WorldWideScience

Sample records for anoxic groundwater sediment

  1. Release of metals from anoxic sediment

    DEFF Research Database (Denmark)

    Larsen, Martin Mørk; Jacobsen, Gitte

    The Bornholm Deep is anoxic every summer, and samples were collected in the fall 2012 and stored dark and cold (4°C in climate room), degassing regularly with Ar(g) to keep the overlying water column anoxic. Nine sediments columns were selected and divided into three groups, (1) where the water w...... without crabs, but cloudy, indicating re-suspension in the group with crabs. The metal release from sediments will be discussed in the context of re-oxygenation of anoxic or low-oxic sediments and the effect of organism that digs into the sediment in recently re-oxidised bottom waters....

  2. Temperature-induced impacts on groundwater quality and arsenic mobility in anoxic aquifer sediments used for both drinking water and shallow geothermal energy production.

    Science.gov (United States)

    Bonte, Matthijs; van Breukelen, Boris M; Stuyfzand, Pieter J

    2013-09-15

    Aquifers used for the production of drinking water are increasingly being used for the generation of shallow geothermal energy. This causes temperature perturbations far beyond the natural variations in aquifers and the effects of these temperature variations on groundwater quality, in particular trace elements, have not been investigated. Here, we report the results of column experiments to assess the impacts of temperature variations (5°C, 11°C, 25°C and 60°C) on groundwater quality in anoxic reactive unconsolidated sandy sediments derived from an aquifer system widely used for drinking water production in the Netherlands. Our results showed that at 5 °C no effects on water quality were observed compared to the reference of 11°C (in situ temperature). At 25°C, As concentrations were significantly increased and at 60 °C, significant increases were observed pH and DOC, P, K, Si, As, Mo, V, B, and F concentrations. These elements should therefore be considered for water quality monitoring programs of shallow geothermal energy projects. No consistent temperature effects were observed on Na, Ca, Mg, Sr, Fe, Mn, Al, Ba, Co, Cu, Ni, Pb, Zn, Eu, Ho, Sb, Sc, Yb, Ga, La, and Th concentrations, all of which were present in the sediment. The temperature-induced chemical effects were probably caused by (incongruent) dissolution of silicate minerals (K and Si), desorption from, and potentially reductive dissolution of, iron oxides (As, B, Mo, V, and possibly P and DOC), and mineralisation of sedimentary organic matter (DOC and P).

  3. H2 cycling and microbial bioenergetics in anoxic sediments

    Science.gov (United States)

    Hoehler, Tori M.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, the great majority of microbial redox processes involve H2 as a reactant, product, or potential by-product, and the thermodynamics of these processes are thus highly sensitive to fluctuations in environmental H2 concentrations. In turn, H2 concentrations are controlled by the activity of H2-consuming microorganisms, which efficiently utilize this substrate down to levels which correspond to their bioenergetic limitations. Consequently, any environmental change which impacts the thermodynamics of H2-consuming organisms is mirrored by a corresponding change in H2 concentrations. This phenomenon is illustrated in anoxic sediments from Cape Lookout Bight, NC, USA: H2 concentrations are controlled by a suite of environmental parameters (e.g., temperature, sulfate concentrations) in a fashion which can be quantitatively described by a simple thermodynamic model. These findings allow us to calculate the apparent minimum quantity of biologically useful energy in situ. We find that sulfate reducing bacteria are not active at energy yields below -18 kJ per mole sulfate, while methanogenic archaea exhibit a minimum close to -10 kJ per mole methane.

  4. Past climate clues from anoxic basin sediments: Cariaco basin (Venezuela) as a tropical climate type section

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, L.C.

    2008-07-01

    This paper discusses how anoxic conditions in deep oceans are the result of a dynamic balance between oxygen supply and oxygen consumption. The author states that a significant consequence of ancient anoxic episodes was that the accumulation and preservation of organic matter in marine sediments were greatly enhanced, allowing the generation of potential petroleum source rocks. Changes in climatic conditions both in the short term as well as over longer periods of time are examined on the basis of oxygen isotope quantities found in ice-cores drilled in Greenland. The influence of these climatic changes on anoxic conditions in the oceans is discussed.

  5. Attenuation and colloidal mobilization of bacteriophages in natural sediments under anoxic as compared to oxic conditions.

    Science.gov (United States)

    Klitzke, Sondra; Schroeder, Jendrik; Selinka, Hans-Christoph; Szewzyk, Regine; Chorus, Ingrid

    2015-06-15

    Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge conditions. Under anoxic conditions, attenuation of bacteriophages was dominated by sorption over inactivation, with MS2 showing a higher degree of sorption than PhiX174. Inactivation in water was low under anoxic conditions for both bacteriophages with about one log10 decrease in concentration during 16 h. Increased Fe/Al concentrations and a low organic carbon content of the sediment led to enhanced bacteriophage removal under anoxic conditions. However, even in the presence of sufficient Fe/A-(hydr)oxides on the solid phase, bacteriophage sorption was low. We presume that organic matter may limit the potential retention of sesquioxides in anoxic sediments and should thus be considered for the risk assessment of virus breakthrough in the subsurface.

  6. The challenge of proving the existence of metazoan life in permanently anoxic deep-sea sediments.

    Science.gov (United States)

    Danovaro, Roberto; Gambi, Cristina; Dell'Anno, Antonio; Corinaldesi, Cinzia; Pusceddu, Antonio; Neves, Ricardo Cardoso; Kristensen, Reinhardt Møbjerg

    2016-06-07

    The demonstration of the existence of metazoan life in absence of free oxygen is one of the most fascinating and difficult challenges in biology. Danovaro et al. (2010) discovered three new species of the Phylum Loricifera, living in the anoxic sediments of the L'Atalante, a deep-hypersaline anoxic basin of the Mediterranean Sea. Multiple and independent analyses based on staining, incorporation of radiolabeled substrates, CellTracker Green incorporation experiments and ultra-structure analyses, allowed Danovaro et al. (2010) to conclude that these animals were able to spend their entire life cycle under anoxic conditions. Bernhard et al. (2015) investigated the same basin. Due to technical difficulties in sampling operations, they could not collect samples from the permanently anoxic sediment, and sampled only the redoxcline portion of the L'Atalante basin. They found ten individuals of Loricifera and provided alternative interpretations of the results of Danovaro et al. (2010). Here we analyze these interpretations, and present additional evidence indicating that the Loricifera encountered in the anoxic basin L'Atalante were actually alive at the time of sampling. We also discuss the reliability of different methodologies and approaches in providing evidence of metazoans living in anoxic conditions, paving the way for future investigations.This paper is a response to Bernhard JM, Morrison CR, Pape E, Beaudoin DJ, Todaro MA, Pachiadaki MG, Kormas KAr, Edgcomb VG. 2015. Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins. BMC Biology 2015 13:105.See research article at http://bmcbiol.biomedcentral.com/articles/10.1186/s12915-015-0213-6.

  7. Sulfur Isotope Exchange between S-35 Labeled Inorganic Sulfur-Compounds in Anoxic Marine-Sediments

    DEFF Research Database (Denmark)

    FOSSING, H.; THODEANDERSEN, S.; JØRGENSEN, BB

    1992-01-01

    Isotope exchange reactions between S-35-labeled sulfur compounds were studied in anoxic estuarine sediment slurries at 21-degrees-C and pH 7.4-7.7. Two experiments labeled with radioactive elemental sulfur (S-35-degrees) and one labeled with radioactive sulfate ((SO42-)-S-35) were performed as time...

  8. Bioremediation of petroleum hydrocarbons in anoxic marine sediments: consequences on the speciation of heavy metals.

    Science.gov (United States)

    Dell'Anno, Antonio; Beolchini, Francesca; Gabellini, Massimo; Rocchetti, Laura; Pusceddu, Antonio; Danovaro, Roberto

    2009-12-01

    We investigated the effects of biostimulation and bioagumentation strategies applied to harbor sediments displaying reducing conditions and high concentrations of petroleum hydrocarbons and heavy metals. We compared the microbial efficiency of hydrocarbon removal from sediments maintained for 60 days in anoxic conditions and inoculated with acetate, sulfate-reducing bacterial strains and acetate and sulfate-reducing bacteria. All treatments determined a significant increase in the microbial growth and significant decreases of hydrocarbon contents and of redox potential values. The addition of sulfate-reducing bacterial strains to the sediment was the most efficient treatment for the hydrocarbon removal. In all experiments, significant changes of the heavy metals' phase repartition were observed. The results reported here suggest that the biodegradation of petroleum hydrocarbons in anoxic marine sediments may be enhanced by stimulating microbial anaerobic metabolism, but care should be applied to monitor the potential changes in the mobility and bioavailability of heavy metals induced by bio-treatments.

  9. Jellyfish Lake, Palau: early diagenesis of organic matter in sediments of an anoxic marine lake

    Science.gov (United States)

    Orem, W.H.; Burnett, W.C.; Landing, W.M.; Lyons, W.B.; Showers, W.

    1991-01-01

    The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10?? lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake. -from Authors

  10. Decomposition of algal lipids in clay-enriched marine sediment under oxic and anoxic conditions

    Institute of Scientific and Technical Information of China (English)

    吕冬伟; 宋茜; 王旭晨

    2010-01-01

    A series of laboratory incubation experiments were conducted to examine the decomposition of algal organic matter in clay-enriched marine sediment under oxic and anoxic conditions.During the 245-day incubation period,changes in the concentrations of TOC,major algal fatty acid components (14:0,16:0,16:1,18:1 and 20:5),and n-alkanes (C16-C23) were quantified in the samples.Our results indicate that the organic matters were degraded more rapidly in oxic than anoxic conditions.Adsorption of fatty acids onto cla...

  11. The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

    OpenAIRE

    Reinhard, Christopher T.; Planavsky, Noah J.; Wang, Xiangli; Fischer, Woodward W.; Johnson, Thomas M.; Lyons, Timothy W.

    2014-01-01

    Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ^(53)Cr data from sediments of the ...

  12. Causes for negative carbon isotope anomalies in Mesozoic marine sediments: Constraints from modern and ancient anoxic settings

    NARCIS (Netherlands)

    van Breugel, Y.

    2006-01-01

    Oceanic Anoxic Events (OAEs) were short periods in Earth history (˜0.5-1 Ma) characterized by atypically high burial rates of organic carbon in marine sediments worldwide. OAEs reflect increased marine primary production and/or enhanced organic matter preservation under anoxic water column condition

  13. Causes for negative carbon isotope anomalies in Mesozoic marine sediments : Constraints from modern and ancient anoxic settings

    NARCIS (Netherlands)

    Breugel, Y. van

    2006-01-01

    Oceanic Anoxic Events (OAEs) were short periods in Earth history (˜0.5-1 Ma) characterized by atypically high burial rates of organic carbon in marine sediments worldwide. OAEs reflect increased marine primary production and/or enhanced organic matter preservation under anoxic water column condition

  14. Investigating phosphorus uptake in anoxic and sulfidic surface sediments with 33P radiotracer experiments

    Science.gov (United States)

    Dijkstra, Nikki; Kraal, Peter; Gonzalez, Santiago; Slomp, Caroline

    2016-04-01

    Phosphorus (P) is a key nutrient for marine organisms. Enhanced P availability in the water column can fuel algal blooms and the development of bottom water anoxia. Recently, it was suggested that micro-organisms in sediments overlain by anoxic and sulfidic bottom waters might take up dissolved P and form Fe(II)-P minerals, thereby enhancing P removal. In this study, we investigated the uptake of P in surface sediments with 33P radiotracer experiments. The sediments were recovered from the anoxic and sulfidic deep basin of the Black Sea and, for comparison, from the adjacent oxic shelf. Results suggest a very fast sedimentary uptake of 33P at all sites but in particular for sediments from the oxic shelf. At all sites, most 33P was sequestered in the citrate-dithionite-bicarbonate-(CDB)-extractable sediment P fraction. No significant differences with abiotic controls were observed, implying that micro-organisms were not directly involved in the P uptake. Whereas 33P uptake by the oxic shelf sediment was likely controlled by sorption of 33P to iron(Fe)-(oxyhydr)oxides, the nature of the CDB-extractable P fraction in the deep basin sediments remains unclear. We discuss whether authigenic formation of Fe(II)-P minerals or fast adsorption of P to calcites may explain our findings.

  15. Are iron-phosphate minerals a sink for phosphorus in anoxic Black Sea sediments?

    Science.gov (United States)

    Dijkstra, Nikki; Kraal, Peter; Kuypers, Marcel M M; Schnetger, Bernhard; Slomp, Caroline P

    2014-01-01

    Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides and release of the associated P. However, recent work suggests that Fe-bound P is an important burial phase in euxinic (i.e. anoxic and sulfidic) basin sediments in the Baltic Sea. In this study, we investigate the role of Fe-bound P as a potential sink for P in Black Sea sediments overlain by oxic and euxinic bottom waters. Sequential P extractions performed on sediments from six multicores along two shelf-to-basin transects provide evidence for the burial of Fe-bound P at all sites, including those in the euxinic deep basin. In the latter sediments, Fe-bound P accounts for more than 20% of the total sedimentary P pool. We suggest that this P is present in the form of reduced Fe-P minerals. We hypothesize that these minerals may be formed as inclusions in sulfur-disproportionating Deltaproteobacteria. Further research is required to elucidate the exact mineral form and formation mechanism of this P burial phase, as well as its role as a sink for P in sulfide-rich marine sediments.

  16. Anoxic carbon degradation in Arctic sediments: Microbial transformations of complex substrates

    DEFF Research Database (Denmark)

    Arnosti, Carol; Finke, Niko; Larsen, Ole

    2005-01-01

    Complex substrates are degraded in anoxic sediments by the concerted activities of diverse microbial communities. To explore the effects of substrate complexity on carbon transformations in permanently cold anoxic sediments, four substrates—Spirulina cells, Isochrysis cells, and soluble high...... of carbon degradation diverged, with an additional 43%, 32%, 33%, and 8% of Isochrysis, Iso-Ex, Spirulina, and Spir-Ex carbon respired to CO2 over the next 750 h of incubation. Somewhat surprisingly, the soluble, carbohydrate-rich extracts did not prove to be more labile substrates than the whole cells from...... which they were derived. Although Spirulina and Iso-Ex differed in physical and chemical characteristics (solid/soluble, C/N ratio, lipid and carbohydrate content), nearly identical quantities of carbon were respired to CO2. In contrast, only 15% of Spir-Ex carbon was respired, despite the initial burst...

  17. Anoxic carbon degradation in Arctic sediments: Microbial transformations of complex substrates

    Science.gov (United States)

    Arnosti, C.; Finke, N.; Larsen, O.; Ghobrial, S.

    2005-05-01

    Complex substrates are degraded in anoxic sediments by the concerted activities of diverse microbial communities. To explore the effects of substrate complexity on carbon transformations in permanently cold anoxic sediments, four substrates— Spirulina cells, Isochrysis cells, and soluble high molecular weight carbohydrate-rich extracts of these cells (Spir-Ex and Iso-Ex)—were added to sediments collected from Svalbard. The sediments were homogenized, incubated anaerobically in gas-tight bags at 0°C, and enzyme activities, fermentation, and terminal respiration were monitored over a 1134 h time course. All substrate additions yielded a fraction (8%-13%) of carbon that was metabolized to CO 2 over the first 384 h of incubation. The timecourse of VFA (volatile fatty acid) production and consumption, as well as the suite of VFAs produced, was similar for all substrates. After this phase, pathways of carbon degradation diverged, with an additional 43%, 32%, 33%, and 8% of Isochrysis, Iso-Ex, Spirulina, and Spir-Ex carbon respired to CO 2 over the next 750 h of incubation. Somewhat surprisingly, the soluble, carbohydrate-rich extracts did not prove to be more labile substrates than the whole cells from which they were derived. Although Spirulina and Iso-Ex differed in physical and chemical characteristics (solid/soluble, C/N ratio, lipid and carbohydrate content), nearly identical quantities of carbon were respired to CO 2. In contrast, only 15% of Spir-Ex carbon was respired, despite the initial burst of activity that it fueled, its soluble nature, and its relatively high (50%) carbohydrate content. The microbial community in these cold anoxic sediments clearly has the capacity to react rapidly to carbon input; extent and timecourse of remineralization of added carbon is similar to observations made at much higher temperatures in temperate sediments. The extent of carbon remineralization from these specific substrates, however, would not likely have been predicted

  18. Long-term performance and fouling analysis of full-scale direct nanofiltration (NF) installations treating anoxic groundwater

    NARCIS (Netherlands)

    Beyer, F.; Rietman, B.M.; Zwijnenburg, A.; Brink, van den P.; Vrouwenvelder, J.S.; Jarzembowska, M.; Laurinonyte, J.; Stams, A.J.M.; Plugge, C.M.

    2014-01-01

    Long-term performance and fouling behavior of four full-scale nanofiltration (NF) plants, treating anoxic groundwater at 80% recovery for drinking water production, were characterized and compared with oxic NF and reverse osmosis systems. Plant operating times varied between 6 and 10 years and pretr

  19. Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation

    Science.gov (United States)

    Bourke, Michael F.; Marriott, Philip J.; Glud, Ronnie N.; Hasler-Sheetal, Harald; Kamalanathan, Manoj; Beardall, John; Greening, Chris; Cook, Perran L. M.

    2017-01-01

    Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H2 production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H2 persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H2 production was observed in dark anoxic cultures of diatoms (Fragilariopsis sp.) and a chlorophyte (Pyramimonas) isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments.

  20. Metal impacts on microbial biomass in the anoxic sediments of a contaminated lake

    Energy Technology Data Exchange (ETDEWEB)

    Gough, Heidi L.; Dahl, Amy L.; Nolan, Melissa A.; Gaillard, Jean-Francois; Stahl, David A.

    2008-04-26

    Little is known about the long-term impacts of metal contamination on the microbiota of anoxic lake sediments. In this study, we examined microbial biomass and metals (arsenic, cadmium, chromium, copper, iron, lead, manganese, and zinc) in the sediments of Lake DePue, a backwater lake located near a former zinc smelter. Sediment core samples were examined using two independent measures for microbial biomass (total microscopic counts and total phospholipid-phosphate concentrations), and for various fractions of each metal (pore water extracts, sequential extractions, and total extracts of all studied metals and zinc speciation by X-ray absorption fine structure (XAFS). Zinc concentrations were up to 1000 times higher than reported for sediments in the adjacent Illinois River, and ranged from 21,400 mg/kg near the source to 1,680 mg/kg near the river. However, solid metal fractions were not well correlated with pore water concentrations, and were not good predictors of biomass concentrations. Instead, biomass, which varied among sites by as much as two-times, was inversely correlated with concentrations of pore water zinc and arsenic as established by multiple linear regression. Monitoring of other parameters known to naturally influence biomass in sediments (e.g., organic carbon concentrations, nitrogen concentrations, pH, sediment texture, and macrophytes) revealed no differences that could explain observed biomass trends. This study provides strong support for control of microbial abundance by pore water metal concentrations in contaminated freshwater sediments.

  1. Uranium(IV) adsorption by natural organic matter in anoxic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Bone, Sharon E.; Dynes, James J.; Cliff, John; Bargar, John R.

    2017-01-09

    Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.

  2. Uranium(IV) adsorption by natural organic matter in anoxic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Bone, Sharon E.; Dynes, James J.; Cliff, John; Bargar, John R.

    2017-01-09

    Uranium is an important fuel source and a global environmental contaminant. It accumulates in the tetravalent state, U(IV), in anoxic sediments, including ore deposits, marine basins, and contaminated aquifers. However, very little is known about the speciation of U(IV) in low temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2) in anoxic sediments; yet studies now show that UO2 is not often dominant in these environments. However, a model of U(IV) speciation under environmentally relevant conditions has not yet been developed. Here we show that complexes of U(IV) adsorb on organic carbon and organic carbon-coated clays in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that the U(IV) product depended on the reduction pathway, our results demonstrate that UO2 formation can be inhibited simply by decreasing the U:solid ratio. Thus, it is the number and type of surface ligands that controls U(IV) speciation subsequent to U(VI) reduction. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider retention of U(IV) ions within the local sediment environment.

  3. Phosphorus, carbon and nitrogen enrichment during sedimentation in a seasonally anoxic lake (Lake Lugano, Switzerland

    Directory of Open Access Journals (Sweden)

    Kurt W. Hanselmann

    2002-08-01

    Full Text Available Sedimentation fluxes of major nutrients are investigated during 1996 and 1997 at three different depths and two locations in eutrophic southern basin of Lake Lugano (Switzerland. Horizontal differences between the two sites are on the order of 10-40% (but can exceed 50%, whereas differences related to interannual oscillations range between 5 and 24%. Particulate organic carbon (POC and nitrogen (PN fluxes show a constant increase of 5-20% from the upper to the bottom trap. This tendency remains more or less constant during the year. On the contrary, particulate phosphorus (PP shows a seasonal variation, with higher accumulation rates from the I to the III trap in autumn and winter which can exceed +1200%. This phenomenon is due to the interaction between the dissolved phosphorus (DP and the iron(oxihydroxides (Fe(OH3 near the oxycline. Fe(OH3 precipitates at the iron redox boundary, scavenging DP. This enrichment flux increases together with the development of the anoxic benthic layer. The efficiency of the iron redox layer in trapping upward diffusing P is related to the concentration of dissolved iron in the anoxic hypolimnion. In Lake Lugano the two considered sites present major difference of iron concentration, and this difference is reflected in the P sedimentation fluxes. The exposition of an additional sedimentation trap above the maximal oxycline height has allowed to gain insight into this phenomenon.

  4. Chromium isotope composition of reducing and anoxic sediments from the Peru Margin and Cariaco Basin

    Science.gov (United States)

    Gueguen, B.; Planavsky, N.; Wang, X.; Algeo, T. J.; Peterson, L. C.; Reinhard, C. T.

    2014-12-01

    Chromium isotope systematics in marine sediments are now being used as a new redox proxy of the modern and ancient Earth's surface. Chromium is primarily delivered to the oceans by riverine inputs through weathering of Cr(III)-rich minerals present in the continental crust and oxidation of insoluble Cr(III) to soluble Cr(VI) species. Since oxidation-reduction reactions fractionate Cr isotopes whereby oxidized Cr(VI) species are preferentially enriched in heavy Cr isotopes, the Cr isotope composition of marine sediments may be useful tracers of redox conditions at the Earth's surface through geological time. Chromium is quantitatively removed in organic-rich sediments where reducing conditions prevail and promote reduction of Cr(VI) to Cr(III), and thus, these sediments should capture the ambient seawater Cr isotope composition. However, the isotopic composition of modern organic-rich sediments is poorly documented so far, and this step is essential for further modeling the global oceanic Cr isotope mass balance and assessing the effects of sedimentation and post-depositional processes on the marine Cr isotopes archive. In this study, we have characterized modern marine organic-rich sediments for their Cr isotope composition (δ53/52Cr) from two different settings, the Peru margin upwelling zone and the anoxic Cariaco Basin (Venezuela). Chromium isotopes were measured on a MC-ICP-MS (Nu Plasma) using a double-spike correction method. The authigenic fraction of shallow samples from the Peru margin sedimentary sequence with a high Total Organic Carbon (TOC) content (>10 wt%) yield an average δ53/52Crauthigenic value of +0.67 ±0.05 ‰ (2sd). However, although this value is close to the seawater value (Atlantic Ocean) and to Cariaco basin sediments (~ +0.6 ‰), reducing sediments from the Peru margin are on average isotopically slightly heavier, especially in samples having a low authigenic fraction and a low TOC content (δ53/52Crauthigenic values up to +1.30

  5. Uranium and plutonium in anoxic marine sediments of the Santiago River mouth (Eastern Pacific, Mexico).

    Science.gov (United States)

    Almazán-Torres, María Guadalupe; Ordóñez-Regil, Eduardo; Ruiz-Fernández, Ana Carolina

    2016-11-01

    The uranium (U) and plutonium (Pu) content with depth in a sediment core collected in the continental shelf off the mouth of the Santiago River in the Mexican Pacific was studied to evaluate the contamination effects of the effluent of the Santiago-Lerma River as it moves into the sea. The large mass of terrestrial detritus delivered by the river influences the physicochemical and geochemical processes in the seafloor. Abnormal concentrations of U and Pu in sediments were examined as indicative of the effects of anoxic conditions. One of the indicators of pollution of seawater is the bacterial activity of the shallow seabed layer; and among the prevailing bacteria, the magnetotactic ones induce the formation of euhedral and framboidal shapes (pyrite). These pyrite entities are by-products of anoxic environments loaded with decomposing detrital material and are very abundant in the surface layers of the sediment core analyzed. The pyrite formation is the result of a biochemical reaction between iron and organic sulphur reduced by bacteria, and the pyrite entities precipitate to the seafloor. In the same upper zone of the profile, (238)U is readily immobilized, while (234)U is oxidized and dissolved in seawater by the effect of hot atom chemistry. This may cause the activity ratio (AR) (234)U/(238)U disequilibrium (near 0.41). Furthermore, in the shallow layer of the sediment core, an abnormally high concentration of (239+240)Pu was detected. In this upper layer, the activity concentrations found were 3.19 Bq kg(-1) for (238)U, 1.32 kg(-1) for (234)U and 2.78 Bq kg(-1) for (239+240)Pu. In the lower fractions of the sediment core, normal values of AR (234)U/(238)U (≈1) were found, with traces of (239+240)Pu.

  6. Experimental study of Ni solubility in sulphidic groundwater and cement water under anoxic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, T.; Vuorinen, U.; Kekki, T.; Aalto, H. [VTT Chemical Technology, Espoo (Finland)

    2001-06-01

    The nickel solubility was studied during a 177-day period under anoxic conditions in three types of waters: a synthetic reference groundwater (OL-SR), a natural Olkiluoto groundwater (PVA2), and a cement-conditioned groundwater (C-PVA2). To each water, nickel, ferrous iron and sulphide were added yielding eight combinations of, approximately, the following initial concentrations: nickel: 1.0x10{sup -6} and 1.0x10{sup -3} mol/L, ferrous iron: 1.8 10{sup -6} and 1.8x10{sup -5} mol/L, and sulphide: 3.1x10{sup -6} and 9.4x10{sup -5} mol/L. The concentrations of these elements in the natural groundwater PVA2 as well as in the cement-conditioned water C-PVA2 was insignificant. In the synthetic water, the nickel concentration was unchanged in all samples having a high initial nickel concentration of 1.0x10{sup -3} mol/L. In the samples with an initial low nickel concentration of 1.0x10{sup -6} mol/L, the sulphide content determined the final nickel concentration. Where the initial sulphide concentration was low, the nickel concentration remained at the level of 1.0x10{sup -6} mol/L, but the higher sulphide concentration caused the nickel concentration to drop to below 10{sup -8} mol/L. In the natural groundwater PVA2, the nickel concentration dropped to below 10{sup -4} mol/L in all samples with an initially high nickel concentration, and to values of roughly 10{sup -7} mol/L in samples with an initially low nickel content. In the cement-conditioned water, the nickel concentration reached a value of 3x10{sup -6} mol/L in samples with initial high nickel concentrations, and to a value of 1x10{sup -7} mol/L in samples with a low initial nickel content. The added amounts of iron and sulphide did not have any significant effect on the observed nickel solubility. The solid phases formed in the natural and synthetic groundwater were analyzed by XRD but could not be identified. In the case of cement-conditioned water the XRD analyses showed the presence of Ni(OH){sub 2} as well

  7. Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation

    DEFF Research Database (Denmark)

    Bourke, Michael F.; Marriott, Philip J; Glud, Ronnie N.

    2017-01-01

    . Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H......Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to prokaryotes such as bacteria and archaea....../hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae...

  8. Electricity generation by anaerobic bacteria and anoxic sediments from hypersaline soda lakes

    Science.gov (United States)

    Miller, L.G.; Oremland, R.S.

    2008-01-01

    Anaerobic bacteria and anoxic sediments from soda lakes produced electricity in microbial fuel cells (MFCs). No electricity was generated in the absence of bacterial metabolism. Arsenate respiring bacteria isolated from moderately hypersaline Mono Lake (Bacillus selenitireducens), and salt-saturated Searles Lake, CA (strain SLAS-1) oxidized lactate using arsenate as the electron acceptor. However, these cultures grew equally well without added arsenate using the MFC anode as their electron acceptor, and in the process oxidized lactate more efficiently. The decrease in electricity generation by consumption of added alternative electron acceptors (i.e. arsenate) which competed with the anode for available electrons proved to be a useful indicator of microbial activity and hence life in the fuel cells. Shaken sediment slurries from these two lakes also generated electricity, with or without added lactate. Hydrogen added to sediment slurries was consumed but did not stimulate electricity production. Finally, electricity was generated in statically incubated "intact" sediment cores from these lakes. More power was produced in sediment from Mono Lake than from Searles Lake, however microbial fuel cells could detect low levels of metabolism operating under moderate and extreme conditions of salt stress. ?? 2008 US Government.

  9. Recycling and burial of phosphorus in sediments of an anoxic fjord-the By Fjord, western Sweden

    DEFF Research Database (Denmark)

    Viktorsson, Lena; Kononets, Mikhail; Roos, Per;

    2013-01-01

    the DIC and DIP fluxes at oxic bottoms was almost 10 times higher than the Redfield C: P ratio indicating partial immobilization of P in oxic sediments. In contrast, the C: P ratio in fluxes was on average 1.5 times lower than Redfield at the anoxic bottoms. The benthic fluxes from anoxic bottoms were P...... rich not only in relation to C, but also to N. The low C: P flux ratio at anoxic sites coincided with an about 2.5 times higher than Redfield C: P ratio of organic matter in the sediment solid phase clearly suggesting preferential regeneration of P at anoxic bottoms. Burial of inorganic P was higher...... water. The water in the basin is exchanged only every 3 to 5 years and the water below sill level is anoxic or sulfidic between water renewals. Five sites were examined in the By Fjord; three shallow sites above the sill level with oxic bottom waters and two deeper sites with anoxic bottom waters...

  10. Investigation of Eh, pH and corrosion potential of steel in anoxic groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Peat, R.; Brabon, S.; Fennell, P.A.H.; Rance, A.P.; Smart, N.R. [AEA Technology (United Kingdom)

    2001-01-01

    SKB intend to dispose of the spent nuclear fuel produced by Sweden's eleven nuclear reactors by encapsulating it in corrosion-resistant copper canisters containing a cast iron or carbon steel insert. After encapsulation, the fuel will be transported to a geological repository, where the containers will be deposited at a depth of 500 to 700 m in granitic rock and surrounded by a bentonite clay backfill material. If, or when the copper corrosion shield fails, the iron insert will be in contact with oxygen-free water and hydrogen-producing, anaerobic corrosion will start. SKB have carried out modelling calculations of the oxidising power (Eh) of groundwater and wished to confirm the results by carrying out experimental measurements. The objective of the work described in this report was to demonstrate the feasibility of monitoring Eh, pH and corrosion potential in a cell where anaerobic corrosion of steel in artificial groundwater was occurring. To this end, gas cells similar to those used previously for anaerobic corrosion rate measurements were used as the basis for the design of an electrochemical cell. The cell incorporated electrodes to provide an in situ measurement of the redox potential, Eh, the pH and the corrosion potential of carbon steel. The main stages of the work were: Design of the electrochemical cell; Preparation of silver-silver chloride and calomel reference electrodes; Calibration of the reference electrodes and commercial glass pH electrodes against a standard hydrogen electrode; Assembly of the test cell under anoxic conditions; Monitoring the cell before and after the addition of steel wires to the test solution. Details of the design of the test cell and the experimental procedures used are described. Two cells were set up. The first employed a silver-silver chloride reference electrode, which was failed after approximately 400 hours, and the second cell therefore used a calomel reference electrode. The results of the electrode

  11. Long-term performance and fouling analysis of full-scale direct nanofiltration (NF) installations treating anoxic groundwater

    KAUST Repository

    Beyer, Florian

    2014-10-01

    Long-term performance and fouling behavior of four full-scale nanofiltration (NF) plants, treating anoxic groundwater at 80% recovery for drinking water production, were characterized and compared with oxic NF and reverse osmosis systems. Plant operating times varied between 6 and 10 years and pretreatment was limited to 10μm pore size cartridge filtration and antiscalant dosage (2-2.5mgL-1) only. Membrane performance parameters normalized pressure drop (NPD), normalized specific water permeability (Kw) and salt retention generally were found stable over extended periods of operation (>6 months). Standard acid-base cleanings (once per year or less) were found to be sufficient to maintain satisfying operation during direct NF of the described iron rich (≤8.4mgL-1) anoxic groundwaters. Extensive autopsies of eight NF membrane elements, which had been in service since the plant startup (6-10 years), were performed to characterize and quantify the material accumulated in the membrane elements. Investigations using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), total organic carbon (TOC) and adenosine triphosphate (ATP) measurements revealed a complex mixture of organic, biological and inorganic materials. The fouling layers that developed during half to one year of operation without chemical cleaning were very thin (<2. μm). Most bio(organic) accumulates were found in the lead elements of the installations while inorganic precipitates/deposits (aluminosilicates and iron(II)sulfides) were found in all autopsied membrane elements. The high solubility of reduced metal ions and the very slow biofilm development under anoxic conditions prevented rapid fouling during direct NF of the studied groundwaters. When compared to oxic NF and RO systems in general (e.g. aerated ground waters or surface waters), the operation and performance of the described anoxic installations (with minimal pretreatment) can be described as very stable. © 2014

  12. Effect of resuspension on the release of heavy metals and water chemistry in anoxic and oxic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Kyung-Yup; Kim, Hong-Seok; Hwang, Inseong [School of Civil and Environmental Engineering, Pusan National University, Busan (Korea, Republic of)

    2011-10-15

    Two types of river sediments with contrasting characteristics (anoxic or oxic) were resuspended and the release of heavy metals and changes in water chemistry were investigated. During resuspension of the anoxic sediment, the dissolved oxygen (DO) concentration and redox potential of the water layer decreased abruptly within the first 1 min, followed by increases toward the end of the resuspension period. Heavy metals were released rapidly in the first 6 h, probably due to the oxidation of acid volatile sulfide (AVS) of the anoxic sediment, and then the aqueous phase concentrations of the heavy metals decreased due to resorption onto the sediment until the 12-h point. During resuspension of the oxic sediment, the DO concentration and redox potential remained relatively constant in the oxic ranges. The heavy metals were released from the oxic sediment gradually during a 24-h resuspension period. The temporal maximum concentrations of Ni, Cu, Zn, and Cd in the aqueous phases in both experiments frequently exceeded the USEPA water quality criteria or the water quality guidelines of Australia and New Zealand. This suggests that a resuspension event could bring about temporal water quality deterioration in the two sediment environments. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

    Science.gov (United States)

    Reinhard, Christopher T.; Planavsky, Noah J.; Wang, Xiangli; Fischer, Woodward W.; Johnson, Thomas M.; Lyons, Timothy W.

    2014-12-01

    Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ53Cr data from sediments of the Cariaco Basin, Venezuela-a 'type' environment for large, perennially anoxic basins with a relatively strong hydrological connection to the global oceans. We document a marked positive shift in bulk δ53Cr values following the termination of the Last Glacial Maximum, followed by relative stasis. Based on a suite of independent redox proxies, this transition marks a switch from oxic to persistently anoxic and sulfidic (euxinic) depositional conditions within the basin. We find good agreement between two independent approaches toward estimating the δ53Cr composition of authigenic Cr in euxinic Cariaco Basin sediments and that these estimates are very similar to the δ53Cr composition of modern open Atlantic Ocean seawater. These data, together with considerations of reaction kinetics and mass balance within the Cariaco Basin, are consistent with the hypothesis that anoxic marine settings can serve as a chemical archive of first-order trends in seawater δ53Cr composition. Additionally, the Cariaco Basin data suggest that there has been secular stability in the average δ53Cr value of Atlantic seawater over the last ∼15 kyr.

  14. A comparison of an optimised sequential extraction procedure and dilute acid leaching of elements in anoxic sediments, including the effects of oxidation on sediment metal partitioning.

    Science.gov (United States)

    Larner, Bronwyn L; Palmer, Anne S; Seen, Andrew J; Townsend, Ashley T

    2008-02-11

    The effect of oxidation of anoxic sediment upon the extraction of 13 elements (Cd, Sn, Sb, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) using the optimised Community Bureau of Reference of the European Commission (BCR) sequential extraction procedure and a dilute acid partial extraction procedure (4h, 1 molL(-1) HCl) was investigated. Elements commonly associated with the sulfidic phase, Cd, Cu, Pb, Zn and Fe exhibited the most significant changes under the BCR sequential extraction procedure. Cd, Cu, Zn, and to a lesser extent Pb, were redistributed into the weak acid extractable fraction upon oxidation of the anoxic sediment and Fe was redistributed into the reducible fraction as expected, but an increase was also observed in the residual Fe. For the HCl partial extraction, sediments with moderate acid volatile sulfide (AVS) levels (1-100 micromolg(-1)) showed no significant difference in element partitioning following oxidation, whilst sediments containing high AVS levels (>100 micromolg(-1)) were significantly different with elevated concentrations of Cu and Sn noted in the partial extract following oxidation of the sediment. Comparison of the labile metals released using the BCR sequential extraction procedure (SigmaSteps 1-3) to labile metals extracted using the dilute HCl partial extraction showed that no method was consistently more aggressive than the other, with the HCl partial extraction extracting more Sn and Sb from the anoxic sediment than the BCR procedure, whilst the BCR procedure extracted more Cr, Co, Cu and As than the HCl extraction.

  15. Jellyfish Lake, Palau: Regeneration of C, N, Si, and P in anoxic marine lake sediments

    Science.gov (United States)

    Lyons, W.B.; Lent, R.M.; Burnett, W.C.; Chin, P.; Landing, W.M.; Orem, W.H.; McArthur, J.M.

    1996-01-01

    Sediment cores from Jellyfish Lake were processed under an inert atmosphere and the pore waters extracted and analyzed for the following parameters: pH, titration alkalinity (TA), Cl-, H4SiO4, PO43-, NH4+, Ca2-, Mg2+, SO42-, and H2S. Additionally, in one set of pore-water samples (core 10), the ??13C of the ??CO2 was also determined. The TA, H4SiO4, PO43-, NH4+, and H2S increased with depth in the pore waters above anoxic bottom-water values. H2S values increased to 3.8 ??M. In one case, both H4SiO4 and PO43- concentrations increased to a maximum value and then decreased with depth, suggesting removal into solid phases. The H4SiO4 concentrations are equal to or greater than pore-water values observed in sediments underlying upwelling areas. PO43- concentrations are, in general, lower than pore-water values from terrigenous nearshore areas but higher than nearshore carbonate pore-water values from Florida Bay or Bermuda. The Ca2+, Cl-, and Mg2+: Cl- ratios show slight decreases in the top 15-20 cm, suggesting that authigenic carbonate may be forming. This suggestion is supported by the fact that the pore waters are saturated with respect to CaCO3 due to the very high TAs. The ??13C measurements of the pore-water ??CO2 are from a shorter core. These measurements reach their most negative concentration at 72 cm and then become slightly heavier. This change is accompanied by a decrease in TA, suggesting the onset of methanogenesis at this location in this core.

  16. Effects of prokaryotic diversity changes on hydrocarbon degradation rates and metal partitioning during bioremediation of contaminated anoxic marine sediments.

    Science.gov (United States)

    Rocchetti, Laura; Beolchini, Francesca; Hallberg, Kevin B; Johnson, D Barrie; Dell'Anno, Antonio

    2012-08-01

    We investigated changes of prokaryotic diversity during bioremediation experiments carried out on anoxic marine sediments characterized by high hydrocarbon and metal content. Microcosms containing contaminated sediments were amended with lactose and acetate and incubated in anaerobic conditions up to 60 d at 20 or 35 °C. Microcosms displaying higher degradation efficiency of hydrocarbons were characterized by the dominance of Alphaproteobacteria and Methanosarcinales and the lack of gene sequences belonging to known hydrocarbonoclastic bacteria. Multivariate analyses support the hypothesis that Alphaproteobacteria are important for hydrocarbon degradation and highlight a potential synergistic effect of archaea and bacteria in changes of metal partitioning. Overall, these results point out that the identification of changes in the prokaryotic diversity during bioremediation of contaminated marine sediments is not only important for the improvement of bio-treatment performance towards hydrocarbons, but also for a better comprehension of changes occurring in metal partitioning which affect their mobility and toxicity.

  17. Groundwater arsenic concentrations in Vietnam controlled by sediment age

    DEFF Research Database (Denmark)

    Postma, Dieke; Larsen, Flemming; Thai, Nguyen Thi

    2012-01-01

    Arsenic contamination of groundwater continues to threaten the health of millions of people in southeast Asia. The oxidation of organic carbon, coupled to the reductive dissolution of arsenic-bearing iron oxides, is thought to control the release of sediment-bound arsenic into groundwater. However......, the cause of the high spatial variability in groundwater arsenic concentrations—which can range from 5 to 500 μg l−1 within distances of a few kilometres—has been uncertain. Here, we combine measurements of sediment age, organic-matter reactivity and water chemistry at four locations along a cross......-section of the arsenic-contaminated Red River floodplain in Vietnam to determine the origin of variations in groundwater arsenic concentrations. The burial age of the aquifer sediments, determined using optical stimulated luminescence, ranged from 460 years near the course of the present-day river to 5,900 years...

  18. Efficacy of Biostimulation for Uranium Sequestration: Coupled Effects Sediment/Groundwater Geochemistry and Microbiology

    Science.gov (United States)

    Xu, J.; Veeramani, H.; Qafoku, N. P.; Singh, G.; Pruden, A.; Kukkadapu, R. K.; Hochella, M. F., Jr.

    2015-12-01

    A systematic flow-through column study was conducted using sediments and groundwater from the subsurface at the U.S. Department of Energy's Integrated Field Research Challenge (IFRC) site in Rifle, Colorado, to better understand the efficacy of uranium removal from the groundwater with and without biostimulation in the form of acetate amendments. The interactive effects of acetate amendment, groundwater/sediment geochemistry, and intrinsic bacterial community composition were evaluated using four types of sediments, collected from different uranium-contaminated (D08, LQ107, CD) or non-contaminated (RABS) aquifers. Subtle variations in the sediments' geochemistry in terms of mineral compositions, particle sizes, redox conditions, and metal(loid) co-contaminants had a marked effect on the uranium removal efficiency, following a descending trend of D08 (~ 90 to 95%) >> RABS (~ 20 to 25) ≥ LQ107 (~ 15 to 20%) > CD (~ -10 to 0%). Overall, biostimulation of the sediments with acetate drove deeper anoxic conditions and observable shifts in bacterial population structures. The abundance of dissimilatory sulfate-reduction genes (i.e., drsA), markers of sulfate-reducing bacteria, were highest in the sediments that performed best in terms of uranium removal. By comparison, no obvious associations were found between the uranium removal efficiency and the abundance of typical iron-reducing microorganisms, e.g., Geobacter spp. In the sediments where bacterial biomass was relatively low and sulfate-reduction was not detected (i.e., CD), abiotic adsorption onto fine mineral surfaces such as phyllosilates likely played a dominant role in the attenuation of aqueous uranium. In these scenarios, however, acetate amendment induced significant remobilization of the sequestered uranium and other heavy metals (e.g., strontium), leading to zero or negative uranium removal efficiencies (i.e., CD). The results of this study suggest that reductive immobilization of uranium can be

  19. Field and laboratory studies of methane oxidation in an anoxic marine sediment: Evidence for a methanogen-sulfate reducer consortium

    Science.gov (United States)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S.

    1994-12-01

    Field and laboratory studies of anoxic sediments from Cape Lookout Bight, North Carolina, suggest that anaerobic methane oxidation is mediated by a consortium of methanogenic and sulfate-reducing bacteria. A seasonal survey of methane oxidation and CO2 reduction rates indicates that methane production was confined to sulfate-depleted sediments at all times of year, while methane oxidation occurred in two modes. In the summer, methane oxidation was confined to sulfate-depleted sediments and occurred at rates lower than those of CO2 reduction. In the winter, net methane oxidation occurred in an interval at the base of the sulfate-containing zone. Sediment incubation experiments suggest both methanogens and sulfate reducers were responsible for the observed methane oxidation. In one incubation experiment both modes of oxidation were partially inhibited by 2-bromoethanesulfonic acid (a specific inhibitor of methanogens). This evidence, along with the apparent confinement of methane oxidation to sulfate-depleted sediments in the summer, indicates that methanogenic bacteria are involved in methane oxidation. In a second incubation experiment, net methane oxidation was induced by adding sulfate to homogenized methanogenic sediments, suggesting that sulfate reducers also play a role in the process. We hypothesize that methanogens oxidize methane and produce hydrogen via a reversal of CO2 reduction. The hydrogen is efficiently removed and maintained at low concentrations by sulfate reducers. Pore water H2 concentrations in the sediment incubation experiments (while net methane oxidation was occurring) were low enough that methanogenic bacteria could derive sufficient energy for growth from the oxidation of methane. The methanogen-sulfate reducer consortium is consistent not only with the results of this study, but may also be a feasible mechanism for previously documented anaerobic methane oxidation in both freshwater and marine environments.

  20. PO4 release at the sediment surface under anoxic conditions: a contribution to the eutrophication of the Baltic Sea?

    Directory of Open Access Journals (Sweden)

    Bernd Schneider

    2011-05-01

    Full Text Available The vertical profiles of phosphate, total CO2 and oxygen/hydrogen sulphide were determined in the deep water of the Gotland Sea during March 2003 to July 2006 with a temporal resolution of 2-3 months. This time span included the shift from anoxic to oxic conditions resulting from a water renewal event, as well as the transition back to anoxic waters during the subsequent two-year stagnation period. The data from depths below 150 m were used to identify and quantify phosphate release and removal processes. The relationship between the total CO2 generated by mineralization (CT, min and the PO4 concentrations indicated that the initial decrease in the phosphate concentrations after the inflow of oxygen-rich water was mainly a dilution effect. Only about one third of the PO4 removal was a consequence of the precipitation of insoluble iron-3-hydroxo-phosphates (Fe-P, which occurred slowly at the sediment surface under oxic conditions. From the CT, min/PO4 ratios it was also concluded that the formation of Fe-P was reversed during the later phase of the stagnation, when the redoxcline approached a depth of 150 m. A phosphate mass balance was performed for four deep water sub-layers in order to quantify the dissolution of Fe-P during the stagnation period and thus to estimate the amount of Fe-P deposited during the last inflow of oxygen-rich water. A value of about 50 mmol-P m-2 was found, which refers to the specific biogeochemical conditions during the change from anoxic to oxic conditions that preceded the stagnation period.

  1. Anoxic incubation of sediment in gas-tight plastic bags: a method for biogeochemical process studies

    DEFF Research Database (Denmark)

    Hansen, JW; Thamdrup, B.; Jørgensen, BB

    2000-01-01

    Incubation of sediment in gas-tight plastic bags is described as a method for experimental studies of biogeochemical processes. Sediment incubation in these bags allows time-course experiments to be conducted on homogenised sediment without dilution, continuous stirring, or gaseous head......-space. Consequently, bag incubations of sediment combine the advantage of low heterogeneity in slurry incubations with the more natural conditions in jar and whole-core incubations. The bag material is a transparent laminated plastic comprised of Nylon, ethylenevinyl alcohol, and polyethylene with a low permeability...... for the studied gases: O-2, CO2, H2S, CH4, N-2, H-2, and He. Estimated fluxes of biologically active gases through the plastic bag during sediment incubation were insignificant compared to rates of microbial processes and to gas concentrations in coastal sediments. An exception was CH4, for which process...

  2. Dynamics of nitrification and denitrification in root- oxygenated sediments and adaptation of ammonia-oxidizing bacteria to low-oxygen or anoxic habitats

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Libochant, J.A.; Blom, C.W.P.M.; Laanbroek, H.J.

    1996-01-01

    Oxygen-releasing plants may provide aerobic niches in anoxic sediments and soils for ammonia-oxidizing bacteria, The oxygen- releasing, aerenchymatous emergent macrophyte Glycerin maxima had a strong positive effect on numbers and activities of the nitrifying bacteria in its root zone in spring and

  3. Vivianite is a key sink for phosphorus in sediments of the Landsort Deep, an intermittently anoxic deep basin in the Baltic Sea

    NARCIS (Netherlands)

    Dijkstra, N.; Slomp, C.P.; Behrends, T.

    2016-01-01

    Phosphorus (P) is an essential nutrient for marine organisms. Its burial in hypoxic and anoxic marine basins is still incompletely understood. Recent studies suggest that P can be sequestered in sediments of such basins as reduced iron (Fe)-P but the exact phase and the underlying mechanisms that le

  4. Long-term survival of dinoflagellate cysts in anoxic marine sediments

    DEFF Research Database (Denmark)

    Ellegaard, Marianne; Lundholm, Nina; Ribeiro, Sofia;

    Germination results of individually isolated dinoflagellate cysts from dated sediment cores obtained in Koljö Fjord on the west coast of Sweden will be presented. More than 500 cysts were isolated, mainly of the species Lingulodinium polyedrum, Pentapharsodinium dalei and Scrippsiella trochoidea......-core as well as effects of storage and isolation conditions on germination success and DNA preservation. Quantitative data on densities of viable dinoflagellates and diatoms in the historical sediment layers will be discussed....

  5. Apparent Minimum Free Energy Requirements for Methanogenic Archaea and Sulfate-Reducing Bacteria in an Anoxic Marine Sediment

    Science.gov (United States)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S.; DeVincenzi, Don (Technical Monitor)

    2000-01-01

    Among the most fundamental constraints governing the distribution of microorganisms in the environment is the availability of chemical energy at biologically useful levels. To assess the minimum free energy yield that can support microbial metabolism in situ, we examined the thermodynamics of H2-consuming processes in anoxic sediments from Cape Lookout Bight, NC, USA. Depth distributions of H2 partial pressure, along with a suite of relevant concentration data, were determined in sediment cores collected in November (at 14.5 C) and August (at 27 C) and used to calculate free energy yields for methanogenesis and sulfate reduction. At both times of year, and for both processes, free energy yields gradually decreased (became less negative) with depth before reaching an apparent asymptote. Sulfate reducing bacteria exhibited an asymptote of -19.1 +/- 1.7 kj(mol SO4(2-)(sup -1) while methanogenic archaea were apparently supported by energy yields as small as -10.6 +/- 0.7 kj(mol CH4)(sup -1).

  6. Long-term survival of dinoflagellate cysts in anoxic marine sediments

    DEFF Research Database (Denmark)

    Ellegaard, Marianne; Lundholm, Nina; Ribeiro, Sofia

    Germination results of individually isolated dinoflagellate cysts from dated sediment cores obtained in Koljö Fjord on the west coast of Sweden will be presented. More than 500 cysts were isolated, mainly of the species Lingulodinium polyedrum, Pentapharsodinium dalei and Scrippsiella trochoidea.......-core as well as effects of storage and isolation conditions on germination success and DNA preservation. Quantitative data on densities of viable dinoflagellates and diatoms in the historical sediment layers will be discussed.......Germination results of individually isolated dinoflagellate cysts from dated sediment cores obtained in Koljö Fjord on the west coast of Sweden will be presented. More than 500 cysts were isolated, mainly of the species Lingulodinium polyedrum, Pentapharsodinium dalei and Scrippsiella trochoidea...

  7. High arsenic (As concentrations in the shallow groundwaters of southern Louisiana: Evidence of microbial controls on As mobilization from sediments

    Directory of Open Access Journals (Sweden)

    Ningfang Yang

    2016-03-01

    New hydrological insights for the region: Shallow groundwaters in southern Louisiana have been reported to contain elevated As concentrations, whereas mechanisms responsible for As release from sediments have rarely been studied in this region. Microbial respiration is generally considered the main mechanism controlling As release in reducing anoxic aquifers such as the shallow aquifers in southern Louisiana and those of the Bengal basin. This study investigates the role microbial respiration plays in As release from shallow aquifer sediments in southern Louisiana through sediment incubation experiments and porewater analysis. Arsenic concentrations were the lowest in the sterilized control experiments, slightly higher in the un-amended experiments, and the highest in the experiments amended with acetate, and especially those amended with both acetate and AQDS (9,10-anthraquinone-2,6-disulfonic acid. Although Fe and Mn generally decreased at the beginning of all the experiments, they did follow a similar trend to As after the decrease. Porewater analysis showed that As and Fe concentrations were generally positively correlated and were higher in the coarse-grained sediments than in the fine-grained sediments. Results of the investigation are consistent with microbial respiration playing a key role in As release from the shallow aquifers sediments in southern Louisiana.

  8. Groundwater recharge measurements in gravel sandy sediments with monolith lysimeter

    Science.gov (United States)

    Bracic Zeleznik, Branka; Souvent, Petra; Cencur Curk, Barbara; Zupanc, Vesna

    2013-04-01

    Ljubljana field aquifer is recharging through precipitation and the river Sava, which has the snow-rain flow regime. The sediments of the aquifer have high permeability and create fast flow as well as high regeneration of the dynamic reserves of the Ljubljana field groundwater resource. Groundwater recharge is vulnerable to climate change and it is very important for drinking water supply management. Water stored in the soil and less permeable layers is important for water availability under extreme weather conditions. Measurements of water percolation through the vadose zone provide important input for groundwater recharge assessment and estimation of contaminant migration from land surface to the groundwater. Knowledge of the processes governing groundwater recharge in the vadose zone is critical to understanding the overall hydrological cycle and quantifying the links between land uses and groundwater quantity and quality. To improve the knowledge on water balance for Ljubljana field aquifer we establish a lysimeter for measurements of processes in unsaturated zone in well field Kleče. The type of lysimeter is a scientific lysimeter designed to solve the water balance equation by measuring the mass of the lysimeter monolith as well as that of outflow tank with high accuracy and high temporal resolution. We evaluated short period data, however the chosen month demonstrates weather extremes of the local climate - relatively dry periods, followed by high precipitation amount. In time of high water usage of vegetation only subsequent substantial precipitation events directly results in water flow towards lower layers. At the same time, gravely layers of the deeper parts of the unsaturated zone have little or no capacity for water retention, and in the event that water line leaves top soil, water flow moves downwards fairly quickly. On one hand this confirms high recharge capacity of Ljubljana field aquifer from precipitation on green areas; on the other hand it

  9. Acetate consumption in anoxic marine sediments: Identification of key players using mixed pure cultures and sediment incubations

    DEFF Research Database (Denmark)

    Na, Hyunsoo

    the flexibility of the microbial communities in response to different geochemical conditions, in high resolution, with biological replicates, using Ion Torrent sequencing. Secondly, we used two different sediment incubation techniques, dialysis tube batch and continuous flow-through bioreactors, to identify...... sulfate for a year were comparable to those of sediment incubated with high sulfate, on phylum/class levels, but within Deltaproteobacteria, certain sulfate reducers such as Desulfobacterium anilini was found only with low sulfate. In continuous flow-through reactors, bacteria mainly involved in sulfur...... at 10 mM acetate-2 mM (low) sulfate and lower (0.1 and 1 mM) acetate-high sulfate conditions, as revealed by Ion Torrent sequencing of 16S rRNA gene sequences. At 0.1 and 1 mM acetate concentrations, members of the phyla Firmicutes (Fusibacter-related), Fusobacteria, and Bacteroidetes were predominantly...

  10. Microbial Oxidation of Pyrite Coupled to Nitrate Reduction in Anoxic Groundwater Sediment

    DEFF Research Database (Denmark)

    Jørgensen, Christian Juncher; Elberling, Bo; Jacobsen, Ole Stig;

    2009-01-01

    denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can...

  11. Effects of water-sediment interaction and irrigation practices on iodine enrichment in shallow groundwater

    Science.gov (United States)

    Li, Junxia; Wang, Yanxin; Xie, Xianjun; DePaolo, Donald J.

    2016-12-01

    High iodine concentrations in groundwater have caused serious health problems to the local residents in the Datong basin, northern China. To determine the impact of water-sediment interaction and irrigation practices on iodine mobilization in aquifers, isotope (2H, 18O and 87Sr/86Sr) and hydrogeochemical studies were conducted. The results show that groundwater iodine concentrations vary from 14.4 to 2180 μg/L, and high iodine groundwater (>150 μg/L) mainly occurs in the central area of the Datong basin. Sediment iodine content is between organic matter acts as the main source of groundwater iodine. The 87Sr/86Sr values and groundwater chemistry suggest that aluminosilicate hydrolysis is the dominant process controlling hydrochemical evolution along groundwater flowpath, and the degradation of TOC/iodine-rich sediment mediated by microbes potentially triggers the iodine release from the sediment into groundwater in the discharge area. The vertical stratification of groundwater 18O and 2H isotope reflects the occurrence of a vertical mixing process driven by periodic surface irrigation. The vertical mixing could change the redox potential of shallow groundwater from sub-reducing to oxidizing condition, thereby affecting the iodine mobilization in shallow groundwater. It is postulated that the extra introduction of organic matter and O2/NO3/SO4 could accelerate the microbial activity due to the supplement of high ranking electron acceptors and promote the iodine release from the sediment into shallow groundwater.

  12. Solid partitioning and solid-liquid distribution of {sup 210}Po and {sup 210}Pb in marine anoxic sediments: roads of Cherbourg at the northwestern France

    Energy Technology Data Exchange (ETDEWEB)

    Connan, O. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)], E-mail: olivier.connan@irsn.fr; Boust, D. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France); Billon, G. [Laboratoire de Chimie Analytique et Marine, Universite des sciences et technologies de Lille, 59655 Villeneuve d' Ascq Cedex (France); Solier, L.; Rozet, M.; Bouderbala, S. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)

    2009-10-15

    A sequential extraction protocol has been used to determine the solid-phase partition of {sup 210}Po and {sup 210}Pb in anoxic marine sediment from the roads of Cherbourg (France) in the central English Channel. Measurements were also obtained in pore waters, in which {sup 210}Po activities range between 1 and 20 mBq L{sup -1} and {sup 210}Pb activities between 2.4 and 3.8 mBq L{sup -1}, with highest activities in the topmost layer. These activities are higher than in seawater, suggesting that sediment act as a source of both {sup 210}Po and {sup 210}Pb for overlying water. The {sup 210}Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO{sub 4}{sup 2-}, suggesting an influence of early diagenetic processes on the {sup 210}Po solid-liquid distribution. In the sediment, {sup 210}Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that {sup 210}Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of {sup 210}Po bound to acid volatile sulphides in the sediment. {sup 210}Po, {sup 210}Pb and Pb exhibit differences in terms of distribution, probably due to a different mode of penetration in the sediment. This work provides information on solid and liquid distribution of {sup 210}Po and {sup 210}Pb in marine sediment. These data are very scarce in the litterature.

  13. Occurrence of arsenic in core sediments and groundwater in the Chapai-Nawabganj District, northwestern Bangladesh.

    Science.gov (United States)

    Selim Reza, A H M; Jean, Jiin-Shuh; Yang, Huai-Jen; Lee, Ming-Kuo; Woodall, Brian; Liu, Chia-Chuan; Lee, Jyh-Fu; Luo, Shang-De

    2010-03-01

    Groundwater and core sediments of two boreholes (to a depth of 50m) from the Chapai-Nawabganj area in northwestern Bangladesh were collected for arsenic concentration and geochemical analysis. Groundwater arsenic concentrations in the uppermost aquifer (10-40m of depth) range from 2.8microgL(-1) to 462.3microgL(-1). Groundwater geochemical conditions change from oxidized to successively more reduced, higher As concentration with depth. Higher sediment arsenic levels (55mgkg(-1)) were found within the upper 40m of the drilled core samples. X-ray absorption near-edge structure spectroscopy was employed to elucidate the arsenic speciation of sediments collected from two boreholes. Environmental scanning electron microscopy and transmission X-ray microscopy were used to investigate the characteristics of FeOOH in sediments which adsorb arsenic. In addition, a pH-Eh diagram was drawn using the Geochemist's Workbench (GWB) software to elucidate the arsenic speciation in groundwater. The dominant groundwater type is Ca-HCO(3) with high concentrations of As, Fe and Mn but low levels of NO(3)(-) and SO(4)(2-). Sequential extraction analysis reveals that Mn and Fe hydroxides and organic matter are the major leachable solids carrying As. High levels of arsenic concentration in aquifers are associated with fine-grained sediments. Fluorescent intensities of humic substances indicate that both groundwater and sediments in this arsenic hotspot area contain less organic matter compared to other parts of Bengal basin. Statistical analysis clearly shows that As is closely associated with Fe and Mn in sediments while As is better correlated with Mn in groundwater. These correlations along with results of sequential leaching experiments suggest that reductive dissolution of MnOOH and FeOOH mediated by anaerobic bacteria represents an important mechanism for releasing arsenic into the groundwater.

  14. Seasonal Arsenic Accumulation in Stream Sediments at a Groundwater Discharge Zone

    DEFF Research Database (Denmark)

    MacKay, Allison A.; Gan, Ping; Yu, Ran

    2014-01-01

    Seasonal changes in arsenic and iron accumulation rates were examined in the sediments of a brook that receives groundwater discharges of arsenic and reduced iron. Clean glass bead columns were deployed in sediments for known periods over the annual hydrologic cycle to monitor changes in arsenic...

  15. Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi, Vietnam

    Science.gov (United States)

    Kuroda, Keisuke; Hayashi, Takeshi; Funabiki, Ayako; Do, An Thuan; Canh, Vu Duc; Nga, Tran Thi Viet; Takizawa, Satoshi

    2017-01-01

    Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25-40 m depth, 9.6-4.8 cal ka uc(BP)) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25-94 μg/L) than in the HUA (5.2-42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.

  16. Effective bioremediation strategy for rapid in situ cleanup of anoxic marine sediments in mesocosm oil spill simulation.

    Directory of Open Access Journals (Sweden)

    Maria eGenovese

    2014-04-01

    Full Text Available The purpose of present study was the simulation of an oil spill accompanied by burial of significant amount of petroleum hydrocarbons (PHs in coastal sediments. Approximately 1,000 kg of sediments collected in Messina harbor were spiked with Bunker C furnace fuel oil (6,500 ppm. The rapid consumption of oxygen by aerobic heterotrophs created highly reduced conditions in the sediments with subsequent recession of biodegradation rates. As follows, after three months of ageing, the anaerobic sediments did not exhibit any significant levels of biodegradation and more than 80% of added Bunker C fuel oil remained buried. Anaerobic microbial community exhibited a strong enrichment in sulfate-reducing PHs-degrading and PHs-associated Deltaproteobacteria. As an effective bioremediation strategy to clean up these contaminated sediments, we applied a Modular Slurry System (MSS allowing the containment of sediments and their physical-chemical treatment, e.g. aeration. Aeration for three months has increased the removal of main PHs contaminants up to 98%. As revealed by CARD-FISH, qPCR and 16S rRNA gene clone library analyses, addition of Bunker C fuel oil initially affected the activity of autochthonous aerobic obligate marine hydrocarbonoclastic bacteria (OMHCB, and after one month more than the third of microbial population was represented by Alcanivorax-, Cycloclasticus- and Marinobacter-related organisms. In the end of the experiment, the microbial community composition has returned to a status typically observed in pristine marine ecosystems with no detectable OMHCB present. Eco-toxicological bioassay revealed that the toxicity of sediments after treatment was substantially decreased. Thus, our studies demonstrated that petroleum-contaminated anaerobic marine sediments could efficiently be cleaned through an in situ oxygenation which stimulates their self-cleaning potential due to reawakening of allochtonous aerobic OMHCB.

  17. Effective bioremediation strategy for rapid in situ cleanup of anoxic marine sediments in mesocosm oil spill simulation.

    Science.gov (United States)

    Genovese, Maria; Crisafi, Francesca; Denaro, Renata; Cappello, Simone; Russo, Daniela; Calogero, Rosario; Santisi, Santina; Catalfamo, Maurizio; Modica, Alfonso; Smedile, Francesco; Genovese, Lucrezia; Golyshin, Peter N; Giuliano, Laura; Yakimov, Michail M

    2014-01-01

    The purpose of present study was the simulation of an oil spill accompanied by burial of significant amount of petroleum hydrocarbons (PHs) in coastal sediments. Approximately 1000 kg of sediments collected in Messina harbor were spiked with Bunker C furnace fuel oil (6500 ppm). The rapid consumption of oxygen by aerobic heterotrophs created highly reduced conditions in the sediments with subsequent recession of biodegradation rates. As follows, after 3 months of ageing, the anaerobic sediments did not exhibit any significant levels of biodegradation and more than 80% of added Bunker C fuel oil remained buried. Anaerobic microbial community exhibited a strong enrichment in sulfate-reducing PHs-degrading and PHs-associated Deltaproteobacteria. As an effective bioremediation strategy to clean up these contaminated sediments, we applied a Modular Slurry System (MSS) allowing the containment of sediments and their physical-chemical treatment, e.g., aeration. Aeration for 3 months has increased the removal of main PHs contaminants up to 98%. As revealed by CARD-FISH, qPCR, and 16S rRNA gene clone library analyses, addition of Bunker C fuel oil initially affected the activity of autochthonous aerobic obligate marine hydrocarbonoclastic bacteria (OMHCB), and after 1 month more than the third of microbial population was represented by Alcanivorax-, Cycloclasticus-, and Marinobacter-related organisms. In the end of the experiment, the microbial community composition has returned to a status typically observed in pristine marine ecosystems with no detectable OMHCB present. Eco-toxicological bioassay revealed that the toxicity of sediments after treatment was substantially decreased. Thus, our studies demonstrated that petroleum-contaminated anaerobic marine sediments could efficiently be cleaned through an in situ oxygenation which stimulates their self-cleaning potential due to reawakening of allochtonous aerobic OMHCB.

  18. Pyrite framboid size distribution as a record for relative variations in sedimentation rate: An example on the Toarcian Oceanic Anoxic Event in Southiberian Palaeomargin

    Science.gov (United States)

    Gallego-Torres, David; Reolid, Matías; Nieto-Moreno, Vanesa; Martínez-Casado, Francisco Javier

    2015-12-01

    The Early Toarcian Oceanic Anoxic Event (T-OAE) represents one of the major alterations of the carbon cycle of the Mesozoic period. Despite being globally recognized, and particularly represented within the Tethys realm, its expression in the sedimentary record is highly variable depending on the studied section, which suggests local environmental factors exert a major control on the resulting lithological appearance of the event. We investigated the Fuente Vidriera section, in the eastern External Subbetic of the Betic Cordillera (Spain), where the Lower Jurassic is represented by alternate layers of marls and marly limestones, and the T-OAE is identified by a major δ13C excursion, micropalaeontological, ichnofacies and geochemical evidences. For this study, we analyzed pyrite framboid size distribution of the sedimentary sequence in Fuente Vidriera. The outcome, according to previous studies on pyrite framboid distribution, is contradictory when compared to all other evidences, suggesting oxygen depletion during the T-OAE. The results have been reinterpreted in the light of Crystal Size Distribution Theory and we conclude that not only growth time but also geochemical environment controls pyrite formation. Since growth time is directly related to burial rates, this approach allows us to reconstruct relative variations of sedimentation rates during the Early Jurassic in this location. Based on the obtained results, we provide new evidences for wide-spread transgression during the Early Toarcian in the South Iberian palaeomargin, which induced low sedimentation rate and lower energetic conditions, as well as favored oxygen impoverished bottom waters.

  19. Groundwater control on the suspended sediment load in the Na Borges River, Mallorca, Spain

    Science.gov (United States)

    Estrany, Joan; Garcia, Celso; Batalla, Ramon J.

    2009-05-01

    Groundwater dominance has important effects on the hydrological and geomorphological characteristics of river systems. Low suspended sediment concentrations and high water clarity are expected because significant inputs of sediment-free spring water dilute the suspended sediment generated by storms. However, in many Mediterranean rivers, groundwater dominance is characterised by seasonal alternations of influent and effluent discharge involving significant variability on the sediment transport regimes. Such areas are often subject to soil and water conservation practices over the centuries that have reduced the sediment contribution from agricultural fields and favour subsurface flow to rivers. Moreover, urbanisation during the twentieth century has changed the catchment hydrology and altered basic river processes due to its 'flashy' regime. In this context, we monitored suspended sediment fluxes during a two-year period in the Na Borges River, a lowland agricultural catchment (319 km 2) on the island of Mallorca (Balearic Islands). The suspended sediment concentration (SSC) was lower when the base flow index (i.e., relative proportion of baseflow compared to stormflow, BFI) was higher. Therefore, strong seasonal contrasts explain the high SSC coefficient of variation, which is clearly related to dilution effects associated with different groundwater and surface water seasonal interactions. A lack of correlation in the Q-SSC rating curves shows that factors other than discharge control sediment transport. As a result, at the event scale, multiple regressions illustrate that groundwater and surface water interactions are involved in the sedimentary response of flood events. In the winter, the stability of baseflow driven by groundwater contributions and agricultural and urban spills causes hydraulic variables (i.e., maximum discharge) to exert the most important control on events, whereas in the summer, it is necessary to accumulate important volumes of rainfall

  20. Monitoring the primary biodegradation of linear alkylbenzene sulfonates and their coproducts in anoxic sediments using liquid chromatography-mass spectrometry.

    Science.gov (United States)

    Lara-Martín, Pablo A; Gómez-Parra, Abelardo; Köchling, Thorsten; Sanz, José Luis; González-Mazo, Eduardo

    2007-05-15

    An accompanying article has demonstrated the anaerobic degradation of the surfactant linear alkylbenzene sulfonate (LAS) in microcosms filled with marine sediments through the generation of sulfophenylcarboxylic acids (SPCs). A detailed study shows that this process was uniform in the blanks (non-spiked natural sediments) for every LAS homologue during the complete course of the experiment. However, when sediments were spiked with commercial LAS and, therefore, enriched with short-chain homologues, degradation was enhanced for these homologues until their percentages were close to those for non-spiked sediments. The reason is that short-chain homologues are more bioavailable due to their higher solubility and lower sorption capacity. Thus, sorption on sediments was found to be increased with the length of the alkyl chain for LAS homologues, following a linear Freundlich isotherm, whereas the metabolites generated were predominant in solution due to their much higher polarity. Intermediate-chain SPC homologues (C7-C9 SPCs) were the most abundant during the experiment, but a significant increase in the concentration of shorter-chain SPC homologues (C4-C6 SPCs) was detected toward the end. In the case of isomers, the steric effect of the aromatic group implies that LAS primary degradation took place preferentially over external isomers. Therefore, the generation of external isomers of SPCs was predominant during the complete experiment although internal isomers of SPCs became more evident when the degradation process had advanced and external isomers of LAS became scarce. The identity of both types of SPC isomer was confirmed by tandem mass spectrometry. With respect to LAS coproducts, the relative percentage of iso-LAS increased during the complete experiment and removal percentages for dialkyl tetralinsulfonates (<30%) were typically lower that those for LAS (66-79%), although a similar behavior was observed for their homologues in both cases.

  1. Evaluation model coupling exploitable groundwater resources and land subsidence control in regional loose sediments

    Science.gov (United States)

    Luo, Z. J.; Zhao, S. J.; Jin, WZ; Ma, Q. S.; Wu, X. H.

    2016-08-01

    The loose sediments in the Yangtze River Delta, the North China Plain, the plain of Northern Jiangsu and other districts in China are of great thickness, complex in structure and abundant in groundwater. Groundwater overexploitation easily results in geological disasters of land subsidence. Aiming at the issues, assessment models coupling exploitable groundwater resources and land subsidence control in regional loose sediments were brought up in this paper. The two models were: (1) a three dimensional groundwater seepage model with land subsidence based on the one dimensional Terzaghi consolidation theory; (2) a three dimensional full coupling model on groundwater seepage and land subsidence based on the Biot consolidation theory to simulate and calculate. It can be used to simulate and calculate the problems in real situations. Thus, the groundwater seepage and land subsidence were coupled together in the model to evaluate the amount of exploitable groundwater under the specific requirements of land subsidence control. The full coupling model, which considers the non-linear characteristics of soil mass and the dynamic changes of soil permeability with stress state based on the Biot consolidation theory, is more coincident with the variation characteristics of the hydraulic and mechanical properties of soil mass during the pumping process, making the evaluation results more scientific and reasonable.

  2. Identifying fermenting bacteria in anoxic tidal-flat sediments by a combination of microcalorimetry and ribosome-based stable-isotope probing.

    Science.gov (United States)

    Graue, Jutta; Kleindienst, Sara; Lueders, Tillmann; Cypionka, Heribert; Engelen, Bert

    2012-07-01

    A novel approach was developed to follow the successive utilization of organic carbon under anoxic conditions by microcalorimetry, chemical analyses of fermentation products and stable-isotope probing (SIP). The fermentation of (13) C-labeled glucose was monitored over 4 weeks by microcalorimetry in a stimulation experiment with tidal-flat sediments. Based on characteristic heat production phases, time points were selected for quantifying fermentation products and identifying substrate-assimilating bacteria by the isolation of intact ribosomes prior to rRNA-SIP. The preisolation of ribosomes resulted in rRNA with an excellent quality. Glucose was completely consumed within 2 days and was mainly fermented to acetate. Ethanol, formate, and hydrogen were detected intermittently. The amount of propionate that was built within the first 3 days stayed constant. Ribosome-based SIP of fully labeled and unlabeled rRNA was used for fingerprinting the glucose-degrading species and the inactive background community. The most abundant actively degrading bacterium was related to Psychromonas macrocephali (similarity 99%) as identified by DGGE and sequencing. The disappearance of Desulfovibrio-related bands in labeled rRNA after 3 days indicated that this group was active during the first degradation phase only. In summary, ribosome-based SIP in combination with microcalorimetry allows dissecting distinct phases in substrate turnover in a very sensitive manner.

  3. Soil, Groundwater, Surface Water, and Sediments of Kennedy Space Center, Florida: Background Chemical and Physical Characteristics

    Science.gov (United States)

    Shmalzer, Paul A.; Hensley, Melissa A.; Mota, Mario; Hall, Carlton R.; Dunlevy, Colleen A.

    2000-01-01

    This study documented background chemical composition of soils, groundwater, surface; water, and sediments of Kennedy Space Center. Two hundred soil samples were collected, 20 each in 10 soil classes. Fifty-one groundwater wells were installed in 4 subaquifers of the Surficial Aquifer and sampled; there were 24 shallow, 16 intermediate, and 11 deep wells. Forty surface water and sediment samples were collected in major watershed basins. All samples were away from sites of known contamination. Samples were analyzed for organochlorine pesticides, aroclors, chlorinated herbicides, polycyclic aromatic hydrocarbons (PAH), total metals, and other parameters. All aroclors (6) were below detection in all media. Some organochlorine pesticides were detected at very low frequencies in soil, sediment, and surface water. Chlorinated herbicides were detected at very low frequencies in soil and sediments. PAH occurred in low frequencies in soiL, shallow groundwater, surface water, and sediments. Concentrations of some metals differed among soil classes, with subaquifers and depths, and among watershed basins for surface water but not sediments. Most of the variation in metal concentrations was natural, but agriculture had increased Cr, Cu, Mn, and Zn.

  4. Degradation of cyanobacterial biomass in anoxic tidal-flat sediments: a microcosm study of metabolic processes and community changes.

    Science.gov (United States)

    Graue, Jutta; Engelen, Bert; Cypionka, Heribert

    2012-03-01

    To follow the anaerobic degradation of organic matter in tidal-flat sediments, a stimulation experiment with (13)C-labeled Spirulina biomass (130 mg per 21 g sediment slurry) was conducted over a period of 24 days. A combination of microcalorimetry to record process kinetics, chemical analyses of fermentation products and RNA-based stable-isotope probing (SIP) to follow community changes was applied. Different degradation phases could be identified by microcalorimetry: Within 2 days, heat output reached its maximum (55 μW), while primary fermentation products were formed (in μmol) as follows: acetate 440, ethanol 195, butyrate 128, propionate 112, H(2) 127 and smaller amounts of valerate, propanol and butanol. Sulfate was depleted within 7 days. Thereafter, methanogenesis was observed and secondary fermentation proceeded. H(2) and alcohols disappeared completely, whereas fatty acids decreased in concentration. Three main degraders were identified by RNA-based SIP and denaturant gradient gel electrophoresis. After 12 h, two phylotypes clearly enriched in (13)C: (i) Psychrilyobacter atlanticus, a fermenter known to produce hydrogen and acetate and (ii) bacteria distantly related to Propionigenium. A Cytophaga-related bacterium was highly abundant after day 3. Sulfate reduction appeared to be performed by incompletely oxidizing species, as only sulfate-reducing bacteria related to Desulfovibrio were labeled as long as sulfate was available.

  5. Groundwater and Human Controls on the Suspended Sediment Load of Na Borges River, Mallorca (Spain)

    Science.gov (United States)

    Estrany, J.; Garcia, C.

    2009-04-01

    Groundwater dominance has important effects on the hydrological and geomorphological characteristics of river systems. Low suspended sediment concentrations and high water clarity are expected because significant inputs of sediment-free spring water dilute the suspended sediment generated by storms. However, in many Mediterranean temporary rivers, groundwater dominance is characterised by seasonal alternations of influent and effluent discharge involving significant variability on the sediment transport regimes. Such areas are often subject to soil and water conservation practices over the centuries that have reduced the sediment contribution from agricultural fields and favour subsurface flow to rivers. Moreover, urbanisation during the twentieth century has changed the catchment hydrology and altered basic river processes due to its ‘flashy' regime. In this context, we monitored suspended sediment fluxes by means of three nested sub-catchments during a two-year period in the Na Borges River, a lowland agricultural catchment (319 km2) on the island of Mallorca (Balearic Islands) managed and therefore modified since Roman Age by agricultural soil and water conservation practices and recently by urbanisation. The suspended sediment concentration (SSC) was lower when the base flow index (i.e., relative proportion of baseflow compared to stormflow, BFI) was higher. Considering the high variability of the Mediterranean climate, a significant scatter of daily average SSC between sites and seasonally was observed, ranging between 22 to 54 mg l-1 for the total study period. The maximum instantaneous peak surpassed 6,000 mg l-1, recorded at downstream site based on the sediment supplied when there was no baseflow and the rainfall intensity was remarkable. At the other sites, peak concentrations did not exceed 2,000 mg l-1 because groundwater plays a more significant role. Furthermore, strong seasonal contrasts explain the high SSC coefficient of variation, which is

  6. Is these a link between eustatic variations, platform drowning, oceanic anoxic events, and ammonite faunal turnovers ? Case study of the Aptian sediments along the northern Tethyan margin

    Science.gov (United States)

    Pictet, Antoine; Föllmi, Karl; Spangenberg, Jorge

    2014-05-01

    The early Aptian witnessed an important episode of paleoenvironmental change, which has been linked to major marine volcanic activity related to the formation of the Ontong-Java large igneous province (e.g., Larson and Erba, 1999). This phase culminated in the formation of hemipelagic and pelagic organic-rich sediments, whereas profound changes are also observed in shallow-water settings, with the step-by-step disappearance of the northern Tethyan platform. Results show that the northern Tethyan platform has passed through three major crises in its evolution during the early Aptian. A first one started with an emersion phase, marked by a subaerial karstified discontinuity reported from the middle early Aptian (Deshayesites forbesi or early D. deshayesi zone). This is directly followed by the drowning of the Urgonian platform along the northern Tethyan margin, preceding the Selli Episode. The period following this drowning phase coincides with the negative and the following positive excursions in the δ13C records and went along with the deposition of the so-called Lower Grünten Member, which is the result of heterozoan carbonate production and characterized by increased detrital input. Ammonite fauna witnessed an important diversification of hemipelagic forms, especially inside the heteromorph Ancyloceratacea. This radiation is probably linked to the expansion of hemipelagic facies, one of the main habitats of ammonites. A second phase, reported from the late early Aptian (late D. deshayesi zone), started with a small drowning event, marked by a firmground and by a phosphatic enrichment. This stratigraphical layer also corresponds to the establishment of the anoxic Apparein level. Above, the Upper Grünten Member continues with heterozoan carbonate production or with glauconitic condensed sediments. The corresponding δ13C record is a the onset of a long-term decrease. The ammonite fauna is marked by a first turnover with the disappearance of Deshayesites, and the

  7. Hydrogeology and hydrochemistry of groundwater-dominated lakes

    DEFF Research Database (Denmark)

    Kazmierczak, Jolanta

    and tracking groundwater flow paths and, thus, to determine the source of the water. These observations were confirmed and explained by flow models. The results of the 2D and 3D flow modelling showed that groundwater contribution is 75% of the total water input into the lake, out of which 35% discharges...... is mobilized in the sediments of the old lake/stream bottom due to reductive dissolution of iron hydroxides by organic matter. The process is triggered by the discharge of anoxic groundwater from the deeper parts of the aquifer to the near shore environment. High groundwater seepage rates do not leave enough...

  8. Reservoir sediments: a sink or source of chemicals at the surface water-groundwater interface.

    Science.gov (United States)

    Ammar, Rawaa; Kazpard, Véronique; Wazne, Mahmoud; El Samrani, Antoine G; Amacha, Nabil; Saad, Zeinab; Chou, Lei

    2015-09-01

    This study delineates the physical, chemical, and biological effects resulting from anthropogenic and endogenic activities in a sensitive dammed reservoir situated in a semi-arid region. The reservoir is characterized by two major flow regimes: a wet fill hydrologic regime and a dry spill one. A seasonal sampling campaign was carried out over a period of 2 years (2011-2013) where water samples were collected across the water column and from piezometers just outside the perimeter of the reservoir. Similarly, sediments were collected from the corresponding areas beneath the water column. The water samples were analyzed for environmental isotopic ratios, elemental composition, and physical, biological and chemical parameters, whereas the sediment and algal samples were subjected to physical, mineralogical, spectroscopic, and microscopic analyses. This investigation indicated that the dam had resulted in the alteration of the biogeochemical cycle of nutrients as well as the degradation of the sediment and water quality. The hydrological and biogeochemical processes were found to induce vertical downward transport of chemicals towards the fine grained calcareous sediments during the fill mode, whereas the sediments acted as a source of a chemical flux upward through the water column and downward towards the groundwater during the spill mode. The geomorphological characteristics of the reservoir enhanced the strong hydrological connectivity between the surface water and the groundwater where the reservoir responded quickly to natural and anthropogenic changes in the upper watershed. The water and sediments in the sensitive spill mode were of poor quality and should receive more attention due to the potential hazard for the associated hydro-project and the sustainability of the agricultural soil in the long term. Thus, a safe water and sediment management plan should be implemented in order to improve the dam functionality and to safeguard the precious water resources.

  9. Transport behavior of groundwater protozoa and protozoan-sized microspheres in sandy aquifer sediments

    Science.gov (United States)

    Harvey, R.W.; Kinner, N.E.; Bunn, A.; MacDonald, D.; Metge, D.

    1995-01-01

    Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 ??m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-??m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 ??m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 ??m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2- ??m carboxylated microspheres may be useful as analogs in investigating several abiotic

  10. Cs-137 geochronology, epithermal neutron activation analysis, and principal component analysis of heavy metals pollution of the Black Sea anoxic continental shelf sediments

    Science.gov (United States)

    Duliu, O. G.; Cristache, C.; Oaie, G.; Culicov, O. A.; Frontasyeva, M. V.

    2009-04-01

    Anthropogenic Cs-137 Gamma-ray Spectroscopy assay (GrSA) performed at the National Institute of Research and Development for Physics and Nuclear Engineering - Bucharest (Romania) in correlation with Epithermal Neutrons Activation Analysis (ENAA) performed at the Joint Institute of Nuclear Researches - Dubna (Russia) were used to investigate a 50 cm core containing unconsolidated sediments collected at a depth of 600 m off Romanian town of Constantza, located in the anoxic zone of the Black Sea Continental Shelf. A digital radiography showed the presence of about 265 distinct laminae, 1 to 3 mm thick, a fact attesting a stationary sedimentary process, completely free of bioturbation. After being radiographed, the core was sliced into 45 segments whose thickness gradually increased from 0.5 to 5 cm, such that the minimum thickness corresponded to the upper part of the core. From each segment two aliquots of about 0.5 g and 50 g were extracted for subsequent ENAA and Cs-137 GrSA. The Cs-137 vertical profile evidenced two maxima, one of them was very sharp and localized at a depth of 1 cm and the other very broad, almost undistinguished at about 8 cm depth, the first one being attributed to 1986 Chernobyl accident. Based on these date, we have estimated a sedimentation ratio of about 0.5 mm/year, value taken as reference for further assessment of recent pollution history. By means of ENAA we have determined the vertical content of five presumed pollutants, e.i. Zn, As, Br, Sn and Sb and of Sc, as natural, nonpolluting element. In the first case, all five elements presented a more or less similar vertical profile consisting of an almost exponential decrease for the first 10 cm below sediment surface followed by a plateau until the core base, i.e. 50 cm below surface, dependency better described by the equation: c(z) = c0 [1+k exp (-z/Z)] (1) where: where c(z) represents the concentration vertical profile; z represents depth (in absolute value); c0 represents the plateau

  11. Characterization of sediment and measurement of groundwater levels and temperatures, Camas National Wildlife Refuge, eastern Idaho

    Science.gov (United States)

    Twining, Brian V.; Rattray, Gordon W.

    2016-11-02

    The Camas National Wildlife Refuge (Refuge) in eastern Idaho, established in 1937, contains wetlands, ponds, and wet meadows that are essential resting and feeding habitat for migratory birds and nesting habitat for waterfowl. Initially, natural sources of water supported these habitats. However, during the past few decades, climate change and changes in surrounding land use have altered and reduced natural groundwater and surface water inflows such that the wetlands, ponds, and wet meadows are now maintained through water management and groundwater pumping. These water management activities have proven to be inefficient and costly, prompting the Refuge to develop alternative water management options that are more efficient and less expensive. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, is studying the hydrogeology at the Refuge to provide information for developing alternative water management options.The hydrogeologic studies at the Refuge included characterizing the type, distribution, and hydraulic conductivity of surficial sediments and measuring water levels and temperatures in monitoring wells. Four monitoring wells and seven soil probe coreholes were drilled at the Refuge. Seven water level and temperature data loggers were installed in the wells and water levels and temperatures were continuously recorded from November 2014 to June 2016. Sediment cores were collected from the coreholes and sediment type and distribution were characterized from drillers’ notes, geophysical logs, corehole samples, and particle grain-size analysis. The hydraulic conductivities of sediments were estimated using the measured average grain size and the assumed textural maturity of the sediment, and ranged from about 20 to 290 feet per day.

  12. Arsenic release from shallow aquifers of the Hetao basin, Inner Mongolia: evidence from bacterial community in aquifer sediments and groundwater.

    Science.gov (United States)

    Li, Yuan; Guo, Huaming; Hao, Chunbo

    2014-12-01

    Indigenous microbes play crucial roles in arsenic mobilization in high arsenic groundwater systems. Databases concerning the presence and the activity of microbial communities are very useful in evaluating the potential of microbe-mediated arsenic mobilization in shallow aquifers hosting high arsenic groundwater. This study characterized microbial communities in groundwaters at different depths with different arsenic concentrations by DGGE and one sediment by 16S rRNA gene clone library, and evaluated arsenic mobilization in microcosm batches with the presence of indigenous bacteria. DGGE fingerprints revealed that the community structure changed substantially with depth at the same location. It indicated that a relatively higher bacterial diversity was present in the groundwater sample with lower arsenic concentration. Sequence analysis of 16S rRNA gene demonstrated that the sediment bacteria mainly belonged to Pseudomonas, Dietzia and Rhodococcus, which have been widely found in aquifer systems. Additionally, NO3(-)-reducing bacteria Pseudomonas sp. was the largest group, followed by Fe(III)-reducing, SO4(2-)-reducing and As(V)-reducing bacteria in the sediment sample. These anaerobic bacteria used the specific oxyanions as electron acceptor and played a significant role in reductive dissolution of Fe oxide minerals, reduction of As(V), and release of arsenic from sediments into groundwater. Microcosm experiments, using intact aquifer sediments, showed that arsenic release and Fe(III) reduction were microbially mediated in the presence of indigenous bacteria. High arsenic concentration was also observed in the batch without amendment of organic carbon, demonstrating that the natural organic matter in sediments was the potential electron donor for microbially mediated arsenic release from these aquifer sediments.

  13. 3-D VARIABLE PARAMETER NUMERICAL MODEL FOR EVALUATION OF THE PLANNED EXPLOITABLE GROUNDWATER RESOURCE IN REGIONAL UNCONSOLIDATED SEDIMENTS

    Institute of Scientific and Technical Information of China (English)

    LUO Zu-jiang; WANG Yan

    2012-01-01

    In order to correctly evaluate the exploitable groundwater resource in regional complex,thick Quaternary unconsolidated sediments,the whole Quaternary unconsolidated sediments are considered as a unified hydrogeological unit and a 3-D unsteady groundwater flow numerical model is adopted.Meanwhile,with the consideration of the dynamic changes of the porosity,the hydraulic conductivity and the specific storage with the groundwater level dropping during the exploitation process,an improved composite element seepage matrix adjustment method is applied to solve the unsteady flow problem of free surface.In order to evaluate the exploitable groundwater resource in Cangzhou,Hebei Province,the hydrogeological conceptual model of Cangzhou is generalized to establish,a 3-D variable parameter numerical model of Cangzhou.Based on the prediction of the present groundwater exploitation,and by adjusting the groundwater exploitation layout,the exploitable groundwater resource is predicted.The model enjoys features like good convergence,good stability and high precision.

  14. Pathways for arsenic from sediments to groundwater to streams: Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA

    Science.gov (United States)

    Barringer, Julia L.; Mumford, Adam; Young, Lily Y.; Reilly, Pamela A.; Bonin, Jennifer L.; Rosman, Robert

    2010-01-01

    The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15–25 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 μg/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any process—natural or anthropogenic—that increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials.

  15. In situ groundwater and sediment bioremediation: barriers and perspectives at European contaminated sites.

    Science.gov (United States)

    Majone, Mauro; Verdini, Roberta; Aulenta, Federico; Rossetti, Simona; Tandoi, Valter; Kalogerakis, Nicolas; Agathos, Spiros; Puig, Sebastià; Zanaroli, Giulio; Fava, Fabio

    2015-01-25

    This paper contains a critical examination of the current application of environmental biotechnologies in the field of bioremediation of contaminated groundwater and sediments. Based on analysis of conventional technologies applied in several European Countries and in the US, scientific, technical and administrative barriers and constraints which still need to be overcome for an improved exploitation of bioremediation are discussed. From this general survey, it is evident that in situ bioremediation is a highly promising and cost-effective technology for remediation of contaminated soil, groundwater and sediments. The wide metabolic diversity of microorganisms makes it applicable to an ever-increasing number of contaminants and contamination scenarios. On the other hand, in situ bioremediation is highly knowledge-intensive and its application requires a thorough understanding of the geochemistry, hydrogeology, microbiology and ecology of contaminated soils, groundwater and sediments, under both natural and engineered conditions. Hence, its potential still remains partially unexploited, largely because of a lack of general consensus and public concerns regarding the lack of effectiveness and control, poor reliability, and possible occurrence of side effects, for example accumulation of toxic metabolites and pathogens. Basic, applied and pre-normative research are all needed to overcome these barriers and make in situ bioremediation more reliable, robust and acceptable to the public, as well as economically more competitive. Research efforts should not be restricted to a deeper understanding of relevant microbial reactions, but also include their interactions with the large array of other relevant phenomena, as a function of the truly variable site-specific conditions. There is a need for a further development and application of advanced biomolecular tools for site investigation, as well as of advanced metabolic and kinetic modelling tools. These would allow a

  16. Occurrence of pesticides in groundwater and sediments and mineralogy of sediments and grain coatings underlying the Rutgers Agricultural Research and Extension Center, Upper Deerfield, New Jersey, 2007

    Science.gov (United States)

    Reilly, Timothy J.; Smalling, Kelly L.; Meyer, Michael T.; Sandstrom, Mark W.; Hladik, Michelle L.; Boehlke, Adam R.; Fishman, Neil S.; Battaglin, William A.; Kuivila, Kathryn M.

    2014-01-01

    Water and sediment samples were collected from June through October 2007 from seven plots at the Rutgers Agricultural Research and Extension Center in Upper Deerfield, New Jersey, and analyzed for a suite of pesticides (including fungicides) and other physical and chemical parameters (including sediment mineralogy) by the U.S. Geological Survey. Plots were selected for inclusion in this study on the basis of the crops grown and the pesticides used. Forty-one pesticides were detected in 14 water samples; these include 5 fungicides, 13 herbicides, 1 insecticide, and 22 pesticide degradates. The following pesticides and pesticide degradates were detected in 50 percent or more of the groundwater samples: 1-amide-4-hydroxy-chorothalonil, alachlor sulfonic acid, metolachlor oxanilic acid, metolachlor sulfonic acid, metalaxyl, and simazine. Dissolved-pesticide concentrations ranged from below their instrumental limit of detection to 36 micrograms per liter (for metolachlor sulfonic acid, a degradate of the herbicide metolachlor). The total number of pesticides found in groundwater samples ranged from 0 to 29. Fourteen pesticides were detected in sediment samples from continuous cores collected within each of the seven sampled plots; these include 4 fungicides, 2 herbicides, and 7 pesticide degradates. Pesticide concentrations in sediment samples ranged from below their instrumental limit of detection to 34.2 nanograms per gram (for azoxystrobin). The total number of pesticides found in sediment samples ranged from 0 to 8. Quantitative whole-rock and grain-coating mineralogy of sediment samples were determined by x-ray diffraction. Whole-rock analysis indicated that sediments were predominantly composed of quartz. The materials coating the quartz grains were removed to allow quantification of the trace mineral phases present.

  17. Implications of Fe/Pd Bimetallic Nanoparticles Immobilized on Adsorptive Activated Carbon for the Remediation of Groundwater and Sediment Contaminated with PCBs

    Science.gov (United States)

    In order to respond to the current limitations and challenges in remediating groundwater and sediment contaminated with polychlorinated biphenyls (PCBs), we have recently developed a new strategy, integration of the physical adsorption of PCBs with their electrochemical dechlori...

  18. Characterization of Organic Carbon and Its Bioavailability in Recharge Waters and Aquifer Sediments: Implications for Groundwater Arsenic Contamination in Bangladesh

    Science.gov (United States)

    Pracht, L. E.; Ardissono, R. J.; Polizzotto, M.; Badruzzaman, A. B. M.; Ali, M. A.; Paša-Tolić, L.; Neumann, R. B.

    2014-12-01

    Arsenic contamination of groundwater in Bangladesh affects millions of people, as groundwater is the primary source of both drinking and irrigation water in the country. The arsenic is of geologic origin, naturally-occurring in the aquifer sediment. However, the source of organic carbon that fuels the microbial reactions responsible for mobilizing arsenic off the sediment and into the groundwater has been debated for over a decade. The outstanding question is whether this organic carbon is sedimentary carbon that was co-deposited when the aquifers were formed, or surface-derived organic carbon transported into the subsurface along with recharge water. The answer to this question has implications for managing the contamination problem. Here we present results of recent laboratory incubations of aquifer sediment with recharge waters collected from our field site in Bangladesh. The incubations revealed a hitherto undocumented pool of biodegradable sedimentary organic carbon. Despite the carbon being old (thousands of years), it was rapidly utilized by the native microbial population. The results imply that within the aquifer this pool of sedimentary organic carbon is largely unavailable to the microbial community, but that chemical and/or physical perturbations to the subsurface, induced, for example, by large-scale groundwater pumping or microbial activity, could mobilize this bioavailable organic carbon off the sediment. Currently, we are using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and spectroscopic techniques to understand the initial character of the mobilized organic carbon in our incubation experiments, and to track how its composition changes over time as it is degraded by microbes. These efforts will help clarify the in situ processes that could destabilize the sedimentary organic carbon and identify the components that make the carbon biologically available. Collectively, our data suggest a possible role for both surface-derived and

  19. Hydrologic controls on nitrogen cycling processes and functional gene abundance in sediments of a groundwater flow-through lake

    Science.gov (United States)

    Stoliker, Deborah L.; Repert, Deborah A.; Smith, Richard L.; Song, Bongkeun; LeBlanc, Denis R.; McCobb, Timothy D.; Conaway, Christopher; Hyun, Sung Pil; Koh, Dong-Chan; Moon, Hee Sun; Kent, Douglas B.

    2016-01-01

    The fate and transport of inorganic nitrogen (N) is a critically important issue for human and aquatic ecosystem health because discharging N-contaminated groundwater can foul drinking water and cause algal blooms. Factors controlling N-processing were examined in sediments at three sites with contrasting hydrologic regimes at a lake on Cape Cod, MA. These factors included water chemistry, seepage rates and direction of groundwater flow, and the abundance and potential rates of activity of N-cycling microbial communities. Genes coding for denitrification, anaerobic ammonium oxidation (anammox), and nitrification were identified at all sites regardless of flow direction or groundwater dissolved oxygen concentrations. Flow direction was, however, a controlling factor in the potential for N-attenuation via denitrification in the sediments. Potential rates of denitrification varied from 6 to 4500 pmol N/g/h from the inflow to the outflow side of the lake, owing to fundamental differences in the supply of labile organic matter. The results of laboratory incubations suggested that when anoxia and limiting labile organic matter prevailed, the potential existed for concomitant anammox and denitrification. Where oxic lake water was downwelling, potential rates of nitrification at shallow depths were substantial (1640 pmol N/g/h). Rates of anammox, denitrification, and nitrification may be linked to rates of organic N-mineralization, serving to increase N-mobility and transport downgradient.

  20. Applications of Nano Reactive Materials in Remediation of Persistence Organic Pollutants in Sediments and Groundwater - Presentation

    Science.gov (United States)

    Remediation of sediments and water contaminated hydrophobic organic chemicals (HOCs) such as polychlorinated biphenyls (PCBs) remains a scientific and technical challenge. PCBs-contaminated sediments are ubiquitous despite the production and use of PCBs was banned in 1979 due to...

  1. Diatoms respire nitrate to survive dark and anoxic conditions

    DEFF Research Database (Denmark)

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L.

    2011-01-01

    Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO3− intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11–274 mM NO3− in th...

  2. Characterization of 200-UP-1 Aquifer Sediments and Results of Sorption-Desorption Tests Using Spiked Uncontaminated Groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Serne, R JEFFREY.; Bjornstad, Bruce N.; Schaef, Herbert T.; Brown, Christopher F.; Legore, Virginia L.; Geiszler, Keith N.; Baum, Steven R.; Valenta, Michelle M.; Kutnyakov, Igor V.; Vickerman, Tanya S.; Lindberg, Michael J.

    2005-11-16

    increasing concentrations of carbonate up to a point. Then as carbonate and calcium concentrations in the groundwater reach values that exceed the solubility limit for the mineral calcite there is a slight increase in U(VI) Kd likely caused by uranium co-precipitation with the fresh calcite. If remediation of the UP-1 groundwater plume is required, such as pump and treat, it is recommended that the aquifer be treated with chemicals to increase pH and alkalinity and decrease dissolved calcium and magnesium [so that the precipitation of calcite is prevented]. Alternative methods to immobilize the uranium in place might be more effective than trying to remove the uranium by pump and treat. Unfortunately, no aquifer sediments were obtained that contained enough Hanford generated uranium to perform quantitative desorption tests germane to the UP-1 plume remediation issue. Recommended Kd values that should be used for risk predictions for the UP-1 groundwater plume traveling through the lithologies within the aquifer present at the UP-1 (and by proxy ZP-1) operable units were provided. The recommended values Kd values are chosen to include some conservatism (lower values are emphasized from the available range) as is standard risk assessment practice. In general, desorption Kd values for aged contaminated sediments can be larger than Kd values determined in short-term laboratory experiments. To accommodate the potential for desorption hysteresis and other complications, a second suite of uranium desorption Kd values were provided to be used to estimate removal of uranium by pump and treat techniques.

  3. Microbial community characterization and functional gene quantification in RDX-degrading microcosms derived from sediment and groundwater at two naval sites.

    Science.gov (United States)

    Wilson, Fernanda Paes; Cupples, Alison M

    2016-08-01

    The explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has long been recognized as a problematic environmental pollutant, and efforts to remediate contaminated soils, sediments, and groundwater have been going on for decades. In recent years, much interest has focused on using bioremediation to clean up these sites. The current study investigated the microorganisms (16S rRNA genes, Illumina) and functional genes (xenA, xenB, and xplA) linked to RDX biodegradation in microcosms composed of sediment or groundwater from two Navy sites. For this, experiments included sediment samples from three depths (5 to 30 ft) from two wells located in one Navy site. In addition, the groundwater upstream and downstream of an emulsified oil biobarrier was examined from another Navy site. Further, for the groundwater experiments, the effect of glucose addition was explored. For the sediment experiments, the most enriched phylotypes during RDX degradation varied over time, by depth and well locations. However, several trends were noted, including the enrichment of Pseudomonas, Rhodococcus, Arthrobacter, and Sporolactobacillus in the sediment microcosms. For the groundwater-based experiments, Pseudomonas, unclassified Rhodocyclaceae, Sphingomonas, and Rhodococcus were also highly abundant during RDX degradation. The abundance of both xplA and xenA significantly increased during RDX degradation compared to the control microcosms for many treatments (both groundwater and sediment microcosms). In a limited number of microcosms, the copy number of the xenB gene increased. Phylotype data were correlated with functional gene data to highlight potentially important biomarkers for RDX biodegradation at these two Navy sites.

  4. An open ocean record of the Toarcian oceanic anoxic event

    OpenAIRE

    2011-01-01

    Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associ...

  5. The first metazoa living in permanently anoxic conditions

    Directory of Open Access Journals (Sweden)

    Heiner Iben

    2010-04-01

    Full Text Available Abstract Background Several unicellular organisms (prokaryotes and protozoa can live under permanently anoxic conditions. Although a few metazoans can survive temporarily in the absence of oxygen, it is believed that multi-cellular organisms cannot spend their entire life cycle without free oxygen. Deep seas include some of the most extreme ecosystems on Earth, such as the deep hypersaline anoxic basins of the Mediterranean Sea. These are permanently anoxic systems inhabited by a huge and partly unexplored microbial biodiversity. Results During the last ten years three oceanographic expeditions were conducted to search for the presence of living fauna in the sediments of the deep anoxic hypersaline L'Atalante basin (Mediterranean Sea. We report here that the sediments of the L'Atalante basin are inhabited by three species of the animal phylum Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp. new to science. Using radioactive tracers, biochemical analyses, quantitative X-ray microanalysis and infrared spectroscopy, scanning and transmission electron microscopy observations on ultra-sections, we provide evidence that these organisms are metabolically active and show specific adaptations to the extreme conditions of the deep basin, such as the lack of mitochondria, and a large number of hydrogenosome-like organelles, associated with endosymbiotic prokaryotes. Conclusions This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments. Our findings allow us also to conclude that these metazoans live under anoxic conditions through an obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes. The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen.

  6. Efficacy of acetate-amended biostimulation for uranium sequestration: Combined analysis of sediment/groundwater geochemistry and bacterial community structure

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jie; Veeramani, Harish; Qafoku, Nikolla P.; Singh, Gargi; Riquelme, Maria V.; Pruden, Amy; Kukkadapu, Ravi K.; Gartman, Brandy N.; Hochella, Michael F.

    2017-03-01

    Systematic flow-through column experiments were conducted using sediments and ground water collected from different subsurface localities at the U.S. Department of Energy’s Integrated Field Research Challenge site in Rifle, Colorado. The principal purpose of this study is to gain a better understanding of the interactive effects of groundwater geochemistry, sediment mineralogy, and indigenous bacterial community structures on the efficacy of uranium removal from the groundwater with/without acetate amendment. Overall, we find that the subtle variations in the sediments’ mineralogy, particle size, redox conditions, as well as contents of metal(loid) co-contaminants showed a pronounced effect on the associated bacterial population and composition, which mainly determines the system’s performance with respect to uranium removal. Positive relationship was identified between the abundance of dissimilatory sulfate-reduction genes (i.e., drsA), markers of sulfate-reducing bacteria, and the sediments’ propensity to sequester aqueous uranium. In contrast, no obvious connections were observed between the abundance of common iron-reducing bacteria, e.g., Geobacter spp., and the sediments’ ability to sequester uranium. In the sediments with low bacterial biomass and the absence of sulfate-reducing conditions, abiotic adsorption onto mineral surfaces such as phyllosilicates likely played a relatively major role in the attenuation of aqueous uranium; however, in these scenarios, acetate amendment induced detectable rebounds in the effluent uranium concentrations. The results of this study suggest that reductive immobilization of uranium can be achieved under predominantly sulfate-reducing conditions, and provide insight into the integrated roles of various biogeochemical components in long-term uranium sequestration.

  7. Risk Assessment and Prediction of Heavy Metal Pollution in Groundwater and River Sediment: A Case Study of a Typical Agricultural Irrigation Area in Northeast China.

    Science.gov (United States)

    Zhong, Shuang; Geng, Hui; Zhang, Fengjun; Liu, Zhaoying; Wang, Tianye; Song, Boyu

    2015-01-01

    The areas with typical municipal sewage discharge river and irrigation water function were selected as study sites in northeast China. The samples from groundwater and river sediment in this area were collected for the concentrations and forms of heavy metals (Cr(VI), Cd, As, and Pb) analysis. The risk assessment of heavy metal pollution was conducted based on single-factor pollution index (I) and Nemerow pollution index (NI). The results showed that only one groundwater sampling site reached a polluted level of heavy metals. There was a high potential ecological risk of Cd on the N21-2 sampling site in river sediment. The morphological analysis results of heavy metals in sediment showed that the release of heavy metals can be inferred as one of the main pollution sources of groundwater. In addition, the changes in the concentration and migration scope of As were predicted by using the Groundwater Modeling System (GMS). The predicted results showed that As will migrate downstream in the next decade, and the changing trend of As polluted areas was changed with As content districts because of some pump wells downstream to form groundwater depression cone, which made the solute transfer upstream.

  8. Risk Assessment and Prediction of Heavy Metal Pollution in Groundwater and River Sediment: A Case Study of a Typical Agricultural Irrigation Area in Northeast China

    Directory of Open Access Journals (Sweden)

    Shuang Zhong

    2015-01-01

    Full Text Available The areas with typical municipal sewage discharge river and irrigation water function were selected as study sites in northeast China. The samples from groundwater and river sediment in this area were collected for the concentrations and forms of heavy metals (Cr(VI, Cd, As, and Pb analysis. The risk assessment of heavy metal pollution was conducted based on single-factor pollution index (I and Nemerow pollution index (NI. The results showed that only one groundwater sampling site reached a polluted level of heavy metals. There was a high potential ecological risk of Cd on the N21-2 sampling site in river sediment. The morphological analysis results of heavy metals in sediment showed that the release of heavy metals can be inferred as one of the main pollution sources of groundwater. In addition, the changes in the concentration and migration scope of As were predicted by using the Groundwater Modeling System (GMS. The predicted results showed that As will migrate downstream in the next decade, and the changing trend of As polluted areas was changed with As content districts because of some pump wells downstream to form groundwater depression cone, which made the solute transfer upstream.

  9. In situ Bioreduction of Uranium (VI) in Groundwater and Sediments with Edible Oil as the Electron Donor

    Science.gov (United States)

    Wu, W.; Watson, D. B.; Mehlhorn, T.; Zhang, G.; Earles, J.; Lowe, K.; Phillips, J.; Boyanov, M.; Kemner, K. M.; Schadt, C. W.; Brooks, S. C.; Criddle, C.; Jardine, P.

    2009-12-01

    In situ bioremediation of a uranium-contaminated aquifer was conducted at the US DOE Environmental Remediation Sciences Program (ERSP) Integrated Field Research Challenge (IFRC) site, in Oak Ridge, TN. Edible oil was tested as a slow-release electron donor for microbially mediated U (VI) reduction. Uranium contaminated sediments from the site were used in laboratory microcosm tests to study the feasibility of using this electron donor under anaerobic, ambient temperature conditions. Parallel microcosms were established using ethanol as electron donor for comparison. The tests also examined the impact of sulfate concentrations on U (VI) reduction. The oil was degraded by indigenous microorganisms with acetate as a major product but at a much slower rate than ethanol. The rapid removal of U (VI) from the aqueous phase occurred concurrently with acetate production and sulfate reduction. Initial U(VI) concentration in the aqueous phase increased with increased sulfate concentration (1 vs. 5 mM), likely due to U(VI) desorption from the solid phase, but more U(VI) was reduced with higher initial sulfate level. Finally, the bioreaction in microcosms progressed to methanogenesis. Subsequently, a field test with the edible oil was conducted in a highly permeable gravelly layer (hydraulic conductivity 0.076 cm/sec). Groundwater at the site contained 5-6 μM U; 1.0-1.2 mM sulfate; 3-4 mM Ca; pH 6.8. Diluted emulsified oil (20% solution) was injected into three injection wells within 2 hrs. Geochemical analysis of site groundwater demonstrated the sequential reduction of nitrate, Mn, Fe(III) and sulfate. Transient accumulation of acetate was observed as an intermediate in the oil degradation. Reduction and removal of uranium from groundwater was observed in all wells connected to the injection wells after 2-4 weeks. Uranium concentrations in groundwater were reduced to below 0.126 μM (EPA drinking water standard), at some well locations. Rebound of U in groundwater was

  10. Hydrogeologic framework, arsenic distribution, and groundwater geochemistry of the glacial-sediment aquifer at the Auburn Road landfill superfund site, Londonderry, New Hampshire

    Science.gov (United States)

    Degnan, James R.; Harte, Philip T.

    2013-01-01

    Leachate continues to be generated from landfills at the Auburn Road Landfill Superfund Site in Londonderry, New Hampshire. Impermeable caps on the three landfills at the site inhibit direct infiltration of precipitation; however, high water-table conditions allow groundwater to interact with landfill materials from below, creating leachate and ultimately reducing conditions in downgradient groundwater. Reducing conditions can facilitate arsenic transport by allowing it to stay in solution or by liberating arsenic adsorbed to surfaces and from geologic sources, such as glacial sediments and bedrock. The site occupies a 180-acre parcel of land containing streams, ponds, wetlands, and former gravel pits located in glacial sediment. Four areas, totaling 14 acres, including three landfills and one septage lagoon, were used for waste disposal. The site was closed in 1980 after volatile organic compounds associated with industrial waste dumping were detected. The site was added to the U.S. Environmental Protection Agency National Priority List in 1982, and the landfills were capped in 1996. Although volatile organic compound concentrations in groundwater have declined substantially, some measurable concentrations remain. Temporally variable and persistent elevated arsenic concentrations have been measured in groundwater affected by the landfill leachate. Microbial consumption of carbon found in leachate is a driver of reducing conditions that liberate arsenic at the site. In addition to sources of carbon in landfill leachate, wetland areas throughout the site also could contribute carbon to groundwater, but it is currently unknown if any of the wetland areas have downward or reversing gradients that could allow the infiltration of surface water to groundwater. Red-stained sediments and water indicate iron-rich groundwater discharge to surface water and are also associated with elevated concentrations of arsenic in sediment and groundwater. Ironrich groundwater seeps have

  11. Groundwater interactions with Lobelia lakes- effects on the aquatic plant, Littorella uniflora

    DEFF Research Database (Denmark)

    Ommen, Daniela Oliveira; Vinther, Hanne Fogh; Krüger, Laila

    aquatic plants whose leaves grow in a rosette form and have a large root base. The large root system enables the plants to better assimilate nutrients from the sediments, and the uptake of CO2 which is used for photosynthesis, and to release O2 into otherwise anoxic sediments. Lake Hampen is situated high....... The macrophytes themselves can also affect the biogeochemistry by changing the concentration of the dissolved CO2, O2 and nutrients in the sediment. The main objective of this project is to investigate how plant growth in Lobelia lakes is influenced by the inlet and outlet of groundwater; and which role...... the plants have in the cycling of the nutrients in these lakes. To fulfil these objectives several smaller studies are to be carried out, these include the determination of the groundwater flow pattern, the determination of the Littorella uniflora coverage within the lake and to establish how this coverage...

  12. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    Science.gov (United States)

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Böhlke, J. K.

    2017-01-01

    Nitrate has become an increasingly abundant potential electron acceptor for Fe(II) oxidation in groundwater, but this redox couple has not been well characterized within aquifer settings. To investigate this reaction and some of its implications for redox-sensitive groundwater contaminants, we conducted an in situ field study in a wastewater-contaminated aquifer on Cape Cod. Long-term (15 year) geochemical monitoring within the contaminant plume indicated interacting zones with variable nitrate-, Fe(II)-, phosphate-, As(V)-, and As(III)-containing groundwater. Nitrate and phosphate were derived predominantly from wastewater disposal, whereas Fe(II), As(III), and As(V) were mobilized from the aquifer sediments. Multiple natural gradient, anoxic tracer tests were conducted in which nitrate and bromide were injected into nitrate-free, Fe(II)-containing groundwater. Prior to injection, aqueous Fe(II) concentrations were approximately 175 μM, but sorbed Fe(II) accounted for greater than 90% of the total reactive Fe(II) in the aquifer. Nitrate reduction was stimulated within 1 m of transport for 100 μM and 1000 μM nitrate additions, initially producing stoichiometric quantities of nitrous oxide (>300 μM N). In subsequent injections at the same site, nitrate was reduced even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and were accompanied by Fe(III) oxyhydroxide precipitation and decreases in dissolved phosphate, As(III), and As(V) concentrations. Nitrate N and O isotope fractionation effects during nitrate reduction were approximately equal (ε15N/ε18O = 1.11) and were similar to those reported for laboratory studies of biological nitrate reduction, including denitrification, but unlike some reported effects on nitrate by denitrification in aquifers. All constituents affected by the in situ tracer experiments returned to pre-injection levels after several weeks

  13. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    Science.gov (United States)

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Böhlke, J.K.

    2017-01-01

    Nitrate has become an increasingly abundant potential electron acceptor for Fe(II) oxidation in groundwater, but this redox couple has not been well characterized within aquifer settings. To investigate this reaction and some of its implications for redox-sensitive groundwater contaminants, we conducted an in situ field study in a wastewater-contaminated aquifer on Cape Cod. Long-term (15 year) geochemical monitoring within the contaminant plume indicated interacting zones with variable nitrate-, Fe(II)-, phosphate-, As(V)-, and As(III)-containing groundwater. Nitrate and phosphate were derived predominantly from wastewater disposal, whereas Fe(II), As(III), and As(V) were mobilized from the aquifer sediments. Multiple natural gradient, anoxic tracer tests were conducted in which nitrate and bromide were injected into nitrate-free, Fe(II)-containing groundwater. Prior to injection, aqueous Fe(II) concentrations were approximately 175 μM, but sorbed Fe(II) accounted for greater than 90% of the total reactive Fe(II) in the aquifer. Nitrate reduction was stimulated within 1 m of transport for 100 μM and 1000 μM nitrate additions, initially producing stoichiometric quantities of nitrous oxide (>300 μM N). In subsequent injections at the same site, nitrate was reduced even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and were accompanied by Fe(III) oxyhydroxide precipitation and decreases in dissolved phosphate, As(III), and As(V) concentrations. Nitrate N and O isotope fractionation effects during nitrate reduction were approximately equal (ε15N/ε18O = 1.11) and were similar to those reported for laboratory studies of biological nitrate reduction, including denitrification, but unlike some reported effects on nitrate by denitrification in aquifers. All constituents affected by the in situ tracer experiments returned to pre-injection levels after several

  14. LABORATORY REPORT ON IODINE ({sup 129}I AND {sup 127}I) SPECIATION, TRANSFORMATION AND MOBILITY IN HANFORD GROUNDWATER, SUSPENDED PARTICLES AND SEDIMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, D.; Santschi, P.; Xu, C.; Zhang, S.; Ho, Y.; Li, H.; Schwehr, K.

    2012-09-30

    The Hanford Site in eastern Washington produced plutonium for several decades and in the process generated billions of gallons of radioactive waste. Included in this complex mixture of waste was 50 Ci of iodine-129 ({sup 129}I). Iodine-129’s high abundance, due to its high fission yield, and extreme toxicity result in iodine-129 becoming a key risk driver at many Department of Energy (DOE) sites. The mobility of radioiodine in arid environments, such as the Hanford Site, depends largely on its chemical speciation and is also greatly affected by many other environmental factors, especially natural sediment organic matter (SOM). Groundwater radioiodine speciation has not been measured in arid regions with major plumes or large disposed {sup 129}I inventories, including the Hanford Site, Idaho National Laboratory, and Nevada Test Site. In this study, stable iodine-127 and radioiodine-129 speciation, pH, and dissolved organic carbon (DOC) of groundwater samples collected from seven wells located in the 200-West Area of the Hanford site were investigated. The most striking finding was that iodate (IO{sub 3}{sup -}) was the most abundant species. Unexpectedly, iodide (I{sup -}), which was likely the form of iodine in the source materials and the expected dominant groundwater species based on thermodynamic considerations, only accounted for 1-2% of the total iodine concentration. It is likely that the relatively high pH and the low abundance of sedimentary organic matter (SOM) that is present at the site slowed down or even inhibited the reduction of iodate, as SOM abiotically reduce iodate into iodide. Moreover, a study on the kinetics of iodide and iodate uptake and aqueous speciation transformation by three representative subsurface Hanford sediments was performed over a period of about one month. This study was carried out by using iodide-125 or iodate-125 at the ambient iodine-127concentration found at the site. Iodate K{sub d} values were on average 89% greater

  15. Groundwater and surface-water interaction and effects of pumping in a complex glacial-sediment aquifer, phase 2, east-central Massachusetts

    Science.gov (United States)

    Eggleston, Jack R.; Zarriello, Phillip J.; Carlson, Carl S.

    2015-12-31

    The U.S. Geological Survey, in cooperation with the Town of Framingham, Massachusetts, has investigated the potential of proposed groundwater withdrawals at the Birch Road well site to affect nearby surface water bodies and wetlands, including Lake Cochituate, the Sudbury River, and the Great Meadows National Wildlife Refuge in east-central Massachusetts. In 2012, the U.S. Geological Survey developed a Phase 1 numerical groundwater model of a complex glacial-sediment aquifer to synthesize hydrogeologic information and simulate potential future pumping scenarios. The model was developed with MODFLOW-NWT, an updated version of a standard USGS numerical groundwater flow modeling program that improves solution of unconfined groundwater flow problems. The groundwater model and investigations of the aquifer improved understanding of groundwater–surface-water interaction and the effects of groundwater withdrawals on surface-water bodies and wetlands in the study area. The initial work also revealed a need for additional information and model refinements to better understand this complex aquifer system.

  16. Influence of geology on groundwater-sediment interactions in arsenic enriched tectono-morphic aquifers of the Himalayan Brahmaputra river basin

    Science.gov (United States)

    Verma, Swati; Mukherjee, Abhijit; Mahanta, Chandan; Choudhury, Runti; Mitra, Kaushik

    2016-09-01

    The present study interprets the groundwater solute chemistry, hydrogeochemical evolution, arsenic (As) enrichment and aquifer characterization in Brahmaputra River Basin (BRB) involving three geologically and tectono-morphically distinct regions located in northeastern India. These study regions consist of the northwestern (NW) and the northern (N) region, both located along the western and eastern parts of Eastern Himalayas and the southern (S) region (near Indo-Burmese Range and Naga hills) of the Brahmaputra basin which show distinct tectonic settings and sediment provenances in the Himalayan orogenic belt. Stable isotopic composition (δ2H and δ18O) in groundwater suggests that some evaporation may have taken place through recharging of ground water in the study areas. The major-ion composition shows that groundwater composition of the NW and N parts are between Casbnd HCO3 and Casbnd Nasbnd HCO3 while the S-region is dominated by Nasbnd Casbnd HCO3 hydrochemical facies. The major mineralogical composition of aquifer sediments indicates the dominant presence of iron(Fe)-oxide and oxyhydroxides, mica (muscovite and biotite), feldspar, pyroxene, amphibole, abundance of quartz and clay minerals whereas clay is predominantly present in sediments of S-aquifers. These mafic minerals, aluminosilicates and clay minerals might offer available reactive surface for As-adsorption and co-precipitatation with amorphous Fe. These associated adsorbed and co-precipitated As might be released due to reductive dissolution of Fe-oxide and oxyhydroxides in groundwater. These minerals are assumed to be possible sources of As in groundwater. The stability diagrams of groundwater data suggest that solute might have been introduced into groundwater from weathering of K-feldspar, plagioclase, pyroxene of Himalayan rocks, the Siwalik Group and Eastern Syntaxes in NW and N-regions. However, basic cations might be derived from weathering of K-feldspar, plagioclase, pyroxene and olivine

  17. Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio-temporal variability of groundwater discharge in soft-bedded streams

    DEFF Research Database (Denmark)

    Sebök, Éva; Calvache, Carlos Duque; Engesgaard, Peter Knudegaard;

    2015-01-01

    -induced temperature anomalies resemble the signal of groundwater discharge while scouring will cause the cable to float in the water column and measure stream water temperatures. DTS applied in a looped layout with nine fibre optic cable rows in a 70 × 5 m section of a soft-bedded stream made it possible to detect......The delineation of groundwater discharge areas based on Distributed Temperature Sensing (DTS) data of the streambed can be difficult in soft-bedded streams where sedimentation and scouring processes constantly change the position of the fibre optic cable relative to the streambed. Deposition...... on the simultaneous interpretation of streambed temperature and elevation data, a method is proposed to delineate potential high-groundwater discharge areas and identify deposition-induced temperature anomalies in soft-bedded streams. Potential high-discharge sites were detected using as metrics the daily minimum...

  18. Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores

    Science.gov (United States)

    Sheibley, R.W.; Duff, J.H.; Jackman, A.P.; Triska, F.J.

    2003-01-01

    Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater-stream water mixing within sediment cores, which provided a well-defined one-dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic-anaerobic interface. Ammonium (NH4+) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO3-) equaling ???25% of the NH4+ loss was produced in the upper sediments. The NH4+ and NO3- profiles in the uppermost sediments resulted from coupled nitrification-denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42-209 and 53-160 mg N m-2 day-1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River.

  19. 碱性缺氧环境下地下水中苯和甲苯的生物降解%BIODEGRADATION OF BENZENE AND TOLUENE IN GROUNDWATER UNDER AN ALKALINE AND ANOXIC CONDITION

    Institute of Scientific and Technical Information of China (English)

    刘玉龙; 陈亮; 刘菲; 刘光全

    2012-01-01

    Three predominated classes of microbes,B-bacteria,T-bacteria and M-bacteria,were inoculated from soils which were collected from a vadose zone chronically contaminated by cruel oil,fed with benzene and toluene and cultured without extra nutrients and electron acceptors under anoxic conditions.Laboratory batch studies were performed to assess the potential for biodegradation of benzene and toluene at high pH levels.The results showed that the degradation processes fit zero-order kinetics equations well and the rate constants ranged from 0.22 to 0.68 mg/(L·d).The rates of benzene and toluene biodegradation by the three cultures decreased variously when increasing the initial pH values from 8.7 to 9.6 and 10.6,respectively.The rates of benzene biodegradation by B-bacteria were reduced by less than 10%;the rates of toluene biodegradation by T-bacteria were decreased from 16.22% at the initial pH 9.6 to 41.23% at the initial pH 10.6;and the rates of benzene and toluene biodegradation by M-bacteria were decreased from about 30% at the initial pH 9.6 to about 45% at the initial pH 10.6.Benzene and toluene could be thoroughly biodegraded even at pH 10.6.It is recommended that no extra pH buffer zone between an Fe0-PRB and a bio-wall should be necessary for designing sequential PRBs to treat such pollutants in aquifers.%在缺氧环境下,不额外加入电子受体和营养盐,从长期受原油污染的包气带介质中分离、培养驯化得到了降解苯或甲苯的3种优势菌群:B-bacteria、T-bacteria和M-bacteria,采用批试验方法研究了高pH环境下3种菌群降解苯和甲苯的速率。结果表明:苯和甲苯的降解符合零级反应动力学,速率常数在0.22~0.68 mg/(L.d)。初始pH从8.7升高到9.6和10.6时,B-bacteria降解苯的速率降低都在10%以内;T-bacteria降解甲苯的速率降低率从pH9.6时的16.22%剧增到pH10.6时的41.23%;而M-bacteria降解苯和甲苯的速率降低从pH9.6时的30%左右增到pH10.6

  20. Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes

    Science.gov (United States)

    Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

    2013-01-01

    Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry.

  1. Experimental study of sediment-CO2 reactions with application to changes in groundwater quality due to leakage of sequestered CO2

    Science.gov (United States)

    Carey, J. W.; Williams, M. R.; Hakala, A.; Fessenden, J. E.; Keating, E. H.

    2009-12-01

    Geologic sequestration of CO2 requires storage of buoyant, immiscible supercritical CO2 in the subsurface for long periods of time. In the viability assessment of sequestration, one of the most significant risk concerns is damage of shallow drinking water aquifers from potential CO2 leakage. The groundwater quality concerns are primarily due to acidification, increase in total dissolved solids (TDS), and the potential mobilization of hazardous trace metals. Previous studies of this issue include natural analogs of CO2-groundwater interactions where there can be uncertainty as to whether observations reflect variations in groundwater quality unrelated to CO2 and numerical studies of CO2-brine interactions with shallow aquifers where there is uncertainty as to the geochemical mechanisms of trace element mobilization. In this study, we conduct experiments of CO2-water-sediment interactions from the Chimayo region in north-central New Mexico. This region includes a natural CO2 seep which we have used in natural analog studies (Keating et al. 2009) and the presence of elevated arsenic and uranium concentrations. The experiments were designed to address the question of whether CO2 reactions with aquifer sediments could account for the observed water quality problems in Chimayo and to consider the more general question of the nature of trace element mobilization by CO2-induced reactions. The experiments consisted of periodically sampled batch reactions of water and sediment reacted with a continuous source of 1-atm CO2. The sediments are quartz-rich alluvial fan deposits that include feldspars and clays and were characterized by XRD, XRF, and by sequential extraction to determine trace metal content. The water was created to represent the background major ion chemistry of groundwater in the region. The sediments were initially equilibrated with the synthetic water prior to introduction of CO2. Reaction with CO2 was monitored over 10 days with periodic fluid sampling. The

  2. Decoupling of the Carbon Cycle during Ocean Anoxic Event-2

    Science.gov (United States)

    Eldrett, J.; Bergman, S. C.; Minisini, D.

    2013-12-01

    The Cenomanian to Turonian Boundary transition (95-93 Ma) represents one of the most profound global perturbations in the carbon cycle of the last 140 million years. This interval is characterized by widespread deposition of organic-rich fine-grained sediment marked by a globally recognised positive carbon isotope excursion (CIE) reflecting the widespread removal of 12C-enriched organic matter in marine sediments under global anoxic conditions. However, the exact timing and trigger of this inferred global phenomenon, termed Oceanic Anoxic Event-2 is still debated, with recent studies showing diachroneity between the deposition of the organic-rich sediment and the CIE, and conflicting interpretations on detailed redox analyses in several of these inferred anoxic settings. Here we present the first evidence for widespread and persistent oxygenation during OAE-2 based primarily on the distribution of redox-sensitive trace metals preserved in sediments from the Eagle Ford Formation, Western Interior Seaway of North America. We generated a δ13C curve which indicates an earlier initiation of the CIE in Texas compared to the Global Stratotype and Point Section at Pueblo, Colorado. Our data also indicate anoxic-euxinic conditions in the mid-late Cenomanian, but improved bottom-water oxygenation prior to and during the CIE, corroborated by increased bioturbation, abundance of benthic foraminifera and reduced total organic carbon values. Trace metal enrichments support large volumes of mafic volcanism possibly from the High Arctic Large Igneous Province (LIP), which occur during peak bottom-water oxygenation and a plateau in δ13Corg values and does not immediately precede the Cenomanian-Turonian CIE, as previously stated. This suggests that the emplacement of a LIP was not the primary trigger of the OAE-2 event. It is also unlikely that bottom-water oxygenation was promoted by the introduction of volcanogenic Fe inhibiting sulfate reduction, as the depletion in redox

  3. Anoxic media design, preparation and considerations

    NARCIS (Netherlands)

    Plugge, C.M.

    2005-01-01

    Exclusion of oxygen from growth media is essential for the growth of anoxic prokaryotes. In general, anaerobic techniques focus on the use of deaerated boiled growth media. Successful enrichment, isolation, and cultivation of anoxic prokaryotes critically depend on the choice of appropriate growth m

  4. Remediation of the Highland Drive South Ravine, Port Hope, Ontario: Contaminated Groundwater Discharge Management Using Permeable Reactive Barriers and Contaminated Sediment Removal - 13447

    Energy Technology Data Exchange (ETDEWEB)

    Smyth, David; Roos, Gillian [Golder Associates Ltd., 2390 Argentia Road, Mississauga, ON L5N 5Z7 (Canada); Ferguson Jones, Andrea [MMM Group Ltd., 100 Commerce Valley Drive West, Thornhill, ON L3T 0A1 (Canada); Case, Glenn [AECL Port Hope Area Initiative Management Office, 115 Toronto Road, Port Hope, ON L1A 3S4 (Canada); Yule, Adam [Public Works and Government Services Canada, 4900 Yonge Street, 11th Floor, Toronto, ON, M2N 6A6 (Canada)

    2013-07-01

    The Highland Drive South Ravine (HDSR) is the discharge area for groundwater originating from the Highland Drive Landfill, the Pine Street North Extension (PSNE) roadbed parts of the Highland Drive roadbed and the PSNE Consolidation Site that contain historical low-level radioactive waste (LLRW). The contaminant plume from these LLRW sites contains elevated concentrations of uranium and arsenic and discharges with groundwater to shallow soils in a wet discharge area within the ravine, and directly to Hunt's Pond and Highland Drive South Creek, which are immediately to the south of the wet discharge area. Remediation and environmental management plans for HDSR have been developed within the framework of the Port Hope Project and the Port Hope Area Initiative. The LLRW sites will be fully remediated by excavation and relocation to a new Long-Term Waste Management Facility (LTWMF) as part of the Port Hope Project. It is projected, however, that the groundwater contaminant plume between the remediated LLRW sites and HDSR will persist for several hundreds of years. At the HDSR, sediment remediation within Hunt's Ponds and Highland Drive South Creek, excavation of the existing and placement of clean fill will be undertaken to remove current accumulations of solid-phase uranium and arsenic associated with the upper 0.75 m of soil in the wet discharge area, and permeable reactive barriers (PRBs) will be used for in situ treatment of contaminated groundwater to prevent the ongoing discharge of uranium and arsenic to the area in HDSR where shallow soil excavation and replacement has been undertaken. Bench-scale testing using groundwater from HDSR has confirmed excellent treatment characteristics for both uranium and arsenic using permeable reactive mixtures containing granular zero-valent iron (ZVI). A sequence of three PRBs containing ZVI and sand in backfilled trenches has been designed to intercept the groundwater flow system prior to its discharge to the ground

  5. Functional Microbial Diversity Explains Groundwater Chemistry in a Pristine Aquifer

    Science.gov (United States)

    Microbial communities inhabiting anoxic aquifers catalyze critical biogeochemical reactions in the subsurface, yet little is known about how their community structure correlates with groundwater chemistry. In this study, we described the composition of microbial communities in th...

  6. Formation and Control of Self-Sealing High Permeability Groundwater Mounds in Impermeable Sediment: Implications for SUDS and Sustainable Pressure Mound Management

    Directory of Open Access Journals (Sweden)

    David D. J. Antia

    2009-10-01

    Full Text Available A groundwater mound (or pressure mound is defined as a volume of fluid dominated by viscous flow contained within a sediment volume where the dominant fluid flow is by Knudsen Diffusion. High permeability self-sealing groundwater mounds can be created as part of a sustainable urban drainage scheme (SUDS using infiltration devices. This study considers how they form, and models their expansion and growth as a function of infiltration device recharge. The mounds grow through lateral macropore propagation within a Dupuit envelope. Excess pressure relief is through propagating vertical surge shafts. These surge shafts can, when they intersect the ground surface result, in high volume overland flow. The study considers that the creation of self-sealing groundwater mounds in matrix supported (clayey sediments (intrinsic permeability = 10–8 to 10–30 m3 m–2 s–1 Pa–1 is a low cost, sustainable method which can be used to dispose of large volumes of storm runoff (<20→2,000 m3/24 hr storm/infiltration device and raise groundwater levels. However, the inappropriate location of pressure mounds can result in repeated seepage and ephemeral spring formation associated with substantial volumes of uncontrolled overland flow. The flow rate and flood volume associated with each overland flow event may be substantially larger than the associated recharge to the pressure mound. In some instances, the volume discharged as overland flow in a few hours may exceed the total storm water recharge to the groundwater mound over the previous three weeks. Macropore modeling is used within the context of a pressure mound poro-elastic fluid expulsion model in order to analyze this phenomena and determine (i how this phenomena can be used to extract large volumes of stored filtered storm water (at high flow rates from within a self-sealing high permeability pressure mound and (ii how self-sealing pressure mounds (created using storm water infiltration can be used to

  7. Determining the sources of suspended sediment in a Mediterranean groundwater-dominated river: the Na Borges basin (Mallorca, Spain).

    Science.gov (United States)

    Estrany, Joan; Martinez-Carreras, Nuria

    2013-04-01

    Tracers have been acknowledged as a useful tool to identify sediment sources, based upon a variety of techniques and chemical and physical sediment properties. Sediment fingerprinting supports the notion that changes in sedimentation rates are not just related to increased/reduced erosion and transport in the same areas, but also to the establishment of different pathways increasing sediment connectivity. The Na Borges is a Mediterranean lowland agricultural river basin (319 km2) where traditional soil and water conservation practices have been applied over millennia to provide effective protection of cultivated land. During the twentieth century, industrialisation and pressure from tourism activities have increased urbanised surfaces, which have impacts on the processes that control streamflow. Within this context, source material sampling was focused in Na Borges on obtaining representative samples from potential sediment sources (comprised topsoil; i.e., 0-2 cm) susceptible to mobilisation by water and subsequent routing to the river channel network, while those representing channel bank sources were collected from actively eroding channel margins and ditches. Samples of road dust and of solids from sewage treatment plants were also collected. During two hydrological years (2004-2006), representative suspended sediment samples for use in source fingerprinting studies were collected at four flow gauging stations and at eight secondary sampling points using time-integrating sampling samplers. Likewise, representative bed-channel sediment samples were obtained using the resuspension approach at eight sampling points in the main stem of the Na Borges River. These deposits represent the fine sediment temporarily stored in the bed-channel and were also used for tracing source contributions. A total of 102 individual time-integrated sediment samples, 40 bulk samples and 48 bed-sediment samples were collected. Upon return to the laboratory, source material samples were

  8. Extreme seawater compositions during Oceanic Anoxic Events

    Science.gov (United States)

    Cohen, A.; Bottini, C.; Dickson, A. J.; Izon, G. J.; Coe, A. L.

    2012-12-01

    For almost the entire duration of the Phanerozoic, the oceans have remained well oxygenated and highly conducive to the development of animal and plant life. However, there have been relatively brief intervals, known as Oceanic Anoxic Events (OAEs), when a very significant expansion of low-oxygen regions occurred throughout the world's oceans. OAEs were characterised by highly atypical seawater chemistry, as reflected in the chemical and isotopic compositions of contemporaneous sediments and fossil remains. These oxygen-deficient intervals also exerted profound pressures on many marine species as indicated by major changes in species populations and distributions. High-resolution chemical and isotopic data recovered from marine sediments and sedimentary rocks, together with biotic information, provide us with the best means of understanding the significance of OAEs and their place in the evolution of the Earth system. We present new Mo- and Os-isotope and geochemical data from OAE 1a (early Cretaceous), which help define how this event evolved in relation to the other major environmental parameters - including global warming, continental weathering and Ontong-Java volcanism - of that time. We compare these new observations with published results from other Mesozoic OAEs and the PETM. Recently published Os-isotope data from DSDP site 463 (mid-Pacific) [1] and northern Italy [1, 2] show that the Os budget of the oceans was dominated for a period of c. 880 ka during OAE 1a by the hydrothermal flux of unradiogenic Os from the Ontong-Java province. The observation of identical Os-isotope compositions at these two very distant sites indicates that seawater was well mixed at that time. Over the same interval, the seawater Mo-isotope composition, based upon well-preserved samples from Italy, was persistently atypical, with δ98/95Mo ranging between -0.7 and +0.7 permil [3]. All the samples analysed here accumulated under highly anoxic conditions and contain highly abundant

  9. Colloidal activated carbon for in-situ groundwater remediation--Transport characteristics and adsorption of organic compounds in water-saturated sediment columns.

    Science.gov (United States)

    Georgi, Anett; Schierz, Ariette; Mackenzie, Katrin; Kopinke, Frank-Dieter

    2015-08-01

    Colloidal activated carbon can be considered as a versatile adsorbent and carrier material for in-situ groundwater remediation. In analogy to other nanoremediation approaches, activated carbon colloids (ACC) can be injected into the subsurface as aqueous suspensions. Deposition of ACC on the sediment creates a sorption barrier against further spreading of hydrophobic pollutants. This study deals with the optimization of ACC and their suspensions with a focus on suspension stability, ACC mobility in saturated porous media and sorption efficiency towards organic contaminants. ACC with an appropriate particle size range (d50=0.8μm) were obtained from a commercial powdered activated carbon product by means of wet-grinding. Among the various methods tested for stabilization of ACC suspensions, addition of humic acid (HA) and carboxymethyl cellulose (CMC) showed the best results. Due to electrosteric stabilization by adsorption of CMC, suspensions remained stable even at high ACC concentrations (11gL(-1)) and conditions typical of very hard water (5mM divalent cations). Furthermore, CMC-stabilized ACC showed high mobility in a water-saturated sandy sediment column (filter coefficient λ=0.2m(-1)). Such mobility is a pre-requisite for in-situ installation of sorption or reaction barriers by simple injection-well or direct-push application of ACC suspensions. Column experiments with organic model compounds proved the efficacy of ACC deposits on sediment for contaminant adsorption and retardation under flow-through conditions.

  10. Results of soil, ground-water, surface-water, and streambed-sediment sampling at Air Force Plane 85, Columbus, Ohio, 1996

    Science.gov (United States)

    Parnell, J.M.

    1997-01-01

    The U.S. Geological Survey (USGS), in cooperation with Aeronautical Systems Center, Environmental Management Directorate, Restoration Division, prepared the Surface- and Ground- Water Monitoring Work Plan for Air Force Plant 85 (AFP 85 or Plant), Columbus, Ohio, under the Air Force Installation Restoration Program to characterize any ground-water, surface-water, and soil contamination that may exist at AFP 85. The USGS began the study in November 1996. The Plant was divided into nine sampling areas, which included some previously investi gated study sites. The investigation activities included the collection and presentation of data taken during drilling and water-quality sampling. Data collection focused on the saturated and unsatur ated zones and surface water. Twenty-three soil borings were completed. Ten monitoring wells (six existing wells and four newly constructed monitoring wells) were selected for water-quality sam pling. Surface-water and streambed-sediment sampling locations were chosen to monitor flow onto and off of the Plant. Seven sites were sampled for both surface-water and streambed-sediment quality. This report presents data on the selected inorganic and organic constituents in soil, ground water, surface water, and streambed sediments at AFP 85. The methods of data collection and anal ysis also are included. Knowledge of the geologic and hydrologic setting could aid Aeronautical Systems Center, Environmental Management Directorate, Restoration Division, and its governing regulatory agencies in future remediation studies.

  11. Reconnaissance investigations of potential ground-water and sediment contamination at three former underground storage tank locations, Fort Jackson, South Carolina, 1994

    Science.gov (United States)

    Robertson, J.F.; Nagle, Douglas D.; Rhodes, Liesl C.

    1994-01-01

    Investigations to provide initial qualitative delineation of petroleum hydrocarbon contamination at three former underground storage tank locations at Fort Jackson, South Carolina, were made during March 1994. Ground-water and sediment samples were collected using direct-push technology and analyzed on-site with a gas chromatograph, which provided real-time, semi-quantitative data. In addition, ground-water and sediment samples were collected at selected sites for laboratory analyses to provide a confirmation of the on-site data. These analyses provided qualitative data on the lateral distri- bution of petroleum hydrocarbons. Petroleum hydrocarbons were detected by on-site analysis in ground-water samples from nine locations at Site 1062, suggesting the presence of a contaminant plume. Concentrations ranged from less than the minimum detection limit to 4,511 mg/L (micrograms per liter) for benzene, 15,594 mg/L for toluene, 16,501 mg/L for ethylbenzene, and 19,391 mg/L for total xylenes. Concentrations of Total Petroleum Hydrocarbons-Gasoline Range Organics ranged from 323 mg/L to 3,364 mg/L; Total Petroleum Hydrocarbons-Diesel Range Organics were not detected. Three samples from this site were analyzed for benzene, toluene, ethylbenzene, and total xylenes at a laboratory and results showed concentrations ranging from less than the minimum detection limit to 1,070 mg/L for benzene, 7,930 mg/L for toluene, 6,890 mg/L for ethylbenzene, and 1,524 mg/L for total xylenes. Petroleum hydro- carbons were detected by on-site analysis in only one sample at Site 2438. A concentration of 131,000 micrograms per kilogram Total Petroleum Hydrocarbons-Diesel Range Organics was detected in sample number GP-2-4-13.5. Petroleum hydrocarbons were detected by on-site analysis in only one ground-water sample from Site 2444. A concentration of 3,145 mg/L Total Petroleum Hydrocarbons-Gasoline Range Organics was detected at sampling location GP-3-2.

  12. Valanginian Weissert oceanic anoxic event

    Science.gov (United States)

    Erba, Elisabetta; Bartolini, Annachiara; Larson, Roger L.

    2004-02-01

    Biotic changes in nannofossils and radiolarians associated with the Valanginian δ13C anomaly are documented at Ocean Drilling Program Hole 1149B in the Pacific Ocean: they are coeval and similar to those previously documented in the Tethys, suggesting a global perturbation of marine ecosystems. A marked increase in abundance of Diazomatolithus, absence of nannoconids, and a Pantanellium peak characterize the Valanginian δ13C excursion. Such changes are interpreted as being due to global enhanced fertility and a biocalcification crisis under conditions of excess CO2. The occurrence of organic C rich black shales in the Southern Alps and in the Pacific in the interval corresponding to the δ13C excursion suggests a Valanginian oceanic anoxic event (OAE). Volcanism of the Paranà-Etendeka large igneous province (ca. 132 Ma) was presumably responsible for an increase of CO2, triggering a climate change and accelerated hydrological cycling, possibly causing an indirect fertilization of the oceans. Widespread nutrification via introduction of biolimiting metals at spreading ridges could have significantly increased during the Gondwana breakup and simultaneous tectonic events in three separate oceans. There is no paleontological or δ18O evidence of warming during the Valanginian OAE. On the contrary, both nannofossils and oxygen isotopes record a cooling event at the climax of the δ13C excursion. Weathering of basalts and burial of organic C rich black shales were presumably responsible for CO2 drawdown and establishment of reversed greenhouse conditions.

  13. Cable Bacteria in Freshwater Sediments

    OpenAIRE

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus B.; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the fre...

  14. Groundwater dating for understanding nitrogen in groundwater systems - Time lag, fate, and detailed flow path ways

    Science.gov (United States)

    Morgenstern, Uwe; Hadfield, John; Stenger, Roland

    2014-05-01

    Nitrate contamination of groundwater is a problem world-wide. Nitrate from land use activities can leach out of the root zone of the crop into the deeper part of the unsaturated zone and ultimately contaminate the underlying groundwater resources. Nitrate travels with the groundwater and then discharges into surface water causing eutrophication of surface water bodies. To understand the source, fate, and future nitrogen loads to ground and surface water bodies, detailed knowledge of the groundwater flow dynamics is essential. Groundwater sampled at monitoring wells or discharges may not yet be in equilibrium with current land use intensity due to the time lag between leaching out of the root zone and arrival at the sampling location. Anoxic groundwater zones can act as nitrate sinks through microbial denitrification. However, the effect of denitrification on overall nitrate fluxes depends on the fraction of the groundwater flowing through such zones. We will show results from volcanic aquifers in the central North Island of New Zealand where age tracers clearly indicate that the groundwater discharges into large sensitive lakes like Lake Taupo and Lake Rotorua are not yet fully realising current land use intensity. The majority of the water discharging into these lakes is decades and up to over hundred years old. Therefore, increases in dairy farming over the last decades are not yet reflected in these old water discharges, but over time these increased nitrate inputs will eventually work their way through the large groundwater systems and increasing N loads to the lakes are to be expected. Anoxic zones are present in some of these aquifers, indicating some denitrification potential, however, age tracer results from nested piezo wells show young groundwater in oxic zones indicating active flow in these zones, while anoxic zones tend to have older water indicating poorer hydraulic conductivity in these zones. Consequently, to evaluate the effect of denitrification

  15. Enhanced detection of groundwater contamination from a leaking waste disposal site by microbial community profiles

    Science.gov (United States)

    Mouser, Paula J.; Rizzo, Donna M.; Druschel, Gregory K.; Morales, Sergio E.; Hayden, Nancy; O'Grady, Patrick; Stevens, Lori

    2010-12-01

    Groundwater biogeochemistry is adversely impacted when municipal solid waste leachate, rich in nutrients and anthropogenic compounds, percolates into the subsurface from leaking landfills. Detecting leachate contamination using statistical techniques is challenging because well strategies or analytical techniques may be insufficient for detecting low levels of groundwater contamination. We sampled profiles of the microbial community from monitoring wells surrounding a leaking landfill using terminal restriction fragment length polymorphism (T-RFLP) targeting the 16S rRNA gene. Results show in situ monitoring of bacteria, archaea, and the family Geobacteraceae improves characterization of groundwater quality. Bacterial T-RFLP profiles showed shifts correlated to known gradients of leachate and effectively detected changes along plume fringes that were not detected using hydrochemical data. Experimental sediment microcosms exposed to leachate-contaminated groundwater revealed a shift from a β-Proteobacteria and Actinobacteria dominated community to one dominated by Firmicutes and δ-Proteobacteria. This shift is consistent with the transition from oxic conditions to an anoxic, iron-reducing environment as a result of landfill leachate-derived contaminants and associated redox conditions. We suggest microbial communities are more sensitive than hydrochemistry data for characterizing low levels of groundwater contamination and thus provide a novel source of information for optimizing detection and long-term monitoring strategies at landfill sites.

  16. Total Reducing Capacity in Aquifer Minerals and Sediments: Quantifying the Potential to Attenuate Cr(VI) in Groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Sisman, S. Lara [Univ. of Virginia, Charlottesville, VA (United States); Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-20

    Hexavalent chromium, Cr(VI), is present in the environment as a byproduct of industrial processes. Due to its mobility and toxicity, it is crucial to attenuate or remove Cr(VI) from the environment. The objective of this investigation was to quantify potential natural attenuation, or reduction capacity, of reactive minerals and aquifer sediments. Samples of reduced-iron containing minerals such as ilmenite, as well as Puye Formation sediments representing a contaminated aquifer in New Mexico, were reacted with chromate. The change in Cr(VI) during the reaction was used to calculate reduction capacity. This study found that minerals that contain reduced iron, such as ilmenite, have high reducing capacities. The data indicated that sample history may impact reduction capacity tests due to surface passivation. Further, this investigation identified areas for future research including: a) refining the relationships between iron content, magnetic susceptibility and reduction capacity, and b) long term kinetic testing using fresh aquifer sediments.

  17. Photochemical synthesis of biomolecules under anoxic conditions

    Science.gov (United States)

    Folsome, C.; Brittain, A.; Zelko, M.

    1983-01-01

    The long-wavelength UV anoxic photosynthesis of uracil, various sugars (including deoxyribose and glycoaldehyde), amino acids, and other organic photoproducts is reported. The reactions were conducted in a mixture of water, calcium carbonate, hydrazine, and formaldehyde which were subjected to 24 hr or 72 hr radiation. Product yields were greatest when the hydrazine/formaldehyde ratio was one, and when the reactant concentrations were low. These data suggest that organic products can be formed in variety from those amounts of formaldehyde and hydazine precursors which are themselves formed under anoxic UV photochemical conditions.

  18. An open ocean record of the Toarcian oceanic anoxic event

    Directory of Open Access Journals (Sweden)

    D. R. Gröcke

    2011-11-01

    Full Text Available Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰ negative (organic carbon isotope excursion (CIE which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE. If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰ negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰ is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric.

  19. Energetic Constraints on H-2-Dependent Terminal Electron Accepting Processes in Anoxic Environments

    DEFF Research Database (Denmark)

    Heimann, Axel Colin; Jakobsen, Rasmus; Blodau, C.

    2010-01-01

    Microbially mediated terminal electron accepting processes (TEAPs) to a large extent control the fate of redox reactive elements and associated reactions in anoxic soils, sediments, and aquifers. This review focuses on thermodynamic controls and regulation of H-2-dependent TEAPs, case studies...... illustrating this concept and the quantitative description of thermodynamic controls in modeling. Other electron transfer processes are considered where appropriate. The work reviewed shows that thermodynamics and microbial kinetics are connected near thermodynamic equilibrium. Free energy thresholds...

  20. Stimulated anoxic biodegradation of aromatic hydrocarbons using Fe(III) ligands

    Science.gov (United States)

    Lovley, D.R.; Woodward, J.C.; Chapelle, F.H.

    1994-01-01

    Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contaminated aquifers.Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing

  1. Chemical and physical speciation of mercury in Offatts Bayou: A seasonally anoxic bayou in Galveston Bay

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seunghee; Lehman, Ronald D.; Choe, Key-Young; Gill, Gary A.

    2007-07-01

    A chemical equilibrium model was used to predict the solution speciation of dissolved mercury (Hg) in the stratified water column of Offatts Bayou, a subestuary in Galveston Bay, Texas, which undergoes seasonal anoxia in bottom waters. Chemical equilibrium modeling was conducted using conditional stability constants and concentrations of Hg-complexing organic ligands experimentally determined by competitive ligand equilibration methods. Dissolved Hg complexation was dominated by interactions with sulfide and dissolved organic matter (DOM) (HOHgHS0, HOHgHS(DOM), HgSHS2, and HgS 2{ 2 ) at all depths. Sulfide and glutathione competed for methylmercury (MeHg) complexation in oxic layers; in anoxic waters, sulfide complexation dominated MeHg speciation. The particle–water distribution coefficient (Kd) of Hg decreased in the anoxic layer of the water column, where the dissolved sulfide concentration increased, providing evidence that sulfide complexation influences the solubility of Hg. The solubility of MeHg was elevated in the anoxic as compared to the oxic layers, and this distributional feature was coincident with a change in the solution speciation of dissolved MeHg from glutathione/sulfide complexation in the oxic layers to a predominantly sulfide complexation in the anoxic layers. Maximum enrichment of Hg, MeHg, and iron (Fe) in suspended particulate matter was observed in the lower layer of the pycnocline, most likely resulting from formation of insoluble Fe oxide, which scavenged dissolved Hg sulfide and MeHg-sulfide species. The concomitant decrease in dissolved inorganic Hg, Fe, and sulfide in the anoxic layers is suggested to result from scavenging of inorganic Hg by FeS, which is in accordance with the Hg speciation model. Overall, Hg cycling in the water column of Offatts Bayou was associated with sulfide and DOM complexation, Fe dissolution/precipitation, water column production of MeHg, and/or efflux of MeHg from anoxic sediment.

  2. Anoxic or aerial survival of bivalves and other euryoxic invertebrates as a useful response to environmental stress - A comprehensive review

    NARCIS (Netherlands)

    De Zwaan, A.; Eertman, R.H.M.

    1996-01-01

    Laboratory and field studies have demonstrated the applicability of anoxic/aerial survival as an early warning indicator of contaminant induced stress. The effects of xenobiotics, including heavy metals, organometals and organics as well as contaminated field sediments have been investigated. The us

  3. Enhanced N2-fixation and NH4+ recycling during oceanic anoxic event 2 in the proto-North Atlantic

    NARCIS (Netherlands)

    Ruvalcaba Baroni, I.; Tsandev, I.; Slomp, C.P.

    2014-01-01

    Evidence from sediment core records and model studies suggests that increased nutrient supply played a key role in the initiation of the Cenomanian-Turonian oceanic anoxic event 2 (OAE2; 94 Ma). However, the relative roles of nitrogen (N) and phosphorus (P) availability in controlling primary produc

  4. Annual report of 1995 groundwater monitoring data for the Kerr Hollow Quarry and Chestnut Ridge Sediment Disposal Basin, Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-02-01

    The Kerr Hollow Quarry (KHQ) and the Chestnut Ridge Sediment Disposal Basin (CRSDB) are inactive waste management sites located at the Oak Ridge Y-12 Plant. The KHQ and CRSDB are regulated as treatment, storage, or disposal (TSD) facilities under the Resource Conservation and Recovery Act (RCRA). The facilities were granted interim status in calendar year (CY) 1986 under Tennessee Department of Environment and Conservation (TDEC) Hazardous Waste Management Rule 1200-1-11-.05. Historical environmental monitoring data and baseline characterization under interim status indicated that releases of contaminants to groundwater had not occurred; thus, the detection monitoring was implemented at the sites until either clean closure was completed or post-closure permits were issued. The CRSDB was closed in Cy 1989 under a TDEC-approved RCRA closure plan. A revised RCRA PCPA for the CRSDB was submitted by DOE personnel to TDEC staff in September 1994. A final post-closure permit was issued by the TDEC on September 18, 1995. Closure activities at KHQ under RCRA were completed in October 1993. The Record of Decision will also incorporate requirements of the RCRA post-closure permit once it is issued by the TDEC.

  5. An open marine record of the Toarcian oceanic anoxic event

    Directory of Open Access Journals (Sweden)

    D. R. Gröcke

    2011-04-01

    Full Text Available Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic-rich sediments (black shales and significant perturbations in the global carbon cycle. The expression of these perturbations is globally recorded in sediments as excursions in the carbon isotope record irrespective of lithology or depositional environment. During the Early Toarcian, black shales were deposited on the epi- and peri-continental shelves of Pangaea and these sedimentary rocks are associated with a pronounced (ca. 7‰ negative (organic carbon isotope excursion (CIE which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the Early Toarcian is thought to represent an oceanic anoxic event (the T-OAE. Associated with this event, there were pronounced perturbations in global weathering rates and seawater temperatures. Although it is commonly asserted that the T-OAE is a global event and that the distribution of black shales is likewise global, an isotopic and/or organic-rich expression of this event has as yet only been recognized on epi- and peri-continental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of Early Toarcian cherts from Japan that were deposited in the open Panthalassa Ocean was analysed. The results show the presence of a major (>6‰ negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the Early Toarcian negative CIE known from European epicontinental strata. Furthermore, a secondary ca. −2‰ excursion in δ13Corg is also recognized lower in the studied succession that, within the current biostratigraphical resolution, is likely to represent the excursion that occurs close to the Pliensbachian/Toarcian boundary and which is also recorded in European epicontinental successions

  6. Cr Isotope Response to Ocean Anoxic Event 2

    Science.gov (United States)

    Holmden, C. E.; Jacobson, A. D.; Sageman, B. B.; Hurtgen, M.

    2015-12-01

    The element Cr offers a redox sensitive isotopic proxy with potential for tracing past oxygen levels in the oceans. We examine this potential in a marine carbonate section deposited during Cretaceous Ocean Anoxic Event 2 (OAE 2) in the Western Interior Seaway, Colorado. Redox changes are the main source of Cr isotope fractionation in Earth surface environments. Cr(VI), in the form of the chromate oxyanion, is the thermodynamically favoured species in oxygenated seawater. Reduction of Cr(VI) causes light isotopes to partition into Cr(III), which is reactive and susceptible to removal into marine sediment. Therefore, widespread ocean anoxia should correlate with positive shifts in seawater chromate Cr isotope values (δ53Cr), assuming that all Cr input fluxes remained constant during the event. We find instead that inferred seawater δ53Cr values decreased during OAE 2. The minima of the sedimentary δ53Cr excursion coincides with the peak interval of anomalously enriched concentrations of Cr and other trace metals of basaltic affinity attributed to eruption of the Caribbean Large Igneous Province (CLIP). We propose that an anoxic, hydrothermal plume enriched in Cr(III) with low δ53Cr values characteristic of igneous rocks moved from deep waters of the CLIP eruption site in the eastern Pacific into deep waters of the proto-North Atlantic through an oceanic gateway in the Central Americas. Once inside, metal-rich waters upwelled against the surrounding continental margins. CLIP volcanism delivered a submarine weathering flux of Cr to the oceans during OAE 2 that was large enough to mask the expected isotopic response of the ocean Cr cycle to increasing anoxia, particularly in the proto-North Atlantic Ocean.

  7. Seasonal hyporheic dynamics control coupled microbiology and geochemistry in Colorado River sediments

    Science.gov (United States)

    Danczak, Robert E.; Sawyer, Audrey H.; Williams, Kenneth H.; Stegen, James C.; Hobson, Chad; Wilkins, Michael J.

    2016-12-01

    Riverbed microbial communities play an oversized role in many watershed ecosystem functions, including the processing of organic carbon, cycling of nitrogen, and alterations to metal mobility. The structure and activity of microbial assemblages depend in part on geochemical conditions set by river-groundwater exchange or hyporheic exchange. To assess how seasonal changes in river-groundwater mixing affect these populations in a snowmelt-dominated fluvial system, vertical sediment and pore water profiles were sampled at three time points at one location in the hyporheic zone of the Colorado River and analyzed by using geochemical measurements, 16S rRNA gene sequencing, and ecological modeling. Oxic river water penetrated deepest into the subsurface during peak river discharge, while under base flow conditions, anoxic groundwater dominated shallower depths. Over a 70 cm thick interval, riverbed sediments were therefore exposed to seasonally fluctuating redox conditions and hosted microbial populations statistically different from those at both shallower and deeper locations. Additionally, microbial populations within this zone were shown to be the most dynamic across sampling time points, underlining the critical role that hyporheic mixing plays in constraining microbial abundances. Given such mixing effects, we anticipate that future changes in river discharge in mountainous, semiarid western U.S. watersheds may affect microbial community structure and function in riverbed environments, with potential implications for biogeochemical processes in riparian regions.

  8. Mercury speciation and mobilization in a wastewater-contaminated groundwater plume

    Science.gov (United States)

    Lamborg, Carl H.; Kent, Doug B.; Swarr, Gretchen J.; Munson, Kathleen M.; Kading, Tristan; O'Connor, Alison E.; Fairchild, Gillian M.; LeBlanc, Denis R.; Wiatrowski, Heather A.

    2013-01-01

    We measured the concentration and speciation of mercury (Hg) in groundwater down-gradient from the site of wastewater infiltration beds operated by the Massachusetts Military Reservation, western Cape Cod, Massachusetts. Total mercury concentrations in oxic, mildly acidic, uncontaminated groundwater are 0.5–1 pM, and aquifer sediments have 0.5–1 ppb mercury. The plume of impacted groundwater created by the wastewater disposal is still evident, although inputs ceased in 1995, as indicated by anoxia extending at least 3 km down-gradient from the disposal site. Solutes indicative of a progression of anaerobic metabolisms are observed vertically and horizontally within the plume, with elevated nitrate concentrations and nitrate reduction surrounding a region with elevated iron concentrations indicating iron reduction. Mercury concentrations up to 800 pM were observed in shallow groundwater directly under the former infiltration beds, but concentrations decreased with depth and with distance down-gradient. Mercury speciation showed significant connections to the redox and metabolic state of the groundwater, with relatively little methylated Hg within the iron reducing sector of the plume, and dominance of this form within the higher nitrate/ammonium zone. Furthermore, substantial reduction of Hg(II) to Hg0 within the core of the anoxic zone was observed when iron reduction was evident. These trends not only provide insight into the biogeochemical factors controlling the interplay of Hg species in natural waters, but also support hypotheses that anoxia and eutrophication in groundwater facilitate the mobilization of natural and anthropogenic Hg from watersheds/aquifers, which can be transported down-gradient to freshwaters and the coastal zone.

  9. Hyporheic flow and dissolved oxygen distribution in fish nests: The effects of open channel velocity, permeability patterns, and groundwater upwelling

    Science.gov (United States)

    Cardenas, M. Bayani; Ford, Aimee E.; Kaufman, Matthew H.; Kessler, Adam J.; Cook, Perran L. M.

    2016-12-01

    Many fish lay their eggs in nests, or redds, which they construct in sediment. The viability of eggs depends on many factors, particularly their oxygenation. Because dissolved oxygen is typically saturated within the stream channel, the dissolved oxygen distribution within the redd depends on whether or not hyporheic flow and transport occur within the sediment. We conducted a series of flume and numerical flow and age transport modeling experiments with the aim of understanding the effects of salmonid redds on the hyporheic transport of young oxygenated water. Hyporheic flow was visualized directly through dye injections. Dissolved oxygen throughout the fish nest was measured using a planar optode. Experiments were conducted at various open channel flow velocities in order to understand their effect on dissolved oxygen, and computational simulations considered various sediment textures and ambient groundwater upwelling rates to add process-level insight. We found that, as also shown by previous studies, the redd topography induces multiscale hyporheic flow that effectively flushes the egg pocket location with younger presumably oxygenated water; older water upwells and forms anoxic zones. This pattern persists even at the lowest channel flow rates and at small upwelling velocities of older ambient groundwater which splits the multiscale hyporheic flow cells into isolated pockets. Large groundwater upwelling rates can shut down all the hyporheic flushing. The relatively coarse texture of the redd further promotes hyporheic flushing of the redd sediment with oxygenated water. Thus, redd morphology and sediment texture optimally combine to induce hyporheic exchange flow that delivers young oxygenated water to the egg pocket.

  10. Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments

    Science.gov (United States)

    Sun, W.; Sierra-Alvarez, R.; Milner, L.; Oremland, R.; Field, J.A.

    2009-01-01

    The objective of this study was to explore a bioremediation strategy based on injecting NO3- to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(III)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flows and filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (column SF1) or absence (column SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 ??g L-1 was reduced to 10.6 (??9.6) ??g L-1 in the effluent of column SF1. The cumulative removal of Fe(II) and As(III) in SF1 was 6.5 to 10-fold higher than that in SF2. Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns were close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxide coated sands with adsorbed As(V). ?? 2009 American Chemical Society.

  11. Enhancement of dimethylsulfide production by anoxic stress in natural seawater

    Science.gov (United States)

    Omori, Yuko; Tanimoto, Hiroshi; Inomata, Satoshi; Wada, Shigeki; Thume, Kathleen; Pohnert, Georg

    2015-05-01

    Dimethylsulfide (DMS) is produced by phytoplankton in the ocean and plays an important role in biogeochemical cycles and climate system of the Earth. Previous field studies reported a possible relationship between DMS enhancement and anoxic condition, although the governing processes are still to be identified. Here we show the first direct evidence for the enhancement of DMS production by natural planktonic assemblages caused by anoxic stress. Under the anoxic condition, DMS production was considerably enhanced and DMS bacterial consumption was inhibited, resulting in an eightfold higher rate of gross DMS production than that under the oxic condition. Our results demonstrated that anoxic stress is one of important "environmental factors" in the marine DMS dynamics, suggesting the possible global importance due to ubiquity of anoxic conditions in the coastal oceans. This process would become more important in the future due to expansion of coastal hypoxic and anoxic zones by global warming.

  12. Biogeochemical factors affecting the presence of 210Po in groundwater

    Science.gov (United States)

    Seiler, R.L.; Stillings, L.L.; Cutler, N.; Salonen, L.; Outola, I.

    2011-01-01

    The discovery of natural 210Po enrichment at levels exceeding 500 mBq/L in numerous domestic wells in northern Nevada, USA, led to a geochemical investigation of the processes responsible for its mobilization. 210Po activities in 63 domestic and public-supply wells ranged from below 1 mBq/L to 6590 ± 590 mBq/L, among the highest reported levels in the USA. There is little spatial or depth variability in 210Pb activity in study-area sediments and mobilization of a few percent of the 210Po in the sediments would account for all of the 210Po in water. Stable-isotope measurements indicate SO4 reduction has occurred in all 210Po contaminated wells. Sulfide species are not accumulating in the groundwater in much of Lahontan Valley, probably because of S cycling involving microbial SO4 reduction, abiotic oxidation of H2S to S0 by Mn(IV), followed by microbial disproportionation of S0 to H2S and SO4. The high pH, Ca depletion, MnCO3 saturation, and presence of S0 in Lahontan Valley groundwater may be consequences of the anaerobic S cycling. Consistent with data from naturally-enriched wells in Florida, 210Po activities begin to decrease when aqueous sulfide species begin to accumulate. This may be due to formation and precipitation of PoS, however, Eh–pH diagrams suggest PoS would not be stable in study-area groundwater. An alternative explanation for the study area is that H2S accumulation begins when anaerobic S cycling stops because Mn oxides are depleted and their reduction is no longer releasing 210Po. Common features of 210Po-enriched groundwater were identified by comparing the radiological and geochemical data from Nevada with data from naturally-enriched wells in Finland, and Florida and Maryland in the USA. Values of pH ranged from 9 in Nevada wells, indicating that pH is not critical in determining whether 210Po is present. Where U is present in the sediments, the data suggest 210Po levels may be elevated in aquifers with (1) SO4-reducing waters with low H2S

  13. Ground-water, surface-water, and bottom-sediment contamination in the O-field area, Aberdeen Proving Ground, Maryland, and the possible effects of selected remedial actions on ground water

    Science.gov (United States)

    Vroblesky, Don A.; Lorah, Michelle M.; Oliveros, James P.

    1995-01-01

    Disposal of munitions and chemical-warfare substances has introduced inorganic and organic contaminants to the ground water, surface water, and bottom sediment at O-Field, in the Edgewood area of Aberdeen Proving Ground, Maryland. Contaminants include chloride, arsenic, transition metals, chlorinated aliphatic hydrocarbons, aromatic compounds, and organosulfur and organophosphorus compounds. The hydrologic effects of several remedial actions were estimated by use of a ground-water-flow model. The remedial actions examined were an impermeable covering, encapsulation, subsurface barriers, a ground-water drain, pumping of wells to manage water levels or to remove contaminated ground water for treatment, and no action.

  14. Hematite Bearing Ridge as Evidence for Anoxic Water Discharge in Gale Crater

    Science.gov (United States)

    Fraeman, A. A.; Arvidson, R. E.; Catalano, J. G.; Morris, R. V.; Murchie, S. L.; Seelos, F. P.; Seelos, K. D.; McGovern, A.; Viviano, C. E.

    2012-12-01

    Mars Reconnaissance Orbiter CRISM hyperspectral imaging data covering the northern flank of Mount Sharp and acquired with pixels spatially oversampled have been processed to retrieve high signal to noise single scattering albedo spectra from 0.45 to 2.6 μm with enhanced spatial resolution. Using these data and coordinated HiRISE images, a ~200 m wide and 6.5 km long ridge to the north of a large channel system emanating from Mount Sharp was identified and mapped. The ridge is composed of finely layered strata dipping to the north and exhibits a strong spectral signature of crystalline hematite. To the west, the ridge transitions to an escarpment overlain by younger strata; to the east, debris flows from Mount Sharp cover and obscure the ridge. The ridge is stratigraphically directly above the clay bearing strata. We interpret the ridge to be formed by erosion associated with outflow from the channel that preferentially stripped away flanking strata not as well cemented by hematite. We hypothesize that the hematite accumulated where anoxic groundwater discharged and came into contact with an oxidizing Martian atmosphere. Anoxic water may have originated as precipitation that percolated through the mound, leaching Fe2+ from the overlying sulfate layers until encountering the clay aquiclude. Alternatively, anoxic Fe2+-rich waters at Gale could have originated by groundwater discharge near the base of the mound. In this scenario, dissolved Fe2+ could be leached from an underlying basaltic aquifer or possibly the clay layer. Given that iron oxidation reactions on Earth may be mediated by chemolithotrophic microorganisms, the ridge provides a compelling site for a detailed measurement campaign by the Mars Science Laboratory Curiosity rover.

  15. Using 14C and 3H to delineate a recharge 'window' into the Perth Basin aquifers, North Gnangara groundwater system, Western Australia.

    Science.gov (United States)

    Meredith, Karina; Cendón, Dioni I; Pigois, Jon-Philippe; Hollins, Suzanne; Jacobsen, Geraldine

    2012-01-01

    The Gnangara Mound and the underlying Perth Basin aquifers are the largest source of groundwater for the southwest of Australia, supplying between 35 and 50% of Perth's potable water (2009-2010). However, declining health of wetlands on the Mound coupled with the reduction in groundwater levels from increased irrigation demands and drier climatic conditions means this resource is experiencing increased pressures. The northern Gnangara is an area where the Yarragadee aquifer occurs at shallow depths (~50 m) and is in direct contact with the superficial aquifer, suggesting the possibility of direct recharge into a generally confined aquifer. Environmental isotopes ((14)C and (3)H) and hydrochemical modelling were used to assess the presence of a recharge 'window' as well as understand the groundwater residence time within different aquifers. Forty-nine groundwater samples were collected from depths ranging from 11 to 311 m below ground surface. The isotopic variation observed in the superficial aquifer was found to be controlled by the different lithologies present, i.e. quartz-rich Bassendean Sand and carbonate-rich sediments of the Ascot Formation. Rainfall recharge into the Bassendean Sand inherits its dissolved inorganic carbon from the soil CO(2). Organic matter throughout the soil profile is degraded by oxidation leading to anoxic/acidic groundwater, which if in contact with the Ascot Formation leads to enhanced dissolution of carbonates. Hydrochemical mass balance modelling showed that carbonate dissolution could contribute 1-2 mmol kg(-1) of carbon to groundwaters recharged through the Ascot Formation. The corrected groundwater residence times of the Yarragadee aquifer in the northern part of the study area ranged from 23 to 35 ka, while waters in the southeastern corner ranged from sub-modern to 2 ka. Groundwater ages increase with distance radiating from the recharge 'window'. This study delineates a recharge 'window' into the commonly presumed confined

  16. Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions

    Science.gov (United States)

    Scholz, Florian; Löscher, Carolin R.; Fiskal, Annika; Sommer, Stefan; Hensen, Christian; Lomnitz, Ulrike; Wuttig, Kathrin; Göttlicher, Jörg; Kossel, Elke; Steininger, Ralph; Canfield, Donald E.

    2016-11-01

    Iron is an essential element for life on Earth and limits primary production in large parts of the ocean. Oxygen-free continental margin sediments represent an important source of bioavailable iron to the ocean, yet little of the iron released from the seabed reaches the productive sea surface. Even in the anoxic water of oxygen minimum zones, where iron solubility should be enhanced, most of the iron is rapidly re-precipitated. To constrain the mechanism(s) of iron removal in anoxic ocean regions we explored the sediment and water in the oxygen minimum zone off Peru. During our sampling campaign the water column featured two distinct redox boundaries separating oxic from nitrate-reducing (i.e., nitrogenous) water and nitrogenous from weakly sulfidic water. The sulfidic water mass in contact with the shelf sediment contained elevated iron concentrations >300 nM. At the boundary between sulfidic and nitrogenous conditions, iron concentrations dropped sharply to nitrate reduction (narG). Part of this upregulation was related to the activity of known iron-oxidizing bacteria. Collectively, our data suggest that iron oxidation and removal is induced by nitrate-reducing microbes, either enzymatically through anaerobic iron oxidation or by providing nitrite for an abiotic reaction. Given the important role that iron plays in nitrogen fixation, photosynthesis and respiration, nitrate-dependent iron oxidation likely represents a key-link between the marine biogeochemical cycles of nitrogen, oxygen and carbon.

  17. Role of the bottom sediments immediately beneath the lake water-groundwater interface in the transport and removal of cyanobacteria, cyanophage, and dissolved organic carbon during natural lake-bank filtration at a kettle pond subject to harmful algal blooms

    Science.gov (United States)

    Harvey, R. W.; Metge, D. W.; LeBlanc, D. R.; Underwood, J. C.; Aiken, G.; McCobb, T. D.; Jasperse, J.

    2015-12-01

    Bank filtration has proven to be a sustainable, cost-effective method of removing cyanobacteria and their harmful toxins from surface water during filtration through bottom and aquifer sediments. The biologically active layer of sediments immediately beneath the sediment-water interface (colmation layer) is believed to be particularly important in this process. An in situ experiment was conducted that involved assessing the transport behaviors of bromide (conservative tracer), Synechococcus sp. IU625 (cyanobacterium, 2.6 ± 0.2 µm), AS-1 (tailed cyanophages, 110 nm long), MS2 (coliphages, 26 nm diameter), and carboxylate-modified microspheres (1.7 µm diameter) introduced to the colmation layer using a bag-and-barrel (Lee-type) seepage meter. The constituents were monitored as they advected through the colmation layer and underlying aquifer sediments at Ashumet Pond in Cape Cod, MA, a mesotrophic kettle pond that recharges a portion of a sole-source, drinking water aquifer. Because the pond DOC includes the various cyanotoxins produced during harmful algal bloom senescence, the DOC and aforementioned colloids were tracked concomitantly. The tracer test constituents were monitored as they advected across the pond water-groundwater interface and through the underlying aquifer sediments under natural-gradient conditions past push-points samplers placed at ~30-cm intervals along a 1.2-m-long, diagonally downward flow path. More than 99% of the microspheres, IU625, MS2, AS-1, and ~42% of the pond DOC were removed in the colmation layer (upper 25 cm of poorly sorted bottom sediments) at two test locations characterized by dissimilar seepage rates (1.7 vs. 0.26 m d-1). Retention profiles in recovered core material indicated that >82% of the attached IU625 were in the top 3 cm of bottom sediments. The colmation layer was also responsible for rapid changes in the character of the DOC and was more effective (by 3 orders of magnitude) at removing microspheres than was the

  18. Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina).

    Science.gov (United States)

    Nicolli, Hugo B; Bundschuh, Jochen; García, Jorge W; Falcón, Carlos M; Jean, Jiin-Shuh

    2010-11-01

    In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Salí River alluvial basin in NW Argentina (Tucumán Province; 7000 km(2)), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km(2)) which is one of the world's largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Salí River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 μg L(-1) leaving 100% of the investigated waters above the provisional WHO guideline value of 10 μg L(-1). A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO(3)) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined

  19. Organic matter provenance, palaeoproductivity and bottom water anoxia during the Cenomanian/Turonian oceanic anoxic event in the Newfoundland Basin (northern proto North Atlantic Ocean)

    NARCIS (Netherlands)

    van Bentum, E.C.; Reichart, G.J.; Sinninghe Damsté, J.S.

    2012-01-01

    Free and sulfur-bound biomarkers in sediments deposited in the northern proto North Atlantic (Newfoundland Basin, ODP Site 1276) during the Cenomanian-Turonian oceanic anoxic event 2 (OAE-2) were studied. The delta C-13 records of phytane and lycopane confirmed the stratigraphic position of the posi

  20. Organic matter provenance, palaeoproductivity and bottom water anoxia during the Cenomanian/Turonian oceanic anoxic event in the Newfoundland Basin (northern proto North Atlantic Ocean)

    NARCIS (Netherlands)

    Bentum, E.C. van; Reichart, G.-J.; Sinninghe Damsté, J.S.

    2012-01-01

    Free and sulfur-bound biomarkers in sediments deposited in the northern proto North Atlantic (Newfoundland Basin, ODP Site 1276) during the Cenomanian-Turonian oceanic anoxic event 2 (OAE-2) were studied. The δ 13C records of phytane and lycopane confirmed the stratigraphic position of the positive

  1. [Predicting prognosis in post-anoxic coma].

    Science.gov (United States)

    Kirsch, M; Boveroux, P; Massion, P; Sadzot, B; Boly, M; Lambermont, B; Lamy, M; Damas, P; Damas, F; Moonen, G; Laureys, S; Ledoux, D

    2008-01-01

    Most patients who remain comatose for a few hours after a period of global cerebral ischemia have a poor prognosis. Early identification of these patients is desirable to reduce uncertainty about treatment and non-treatment decisions, and to improve relationships with the family. The absence of pupillary light response and corneal reflexes, absent or stereotyped extension motor response to noxious stimulation (3 days after insult); myoclonus status epilepticus; absence of cortical N20 response on somatosensory evoked potential studies; generalised suppression or burst-suppression EEG and serum neuron-specific enolase above 33 microg/L (sampled 1-3 days after insult) have been shown to predict poor outcome. We here propose an algorithm to help intensive care physicians' clinical decision making in post-anoxic coma.

  2. Anoxic phosphorus removal in a pilot scale anaerobic-anoxic oxidation ditch process

    Institute of Scientific and Technical Information of China (English)

    Hongxun HOU; Shuying WANG; Yongzhen PENG; Zhiguo YUAN; Fangfang YIN; Wang GAN

    2009-01-01

    The anaerobic-anoxic oxidation ditch (A2/O OD) process is popularly used to eliminate nutrients from domestic wastewater. In order to identify the existence of denitrifying phosphorus removing bacteria (DPB), evalu-ate the contribution of DPB to biological nutrient removal,and enhance the denitrifying phosphorus removal in the A2/O OD process, a pilot-scale A2/O OD plant (375 L)was conducted. At the same time batch tests using sequence batch reactors (12 L and 4 L) were operated to reveal the significance of anoxic phosphorus removal. The results indicated that: The average removal efficiency of COD, NH4+, pO3-4, and TN were 88.2%, 92.6%, 87.8%,and 73.1%, respectively, when the steady state of the pilotscale A2/O OD plant was reached during 31-73d,demonstrating a good denitrifying phosphorus removal performance. Phosphorus uptake took place in the anoxic zone by poly-phosphorus accumulating organisms NO2- could be used as electron receptors in denitrifying phosphorus removal, and the phosphorus uptake rate with NO2- as the electron receptor was higher than that with NO3- when the initial concentration of either NO2- or NO3 was 40 mg/L.

  3. Extremophile microbiomes in acidic and hypersaline river sediments of Western Australia.

    Science.gov (United States)

    Lu, Shipeng; Peiffer, Stefan; Lazar, Cassandre Sara; Oldham, Carolyn; Neu, Thomas R; Ciobota, Valerian; Näb, Olga; Lillicrap, Adam; Rösch, Petra; Popp, Jürgen; Küsel, Kirsten

    2016-02-01

    We investigated the microbial community compositions in two sediment samples from the acidic (pH ∼3) and hypersaline (>4.5% NaCl) surface waters, which are widespread in Western Australia. In West Dalyup River, large amounts of NaCl, Fe(II) and sulfate are brought by the groundwater into the surface run-off. The presence of K-jarosite and schwertmannite minerals in the river sediments suggested the occurrence of microbial Fe(II) oxidation because chemical oxidation is greatly reduced at low pH. 16S rRNA gene diversity analyses revealed that sequences affiliated with an uncultured archaeal lineage named Aplasma, which has the genomic potential for Fe(II) oxidation, were dominant in both sediment samples. The acidophilic heterotrophs Acidiphilium and Acidocella were identified as the dominant bacterial groups. Acidiphilium strain AusYE3-1 obtained from the river sediment tolerated up to 6% NaCl at pH 3 under oxic conditions and cells of strain AusYE3-1 reduced the effects of high salt content by forming filamentous structure clumping as aggregates. Neither growth nor Fe(III) reduction by strain AusYE3-1 was observed in anoxic salt-containing medium. The detection of Aplasma group as potential Fe(II) oxidizers and the inhibited Fe(III)-reducing capacity of Acidiphilium contributes to our understanding of the microbial ecology of acidic hypersaline environments.

  4. Microbially mediated barite dissolution in anoxic brines

    Science.gov (United States)

    Ouyang, Bingjie; Akob, Denise M.; Dunlap, Darren S.; Renock, Devon

    2017-01-01

    Fluids injected into shale formations during hydraulic fracturing of black shale return with extraordinarily high total-dissolved-solids (TDS) and high concentrations of barium (Ba) and radium (Ra). Barite, BaSO4, has been implicated as a possible source of Ba as well as a problematic mineral scale that forms on internal well surfaces, often in close association with radiobarite, (Ba,Ra)SO4. The dissolution of barite by abiotic processes is well quantified. However, the identification of microbial communities in flowback and produced water necessitates the need to understand barite dissolution in the presence of bacteria. Therefore, we evaluated the rates and mechanisms of abiotic and microbially-mediated barite dissolution under anoxic and hypersaline conditions in the laboratory. Barite dissolution experiments were conducted with bacterial enrichment cultures established from produced water from Marcellus Shale wells located in northcentral Pennsylvania. These cultures were dominated by anaerobic halophilic bacteria from the genus Halanaerobium. Dissolved Ba was determined by ICP-OES and barite surfaces were investigated by SEM and AFM. Our results reveal that: 1) higher amounts of barium (up to ∼5 × ) are released from barite in the presence of Halanaerobium cultures compared to brine controls after 30 days of reaction, 2) etch pits that develop on the barite (001) surface in the presence of Halanaerobium exhibit a morphology that is distinct from those that form during control experiments without bacteria, 3) etch pits that develop in the presence of Halanaerobium exhibit a morphology that is similar to the morphology of etch pits formed in the presence of strong organic chelators, EDTA and DTPA, and 4) experiments using dialysis membranes to separate barite from bacteria suggest that direct contact between the two is not required in order to promote dissolution. These results suggest that Halanaerobium increase the rate of barite dissolution in anoxic and

  5. Relations of hydrogeologic factors, groundwater reduction-oxidation conditions, and temporal and spatial distributions of nitrate, Central-Eastside San Joaquin Valley, California, USA

    Science.gov (United States)

    Landon, Matthew K.; Green, Christopher T.; Belitz, Kenneth; Singleton, Michael J.; Esser, Bradley K.

    2011-09-01

    In a 2,700-km2 area in the eastern San Joaquin Valley, California (USA), data from multiple sources were used to determine interrelations among hydrogeologic factors, reduction-oxidation (redox) conditions, and temporal and spatial distributions of nitrate (NO3), a widely detected groundwater contaminant. Groundwater is predominantly modern, or mixtures of modern water, with detectable NO3 and oxic redox conditions, but some zones have anoxic or mixed redox conditions. Anoxic conditions were associated with long residence times that occurred near the valley trough and in areas of historical groundwater discharge with shallow depth to water. Anoxic conditions also were associated with interactions of shallow, modern groundwater with soils. NO3 concentrations were significantly lower in anoxic than oxic or mixed redox groundwater, primarily because residence times of anoxic waters exceed the duration of increased pumping and fertilizer use associated with modern agriculture. Effects of redox reactions on NO3 concentrations were relatively minor. Dissolved N2 gas data indicated that denitrification has eliminated >5 mg/L NO3-N in about 10% of 39 wells. Increasing NO3 concentrations over time were slightly less prevalent in anoxic than oxic or mixed redox groundwater. Spatial and temporal trends of NO3 are primarily controlled by water and NO3 fluxes of modern land use.

  6. Adsorption Characteristics of Remazol Black B on Anoxic Sludge

    Institute of Scientific and Technical Information of China (English)

    HUANG Man-hong; CHEN Liang; CHEN Dong-hui; CHEN Chao-peng

    2009-01-01

    The adsorption characteristics of Remazol Black B on anoxic sludge were investigated. The parameters, such as initial pH, sulphate concentration, and temperature,affecting the dye adsorption were studied. The adsorption data were analyzed with three adsorption isotherm models,namely Langmuir, Freudlich, and linear partition. The results showed that adsorption of Remazol Black B on the sterilized sludge reached equilibrium in 4 h. It also indicated that pH had significant effect on anoxic sludge adsorption behavior. The adsorption capacity of anoxic sludge decreased with the increase of pH value and the maximum adsorption capacity of dyes occurred at pH = 3. The adsorptive capacities increased with the decrease of temperature and increase of sulphate concentration. Results also indicated that the adsorption equilibrium of Remazol Black B on anoxic sludge could be well fitted by Freundlich model.

  7. REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

    Science.gov (United States)

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

  8. Groundwater recharge in Pleistocene sediments overlying basalt aquifers in the Palouse Basin, USA: modeling of distributed recharge potential and identification of water pathways

    NARCIS (Netherlands)

    Dijksma, R.; Brooks, E.S.; Boll, J.

    2011-01-01

    Groundwater levels in basalt aquifers around the world have been declining for many years. Understanding water pathways is needed for solutions like artificial drainage. Water supply in the Palouse Basin, Washington and Idaho, USA, primarily relies on basalt aquifers. This study presents a combinati

  9. Anoxic iron cycling bacteria from an iron sulfide- and nitrate-rich freshwater environment

    Directory of Open Access Journals (Sweden)

    Suzanne Caroline Marianne Haaijer

    2012-02-01

    Full Text Available In this study, both culture-dependent and culture-independent methods were used to determine whether the iron sulfide mineral- and nitrate-rich freshwater nature reserve Het Zwart Water accommodates anoxic microbial iron cycling. Molecular analyses (16S rRNA gene clone library and FISH showed that sulfur-oxidizing denitrifiers dominated the microbial population. In addition, bacteria resembling the iron-oxidizing, nitrate-reducing Acidovorax strain BrG1 accounted for a major part of the microbial community in the groundwater of this ecosystem. Despite the apparent abundance of strain BrG1-like bacteria, iron-oxidizing nitrate reducers could not be isolated, likely due to the strictly autotrophic cultivation conditions adopted in our study. In contrast an iron-reducing Geobacter sp. was isolated from this environment while FISH and 16S rRNA gene clone library analyses did not reveal any Geobacter sp.-related sequences in the groundwater. Our findings indicate that iron-oxidizing nitrate reducers may be of importance to the redox cycling of iron in the groundwater of our study site and illustrate the necessity of employing both culture-dependent and independent methods in studies on microbial processes.

  10. Perils of categorical thinking: "Oxic/anoxic" conceptual model in environmental remediation

    Science.gov (United States)

    Bradley, Paul M.

    2012-01-01

    Given ambient atmospheric oxygen concentrations of about 21 percent (by volume), the lower limit for reliable quantitation of dissolved oxygen concentrations in groundwater samples is in the range of 0.1–0.5 mg/L. Frameworks for assessing in situ redox condition are often applied using a simple two-category (oxic/anoxic) model of oxygen condition. The "oxic" category defines the environmental range in which dissolved oxygen concentrations are clearly expected to impact contaminant biodegradation, either by supporting aerobic biodegradation of electron-donor contaminants like petroleum hydrocarbons or by inhibiting anaerobic biodegradation of electron-acceptor contaminants like chloroethenes. The tendency to label the second category "anoxic" leads to an invalid assumption that oxygen is insignificant when, in fact, the dissolved oxygen concentration is less than detection but otherwise unknown. Expressing dissolved oxygen concentrations as numbers of molecules per volume, dissolved oxygen concentrations that fall below the 0.1 mg/L field detection limit range from 1 to 1017 molecules/L. In light of recent demonstrations of substantial oxygen-linked biodegradation of chloroethene contaminants at dissolved oxygen concentrations well below the 0.1–0.5 mg/L field detection limit, characterizing "less than detection" oxygen concentrations as "insignificant" is invalid.

  11. The Removal of Uranium onto Nanoscale Zero-Valent Iron Particles in Anoxic Batch Systems

    Directory of Open Access Journals (Sweden)

    Richard A. Crane

    2014-01-01

    Full Text Available The removal of uranium (U onto nanoscale zero-valent iron particles has been studied for uranium-bearing mine water and synthetic uranyl solutions in the presence and absence of dissolved oxygen. The work has been conducted in order to investigate the differential nanoparticle corrosion behaviour and associated mechanisms of U removal behaviour in conditions representative of near-surface and deep groundwater systems. Batch systems were analysed over a 28-day reaction period during which the liquid and nanoparticulate solids were periodically analysed to determine chemical evolution of the solutions and particulates. Analysis of aqueous samples using inductively coupled plasma mass spectrometry recorded near-total U removal after 1 hour of reaction in all systems studied. However, in the latter stages of the reaction (after 48 hours, significant rerelease of uranium was recorded for the mine water batch system with dissolved O2 present. In contrast, less than 2% uranium rerelease was recorded for the anoxic batch system. Concurrent analysis of extracted nanoparticle solids using X-ray diffraction recorded significantly slower corrosion of the nanoparticles in the anoxic batch system, with residual metallic iron maintained until after 28 days of reaction compared to only 7 days of reaction in systems with dissolved O2 present. Results provide clear evidence that the corrosion lifespan and associated U6+ removal efficacy of nanoscale zero-valent iron replace enhanced in the absence of dissolved oxygen.

  12. Copper corrosion experiments under anoxic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ollila, Kaija [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-06-15

    This report gives results from the corrosion experiments with copper under anoxic conditions. The objective was to study whether hydrogen-evolving corrosion reaction could occur. Copper foil samples were exposed in deaerated deionized water in Erlenmeyer flasks in the glove box with inert atmosphere. Four corrosion experiments (Cu1, Cu2, Cu3 and Cu4) were started, as well as a reference test standing in air. Cu1 and Cu2 had gas tight seals, whereas Cu3 and Cu4 had palladium foils as hydrogen permeable enclosure. The test vessels were stored during the experiments in a closed stainless steel vessel to protect them from the trace oxygen of the gas atmosphere and light. After the reaction time of three and a half years, there were no visible changes in the copper surfaces in any of the tests in the glove box, in contrast the Cu surfaces looked shiny and unaltered. The Cu3 test was terminated after the reaction time of 746 days. The analysis of the Pd-membrane showed the presence of H2 in the test system. If the measured amount of 7.2{center_dot}10{sup 5} mol H{sub 2} was the result of formation of Cu{sub 2}O this would correspond to a 200 nm thick corrosion layer. This was not in agreement with the measured layer thickness with SIMS, which was 6{+-}1 nm. A clear weight loss observed for the Cu3 test vessel throughout the test period suggests the evaporation of water through the epoxy sealing to the closed steel vessel. If this occurred, the anaerobic corrosion of steel surface in humid oxygen-free atmosphere could be a source of hydrogen. A similar weight loss was not observed for the parallel test (Cu4). The reference test standing in air showed visible development of corrosion products.

  13. Processing, Analysis, and General Evaluation of Well-Driller Logs for Estimating Hydrogeologic Parameters of the Glacial Sediments in a Ground-Water Flow Model of the Lake Michigan Basin

    Science.gov (United States)

    Arihood, Leslie D.

    2009-01-01

    In 2005, the U.S. Geological Survey began a pilot study for the National Assessment of Water Availability and Use Program to assess the availability of water and water use in the Great Lakes Basin. Part of the study involves constructing a ground-water flow model for the Lake Michigan part of the Basin. Most ground-water flow occurs in the glacial sediments above the bedrock formations; therefore, adequate representation by the model of the horizontal and vertical hydraulic conductivity of the glacial sediments is important to the accuracy of model simulations. This work processed and analyzed well records to provide the hydrogeologic parameters of horizontal and vertical hydraulic conductivity and ground-water levels for the model layers used to simulated ground-water flow in the glacial sediments. The methods used to convert (1) lithology descriptions into assumed values of horizontal and vertical hydraulic conductivity for entire model layers, (2) aquifer-test data into point values of horizontal hydraulic conductivity, and (3) static water levels into water-level calibration data are presented. A large data set of about 458,000 well driller well logs for monitoring, observation, and water wells was available from three statewide electronic data bases to characterize hydrogeologic parameters. More than 1.8 million records of lithology from the well logs were used to create a lithologic-based representation of horizontal and vertical hydraulic conductivity of the glacial sediments. Specific-capacity data from about 292,000 well logs were converted into horizontal hydraulic conductivity values to determine specific values of horizontal hydraulic conductivity and its aerial variation. About 396,000 well logs contained data on ground-water levels that were assembled into a water-level calibration data set. A lithology-based distribution of hydraulic conductivity was created by use of a computer program to convert well-log lithology descriptions into aquifer or

  14. Studies of anoxiC conditions in Framvaren fjord, Gullmaren fjord and Byfjorden and of mixing between seawater and freshwater at the Kalix river and estuary

    Energy Technology Data Exchange (ETDEWEB)

    Roos, P. [Univ. of Lund, Lund (Sweden)

    2001-04-01

    The sediments in the anoxic Framvaren fjord acts as a source for actinides to the overlaying water column. The remobilisation process is most likely linked to early diagenetic alteration of the marine organic material in the sediments. This is indicated by the close correlation between Pu, Am and dissolved organic carbon depth profiles in the water column. Speciation studies of the plutonium and americium in the water column shows that both to a large degree are associated to colloidal material in the size range 0.01-0.45 {mu}m. Less than 2% is retained by a 0.45 {mu}m filter which is reflected in the low K{sub D}-values obtained of about 20 000, which is at least a factor of 10 lower than in typical coastal waters. It is also proven that the plutonium exist almost entirely in the trivalent state in the anoxic water column. This study is the first ever to show extensive remobilisation of plutonium and americium from sediments in anoxic marine basins. Similar remobilisation from sediments most likely occur in other anoxic marine waters where early diagenesis results in humic and fulvic acid production. Although the remobilised actinides in the Framvaren fjord at present don't pose any radiological hazard due to the lack of fish in anoxic waters, it is of great concern to identify processes involved in the remobilisation of actinides from anoxic sediments as such sediments likely will be a major source for actinides in the Baltic Sea and other oxygen sensitive basins in the long term perspective. In such basins the remobilised plutonium may reach oxygenated and biological productive waters by convection. Results from the temporarily oxygen deficient Gullmaren fjord on the Swedish west coast shows that remobilisation from sediments can not be identified during short (a few months) periods of oxygen deficient water. The rapid bioturbation (quantified by tracer studies) in this fjord results in that sedimenting organic material rapidly is buried and distributed

  15. Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments.

    Science.gov (United States)

    Stoliker, Deborah L; Campbell, Kate M; Fox, Patricia M; Singer, David M; Kaviani, Nazila; Carey, Minna; Peck, Nicole E; Bargar, John R; Kent, Douglas B; Davis, James A

    2013-08-20

    Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

  16. Evaluating chemical extraction techniques for the determination of uranium oxidation state in reduced aquifer sediments

    Science.gov (United States)

    Stoliker, Deborah L.; Campbell, Kate M.; Fox, Patricia M.; Singer, David M.; Kaviani, Nazila; Carey, Minna; Peck, Nicole E.; Barger, John R.; Kent, Douglas B.; Davis, James A.

    2013-01-01

    Extraction techniques utilizing high pH and (bi)carbonate concentrations were evaluated for their efficacy in determining the oxidation state of uranium (U) in reduced sediments collected from Rifle, CO. Differences in dissolved concentrations between oxic and anoxic extractions have been proposed as a means to quantify the U(VI) and U(IV) content of sediments. An additional step was added to anoxic extractions using a strong anion exchange resin to separate dissolved U(IV) and U(VI). X-ray spectroscopy showed that U(IV) in the sediments was present as polymerized precipitates similar to uraninite and/or less ordered U(IV), referred to as non-uraninite U(IV) species associated with biomass (NUSAB). Extractions of sediment containing both uraninite and NUSAB displayed higher dissolved uranium concentrations under oxic than anoxic conditions while extractions of sediment dominated by NUSAB resulted in identical dissolved U concentrations. Dissolved U(IV) was rapidly oxidized under anoxic conditions in all experiments. Uraninite reacted minimally under anoxic conditions but thermodynamic calculations show that its propensity to oxidize is sensitive to solution chemistry and sediment mineralogy. A universal method for quantification of U(IV) and U(VI) in sediments has not yet been developed but the chemical extractions, when combined with solid-phase characterization, have a narrow range of applicability for sediments without U(VI).

  17. A decade of investigations on groundwater arsenic contamination in Middle Ganga Plain, India.

    Science.gov (United States)

    Saha, Dipankar; Sahu, Sudarsan

    2016-04-01

    Groundwater arsenic (As) load in excess of drinking limit (50 µg L(-1)) in the Gangetic Plains was first detected in 2002. Though the menace was known since about two decades from the downstream part of the plains in the Bengal Basin, comprising of Lower Ganga Plain and deltaic plains of Ganga-Brahmaputra-Meghna River system, little thought was given to its possible threat in the upstream parts in the Gangetic Plains beyond Garo-Rajmahal Hills. The contamination in Bengal Basin has become one of the extensively studied issues in the world and regarded as the severest case of health hazard in the history of mankind. The researches and investigations in the Gangetic Plains during the last decade (2003-2013) revealed that the eastern half of the plains, also referred as Middle Ganga Plain (MGP), is particularly affected by contamination, jeopardising the shallow aquifer-based drinking water supply. The present paper reviews researches and investigations carried out so far in MGP by various research institutes and government departments on wide array of issues of groundwater As such as its spatio-temporal variation, mobilisation paths, water level behaviour and flow regime, configuration of contaminated and safe aquifers and their recharge mechanism. Elevated conc. of groundwater As has been observed in grey and dark grey sediments of Holocene age (Newer Alluvium) deposited in a fluvio-lacustrine environment in the floodplain of the Ganga and most of its northern tributaries from Himalayas. Older Alluvium, comprising Pleistocene brownish yellow sediment, extending as deeper aquifers in Newer Alluvium areas, is low in groundwater As. Similarities and differences on issues between the MGP and the Bengal Basin have been discussed. The researches point towards the mobilisation process as reductive dissolution of iron hydroxide coating, rich in adsorbed As, mediated by microbial processes. The area is marked with shallow water level (ground) with ample monsoonal recharge

  18. Biological phosphorus uptake under anoxic and aerobic conditions

    DEFF Research Database (Denmark)

    Kerrn-Jespersen, Jens Peter; Henze, Mogens

    1993-01-01

    Biological phosphorus removal was investigated under anoxic and aerobic conditions. Tests were made to establish whether phosphorus accumulating bacteria can take up phosphate under anoxic conditions and thus utilise nitrate as oxidant. Furthermore, it was tested how the amount of organic matter...... sludge from two different pilot plants incorporating phosphorus removal. The results showed that the phosphorus accumulating bacteria can be divided into two groups in respect of process; one group capable of utilising only oxygen as oxidant and another group capable of utilising both oxygen and nitrate...... taken up by the phosphorus accumulating bacteria during the anaerobic phase affects the total denitrification rate, as well as the rate at which the phosphorus accumulating bacteria take up phosphate under anoxic conditions. The tests were conducted as batch experiments in 21. reactors with activated...

  19. Sediment Oxygen Demand in Cochin backwaters, a tropical estuarine system in the south-west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Abhilash, K.R.; Raveendran, T.V.; LimnaMol, V.P.; Deepak, M.P.

    Eutrophication has often been one of the major problems encountered in estuaries and coastal waters. The oxic/anoxic status of an estuary can be effectively determined by measurement of the Sediment Oxygen Demand (SOD). An attempt is made...

  20. Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

    DEFF Research Database (Denmark)

    Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V.

    2014-01-01

    The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are re......The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid...

  1. Influence of groundwater composition on subsurface iron and arsenic removal

    KAUST Repository

    Moed, David H.

    2012-06-01

    Subsurface arsenic and iron removal (SAR/SIR) is a novel technology to remove arsenic, iron and other groundwater components by using the subsoil. This research project investigated the influence of the groundwater composition on subsurface treatment. In anoxic sand column experiments, with synthetic groundwater and virgin sand, it was found that several dissolved substances in groundwater compete for adsorption sites with arsenic and iron. The presence of 0.01 mmol L -1phosphate, 0.2 mmol L -1 silicate, and 1 mmol L -1 nitrate greatly reduced the efficiency of SAR, illustrating the vulnerability of this technology in diverse geochemical settings. SIR was not as sensitive to other inorganic groundwater compounds, though iron retardation was limited by 1.2 mmol L -1 calcium and 0.06 mmol L -1 manganese. © IWA Publishing 2012.

  2. Silting up and development of anoxic conditions enhanced by high abundance of the geoengineer species Ophiothrix fragilis

    Science.gov (United States)

    Murat, A.; Méar, Y.; Poizot, E.; Dauvin, J. C.; Beryouni, K.

    2016-04-01

    In the English Channel, the brittle-star Ophiothrix fragilis is a common epifaunal species typically found on pebbles in habitats with strong tidal currents. This species forms dense aggregations on the seafloor, supporting populations that can reach up to 7500 ind m-2 in the eastern part of the Baie de Seine, offshore from Antifer harbour. Here, O. fragilis occurs in an area with unexpected amounts of fine-grained sediment. Some of these mud deposits are made up of unusually compact black muds, an indication of the development of anoxic conditions in surficial sediments. To highlight a potential link between silting up and dense O. fragilis populations, and identify the interactions between environmental conditions and the population dynamics of this species, we analyse the data from three surveys corresponding to exceptional situations: (1) just after a Seine flood; (2) just after a storm and (3) after a period of ten months without any flood or storm. Four parameters are taken into account: number of brittle stars per 0.25 m2, Fine Fraction percentage, Total Organic Carbon and Total Sulphur. The main environmental forcings appear to be Seine river inflow, regional circulation dependent on tidal currents and the occurrence of storms. O. fragilis is able to geoengineer its environment in various ways and at different rates. Silting up is enhanced by increasing abundance of O. fragilis and takes place at a very fast rate. As a result, floods and storms reflecting instantaneous events give rise to a steady-state situation established between the abundance of this species and the fine fraction percentage. Anoxic conditions are dependent on the degradation of organic matter and require more time to be established. After many months in the absence of any disturbing events, anoxic conditions are developed in non-compacted muddy sediments (stability situation) and represent the normal surficial situation when the sediment becomes compacted (compact black muds). The

  3. Paleoenvironmental responses to Late Cretaceous Oceanic Anoxic Event 2 on the Kerguelen Plateau

    Science.gov (United States)

    Dickson, A.; Saker-Clark, M.; Jenkyns, H. C.; Erba, E.; Bottini, C.; Murphy, M. J.; Gorbanenko, O.; Idiz, E.; van den Boorn, S.

    2014-12-01

    Oceanic Anoxic Event 2 (OAE-2, ~94 Ma: late Cretaceous) was characterized by a perturbation in seawater chemistry, an expansion of marine anoxia and euxinia, an increase in marine organic-carbon burial, a decrease in atmospheric pCO2 during an interval of high global temperatures, an extinction event among marine organisms, and changes in weathering intensity. However, many of the most detailed studies of OAE-2 are from the northern hemisphere, and consequently how global environmental changes were expressed at the local and regional scale in the southern hemisphere is poorly understood. A detailed geochemical, petrographic and micropalaeontological dataset from Ocean Drilling Program Site 1138 on the Kerguelen Plateau, southern Indian Ocean (53.5oS paleolatitude), identifies OAE-2 from a 3‰ positive carbon-isotope excursion (CIE) and from high-resolution nannofossil biostratigraphy. An enrichment of organic carbon (to ~15%) corresponds with a shift towards locally sub-oxic/anoxic conditions, as recorded by trace-metal enrichments and molybdenum-isotope compositions. The redox changes coincide stratigraphically with an abrupt decline in the delivery of highly weathered detrital material and terrestrial organic matter to Site 1138. A rapid relative sea-level rise occurring around the onset of OAE-2 could have reduced the input of highly weathered detrital sediments, while moving the local seafloor deeper into an oxygen minimum zone impinging on the margins of the Kerguelen Plateau. Alternatively, or additionally, intensified mid-latitude hydrological cycling in the early stages of OAE-2 could have rapidly destabilized terrestrial sediments from sub-aerial landmasses on the Kerguelen Plateau. In either case, the new datasets highlight the abrupt nature of the palaeoenvironmental response to OAE-2 in the mid-latitude southern hemisphere.

  4. Cable Bacteria in Freshwater Sediments

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus

    2015-01-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable...... bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures...... marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary...

  5. Evidence of CFC degradation in groundwater under pyrite-oxidizing conditions

    Science.gov (United States)

    Sebol, L.A.; Robertson, W.D.; Busenberg, E.; Plummer, L.N.; Ryan, M.C.; Schiff, S.L.

    2007-01-01

    A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1-5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ???5 years old was confined to an aerobic zone at ???5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7-11 ??C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6-7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3H/3He ratios indicated that groundwater-age continued to increase uniformly with depth, to a maximum value of 27 years at 13 m depth. CFC concentrations, however, decreased abruptly within the denitrifying zone, leading to substantial age overestimation compared to the 3H/3He ages. Noble gas data indicated that the apparent CFC mass loss was not likely the result of gas stripping from possible bubble formation; thus, CFC degradation was indicated in the anoxic zone. The field data are consistent with first-order degradation rates of 0.3 yr-1 for CFC-12, 0.7 yr-1 for CFC-11, and 1.6 yr-1 for CFC-113. CFC attenuation at this site coincides with a zone where reduced S (pyrite) is actively oxidized by NO3 and dissolved oxygen (DO). Similar behavior has been observed at other sites [Tesoriero, A.J., Liebscher, H., Cox, S.E., 2000. Mechanism and rate of denitrification in an agricultural watershed: electron and mass balance along groundwater flow path. Water Resour. Res. 36 (6), 1545-1559; Hinsby, K., Hojberg, A.L., Engesgaard, P., Jensen, K.H., Larsen, F., Plummer, L.N., Busenberg, E., Accepted for publication. Transport and degradation of chlorofluorocarbons (CFCs) in a pyritic aquifer, Rabis Creek, Denmark. Water Resour. Res.], further demonstrating that the use of CFCs for age-dating anaerobic

  6. Why Oceanic Anoxic Events Terminated? Data and Speculations About the end of OAE1a.

    Science.gov (United States)

    Erba, E.

    2006-12-01

    /or hiatuses in sedimentary successions. However, evidence for a generalized sedimentation break has not been forwarded and an internal cause seems more plausible. I suspect that the duration of OAE1a is a direct measure of excess CO2, inducing oceanic acidification, hampering biocalcification and maintaining a greenhouse climate while turning the oceans into an immense anoxic pool. The combination of these conditions favored peculiar primary producers and resulted in the deposition of carbonate-poor and organic matter-rich anoxic sediments. Burial of massive amounts of organic C and accelerated weathering drastically lowered CO2 levels allowing/stimulating calcification and inducing reversed greenhouse conditions. The persistence of the C isotopic anomaly after cessation of anoxia poses intriguing questions regarding the links between anoxia, primary productivity and perturbations of the carbon cycle.

  7. Molybdenum drawdown during Cretaceous Oceanic Anoxic Event 2

    NARCIS (Netherlands)

    Goldberg, T.; Poulton, S.W.; Wagner, T.; Kolonic, S.F.; Rehkämper, M.

    2016-01-01

    During the Cretaceous greenhouse, episodes of widespread ocean deoxygenation were associated with globally occurring events of black shale deposition. Possibly the most pronounced of these oceanic anoxic events (OAE's) was the Cenomanian-Turonian OAE2 (~94 Ma). However, although certain redox sensit

  8. The enigma of prokaryotic life in deep hypersaline anoxic basins

    NARCIS (Netherlands)

    van der Wielen, PWJJ; Bolhuis, H; Borin, S; Daffonchio, D; Corselli, C; Giuliano, L; D'Auria, G; de Lange, GJ; Huebner, A; Varnavas, SP; Thomson, J; Tamburini, C; Marty, D; McGenity, TJ; Timmis, KN

    2005-01-01

    Deep hypersaline anoxic basins in the Mediterranean Sea are a legacy of dissolution of ancient subterranean salt deposits from the Miocene period. Our study revealed that these hypersaline basins are not biogeochemical dead ends, but support in situ sulfate reduction, methanogenesis, and heterotroph

  9. Bioavailability of Metals in Contaminated Sediments

    Directory of Open Access Journals (Sweden)

    Paller M. H.

    2013-04-01

    Full Text Available Bioavailability controls the transfer of metals from sediments to ecological receptors and humans. It can rarely be predicted from total metal concentrations because it is affected by metal geochemistry in sediments as well as the biochemistry, physiology, and behavior of benthic organisms. There is no single approach for including bioavailability in risk assessments because of variability in site specific conditions and the difficulty of validating methods. Acid-volatile sulfide and simultaneously extracted metals are useful in predicting bioavailability in anoxic sediments containing sulfides that react to form insoluble metal complexes. This method can be improved by adjusting for organic carbon and other ligands that also bind free metals. Site-specific desorption Kd values calculated by sequential extraction methods can be useful in predicting bioavailable metal fractions in oxic and anoxic sediments. A modified desorption distribution coefficient (Kdg can be calculated by extraction with the digestive gut fluids of sediment feeding organisms to account for the effects of ingestion on metal release from sediments. Recently developed in situ measurement technologies can accumulate dissolved metals in a controlled fashion that may correspond with bioavailable metal fractions in sediment. Successful evaluation of bioavailability requires the selection of methods suitable for the organisms and sediment environments under consideration. A weight-of-evidence approach that incorporates multiple lines of evidence can help address uncertainties and increase the likelihood of incorporating bioavailability into remedial decisions.

  10. The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifera

    Directory of Open Access Journals (Sweden)

    Fox Patricia M

    2004-04-01

    Full Text Available We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1 the uncontaminated zone above the sewage plume [350 μM dissolved oxygen (DO, pH 5.9]; (2 the suboxic zone (5 μM DO, pH 6.2, elevated concentrations of sewage-derived phosphate and nitrate; and (3 the anoxic zone [dissolved iron(II 100–300 μM, pH 6.5–6.9, elevated concentrations of sewage-derived phosphate]. Sediments are comprised of greater than 90% quartz but the surfaces of quartz and other mineral grains are coated with nanometer-size iron (Fe and aluminum (Al oxides and/or silicates, which control the adsorption properties of the sediments. Uncontaminated groundwater with added phosphate (620 μM was pumped into the uncontaminated zone while samples were collected 0.3 m above the injection point. Concentrations of As(V increased from below detection (0.005 μM to a maximum of 0.07 μM during breakthrough of phosphate at the sampling port; As(III concentrations remained below detection. These results are consistent with the hypothesis that naturally occurring As(V adsorbed to constituents of the coatings on grain surfaces was desorbed by phosphate in the injected groundwater. Also consistent with this hypothesis, vertical profiles of groundwater chemistry measured prior to the tracer test showed that dissolved As(V concentrations increased along with dissolved phosphate from below detection in the uncontaminated zone to approximately 0.07 and 70 μM, respectively, in the suboxic zone. Concentrations of As(III were below detection in both zones. The anoxic zone had approximately 0.07 μM As(V but also had As(III concentrations of 0.07–0.14 μM, suggesting that release of As bound to sediment grains occurred by desorption by phosphate

  11. Oceanic oxygenation events in the anoxic Ediacaran ocean.

    Science.gov (United States)

    Sahoo, S K; Planavsky, N J; Jiang, G; Kendall, B; Owens, J D; Wang, X; Shi, X; Anbar, A D; Lyons, T W

    2016-09-01

    The ocean-atmosphere system is typically envisioned to have gone through a unidirectional oxygenation with significant oxygen increases in the earliest (ca. 635 Ma), middle (ca. 580 Ma), or late (ca. 560 Ma) Ediacaran Period. However, temporally discontinuous geochemical data and the patchy metazoan fossil record have been inadequate to chart the details of Ediacaran ocean oxygenation, raising fundamental debates about the timing of ocean oxygenation, its purported unidirectional rise, and its causal relationship, if any, with the evolution of early animal life. To better understand the Ediacaran ocean redox evolution, we have conducted a multi-proxy paleoredox study of a relatively continuous, deep-water section in South China that was paleogeographically connected with the open ocean. Iron speciation and pyrite morphology indicate locally euxinic (anoxic and sulfidic) environments throughout the Ediacaran in this section. In the same rocks, redox sensitive element enrichments and sulfur isotope data provide evidence for multiple oceanic oxygenation events (OOEs) in a predominantly anoxic global Ediacaran-early Cambrian ocean. This dynamic redox landscape contrasts with a recent view of a redox-static Ediacaran ocean without significant change in oxygen content. The duration of the Ediacaran OOEs may be comparable to those of the oceanic anoxic events (OAEs) in otherwise well-oxygenated Phanerozoic oceans. Anoxic events caused mass extinctions followed by fast recovery in biologically diversified Phanerozoic oceans. In contrast, oxygenation events in otherwise ecologically monotonous anoxic Ediacaran-early Cambrian oceans may have stimulated biotic innovations followed by prolonged evolutionary stasis.

  12. Pushpoint sampling for defining spatial and temporal variations in contaminant concentrations in sediment pore water near the ground-water / surface-water interface

    Science.gov (United States)

    Zimmerman, Marc J.; Massey, Andrew J.; Campo, Kimberly W.

    2005-01-01

    During four periods from April 2002 to June 2003, pore-water samples were taken from river sediment within a gaining reach (Mill Pond) of the Sudbury River in Ashland, Massachusetts, with a temporary pushpoint sampler to determine whether this device is an effective tool for measuring small-scale spatial variations in concentrations of volatile organic compounds and selected field parameters (specific conductance and dissolved oxygen concentration). The pore waters sampled were within a subsurface plume of volatile organic compounds extending from the nearby Nyanza Chemical Waste Dump Superfund site to the river. Samples were collected from depths of 10, 30, and 60 centimeters below the sediment surface along two 10-meter-long, parallel transects extending into the river. Twenty-five volatile organic compounds were detected at concentrations ranging from less than 1 microgram per liter to hundreds of micrograms per liter (for example, 1,2-dichlorobenzene, 490 micrograms per liter; cis-1,2-dichloroethene, 290 micrograms per liter). The most frequently detected compounds were either chlorobenzenes or chlorinated ethenes. Many of the compounds were detected only infrequently. Quality-control sampling indicated a low incidence of trace concentrations of contaminants. Additional samples collected with passive-water-diffusion-bag samplers yielded results comparable to those collected with the pushpoint sampler and to samples collected in previous studies at the site. The results demonstrate that the pushpoint sampler can yield distinct samples from sites in close proximity; in this case, sampling sites were 1 meter apart horizontally and 20 or 30 centimeters apart vertically. Moreover, the pushpoint sampler was able to draw pore water when inserted to depths as shallow as 10 centimeters below the sediment surface without entraining surface water. The simplicity of collecting numerous samples in a short time period (routinely, 20 to 30 per day) validates the use of a

  13. Assessment of Halon-1301 as a groundwater age tracer

    Science.gov (United States)

    Beyer, M.; van der Raaij, R.; Morgenstern, U.; Jackson, B.

    2015-06-01

    Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and timescale of groundwater flow and recharge, contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their individual restricted application ranges. For more robust groundwater dating multiple tracers need to be applied complementarily (or other characterisation methods need to be used to complement tracer information). It is important that additional, groundwater age tracers are found to ensure robust groundwater dating in future. We have recently suggested that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate, but its behaviour in water and suitability as a groundwater age tracer had not yet been assessed in detail. In this study, we determined Halon-1301 and inferred age information in 17 New Zealand groundwater samples and various modern (river) water samples. The samples were simultaneously analysed for Halon-1301 and SF6, which allowed for identification of issues such as contamination of the water with modern air during sampling. All analysed groundwater sites had also been previously dated with tritium, CFC-12, CFC-11 and SF6, and exhibited mean residence times ranging from modern (close to 0 years) to over 100 years. The investigated groundwater samples ranged from oxic to highly anoxic. All samples with available CFC data were degraded and/or contaminated in one or both of CFC-11 and CFC-12. This allowed us to make a first attempt of assessing the conservativeness of Halon-1301 in water, in terms of presence of local sources and its sensitivity towards degradation, which could affect the suitability of Halon-1301 as groundwater age tracer. Overall we found Halon-1301

  14. Assessment of Halon-1301 as a groundwater age tracer

    Directory of Open Access Journals (Sweden)

    M. Beyer

    2015-01-01

    Full Text Available Groundwater dating is an important tool to assess groundwater resources in regards to their dynamics, i.e. direction and time scale of groundwater flow and recharge, to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However, ambiguous age interpretations are often faced, due to a limited set of available tracers and their individual restricted application ranges. For more robust groundwater dating multiple tracers need to be applied complementarily and it is vital that additional, groundwater age tracers are found to ensure robust groundwater dating in future. We recently suggested that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate, but its behaviour in water and suitability as a groundwater age tracer had not yet been assessed in detail. In this study, we determine Halon-1301 and infer age information in 17 New Zealand groundwaters and various modern (river water samples. The samples are simultaneously analysed for Halon-1301 and SF6, which allows identification of issues such as contamination of the water with modern air during sampling. Water at all analysed groundwater sites have also been previously dated with tritium, CFC-12, CFC-11 and SF6, and exhibit mean residence times ranging from modern (close to 0 years to over 100 years. The investigated groundwater ranged from oxic to highly anoxic, and some showed evidence of CFC contamination or degradation. This allowed us to make a first attempt of assessing the conservativeness of Halon-1301 in water, in terms of presence of local sources and its sensitivity towards degradation etc., which could affect the suitability of Halon-1301 as groundwater age tracer. Overall we found Halon-1301 reliably inferred the mean residence time of groundwater recharged between 1980 and 2014. Where direct age comparison

  15. Characteristics of anoxic phosphors removal in sequence batch reactor

    Institute of Scientific and Technical Information of China (English)

    WANG Ya-yi; PAN Mian-li; Yan Min; PENG Yong-zhen; WANG Shu-ying

    2007-01-01

    The characteristics of anaerobic phosphorus release and anoxic phosphorus uptake was investigated in sequencing batch reactors using denitrifying phosphorus removing bacteria (DPB) sludge. The lab-scale experiments were accomplished under conditions of various nitrite concentrations (5.5, 9.5, and 15 mg/L) and mixed liquor suspended solids (MLSS) (1844, 3231, and 6730 mg/L). The results obtained confirmed that nitrite, MLSS, and pH were key factors, which had a significant impact on anaerobic phosphorus release and anoxic phosphorus uptake in the biological phosphorous removal process. The nitrites were able to successfully act as electron acceptors for phosphorous uptake at a limited concentration between 5.5 and 9.5 mg/L. The denitrification and dephosphorous were inhibited when the nitrite concentration reached 15 mg/L. This observation indicated that the nitrite would not inhibit phosphorus uptake before it exceeded a threshold concentration. It was assumed that an increase of MLSS concentration from 1844 mg/L to 6730 mg/L led to the increase of denitrification and anoxic P-uptake rate. On the contrary, the average P uptake/N denitrifying reduced from 2.10 to 1.57 mg PO43--P/mg NO3--N. Therefore, it could be concluded that increasing MLSS of the DEPHANOX system might shorten the reaction time of phosphorus release and anoxic phosphorus uptake. However, excessive MLSS might reduce the specific denitrifying rate. Meanwhile, a rapid pH increase occurred at the beginning of the anoxic conditions as a result of denitrification and anoxic phosphate uptake. Anaerobic P release rate increased with an increase in pH. Moreover, when pH exceeded a relatively high value of 8.0, the dissolved P concentration decreased in the liquid phase, because of chemical precipitation. This observation suggested that pH should be strictly controlled below 8.0 to avoid chemical precipitation if the biological denitrifying phosphorus removal capability is to be studied accurately.

  16. Microbially induced corrosion of carbon steel in deep groundwater environment

    Directory of Open Access Journals (Sweden)

    Pauliina eRajala

    2015-07-01

    Full Text Available The metallic low and intermediate level radioactive waste generally consists of carbon steel and stainless steels. The corrosion rate of carbon steel in deep groundwater is typically low, unless the water is very acidic or microbial activity in the environment is high. Therefore, the assessment of microbially induced corrosion of carbon steel in deep bedrock environment has become important for evaluating the safety of disposal of radioactive waste. Here we studied the corrosion inducing ability of indigenous microbial community from a deep bedrock aquifer. Carbon steel coupons were exposed to anoxic groundwater from repository site 100 m depth (Olkiluoto, Finland for periods of three and eight months. The experiments were conducted at both in situ temperature and room temperature to investigate the response of microbial population to elevated temperature. Our results demonstrate that microorganisms from the deep bedrock aquifer benefit from carbon steel introduced to the nutrient poor anoxic deep groundwater environment. In the groundwater incubated with carbon steel the planktonic microbial community was more diverse and 100-fold more abundant compared to the environment without carbon steel. The betaproteobacteria were the most dominant bacterial class in all samples where carbon steel was present, whereas in groundwater incubated without carbon steel the microbial community had clearly less diversity. Microorganisms induced pitting corrosion and were found to cluster inside the corrosion pits. Temperature had an effect on the species composition of microbial community and also affected the corrosion deposits layer formed on the surface of carbon steel.

  17. The importance of diazotrophic cyanobacteria as primary producers during Cretaceous Oceanic Anoxic Event 2

    Directory of Open Access Journals (Sweden)

    N. Ohkouchi

    2006-01-01

    Full Text Available In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca. 94 Ma, nitrogen isotopic compositions of bulk sediments are mostly in a narrow range from –2.7 to –0.7‰. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C32 Ni deoxophylloerythroetioporphyrin (DPEP and total Ni porphyrins are –3.5 and –3.3‰, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cells were around +1‰ during the formation of Bonarelli black shale. This value is suggestive of N2-fixation, a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived mainly from chlorophyll a had the highest concentration. Based on this evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. Cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth's history, and hence may have played a crucial role in the evolution of geochemical cycles even in the later half of the Earth's history.

  18. An importance of diazotrophic cyanobacteria as a primary producer during Cretaceous Oceanic Anoxic Event 2

    Directory of Open Access Journals (Sweden)

    N. Ohkouchi

    2006-06-01

    Full Text Available In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic Event 2 (OAE-2, ca. 94 Ma, nitrogen isotopic compositions of bulk sediments are in a narrow range from −2.7 to −0.7. We also determined molecular distribution and nitrogen isotopic compositions of geoporphyrins extracted from the black shale. The nitrogen isotopic compositions of C32 Ni deoxophylloerythroetioporphyrin (DPEP and total Ni porphyrins are −3.5 and −3.3, respectively, leading us to the estimation that the mean nitrogen isotopic composition of photoautotrophic cell was around +1 during the formation of Bonarelli black shale. This value is suggestive of N2-fixation a dominant process for these photoautotrophs when assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived mainly from chlorophyll a was the highest concentration. Based on these evidence, we conclude that diazotrophic cyanobacteria were major primary producers during that time. The cyanobacteria may be key photoautotrophs during the formation of black shale type sediments intermittently observed throughout the later half of the Earth's history, and hence may have played a crucial role in the evolution of geochemical cycles.

  19. Fluid displacive resin embedding of laminated sediments: preserving trace metals for high-resolution paleoclimate investigations

    NARCIS (Netherlands)

    Jilbert, T.; Lange, G.J. de; Reichart, G.-J.

    2008-01-01

    For the high-resolution study of trace metal profiles in laminated anoxic sediments, a specially adapted method of resin embedding has been developed. Fluid displacement is the preferred means of sediment dehydration, offering optimum structural preservation and facilitating desalination. Exchanges

  20. The impact of electrogenic sulfide oxidation on elemental cycling and solute fluxes in coastal sediment

    NARCIS (Netherlands)

    Rao, A.M.F.; Malkin, S.Y.; Hidalgo-Martinez, S.; Meysman, Filip

    2016-01-01

    Filamentous sulfide oxidizing cable bacteria are capable of linking the oxidation of free sulfide in deep anoxic layers of marine sediments to the reduction of oxygen or nitrate in surface sediments by conducting electrons over centimeter-scale distances. Previous studies have shown that this newly

  1. Does vivianite control phosphate solubility in anoxic meadow soils?

    DEFF Research Database (Denmark)

    Walpersdorf, Eva Christine; Bender Koch, Christian; Heiberg, Lisa

    2013-01-01

    composition in the gyttja layer was close to equilibrium with vivianite (saturation index, SIviv, 2.01±0.53) at constant pH (~ 6.8). Dissolution and precipitation experiments in the laboratory with soil suspensions from the gyttja layer demonstrated that vivianite solubility equilibria were only slowly......Vivianite (Fe3(PO4)2·8H2O) may precipitate in anoxic wetland soils where it may control orthophosphate (Pi) equilibrium solution concentrations at micromolar levels, and thus be of key importance in reducing excessive P from agricultural sources and eutrophication. However, vivianite equilibria...... restored. Even after 120 days following perturbation the supersaturation was still high (SIviv~6). It seems that vivianite does contribute to Pi immobilization in anoxic soil horizons, but due to slow precipitation kinetics such soils cannot maintain Pi concentrations at levels below critical thresholds...

  2. The Cogollo Group and the oceanic anoxic events 1a and 1b, Maracaibo basin, Venezuela

    Directory of Open Access Journals (Sweden)

    José Alejandro Méndez Dot

    Full Text Available ABSTRACTCarbonates of Cogollo Group (Apón, Lisure and Maraca formations constitute the broader calcareous platform system originated during Aptian and Albian of Cretaceous in north-western South America, Maracaibo Basin, Venezuela. On the shallow shelf, a variety of calcareous sedimentary facies were deposited during marine transgressive and regressive cycles. Some of them developed porosity and constitute important hydrocarbon reservoirs. Due to some major marine transgressions, from early Aptian, the anoxic environment and characteristic facies of a pelagic environment moved from the outer slope and basin to the shallow shelf, during specific time intervals, favouring the sedimentation of organic matter-rich facies, which correspond to the oceanic anoxic events (OAEs 1a and 1b. The source rock of Machiques Member (Apón Formation was deposited during early Aptian OAE 1a (~ 120 Ma. The source rock of Piché Member, located at the top of the Apón Formation, was deposited during late Aptian OAE 1b (~ 113 Ma. Finally, La Luna Formation, from Cenomanian, that covers the OAE 2 (~ 93 Ma, represents the most important source rock in the Maracaibo Basin. In this way and based on sedimentological and organic geochemistry results from the determinations performed on 247 samples belonging to six cores in the Maracaibo Basin, we propose these two organic-rich levels, deposited on the shallow shelf of the Cogollo Group, as "effective source rocks", additional to La Luna Formation, with oil migration in relatively small distances to the porosity facies.

  3. Ecology and living conditions of groundwater fauna

    Energy Technology Data Exchange (ETDEWEB)

    Thulin, Barbara (Geo Innova AB (Sweden)); Hahn, Hans Juergen (Arbeitsgruppe Grundwasseroekologie, Univ. of Koblenz-Landau (Germany))

    2008-09-15

    This report presents the current state of ecological knowledge and applied research relating to groundwater. A conceptual picture is given of groundwater fauna occurrence in regard to Swedish environmental conditions. Interpretation features for groundwater fauna and applications are outlined. Groundwater is one of the largest and oldest limnic habitats populated by a rich and diverse fauna. Both very old species and species occurring naturally in brackish or salt water can be found in groundwater. Groundwater ecosystems are heterotrophic; the fauna depends on imports from the surface. Most species are meiofauna, 0.3-1 mm. The food chain of groundwater fauna is the same as for relatives in surface water and salt water. Smaller animals graze biofilms and detritus, larger animals act facutatively as predators. A difference is that stygobiotic fauna has become highly adapted to its living space and tolerates very long periods without food. Oxygen is a limiting factor, but groundwater fauna tolerates periods with low oxygen concentrations, even anoxic conditions. For longer periods of time a minimum oxygen requirement of 1 mg/l should be fulfilled. Geographic features such as Quaternary glaciation and very old Pliocene river systems are important for distribution patterns on a large spatial scale, but aquifer characteristics are important on a landscape scale. Area diversity is often comparable to surface water diversity. However, site diversity is low in groundwater. Site specific hydrological exchange on a geological facies level inside the aquifer, e.g. porous, fractured and karstic aquifers as well as the hyporheic zone, controls distribution patterns of groundwater fauna. For a better understanding of controlling factors indicator values are suggested. Different adequate sampling methods are available. They are representative for the aquifer, but a suitable number of monitoring wells is required. The existence of groundwater fauna in Sweden is considered as very

  4. Anoxic survival potential of bivalves: (arte)facts.

    Science.gov (United States)

    de Zwaan, Albertus; Babarro, Jose M F; Monari, Marta; Cattani, Otello

    2002-03-01

    The anoxic survival time of the bivalves Chamelea gallina, Cerastoderma edule and Scapharca inaequivalvis from two different ecosystems and differing anoxia tolerances was studied in static (closed) and flow-through systems. The antibiotics chloramphenicol, penicillin and polymyxin were added, and molybdate (specific inhibitor of the process of sulfate reduction). Survival in (near) anoxic seawater of Chamelea was studied in a static system by comparing untreated seawater with autoclaved seawater and untreated clams with clams incubated in well-aerated seawater, containing the broad-spectrum antibiotic chloramphenicol, prior to the anoxic survival test. With untreated clams and natural seawater (median mortality time 2.4 days) a decrease in pH and exponential accumulation of sulfide and ammonium was observed in the anoxic medium, indicating excessive growth of (sulfate reducing) bacteria. In sterilized seawater LT50 (2.1 days) was not significantly different and again considerable amounts of ammonium and sulfide accumulated. However, pre-treatment of clams with chloramphenicol resulted in an increase of LT50 (11.0 days) by approximately fivefold. Accumulation of ammonium and sulfide was retarded, but was finally even stronger than in the medium containing untreated clams. Median mortality times were 2.5 and 2.4 days for Chamelea and 2.7 and 2.9 days for Cerastoderma for static and flow-through incubations, respectively. Addition of chloramphenicol increased strongly survival time in both systems with corresponding values of 11.0 and 16.3 days for Chamelea, and 6.4 and 6.5 days for Cerastoderma. LT50 of Scapharca in anoxic seawater was 14.4 days. Chloramphenicol and penicillin increased median survival time to 28.5 and 28.7 days, respectively, whereas polymyxin displayed no effect (LT50=13.6 days). Molybdate added to artificial sulfate free seawater blocked biotic sulfide formation, but did not improve survival time (LT50=13.7 days). Overall the results indicate

  5. Technetium diffusion in clay-based materials under oxic and anoxic conditions. AECL research No. AECL-11419

    Energy Technology Data Exchange (ETDEWEB)

    Hume, H.B.

    1995-12-31

    Describes experiments to determine diffusion coefficients for technetium in compacted clay-based material (soils) saturated with a synthetic groundwater solution whose principal ions were calcium, sodium, and chlorine. Tests were conducted in anoxic conditions established by conducting the experiments in a low- oxygen glove box and by mixing 0.5% by weight of powdered iron with the soils (Lake Agassiz clay and a 1:3 mix of dry mass of clay and crushed granite aggregate). Effective diffusion coefficients were also measured in oxic conditions in Avonlea bentonite, Lake Agassiz clay, and illite/smectite. Implications of the results for transport of radionuclides through backfill material and clay barriers used in underground disposal of nuclear fuel waste are discussed.

  6. Multi-proxy study of Ocean Anoxic Event 2 (Cenomanian-Turonian) yields new perspective on the drivers for Mesozoic anoxic events

    Science.gov (United States)

    Sageman, B. B.; Hurtgen, M.; Jacobson, A. D.; Selby, D. S.

    2015-12-01

    Mesozoic ocean anoxic events have long been a focus of intense study because they appear to reflect a large-scale oscillation of the marine redox state from oxic to anoxic, and at least locally sulfidic. The consensus view on the cause of these events has changed over the past 39 years, since they were first defined. A global net increase in primary production is now widely accepted as the key driver, and the evidence for a volcanic trigger of this process is strong. However, the exact pathway from volcanism to OAE is less certain. Some authors favor the direct role of a massive load of reduced compounds in LIP hydrothermal fluxes for consuming available marine oxygen. Others prefer the indirect pathway of oxygen consumption by enhanced organic matter flux, which requires a major increase in nutrient budgets. Metallic micronutrients in the hydrothermal fluxes have been hypothesized, as have increases in riverine phosphorus fluxes due to enhanced weathering that would result from volcanic CO2 driven warming. Our recent work on the OAE2 interval has led to some new ideas about these hypothesized drivers. In particular, refinement of the Late Cenomanian time scale, and comparison of the geochemical records of d13C, d34S, Osi, P phases, and d44Ca between selected sections in North America and Europe has suggested the following sequence of events: 1) Osi data indicate that the onset of a major volcanic event precedes the positive shift in C-isotopes by at least 40 to possibly 180 kyr; 2) a positive shift in d44Ca data interpreted to indicate ocean acidification is coincident with the volcanic event; 3) the positive shift in C-isotopes is interpreted to reflect the accumulated burial of marine organic matter sufficient to shift the C-reservoir to heavier values; thus, our data suggest that up to 180 kyr was required for the shift in nutrient supply, productivity increase, and organic matter burial. Two mechanisms that conceivably match the lagged character of the event

  7. Alpine Groundwater - Pristine Aquifers Under Threat?

    Science.gov (United States)

    Schneider, P.; Lange, A.

    2014-12-01

    Glacier and permafrost retreat are prominent climate change indicators. However, the characteristics of climate and hydrology in mountain areas remain poorly understood relative to lowland areas. Specifically, not much is known about alpine groundwater, its recharge and water quality variations, as these remote reservoirs are rarely monitored. As global temperatures rise, glaciers and permafrost will continue to retreat forming new sediment deposits and changing infiltration conditions in high alpine terrain. Climate change impacts the hydro-chemical composition of alpine waters, accelerates weathering processes, and potentially triggers mobilization of pollutants. Accordingly, we monitored groundwater quantity and quality parameters of an alpine porous aquifer near the Tiefenbach glacier in the Gotthard Massif in Switzerland. The goal of this research was to assess quality and seasonal storage dynamics of groundwater above the timberline (2000 m). To translate hydrological science into an ecosystem service context, we focused on four attributes: Water quantity: observations of groundwater level fluctuations combined with analysis of contributing water sources based on stable isotope analysis to give a quantitative understanding of origin and amount of water, Water quality: groundwater level, groundwater temperature and electrical conductivity were used as proxies for sampling of hydro-chemical parameters with automated water samplers during primary groundwater recharge periods (snowmelt and rainfall events), Location: Alpine terrain above the timberline, especially recharge into/out of an alpine porous aquifer at a pro-glacial floodplain and Date of annual melt (albedo effect) and timing of flow (snow- and icemelt from May to September) and groundwater recharge during the growing season. The study found that the summer groundwater temperatures depend on the date of annual melt and are more sensitive to climate forcing than lowland groundwater temperatures

  8. A High-Resolution Porphyrin Nitrogen Isotope Record of an Oceanic Anoxic Event

    Science.gov (United States)

    Pearson, A.; Higgins, M. B.; Robinson, R. S.; Carter, S. J.

    2010-12-01

    Nitrogen isotope values measured in sediments deposited at times of widespread marine suboxic conditions are consistently more depleted in 15N than are modern marine sediments. We measured a high-resolution δ15N record of sedimentary porphyrins from a section spanning the Cenomanian-Turonian Oceanic Anoxic Event (OAE) II to examine changes in the nitrogen cycle recorded in surface waters. We compare these values to δ15N values of three sedimentary fractions: bulk sediment, extractable organic matter (bitumen), and non-extractable organic matter (kerogen). All fractions record similar trends; are offset from each other by consistent differences that are reflective of algal (not cyanobacterial) export; and are depleted in 15N compared to modern sedimentary samples, both before, during, and after the interval defined by the OAE. Prior to the termination of OAE II, there is a slight further negative excursion in δ15N values. In order to interpret these and other depleted δ15N values measured in similar black shales, we invoke a nitrogen isotope model that considers the importance of redox transformations of N under suboxic conditions. This model invokes an ocean in which the deep N reservoir is dominated by NH4+, limited nitrification occurs in the photic zone, and chemocline denitrification acts as a quantitative sink for downwelling nitrate. Although in this model a large component of net production may be fueled by N fixation, N fixation alone cannot generate biomass with δ15N values as depleted as are seen in many Mesozoic OAE sections. We postulate that throughout the Phanerozoic, excursions leading to negative values of d15N reflect relatively low rates of nitrosification relative to the sum of NH4+ utilization and N fixation.

  9. Persistence of Carbonate Platform Environments in Central Mexico during the Oceanic Anoxic Event 2: impact of the Carribean Plateau?

    Science.gov (United States)

    Bomou, Brahimsamba; Adatte, Thierry; Föllmi, Karl; Arnaud-Vanneau, Annie; Fleitmann, Dominik

    2010-05-01

    The Cenomanian-Turonian Oceanic Anoxic Event 2 is described as an interruption of normal pelagic sediment deposition by several distinct intervals of widespread oceanic anoxia (Schlanger & Jenkyns, 1976; Jenkyns, 1980; Arthur et al., 1990) characterized by black shales deposition coinciding with a positive shift in carbon isotope excursion. Some authors show a relationship between OAEs and massive volcanic events associated with the emplacement of large igneous provinces (LIPs) and sea floor spreading at mid-ocean ridges (Kuroda et al., 2007; Snow et al., 2005). High metal abundance anomalies recorded in pelagic sections (e.g. Pueblo, Colorado) coincide with the massive volcanism that built the Carribean plateau (around 93-94 Ma), associated with the onset of OAE 2 (Snow et al., 2005). Mort et al., (2007) demonstrate that the onset of the OAE 2 was triggered by a short-lived but significant increase in phosphorus burial. The bottom waters became anoxic and switched from being a P sink to a P source, sustaining the productivity in a positive feedback loop. However, the behaviour of phosphorus and trace metals at larger scale, in different paleogeography and paleodepht is still poorly known. The Axaxacualco and Baranca el Cañon sections, located at the Guerrero-Morelos carbonate platform in southern Mexico exhibit a fully correlateable d13C curves. In the distal part of the carbonate platform at Axaxacualco, the maximum d13C positive excursion coincides with oligotrophic carbonate platform environments supported by low concentrations in P and characterized by abundant and diversified benthic microfauna and rudists. The impact of OAE appears may be more significant in the proximal part of the carbonate platform at Barranca, characterized by the deposition of thick laminated microbialites indicative of mesotrophic conditions. The Morelos Carbonate platform with oligotrophic to mesotrophic conditions was persistent throughout the entire OAE2 in Central Mexico despite

  10. High sensitivity of Lobelia dortmanna to sediment oxygen depletion following organic enrichment

    DEFF Research Database (Denmark)

    Møller, Claus Lindskov; Jensen, Kaj Sand

    2011-01-01

    sediments. • We added organic matter to sediments and followed O(2) dynamics in plants and sediments using microelectrodes. To investigate plant stress, nutrient content and photosynthetic capacity of leaves were measured. • Small additions of organic matter triggered O(2) depletion and accumulation of NH(4......• Lobelia dortmanna thrives in oligotrophic, softwater lakes thanks to O(2) and CO(2) exchange across roots and uptake of sediment nutrients. We hypothesize that low gas permeability of leaves constrains Lobelia to pristine habitats because plants go anoxic in the dark if O(2) vanishes from...... thresholds for cell function in enriched sediments and was accompanied by critically low chlorophyll and photosynthesis. • We propose that anoxic stress restricts ATP formation and constrains transfer of nutrients to leaves. Brief anoxia in sediments and leaf lacunae late at night is a recurring summer...

  11. Rapid changes in the redox conditions of the western Tethys Ocean during the early Aptian oceanic anoxic event

    Science.gov (United States)

    Westermann, Stéphane; Stein, Melody; Matera, Virginie; Fiet, Nicolas; Fleitmann, Dominik; Adatte, Thierry; Föllmi, Karl B.

    2013-11-01

    The early Aptian (125 to 121 Ma) records an episode of severe environmental change including a major perturbation of the carbon cycle, an oceanic anoxic event (OAE 1a, 122.5 Ma), a platform drowning episode and a biocalcification crisis. We propose to trace changes in the oxygenation state of the ocean during the early Aptian anoxic event using the redox-sensitive trace-element (RSTE) distribution, phosphorus accumulation rates (PARs) and organic-matter characterization in three different basins of the western Tethys. The following sections have been investigated: Gorgo a Cerbara (central Italy) in the Umbria Marche basin, Glaise (SE France) in the Vocontian basin and Cassis/La Bédoule (SE France) located in the Provencal basin. In the Gorgo a Cerbara section, RSTE distributions show a low background level along the main part of the section, contrasted by different maxima in concentrations within the Selli level. In the Glaise section, the Goguel level displays a weak increase in RSTE contents coeval with moderate TOC values. At Cassis/La Bédoule, no significant RSTE enrichments have been observed in sediments equivalent to the Selli level. These differences in the records of the geochemical proxies of the Selli level or its equivalent indicate the deposition under different redox conditions, probably related to the paleogeography. Our data indicate the development of anoxic-euxinic conditions in the deeper part of the Tethys during OAE 1a, whereas in the shallower environments, conditions were less reducing. Moreover, at Gorgo a Cerbara, the Selli level is characterized by rapid changes in the intensity of reducing conditions in the water column. Ocean eutrophication seems to be a major factor in the development and the persistence of anoxia as suggested by the PAR evolution. Higher PAR values at the onset of OAE 1a suggest an increase in nutrient input, whereas the return to lower values through the first part of the OAE 1a interval may be related to the

  12. Anoxic Activated Sludge Monitoring with Combined Nitrate and Titrimetric Measurements

    DEFF Research Database (Denmark)

    Petersen, B.; Gernaey, Krist; Vanrolleghem, P.A.

    2002-01-01

    An experimental procedure for anoxic activated sludge monitoring with combined nitrate and titrimetric measurements is proposed and evaluated successfully with two known carbon sources, (-)acetate and dextrose. For nitrate measurements an ion-selective nitrate electrode is applied to allow...... was with the carbon source in excess, since excess nitrate provoked nitrite build-up thereby complicating the data interpretation. A conceptual model could quantitatively describe the experimental observations and thus link the experimentally measured proton production with the consumption of electron acceptor...... and carbon source during denitrification....

  13. Modeling biogeochemical processes in subterranean estuaries : Effect of flow dynamics and redox conditions on submarine groundwater discharge of nutrients

    NARCIS (Netherlands)

    Spiteri, C.; Slomp, C.P.; Tuncay, K.; Meile, C.

    2008-01-01

    A two-dimensional density-dependent reactive transport model, which couples groundwater flow and biogeochemical reactions, is used to investigate the fate of nutrients (NO3 −, NH4 +, and PO4) in idealized subterranean estuaries representing four end-members of oxic/anoxic aquifer and seawater redox

  14. Mercury methylation by a microbial community from sediments of the Adour Estuary (Bay of Biscay, France)

    Energy Technology Data Exchange (ETDEWEB)

    Duran, R. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France)], E-mail: robert.duran@univ-pau.fr; Ranchou-Peyruse, M.; Menuet, V. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Monperrus, M.; Bareille, G. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France); Goni, M.S.; Salvado, J.C. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Amouroux, D. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France); Guyoneaud, R. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Donard, O.F.X. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France)] (and others)

    2008-12-15

    In order to study the influence of microorganisms on the mercury biogeochemistry, the metal content and the structure of microbial communities were determined in sediments from stations along the Adour Estuary. The comparison of the bacterial communities and their distribution in function of the environmental parameters by Canonical Correspondence Analysis (CCA) revealed the influence of metals on the bacterial communities structure. Sediments where the bacterial communities are mostly influenced by methylmercury were incubated in slurries with or without mercury, under oxic and anoxic conditions. Methylmercury production was detected in the anoxic biotic slurries with a net methylation yield of 0.3% after 24 h. CCA based on T-RFLP profiles revealed the impact of mercury addition on the bacterial communities structure. In addition, 17 bacterial strains, mainly sulphate-reducing bacteria involved in mercury methylation, were isolated and identified. - Role of oxic/anoxic cycles and microbial activities on the methylmercury formation in Adour (France) estuarine sediments.

  15. Wave-Induced Groundwater Flows in a Freshwater Beach Aquifer

    Science.gov (United States)

    Malott, S. S.; Robinson, C. E.; O'Carroll, D. M.

    2014-12-01

    Wave-induced recirculation across the sediment-water interface can impact the transport of pollutants through a beach aquifer and their ultimate flux into coastal waters. The fate of nutrients (e.g. from septic and agricultural sources) and fecal indicator bacteria (e.g. E. coil) near the sediment-water interface are of particular concern as these pollutants often lead to degradation of recreational water quality and nearshore ecosystems. This paper presents detailed field measurements of groundwater flows in a freshwater beach aquifer on Lake Huron over periods of intensified wave conditions. Quantifying wave-driven processes in a freshwater beach aquifer enables wave effects to be studied in isolation from density and tidal effects that complicate groundwater flows in marine beaches. Water exchange across the sediment-water interface and groundwater flow patterns were measured using groundwater wells, arrays of vertically nested pressure transducers and manometers. Results show that wave action induces rapid infiltration/exfiltration across the sediment-water interface and a larger recirculation cell through the beach aquifer. Field data is used to validate a numerical groundwater model of wave-induced groundwater flows. While prior studies have simulated the effects of waves on beach groundwater flows, this study is the first attempt to validate these sophisticated modeling approaches. Finally, field data illustrating the impact of wave-induced groundwater flows on nutrient and bacteria fate and transport in beach aquifers will also be presented.

  16. Temperature-driven decoupling of key phases of organic matter degradation in marine sediments

    OpenAIRE

    Weston, Nathaniel B.; Joye, Samantha B.

    2005-01-01

    The long-term burial of organic carbon in sediments results in the net accumulation of oxygen in the atmosphere, thereby mediating the redox state of the Earth's biosphere and atmosphere. Sediment microbial activity plays a major role in determining whether particulate organic carbon is recycled or buried. A diverse consortium of microorganisms that hydrolyze, ferment, and terminally oxidize organic compounds mediates anaerobic organic matter mineralization in anoxic sediments. Variable tempe...

  17. The impact of electrogenic sulfide oxidation on elemental cycling and solute fluxes in coastal sediment

    OpenAIRE

    Rao, A.M.F.; Malkin, S.Y.; Hidalgo-Martinez, S.; Meysman, Filip

    2016-01-01

    Filamentous sulfide oxidizing cable bacteria are capable of linking the oxidation of free sulfide in deep anoxic layers of marine sediments to the reduction of oxygen or nitrate in surface sediments by conducting electrons over centimeter-scale distances. Previous studies have shown that this newly discovered microbial process, referred to as electrogenic sulfide oxidation (e-SOx), may alter elemental cycling in sediments, but the nature and rates of the resulting biogeochemical transformatio...

  18. Halon-1301, a new Groundwater Age Tracer

    Science.gov (United States)

    Beyer, Monique; van der Raaij, Rob; Morgenstern, Uwe; Jackson, Bethanna

    2015-04-01

    Groundwater dating is an important tool to assess groundwater resources in regards to direction and time scale of groundwater flow and recharge and to assess contamination risks and manage remediation. To infer groundwater age information, a combination of different environmental tracers, such as tritium and SF6, are commonly used. However ambiguous age interpretations are often faced, due to a limited set of available tracers and limitations of each tracer method when applied alone. There is a need for additional, complementary groundwater age tracers. We recently discovered that Halon-1301, a water soluble and entirely anthropogenic gaseous substance, may be a promising candidate [Beyer et al, 2014]. Halon-1301 can be determined along with SF6, SF5CF3 and CFC-12 in groundwater using a gas chromatography setup with attached electron capture detector developed by Busenberg and Plummer [2008]. Halon-1301 has not been assessed in groundwater. This study assesses the behaviour of Halon-1301 in water and its suitability as a groundwater age tracer. We determined Halon-1301 in 17 groundwater and various modern (river) waters sites located in 3 different groundwater systems in the Wellington Region, New Zealand. These waters have been previously dated with tritium, CFC-12, CFC-11 and SF6 with mean residence times ranging from 0.5 to over 100 years. The waters range from oxic to anoxic and some show evidence of CFC contamination or degradation. This allows us to assess the different properties affecting the suitability of Halon-1301 as groundwater age tracer, such as its conservativeness in water and local contamination potential. The samples are analysed for Halon-1301 and SF6simultaneously, which allows identification of issues commonly faced when using gaseous tracers such as contamination with modern air during sampling. Overall we found in the assessed groundwater samples Halon-1301 is a feasible new groundwater tracer. No sample indicated significantly elevated

  19. Environmental magnetism of the Toarcian Oceanic Anoxic Event at Peniche (Portugal)

    Science.gov (United States)

    Font, Eric; Vitor Duarte, Luis; Adatte, Thierry; Mirão, José

    2016-04-01

    The Pliensbachian-Toarcian section of Peniche has been recently selected as the global stratotype section and point for this time interval. It represents one of the best examples of the record of the oceanic anoxic event (OAE) in the world. Here we conducted a detailed a magnetostratigraphic and environmental study in order to improve the time-scale calibration and to provide new magnetic markers for period of oceanic anoxia recorded in marine sediments. Our results show that the magnetic signal is carried by very low coercive magnetic minerals and exhibit unstable and unreliable data for magnetostratigraphic investigation. In counterpart, bulk magnetic properties (magnetic susceptibility, isothermal remanent magnetization curves, etc) coupled to Scanning Electron Microscopy (SEM) show a striking negative correlation with carbonate content and 13DC previously published in the literature. Particularly, the most pronounced negative C isotopic composition of the OAE interval correlates with high magnetic susceptibility values. SEM-EDS analysis show that the strata featured by high MS values contain ubiquitous pyrite and greigite framboids. These insights provide new markers to identify the magnetic signature of OAE in the marine record. Funded by IDL (FCT UID/GEO/50019/2013)

  20. Profiling bacterial communities associated with sediment-based aquaculture bioremediation systems under contrasting redox regimes

    Science.gov (United States)

    Robinson, Georgina; Caldwell, Gary S.; Wade, Matthew J.; Free, Andrew; Jones, Clifford L. W.; Stead, Selina M.

    2016-12-01

    Deposit-feeding invertebrates are proposed bioremediators in microbial-driven sediment-based aquaculture effluent treatment systems. We elucidate the role of the sediment reduction-oxidation (redox) regime in structuring benthic bacterial communities, having direct implications for bioremediation potential and deposit-feeder nutrition. The sea cucumber Holothuria scabra was cultured on sediments under contrasting redox regimes; fully oxygenated (oxic) and redox stratified (oxic-anoxic). Taxonomically, metabolically and functionally distinct bacterial communities developed between the redox treatments with the oxic treatment supporting the greater diversity; redox regime and dissolved oxygen levels were the main environmental drivers. Oxic sediments were colonised by nitrifying bacteria with the potential to remediate nitrogenous wastes. Percolation of oxygenated water prevented the proliferation of anaerobic sulphate-reducing bacteria, which were prevalent in the oxic-anoxic sediments. At the predictive functional level, bacteria within the oxic treatment were enriched with genes associated with xenobiotics metabolism. Oxic sediments showed the greater bioremediation potential; however, the oxic-anoxic sediments supported a greater sea cucumber biomass. Overall, the results indicate that bacterial communities present in fully oxic sediments may enhance the metabolic capacity and bioremediation potential of deposit-feeder microbial systems. This study highlights the benefits of incorporating deposit-feeding invertebrates into effluent treatment systems, particularly when the sediment is oxygenated.

  1. Profiling bacterial communities associated with sediment-based aquaculture bioremediation systems under contrasting redox regimes

    Science.gov (United States)

    Robinson, Georgina; Caldwell, Gary S.; Wade, Matthew J.; Free, Andrew; Jones, Clifford L. W.; Stead, Selina M.

    2016-01-01

    Deposit-feeding invertebrates are proposed bioremediators in microbial-driven sediment-based aquaculture effluent treatment systems. We elucidate the role of the sediment reduction-oxidation (redox) regime in structuring benthic bacterial communities, having direct implications for bioremediation potential and deposit-feeder nutrition. The sea cucumber Holothuria scabra was cultured on sediments under contrasting redox regimes; fully oxygenated (oxic) and redox stratified (oxic-anoxic). Taxonomically, metabolically and functionally distinct bacterial communities developed between the redox treatments with the oxic treatment supporting the greater diversity; redox regime and dissolved oxygen levels were the main environmental drivers. Oxic sediments were colonised by nitrifying bacteria with the potential to remediate nitrogenous wastes. Percolation of oxygenated water prevented the proliferation of anaerobic sulphate-reducing bacteria, which were prevalent in the oxic-anoxic sediments. At the predictive functional level, bacteria within the oxic treatment were enriched with genes associated with xenobiotics metabolism. Oxic sediments showed the greater bioremediation potential; however, the oxic-anoxic sediments supported a greater sea cucumber biomass. Overall, the results indicate that bacterial communities present in fully oxic sediments may enhance the metabolic capacity and bioremediation potential of deposit-feeder microbial systems. This study highlights the benefits of incorporating deposit-feeding invertebrates into effluent treatment systems, particularly when the sediment is oxygenated. PMID:27941918

  2. Phosphorus recycling and burial in Baltic Sea sediments with contrasting redox conditions

    DEFF Research Database (Denmark)

    Mort, Haydon P; Slomp, Caroline P; Gustafson, Bo G

    2010-01-01

    -day bottom water redox conditions range from fully oxygenated and seasonally hypoxic to almost permanently anoxic and sulfidic. Strong surface enrichments of Fe-oxide bound P are observed at oxic and seasonally hypoxic sites but not in the anoxic basins. Reductive dissolution of Fe-oxides and release...... primary productivity. Historical records of bottom water oxygen at two sites (Bornholm, Northern Gotland) show a decline over the past century and are accompanied by a rise in values for typical sediment proxies for anoxia (total sulfur, molybdenum and organic C/P ratios). While sediment reactive P...

  3. Metals in tissues of seabass and seabream reared in sites with oxic and anoxic substrata and risk assessment for consumers.

    Science.gov (United States)

    Kalantzi, I; Pergantis, S A; Black, K D; Shimmield, T M; Papageorgiou, N; Tsapakis, M; Karakassis, I

    2016-03-01

    Twenty-eight metals and elements were measured in the muscle, liver, gills, bone and intestine of farmed seabass and gilthead seabream from four Mediterranean fish farms. The influence of fish species and the effect of environmental conditions on the metal accumulation in fish tissues was investigated. Most concentrations were lower in muscle and higher in liver and bone than in other body tissues. Seabass accumulates more elements in its tissues than seabream. Fish reared in coarse, oxic sites accumulate more elements with higher concentrations in muscle, bone and intestine and with lower concentrations in liver and gills than fish reared in silty, anoxic sites. This may be attributed to feed type and sediment properties. According to the metal pollution index, hazard quotient, selenium health benefit values, carcinogenic risk of arsenic, maximum safe consumption and the permitted limits, the consumption of both farmed species should be considered as safe for human health.

  4. Cadmium-isotopic evidence for increasing primary productivity during the Late Permian anoxic event

    Science.gov (United States)

    Georgiev, Svetoslav V.; Horner, Tristan J.; Stein, Holly J.; Hannah, Judith L.; Bingen, Bernard; Rehkämper, Mark

    2015-01-01

    Earth's most extreme extinction event near the end of the Late Permian decimated more than 90% of all extant marine species. Widespread and intensive oceanic anoxia almost certainly contributed to the catastrophe, though the driving mechanisms that sustained such conditions are still debated. Of particular interest is whether water column anoxia was a consequence of a 'stagnant ocean', or if it was controlled by increases in nutrient supply, primary productivity, and subsequent heterotrophic respiration. Testing these competing hypotheses requires deconvolving sedimentary/bottom water redox conditions from changes in surface water productivity in marine sediments. We address this issue by studying marine shales from East Greenland and the mid-Norwegian shelf and combining sedimentary redox proxies with cadmium-isotopic analyses. Sedimentary nitrogen-isotopic data, pyrite framboid analyses, and organic and inorganic shale geochemistry reveal sulfidic conditions with vigorous upwelling, and increasingly anoxic conditions with a strengthening upwelling in the Greenland and Norwegian sections, respectively. Detailed analysis of sedimentary metal budgets illustrates that Cd is primarily associated with organic carbon and records primary geochemical signatures, thus enabling reconstruction of surface water nutrient utilization. Cadmium-isotopic analyses of the authigenic shale fraction released by inverse aqua regia digestion yield an average δ114Cd110 of + 0.15 ± 0.01 ‰ (2 SE, n = 12; rel. NIST SRM 3108), indicative of incomplete surface water nutrient utilization up-section. The constant degree of nutrient utilization combined with strong upwelling requires increasing primary productivity - and not oceanic stagnation - to balance the larger nutrient fluxes to both study sites during the development of the Late Permian water column anoxia. Overall, our data illustrate that if bottom water redox and upwelling can be adequately constrained, Cd-isotopic analyses of

  5. Groundwater Waters

    Directory of Open Access Journals (Sweden)

    Ramón Llamas

    1999-10-01

    Full Text Available The groundwaters released through springs constituted a basic element for the survival and progressive development of human beings. Man came to learn how to take better advantage of these waters by digging wells, irrigation channels, and galleries. Nevertheless, these activities do not require cooperation nor the collective agreement of relatively large groups of people, as in the case of creating the necessary structures to take advantage of the resources of surfacewaters. The construction and operation of these structures was a powerful factor in the birth of an urban or civil society – the designated water civilizations. The difference between people taking advantage of groundwater, quasi-individually, and those of surface water, where people work in a group, has continued to the present day. Whereas earlier, this difference did not bring about any special problems, the technological advances of this century, especially theturbine pump, have led to a spectacular increase in the use of roundwater. This advance has significantly contributed to reducing hunger in the world and has provided potable water in developing countries. However, the almost generalized lack of planning and control in the exploitation of these groundwaters reflects that they are little or badly understood by the managers of water policy in almost every country. As such, problems have occurred which have often become exaggerated, giving rise to water-myths. These problems, though, should be addressed if the aim is the sustainable usage of surface water as well as groundwater. To counter any misconceptions and to seek solutions to the problems, distinct plans of action can be highlighted: educating the public; fomenting a system of participative management and decisive support for the communities of users of subterranean waters; integrating a sufficient number of experts in hydrology in the various water management organizations;and assuring transparency of the data on

  6. Kinetic and stoichiometric characterization of anoxic sulfide oxidation by SO-NR mixed cultures from anoxic biotrickling filters.

    Science.gov (United States)

    Mora, Mabel; Fernández, Maikel; Gómez, José Manuel; Cantero, Domingo; Lafuente, Javier; Gamisans, Xavier; Gabriel, David

    2015-01-01

    Monitoring the biological activity in biotrickling filters is difficult since it implies estimating biomass concentration and its growth yield, which can hardly be measured in immobilized biomass systems. In this study, the characterization of a sulfide-oxidizing nitrate-reducing biomass obtained from an anoxic biotrickling filter was performed through the application of respirometric and titrimetric techniques. Previously, the biomass was maintained in a continuous stirred tank reactor under steady-state conditions resulting in a growth yield of 0.328 ± 0.045 g VSS/g S. To properly assess biological activity in respirometric tests, abiotic assays were conducted to characterize the stripping of CO2 and sulfide. The global mass transfer coefficient for both processes was estimated. Subsequently, different respirometric tests were performed: (1) to solve the stoichiometry related to the autotrophic denitrification of sulfide using either nitrate or nitrite as electron acceptors, (2) to evaluate the inhibition caused by nitrite and sulfide on sulfide oxidation, and (3) to propose, calibrate, and validate a kinetic model considering both electron acceptors in the overall anoxic biodesulfurization process. The kinetic model considered a Haldane-type equation to describe sulfide and nitrite inhibitions, a non-competitive inhibition to reflect the effect of sulfide on the elemental sulfur oxidation besides single-step denitrification since no nitrite was produced during the biological assays.

  7. Jurassic carbonate microfacies, sea-level changes and the Toarcian anoxic event in the Tethys Himalaya (South Tibet)

    Science.gov (United States)

    Han, Zhong; Hu, Xiumian; Garzanti, Eduardo

    2016-04-01

    Detailed microfacies analysis of carbonate rocks from the Tingri and Nyalam areas of South Tibet allowed us to reconstruct the evolution of sedimentary environments during the Early to Middle Jurassic. Based on texture, sedimentary structure, grain composition and fossil content of about 500 thin sections, 17 microfacies overall were identified, and three evolutionary stages were defined. Stage 1 (Rhaetian?-lower Sinemurian Zhamure Formation) was characterized by siliciclastic and mixed siliciclastic-carbonate sedimentation on a barrier shore environment, stage 2 (upper Sinemurian-Pliensbachian Pupuga Formation) by high-energy grainstones with rich benthic faunas thriving on a carbonate platform, and stage 3 (Toarcian-lower Bajocian Nieniexiongla Formation) by low-energy mudstones intercalated with frequent storm layers on a carbonate ramp. Besides, Carbon isotope analyses (δ13Ccarb and δ13Corg) were performed on the late Pliensbachian-early Toarcian interval, and the organic matter recorded a pronounced stepped negative excursion -4.5‰ corresponding to characteristics of the early Toarcian oceanic anoxic event globally, which began just below the stage 2-stage 3 facies shifting boundary. The comparison between the Tethys Himalaya (South Tibet) and the tropical/subtropical zones of the Western Tethys and Panthalassa was carried out to discuss the factors controlling sedimentary evolution. The change from stage 1 to stage 2 was possibly induced by sea-level rise, when the Tibetan Tethys Himalaya was located at tropical/subtropical latitudes in suitable climatic and ecological conditions for carbonate sedimentation. The abrupt change from stage 2 to stage 3 is interpreted as a consequence of the early Toarcian oceanic anoxic event, accompanied by obvious carbon-isotope negative excursion and sea-level rise. The failed recovery from the carbonate crisis in the early Bajocian, with continuing deposition on a low-energy carbonate ramp, is ascribed to the tectonic

  8. Cable Bacteria in Freshwater Sediments.

    Science.gov (United States)

    Risgaard-Petersen, Nils; Kristiansen, Michael; Frederiksen, Rasmus B; Dittmer, Anders Lindequist; Bjerg, Jesper Tataru; Trojan, Daniela; Schreiber, Lars; Damgaard, Lars Riis; Schramm, Andreas; Nielsen, Lars Peter

    2015-09-01

    In marine sediments cathodic oxygen reduction at the sediment surface can be coupled to anodic sulfide oxidation in deeper anoxic layers through electrical currents mediated by filamentous, multicellular bacteria of the Desulfobulbaceae family, the so-called cable bacteria. Until now, cable bacteria have only been reported from marine environments. In this study, we demonstrate that cable bacteria also occur in freshwater sediments. In a first step, homogenized sediment collected from the freshwater stream Giber Å, Denmark, was incubated in the laboratory. After 2 weeks, pH signatures and electric fields indicated electron transfer between vertically separated anodic and cathodic half-reactions. Fluorescence in situ hybridization revealed the presence of Desulfobulbaceae filaments. In addition, in situ measurements of oxygen, pH, and electric potential distributions in the waterlogged banks of Giber Å demonstrated the presence of distant electric redox coupling in naturally occurring freshwater sediment. At the same site, filamentous Desulfobulbaceae with cable bacterium morphology were found to be present. Their 16S rRNA gene sequence placed them as a distinct sister group to the known marine cable bacteria, with the genus Desulfobulbus as the closest cultured lineage. The results of the present study indicate that electric currents mediated by cable bacteria could be important for the biogeochemistry in many more environments than anticipated thus far and suggest a common evolutionary origin of the cable phenotype within Desulfobulbaceae with subsequent diversification into a freshwater and a marine lineage.

  9. Influence of different anoxic time exposures on active biomass, protozoa and filamentous bacteria in activated sludge.

    Science.gov (United States)

    Rodriguez-Perez, S; Fermoso, F G; Arnaiz, C

    Medium-sized wastewater treatment plants are considered too small to implement anaerobic digestion technologies and too large for extensive treatments. A promising option as a sewage sludge reduction method is the inclusion of anoxic time exposures. In the present study, three different anoxic time exposures of 12, 6 and 4 hours have been studied to reduce sewage sludge production. The best anoxic time exposure was observed under anoxic/oxic cycles of 6 hours, which reduced 29.63% of the biomass production compared with the oxic control conditions. The sludge under different anoxic time exposures, even with a lower active biomass concentration than the oxic control conditions, showed a much higher metabolic activity than the oxic control conditions. Microbiological results suggested that both protozoa density and abundance of filamentous bacteria decrease under anoxic time exposures compared to oxic control conditions. The anoxic time exposures 6/6 showed the highest reduction in both protozoa density, 37.5%, and abundance of filamentous bacteria, 41.1%, in comparison to the oxic control conditions. The groups of crawling ciliates, carnivorous ciliates and filamentous bacteria were highly influenced by the anoxic time exposures. Protozoa density and abundance of filamentous bacteria have been shown as promising bioindicators of biomass production reduction.

  10. Anoxia and the nitrogen cycle during Cretaceous Oceanic Anoxic Event 1a (~120 Ma): a data-model comparison

    Science.gov (United States)

    Naafs, B. D.; Monteiro, F. M.; Froehner, S.; Lowson, C.; Quijano, M.; Castro, J.; Donnadieu, Y.; Schmidt, D. N.; Ridgwell, A. J.; Pancost, R. D.

    2013-12-01

    The Oceanic Anoxic Events (OAEs) of the Mesozoic are among the most dramatic examples of water column oxygen depletion in Earth's history. OAEs were likely characterized by high rates of denitrification and a profoundly different marine nitrogen cycle than that of today. High abundances of 2-methylhopane biomarkers commonly occur in OAE sediments, especially OAE 1a, and are often interpreted to reflect a major increase in the (relative) abundance of N2-fixing cyanobacteria (e.g., Kuypers et al., 2004). However the spatial extent of these postulated cyanobacterial blooms, control of water column anoxia on their occurrence, and impact on the nitrogen cycle is not well constrained and understood. Combining new data with an intermediate-complexity Earth system model (GENIE), we show that modeled reduced oxygenation of the water column is consistent with the majority of available data for OAE 1a. Increased nutrient availability likely caused widespread bottom water anoxia during OAE 1a, similar to OAE 2 (Monteiro et al., 2012). However, the different paleogeography appears to have prevented widespread expansion of euxinic conditions in the photic zone during OAE 1a, consistent with the general absence of isorenieratane in OAE 1a sediments. A compilation of newly generated and previously published 2-methylhopane biomarker data from the Tethys realm (Cismon core and three newly generated records from southern Spain) and Pacific Ocean (Shatsky Rise, DSDP Site 463, and new data from ODP Site 866) shows that relative abundances of 2-methylhopanes and temporal trends herein differ greatly during OAE 1a, even between proximal sites. Although modeled spatial distribution of nitrogen fixation for OAE1a bears similarity with 2-methylhopanes distributions, distinct differences are present. Altogether these results call into question the assumed effects of periods of anoxia on the nitrogen cycle and suggest that the response of the nitrogen cycle to large perturbations of the

  11. Hydraulic activities by ghost shrimp Neotrypaea californiensis induce oxic-anoxic oscillations in sediments

    Science.gov (United States)

    We applied porewater pressure sensing, time-lapse photography and planar optode imaging of oxygen to investigate hydraulic behaviors of the Thalassinidean ghost shrimp Neotrypaea californiensis and the associated dynamics of oxygen in and around their burrows. Ghost shrimp were h...

  12. Diverse methane concentrations in anoxic brines and underlying sediments, eastern Mediterranean Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Karisiddaiah, S.M.

    *Bannock Basin (CTD 1 and LC 16), U*Urania Basin (CTD 2, LC 17); #*ODP Leg 160 (Site 970, 971) locations; a, b, c and d are"elds of mud diapirs. (a) Prometheus, (b)Pan di Zuchheri, (c)Prometheus and (d) Olimpi (its position is similar to ODP position); IP * Inner...

  13. Early diagenesis and authigenic mineral formation in anoxic sediments of Kau Bay, Indonesia

    NARCIS (Netherlands)

    Middelburg, Jack

    1990-01-01

    Kau Bay (island of Halmahera, Eastern Indonesia) is a 470 m deep basin separated from the Pacific Ocean by a sill that is at present only 40 m below sea-level. The presence of this sill has two major implications. Firstly, during Weichselian time, the sea-level dropped below the depth of the sill, K

  14. Groundwater and security

    NARCIS (Netherlands)

    Conti, K.I.; Kukurić, N.; Gupta, J.; Pahl-Wostl, C.; Bhaduri, A.; Gupta, J.

    2016-01-01

    Humans abstract two hundred times more groundwater than oil, annually. Ironically, the role of groundwater in water management and supply is underappreciated, partially due to its invisibility. By conducting a literature survey and investigating groundwater information databases, this chapter answer

  15. Bruxism Associated with Anoxic Encephalopathy: Successful Treatment with Baclofen

    Science.gov (United States)

    Janati, A. Bruce; ALGhasab, Naif Saad; ALGhassab, Fahad Saad

    2013-01-01

    Introduction. Bruxism is a movement disorder characterized by grinding and clenching of the teeth. Etiology of bruxism can be divided into three groups: psychosocial factors, peripheral factors, and pathophysiological factors. Methods. The clinical investigation was conducted at King Khaled Hospital in Hail, Saudi Arabia, in 2012. Results. A 16-year-old Saudi female was brought to the hospital in a comatose state and with generalized convulsive seizures secondary to acute anoxic encephalopathy. In the third week of hospitalization, while still in a state of akinetic mutism, she developed incessant bruxism which responded favorably to a GABA receptor agonist (baclofen). Conclusion. Our data support the hypothesis that bruxism emanates from imbalance or dysregulation of the neurotransmitter system. Larger scale studies will be needed to confirm this hypothesis. PMID:24455317

  16. Oxygen intrusion into anoxic fjords leads to increased methylmercury availability

    Science.gov (United States)

    Veiteberg Braaten, Hans Fredrik; Pakhomova, Svetlana; Yakushev, Evgeniy

    2013-04-01

    Mercury (Hg) appears in the oxic surface waters of the oceans at low levels (sub ng/L). Because inorganic Hg can be methylated into the toxic and bioaccumulative specie methylmercury (MeHg) levels can be high at the top of the marine food chain. Even though marine sea food is considered the main risk driver for MeHg exposure to people most research up to date has focused on Hg methylation processes in freshwater systems. This study identifies the mechanisms driving formation of MeHg during oxygen depletion in fjords, and shows how MeHg is made available in the surface water during oxygen intrusion. Studies of the biogeochemical structure in the water column of the Norwegian fjord Hunnbunn were performed in 2009, 2011 and 2012. In autumn of 2011 mixing flushing events were observed and lead to both positive and negative effects on the ecosystem state in the fjord. The oxygenated water intrusions lead to a decrease of the deep layer concentrations of hydrogen sulfide (H2S), ammonia and phosphate. On the other hand the intrusion also raised the H2S boundary from 8 m to a shallower depth of just 4 m. Following the intrusion was also observed an increase at shallower depths of nutrients combined with a decrease of pH. Before flushing events were observed concentrations of total Hg (TotHg) increased from 1.3 - 1.7 ng/L in the surface layer of the fjord to concentrations ranging from 5.2 ng/L to 6.4 ng/L in the anoxic zone. MeHg increased regularly from 0.04 ng/L in the surface water to a maximum concentration of 5.2 ng/L in the deeper layers. This corresponds to an amount of TotHg present as MeHg ranging from 2.1 % to 99 %. The higher concentrations of MeHg in the deeper layer corresponds to an area where no oxygen is present and concentrations of H2S exceeds 500 µM, suggesting a production of MeHg in the anoxic area as a result of sulphate reducing bacteria activity. After flushing the concentrations of TotHg showed a similar pattern ranging from 0.6 ng/L in the

  17. Bruxism Associated with Anoxic Encephalopathy: Successful Treatment with Baclofen

    Directory of Open Access Journals (Sweden)

    A. Bruce Janati

    2013-01-01

    Full Text Available Introduction. Bruxism is a movement disorder characterized by grinding and clenching of the teeth. Etiology of bruxism can be divided into three groups: psychosocial factors, peripheral factors, and pathophysiological factors. Methods. The clinical investigation was conducted at King Khaled Hospital in Hail, Saudi Arabia, in 2012. Results. A 16-year-old Saudi female was brought to the hospital in a comatose state and with generalized convulsive seizures secondary to acute anoxic encephalopathy. In the third week of hospitalization, while still in a state of akinetic mutism, she developed incessant bruxism which responded favorably to a GABA receptor agonist (baclofen. Conclusion. Our data support the hypothesis that bruxism emanates from imbalance or dysregulation of the neurotransmitter system. Larger scale studies will be needed to confirm this hypothesis.

  18. Genome-scale dynamic modeling of the competition between Rhodoferax and Geobacter in anoxic subsurface environments.

    Science.gov (United States)

    Zhuang, Kai; Izallalen, Mounir; Mouser, Paula; Richter, Hanno; Risso, Carla; Mahadevan, Radhakrishnan; Lovley, Derek R

    2011-02-01

    The advent of rapid complete genome sequencing, and the potential to capture this information in genome-scale metabolic models, provide the possibility of comprehensively modeling microbial community interactions. For example, Rhodoferax and Geobacter species are acetate-oxidizing Fe(III)-reducers that compete in anoxic subsurface environments and this competition may have an influence on the in situ bioremediation of uranium-contaminated groundwater. Therefore, genome-scale models of Geobacter sulfurreducens and Rhodoferax ferrireducens were used to evaluate how Geobacter and Rhodoferax species might compete under diverse conditions found in a uranium-contaminated aquifer in Rifle, CO. The model predicted that at the low rates of acetate flux expected under natural conditions at the site, Rhodoferax will outcompete Geobacter as long as sufficient ammonium is available. The model also predicted that when high concentrations of acetate are added during in situ bioremediation, Geobacter species would predominate, consistent with field-scale observations. This can be attributed to the higher expected growth yields of Rhodoferax and the ability of Geobacter to fix nitrogen. The modeling predicted relative proportions of Geobacter and Rhodoferax in geochemically distinct zones of the Rifle site that were comparable to those that were previously documented with molecular techniques. The model also predicted that under nitrogen fixation, higher carbon and electron fluxes would be diverted toward respiration rather than biomass formation in Geobacter, providing a potential explanation for enhanced in situ U(VI) reduction in low-ammonium zones. These results show that genome-scale modeling can be a useful tool for predicting microbial interactions in subsurface environments and shows promise for designing bioremediation strategies.

  19. Feasibility of hydraulic separation in a novel anaerobic-anoxic upflow reactor for biological nutrient removal.

    Science.gov (United States)

    Díez-Montero, Rubén; De Florio, Loredana; González-Viar, Marta; Volcke, Eveline I P; Tejero, Iñaki

    2015-01-01

    This contribution deals with a novel anaerobic-anoxic reactor for biological nutrient removal (BNR) from wastewater, termed AnoxAn. In the AnoxAn reactor, the anaerobic and anoxic zones for phosphate removal and denitrification are integrated in a single continuous upflow sludge blanket reactor, aiming at high compactness and efficiency. Its application is envisaged in those cases where retrofitting of existing wastewater treatment plants for BNR, or the construction of new ones, is limited by the available surface area. The environmental conditions are vertically divided up inside the reactor with the anaerobic zone at the bottom and the anoxic zone above. The capability of the AnoxAn configuration to establish two hydraulically separated zones inside the single reactor was assessed by means of hydraulic characterization experiments and model simulations. Residence time distribution (RTD) experiments in clean water were performed in a bench-scale (48.4 L) AnoxAn prototype. The required hydraulic separation between the anaerobic and anoxic zones, as well as adequate mixing in the individual zones, were obtained through selected mixing devices. The observed behaviour was described by a hydraulic model consisting of continuous stirred tank reactors and plug-flow reactors. The impact of the denitrification process in the anoxic zone on the hydraulic separation was subsequently evaluated through model simulations. The desired hydraulic behaviour proved feasible, involving little mixing between the anaerobic and anoxic zones (mixing flowrate 40.2 % of influent flowrate) and negligible nitrate concentration in the anaerobic zone (less than 0.1 mgN L(-1)) when denitrification was considered.

  20. Evidence For Volcanic Initiation Of Cretaceous Ocean Anoxic Events (Invited)

    Science.gov (United States)

    Sageman, B. B.; Hurtgen, M. T.; McElwain, J.; Adams, D.; Barclay, R. S.; Joo, Y.

    2010-12-01

    Increasing evidence from studies of Cretaceous ocean anoxic events (OAE’s) has suggested that major changes in volcanic activity may have played a significant role in their genesis. Numerous specific mechanisms of have been proposed, including increases in atmospheric CO2 and surface temperature, leading to enhanced chemical weathering and terrestrial nutrient release, or increases in reduced trace metal fluxes, leading to oxygen depletion and possibly providing micronutrients for enhanced primary production. An additional pathway by which the byproducts of enhanced volcanic activity may have contributed to OAE genesis involves relationships between the biogeochemical cycles sulfur, iron, and phosphorus. Recent analysis of S-isotope data from carbonate-associated sulfate and pyrite collected across the Cenomanian-Turonian OAE2 in the Western Interior basin suggest that increases in sulfate to an initially sulfate-depleted ocean preceded onset of the event. Modern lake data support the idea that increases in sulfate concentration drive microbial sulfate reduction, leading to more efficient regeneration of P from sedimentary organic matter. If the early Cretaceous opening of the South Atlantic was accompanied by evaporite deposition sufficient to draw down global marine sulfate levels, and widespread anoxia leading to elevated pyrite burial helped maintain these low levels for the succeeding 30 myr, during which most Cretaceous OAE’s are found, perhaps pulses of volcanism that rapidly introduced large volumes of sulfate may have played a key role in OAE initiation. The eventually burial of S in the form of pyrite may have returned sulfate levels to a low background, thus providing a mechanism to terminate the anoxic events. This talk will review the evidence for volcanic initiation of OAE’s in the context of the sulfate-phosphorus regeneration model.

  1. Status and understanding of groundwater quality in the South Coast Range-Coastal study unit, 2008: California GAMA Priority Basin Project

    Science.gov (United States)

    Burton, Carmen A.; Land, Michael; Belitz, Kenneth

    2013-01-01

    , total dissolved solids (TDS), and sulfate were the inorganic constituents with SMCLs detected at high relative-concentrations. In contrast to inorganic constituents, organic constituents with human-health benchmarks were not detected at high relative-concentrations in the primary aquifer system in the SCRC study unit. Of the 205 organic constituents analyzed, 21 were detected—13 with human-health benchmarks. Perchloroethene (PCE) was the only VOC detected at moderate relative-concentrations. PCE, dichlorodifluoromethane (CFC-12), and chloroform were detected in more than 10 percent of the primary aquifer system. Of the two special-interest constituents, one was detected; perchlorate, which has a human-health benchmark, was detected at moderate relative-concentrations in 29 percent of the primary aquifer system and had a detection frequency of 60 percent in the SCRC study unit. The second component of this study, the understanding assessment, identified the natural and human factors that may have affected groundwater quality in the SCRC study unit by evaluating statistical correlations between water-quality constituents and potential explanatory factors. The potential explanatory factors evaluated were land use, septic tank density, well depth and depth to top-of-perforations, groundwater age, density and distance to the nearest formerly leaking underground fuel tank (LUFT), pH, and dissolved oxygen (DO) concentration. Results of the statistical evaluations were used to explain the occurrence and distribution of constituents in the study unit. DO was the primary explanatory factor influencing the concentrations of many inorganic constituents. Arsenic, iron, and manganese concentrations increased as DO concentrations decreased, consistent with patterns expected as a result of reductive dissolution of iron and (or) manganese oxides in aquifer sediments. Molybdenum concentrations increased in anoxic conditions and in oxic conditions with high pH, reflecting two mechanisms

  2. Sediment-water 02 dynamics and feedbacks to sediment oxic, suboxic, and anoxic processes on the Louisiana shelf

    Science.gov (United States)

    The Mississippi and Atchafalaya Rivers annually discharge 674 km3 of freshwater, 86 x 109 moles nitrogen, 5 x 109 moles phosphorus, and 325 x 109 moles organic carbon to the Louisiana shelf. The seasonal input and transport of these materials causes large temporal and spatial va...

  3. Live (Rose-bengal stained) foraminifera from deep-sea anoxic salt brine in the Eastern Mediterranean: toward understanding limit of life for single-celled eukaryotes (foraminifera)

    Science.gov (United States)

    Kitazato, H.; Ohkawara, N.; Iwasaki, A.; Nomaki, H.; Akoumianaki, I.; Tokuyama, H.

    2012-04-01

    What is a limit of life for the eukaryotes? Eukaryotes are thought to adapt and evolve under oxic environmental conditions. Recently, there are many exceptions for this hypothesis, as many eukaryotes including metazoan groups are found in anoxic environmental conditions. We found many rose-bengal stained foraminifera from a deep-hypersaline anoxic basin (DHAB) in the eastern Mediterranean. During KH06-04 cruise, we conducted oceanographic research at Medée Lake, the largest DHAB, that is located 100km southwest of Crete Island in the eastern Mediterranean. The lake situates at 2920m in water depth. Depth of saline water is 120m in maximum. Both water and sediment samplings were carried out both with Niskin bottles and multiple corer attached to camera watching sampling system at three sites, inside of the lake (CS), the edge of the lake (OMS) and the normal deep-sea floor (RS). Temperature, salinity, and dissolved oxygen concentrations at central saline lake are 15.27 oC, 328PSU, and 0.0 ml/L, respectively. Strong smell of hydrogen sulfide was detected from the lake sediment. Subsamples were conducted for multiple core samples using 3 subcores(φ 2.9cm) from each core tube (φ 8.2cm). Sediment samples were fixed with 4% formalin Rose Bengal solution on board. In laboratory, samples were washed with 32μm sieve. Rose Bengal stained specimens were picked under binocular stereomicroscope (Zeiss Stemi SV11) for surface 0.5cm layer, and identified with inverted microscope (Nikon ECLIPSE TE300). In total, 26 species belonging to 9 genera were identified from three sites. Six species belonging to two genera were identified in the center of the salt brine. Only a few species are common among three sites, even though the numbers of common species were 10 between OMS and RS sites. In DHAB, spherical organic-walled species, such as allogromiid and psammosphaerid, are dominant. In contrast, tube-like chitinous foraminifera, such as Resigella, Conicotheca and Nodellum, are

  4. Heterotrophic potential of Atribacteria from deep marine Antarctic sediment

    Science.gov (United States)

    Carr, S. A.; Orcutt, B.; Mandernack, K. W.; Spear, J. R.

    2015-12-01

    Bacteria belonging to the newly classified candidate phylum "Atribacteria" (formerly referred to as "OP9" and "JS1") are common in anoxic methane-rich sediments. However, the metabolic functions and biogeochemical role of these microorganisms in the subsurface remains unrealized due to the lack of pure culture representatives. This study observed a steady increase of Atribacteria-related sequences with increasing sediment depth throughout the methane-rich zone of the Adélie Basin, Antarctica (according to a 16S rRNA gene survey). To explore the functional potential of Atribacteria in this basin, samples from various depths (14, 25 and 97 meters below seafloor), were subjected to metagenomic sequencing. Additionally, individual cells were separated from frozen, unpreserved sediment for whole genome amplification. The successful isolation and sequencing of a single-amplified Atribacteria genome from these unpreserved sediments demonstrates a future use of single cell techniques with previously collected and frozen sediments. Our resulting single-cell amplified genome, combined with metagenomic interpretations, provides our first insights to the functional potential of Atribacteria in deep subsurface settings. As observed for non-marine Atribacteria, genomic analyses suggest a heterotrophic metabolism, with Atribacteria potentially producing fermentation products such as acetate, ethanol and CO2. These products may in turn support methanogens within the sediment microbial community and explain the frequent occurrence of Atribacteria in anoxic methane-rich sediments.

  5. Sedimentation rate in the Baltic Sea

    Energy Technology Data Exchange (ETDEWEB)

    Ilus, E.; Mattila, J.; Klemola, S.; Ikaeheimonen, T.K. [STUK Radiation and Nuclear Safety Authority (Finland); Niemisto, L. [Finnish Inst. of Marine Research (Finland)

    2001-04-01

    Varying redox conditions may affect the occurrence and concentrations of certain radionuclides in the surface layers of sediments and in near-bottom waters by causing remobilization of radionuclides from surface sediments to the overlying water and their settling back into the sediment. In recent decades about 70.000 km{sup 2} of the sea bottom in the deepest part of the Baltic Sea (about 19% of its total area) have withstood almost continuous anoxic conditions; thus, it is important to know to what extent depletion of oxygen can affect the behaviour of these radionuclides in near-bottom waters. The aim of the project was to resolve the above question in a coastal basin periodically undergoing anoxic conditions. Radioecological processes in sediments and in near-bottom water under varying redoxconditions were studied in the deep area of the Haestholmsfjaerden Bay in Loviisa (eastern Gulf of Finland) in 1995-1996. The Haestholmsfjaerden Bay is a semienclosed basin between the mainland and the archipelago and is connected with the open Gulf of Finland only through narrow, shallow sounds: In 1995, total depletion of oxygen occurred in the hypolimnion of Haestholmsfjaerden Bay during 2 periods in late summer and autumn. In 1996, oxygen conditions were the worst ever observed in the Haestholmsfjaerden deep. During early autumn anoxic conditions prevailed for more than 1 month in the near-bottom water. The highest total phosphorus and total nitrogen concentrations in the near-bottom water during these periods were 20- and 4- fold compared with the corresponding values in surface water. According to the results obtained in this project, remobilization of {sup 137}Cs and {sup 239,240}Pu from sediments to near-bottom water is negligible or non-existent in the Haestholmsfjaerden deep. If it does occur, however, it may be so slight that it is not possible to observe with the methods used in this study. Although the anoxic periods are quite short in the Haestholmsfjaerden deep

  6. Phosphorus recycling in sediments of the Central Baltic Sea

    Directory of Open Access Journals (Sweden)

    L. Viktorsson

    2012-11-01

    Full Text Available Benthic fluxes of dissolved inorganic phosphorus (DIP were measured in situ in the Eastern Gotland Basin (EGB, Central Baltic Sea, using benthic landers. A total of 40 flux measurements on 13 stations at water depths ranging from 30–210 m and under different oxygen regimes were carried out on three cruises during three consecutive years (2008–2010 in August–September. Our study is the first to report in situ DIP fluxes in the Baltic Proper, and it provides the most comprehensive data set of benthic DIP fluxes in the Baltic Proper existing to date. DIP fluxes increased with increasing water depth and with decreasing bottom water oxygen concentration. Average fluxes were calculated for oxic bottom water conditions (−0.003 ± 0.040 mmol m−2 d−1, hypoxic conditions (0.027 ± 0.067 mmol m−2 d−1 and anoxic conditions (0.376 ± 0.214 mmol m−2 d−1. The mean flux on anoxic bottoms was ca. 5–10 times higher than previous estimates based on ex situ measurements, but agreed well with previous flux estimations from changes in the basin water DIP pool. The DIP flux was positively correlated with the organic carbon inventory of sediment and the benthic flux of dissolved inorganic carbon (DIC on anoxic stations, but these variables were uncorrelated on oxic stations. The positive correlation between DIP and DIC fluxes suggests that the benthic DIP flux on anoxic bottoms in the Baltic Proper is mainly controlled by rates of deposition and degradation of organic matter. The flux from anoxic sediment was very P rich in relation to both C and N, and the average C:P ratio in fluxes on anoxic accumulation bottoms was 69 ± 15, which is well below the Redfield C:P ratio of 106:1. On oxic stations, however, the C:P flux ratio was much higher than the Redfield ratio, consistent with well-known P retention mechanisms associated with iron and bacteria in oxidized sediment. Using a

  7. Arsenic in groundwater of the Red River Floodplain, Vietnam

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Larsen, Flemming; Jessen, Søren

    2007-01-01

    The mobilization of arsenic (As) to the groundwater was studied in a shallow Holocene aquifer on the Red River flood plain near Hanoi, Vietnam. Results show an anoxic aquifer featuring organic carbon decomposition with redox zonation dominated by the reduction of Fe-oxides and methanogenesis....... The concentration of As increases over depth to a concentration of up to 550 μg/L. Most As is present as As(III) but some As(V) is always found. Arsenic correlates well with NH4, relating its release to organic matter decomposition and the source of As appears to be the Fe-oxides being reduced....

  8. Microbial community in high arsenic shallow groundwater aquifers in Hetao Basin of Inner Mongolia, China.

    Directory of Open Access Journals (Sweden)

    Ping Li

    Full Text Available A survey was carried out on the microbial community of 20 groundwater samples (4 low and 16 high arsenic groundwater and 19 sediments from three boreholes (two high arsenic and one low arsenic boreholes in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia, using the 454 pyrosequencing approach. A total of 233,704 sequence reads were obtained and classified into 12-267 operational taxonomic units (OTUs. Groundwater and sediment samples were divided into low and high arsenic groups based on measured geochemical parameters and microbial communities, by hierarchical clustering and principal coordinates analysis. Richness and diversity of the microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four genera in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter dominated high arsenic sediments. Archaeal sequences in high arsenic groundwater were mostly related to methanogens. Biota-environment matching and co-inertia analyses showed that arsenic, total organic carbon, SO4(2-, SO4(2-/total sulfur ratio, and Fe(2+ were important environmental factors shaping the observed microbial communities. The results of this study expand our current understanding of microbial ecology in high arsenic groundwater aquifers and emphasize the potential importance of microbes in arsenic transformation in the Hetao Basin, Inner Mongolia.

  9. Microbial community in high arsenic shallow groundwater aquifers in Hetao Basin of Inner Mongolia, China.

    Science.gov (United States)

    Li, Ping; Wang, Yanhong; Dai, Xinyue; Zhang, Rui; Jiang, Zhou; Jiang, Dawei; Wang, Shang; Jiang, Hongchen; Wang, Yanxin; Dong, Hailiang

    2015-01-01

    A survey was carried out on the microbial community of 20 groundwater samples (4 low and 16 high arsenic groundwater) and 19 sediments from three boreholes (two high arsenic and one low arsenic boreholes) in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia, using the 454 pyrosequencing approach. A total of 233,704 sequence reads were obtained and classified into 12-267 operational taxonomic units (OTUs). Groundwater and sediment samples were divided into low and high arsenic groups based on measured geochemical parameters and microbial communities, by hierarchical clustering and principal coordinates analysis. Richness and diversity of the microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four genera in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter dominated high arsenic sediments. Archaeal sequences in high arsenic groundwater were mostly related to methanogens. Biota-environment matching and co-inertia analyses showed that arsenic, total organic carbon, SO4(2-), SO4(2-)/total sulfur ratio, and Fe(2+) were important environmental factors shaping the observed microbial communities. The results of this study expand our current understanding of microbial ecology in high arsenic groundwater aquifers and emphasize the potential importance of microbes in arsenic transformation in the Hetao Basin, Inner Mongolia.

  10. The use of magnesium peroxide for the inhibition of sulfate-reducing bacteria under anoxic conditions.

    Science.gov (United States)

    Chang, Yu-Jie; Chang, Yi-Tang; Hung, Chun-Hsiung

    2008-11-01

    Sulfate-reducing bacteria (SRB), which cause microbiologically influenced material corrosion under anoxic conditions, form one of the major groups of microorganisms responsible for the generation of hydrogen sulfide. In this study, which is aimed at reducing the presence of SRB, a novel alternative approach involving the addition of magnesium peroxide (MgO2) compounds involving the use of reagent-grade MgO2 and a commercial product (ORC) was evaluated as a means of inhibiting SRB in laboratory batch columns. Different concentrations of MgO2 were added in the columns when black sulfide sediment had appeared in the columns. The experimental results showed that MgO2 is able to inhibit biogenic sulfide. The number of SRB, the sulfide concentration and the sulfate reducing rate (SRR) were decreased. ORCtrade mark as an additive was able to decrease more effectively the concentration of sulfide in water and the SRB-control effect was maintained over a longer time period when ORCtrade mark was used. The level of oxidation-reduction potential (ORP), which has a linear relationship to the sulfide/sulfate ratio, is a good indicator of SRB activity. As determined by fluorescence in-situ hybridization (FISH), most SRB growth was inhibited under increasing amounts of added MgO2. The concentration of sulfide reflected the abundance of the SRB. Utilization of organic matter greater than the theoretical SRB utilization rate indicated that facultative heterotrophs became dominant after MgO2 was added. The results of this study could supply the useful information for further study on evaluating the solution to biocorrosion problems in practical situations.

  11. Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities.

    Directory of Open Access Journals (Sweden)

    Simon P Rout

    Full Text Available One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW is disposal to a cementitious geological disposal facility (GDF. Under the alkaline (10.013.0 anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP are dominated by α- and β-isosaccharinic acids (ISA, which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

  12. Long-term groundwater contamination after source removal—The role of sorbed carbon and nitrogen on the rate of reoxygenation of a treated-wastewater plume on Cape Cod, MA, USA

    Science.gov (United States)

    Smith, Richard L.; Repert, Deborah A.; Barber, Larry B.; LeBlanc, Denis R.

    2013-01-01

    The consequences of groundwater contamination can remain long after a contaminant source has been removed. Documentation of natural aquifer recoveries and empirical tools to predict recovery time frames and associated geochemical changes are generally lacking. This study characterized the long-term natural attenuation of a groundwater contaminant plume in a sand and gravel aquifer on Cape Cod, Massachusetts, after the removal of the treated-wastewater source. Although concentrations of dissolved organic carbon (DOC) and other soluble constituents have decreased substantially in the 15 years since the source was removed, the core of the plume remains anoxic and has sharp redox gradients and elevated concentrations of nitrate and ammonium. Aquifer sediment was collected from near the former disposal site at several points in time and space along a 0.5-km-long transect extending downgradient from the disposal site and analyses of the sediment was correlated with changes in plume composition. Total sediment carbon content was generally low (< 8 to 55.8 μmol (g dry wt)− 1) but was positively correlated with oxygen consumption rates in laboratory incubations, which ranged from 11.6 to 44.7 nmol (g dry wt)− 1 day− 1. Total water extractable organic carbon was < 10–50% of the total carbon content but was the most biodegradable portion of the carbon pool. Carbon/nitrogen (C/N) ratios in the extracts increased more than 10-fold with time, suggesting that organic carbon degradation and oxygen consumption could become N-limited as the sorbed C and dissolved inorganic nitrogen (DIN) pools produced by the degradation separate with time by differential transport. A 1-D model using total degradable organic carbon values was constructed to simulate oxygen consumption and transport and calibrated by using observed temporal changes in oxygen concentrations at selected wells. The simulated travel velocity of the oxygen gradient was 5–13% of the groundwater velocity. This

  13. High bacterial biodiversity increases degradation performance of hydrocarbons during bioremediation of contaminated harbor marine sediments.

    Science.gov (United States)

    Dell'Anno, Antonio; Beolchini, Francesca; Rocchetti, Laura; Luna, Gian Marco; Danovaro, Roberto

    2012-08-01

    We investigated changes of bacterial abundance and biodiversity during bioremediation experiments carried out on oxic and anoxic marine harbor sediments contaminated with hydrocarbons. Oxic sediments, supplied with inorganic nutrients, were incubated in aerobic conditions at 20 °C and 35 °C for 30 days, whereas anoxic sediments, amended with organic substrates, were incubated in anaerobic conditions at the same temperatures for 60 days. Results reported here indicate that temperature exerted the main effect on bacterial abundance, diversity and assemblage composition. At higher temperature bacterial diversity and evenness increased significantly in aerobic conditions, whilst decreased in anaerobic conditions. In both aerobic and anaerobic conditions, biodegradation efficiencies of hydrocarbons were significantly and positively related with bacterial richness and evenness. Overall results presented here suggest that bioremediation strategies, which can sustain high levels of bacterial diversity rather than the selection of specific taxa, may significantly increase the efficiency of hydrocarbon degradation in contaminated marine sediments.

  14. Cretaceous black shale and the oceanic red beds:Process and mechanisms of oceanic anoxic events and oxic environment

    Institute of Scientific and Technical Information of China (English)

    Zhenguo ZHANG; Nianqiao FANG; Lianfeng GAO; Baoling GUI; Muhua CUI

    2008-01-01

    The Cretaceous is an important period in which many geological events occurred,especially the OAEs (oceanic anoxic events) which are characterized by black shale,and the oxic process characterized by CORBs (Cretaceous oceanic red beds).In this paper,the causative mechanism behind the formation of black shale and the oceanic red beds are described in detail.This may explain how the oceanic environment changed from anoxic to oxic in the Cretaceous period.It is suggested that these two different events happened because of the same cause.On the one hand,the large-scale magma activities in Cretaceous caused the concentration of CO2,the release of the inner energy of the earth,superficial change in the ocean-land,and finally,the increase of atmospheric temperature.These changes implied the same tendency as the oceanic water temperature show,and caused the decrease in O2 concentration in the Cretaceous ocean,and finally resulted in the occurrence of the OAEs.On the other hand,violent and frequent volcanic eruptions in the Cretaceous produced plenty of Fe-enriched lava on the seafloor.When the seawater reacted with the lava,the element Fe became dissolved in seawater.Iron,which could help phytoplankton grow rapidly,is a micronutrient essential to the synthesis of enzymes required for photosynthesis in the oceanic environment.Phytoplankton,which grows in much of the oceans around the world,can consume carbon dioxide in the air and the ocean.Meanwhile,an equal quantity of oxygen can be produced by the phytoplankton during its growth.Finally,the oxic environment characterized by red sediment rich in Fe3+appeared.The anoxic and oxic conditions in the Cretaceous ocean were caused by volcanic activities,but they stemmed from different causative mechanisms.The former was based on physical and chemical processes,while the latter involved more complicated bio-oceanic-geochemical processes.

  15. Applicability of anoxic-oxic process in treating petrochemical wastewater

    Institute of Scientific and Technical Information of China (English)

    Li-jun ZHAO; Fang MA; Jing-bo GUO

    2009-01-01

    To explore the applicability of anoxic-oxic (A/O) activated sludge process for petrochemical wastewater treatment, the relationship between bacterial community structure and pollutants loading/removal efficiencies was investigated by gas chromatograph-mass spectrometry (GC-MS), polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and other conventional techniques. It showed that when the concentrations of the influent chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) were 420~560 mg/L and 64~100 mg/L, respectively, the corresponding average effluent concentra-tions were 160 mg/L and 55 mg/L, which were 1.6 and 2.2 times higher than those of the national standards in China, respectively, demonstrating the inefficient performances of A/O process. Analysis of GC-MS indicated that refractory pollutants were mainly removed by sludge adsorption, but not by biodegradation. PCR-DGGE profile analysis suggested that the biological system was species-rich, but there was apparent succession of the bacterial community structure in different locations of the A/O system. Variations of bacterial community structure and pollutant Ioadings had obvious influences on pollutants removal efficiencies. Thus, A/O process was inapplicable for the treatment of complicated petrochemical wastewater, and strategies such as the reinforcement of pre-treatment and two-stage A/O process were suggested.

  16. Long-term subculture of human keratinocytes under an anoxic condition.

    Science.gov (United States)

    Kino-oka, Masahiro; Agatahama, Yuka; Haga, Yuki; Inoie, Masukazu; Taya, Masahito

    2005-07-01

    The serial subculturing of human keratinocyte cells under the anoxic and normoxic conditions was examined. The cumulative number of population doublings in the subcultures under the former condition increased 2.1-fold while maintaining an appreciable growth rate of cells, as compared with that under the latter condition. Moreover, the migration ability, which was estimated by the rotation rate of paired cells, was maintained accompanied by fully developed filopodia of F-actin filaments under the anoxic condition, despite of the poor development of stress fibers at the center of the cellular body. The cells passaged under the anoxic condition possessed the sufficient clonogenic potential to form epithelial sheets, supporting the view that the long-term subculture of keratinocytes under the anoxic condition can be applied for cell expansion in the practical production of epithelial sheets.

  17. Factors affecting biological denitrifying dephosphatation in anaerobic/anoxic/aerobic sequencing batch reactor

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This study was conducted to verify and discuss the denitrifying dephosphatation under different levels of nitrate concentration and retention time of anoxic/aerobic process in a Sequencing Batch Reactor ( SBR ).The results of tests demonstrated that there were two kinds of phosphorus-accumulating organisms (PAOs) in the biological excess phosphorus removal (BEPR) system. One was non-DNPAOs that could only use oxygen as terminal electron acceptors, the other was denitrifying PAOs (DNPAOs) that could use both nitrate and oxygen as terminal electron acceptors. Phosphorus uptake efficiency could be attained under anoxic period ranging from 28.7%-96.7% in an anacrobic/anoxic/aerobic system. Experimental results showed that nitrate concentration and retention time of anoxic/aerobic process were the key factors affecting the course of denitrifying dephosphatation.

  18. Anoxic biodegradation of petroleum hydrocarbons in saline media using denitrifier biogranules.

    Science.gov (United States)

    Moussavi, Gholamreza; Shekoohiyan, Sakine; Naddafi, Kazem

    2016-07-01

    The total petroleum hydrocarbons (TPH) biodegradation was examined using biogranules at different initial TPH concentration and contact time under anoxic condition in saline media. The circular compact biogranules having the average diameter between 2 and 3mm were composed of a dense population of Bacillus spp. capable of biodegrading TPH under anoxic condition in saline media were formed in first step of the study. The biogranules could biodegrade over 99% of the TPH at initial concentration up to 2g/L at the contact time of 22h under anoxic condition in saline media. The maximum TPH biodegradation rate of 2.6 gTPH/gbiomass.d could be obtained at initial TPH concentration of 10g/L. Accordingly, the anoxic biogranulation is a possible and promising technique for high-rate biodegradation of petroleum hydrocarbons in saline media.

  19. Electric currents couple spatially separated biogeochemical processes in marine sediment

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Risgaard-Petersen, Nils; Fossing, Henrik;

    2010-01-01

    be coupled by electric currents in nature. Here we provide evidence that electric currents running through defaunated sediment couple oxygen consumption at the sediment surface to oxidation of hydrogen sulphide and organic carbon deep within the sediment. Altering the oxygen concentration in the sea water...... in the sediment was driven by electrons conducted from the anoxic zone. A distinct pH peak in the oxic zone could be explained by electrochemical oxygen reduction, but not by any conventional sets of aerobic sediment processes. We suggest that the electric current was conducted by bacterial nanowires combined...... with pyrite, soluble electron shuttles and outer-membrane cytochromes. Electrical communication between distant chemical and biological processes in nature adds a new dimension to our understanding of biogeochemistry and microbial ecology....

  20. Remediation of TCE-contaminated groundwater using nanocatalyst and bacteria.

    Science.gov (United States)

    Kang, Ser Ku; Seo, Hyunhee; Sun, Eunyoung; Kim, Inseon; Roh, Yul

    2011-08-01

    The objective of this study was to develop and evaluate the remediation of trichloroethene (TCE)-contaminated groundwater using both a nanocatalyst (bio-Zn-magnetite) and bacterium (similar to Clostridium quinii) in anoxic environments. Of the 7 nanocatalysts tested, bio-Zn-magnetite showed the highest TCE dechlorination efficiency, with an average of ca. 90% within 8 days in a batch experiment. The column tests confirmed that the application of bio-Zn-magnetite in combination with the bacterium achieved high degradation efficiency (ca. 90%) of TCE within 5 days compared to the nanocatalyst only, which degraded only 30% of the TCE. These results suggest that the application of a nanocatalyst and the bacterium have potential for the remediation of TCE-contaminated groundwater in subsurface environments.

  1. Response of the Cr isotope proxy to Cretaceous Ocean Anoxic Event 2 in a pelagic carbonate succession from the Western Interior Seaway

    Science.gov (United States)

    Holmden, C.; Jacobson, A. D.; Sageman, B. B.; Hurtgen, M. T.

    2016-08-01

    Chromium offers a redox sensitive isotopic proxy with potential for tracing past oxygen levels in the oceans. We explore this potential in a pelagic succession of marine carbonate sediment deposited during Cretaceous Ocean Anoxic Event 2 (OAE 2) in the Western Interior Seaway, Colorado (WIS), using the USGS Portland #1 Core. Reduction of Cr(VI) causes light isotopes of Cr to preferentially partition into Cr(III). Because Cr(VI) is the thermodynamically favoured species in oxygenated seawater, and Cr(III) is relatively insoluble under the same conditions, increased removal of Cr(III) into anoxic marine sediment during ocean anoxic events should cause positive shifts in seawater δ53Cr values. This assumes that isotopic fractionation associated with all Cr removal fluxes from the oceans was constant during OAE 2 and that there was no change in Cr input fluxes to the oceans. Here, we report findings that counter this prediction, namely evidence for a negative shift in seawater δ53Cr during OAE 2 of ∼1.1‰ in the WIS. The magnitude of the excursion depends on the speciation of Cr removed in this setting over the duration of OAE 2, as well as the fractionation factor accompanying the removal flux of chromate into carbonate sediment, both of which are uncertain. The δ53Cr excursion reaches values as low -0.09‰ during OAE 2, which is indistinguishable from the high-temperature igneous rock baseline value of -0.124 ± 0.101‰ (2σ). Moreover, the minima in the δ53Cr profile coincides with a peak in Cr concentrations in the study core, as well as anomalous enrichments of other trace metals of basaltic affinity. Building on previous studies linking OAE 2 to a massive episode of submarine volcanic activity, we attribute the decrease in carbonate δ53Cr values during OAE 2 to the expansion of a hydrothermal superplume created during eruptions of the Caribbean Large Igneous Province (LIP). This metal laden plume, enriched in Cr(III) and probably anoxic, moved from deep

  2. Microscale geochemical gradients in Hanford 300 Area sediment biofilms and influence of uranium.

    Science.gov (United States)

    Nguyen, Hung Duc; Cao, Bin; Mishra, Bhoopesh; Boyanov, Maxim I; Kemner, Kenneth M; Fredrickson, Jim K; Beyenal, Haluk

    2012-01-01

    The presence and importance of microenvironments in the subsurface at contaminated sites were suggested by previous geochemical studies. However, no direct quantitative characterization of the geochemical microenvironments had been reported. We quantitatively characterized microscale geochemical gradients (dissolved oxygen (DO), H(2), pH, and redox potential) in Hanford 300A subsurface sediment biofilms. Our results revealed significant differences in geochemical parameters across the sediment biofilm/water interface in the presence and absence of U(VI) under oxic and anoxic conditions. While the pH was relatively constant within the sediment biofilm, the redox potential and the DO and H(2) concentrations were heterogeneous at the microscale (<500-1000 μm). We found microenvironments with high DO levels (DO hotspots) when the sediment biofilm was exposed to U(VI). On the other hand, we found hotspots (high concentrations) of H(2) under anoxic conditions both in the presence and in the absence of U(VI). The presence of anoxic microenvironments inside the sediment biofilms suggests that U(VI) reduction proceeds under bulk oxic conditions. To test this, we operated our biofilm reactor under air-saturated conditions in the presence of U(VI) and characterized U speciation in the sediment biofilm. U L(III)-edge X-ray absorption spectroscopy (XANES and EXAFS) showed that 80-85% of the U was in the U(IV) valence state.

  3. Biogeochemistry of dissolved organic matter in an anoxic intertidal creek bank

    Science.gov (United States)

    Seidel, Michael; Beck, Melanie; Riedel, Thomas; Waska, Hannelore; Suryaputra, I. G. N. A.; Schnetger, Bernhard; Niggemann, Jutta; Simon, Meinhard; Dittmar, Thorsten

    2014-09-01

    Seawater circulation in permeable coastal sediments is driven by tidal changes in hydraulic gradients. The resulting submarine groundwater discharge is a source of nutrients and dissolved organic matter (DOM) to the water column. Yet, little is known about the cycling of DOM within tidal sediments, because the molecular DOM characterization remains analytically challenging. One technique that can dissect the multitude of molecules in DOM is ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). To aim at a high resolution DOM analysis we study the seasonal turnover and marine and terrestrial sources of DOM in an intertidal creek bank of the southern North Sea down to 3 m depth and link the biogeochemical processes to FT-ICR-MS data and the analyses of inorganic porewater chemistry, δ13C of solid-phase extracted dissolved organic carbon (SPE-DOC), dissolved black carbon (DBC) and dissolved carbohydrates (DCHO). Increasing concentrations of dissolved Fe, Mn, P, total alkalinity, dissolved nitrogen, DOC and a concomitant decrease of sulfate along the seawater circulation path from the upper tidal flat to the tidal flat margin indicate continuous microbial activity. The relative increase of Si concentrations, unsaturated aliphatics, peptide molecular formulae and isotopically more 13C-enriched SPE-DOC towards the tidal flat margin suggests that remineralization processes mobilize DOM from buried algal (diatoms) and microbial biomass. Porewater in sediments ocean. Porewater DOM accumulating at the low water line is enriched in N and S. We hypothesize that this is partly due to DOM reacting with dissolved sulfide and ammonium which may increase the refractory character of the DOM, hence making it less bioavailable for in situ active microbes.

  4. Sulfur-based mixotrophic denitrification corresponding to different electron donors and microbial profiling in anoxic fluidized-bed membrane bioreactors.

    Science.gov (United States)

    Zhang, Lili; Zhang, Chao; Hu, Chengzhi; Liu, Huijuan; Bai, Yaohui; Qu, Jiuhui

    2015-11-15

    Sulfur-based mixotrophic denitrifying anoxic fluidized bed membrane bioreactors (AnFB-MBR) were developed for the treatment of nitrate-contaminated groundwater with minimized sulfate production. The nitrate removal rates obtained in the methanol- and ethanol-fed mixotrophic denitrifying AnFB-MBRs reached 1.44-3.84 g NO3 -N/L reactor d at a hydraulic retention time of 0.5 h, which were significantly superior to those reported in packed bed reactors. Compared to methanol, ethanol was found to be a more effective external carbon source for sulfur-based mixotrophic denitrification due to lower sulfate and total organic carbon concentrations in the effluent. Using pyrosequencing, the phylotypes of primary microbial groups in the reactor, including sulfur-oxidizing autotrophic denitrifiers, methanol- or ethanol-supported heterotrophic denitrifiers, were investigated in response to changes in electron donors. Principal component and heatmap analyses indicated that selection of electron donating substrates largely determined the microbial community structure. The abundance of Thiobacillus decreased from 45.1% in the sulfur-oxidizing autotrophic denitrifying reactor to 12.0% and 14.2% in sulfur-based methanol- and ethanol-fed mixotrophic denitrifying bioreactors, respectively. Heterotrophic Methyloversatilis and Thauera bacteria became more dominant in the mixotrophic denitrifying bioreactors, which were possibly responsible for the observed methanol- and ethanol-associated denitrification.

  5. Origin of first cells at terrestrial, anoxic geothermal fields.

    Science.gov (United States)

    Mulkidjanian, Armen Y; Bychkov, Andrew Yu; Dibrova, Daria V; Galperin, Michael Y; Koonin, Eugene V

    2012-04-01

    All cells contain much more potassium, phosphate, and transition metals than modern (or reconstructed primeval) oceans, lakes, or rivers. Cells maintain ion gradients by using sophisticated, energy-dependent membrane enzymes (membrane pumps) that are embedded in elaborate ion-tight membranes. The first cells could possess neither ion-tight membranes nor membrane pumps, so the concentrations of small inorganic molecules and ions within protocells and in their environment would equilibrate. Hence, the ion composition of modern cells might reflect the inorganic ion composition of the habitats of protocells. We attempted to reconstruct the "hatcheries" of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells. These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K(+), Zn(2+), Mn(2+), and phosphate. Thus, protocells must have evolved in habitats with a high K(+)/Na(+) ratio and relatively high concentrations of Zn, Mn, and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under the anoxic, CO(2)-dominated primordial atmosphere, the chemistry of basins at geothermal fields would resemble the internal milieu of modern cells. The precellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapor that were lined with porous silicate minerals mixed with metal sulfides and enriched in K(+), Zn(2+), and phosphorous compounds.

  6. Ecohydrological Investigations of a Groundwater-Lake System

    DEFF Research Database (Denmark)

    Frandsen, Mette Cristine Schou

    I). •Does dense bottom vegetation affect the small scale hydrology of the lake bed sediment? (Paper 2). •How can natural tracers (δ 18O) be used to quantify the temporal variation in groundwater seepage dynamics? (Paper 3). •Is it possible to combine ecological data of surface water chemistry...... and data on groundwater chemistry to stoichiometrically describe changes in the lake in a historical time frame? (Paper 4). he main conclusions from the study are: •When evaluating the ecology of a groundwater-lake system, both hydrological and biological parameters are needed to accurately describe...... by this. The reasons for the lowered hydraulic conductivity seems to be an combination of the organic content in the sediment (i.e. the roots of the plants) and a vegetation induced entrapment of fine particles in the sediment. Over the course of three years I followed the small scale variation...

  7. CO2-induced shift in microbial activity affects carbon trapping and water quality in anoxic bioreactors

    Science.gov (United States)

    Kirk, Matthew F.; Santillan, Eugenio F. U.; Sanford, Robert A.; Altman, Susan J.

    2013-12-01

    Microbial activity is a potentially important yet poorly understood control on the fate and environmental impact of CO2 that leaks into aquifers from deep storage reservoirs. In this study we examine how variation in CO2 abundance affected competition between Fe(III) and SO42--reducers in anoxic bioreactors inoculated with a mixed-microbial community from a freshwater aquifer. We performed two sets of experiments: one with low CO2 partial pressure (∼0.02 atm) in the headspace of the reactors and one with high CO2 partial pressure (∼1 atm). A fluid residence time of 35 days was maintained in the reactors by replacing one-fifth of the aqueous volume with fresh medium every seven days. The aqueous medium was composed of groundwater amended with small amounts of acetate (250 μM), phosphate (1 μM), and ammonium (50 μM) to stimulate microbial activity. Synthetic goethite (1 mmol) and SO42- (500 μM influent concentration) were also available in each reactor to serve as electron acceptors. Results of this study show that higher CO2 abundance increased the ability of Fe(III) reducers to compete with SO42- reducers, leading to significant shifts in CO2 trapping and water quality. Mass-balance calculations and pyrosequencing results demonstrate that SO42- reducers were dominant in reactors with low CO2 content. They consumed 85% of the acetate after acetate consumption reached steady state while Fe(III) reducers consumed only 15% on average. In contrast, Fe(III) reducers were dominant during that same interval in reactors with high CO2 content, consuming at least 90% of the acetate while SO42- reducers consumed a negligible amount (bioreactors enhanced CO2 solubility trapping relative to the low-CO2 bioreactors by increasing alkalinity generation (6X). Hence, the shift in microbial activity we observed was a positive feedback on CO2 trapping. More rapid Fe(III) reduction degraded water quality, however, by leading to high Fe(II) concentration.

  8. Biological Nutrient Removal in a Full Scale Anoxic/Anaerobic/Aerobic/Pre-anoxic-MBR Plant for Low C/N Ratio Municipal Wastewater Treatment

    Institute of Scientific and Technical Information of China (English)

    胡香; 谢丽; 张善发; 杨殿海

    2014-01-01

    A novel full scale modified A2O (anoxic/anaerobic/aerobic/pre-anoxic)-membrane bioreactor (MBR) plant combined with the step feed strategy was operated to improve the biological nutrient removal (BNR) from low C/N ratio municipal wastewater in Southern China. Transformation of organic carbon, nitrogen and phosphorus, and membrane fouling were investigated. Experimental results for over four months demonstrated good efficiencies for chemical oxygen demand (COD) and 4NH+-N removal, with average values higher than 84.5%and 98.1%, re-spectively. A relatively higher total nitrogen (TN) removal efficiency (52.1%) was also obtained at low C/N ratio of 3.82, contributed by the configuration modification (anoxic zone before anaerobic zone) and the step feed with a distribution ratio of 1︰1. Addition of sodium acetate into the anoxic zone as the external carbon source, with a theoretical amount of 31.3 mg COD per liter in influent, enhanced denitrification and the TN removal efficiency in-creased to 74.9%. Moreover, the total phosphate (TP) removal efficiency increased by 18.0%. It is suggested that the external carbon source is needed to improve the BNR performance in treating low C/N ratio municipal waste-water in the modified A2O-MBR process.

  9. Arsenic geochemistry of groundwater in Southeast Asia.

    Science.gov (United States)

    Kim, Kyoung-Woong; Chanpiwat, Penradee; Hanh, Hoang Thi; Phan, Kongkea; Sthiannopkao, Suthipong

    2011-12-01

    The occurrence of high concentrations of arsenic in the groundwater of the Southeast Asia region has received much attention in the past decade. This study presents an overview of the arsenic contamination problems in Vietnam, Cambodia, Lao People's Democratic Republic and Thailand. Most groundwater used as a source of drinking water in rural areas has been found to be contaminated with arsenic exceeding the WHO drinking water guideline of 10 μg·L(-1). With the exception of Thailand, groundwater was found to be contaminated with naturally occurring arsenic in the region. Interestingly, high arsenic concentrations (> 10 μg·L(-1)) were generally found in the floodplain areas located along the Mekong River. The source of elevated arsenic concentrations in groundwater is thought to be the release of arsenic from river sediments under highly reducing conditions. In Thailand, arsenic has never been found naturally in groundwater, but originates from tin mining activities. More than 10 million residents in Southeast Asia are estimated to be at risk from consuming arsenic-contaminated groundwater. In Southeast Asia, groundwater has been found to be a significant source of daily inorganic arsenic intake in humans. A positive correlation between groundwater arsenic concentration and arsenic concentration in human hair has been observed in Cambodia and Vietnam. A substantial knowledge gap exists between the epidemiology of arsenicosis and its impact on human health. More collaborative studies particularly on the scope of public health and its epidemiology are needed to conduct to fulfill the knowledge gaps of As as well as to enhance the operational responses to As issue in Southeast Asian countries.

  10. Production of fluorescent dissolved organic matter in Arctic Ocean sediments

    Science.gov (United States)

    Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin

    2016-12-01

    Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R2 > 0.96, p  0.95, p oceans.

  11. Groundwater Managment Districts

    Data.gov (United States)

    Kansas Data Access and Support Center — This dataset outlines the location of the five Groundwater Management Districts in Kansas. GMDs are locally formed and elected boards for regional groundwater...

  12. Anoxic stress and rapid cold hardening enhance cold tolerance of the migratory locust.

    Science.gov (United States)

    Cui, Feng; Wang, Hongsheng; Zhang, Hanying; Kang, Le

    2014-10-01

    Anoxia and rapid cold hardening (RCH) can increase the cold tolerance of many animals. However, mechanisms underlying these two kinds of stresses remain unclear. In this study, we aimed to explore the relationship of acclimation to cold stress with acclimation to anoxic stress in the migratory locust, Locusta migratoria. RCH at 0°C for 3h promoted the survival of cold stress-exposed locusts. Anoxic hypercapnia (CO2 anoxic treatment) for 40 min exerted an effect similar to that of RCH. Anoxic hypercapnia within 1h can all promote the cold hardiness of locusts. We investigated the transcript levels of six heat shock protein (Hsp) genes, namely, Hsp20.5, Hsp20.6, Hsp20.7, Hsp40, Hsp70, and Hsp90. Four genes, namely, Hsp90, Hsp40, Hsp20.5, and Hsp20.7, showed differential responses to RCH and anoxic hypercapnia treatments. Under cold stress, locusts exposed to the two regimens showed different responses for Hsp90, Hsp20.5, and Hsp20.7. However, the varied responses disappeared after recovery from cold stress. Compared with the control group, the transcript levels of six Hsp genes were generally downregulated in locusts subjected to anoxic hypercapnia or/and RCH. These results indicate that anoxic stress and RCH have different mechanisms of regulating the transcription of Hsp family members even if the two treatments exerted similar effects on cold tolerance of the migratory locust. However, Hsps may not play a major role in the promotion of cold hardiness by the two treatments.

  13. Eddy correlation measurements of submarine groundwater discharge

    Science.gov (United States)

    Crusius, J.; Berg, P.; Koopmans, D.J.; Erban, L.

    2008-01-01

    This paper presents a new, non-invasive means of quantifying groundwater discharge into marine waters using an eddy correlation approach. The method takes advantage of the fact that, in virtually all aquatic environments, the dominant mode of vertical transport near the sediment-water interface is turbulent mixing. The technique thus relies on measuring simultaneously the fluctuating vertical velocity using an acoustic Doppler velocimeter and the fluctuating salinity and/or temperature using rapid-response conductivity and/or temperature sensors. The measurements are typically done at a height of 5-15??cm above the sediment surface, at a frequency of 16 to 64??Hz, and for a period of 15 to 60??min. If the groundwater salinity and/or temperature differ from that of the water column, the groundwater specific discharge (cm d- 1) can be quantified from either a heat or salt balance. Groundwater discharge was estimated with this new approach in Salt Pond, a small estuary on Cape Cod (MA, USA). Estimates agreed well with previous estimates of discharge measured using seepage meters and 222Rn as a tracer. The eddy correlation technique has several desirable characteristics: 1) discharge is quantified under in-situ hydrodynamic conditions; 2) salinity and temperature can serve as two semi-independent tracers of discharge; 3) discharge can be quantified at high temporal resolution, and 4) long-term records of discharge may be possible, due to the low power requirements of the instrumentation. ?? 2007 Elsevier B.V. All rights reserved.

  14. 16S rRNA-based bacterial diversity in the organic-rich sediments underlying oxygen-deficient waters of the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Divya, B.; Parvathi, A.; LokaBharathi, P.A.; Nair, S.

    ). Bootstrap analysis was carried out using 1000 iterations. Diversity analysis The clone library of AS-OMZ was compared with those of other anoxic sediments from Gulf of Mexico, North Sea and South China Sea (28, 60 and 87 sequences, respectively.... Figure 2d Bacterial diversity and richness To understand the bacterial diversity and richness of the AS-OMZ sediment clone library, comparisons were made with suboxic sediment clone libraries from South China Sea, North Sea and Gulf of Mexico...

  15. Biogeochemistry of pyrite and iron sulfide oxidation in marine sediments

    DEFF Research Database (Denmark)

    Schippers, A.; Jørgensen, BB

    2002-01-01

    Pyrite (FeS2) and iron monosulfide (FeS) play a central role in the sulfur and iron cycles of marine sediments, They may be buried in the sediment or oxidized by O-2 after transport by bioturbation to the sediment surface. FeS2 and FeS may also be oxidized within the anoxic sediment in which NO3......-, Fe(III) oxides, or MnO2 are available as potential electron acceptors. In chemical experiments, FeS2 and FeS were oxidized by MnO2 but not with NO3- or amorphous Fe(III) oxide (Schippers and Jørgensen, 2001). Here we also show that in experiments with anoxic sediment slurries, a dissolution of tracer......-marked (FeS2)-Fe-55 occurred with MnO2 but not with NO3- or amorphous Fe(III) oxide as electron acceptor. To study a thermodynamically possible anaerobic microbial FeS, and FeS oxidation with NO3- or amorphous Fe(III) oxide as electron acceptor, more than 300 assays were inoculated with material from several...

  16. Intermittent Elevated Radium Concentrations in Coastal Plain Groundwater of South Carolina, U.S.A.

    Energy Technology Data Exchange (ETDEWEB)

    Denham, Miles; Millings, Margaret; Noonkester, Jay

    2005-09-22

    To learn the cause of intermittent radium concentrations in groundwater of Coastal Plain aquifers, 31 groundwater wells in South Carolina, U.S.A. were sampled for radium and other geochemical parameters. Sediments cored from near the well screens were also sampled to examine any relationship between sediment properties and radium concentration in the groundwater. Elevated radium concentrations only occurred in groundwater with low electrical conductivity and pH values below 6.3. The adsorption edge for radium on hematite--a major surface active mineral in these aquifers--is at a pH value of about 6. Near this value, small changes in pH can result in significant adsorption or desorption of radium. In groundwater with initially low alkalinity, small intermittent decreases in partial pressure of carbon dioxide in groundwater cause decreases in pH and desorption of radium. The result is intermittent elevated radium concentrations.

  17. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2...

  18. Control of phosphorus concentration through adsorption and desorption in shallow groundwater of subtropical carbonate estuary

    Science.gov (United States)

    Flower, Hilary; Rains, Mark; Lewis, David; Zhang, Jia-Zhong; Price, René

    2016-02-01

    The changes in the proportion of fresh and marine water sources in coastal mixing zones can affect phosphorus (P) availability, one of the important drivers of primary productivity. This study focuses on an abiotic portion of the P cycle in the mangrove ecotone of Taylor Slough, coastal Everglades, Florida. We investigated the P sorption properties of sediment with three distinct water sources in this region: 1) fresh groundwater from the inland Everglades, 2) bicarbonate enriched groundwater from the mangrove ecotone, and 3) surface saltwater from Florida Bay. Soluble reactive P (SPR) in ecotone groundwater exhibit markedly low sorption efficiency (Kd = 0.2 L g-1) onto the sediment compared to fresh groundwater and Florida Bay water (11.3 L g-1 and 3.4 L g-1, respectively). The low SRP buffering capacity of the sediment in ecotone groundwater would maintain a higher ambient water SRP concentration in ecotone groundwater than in the other two waters. The relative sorption efficiency is consistent with the measured zero equilibrium SRP concentration being highest in ecotone groundwater (0.094 ± 0.003 μM) and lower in fresh groundwater and Florida Bay surface water (0.075 ± 0.005 μM and 0.058 ± 0.004 μM, respectively). The temporal variability of SRP concentration in groundwater at the ecotone field station is greater than the range of zero equilibrium SRP concentration for all three waters, so very low SRP concentration in the ambient water would induce desorption of P from the sediment. Such desorption processes would result in a higher ambient SRP concentration in ecotone groundwater than the other two water types. Our results suggest that ecotone groundwater, due to its higher bicarbonate content, would release more SRP from mangrove sediments compared to the upstream and downstream waters, as evidenced by both its lower P sorption efficiency and its higher zero equilibrium SRP concentration.

  19. Screening Effect of the Diffusive Boundary Layer in Sediments of Lake Aha in the Suburbs of Guiyang City,Guizhou Province

    Institute of Scientific and Technical Information of China (English)

    万国江; 万曦; 等

    1997-01-01

    The redox cycle of iron and manganese is a major geochemica process at the boundary layers of lake sediments.Lake Aha,which lies in the suburbs of Guiyang City,Guizhou Province,China,is a medium-sized artificial reservoir with seasonally anoxic hypolimnion,Long-term sedimentary accumulation of iron and manganese resulted in their enrichment in the upper sediments,In the anoxic season,Fe2+ and Mn2+,formed by diological oxidation,would diffuse up to overlying waters from sediments.However,the concentration of oxidation,would diffuse up to overlying waters from sediments,However,the concentration of Fe2+ increased later and decreased earlier than that of Mn2+.Generally,sulfate reduction occurred at 6 cm below the sediment-water interface.Whereas,in the anoxic season.the reduction reached upper sediments,inhibiting the release of Fe2+,The Fe concentration of anoxic water is quickly decreased from high to low as a result of reduction of the suplhur system.

  20. Microbial transformations of arsenic: Mobilization from glauconitic sediments to water

    Science.gov (United States)

    Mumford, Adam C.; Barringer, Julia L.; Benzel, William M.; Reilly, Pamela A.; Young, L.Y.

    2012-01-01

    In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33–90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 μg/L. Microcosms developed from site sediments released 23 μg/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site.

  1. A Modified Oxidation Ditch with Additional Internal Anoxic Zones for Enhanced Biological Nutrient Removal

    Institute of Scientific and Technical Information of China (English)

    LIU Wei; YANG Dianhai; XU Li; SHEN Changming

    2013-01-01

    A novel modified pilot scale anaerobic oxidation ditch with additional internal anoxic zones was operated experimentally,aiming to study the improvement of biological nitrogen and phosphorus removal and the effect of enhanced denitrifying phosphorus removal in the process.Under all experimental conditions,the anaerobic-oxidation ditch with additional internal anoxic zones and an internal recycle ratio of 200% had the highest nutrient removal efficiency.The effluent NH+4-N,total nitrogen(TN),PO34--P and total phosphorus(TP)contents were 1.2 mg·L-1,13 mg·L-1,0.3 mg·L-1 and 0.4 mg·L-1,respectively,all met the discharge standards in China.The TN and TP removal efficiencies were remarkably improved from 37% and 50% to 65% and 88% with the presence of additional internal anoxic zones and internal recycle ratio of 200%.The results indicated that additional internal anoxic zones can optimize the utilization of available carbon source from the anaerobic outflow for denitrification.It was also found that phosphorus removal via the denitrification process was stimulated in the additional internal anoxic zones,which was beneficial for biological nitrogen and phosphorus removal when treating wastewater with a limited carbon source.However,an excess internal recycle would cause nitrite to accumulate in the system.This seems to be harmful to biological phosphorus removal.

  2. Positive role of nitrite as electron acceptor on anoxic denitrifying phosphorus removal process

    Institute of Scientific and Technical Information of China (English)

    HUANG RongXin; LI Dong; LI XiangKun; BAO LinLin; JIANG AnXi; ZHANG Jie

    2007-01-01

    Literatures revealed that the electron acceptor-nitrite could be inhibitory or toxic in the denitrifying phosphorus removal process.Batch test experiments were used to investigate the inhibitory effect during the anoxic condition.The inoculated activated sludge was taken from a continuous double- sludge denitrifying phosphorus and nitrogen removal system.Nitrite was added at the anoxic stage.One time injection and sequencing batch injection were carried on in the denitrifying dephosphorus procedure.The results indicated that the nitrite concentration higher than 30 mg/L would inhibit the anoxic phosphate uptake severely, and the threshold inhibitory concentration was dependent on the characteristics of the activated sludge and the operating conditions; instead, lower than the inhibitory concentration would not be detrimental to anoxic phosphorus uptake, and it could act as good electron acceptor for the anoxic phosphate accumulated.Positive effects performed during the denitrifying biological dephosphorus all the time.The utility of nitrite as good electron acceptor would provide a new feasible way in the denitrifying phosphorus process.

  3. Nitrate, nitrite, and nitrous oxide transformations in sediments along a salinity gradient in the Weser Estuary

    DEFF Research Database (Denmark)

    Nielsen, Michael; Gieseke, Armin; de Beer, Dirk

    2009-01-01

    The dynamics of the nitrogen intermediates N2O and NO2- in estuarine sediments were studied along a salinity gradient in the eutrophied Weser Estuary (Germany) using microsensors for N2O, NO2-, NOx-, and O2. During dark incubations in the laboratory of sediment samples from a freshwater site......, a brackish water site with fluctuating salinity, and a marine site, the effects of environmental changes in nitrogen availability and salinity on microscale sediment dynamics were examined. Generally, sediment levels of intermediates were low: 1 to 25 µM NO2- and 0 to 8 µM N2O. However, significant variation...... change in either NO3- or salinity, and was found in anoxic or micro-oxic sediment layers. Because oxic sediment layers showed little or no potential for N2O consumption (in contrast to NO2-) the accumulation of N2O always resulted in release from the sediment surface. Results demonstrate that changes...

  4. High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle

    Science.gov (United States)

    Them, T. R.; Gill, B. C.; Caruthers, A. H.; Gröcke, D. R.; Tulsky, E. T.; Martindale, R. C.; Poulton, T. P.; Smith, P. L.

    2017-02-01

    The Mesozoic Era experienced several instances of abrupt environmental change that are associated with instabilities in the climate, reorganizations of the global carbon cycle, and elevated extinction rates. Often during these perturbations, oxygen-deficient conditions developed in the oceans resulting in the widespread deposition of organic-rich sediments - these events are referred to as Oceanic Anoxic Events or OAEs. Such events have been linked to massive injections of greenhouse gases into the ocean-atmosphere system by transient episodes of voluminous volcanism and the destabilization of methane clathrates within marine environments. Nevertheless, uncertainty surrounds the specific environmental drivers and feedbacks that occurred during the OAEs that caused perturbations in the carbon cycle; this is particularly true of the Early Jurassic Toarcian OAE (∼183.1 Ma). Here, we present biostratigraphically constrained carbon isotope data from western North America (Alberta and British Columbia, Canada) to better assess the global extent of the carbon cycle perturbations. We identify the large negative carbon isotope excursion associated with the OAE along with high-frequency oscillations and steps within the onset of this excursion. We propose that these high-frequency carbon isotope excursions reflect changes to the global carbon cycle and also that they are related to the production and release of greenhouse gases from terrestrial environments on astronomical timescales. Furthermore, increased terrestrial methanogenesis should be considered an important climatic feedback during Ocean Anoxic Events and other similar events in Earth history after the proliferation of land plants.

  5. Nitric oxide turnover in permeable river sediment

    DEFF Research Database (Denmark)

    Schreiber, Frank; Stief, Peter; Kuypers, Marcel M M;

    2014-01-01

    We measured nitric oxide (NO) microprofiles in relation to oxygen (O2) and all major dissolved N-species (ammonium, nitrate, nitrite, and nitrous oxide [N2O]) in a permeable, freshwater sediment (River Weser, Germany). NO reaches peak concentrations of 0.13 μmol L-1 in the oxic zone and is consumed...... in the oxic-anoxic transition zone. Apparently, NO is produced by ammonia oxidizers under oxic conditions and consumed by denitrification under microoxic conditions. Experimental percolation of sediment cores with aerated surface water resulted in an initial rate of NO production that was 12 times higher than...... the net NO production rate in steady state. This initial NO production rate is in the same range as the net ammonia oxidation rate, indicating that NO is transiently the main product of ammonia oxidizers. Stable isotope labeling experiments with the 15N-labeled chemical NO donor S...

  6. Redox oscillation affecting mercury mobility from highly contaminated coastal sediments: a mesocosm incubation experiment

    Directory of Open Access Journals (Sweden)

    Emili A.

    2013-04-01

    Full Text Available Mercury (Hg mobility at the sediment-water interface was investigated during a laboratory incubation experiment on highly contaminated sediments (up to 23 μg g−1 of the Gulf of Trieste. Undisturbed sediment was collected in front of the Isonzo River mouth, which inflows Hg-rich suspended material originating from the Idrija (NW Slovenia mining district. Since hypoxic and anoxic conditions at the bottom are frequently observed, a redox oscillation was simulated in the laboratory at in situ temperature, using a dark flux chamber. Temporal variations of several parameters were monitored simultaneously: dissolved Hg and methylmercury (MeHg, O2, NH4+, NO3−+NO2−, PO43−, H2S, dissolved Fe and Mn, dissolved inorganic and organic carbon (DIC and DOC. Benthic fluxes of Hg and MeHg were higher under anoxic conditions while re-oxygenation caused concentrations of MeHg and Hg to rapidly drop, probably due to re-adsorption onto Fe/Mn oxyhydroxides and enhanced demethylation. Hence, during anoxic events, sediments of the Gulf of Trieste may be considered as an important source of dissolved Hg species for the water column. However, re-oxygenation of the bottom compartment mitigates Hg and MeHg release from the sediment, thus acting as a natural “defence” from possible interaction between the metal and the aquatic organisms.

  7. Denitrification coupled to pyrite oxidation and changes in groundwater quality in a shallow sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Slomp, C.P.; Broers, H.P.; Passier, H.F.; Cappellen, P. van

    2009-01-01

    This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating (3H/3He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherland

  8. Groundwater flow paths in a glacially affected flat area in the Netherlands

    NARCIS (Netherlands)

    Dijksma, R.; Menkveld, S.H.; Bier, G.; Osterhof, A.T.

    2015-01-01

    Well field Garyp is abstracting deep groundwater from fluvioglacial sediments, which are covered by glacio-lacustrine clay. This drinking water abstraction is hampered by rapid salinization of the abstraction wells. A detailed ground-water modelling study was done, to reveal the water pathways and t

  9. Distribution of microbial biomass and the potential for anaerobic respiration in Hanford Site 300 Area subsurface sediment

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Xueju; Kennedy, David W.; Peacock, Aaron D.; McKinley, James P.; Resch, Charles T.; Fredrickson, Jim K.; Konopka, Allan

    2012-02-01

    Subsurface sediments were recovered from a 52 m deep borehole cored in the 300 Area of the Hanford Site in southeastern Washington State to assess the potential for biogeochemical transformation of radionuclide contaminants. Microbial analyses were made on 17 sediment samples traversing multiple geological units: the oxic coarse-grained Hanford formation (9-17.4 m), the oxic fine-grained upper Ringold Formation (17.7-18.1 m), and the reduced Ringold Formation (18.3-52m). Microbial biomass (measured as phospholipid) ranged from 7-974 pmols per g in discrete samples, with the highest numbers found in the Hanford formation. On average, strata below 17.4 m had 13-fold less biomass than those from shallower strata. The nosZ gene encoding nitrous oxide reductase had an abundance of 5-17% relative to total 16S rRNA genes below 18.3 m and <5% above 18.1 m. Most nosZ sequences were affiliated with Ochrobactrum anthropi (97% sequence similarity) or had a nearest neighbor of Achromobacter xylosoxidans (90% similarity). Passive multilevel sampling of groundwater geochemistry demonstrated a redox gradient in the 1.5 m region between the Hanford-Ringold formation contact and the Ringold oxic-anoxic interface. Within this zone, copies of the dsrA gene and Geobacteraceae had the highest relative abundance. The majority of dsrA genes detected near the interface were related to Desulfotomaculum sp.. These analyses indicate that the region just below the contact between the Hanford and Ringold formations is a zone of active biogeochemical redox cycling.

  10. Combined DNA and lipid analyses of sediments reveal changes in Holocene phytoplankton populations in an Antarctic lake

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Coolen, M.J.L.; Muyzer, G.; Rijpstra, W.I.C.; Schouten, S.; Volkman, J.K.

    2004-01-01

    Preserved ribosomal DNA of planktonic phototrophic algae was recovered from Holocene anoxic sediments of Ace Lake (Antarctica), and the ancient community members were identified based on comparative sequence analysis. The similar concentration profiles of DNA of haptophytes and their traditional lip

  11. Effects of soil erosion and anoxic-euxinic ocean in the Permian-Triassic marine crisis.

    Science.gov (United States)

    Kaiho, Kunio; Saito, Ryosuke; Ito, Kosuke; Miyaji, Takashi; Biswas, Raman; Tian, Li; Sano, Hiroyoshi; Shi, Zhiqiang; Takahashi, Satoshi; Tong, Jinnan; Liang, Lei; Oba, Masahiro; Nara, Fumiko W; Tsuchiya, Noriyoshi; Chen, Zhong-Qiang

    2016-08-01

    The largest mass extinction of biota in the Earth's history occurred during the Permian-Triassic transition and included two extinctions, one each at the latest Permian (first phase) and earliest Triassic (second phase). High seawater temperature in the surface water accompanied by euxinic deep-intermediate water, intrusion of the euxinic water to the surface water, a decrease in pH, and hypercapnia have been proposed as direct causes of the marine crisis. For the first-phase extinction, we here add a causal mechanism beginning from massive soil and rock erosion and leading to algal blooms, release of toxic components, asphyxiation, and oxygen-depleted nearshore bottom water that created environmental stress for nearshore marine animals. For the second-phase extinction, we show that a soil and rock erosion/algal bloom event did not occur, but culmination of anoxia-euxinia in intermediate waters did occur, spanning the second-phase extinction. We investigated sedimentary organic molecules, and the results indicated a peak of a massive soil erosion proxy followed by peaks of marine productivity proxy. Anoxic proxies of surface sediments and water occurred in the shallow nearshore sea at the eastern and western margins of the Paleotethys at the first-phase extinction horizon, but not at the second-phase extinction horizon. Our reconstruction of ocean redox structure at low latitudes indicates that a gradual increase in temperature spanning the two extinctions could have induced a gradual change from a well-mixed oxic to a stratified euxinic ocean beginning immediately prior to the first-phase extinction, followed by culmination of anoxia in nearshore surface waters and of anoxia and euxinia in the shallow-intermediate waters at the second-phase extinction over a period of approximately one million years or more. Enhanced global warming, ocean acidification, and hypercapnia could have caused the second-phase extinction approximately 60 kyr after the first

  12. Organic geochemistry of the early Toarcian oceanic anoxic event in Hawsker Bottoms, Yorkshire, England

    Science.gov (United States)

    French, K. L.; Sepúlveda, J.; Trabucho-Alexandre, J.; Gröcke, D. R.; Summons, R. E.

    2014-03-01

    A comprehensive organic geochemical investigation of the Hawsker Bottoms outcrop section in Yorkshire, England has provided new insights about environmental conditions leading into and during the Toarcian oceanic anoxic event (T-OAE; ∼183 Ma). Rock-Eval and molecular analyses demonstrate that the section is uniformly within the early oil window. Hydrogen index (HI), organic petrography, polycyclic aromatic hydrocarbon (PAH) distributions, and tricyclic terpane ratios mark a shift to a lower relative abundance of terrigenous organic matter supplied to the sampling locality during the onset of the T-OAE and across a lithological transition. Unlike other ancient intervals of anoxia and extinction, biomarker indices of planktonic community structure do not display major changes or anomalous values. Depositional environment and redox indicators support a shift towards more reducing conditions in the sediment porewaters and the development of a seasonally stratified water column during the T-OAE. In addition to carotenoid biomarkers for green sulfur bacteria (GSB), we report the first occurrence of okenane, a marker of purple sulfur bacteria (PSB), in marine samples younger than ∼1.64 Ga. Based on modern observations, a planktonic source of okenane's precursor, okenone, would require extremely shallow photic zone euxinia (PZE) and a highly restricted depositional environment. However, due to coastal vertical mixing, the lack of planktonic okenone production in modern marine sulfidic environments, and building evidence of okenone production in mat-dwelling Chromatiaceae, we propose a sedimentary source of okenone as an alternative. Lastly, we report the first parallel compound-specific δC13 record in marine- and terrestrial-derived biomarkers across the T-OAE. The δC13 records of short-chain n-alkanes, acyclic isoprenoids, and long-chain n-alkanes all encode negative carbon isotope excursions (CIEs), and together, they support an injection of isotopically light

  13. Integrated stratigraphy of the Cenomanian-Turonian boundary interval: improving understanding of Oceanic Anoxic Events

    Science.gov (United States)

    Jarvis, Ian

    2014-05-01

    The Cenomanian-Turonian boundary (CTB) interval ~ 94 Ma represented a period of major global palaeoenvironmental change. Increasingly detailed multidisciplinary studies integrating sedimentological, palaeontological and geochemical data from multiple basins, are enabling the development of refined but complex models that aid understanding of the mechanisms driving changes in ocean productivity and climate. This paper reviews some of the exciting new developments in this field. Facies change characterizes the CTB interval in most areas. In the Chalk seas of northern Europe, a widespead hiatus was followed by the deposition of clay-rich organic-lean beds of the Plenus Marl and its equivalents, and then nodular chalks. In the North Sea basin and its onshore extension in eastern England and northern Germany, black shales of the Black Band (Blodøks Formation, Hasseltal Formation) occur. Similarly, in northern Tethys, a brief interval of black shale accumulation within a predominantly carbonate succession, is exemplified by the Niveau Thomel in the Vocontian Basin (SE France), and the Livello Bonarelli in Italy. Widespread deposition of organic-rich marine sediments during CTB times led to 12C depletion in surface carbon reservoirs (oceans, atmosphere, biosphere), and a large positive global δ13C excursion preserved in marine carbonates and both marine and terrestrial organic matter (Oceanic Anoxic Event 2). Significant biotic turnover characterises the boundary interval, and inter-regional correlation may be achieved at high resolution using integrated biostratigraphy employing macrofossils (ammonites, inoceramid bivalves), microfossils (planktonic foraminifera, dinoflagellate cysts) and calcareous nannofossils. Correlations can be tested against those based on comparison of δ13C profiles - carbon isotope chemostratigraphy, supplemented by oxygen isotope and elemental data. Interpretation of paired carbonate - organic matter δ13C data from multiple CTB sections

  14. Batroxobin Against Anoxic Damage of Rat Hippocampal Neurons in Culture: Morphological Changes and Hsp70 Expression

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@Batroxobin,the thrombin-like enzyme,is used for therapeutic defibrination. We have found that batroxobin has good therapeutic effect in ischemic reperfusion rats and clinical practices in vivo. But we have not studied the neuroprotective effect of batroxobin on anoxic hippocampal neurons in vitro. The purpose of this study was to obtain further information on the mechanism of the batroxobin-induced neuroprotection and examine the neuroprotective effect on neurons exposed to anoxia. The effect of batroxobin on anoxic damages in cultured hippocampal neurons of neonatal rats was investigated by using morphological changes and heat shock protein 70Kd (Hsp70) immunoreactive expression as indicators. The results indicate that batroxobin, besides its defibrination, may have a direct neuroprotective effect on anoxic damage of hippocampal neurons.

  15. Inhibition of Sporosarcina pasteurii under anoxic conditions: implications for subsurface carbonate precipitation and remediation via ureolysis.

    Science.gov (United States)

    Martin, Derek; Dodds, Kevin; Ngwenya, Bryne T; Butler, Ian B; Elphick, Stephen C

    2012-08-07

    The use of Sporosarcina pasteurii to precipitate calcium carbonate in the anoxic subsurface via ureolysis has been proposed for reducing porosity and sealing fractures in rocks. Here we show that S. pasteurii is unable to grow anaerobically and that the ureolytic activity previously shown under anoxic conditions is a consequence of the urease enzyme already present in the cells of the aerobically grown inoculum. The implications are discussed, suggesting that de novo synthesis of urease under anoxic conditions is not possible and that ureolysis may decline over time without repeated injection of S. pasteurii as the urease enzyme degrades and/or becomes inhibited. Augmentation with a different ureolytic species that is able to grow anaerobically or stimulation of natural communities may be preferable for carbonate precipitation over the long term.

  16. A comparative study of phosphate sorption in lowland soils under oxic and anoxic conditions

    DEFF Research Database (Denmark)

    Heiberg, Lisa; Pedersen, Thomas Vils; Jensen, Henning S.;

    2010-01-01

    of 36 to 93% of the dithionite-extractable FeIII (FeBD). Langmuir fitted Pi sorption isotherms showed a Pi release of up to 1.1 mmol kg-1 in six soils when Pi concentrations in the matrix (Psol) were lower than 10 µM. Phosphate desorption was attributed to dissolution of amorphous iron oxides......Received for publication June 13, 2009. Phosphate (Pi) release due to FeIII oxide dissolution is well documented for soils undergoing reduction. The Pi sorption properties of soils in anoxic conditions are, however, still under consideration. In this investigation, Pi sorption to strictly anoxic...... FeII phosphates may have caused the higher sorption capacities. Use of maximum sorption capacity (Smax) is therefore misleading as a measure of Pi sorption at low Psol concentrations. The results demonstrate that none of the strongly anoxic soils, irrespective of the initial FeIII oxide content...

  17. Theoretical evaluation on nitrogen removal of step-feed anoxic/oxic activated sludge process

    Institute of Scientific and Technical Information of China (English)

    ZHU Gui-bing; PENG Yong-zhen

    2006-01-01

    Evaluation on nitrogen removal of step-feed anoxic/oxic activated sludge process at the standpoint of reaction kinetics and process kinetics was conducted. Theoretical biological nitrogen removal efficiency was deduced based on the mass balance of nitrate in the last stage. The comparison of pre-denitrification process and step feed process in the aspects of nitrogen removal efficiency, volume of reactor and building investment was studied, and the results indicated that step-feed anoxic/oxic activated sludge process was superior to pre-denitrification process in these aspects.

  18. Hydrology and Ground-Water Quality in the Mine Workings within the Picher Mining District, Northeastern Oklahoma, 2002-03

    Science.gov (United States)

    DeHay, Kelli L.; Andrews, William J.; Sughru, Michael P.

    2004-01-01

    The Picher mining district of northeastern Ottawa County, Oklahoma, was a major site of mining for lead and zinc ores in the first half of the 20th century. The primary source of lead and zinc were sulfide minerals disseminated in the cherty limestones and dolomites of the Boone Formation of Mississippian age, which comprises the Boone aquifer. Ground water in the aquifer and seeping to surface water in the district has been contaminated by sulfate, iron, lead, zinc, and several other metals. The U.S. Geological Survey, in cooperation with the Oklahoma Department of Environmental Quality, investigated hydrology and ground-water quality in the mine workings in the mining district, as part of the process to aid water managers and planners in designing remediation measures that may restore the environmental quality of the district to pre-mining conditions. Most ground-water levels underlying the mining district had similar altitudes, indicating a large degree of hydraulic connection in the mine workings and overlying aquifer materials. Recharge-age dates derived from concentrations of chlorofluorocarbons and other dissolved gases indicated that water in the Boone aquifer may flow slowly from the northeast and southeast portions of the mining district. However, recharge-age dates may have been affected by the types of sites sampled, with more recent recharge-age dates being associated with mine-shafts, which are more prone to atmospheric interactions and surface runoff than the sampled airshafts. Water levels in streams upstream from the confluence of Tar and Lytle Creeks were several feet higher than those in adjacent portions of the Boone aquifer, perhaps due to low-permeability streambed sediments and indicating the streams may be losing water to the aquifer in this area. From just upstream to downstream from the confluence of Tar and Lytle Creeks, surface-water elevations in these streams were less than those in the surrounding Boone aquifer, indicating that

  19. Influence of an aerobic sediment-water interface in relation to reduced risk of phosphorus leaching from re-established wetlands

    DEFF Research Database (Denmark)

    Forsmann, Ditte M.; Kjærgaard, Charlotte

    water interactions are of fundamental importance for the biogeochemical processes controlling phosphorus dynamics in wetlands, and different hydrological pathways such as groundwater discharge and surface water flooding are operating within wetlands (Hoffmann et al., 2009). During groundwater discharge...... water passes through the wetland sediment and carry soluble iron and phosphorus by convection to the sediment-water interface. During surface water flooding phosphorus fluxes from the sediment will be dominated by diffuse fluxes. The eventual loss of phosphorus mobilized within the anaerobic sediment...

  20. Establishment of Groundwater Arsenic Potential Distribution and Discrimination in Taiwan

    Science.gov (United States)

    Tsai, Kuo Sheng; Chen, Yu Ying; Chung Liu, Chih; Lin, Chien Wen

    2016-04-01

    According to the last 10 years groundwater monitoring data in Taiwan, Arsenic concentration increase rapidly in some areas, similar to Bengal and India, the main source of Arsenic-polluted groundwater is geological sediments, through reducing reactions. There are many researches indicate that high concentration of Arsenic in groundwater poses the risk to water safety, for example, the farm lands irrigation water contains Arsenic cause the concentration of Arsenic increase in soil and crops. Based on the management of water usage instead of remediation in the situation of insufficient water. Taiwan EPA has been developed the procedures of Arsenic contamination potential area establishment and source discriminated process. Taiwan EPA use the procedures to determine the management of using groundwater, and the proposing usage of Arsenic groundwater accordance with different objects. Agencies could cooperate with the water quality standard or water needs, studying appropriate water purification methods and the groundwater depth, water consumption, thus achieve the goal of water safety and environmental protection, as a reference of policy to control total Arsenic concentration in groundwater. Keywords: Arsenic; Distribution; Discrimination; Pollution potential area of Arsenic; Origin evaluation of groundwater Arsenic

  1. Phloem flow and sugar transport in Ricinus communis L. is inhibited under anoxic conditions of shoot or roots

    NARCIS (Netherlands)

    Peuke, A.D.; Gessler, A.; Trumbore, S.; Windt, C.W.; Homan, N.; Gerkema, E.; As, van H.

    2015-01-01

    Anoxic conditions should hamper the transport of sugar in the phloem, as this is an active process. The canopy is a carbohydrate source and the roots are carbohydrate sinks.By fumigating the shoot with N2 or flooding the rhizosphere, anoxic conditions in the source or sink, respectively, were induce

  2. DYNAMICS OF AGRICULTURAL GROUNDWATER EXTRACTION

    OpenAIRE

    Hellegers, Petra J.G.J.; Zilberman, David; van Ierland, Ekko C.

    2001-01-01

    Agricultural shallow groundwater extraction can result in desiccation of neighbouring nature reserves and degradation of groundwater quality in the Netherlands, whereas both externalities are often not considered when agricultural groundwater extraction patterns are being determined. A model is developed to study socially optimal agricultural shallow groundwater extraction patterns. It shows the importance of stock size to slow down changes in groundwater quality.

  3. Patterns in groundwater chemistry resulting from groundwater flow

    Science.gov (United States)

    Stuyfzand, Pieter J.

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic-methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500m in the flow direction is shown to correspond with about 5000yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Résumé Les écoulements souterrains influencent les différents types hydrochimiques, parce que l'écoulement réduit le mélange par diffusion, porte les marques chimiques de changements biologiques et anthropiques dans la zone d'alimentation et lessive le système aquifère. Ces types dans leur ensemble sont surtout déterminés par des différences dans le flux d'eau météorique traversant le sous-sol. Dans les "hydrosomes" (masses d'eau d'origine déterminée), les lignes marquant une évolution prograde (séquence de faciès) se développent normalement dans la direction de l'écoulement souterrain : depuis des fluctuations fortes de la

  4. Groundwater sustainability strategies

    Science.gov (United States)

    Gleeson, Tom; VanderSteen, Jonathan; Sophocleous, Marios A.; Taniguchi, Makoto; Alley, William M.; Allen, Diana M.; Zhou, Yangxiao

    2010-01-01

    Groundwater extraction has facilitated significant social development and economic growth, enhanced food security and alleviated drought in many farming regions. But groundwater development has also depressed water tables, degraded ecosystems and led to the deterioration of groundwater quality, as well as to conflict among water users. The effects are not evenly spread. In some areas of India, for example, groundwater depletion has preferentially affected the poor. Importantly, groundwater in some aquifers is renewed slowly, over decades to millennia, and coupled climate–aquifer models predict that the flux and/or timing of recharge to many aquifers will change under future climate scenarios. Here we argue that communities need to set multigenerational goals if groundwater is to be managed sustainably.

  5. Modelling the effects of surface water flood pulses on groundwater

    NARCIS (Netherlands)

    Schot, P.P.; Wassen, M.J.

    2010-01-01

    Flood pulses in wetlands steer ecosystem development directly through surface water processes and indirectly through the effects of the flood pulse on groundwater. Direct effects on ecosystems are exerted by e.g. inundation and deposition of sediments containing nutrients. Indirect effects include t

  6. Targeting sediment management strategies using sediment quantification and fingerprinting methods

    Science.gov (United States)

    Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

    2016-04-01

    statistically un-mixed using FR2000, an uncertainty-inclusive algorithm, and combined with sediment yield data. Results showed sediment contributions from channel, field and road groups were 70%, 25% and 5% in the poorly-drained catchment, 59%, 22% and 19% in the well-drained catchment, and 17%, 74% and 9% in the moderately-drained catchment. Higher channel contributions in the poorly-drained catchment were attributed to bank erosion accelerated by the rapid diversion of surface runoff into channels, facilitated by surface and sub-surface artificial drainage networks, and bank seepage from lateral pressure gradients due to confined groundwater. Despite the greatest proportion of arable soils in the well-drained catchment, this source was frequently hydrologically disconnected as well-drained soils largely infiltrated rainfall and prevented surface soil erosion. Periods of high and intense rainfall were associated with greater proportions of field losses in the well-drained catchment likely due to infiltration exceeding the saturated hydraulic conductivity of soils and establishment of surface hydrological connectivity. Losses from field topsoils dominated in the moderately-drained catchment as antecedent soil wetness maintained surface flow pathways and coincided with low groundcover on arable soils. For cost-effective management of sediment pressures to aquatic ecosystems, catchment specific variations in sediment sources must be considered.

  7. Study of control strategy and simulation in anoxic-oxic nitrogen removal process

    Institute of Scientific and Technical Information of China (English)

    PENG Yong-zhen; WANG Zhi-hui; WANG Shu-ying

    2005-01-01

    The control strategy and simulation of external carbon addition were specially studied in an anoxic-oxic(A/O) process with low carbon: nitrogen(C/N) domestic wastewater. The control strategy aimed to adjust the flow rate of external carbon dosage to the anoxic zone, thus the concentration of nitrate plus nitrite( NOx -N) in the anoxic zone was kept closed to the set point. The relationship was studied between the NOx-N concentration in the anoxic zone(SNo) and the dosage of external carbon, and the results showed that the removal efficiency of the total nitrogen(TN) could not be largely improved by double dosage of carbon source when SNO reached about 2mg/L. Through keeping SNO at the level of about 2 mg/L, the demand of effluent quality could be met and the carbon dosage could be optimized. Based on the Activated Sludge Model No. 1 (ASM No. 1 ), a simplified mathematical model of external carbon dosage was developed. Simulation results showed that PI controller and feed-forward PI controller both had good dynamic response and steady precision. And feed-forward PI controller had better control effects due to its consideration of influent disturbances.

  8. Carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event

    Science.gov (United States)

    Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Hesselbo, Stephen P.; Riding, James B.; Selby, David; Naafs, B. David A.; Weijers, Johan W. H.; Pancost, Richard D.; Tegelaar, Erik W.; Idiz, Erdem F.

    2017-01-01

    The Early Jurassic Toarcian oceanic anoxic event (~183 Ma) was marked by marine anoxia-euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo-Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and environmental change on the continents is poorly understood. Here, utilizing radioisotopic, palynological and geochemical data from lacustrine black shales, we demonstrate that a large lake system developed contemporaneously with the Toarcian oceanic anoxic event in the Sichuan Basin, China, probably due to enhanced hydrological cycling under elevated atmospheric pCO 2. We attribute increased lacustrine organic productivity to elevated fluvial nutrient supply, which resulted in the burial of ~460 Gt of organic carbon in the Sichuan Basin alone, creating an important negative feedback in the global exogenic carbon cycle. We suggest that enhanced nutrient delivery to marine and large lacustrine systems was a key component in the global carbon cycle recovery during the Toarcian oceanic anoxic event and acted to shorten the duration of the recovery of global δ13C values.

  9. Massive expansion of marine archaea during a mid-Cretaceous oceanic anoxic event

    DEFF Research Database (Denmark)

    Kuypers, M.M.M.; Blokker, P.; Erbacher, J.;

    2001-01-01

    Biogeochemical and stable carbon isotopic analysis of black-shale sequences deposited during an Albian oceanic anoxic event (∼112 million years ago) indicate that up to 80 weight percent of sedimentary organic carbon is derived from marine, nonthermophilic archaea. The carbon-13 content of archae...

  10. Effect of a Jurassic oceanic anoxic event on belemnite ecology and evolution

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz; Thibault, Nicolas Rudolph; Ruhl, Micha

    2014-01-01

    The Toarcian oceanic anoxic event (T-OAE; ∼183 million y ago) is possibly the most extreme episode of widespread ocean oxygen deficiency in the Phanerozoic, coinciding with rapid atmospheric pCO2 increase and significant loss of biodiversity in marine faunas. The event is a unique past tipping...

  11. Anoxic survival of Macoma balthica: the effect of antibiotics, molybdate and sulphide

    NARCIS (Netherlands)

    De Zwaan, A.; Schaub, B.; Babarro, J.M.F.

    2001-01-01

    In anoxic semi-closed systems, the survival time of the clam Macoma balthica was compared to clams which were incubated in the presence of several antibiotics (chloramphenicol, 5- oxytetracycline hydrochloride, penicillin, streptomycin. a mix of penicillin and streptomycin and a mix of chloramphenic

  12. Anoxic aggregates - an ephemeral phenomenon in the pelagic environment? RID A-1977-2009

    DEFF Research Database (Denmark)

    Ploug, H.; Kuhl, M.; BuchholzCleven, B.;

    1997-01-01

    of heterotrophic processes would limit anoxic conditions to occurring only over a few hours, depending on the size of the aggregates. Therefore slow-growing obligate anaerobic microorganisms such as sulfate reducing bacteria and methanogenic bacteria may be limited by the relatively short persistence of anoxia...

  13. The effect of anoxic treatment on the larvae of six species of dermestids (Coleoptera)

    DEFF Research Database (Denmark)

    Bergh, J.E.; Hansen, L.S.; Jensen, K.M.V.;

    2003-01-01

    Based on surveys of species of museum pest insects commonly found in Finland, Norway, Denmark and Sweden, six species were selected for a study of the effect of exposure to anoxic treatment on the larval stage. An oxygen level of 0.3% (the rest, nitrogen) was applied and lethal exposure times wer...

  14. Vivianite precipitation and phosphate sorption following iron reduction in anoxic soils

    DEFF Research Database (Denmark)

    Heiberg, Lisa; Bender Koch, Christian; Kjærgaard, Charlotte;

    2012-01-01

    (-1) and EPC0 increased from 1.7 to 83 mu M, after 322 d of anoxic incubation. The fast Fe(III) reduction made the peat soils particularly vulnerable to changes in redox conditions. However, the precipitation of vivianite/metavivianite minerals may control soluble P-i concentrations to between 2 and 3...

  15. Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a

    Science.gov (United States)

    Naafs, B. D. A.; Castro, J. M.; de Gea, G. A.; Quijano, M. L.; Schmidt, D. N.; Pancost, R. D.

    2016-02-01

    During the Aptian Oceanic Anoxic Event 1a, about 120 million years ago, black shales were deposited in all the main ocean basins. The event was also associated with elevated sea surface temperatures and a calcification crisis in calcareous nannoplankton. These environmental changes have been attributed to variations in atmospheric CO2 concentrations, but the evolution of the carbon cycle during this event is poorly constrained. Here we present records of atmospheric CO2 concentrations across Oceanic Anoxic Event 1a derived from bulk and compound-specific δ13C from marine rock outcrops in southern Spain and Tunisia. We find that CO2 concentrations doubled in two steps during the oceanic anoxic event and remained above background values for approximately 1.5-2 million years before declining. The rise of CO2 concentrations occurred over several tens to hundreds of thousand years, and thus was unlikely to have resulted in any prolonged surface ocean acidification, suggesting that CO2 emissions were not the primary cause of the nannoplankton calcification crisis. We find that the period of elevated CO2 concentrations coincides with a shift in the oceanic osmium-isotope inventory associated with emplacement of the Ontong Java Plateau flood basalts, and conclude that sustained volcanic outgassing was the primary source of carbon dioxide during Oceanic Anoxic Event 1a.

  16. Early diagenetic production and sediment-water exchange of fluorescent dissolved organic matter in the coastal environment

    Science.gov (United States)

    Skoog, Annelie; Hall, Per O. J.; Hulth, Stefan; Paxéus, Nicklas; Van Der Loeff, Michiel Rutgers; Westerlund, Stig

    1996-10-01

    Fluorescence at wavelengths characteristic of humic substances (excitation 350 nm, emission 450 nm) have been used in this study to approximate concentrations of fluorescent dissolved organic material (FDOM). In situ regulated and unregulated benthic chambers, sediment cores, and laboratory tank incubations were used to study early diagenesis of FDOM in coastal marine sediments of the Gullmar Fjord, western Sweden. In the regulated in situ chambers, pH and oxygen were kept at relatively stable levels, while in the unregulated in situ chambers, pH and oxygen were left to decrease as a result of biological activity. FDOM porewater distributions and correlation between FDOM and parameters indicating mineralization showed that FDOM was formed in the sediment and should flux across the sediment-water interface. A substantial flux of FDOM was also observed during winter and spring conditions and during anoxic conditions fall. However, no flux was observed during oxic conditions fall. Modeling indicated that oxygen penetration depth was deeper during winter than during fall, i.e., the oxygen penetration depth increased during fall towards winter values. We suggest that as FeOOH was formed when oxygen penetration depths increased, FROM was sorbed to newly formed FeOOH, inhibiting FDOM flux over the sediment-water interface. In addition, at onset of anoxic conditions in the sediment surface layer in fall incubations, FDOM flux from sediment to overlying water increased substantially. Increases in anoxic FDOM fluxes were accompanied by increases in Fe and phosphate fluxes. We suggest that reductively dissolved FeOOH released sorbed FDOM. FDOM released from FeOOH by anoxic conditions was not resorbed when oxic conditions were resumed. This could be an effect of higher pH in overlying water as compared with porewater, inhibiting FeOOH sorption of FDOM.

  17. Characterization of redox conditions in groundwater contaminant plumes

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Bjerg, Poul Løgstrup; Banwarth, Steven A.;

    2000-01-01

    Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few...... cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials...... dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial...

  18. Composition of dissolved organic matter in groundwater

    Science.gov (United States)

    Longnecker, Krista; Kujawinski, Elizabeth B.

    2011-05-01

    Groundwater constitutes a globally important source of freshwater for drinking water and other agricultural and industrial purposes, and is a prominent source of freshwater flowing into the coastal ocean. Therefore, understanding the chemical components of groundwater is relevant to both coastal and inland communities. We used electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to examine dissolved organic compounds in groundwater prior to and after passage through a sediment-filled column containing microorganisms. The data revealed that an unexpectedly high proportion of organic compounds contained nitrogen and sulfur, possibly due to transport of surface waters from septic systems and rain events. We matched 292 chemical features, based on measured mass:charge ( m/z) values, to compounds stored in the Kyoto Encyclopedia of Genes and Genomes (KEGG). A subset of these compounds (88) had only one structural isomer in KEGG, thus supporting tentative identification. Most identified elemental formulas were linked with metabolic pathways that produce polyketides or with secondary metabolites produced by plants. The presence of polyketides in groundwater is notable because of their anti-bacterial and anti-cancer properties. However, their relative abundance must be quantified with appropriate analyses to assess any implications for public health.

  19. Solute transport into the Jiulong River estuary via pore water exchange and submarine groundwater discharge: New insights from 224Ra/228Th disequilibrium

    Science.gov (United States)

    Hong, Qingquan; Cai, Pinghe; Shi, Xiangming; Li, Qing; Wang, Guizhi

    2017-02-01

    Pore water exchange (PEX) and submarine groundwater discharge (SGD) represent two mechanisms for solute transport from the seabed into the coastal ocean. However, their relative importance remains to be assessed. In this study, we pursued the recently developed 224Ra/228Th disequilibrium approach to quantify PEX fluxes of 224Ra into the Jiulong River estuary, China. By constructing a full mass balance of water column 224Ra, we were allowed to put various source terms, i.e., SGD, diffusive and advective pore water flow (PEX), and river input in a single context. This led to the first quantitative assessment of the relative importance of PEX vs. SGD in the delivery of solutes into an estuary. We carried out two surveys in the Jiulong River estuary: one in January 2014 (winter survey), the other in August 2014 (summer survey). By virtue of a 1-D mass balance model of 224Ra in the sediment column, we demonstrated that PEX fluxes of 224Ra were highly variable, both temporally and spatially, and can change by 1-2 orders of magnitude in our study area. Moreover, we identified a strong correlation between 224Ra-based irrigation rate and 234Th-based sediment mixing rate. Our results highlighted irrigation as the predominant PEX process for solute transfer across the sediment-water interface. Total PEX flux of 224Ra (in 1010 dpm d-1) into the Jiulong River estuary was estimated to be 22.3 ± 3.0 and 33.7 ± 5.5 during the winter and summer surveys, respectively. In comparison, total SGD flux of 224Ra (in 1010 dpm d-1) was 11.3 ± 8.6 and 49.5 ± 16.3 in the respective seasons. By multiplying the PEX fluxes of 224Ra by the ratio of the concentration gradients of component/224Ra at the sediment-water interface, we quantified the total PEX fluxes of dissolved inorganic carbon (DIC) and nutrients (NH4+, NO3-, and H4SiO4) into the Jiulong River estuary. In the meantime, net export of DIC and nutrients via SGD were estimated by multiplying the SGD fluxes of 224Ra by the DIC

  20. A TOXICITY ASSESSMENT APPROACH FOR EVALUATION OF IN-SITU BIOREMEDIATION OF PAH CONTAMINATED SEDIMENTS

    Science.gov (United States)

    Polycyclic aromatic hydrocarbons (PAHs) represent a group of organic contaminants known for their prevalence and persistence in petroleum-impacted environment such as groundwater, soils and sediments. Many high molecular weight PAHs are suspected carcinogens and the existence of...

  1. Effects of Groundwater Development on Uranium: Central Valley, California, USA

    Science.gov (United States)

    Jurgens, B.C.; Fram, M.S.; Belitz, K.; Burow, K.R.; Landon, M.K.

    2010-01-01

    Uranium (U) concentrations in groundwater in several parts of the eastern San Joaquin Valley, California, have exceeded federal and state drinking water standards during the last 20 years. The San Joaquin Valley is located within the Central Valley of California and is one of the most productive agricultural areas in the world. Increased irrigation and pumping associated with agricultural and urban development during the last 100 years have changed the chemistry and magnitude of groundwater recharge, and increased the rate of downward groundwater movement. Strong correlations between U and bicarbonate suggest that U is leached from shallow sediments by high bicarbonate water, consistent with findings of previous work in Modesto, California. Summer irrigation of crops in agricultural areas and, to lesser extent, of landscape plants and grasses in urban areas, has increased Pco2 concentrations in the soil zone and caused higher temperature and salinity of groundwater recharge. Coupled with groundwater pumping, this process, as evidenced by increasing bicarbonate concentrations in groundwater over the last 100 years, has caused shallow, young groundwater with high U concentrations to migrate to deeper parts of the groundwater system that are tapped by public-supply wells. Continued downward migration of U-affected groundwater and expansion of urban centers into agricultural areas will likely be associated with increased U concentrations in public-supply wells. The results from this study illustrate the potential long-term effects of groundwater development and irrigation-supported agriculture on water quality in arid and semiarid regions around the world. Journal compilation ?? 2009 National Ground Water Association. No claim to original US government works.

  2. Groundwater flow and mixing in a wetland–stream system

    DEFF Research Database (Denmark)

    Karan, Sachin; Engesgaard, Peter Knudegaard; Zibar, Majken Caroline Looms;

    2013-01-01

    We combined electrical resistivity tomography (ERT) on land and in a stream with zone-based hydraulic conductivities (from multi-level slug testing) to investigate the local geological heterogeneity of the deposits in a wetland–stream system. The detailed geology was incorporated into a numerical....... The presented approach of integrating such methods in groundwater–surface water exchange studies, proved efficient to obtain information of the controlling factors....... steady-state groundwater model that was calibrated against average head observations. The model results were tested against groundwater fluxes determined from streambed temperature measurements. Discharge varied up to one order of magnitude across the stream and the model was successful in capturing...... this variability. Water quality analyses from multi-level sampling underneath the streambed and in the wetland showed a stratification in groundwater composition with an aerobic shallow zone with oxygen and nitrate (top ∼3 m) overlying a reduced, anoxic zone. While NO3- concentrations up to 58 mg L−1 were found...

  3. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam John; Glud, R.N.; Cardenas, M.B.

    2013-01-01

    Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insig......- and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....

  4. Hydrological control of As concentrations in Bangladesh groundwater

    Science.gov (United States)

    Stute, M.; Zheng, Y.; Schlosser, P.; Horneman, A.; Dhar, R. K.; Datta, S.; Hoque, M. A.; Seddique, A. A.; Shamsudduha, M.; Ahmed, K. M.; van Geen, A.

    2007-09-01

    The elevated arsenic (As) content of groundwater from wells across Bangladesh and several other South Asian countries is estimated to slowly poison at least 100 million people. The heterogeneous distribution of dissolved arsenic in the subsurface complicates understanding of its release from the sediment matrix into the groundwater, as well as the design of mitigation strategies. Using the tritium-helium (3H/3He) groundwater dating technique, we show that there is a linear correlation between groundwater age at depths <20 m and dissolved As concentration, with an average slope of 19 μg L-1 yr-1 (monitoring wells only). We propose that either the kinetics of As mobilization or the removal of As by groundwater flushing is the mechanism underlying this relationship. In either case, the spatial variability of As concentrations in the top 20 m of the shallow aquifers can to a large extent be attributed to groundwater age controlled by the hydrogeological heterogeneity in the local groundwater flow system.

  5. Hydroxyl radicals form in natural sediments - effects on sedimentary organic matter

    Science.gov (United States)

    Skoog, Annelie; Alejandro Arias-Esquivel, Victor

    2010-05-01

    We show that hydroxyl radicals form at the oxic anoxic interface in marine sediments from ferrous iron reacting with hydrogen peroxide in the Fenton reaction. The aggressive nature of hydroxyl radicals makes it likely that they participate in degradation of sedimentary organic matter (SOM). We used terephthalic acid (TPA) to trap the hydroxyl radicals in sediment cores - TPA reacts with hydroxyl radicals to form the highly fluorescent product TPAOH. Results indicated formation of TPAOH at high concentrations at the oxic-anoxic interface. We also subjected SOM to hydroxyl radicals formed by the Fenton reaction, which resulted in changes in fluorescence properties and chemical composition. This is the first study showing formation of hydroxyl radicals and their effect on SOM, which is a previously unknown mechanism in the global carbon cycle.

  6. Trends in groundwater quality in relation to groundwater age

    NARCIS (Netherlands)

    Visser, A.

    2009-01-01

    Groundwater is a valuable natural resource and as such should be protected from chemical pollution. Because of the long travel times of pollutants through groundwater bodies, early detection of groundwater quality deterioration is necessary to efficiently protect groundwater bodies. The aim of this

  7. Pollution and potential mobility of Cd, Ni and Pb in the sediments of a wastewater-receiving river in Hanoi, Vietnam

    DEFF Research Database (Denmark)

    Ingvertsen, Simon T.; Marcussen, Helle; Holm, Peter E.

    2013-01-01

    with the redox-sensitive fractions and could thus be mobilised following measures such as resuspension or dredging. To assess the potential mobilisation of heavy metals from the anoxic sediment due to oxidation, the samples were exposed to different oxidants (i.e. atmospheric air and hydrogen peroxide...

  8. Variation of Sediment Properties among the Radial Profiles of Fiddler Crab Burrows in Mangrove Ecosystem

    Directory of Open Access Journals (Sweden)

    Mohammad Mokhtari

    2016-01-01

    Full Text Available Fiddler crabs burrow creates oxic-anoxic interfaces on the burrow walls. Accordingly burrow walls represent the transitions site between oxic and anoxic condition where the sediment properties varied significantly across it. In this study the burrows of three species of fiddler crabs including Uca rosea, Uca forcipata and Uca pardussumieri were sampled at three depth layers. Sediment properties of burrow walls including; temperature, redox potential, pH, density, porosity, water content, organic content, chlorophyll content and solid phase iron pools were measured to determine the magnitude of burrow effects on mangrove sediments. The results indicated that U. paradussumieri effectively reduced the sediment porosity of surrounding sediments down to 45%. Oxidized layer was more extended around U. paradussumieri burrows. Burrow walls of U. forcipata and U. paradussumieri contain higher water content than ambient sediment and burrows of U. rosea efficiently decreased the organic content of sediment. The PCA biplots indicated that the burrow walls of the all three species of fiddler crabs at 3 and 8 cm depth were correlated with oxidized iron. Ambient sediments of U. forcipata habitat were correlated with reduced iron and organic content. At 20 cm depth, burrow walls of U. paradussumieri were highly correlated with water content, while ambient sediment was correlated with reduced iron. The results of this study revealed that the thickness of oxidized layer varied according to sediment depth and burrow volume. Consequently the burrow effect varied significantly among different species of fiddler crabs as results of different habitat characteristics, sediment types and crab size.

  9. Groundwater Quality in Mura Valley (Slovenia)

    Science.gov (United States)

    Zajc Benda, T.; Souvent, P.; Bračič Železnik, B.; Čenčur Curk, B.

    2012-04-01

    Groundwater quality is one of the most important parameters in drinking water supply management. For safe drinking water supply, the quality of groundwater in the water wells on the recharge area has to be controlled. Groundwater quality data will be presented for one test area in the SEE project CC-WaterS (Climate Change and Impacts on Water Supply) Mura valley, which lies in the northeastern part of Slovenia. The Mura valley is a part of the Pannonian basin tectonic unit, which is filled with Tertiary and Quaternary gravel and sand sediments. The porous aquifer is 17 m thick in average and recharges from precipitation (70 %) and from surface waters (30 %). The aquifer is the main source of drinking water in the area for almost 53.000 inhabitants. Most of the aquifer lies beneath the agricultural area what represents the risk of groundwater quality. The major groundwater pollutants in the Mura valley are nitrates, atrazine, desethyl-atrazine, trichloroethane and tetrachloroethene. National groundwater quality monitoring is carried out twice a year, so some polluting events could be missed. The nitrate concentrations in the past were up to 140 mg/l. Concentration trends are decreasing and are now below 60 mg/l. Concentrations of atrazine and desethyl-atrazine, are decreasing as well and are below 0,1 µg/l. Trichloroethene and tetrachloroethene were detected downstream of main city in Mura valley, in the maximum concentrations of 280 μg/l in June 2005 (trichloroethene) and 880 μg/l in October 1997 (tetrachloroethene). So, it can be summarized that the trends for most pollutants in the Mura valley are decreasing, what is a good prediction for the future. Input estimation of the total nitrogen (N) (mineral and organic fertilizers) in the Mura valley shows, that the risk of leaching is enlarged in the areas, where the N input is larger than 250 kg/ha, this is at 6,3 % of all agricultural areas. Prediction for the period 2021-2050 indicates that the leaching of N

  10. Airborne and ground-based transient electromagnetic mapping of groundwater salinity in the Machile–Zambezi Basin, southwestern Zambia

    DEFF Research Database (Denmark)

    Chongo, Mkhuzo; Vest Christiansen, Anders; Tembo, Alice;

    2015-01-01

    is an efficient tool for mapping groundwater quality variations and has been used extensively to explore the Kalahari sediments, e.g., in Botswana and Namibia. Recently, airborne and groundbased mapping of groundwater salinity was conducted in the Machile–Zambezi Basin, southwestern Zambia, using the versatile...

  11. Impact of sulfide-oxidizing bacteria on the phosphorus cycle in marine sediments

    OpenAIRE

    Brock, Jörg

    2011-01-01

    Studies with the marine Beggiatoa strain 35Flor revealed that intracellular polyphosphate is rapidly degraded and phosphate is released in response to a switch from oxic to anoxic conditions at high sulfide concentrations. This new mode of polyphosphate usage drastically increases phosphate concentrations in the surrounding medium and helps to explain high phosphate concentrations in organic rich sediments of coastal upwelling areas, which enhance the chance of apatite precipitation. The unus...

  12. Nitrogen cycling within an alluvial aquifer during groundwater fluctuations

    Science.gov (United States)

    Bouskill, N.; Conrad, M. E.; Bill, M.; Brodie, E.; Forbes, M. S.; Casciotti, K. L.; Williams, K. H.

    2015-12-01

    Subsurface terrestrial-aquatic interfaces are hotspots of biogeochemical cycling of terrestrially derived organic matter and nutrients. However, pathways of nitrogen (N) loss within subsurface aquifers are poorly understood. Here we take an experimental and mechanistic modeling approach to gauge the contribution of different microbial functional groups to the transformation and loss of N in an unconfined aquifer at Rifle, Colorado. During 2014 we measured nitrate (NO3), ammonia, gaseous nitrous oxide (N2O) and the corresponding isotopic composition of NO3 and N2O. Coincident with an annual Spring/ Summer excursion in groundwater elevation, we observed a rapid decline in NO3 concentrations at three discrete depths (2, 2.5 and 3 m) within the aquifer. Isotopic measurements (i.e., δ18O and δ15N) of NO3 suggest an immediate onset of biological N loss at 2 m, but not at 3 m where the isotopic composition demonstrated dilution of NO3 concentration prior to the onset of biological N loss. This implies that the groundwater becomes increasingly anoxic as it rises within the capillary fringe. We observed the highest rates of N2O production concomitant with the largest enrichment of the δ18ONO3 and δ15NNO3 isotopes. A mechanistic microbial model representing the diverse physiology of nitrifiers, aerobic and anaerobic (denitrifying) heterotrophs and anammox bacteria indicates that the bulk of N2O production and N loss is attributable to denitrifying heterotrophs. However, this relationship is dependent on the coupling between aerobic and anaerobic microbial guilds at the oxic-anoxic interface. Modeling results suggest anammox plays a more prominent role in N loss under conditions where the organic matter input is low and rapidly drawn down by aerobic heterotrophs prior to the rise of the water table. We discuss our modeling results in light of recent molecular microbiology work at this site, but also with respect to implications for N loss across terrestrial

  13. Methanotrophy controls groundwater methane export from a barrier island

    Science.gov (United States)

    Schutte, Charles A.; Wilson, Alicia M.; Evans, Tyler; Moore, Willard S.; Joye, Samantha B.

    2016-04-01

    Methane concentrations can be high in coastal groundwater, resulting in methane export driven by submarine groundwater discharge. However, the magnitude of this methane flux depends significantly on the rate of methanotrophy, the often overlooked process of microbial methane consumption that occurs within coastal aquifer sediments. Here we describe a zone of methanogenesis within the freshwater lens of a barrier island aquifer and investigate the methane source/sink behavior of the barrier island system as a whole. The median concentration of methane dissolved in fresh groundwater beneath the center of the island was 0.6 mM, supported by high rates of potential methanogenesis (22 mmol m-2 day-1). However, rates of microbial methane consumption were also elevated in surrounding sediments (18 mmol m-2 day-1). Groundwater flowing from the zone of methanogenesis to the point of discharge into the ocean had a long residence time within methanotrophic sediments (∼195 days) such that the majority of the methane produced within the barrier island aquifer was likely consumed there.

  14. Global depletion of groundwater resources

    NARCIS (Netherlands)

    Wada, Y.; Beek, L.P.H. van; van Kempen, C.M.; Reckman, J.W.T.M.; Vasak, S.; Bierkens, M.F.P.

    2010-01-01

    In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provid

  15. Distributions of C22 C30 even-carbon-number n-alkanes in Ocean Anoxic Event 1 samples from the Basque-Cantabrian Basin

    Science.gov (United States)

    Chaler, R.; Dorronsoro, C.; Grimalt, J. O.; Agirrezabala, L. M.; Fernández-Mendiola, P. A.; García-Mondejar, J.; Gómez-Pérez, I.; López-Horgue, M.

    2005-05-01

    The Ocean Anoxic Event 1 (OAE-1) in central sites of the Basque-Cantabrian Basin exhibits very reducing depositional conditions of sedimentation. These sedimentation events have left a distinct mixture of hydrocarbons that are represented by C22 C30 n-alkanes with a predominance of the even-carbon-number homologues, high relative proportions of squalane and C16 C24 n-alkylcyclopentanes predominated by n-undecyl-, n-tridecyl- and n-pentadecylcyclopentane. Other minor compounds encompass a series of C18 C21 n-alkylcyclohexanes and C18 C24 dimethyl n-alkylcyclohexanes maximized by the even-carbon-number homologues as well as iso- and anteiso-alkanes. This unusual distribution of n-alkanes in this environment provides a new case for comparison with previously reported hypersaline and phosphorite sedimentary deposits where the occurrence of similar n-alkane distributions was reported. In the present case, these major n-alkanes and squalane are indicative of transformation under strong reducing conditions. In contrast, the occurrence of the alkylcyclopentanes, irrespective of the presence of even-carbon-number n-alkanes or squalane, suggests that reductive cyclization of fatty acids is less dependent on strong reducing conditions.

  16. Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

    Science.gov (United States)

    Bąk, Krzysztof; Bąk, Marta; Górny, Zbigniew; Wolska, Anna

    2015-01-01

    Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

  17. Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

    Directory of Open Access Journals (Sweden)

    Bąk Krzysztof

    2015-01-01

    Full Text Available Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

  18. Groundwater data network interoperability

    Science.gov (United States)

    Brodaric, Boyan; Booth, Nathaniel; Boisvert, Eric; Lucido, Jessica M.

    2016-01-01

    Water data networks are increasingly being integrated to answer complex scientific questions that often span large geographical areas and cross political borders. Data heterogeneity is a major obstacle that impedes interoperability within and between such networks. It is resolved here for groundwater data at five levels of interoperability, within a Spatial Data Infrastructure architecture. The result is a pair of distinct national groundwater data networks for the United States and Canada, and a combined data network in which they are interoperable. This combined data network enables, for the first time, transparent public access to harmonized groundwater data from both sides of the shared international border.

  19. Groundwater contamination in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Tase, Norio [Univ. of Tsukuba, Ibaraki (Japan)

    1992-07-01

    Problems on groundwater contamination in Japan are briefly summarized in this paper. Although normal physical conditions in Japan restrict the possibilities of groundwater contamination, human activities are threatening groundwater resources. A survey by the Environment Agency of Japan showed nationwide spreading of organic substances, such as trichloroethylene as well as nitrogen compounds. Synthetic detergents have also been detected even in rural areas and in deep confined aquifers, although their concentrations are not as high. Public awareness of agrichemical or pesticides abuse, especially from golf courses, is apparent. Other problems such as nitrate-nitrogen, leachate from landfills, and the leaking of underground storage tanks are also discussed. 9 refs., 3 figs., 4 tabs.

  20. Groundwater contamination in Japan

    Science.gov (United States)

    Tase, Norio

    1992-07-01

    Problems on groundwater contamination in Japan are briefly summarized in this paper. Although normal physical conditions in Japan restrict the possibilities of groundwater contamination, human activities are threatening groundwater resources. A survey by the Environment Agency of Japan showed nationwide spreading of organic substances, such as trichloroethylene as well as nitrogen compounds. Synthetic detergents have also been detected even in rural areas and in deep confined aquifers, although their concentrations are not as high. Public awareness of agrichemical or pesticides abuse, especially from golf courses, is apparent. Other problems such as nitrate-nitrogen, leachate from landfills, and the leaking of underground storage tanks are also discussed.

  1. Algae after dark: mechanisms to cope with anoxic/hypoxic conditions.

    Science.gov (United States)

    Yang, Wenqiang; Catalanotti, Claudia; Wittkopp, Tyler M; Posewitz, Matthew C; Grossman, Arthur R

    2015-05-01

    Chlamydomonas reinhardtii is a unicellular, soil-dwelling (and aquatic) green alga that has significant metabolic flexibility for balancing redox equivalents and generating ATP when it experiences hypoxic/anoxic conditions. The diversity of pathways available to ferment sugars is often revealed in mutants in which the activities of specific branches of fermentative metabolism have been eliminated; compensatory pathways that have little activity in parental strains under standard laboratory fermentative conditions are often activated. The ways in which these pathways are regulated and integrated have not been extensively explored. In this review, we primarily discuss the intricacies of dark anoxic metabolism in Chlamydomonas, but also discuss aspects of dark oxic metabolism, the utilization of acetate, and the relatively uncharacterized but critical interactions that link chloroplastic and mitochondrial metabolic networks.

  2. Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction.

    Science.gov (United States)

    Shen, Yanan; Farquhar, James; Zhang, Hua; Masterson, Andrew; Zhang, Tonggang; Wing, Boswell A

    2011-02-22

    Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes ((32)S, (33)S, (34)S and (36)S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ(34)S with negative Δ(33)S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction.

  3. Pyrite surface interaction with selected organic aqueous species under anoxic conditions

    Directory of Open Access Journals (Sweden)

    Bebié Joakim

    2000-10-01

    Full Text Available The interaction between low-molecular weight organic compounds and pyrite under anoxic conditions has been studied using a combination of electrophoresis and batch sorption experiments. The results suggest that acetate, carbamide, ethylamine, formamide, purine, D-ribose, and adenine, as well as the amino acids alanine, cysteine and glycine, interact within the electrophoretic shearplane of the pyrite surface. The observed surface interaction between the negatively charged surface of pyrite and the organic aqueous species takes place regardless of the formal charge of the aqueous species of interest. This indicates that the interaction of organic molecules with pyrite surfaces under anoxic conditions is dictated by interactions with specific surface sites (thiol or iron surface sites rather than electrostatic forces. Dissolved metals typically enhance the interaction of the organics species. This enhancement is either due to an alteration in the distribution of thiol and iron groups on the pyrite surface or by the formation of ternary surface complexes.

  4. Systematics of past changes in ocean ventilation: a comparison of Cretaceous Ocean Anoxic Event 2 and Pleistocene to Holocene Oxygen Minimum Zones

    Directory of Open Access Journals (Sweden)

    J. Schönfeld

    2014-09-01

    Full Text Available Present day oceans are generally well ventilated except mid-depth oxygen minimum zones (OMZs under high surface water productivity regimes, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or even anoxic. In particular the Cretaceous Ocean Anoxic Events (OAEs were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossil assemblages preserved in the sedimentary record. Yet both, qualitative and quantitative assessments of intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life are well known. Their implications for constraining past bottom-water oxygenation are addressed in this review, with emphasis on comparing OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the Atlantic NW African shelf. Holocene laminated sediments were encountered at bottom-water oxygen levels of −1 under the Peruvian upwelling and −1 in California Borderland basins and the Pakistan Margin. Changes of sediment input on seasonal to decadal time scales are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae in sediment cores. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. This ichnogenus has not been reported from Peruvian sediments but cm-sized crab burrows appeared around 10 μmol kg−1, which may indicate a

  5. Iron isotope and trace metal records of iron cycling in the proto-North Atlantic during the Cenomanian-Turonian oceanic anoxic event (OAE-2)

    Science.gov (United States)

    Owens, Jeremy D.; Lyons, Timothy W.; Li, Xiaona; MacLeod, Kenneth G.; Gordon, Gwenyth; Kuypers, Marcel M. M.; Anbar, Ariel; Kuhnt, Wolfgang; Severmann, Silke

    2012-09-01

    The global carbon cycle during the mid-Cretaceous (˜125-88 million years ago, Ma) experienced numerous major perturbations linked to increased organic carbon burial under widespread, possibly basin-scale oxygen deficiency and episodes of euxinia (anoxic and H2S-containing). The largest of these episodes, the Cenomanian-Turonian boundary event (ca. 93.5 Ma), or oceanic anoxic event (OAE) 2, was marked by pervasive deposition of organic-rich, laminated black shales in deep waters and in some cases across continental shelves. This deposition is recorded in a pronounced positive carbon isotope excursion seen ubiquitously in carbonates and organic matter. Enrichments of redox-sensitive, often bioessential trace metals, including Fe and Mo, indicate major shifts in their biogeochemical cycles under reducing conditions that may be linked to changes in primary production. Iron enrichments and bulk Fe isotope compositions track the sources and sinks of Fe in the proto-North Atlantic at seven localities marked by diverse depositional conditions. Included are an ancestral mid-ocean ridge and euxinic, intermittently euxinic, and oxic settings across varying paleodepths throughout the basin. These data yield evidence for a reactive Fe shuttle that likely delivered Fe from the shallow shelf to the deep ocean basin, as well as (1) hydrothermal sources enhanced by accelerated seafloor spreading or emplacement of large igneous province(s) and (2) local-scale Fe remobilization within the sediment column. This study, the first to explore Fe cycling and enrichment patterns on an ocean scale using iron isotope data, demonstrates the complex processes operating on this scale that can mask simple source-sink relationships. The data imply that the proto-North Atlantic received elevated Fe inputs from several sources (e.g., hydrothermal, shuttle and detrital inputs) and that the redox state of the basin was not exclusively euxinic, suggesting previously unknown heterogeneity in

  6. Absence of major vegetation and palaeoatmospheric pCO 2 changes associated with oceanic anoxic event 1a (Early Aptian, SE France)

    Science.gov (United States)

    Heimhofer, Ulrich; Hochuli, Peter A.; Herrle, Jens O.; Andersen, Nils; Weissert, Helmut

    2004-07-01

    The deposition of organic-rich sediments during the late Early Aptian Oceanic Anoxic Event (OAE) 1a has been interpreted to result in a major decrease of palaeoatmospheric CO 2 concentrations, accompanied by significant changes in the terrestrial flora. In order to test this hypothesis, the OAE 1a interval in the Vocontian Basin (SE France) has been studied with a combined approach including stable carbon isotopes, organic geochemistry and palynology. To estimate changes in palaeoatmospheric CO 2 levels across the OAE 1a, the δ13C composition of presumed algal biomarkers (low molecular weight n-alkanes, steranes) and of bulk carbonate carbon are used. Our results yield estimated Early Aptian carbon dioxide partial pressure ( pCO 2) values three to four times the preindustrial level and only a moderate drop across the black shale event. This moderate drop in pCO 2 is supported by palynological results. The frequency patterns of climate-sensitive sporomorphs (incl. pteridophyte spores, bisaccate pollen and Classopollis spp.) display only minor fluctuations throughout the studied section and indicate relatively stable patterns of terrestrial vegetation during and after formation of the OAE 1a black shale. The occurrence of a characteristic Early Aptian carbon isotope pattern across the OAE 1a interval permits accurate chemostratigraphic correlation with the well-studied Livello Selli interval of the Cismon record (N Italy). The contemporaneous formation of individual black shale layers at both sites indicates that transient episodes of dysoxic-anoxic bottom waters prevailed over large areas in the W Tethys Ocean independent of depositional setting. Comparison of the palynological data from the two locations displays significant differences in the frequency patterns of bisaccate pollen. The contrasting pollen spectra are interpreted to reflect prominent changes in the palaeoceanographic current patterns and/or selective sorting due to sea-level rise rather than

  7. Chromium isotopes in siliciclastic sediments and sedimentary rocks as a proxy for Earth surface redox

    Science.gov (United States)

    Reinhard, C. T.; Planavsky, N. J.; Wang, X.; Owens, J. D.; Johnson, T. M.; Fischer, W. W.; Lyons, T. W.

    2013-12-01

    Chromium (Cr) isotopes are an emerging and potentially promising proxy for tracking redox processes at Earth's surface. However, recent efforts to reconstruct the Cr isotope record through time have primarily focused on sporadically deposited iron-rich chemical sediments, with large temporal gaps and limited capacity to explore the Cr isotope record relative to modern and recent marine processes. However, the basic inorganic chemistry of Cr suggests that anoxic marine basins factor prominently in the global Cr cycle, and that likewise sediments deposited within anoxic basins may offer an unexplored Cr isotope archive throughout Earth's history. We present authigenic δ53Cr data from sediments of the Cariaco Basin, Venezuela--a ';type' environment on the modern Earth for large, perennially anoxic basins with relatively strong hydrological connections to the global ocean. Combined with currently available constraints on the δ53Cr composition of modern Atlantic seawater, these data are consistent with the hypothesis that anoxic marine basins can serve as a chemical archive of the first-order features of seawater δ53Cr variation. We employ a simple quantitative model to explore the implications of this hypothesis for global Cr isotope mass balance and the possible utility of authigenic δ53Cr in anoxically deposited siliciclastic sediments and sedimentary rocks as a global paleoredox proxy. Our focus is a basic analysis of the primary controls on seawater δ53Cr as related to both the marine redox landscape and the processes involved in the weathering and aqueous-particulate transport of Cr at Earth's surface. As a case study, we provide analysis of new bulk δ53Cr data through a Cretaceous Oceanic Anoxic Event (OAE-2), which shows a well-defined ~1.0‰ negative excursion during the event coupled with evidence for a drawdown of the marine Cr reservoir. We present a conceptual model to explain these observations, and interpret this shift to suggest a shutdown of

  8. Open questions on the origin of life at anoxic geothermal fields.

    Science.gov (United States)

    Mulkidjanian, Armen Y; Bychkov, Andrew Yu; Dibrova, Daria V; Galperin, Michael Y; Koonin, Eugene V

    2012-10-01

    We have recently reconstructed the 'hatcheries' of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells (Mulkidjanian et al. Proc Natl Acad Sci U S A 109:E821-830, 2012). These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K⁺, Zn²⁺, Mn²⁺, and phosphate. Thus, protocells must have evolved in habitats with a high K⁺/Na⁺ ratio and relatively high concentrations of Zn, Mn and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under an anoxic, CO₂-dominated atmosphere, the ionic composition of pools of cool, condensed vapor at anoxic geothermal fields would resemble the internal milieu of modern cells. Such pools would be lined with porous silicate minerals mixed with metal sulfides and enriched in K⁺ ions and phosphorous compounds. Here we address some questions that have appeared in print after the publication of our anoxic geothermal field scenario. We argue that anoxic geothermal fields, which were identified as likely cradles of life by using a top-down approach and phylogenomics analysis, could provide geochemical conditions similar to those which were suggested as most conducive for the emergence of life by the chemists who pursuit the complementary bottom-up strategy.

  9. Controlled oxygen release from pyridone endoperoxides promotes cell survival under anoxic conditions

    OpenAIRE

    Benz, Sebastian; Noetzli, Sarah; Siegel, Jay; Eberli, Daniel; Jessen, Henning Jacob

    2013-01-01

    In tissue engineering, survival of larger constructs remains challenging due to limited supply with oxygen caused by a lack of early vascularization. Controlled release of oxygen from small organic molecules represents a possible strategy to prevent cell death under anoxic conditions. A comprehensive study of methylated pyridone-derived endoperoxides has led to the development of water-soluble molecules that undergo retro Diels-Alder reactions in aqueous environment releasing oxygen in high y...

  10. Extreme Red Sea: Life in the deep-sea anoxic brine lakes

    OpenAIRE

    2013-01-01

    Tectonic splitting of the Arabian and African plates originated the Red Sea together with one of the most unique, remote, and extreme environments on Earth: deep-sea anoxic brine lakes. They combine multiple extremes namely increased salinity (7-fold), temperature (up to 70°C), concentration of heavy metals (1,000- to 10,000-fold), and hydrostatic pressure [1]. Despite such harsh conditions, they harbor an unexpectedly high biodiversity and are teeming with life. Increased i...

  11. Biogenic nitrogen gas production at the oxic–anoxic interface in the Cariaco Basin, Venezuela

    Directory of Open Access Journals (Sweden)

    E. Montes

    2013-01-01

    Full Text Available Excess nitrogen gas (N2xs was measured in samples collected at six locations in the eastern and western sub-basins of the Cariaco Basin, Venezuela, in September 2008 (non-upwelling conditions and March 2009 (upwelling conditions. During both sampling periods, N2xs concentrations were below detection in surface waters, increasing to ~ 22 μmol N kg−1 at the oxic–anoxic interface ([O2] < ~ 4 μmol kg−1, ~ 250 m. Below the oxic–anoxic interface (300–400 m, the average concentration of N2xs was 24.7 ± 1.9 μmol N kg−1 in September 2008 and 27.5 ± 2.0 μmol N kg−1 in March 2009, i.e., N2xs concentrations within this depth interval were ~ 3 μmol N kg−1 higher (p < 0.001 during the upwelling season compared to the non-upwelling period. These results suggest that N-loss in the Cariaco Basin may vary seasonally in response to changes in the flux of sinking particulate organic matter. We attribute the increase in N2xs concentrations, or N-loss, observed during upwelling to: (1 higher availability of fixed nitrogen derived from suspended and sinking particles at the oxic–anoxic interface and/or (2 enhanced ventilation at the oxic–anoxic interface during upwelling.

  12. The removal of cyanobacteria and their metabolites through anoxic biodegradation in drinking water sludge.

    Science.gov (United States)

    Ma, Guangxiang; Pei, Haiyan; Hu, Wenrong; Xu, Xiangchao; Ma, Chunxia; Li, Xiuqing

    2014-08-01

    The effects of environmental factors on cyanobacteria damage and microcystin-LR degradation in drinking water sludge were investigated under anoxic conditions. The rates of microcystin-LR release and degradation increased rapidly with the increasing temperature from 15°C to 40°C and the highest degradation rate of 99% was observed at 35°C within 10days. Compared to acidic conditions, microcystin-LR degraded more rapidly in weak alkali environments. In addition, the microbial community structures under different anoxic conditions were studied. The sequencing results showed that four phyla obtained from the DGGE profiles were as follows: Proteobacteria, Acidobacteria, Firmicutes and Cyanobacteria. Proteobacteria containing nine genera were the most common species. Pseudomonas, Methylosinus and Sphingomona all showed stronger activities and had significant increase as microcystin-LR degraded, so they should be responsible for the microcystin-LR degradation. This is the first report of Pseudomonas, Methylosinus and Sphingomonas as the microcystins-degrading microorganisms in anoxic drinking water sludge.

  13. A laboratory-incubated redox oscillation experiment to investigate Hg fluxes from highly contaminated coastal marine sediments (Gulf of Trieste, Northern Adriatic Sea).

    Science.gov (United States)

    Emili, A; Carrasco, L; Acquavita, A; Covelli, S

    2014-03-01

    Mercury (Hg) mobility at the sediment-water interface was investigated during a laboratory incubation experiment conducted with highly contaminated sediments (13 μg g(-1)) of the Gulf of Trieste. Undisturbed sediment was collected in front of the Isonzo River mouth, which inflows Hg-rich suspended material originating from the Idrija (NW Slovenia) mining district. Since hypoxic and anoxic conditions at the bottom are frequently observed and can influence the Hg biogeochemical behavior, a redox oscillation was simulated in the laboratory, at in situ temperature, using a dark flux chamber. Temporal variations of several parameters were monitored simultaneously: dissolved Hg (DHg) and methylmercury (MeHg), O2, NH4 (+), NO3 (-) + NO2 (-), PO4 (3-), H2S, dissolved Mn(2+), dissolved inorganic and organic carbon (DIC and DOC). Under anoxic conditions, both Hg (665 ng m(2) day(-1)) and MeHg (550 ng m(2) day(-1)) fluxed from sediments into the water column, whereas re-oxygenation caused concentrations of MeHg and Hg to rapidly drop, probably due to re-adsorption onto Fe/Mn-oxyhydroxides and enhanced demethylation processes. Hence, during anoxic events, sediments of the Gulf of Trieste may be considered as an important source of DHg species for the water column. On the contrary, re-oxygenation of the bottom compartment mitigates Hg and MeHg release from the sediment, thus acting as a natural "defence" from possible interaction between the metal and the aquatic organisms.

  14. Groundwater Capture Zones

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — Source water protection areas are delineated for each groundwater-based public water supply system using available geologic and hydrogeologic information to...

  15. Using radon to understand parafluvial flows and the changing locations of groundwater inflows in the Avon River, southeast Australia

    Science.gov (United States)

    Cartwright, Ian; Hofmann, Harald

    2016-09-01

    Understanding the location and magnitude of groundwater inflows to rivers is important for the protection of riverine ecosystems and the management of connected groundwater and surface water systems. This study utilizes 222Rn activities and Cl concentrations in the Avon River, southeast Australia, to determine the distribution of groundwater inflows and to understand the importance of parafluvial flow on the 222Rn budget. The distribution of 222Rn activities and Cl concentrations implies that the Avon River contains alternating gaining and losing reaches. The location of groundwater inflows changed as a result of major floods in 2011-2013 that caused significant movement of the floodplain sediments. The floodplain of the Avon River comprises unconsolidated coarse-grained sediments with numerous point bars and sediment banks through which significant parafluvial flow is likely. The 222Rn activities in the Avon River, which are locally up to 3690 Bq m-3, result from a combination of groundwater inflows and the input of water from the parafluvial zone that has high 222Rn activities due to 222Rn emanation from the alluvial sediments. If the high 222Rn activities were ascribed solely to groundwater inflows, the calculated net groundwater inflows would exceed the measured increase in streamflow along the river by up to 490 % at low streamflows. Uncertainties in the 222Rn activities of groundwater, the gas transfer coefficient, and the degree of hyporheic exchange cannot explain a discrepancy of this magnitude. The proposed model of parafluvial flow envisages that water enters the alluvial sediments in reaches where the river is losing and subsequently re-enters the river in the gaining reaches with flow paths of tens to hundreds of metres. Parafluvial flow is likely to be important in rivers with coarse-grained alluvial sediments on their floodplains and failure to quantify the input of 222Rn from parafluvial flow will result in overestimating groundwater inflows to

  16. High-fluoride groundwater.

    Science.gov (United States)

    Rao, N Subba

    2011-05-01

    Fluoride (F(-)) is essential for normal bone growth, but its higher concentration in the drinking water poses great health problems and fluorosis is common in many parts of India. The present paper deals with the aim of establishment of facts of the chemical characteristics responsible for the higher concentration of F(-) in the groundwater, after understanding the chemical behavior of F(-) in relation to pH, total alkalinity (TA), total hardness (TH), carbonate hardness (CH), non-carbonate hardness (NCH), and excess alkalinity (EA) in the groundwater observed from the known areas of endemic fluorosis zones of Andhra Pradesh that have abundant sources of F(-)-bearing minerals of the Precambrians. The chemical data of the groundwater shows that the pH increases with increase F(-); the concentration of TH is more than the concentration of TA at low F(-) groundwater, the resulting water is represented by NCH; the TH has less concentration compared to TA at high F(-) groundwater, causing the water that is characterized by EA; and the water of both low and high concentrations of F(-) has CH. As a result, the F(-) has a positive relation with pH and TA, and a negative relation with TH. The operating mechanism derived from these observations is that the F(-) is released from the source into the groundwater by geochemical reactions and that the groundwater in its flowpath is subjected to evapotranspiration due to the influence of dry climate, which accelerates a precipitation of CaCO(3) and a reduction of TH, and thereby a dissolution of F(-). Furthermore, the EA in the water activates the alkalinity in the areas of alkaline soils, leading to enrichment of F(-). Therefore, the alkaline condition, with high pH and EA, and low TH, is a more conducive environment for the higher concentration of F(-) in the groundwater.

  17. Evaluation of deep groundwater development for arsenic mitigation in western Bangladesh.

    Science.gov (United States)

    Shibasaki, Naoaki; Lei, Peifeng; Kamata, Akira

    2007-10-01

    Groundwater contamination by arsenic frequently occurs in western Bangladesh. Integrated hydrogeological studies were carried out by the Japan International Cooperation Agency (JICA) in the Jessore, Jhenaidah and Chuadanga districts to assess the possibility of supplying safe drinking water from deep aquifers. The subsurface geology of up to 300 m in depth was classified into 5 formations (viz. A to E formations in descending order). Thick clay facies are found in C formation in the Jessore district, however, clay facies are absent in the Jhenaidah and Chuadanga districts. The clay layer separates deep aquifers from shallow aquifers, and controls vertical groundwater flow. The results of core sample analysis showed that high arsenic contents of more than 30 ppm were found not only from shallow clay but also even from deep clay below 200 m. However, the arsenic concentrations in groundwater were generally below 0.05 mg/L in the deep aquifers. The simulation study using a vertical 2-D groundwater model indicates that deep groundwater will not be contaminated by arsenic in shallow groundwater when the piezometric heads of the deep aquifers are higher than the shallow aquifers. However, the simulation results indicate that overexploitation of the deep aquifers will cause arsenic contamination in deep aquifers due to the downward movement of contaminated shallow groundwater when no sorption takes place in the sediments. These results suggest that groundwater management and control of groundwater pumpage in deep aquifers are crucial for sustainable supply of arsenic safe deep groundwater in western Bangladesh.

  18. Groundwater Monitoring of Land Application with Manure, Biosolids, and other Organic Residuals

    Science.gov (United States)

    Harter, T.; Lawrence, C.; Atwill, E. R.; Kendall, C.

    2007-12-01

    Regulatory programs frequently require monitoring of first encountered (shallow-most) groundwater for purposes of determining whether an actual or potential, permitted or incidental waste discharge has had or will have a degrading effect on groundwater quality. Traditionally, these programs have focused on monitoring of incidental discharges from industrial sites. Increasingly, sources with an implied groundwater recharge are subject to monitoring requirements. These recharging sources include, for example, land application of municipal, food processing, or animal waste to irrigated cropland. Groundwater monitoring of a recharging source requires a different approach to groundwater monitoring than traditional (incidental source) monitoring programs. Furthermore, the shallow groundwater aquifer targeted for compliance monitoring commonly consists of highly heterogeneous unconsolidated alluvial, fluvial, lacustrine, glacial, or subaeolian sediments of late tertiary or quaternary age. Particularly in arid and semi-arid climates, groundwater is also frequently subject to significant seasonal and interannual groundwater level fluctuations that may exceed ten feet seasonally and several tens of feet within a three- to five-year period. We present a hydrodynamically rigorous approach to designing groundwater monitoring wells for recharging sources under conditions of aquifer heterogeneity and water level fluctuations and present the application of this concept to monitoring confined animal farming operations (CAFOs) with irrigated crops located on alluvial fans with highly fluctuating, deep groundwater table.

  19. Study on the variation of arsenic concentration in groundwater and chemical characteristics of arsenic in sediment cores at the areas with endemic arsenic poison disease in Jianghan Plain%江汉平原地方性砷中毒病区地下水砷含量变化及沉积物砷化学特征研究

    Institute of Scientific and Technical Information of China (English)

    周素华; 叶恒朋; 李明健; 熊培生; 杜冬云; 王靖文

    2015-01-01

    目的 了解江汉平原地方性砷中毒(地砷病)病区地下水砷含量变化,探讨该区域高砷水赋存环境、地下水系统砷的来源.方法 在湖北省仙桃市和洪湖市分别以地砷病患者家为中心点,在3km半径内各采集30份地下水样品和3个地质钻孔沉积物样芯;水砷含量比较采用配对t检验或配对符号秩和检验进行分析.结果 仙桃市南洪村2011-2012年水砷浓度低于2006-2007年(t=4.645 3,P<0.000 1),洪湖市姚河村2011-2012年水砷浓度高于2006-2007年(S=-150,P<0.000 1);高砷水呈弱酸、弱氧化性,水砷浓度与水样C1-、HCO3-、Fe、Mn浓度正相关,与水样SO42-、NO3-浓度负相关;研究区沉积物中砷浓度为1.500~ 17.289mg/kg,砷含量最大值均出现在泥土层,最小值均出现在沙层.结论 江汉平原地砷病病区高砷水砷含量的时空间变化程度较大,与中国山西大同盆地、山阴地区、内蒙古河套平原等原生高砷水地区有明显差异,为典型的高砷水赋存环境;研究区沉积物样品中砷含量与岩性结构有密切关系.%Objective To understand the variation of arsenic concentration in underground water at the endemic arsenic poison disease area of Jianghan Plain so as to better understand the spatial distribution of high arsenic groundwater,hydro-chemical evolution and source of arsenic in this region.Methods Thirty underground water samples were collected respectively around 3 km radius of the two houses where arsenic poisoning patients lived,in Xiantao and Honghu.Sediment cores of three drillings were collected as well.Both paired t-test or paired Wilcoxon Signed Ranking Test were used to compare the arsenic concentration of water.Results The arsenic concentration in 2011-2012 appeared lower than that in 2006-2007 at the Nanhong village of Xiantao (t=4.645 3,P<0.000 1),but was higher(S=-150,P<0.000 1) in the Yaohe village of Honghu.The pH value showed weak acidity with Eh as weak oxidated

  20. Occurrence and hydrogeochemical characteristics of high-fluoride groundwater in Xiji County, southern part of Ningxia Province, China.

    Science.gov (United States)

    Wei, Chao; Guo, Huaming; Zhang, Di; Wu, Yang; Han, Shuangbao; An, Yonghui; Zhang, Fucun

    2016-02-01

    High-F(-) groundwater is widely distributed in Xiji County, which endangers the safety of drinking water. In order to evaluate the key factors controlling the origin and geochemical mechanisms of F(-) enrichment in groundwater at Xiji County, one hundred and five groundwater samples and sixty-two sediment samples were collected. Fluoride concentration in the groundwater samples ranged from 0.2 to 3.01 mg/L (mean 1.13 mg/L), with 17 % exceeding the WHO drinking water guideline value of 1.5 mg/L and 48 % exceeding the Chinese drinking water guideline value of 1.0 mg/L. High-F(-) groundwaters were characterized by hydrochemical types of Na-HCO3 and Na-SO4·Cl, which were found in Quaternary sediment aquifer and in Tertiary clastic aquifer, respectively. Conditions favorable for F(-) enrichment in groundwater included weakly alkaline pH (7.2-8.9), low concentration of Ca(2+), and high concentrations of HCO3 (-) and Na(+). Calcite and fluorite were the main minerals controlling F(-) concentration in groundwaters. The hydrolysis of F-bearing minerals in aquifer sediments was the more important process for F(-) release in Tertiary clastic aquifer, which was facilitated by long residence time of groundwater, in comparison with Quaternary sediment aquifer. Cation exchange would also play important roles, which removed Ca(2+) and Mg(2+) and led to more free mobility of F(-) in groundwater and permitted dissolution of fluorite, especially in Tertiary clastic aquifer. However, evapotranspiration and competing adsorption of B and HCO3 (-) were the more important processes for F(-) enrichment in Quaternary groundwater. Groundwater in Lower Cretaceous aquifer had relatively low F(-) concentration, which was considered to be the potential drinking water resource.

  1. Different bacterial communities associated with the roots and bulk sediment of the seagrass Zostera marina

    DEFF Research Database (Denmark)

    Jensen, Sheila Ingemann; Kühl, Michael; Priemé, Anders

    2007-01-01

    The bacterial community of Zostera marina-inhabited bulk sediment vs. root-associated bacteria was investigated by terminal restriction fragment length polymorphism and sequencing, and the spatial extension of the oxygen loss from roots was determined by oxygen microsensors. Extensive oxygen loss...... was found in the tip region of the youngest roots, and most of the rhizoplane of Z. marina roots was thus anoxic. A significant difference between the bacterial communities associated with the roots and bulk sediment was found. No significant differences were found between differently aged root...

  2. Long distance electron transport in marine sediments: Microbial and geochemical implications

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Larsen, Steffen; Pfeffer, Christian;

    redox half-reactions in distant regions of the sediment leads to formation of electrical fields, which modifies ion transport. The local proton producing and proton consuming half reactions induces pH extremes that accelerate dissolution of iron sulphides and calcium carbonates in anoxic layers......-structural properties suggesting that they are living electric micro cables. The mode of action of these organisms has major impacts on element cycling by redox processes, pH balances, mineral dissolution/precipitations, and electro migration of ions in marine sediment. The ability of Desulfubulbus filaments to bridge...

  3. Trace metal behaviour in riverine sediments: Role of organic matter and sulfides

    Energy Technology Data Exchange (ETDEWEB)

    Charriau, Adeline; Lesven, Ludovic [Universite Lille 1 Sciences et Technologies, Laboratoire Geosystemes (FRE-CNRS 3298), 59655 Villeneuve d' Ascq (France); Gao Yue; Leermakers, Martine; Baeyens, Willy [Department of Analytical and Environmental Chemistry (ANCH), Vrije Universiteit Brussel (VUB), B-1050 Brussels (Belgium); Ouddane, Baghdad [Universite Lille 1 Sciences et Technologies, Laboratoire Geosystemes (FRE-CNRS 3298), 59655 Villeneuve d' Ascq (France); Billon, Gabriel, E-mail: gabriel.billon@univ-lille1.fr [Universite Lille 1 Sciences et Technologies, Laboratoire Geosystemes (FRE-CNRS 3298), 59655 Villeneuve d' Ascq (France)

    2011-01-15

    Graphical abstract: Experimental and modelling approach on trace metal fate in anoxic sediments. Display Omitted Research highlights: {yields} Experimental and modelling approach on trace metals fate in anoxic sediments. {yields} Organic matter and sulphides compete for the binding of trace metals. {yields} Efficient scavenging of trace metals in sulphide minerals. {yields} Dissolved organic matter increases the solubility of trace metals in pore waters. {yields} Similar lability of trace metals in pore waters and sediment particles. - Abstract: Three sediment cores were collected in the Scheldt, Lys and Spiere canals, which drain a highly populated and industrialized area in Western Europe. The speciation and the distribution of trace metals in pore waters and sediment particles were assessed through a combination of computational and experimental techniques. The concentrations of dissolved major and trace elements (anions, cations, sulfides, dissolved organic C, Cd, Co, Fe, Mn, Ni, Pb and Zn) were used to calculate the thermodynamic equilibrium speciation in pore waters and to evaluate the saturation of minerals (Visual Minteq software). A sequential extraction procedure was applied on anoxic sediment particles in order to assess the main host phases of trace elements. Manganese was the most labile metal in pore waters and was mainly associated with carbonates in particles. In contrast, a weak affinity of Cd, Co, Ni, Pb and Zn with carbonates was established because: (1) a systematic under-saturation was noticed in pore waters and (2) less than 10% of these elements were extracted in the exchangeable and carbonate sedimentary fraction. In the studied anoxic sediments, the mobility and the lability of trace metals, apart from Mn, seemed to be controlled through the competition between sulfidic and organic ligands. In particular, the necessity of taking into account organic matter in the modelling of thermodynamic equilibrium was demonstrated for Cd, Ni, Zn and Pb

  4. Nitrogen fixation in sediments along a depth transect through the Peruvian oxygen minimum zone

    OpenAIRE

    Gier, Jessica; Sommer, Stefan; Carolin R Löscher; Dale, Andrew W.; Schmitz, Ruth A.; Treude, Tina

    2016-01-01

    The potential coupling of nitrogen (N2) fixation and sulfate reduction (SR) was explored in sediments of the Peruvian oxygen minimum zone (OMZ). Sediment samples were retrieved by a multiple corer at six stations along a depth transect (70–1025 m water depth) at 12° S, covering anoxic and hypoxic bottom water conditions. Benthic N2 fixation, determined by the acetylene reduction assay, was detected at all sites, with highest rates between 70 and 253 m and lower rates at grea...

  5. Interpolations of groundwater table elevation in dissected uplands.

    Science.gov (United States)

    Chung, Jae-won; Rogers, J David

    2012-01-01

    The variable elevation of the groundwater table in the St. Louis area was estimated using multiple linear regression (MLR), ordinary kriging, and cokriging as part of a regional program seeking to assess liquefaction potential. Surface water features were used to determine the minimum water table for MLR and supplement the principal variables for ordinary kriging and cokriging. By evaluating the known depth to the water and the minimum water table elevation, the MLR analysis approximates the groundwater elevation for a contiguous hydrologic system. Ordinary kriging and cokriging estimate values in unsampled areas by calculating the spatial relationships between the unsampled and sampled locations. In this study, ordinary kriging did not incorporate topographic variations as an independent variable, while cokriging included topography as a supporting covariable. Cross validation suggests that cokriging provides a more reliable estimate at known data points with less uncertainty than the other methods. Profiles extending through the dissected uplands terrain suggest that: (1) the groundwater table generated by MLR mimics the ground surface and elicits a exaggerated interpolation of groundwater elevation; (2) the groundwater table estimated by ordinary kriging tends to ignore local topography and exhibits oversmoothing of the actual undulations in the water table; and (3) cokriging appears to give the realistic water surface, which rises and falls in proportion to the overlying topography. The authors concluded that cokriging provided the most realistic estimate of the groundwater surface, which is the key variable in assessing soil liquefaction potential in unconsolidated sediments.

  6. Hydrogeochemical Characteristics of Fluorine in Shallow Groundwater of Tongshan Area

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lai; FENG Qi-yan; LI Hou-yao

    2005-01-01

    Tongshan area,a part of the floodplain of the abandoned Huanghe River, is one of the popular endemic fluorosis areas in East China. One of the reasons is high concentration of fluorine in shallow groundwater. Test results of 36 groundwater samples show that fluorine concentration in shallow groundwater is 0.18-6.7 mg/L and 50 % of the samples exceed the Chinese drinking water quality standard. There exists a significant negative correlation in content between Ca2+ and F-. The correlations between fluorine concentration and other cations (for example Na+, K+, Mg2+) are not significant. The content of dissolved fluorine from the flooding sediments of the Huanghe River that varying from 5.6 mg/kg to 15.2 mg/kg plays an important role in forming the high fluorine groundwater. Usually, the dissolved fluorine content in silt is much higher than that in silty clay and clay. According to the geological investigation fluorine content in deep groundwater (over 60 m) is less than 1.0 mg/L and suitable for drinking, so it is an effective measure to prevent endemic fluorosis by extracting deep groundwater in disease areas.

  7. Phosphate-Induced Immobilization of Uranium in Hanford Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zezhen; Giammar, Daniel E.; Mehta, Vrajesh; Troyer, Lyndsay D.; Catalano, Jeffrey G.; Wang, Zheming

    2016-12-20

    Phosphate can be added to subsurface environments to immobilize U(VI) contamination. The efficacy of immobilization depends on the site-specific groundwater chemistry and aquifer sediment properties. Batch and column experiments were performed with sediments from the Hanford 300 Area in Washington State and artificial groundwater prepared to emulate the conditions at the site. Batch experiments revealed enhanced U(VI) sorption with increasing phosphate addition. X-ray absorption spectroscopy measurements of samples from the batch experiments found that U(VI) was predominantly adsorbed at conditions relevant to the column experiments and most field sites (low U(VI) loadings, <25 μM), and U(VI) phosphate precipitation occurred only at high initial U(VI) (>25 μM) and phosphate loadings. While batch experiments showed the transition of U(VI) uptake from adsorption to precipitation, the column study was more directly relevant to the subsurface environment because of the high solid:water ratio in the column and the advective flow of water. In column experiments, nearly six times more U(VI) was retained in sediments when phosphate-containing groundwater was introduced to U(VI)-loaded sediments than when the groundwater did not contain phosphate. This enhanced retention persisted for at least one month after cessation of phosphate addition to the influent fluid. Sequential extractions and laser-induced fluorescence spectroscopy of sediments from the columns suggested that the retained U(VI) was primarily in adsorbed forms. These results indicate that in situ remediation of groundwater by phosphate addition provides lasting benefit beyond the treatment period via enhanced U(VI) adsorption to sediments.

  8. Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

    Directory of Open Access Journals (Sweden)

    B. Deutsch

    2010-04-01

    Full Text Available Rates of denitrification in sediments were measured with the isotope pairing technique at different sites in the southern and central Baltic Sea. They varied between 0.5 μmol m−2 h−1 in sands and 28.7 μmol m−2 h−1 in muddy sediments and showed a good correlation to the organic carbon contents of the surface sediments. N-removal rates via sedimentary denitrification were estimated for the entire Baltic Sea calculating sediment specific denitrification rates and interpolating them to the whole Baltic Sea area. Another approach was carried out by using the relationship between the organic carbon content and the rate of denitrification. For the entire Baltic Sea the N-removal by denitrification in sediments varied between 426–652 kt N a−1, which is around 48–73% of the external N inputs delivered via rivers, coastal point sources and atmospheric deposition. Moreover, an expansion of the anoxic bottom areas was considered under the assumption of a rising oxycline from 100 to 80 m water depth. This leads to an increase of the area with anoxic conditions and an overall decrease in sedimentary denitrification by 14%. Overall we can show here that this type of data extrapolation is a powerful tool to estimate the nitrogen losses for a whole coastal sea and may be applicable to other coastal regions and enclosed seas, too.

  9. Potassium ferrate treatment of RFETS` contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-01-01

    The potassium ferrate treatment study of Rocky Flats Environmental Technology Site (RFETS) groundwater was performed under the Sitewide Treatability Studies Program (STSP). This study was undertaken to determine the effectiveness of potassium ferrate in a water treatment system to remove the contaminants of concern (COCS) from groundwater at the RFETS. Potassium ferrate is a simple salt where the iron is in the plus six valence state. It is the iron at the plus six valence state (Fe {sup +6}) that makes it an unique water treatment chemical, especially in waters where the pH is greater than seven. In basic solutions where the solubility of the oxides/hydroxides of many of the COCs is low, solids are formed as the pH is raised. By using ferrate these solids are agglomerated so they can be effectively removed by sedimentation in conventional water treatment equipment. The objective of this study was to determine the quality of water after treatment with potassium ferrate and to determine if the Colorado Water Quality Control Commission (CWQCC) discharge limits for the COCs listed in Table 1.0-1 could be met. Radionuclides in the groundwater were of special concern.

  10. Laboratory experiment to determine phosphate release rates from sediments of a formerly oligotrophic lake (Silbersee, Cuxhaven)

    Science.gov (United States)

    Elmarami, Hatem; Greskowiak, Janek; Hamann, Enrico; Massmann, Gudrun

    2016-04-01

    The Silbersee is a small, formerly oligotrophic lake in northwestern Germany which still contains rare character species for oligotrophic lakes (Isoëtes lacustris, Littorella uniflora) threatened by eutrophication. It was suspected that the lake sediments and the redox conditions in the hypolimnon play an important role with regard to eutrophication, potentially releasing phosphorus (P) into the water column. This was the motivation to conduct experiments to estimate the release rate of phosphorus into the lake. It had been noted that the P concentrations in the bottom water were higher during summer in the stagnation phase, when conditions turned sulfidic. Eight sediment cores were taken with a Mondsee-corer (manufactured by UWITEC) at different sites of the lake. The thickness of the sediment within the cores ranged from 15cm to 35 cm and were overlying by approximately 40cm of lake water water. The headspace was approximately 10cm. The cores were stored in a fridge first under oxic, then under anoxic conditions as observed in the lake bottom water in the different seasons. Redox conditions were maintained by bubbling with oxygen and nitrogen gas during the respective time periods. During the experiment, the temperature was held constant to match the water temperature measured at the bottom of the lake (~ 7±1°C). Concentrations of total phosphorus (TP) and dissolved phosphorus (DP), iron (Fe) and dissolved oxygen (DO) as well as pH were measured under oxic and anoxic conditions in the water column. The results showed that TP, DP and Fe concentrations were higher under anoxic conditions than under oxic conditions. The observed increase of phosporous in the water column during the anoxic phase was presumably a result of (i) reductive Fe-oxides dissolution and the corresponding loss of sorption sites and (ii) desorption of phosphorous via surface complexation reactions due to pH changes during the experiment.

  11. Long-distance electron transfer by cable bacteria in aquifer sediments.

    Science.gov (United States)

    Müller, Hubert; Bosch, Julian; Griebler, Christian; Damgaard, Lars Riis; Nielsen, Lars Peter; Lueders, Tillmann; Meckenstock, Rainer U

    2016-08-01

    The biodegradation of organic pollutants in aquifers is often restricted to the fringes of contaminant plumes where steep countergradients of electron donors and acceptors are separated by limited dispersive mixing. However, long-distance electron transfer (LDET) by filamentous 'cable bacteria' has recently been discovered in marine sediments to couple spatially separated redox half reactions over centimeter scales. Here we provide primary evidence that such sulfur-oxidizing cable bacteria can also be found at oxic-anoxic interfaces in aquifer sediments, where they provide a means for the direct recycling of sulfate by electron transfer over 1-2-cm distance. Sediments were taken from a hydrocarbon-contaminated aquifer, amended with iron sulfide and saturated with water, leaving the sediment surface exposed to air. Steep geochemical gradients developed in the upper 3 cm, showing a spatial separation of oxygen and sulfide by 9 mm together with a pH profile characteristic for sulfur oxidation by LDET. Bacterial filaments, which were highly abundant in the suboxic zone, were identified by sequencing of 16S rRNA genes and fluorescence in situ hybridization (FISH) as cable bacteria belonging to the Desulfobulbaceae. The detection of similar Desulfobulbaceae at the oxic-anoxic interface of fresh sediment cores taken at a contaminated aquifer suggests that LDET may indeed be active at the capillary fringe in situ.

  12. Limits to Global Groundwater Consumption

    Science.gov (United States)

    Graaf, I. D.; Van Beek, R.; Sutanudjaja, E.; Wada, Y.; Bierkens, M. F.

    2015-12-01

    In regions with frequent water stress and large aquifer systems, groundwater is often used as an additional fresh water source. For many regions of the world groundwater abstraction exceeds groundwater recharge and persistent groundwater depletion occurs. The most direct effect of groundwater depletion is declining of water tables, leading to reduced groundwater discharge needed to sustain base-flow to e.g. rivers. Next to that, pumping costs increase, wells dry up and land subsidence occurs. These problems are expected to increase in the near future due to growing population and climate changes. This poses the urgent question of what the limits are of groundwater consumption worldwide. We simulate global water availability (5 arc-minute resolution, for 1960-2050) using the hydrological model PCR-GLOBWB (van Beek et al. 2011), coupled to a groundwater model based on MODFLOW (de Graaf et al. 2015), allowing for groundwater - surface water interactions. The groundwater model includes a parameterization of world's confined and unconfined aquifer systems needed for a realistic simulation of groundwater head dynamics. Water demands are included (from Wada et al. 2014). We study the limits to water consumption, focusing on locally attainable groundwater and groundwater levels critical to rivers to sustain low flows. We show an increasing trend (1960-2050) in groundwater head declines, due to increase in groundwater demand. Also, stream flow will decrease and low flow conditions will occur more frequent and will be longer in duration in the near future, especially for irrigated areas. Next to that, we provide a global overview of the years it takes until groundwater gets unattainable for e.g. a local farmer (100 m below land-surface used as a proxy), and estimate the increase in pumping cost for the near future. The results show where and when limits of groundwater consumption are reached globally.

  13. Shallow bedrock limits groundwater seepage-based headwater climate refugia

    Science.gov (United States)

    Briggs, Martin; Lane, John; Snyder, Craig D.; White, Eric A.; Johnson, Zachary; Nelms, David L.; Hitt, Nathaniel P.

    2017-01-01

    Groundwater/surface-water exchanges in streams are inexorably linked to adjacent aquifer dynamics. As surface-water temperatures continue to increase with climate warming, refugia created by groundwater connectivity is expected to enable cold water fish species to survive. The shallow alluvial aquifers that source groundwater seepage to headwater streams, however, may also be sensitive to seasonal and long-term air temperature dynamics. Depth to bedrock can directly influence shallow aquifer flow and thermal sensitivity, but is typically ill-defined along the stream corridor in steep mountain catchments. We employ rapid, cost-effective passive seismic measurements to evaluate the variable thickness of the shallow colluvial and alluvial aquifer sediments along a headwater stream supporting cold water-dependent brook trout (Salvelinus fontinalis) in Shenandoah National Park, VA, USA. Using a mean depth to bedrock of 2.6 m, numerical models predicted strong sensitivity of shallow aquifer temperature to the downward propagation of surface heat. The annual temperature dynamics (annual signal amplitude attenuation and phase shift) of potential seepage sourced from the shallow modeled aquifer were compared to several years of paired observed stream and air temperature records. Annual stream water temperature patterns were found to lag local air temperature by ∼8–19 d along the stream corridor, indicating that thermal exchange between the stream and shallow groundwater is spatially variable. Locations with greater annual signal phase lag were also associated with locally increased amplitude attenuation, further suggestion of year-round buffering of channel water temperature by groundwater seepage. Numerical models of shallow groundwater temperature that incorporate regional expected climate warming trends indicate that the summer cooling capacity of this groundwater seepage will be reduced over time, and lower-elevation stream sections may no longer serve as larger

  14. Impact of agricultural activities on anaerobic processes in stream sediments

    Science.gov (United States)

    Schade, J. D.; Ludwig, S.; Nelson, L. C.; Porterfield, J.; Sather, K. L.; Songpitak, M.; Spawn, S.; Weigel, B.

    2013-12-01

    Streams draining agriculture watersheds are subject to significant anthropogenic impacts, including sedimentation from soil erosion and high nitrate input from heavy fertilizer application. Sedimentation degrades habitat and can reduce hydrologic exchange between surface and subsurface waters. Disconnecting surface and subsurface flow reduces oxygen input to hyporheic water, increasing the extent of anoxic zones in stream sediments and creating hotspots for anaerobic processes like denitrification and methanogenesis that can be important sources of nitrous oxide and methane, both powerful greenhouse gases. Increased nitrate input may influence greenhouse gas fluxes from stream sediments by stimulating rates of denitrification and potentially reducing rates of methanogenesis, either through direct inhibition or by increasing competition for organic substrates from denitrifying bacteria. We hypothesized that accumulation of fine sediments in stream channels would result in high rates of methanogenesis in stream sediments, and that increased nitrate input from agricultural runoff would stimulate denitrification and reduce rates of methane production. Our work focused on streams in northern and central Minnesota, in particular on Rice Creek, a small stream draining an agricultural watershed. We used a variety of approaches to test our hypotheses, including surveys of methane concentrations in surface waters of streams ranging in sediment type and nitrate concentration, bottle incubations of sediment from several sites in Rice Creek, and the use of functional gene probes and RNA analyses to determine if genes for these processes are present and being expressed in stream sediments. We found higher methane concentrations in surface water from streams with large deposits of fine sediments, but significantly less methane in these streams when nitrate concentrations were high. We also found high potential for both methanogenesis and denitrification in sediment incubations

  15. Transport of Gas and Solutes in Permeable Estuarine Sediments

    Science.gov (United States)

    2013-09-30

    profiles in sediment affected by groundwater seepage. Free methane gas builds up below 10 cm depth. The average gas production rate recorded at St...of the nearshore zone (< 2 m water depth), which according to the National Geophysical data center (ETOPO data set, http://www.ngdc.noaa.gov

  16. Biological and chemical characterization of metal bioavailability in sediments from Lake Roosevelt, Columbia River, Washington, USA

    Science.gov (United States)

    Besser, J.M.; Brumbaugh, W.G.; Ivey, C.D.; Ingersoll, C.G.; Moran, P.W.

    2008-01-01

    We studied the bioavailability and toxicity of copper, zinc, arsenic, cadmium, and lead in sediments from Lake Roosevelt (LR), a reservoir on the Columbia River in Washington, USA that receives inputs of metals from an upstream smelter facility. We characterized chronic sediment toxicity, metal bioaccumulation, and metal concentrations in sediment and pore water from eight study sites: one site upstream in the Columbia River, six sites in the reservoir, and a reference site in an uncontaminated tributary. Total recoverable metal concentrations in LR sediments generally decreased from upstream to downstream in the study area, but sediments from two sites in the reservoir had metal concentrations much lower than adjacent reservoir sites and similar to the reference site, apparently due to erosion of uncontaminated bank soils. Concentrations of acid-volatile sulfide in LR sediments were too low to provide strong controls on metal bioavailability, and selective sediment extractions indicated that metals in most LR sediments were primarily associated with iron and manganese oxides. Oligochaetes (Lumbriculus variegatus) accumulated greatest concentrations of copper from the river sediment, and greatest concentrations of arsenic, cadmium, and lead from reservoir sediments. Chronic toxic effects on amphipods (Hyalella azteca; reduced survival) and midge larvae (Chironomus dilutus; reduced growth) in whole-sediment exposures were generally consistent with predictions of metal toxicity based on empirical and equilibrium partitioning-based sediment quality guidelines. Elevated metal concentrations in pore waters of some LR sediments suggested that metals released from iron and manganese oxides under anoxic conditions contributed to metal bioaccumulation and toxicity. Results of both chemical and biological assays indicate that metals in sediments from both riverine and reservoir habitats of Lake Roosevelt are available to benthic invertebrates. These findings will be used as

  17. The importance of shallow confining units to submarine groundwater flow

    Science.gov (United States)

    Bratton, J.F.

    2007-01-01

    In addition to variable density flow, the lateral and vertical heterogeneity of submarine sediments creates important controls on coastal aquifer systems. Submarine confining units produce semi-confined offshore aquifers that are recharged on shore. These low-permeability deposits are usually either late Pleistocene to Holocene in age, or date to the period of the last interglacial highstand. Extensive confining units consisting of peat form in tropical mangrove swamps, and in salt marshes and freshwater marshes and swamps at mid-latitudes. At higher latitudes, fine-grained glaciomarine sediments are widespread. The net effect of these shallow confining units is that groundwater from land often flows farther offshore before discharging than would normally be expected. In many settings, the presence of such confining units is critical to determining how and where pollutants from land will be discharged into coastal waters. Alternatively, these confining units may also protect fresh groundwater supplies from saltwater intrusion into coastal wells.

  18. Trace elements in groundwater as indicators of anthropogenic impact

    Science.gov (United States)

    Levins, Igors; Gosk, Edmund

    2008-07-01

    The distribution of several minor and trace elements mainly in fresh (dominating TDS 160 400 mg/l) groundwater of Latvia have been investigated by the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) technique. An evaluation of results of about 700 analyses leads to the conclusion that concentrations of these elements is influenced by: pH Eh conditions, groundwater residence time and diffuse contamination, whereas the role of water-bearing sediments is of secondary importance. Most trace elements are characterised by low mobility under alkaline and reducing conditions; concentrations in confined aquifers are much smaller than the Maximum Permissible Values for drinking water. The strongest anomalies of REE, Al and P were found in shallow groundwater around the former agrochemical storehouses.

  19. Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

    Science.gov (United States)

    Rattray, Gordon W.; Ginsbach, Michael L.

    2014-01-01

    The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake

  20. Complexity of Groundwater Contaminants at DOE Sites

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, T.C.; Faybishenko, B.; Jordan, P.

    2010-12-03

    The U.S. Department of Energy (DOE) is responsible for the remediation and long-term stewardship of one of the world's largest groundwater contamination portfolios, with a significant number of plumes containing various contaminants, and considerable total mass and activity. As of 1999, the DOE's Office of Environmental Management was responsible for remediation, waste management, or nuclear materials and facility stabilization at 144 sites in 31 states and one U.S. territory, out of which 109 sites were expected to require long-term stewardship. Currently, 19 DOE sites are on the National Priority List. The total number of contaminated plumes on DOE lands is estimated to be 10,000. However, a significant number of DOE sites have not yet been fully characterized. The most prevalent contaminated media are groundwater and soil, although contaminated sediment, sludge, and surface water also are present. Groundwater, soil, and sediment contamination are present at 72% of all DOE sites. A proper characterization of the contaminant inventory at DOE sites is critical for accomplishing one of the primary DOE missions -- planning basic research to understand the complex physical, chemical, and biological properties of contaminated sites. Note that the definitions of the terms 'site' and 'facility' may differ from one publication to another. In this report, the terms 'site,' 'facility' or 'installation' are used to identify a contiguous land area within the borders of a property, which may contain more than one plume. The term 'plume' is used here to indicate an individual area of contamination, which can be small or large. Even though several publications and databases contain information on groundwater contamination and remediation technologies, no statistical analyses of the contaminant inventory at DOE sites has been prepared since the 1992 report by Riley and Zachara. The DOE Groundwater Data Base

  1. Oxic and anoxic mineralization of simple carbon substrates in peat at low temperatures

    Science.gov (United States)

    Segura, Javier; Sparrman, Tobias; Nilsson, Mats; Schleucher, Jürgen; Öquist, Mats

    2016-04-01

    Northern peatlands store approximately one-quarter of the world's soil carbon and typically act as net carbon sinks. However a large fraction of the carbon fixed during the growing season can be emitted back to the atmosphere during winter as CO2 and CH4, despite low temperatures and frozen conditions, making low temperature biogeochemical processes crucial for the long-term net ecosystem carbon balance. However, the metabolic processes driving carbon mineralization under winter conditions are poorly understood and whether or not peat microbial communities can maintain metabolic activity at temperatures below freezing is uncertain. Here we present results from an incubation study aimed at elucidating the potential of peat microbial communities to mineralize simple carbon substrates to CO2 and CH4 at low temperatures. Peat samples from the acrotelm were amended with [13C]- glucose and incubated at -5 °C, -3 °C, +4 °C, and +9 °C under both oxic and anoxic conditions, and rates of CO2 and CH4 production were determined. In addition, incorporation of the labelled substrate into phospholipid fatty acids (PLFAs) were determined to account for microbial growth during mineralization and the metabolic partitioning between catabolic and anabolic activity. Biogenic [13C]-CO2 was produced from the added substrate in peat samples incubated both under oxic and anoxic conditions. Under oxic conditions the production rates were 3.5, 2.3, 0.3 and 0.07 mg CO2 g SOM-1day-1 at +9 °C, +4 °C, -3 °C and -5 °C, respectively, and corresponding rates for anoxic conditions were 1.1, 1.0, 0.03 and 0.01 mg CO2 g SOM-1day-1. Consequently the observed Q10 values of the temperature sensitivity under both oxic and anoxic conditions increased dramatically upon soil freezing. However, anoxic mineralization appears less sensitive to temperature as compared to when oxygen is present. Methane was also produced and detected across the range of the incubation temperatures in the anoxic

  2. Petroleum biodegradation studied in sediment-flow-through systems simulating natural oil seepage in marine sediments

    Science.gov (United States)

    Mishra, Sonakshi; Wefers, Peggy; Steeb, Philip; Schmidt, Mark; Treude, Tina

    2014-05-01

    The natural biodegradation of hydrocarbons depends on several environmental factors like nutrients, salinity, temperature, pressure, redox-conditions and composition of crude oil. Petroleum migrating from depth into marine surface sediments at natural seep sites could be subjected to a sequence of different kind of microbial processes which is controlled by a strong redox gradient within a thin sediment segment. Most studies on microbial degradation of petroleum have focused either only on selected hydrocarbon fractions or on cultured microbes. This study, however, attempts to investigate the natural microbial response of marine sediments to crude oil seepage with detailed analysis of sediment and porewater geochemistry, hydrocarbon degradation products, microbial activity, and microbial genetics. A sediment-oil-flow-through-system was established where crude oil migrated through the bottom of (approximately 30 cm long) intact marine sediment cores simulating a natural seepage scenario. Electron acceptor-rich oxic seawater was provided at the top of the core and anoxic conditions were established at the bottom of the cores. The intact sediment cores had been sampled from the Caspian Sea (near Baku) and the North Alex Mud Volcano in the Mediterranean Sea. The Caspian Sea and the North Alex Mud Volcano are both sites with active transport of hydrocarbons from depth by mud volcano activity. The geochemical changes in the sediment cores during oil seepage were monitored by using microelectrodes and porewater analyses. The geochemical analysis was later followed by hydrocarbon and molecular analyses at the end of the experiment by slicing the cores. First results based on the biogeochemistry of the sediment cores and hydrocarbon analyses are presented here. Porewater profiles of hydrogen sulfide and sulfate during the experimental runs gave first indications of microbial response and sulfate reduction due to the addition of crude oil. The core from North Alex Mud

  3. DS796 California Groundwater Units

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The California Groundwater Units dataset classifies and delineates the State into one of three groundwater based polygon units: (1) those areas defined as alluvial...

  4. [Construction and evaluation of an engineered bacterial strain for producing lipopeptide under anoxic conditions].

    Science.gov (United States)

    Liang, Xiao-long; Zhao, Feng; Shi, Rong-jiu; Ban, Yun-he; Zhou, Ji-dong; Han, Si-qin; Zhang, Ying

    2015-08-01

    Biosurfactant-facilitated oil recovery is one of the most important aspects of microbial enhanced oil recovery (MEOR). However, the biosurfactant production by biosurfactant-producing microorganisms, most of which are aerobes, is severely suppressed due to the in-situ anoxic conditions within oil reservoirs. In this research, we successfully engineered a strain JD-3, which could grow rapidly and produce lipopeptide under anoxic conditions, by protoplast confusion using a Bacillus amyloliquefaciens strain BQ-2 which produces biosurfactant aerobically, and a facultative anaerobic Pseudomonas stutzeri strain DQ-1 as parent strains. The alignment of 16S rDNA sequence (99% similarity) and comparisons of cell colony morphology showed that fusant JD-3 was closer to the parental strain B. amyloliquefaciens BQ-2. The surface tension of culture broth of fusant JD-3, after 36-hour cultivation under anaerobic conditions, decreased from initially 63.0 to 32.5 mN · m(-1). The results of thin layer chromatography and infrared spectrum analysis demonstrated that the biosurfactant produced by JD-3 was lipopeptide. The surface-active lipopeptide had a low critical micelle concentration (CMC) of 90 mg · L(-1) and presented a good ability to emulsify various hydrocarbons such as crude oil, liquid paraffin, and kerosene. Strain JD-3 could utilize peptone as nitrogen source and sucrose, glucose, glycerin or other common organics as carbon sources for anaerobic lipopeptide synthesis. The subculture of fusant JD-3 showed a stable lipopeptide-producing ability even after ten serial passages. All these results indicated that fusant JD-3 holds a great potential to microbially enhance oil recovery under anoxic conditions.

  5. Simultaneous carbon and nitrogen removal in anoxic-aerobic circulating fluidized bed biological reactor (CFBBR).

    Science.gov (United States)

    Cui, Y; Nakhla, G; Zhu, J; Patel, A

    2004-06-01

    Biological nutrient removal (BNR) in municipal wastewater treatment to remove carbonaceous substrates and nutrients, has recently become increasingly popular worldwide due to increasingly stringent regulations. Biological fluidized bed (BFB) technology, which could be potentially used for BNR, can provide some advantages such as high efficiency and a compact structure. This work shows the results of simultaneous elimination of organic carbon and nitrogen using a circulating fluidized bed biological reactor (CFBBR, which has been developed recently for chemical engineering processes. The CFBBR has two fluidized beds, running as anoxic and aerobic processes to accomplish simultaneous nitrification and denitrification, with continuous liquid recirculation through the anoxic bed and the aerobic bed. Soluble COD concentrations in the effluent ranging from 4 to 20 mg l(-1) were obtained at varying COD loading rates; ammonia nitrogen removal efficiencies averaged in excess of 99% at a minimum total hydraulic retention time (HRT) of 2.0 hours over a temperature range of 25 degrees C to 28 degrees C. Effluent nitrate nitrogen concentration of less than 5 mg l(-1) was achieved by increasing effluent recycle rate. No nitrite accumulation was observed either in the anoxic bed or in the aerobic bed. The system was able to treat grit chamber effluent wastewater at a HRT of 2.0 hours while achieving average effluent BOD, COD, NH3-N, TKN, nitrates, total phosphate, TSS and VSS concentrations of 10 mg l(-1), 18 mg l(-1), 1.3 mg l(-1), 1.5 mg l(-1), 7 mg l(-1), 2.0 mg l(-1), 10 mg l(-1) and 8 mg l(-1) respectively. The CFBBR appears to be not only an excellent alternative for conventional activated sludge type BNR technologies but also capable of processing much higher loadings that are suitable for industrial applications.

  6. Nerve Growth Factor Inhibits Gd3+-sensitive Calcium Influx and Reduces Chemical Anoxic Neuronal Death

    Institute of Scientific and Technical Information of China (English)

    Hui JIANG; Shunlian TIAN; Yan ZENG; Jing SHI

    2008-01-01

    To investigate whether glutamate and voltage-gated calcium channels-independent calcium influx exists during acute anoxic neuronal damage and its possible relationship to neuronal protective function of NGF. In in vitro model of acute anoxia, hippocampal cultures from newborn rats were exposed to 3 mmol/L KCN. Changes of intracellular Ca2+ concentration ([Ca2+]i) were monitored by con-focal imaging and cell viability was assayed by PI and cFDA staining. The results showed that after treatment with primary hippocampal cultures with 3 mmol/L KCN for 15 min,[Ca2+]i was significantly increased 6.27-fold compared to pre-anoxia level and 73.3% of the cells died.When combination of 20 μmol/L MK-801 (glutamate receptor antagonist), 40 μmol/L CNQX (AMPA receptor antagonist) and 5 μmol/L nimodipine (voltage-gated calcium channel antagonist) (hereafter denoted as MCN) were administrated to hippocampal cultures, levels of [Ca2+]i and cell death rate induced by KCN were partially reduced by 35.9% and 47.5% respectively. However, Gd3+ (10μmol/L) almost completely blocked KCN-mediated [Ca2+]i elevation by 81.9% and reduced neuronal death by 88.8% in the presence of MCN. It is noteworthy that NGF, used in combination with MCN,inhibited KCN-induced [Ca2+]i increase by 77.4% and reduced cell death by 87.1%. Only PLC inhibitor U73122 (10 μmol/L) abolished NGF effects. It is concluded that Gd3+-sensitive calcium influx,which is NMDA (glutamate receptor) and voltage-gated calcium channels-independent, is responsible for acute anoxic neuronal death. NGF can inhibit Gd3+-sensitive calcium influx and reduce anoxic neuronal death through activating PLC pathway.

  7. Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries

    Science.gov (United States)

    Wieczorek, A. S.; Hetz, S. A.; Kolb, S.

    2014-06-01

    Microbial degradation of chitin in soil substantially contributes to carbon cycling in terrestrial ecosystems. Chitin is globally the second most abundant biopolymer after cellulose and can be deacetylated to chitosan or can be hydrolyzed to N,N'-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities is unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, and carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation, along with ammonification, were likely responsible for anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of less than 50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions on community level.

  8. Vivianite precipitation and phosphate sorption following iron reduction in anoxic soils.

    Science.gov (United States)

    Heiberg, Lisa; Koch, Christian Bender; Kjaergaard, Charlotte; Jensen, Henning S; Hans Christian, B Hansen

    2012-01-01

    Phosphorus retention in lowland soils depends on redox conditions. The aim of this study was to evaluate how the Fe(III) reduction degree affects phosphate adsorption and precipitation. Two similarly P-saturated, ferric Fe-rich lowland soils, a sandy and a peat soil, were incubated under anaerobic conditions. Mössbauer spectroscopy demonstrated that Fe(III) in the sandy soil was present as goethite and phyllosilicates, whereas Fe(III) in the peat soil was mainly present as polynuclear, Fe-humic complexes. Following anoxic incubation, extensive formation of Fe(II) in the solids occurred. After 100 d, the Fe(II) production reached its maximum and 34% of the citrate-bicarbonate-dithionite extractable Fe (Fe(CBD)) was reduced to Fe(II) in the sandy soil. The peat soil showed a much faster reduction of Fe(III) and the maximum reduction of 89% of Fe(CBD) was reached after 200 d. Neoformation of a metavivianite/vivianite phase under anoxic conditions was identified by X-ray diffraction in the peat. The sandy soil exhibited small changes in the point of zero net sorption (EPC₀) and P(i) desorption with increasing Fe(III) reduction, whereas in the peat soil P desorption increased from 80 to 3100 μmol kg⁻¹ and EPC₀ increased from 1.7 to 83 μM, after 322 d of anoxic incubation. The fast Fe(III) reduction made the peat soils particularly vulnerable to changes in redox conditions. However, the precipitation of vivianite/metavivianite minerals may control soluble P(i) concentrations to between 2 and 3 μM in the long term if the soil is not disturbed.

  9. Tehran Groundwater Chemical Pollution

    Directory of Open Access Journals (Sweden)

    M- Shariatpanahi

    1990-06-01

    Full Text Available Seventy eight wells water sample of Tehran plain were examined to determine r its groundwaters chemical pollution. Tehran s groundwaters are slightly acidic and their total dissolved solids are high and are in the hard water category."nThe nitrate concentration of wells water of west region is less than per¬missible level of W.H.O. standard, whereas, the nitrate concentration of some of the other regions wells exceed W.H.O. standard which is indication of pollution"nwith municipal wastewaters. The concentration of toxic elements Cr, Cd, As, Hg and"ni Pb of some of the west, east and south regions wells of Tehran is more than per¬missible level of W.H.O. standard, whereas, the concentration of Cu, Zn,Mn and detergents is below W.H.O. standard."n1"nIn general, the amount of dissolved materials of Tehran s groundwaters and also"ni the potential of their contamination with nitrate is increased as Tehran s ground-"nwaters move further to the south, and even though, Tehran s groundwaters contamination with toxic elements is limited to the industrial west district, industrial-residential east and south districts, but»with regard to the disposal methods of"nt municipal and industrial wastewaters, if Tehran s groundwaters pollution continues,"nlocal contamination of groundwaters is likely to spread. So that finally their quality changes in such a way that this water source may become unfit for most domestic, industrial and agricultural uses. This survey shows the necessity of collection and treatment of Tehran s wastewaters and Prevention of the disposal of untreated wastewaters into the environment.

  10. Investigating groundwater arsenic contamination using aquifer push-pull test

    Science.gov (United States)

    Daigle, A. R.; Jin, Q.

    2009-12-01

    The groundwater of the Southern Willamette Basin, OR is contaminated with arsenic at concentrations as high as several ppm. A single-well push-pull test was conducted to investigate how microbial metabolisms control arsenic occurrence and levels in the bedrock aquifer of the area. During the experiments, a test solution containing ethanol was first injected into the aquifer. As the experiment progressed, dissolved gasses, groundwater, and sediment were sampled to monitor the variations in the chemical parameters, including the speciation of iron, sulfur, and arsenic, in the aquifer. Ethanol amendment stimulated a series of microbial metabolisms, including arsenate reduction, iron reduction, and sulfate reduction. Iron reduction released arsenic sorbed onto the aquifer sediments, increasing groundwater arsenic levels. Arsenate reduction converted arsenate to arsenite and, as a result, most arsenic occurred as arsenite in the groundwater. Results of the experiments demonstrate how different microbial functional groups influenced arsenic contamination in the area. These results also shed new light on potential bioremediation strategies in the area.

  11. Microscopic and Spectroscopic Characterisation of Waterlogged Archaeological Softwood from Anoxic Environments

    DEFF Research Database (Denmark)

    Pedersen, Nanna Bjerregaard

    Confocal Raman imaging, UV-microspectrophotometry, light microscopy, transmission electron microscopy, compositional analysis, and ATR-FTIR spectroscopy has been applied to waterlogged archaeological Norway spruce [Picea abies (L.) Karst] and Scots pine [Pinus sylvestris L.] retrieved from anoxic...... waterlogged sites and solely decayed by erosion bacteria to refine the understanding of the residual wood structure left after degradation. This was done not only to improve the ability to develop suitable and cost effective conservations treatments but also to improve the understanding of anaerobic decay...

  12. Butyltin speciation in sediments from Todos os Santos Bay (Bahia, Brazil by GC-PFPD

    Directory of Open Access Journals (Sweden)

    Juliana Feitosa Felizzola

    2008-01-01

    Full Text Available Butyltin compounds were investigated in surface sediments from 17 stations in Todos os Santos Bay. Analytical conditions for organotin determination in marine sediments were optimized for GC with pulsed flame photometric detection. Detection limits were: 5.4 µg kg-1 for TBT; 0.2 µg kg-1 for DBT; and 2.1 µg kg-1 for MBT, using a 610-nm filter. In general, TBT concentrations were low and in the range of

    anoxic conditions in the sediments. The presence of paint particles in the sediments and degradation in the water column during resuspension events followed by removal of the more soluble DBT and MBT may explain these observations.

  13. In situ groundwater bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, Terry C.

    2009-02-01

    In situ groundwater bioremediation of hydrocarbons has been used for more than 40 years. Most strategies involve biostimulation; however, recently bioaugmentation have been used for dehalorespiration. Aquifer and contaminant profiles are critical to determining the feasibility and strategy for in situ groundwater bioremediation. Hydraulic conductivity and redox conditions, including concentrations of terminal electron acceptors are critical to determine the feasibility and strategy for potential bioremediation applications. Conceptual models followed by characterization and subsequent numerical models are critical for efficient and cost effective bioremediation. Critical research needs in this area include better modeling and integration of remediation strategies with natural attenuation.

  14. Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

    Science.gov (United States)

    Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

    2015-01-01

    This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser

  15. Crab burrows as conduits for groundwater-surface water exchange in Bangladesh

    Science.gov (United States)

    Stahl, Mason O.; Tarek, M. H.; Yeo, Darren C. J.; Badruzzaman, A. B. M.; Harvey, Charles F.

    2014-12-01

    Groundwater recharge affects water budgets and groundwater quality on the deltas and floodplains of South and Southeast Asia. Rain and flooding rivers recharge groundwater during the monsoon; irrigated rice fields and surface water bodies recharge aquifers during the dry season. Groundwater throughout the region is severely contaminated by arsenic, and recent research suggests that quantifying and characterizing recharge is important to understand whether recharge flushes or mobilizes arsenic from aquifers. At a field site in Bangladesh, we found that burrows of terrestrial crabs short-circuit low-permeability surface sediments, providing the primary conduit for recharge. We combine field observations along with a model that couples isotope and water balances to quantify the effect of crab burrows on aquifer recharge. Given the wide distribution of burrowing crabs and the surficial geology, we suggest that crab burrows provide widespread conduits for groundwater recharge.

  16. Removal of Organic Pollutants in Municipal Wastewater for Artificial Groundwater Recharge

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to construct a demonstration artificial groundwater recharge system for wastewater reuse in China, three years of laboratory work has been conducted on advanced treatment technologies in combination with soil aquifer treatment of secondary effluent from sewage treatment plants. An effective and inexpensive process was selected, which uses DGB adsorption, PAC coagulation, sedimentation, sand filtration, ozone disinfection, and soil aquifer treatment. The effluent meets the recommended water quality criteria for groundwater recharge. Ozonation is effective for disinfection as well as for water quality improvement. Results showed that the total N in the SAT system remained constant thus the secondary effluent must have a low NH3-N concentration for groundwater recharge.

  17. Groundwater: A Community Action Guide.

    Science.gov (United States)

    Boyd, Susan, Ed.; And Others

    Designed to be a guide for community action, this booklet examines issues and trends related to groundwater contamination. Basic concepts about groundwater and information about problems affecting it are covered under the categories of (1) what is groundwater? (2) availability and depletion; (3) quality and contamination; (4) public health…

  18. The effect of biogenic Fe(II) on the stability and sorption of Co(II)EDTA 2- to goethite and a subsurface sediment

    Science.gov (United States)

    Zachara, John M.; Smith, Steven C.; Fredrickson, James K.

    2000-04-01

    Laboratory experiments were conducted with suspensions of goethite (α-FeOOH) and a subsurface sediment to assess the influence of bacterial iron reduction on the fate of Co(II)EDTA 2-, a representative metal-ligand complex of intermediate stability (log K Co(II)EDTA = 17.97). The goethite was synthetic (ca. 55 m 2/g) and the sediment was a Pleistocene age, Fe(III) oxide-containing material from the Atlantic coastal plain (Milford). Shewanella alga strain BrY, a dissimilatory iron reducing bacterium (DIRB), was used to promote Fe(III) oxide reduction. Sorption isotherms and pH adsorption edges were measured for Co 2+, Fe 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- on the two sorbents in 0.001 mol/L Ca(ClO 4) 2 to aid in experiment interpretation. Anoxic suspensions of the sorbents in PIPES buffer at pH 6.5-7.0 were spiked with Co(II)EDTA 2- (10 -5 mol/L, 60Co and 14EDTA labeled), inoculated with BrY (1-6 × 10 8 organisms/mL), and the headspace filled with a N 2/H 2 gas mix. The experiments were conducted under non-growth conditions. The medium did not contain PO 43- (with one exception), trace elements, or vitamins. The tubes were incubated under anoxic conditions at 25°C for time periods in excess of 100 d. Replicate tubes were sacrificed and analyzed at desired time periods for pH, Fe(II) TOT, Fe (aq)2+, 60Co, and 14EDTA. Abiotic analogue experiments were conducted where Fe (aq)2+ was added in increasing concentration to Co(II)EDTA 2-/mineral suspensions to simulate the influence of bacterial Fe(II) evolution. The DIRB generated Fe(II) from both goethite and the Milford sediment that was strongly sorbed by mineral surfaces. Aqueous Fe 2+ increased during the experiment as surfaces became saturated; Fe (aq)2+ induced the dissociation of Co(II)EDTA 2- into a mixture of Co 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- (log K Fe(II)EDTA = 15.98). The extent of dissociation of Co(II)EDTA 2- was greater in the subsurface sediment because it sorbed Fe(II) less strongly than did

  19. Integrating turbulent flow, biogeochemical, and poromechanical processes in rippled coastal sediment (Invited)

    Science.gov (United States)

    Cardenas, M. B.; Cook, P. L.; Jiang, H.; Traykovski, P.

    2010-12-01

    Coastal sediments are the locus of multiple coupled processes. Turbulent flow associated with waves and currents induces porewater flow through sediment leading to fluid exchange with the water column. This porewater flow is determined by the hydraulic and elastic properties of the sediment. Porewater flow also ultimately controls biogeochemical reactions in the sediment whose rates depend on delivery of reactants and export of products. We present results from numerical modeling studies directed at integrating these processes with the goal of shedding light on these complex environments. We show how denitrification rates inside ripples are largest at intermediate permeability which represents the optimal balance of reactant delivery and anoxic conditions. It is clear that nutrient cycling and distribution within the sediment is strongly dependent on the character of the multidimensional flow field inside of sediment. More recent studies illustrate the importance of the elastic properties of the saturated sediment on modulating fluid exchange between the water column and the sediment when pressure fluctuations along the sediment-water interface occur at the millisecond scale. Pressure fluctuations occur at this temporal scale due to turbulence and associated shedding of vortices due to the ripple geometry. This suggests that biogeochemical cycling may also be affected by these high-frequency elastic effects. Future studies should be directed towards this and should take advantage of modeling tools such as those we present.

  20. Characteristics of high arsenic groundwater in Hetao Basin, Inner Mongolia, northern China

    Institute of Scientific and Technical Information of China (English)

    YangChun Zhu; XueYong Zhao; Min Chen; YongQing Luo; Xin Zhou

    2015-01-01

    It is well known that the Hetao Basin is one of the most seriously arsenic-affected groundwater areas in China. In order to understand the characteristics of high arsenic (As) groundwater in the Basin, a brief overview of arsenic in groundwater follows. High arsenic in the Basin commonly occurs in shallow groundwater and the total arsenic concentrations range from 0.58 to 572 µg/L (average 99.73 µg/L), exceeding the maximum mandated value of 10 µg/L for drinking water in China;As(Ш) is the predominant species. The regional distribution pattern of arsenic in the groundwater increases from south/southeast to north/northwest. Hangjinhouqi and Wuyuan counties are considered as the most seriously affected areas, with high incidences of endemic arsenicosic diseases in the Hetao Basin. High groundwater arsenic correlates with the increase of well depth. Previous studies proposed that groundwater arsenic in the Basin is mainly originated from desorption of some natural solid materials in the sediments, under reducing condition. Generally, reducing condition is believed to be the primary factor for arsenic releasing from the sediment to groundwater in the region. Under inorganic or bacterial processes, Fe2O3 changes to FeS and arsenic adsorbed to Fe(OH)3 dissolves into groundwater, and As(V) is re-duced to As(Ш). Besides, reducing environments, groundwater hydraulic gradients, organic matter, pH, evapotranspiration, and soil texture are presumed to be the predominant factors that control arsenic mobilization.

  1. PATHS groundwater hydrologic model

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, R.W.; Schur, J.A.

    1980-04-01

    A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

  2. Ubiquitous Gammaproteobacteria dominate dark carbon fixation in coastal sediments.

    Science.gov (United States)

    Dyksma, Stefan; Bischof, Kerstin; Fuchs, Bernhard M; Hoffmann, Katy; Meier, Dimitri; Meyerdierks, Anke; Pjevac, Petra; Probandt, David; Richter, Michael; Stepanauskas, Ramunas; Mußmann, Marc

    2016-08-01

    Marine sediments are the largest carbon sink on earth. Nearly half of dark carbon fixation in the oceans occurs in coastal sediments, but the microorganisms responsible are largely unknown. By integrating the 16S rRNA approach, single-cell genomics, metagenomics and transcriptomics with (14)C-carbon assimilation experiments, we show that uncultured Gammaproteobacteria account for 70-86% of dark carbon fixation in coastal sediments. First, we surveyed the bacterial 16S rRNA gene diversity of 13 tidal and sublittoral sediments across Europe and Australia to identify ubiquitous core groups of Gammaproteobacteria mainly affiliating with sulfur-oxidizing bacteria. These also accounted for a substantial fraction of the microbial community in anoxic, 490-cm-deep subsurface sediments. We then quantified dark carbon fixation by scintillography of specific microbial populations extracted and flow-sorted from sediments that were short-term incubated with (14)C-bicarbonate. We identified three distinct gammaproteobacterial clades covering diversity ranges on family to order level (the Acidiferrobacter, JTB255 and SSr clades) that made up >50% of dark carbon fixation in a tidal sediment. Consistent with these activity measurements, environmental transcripts of sulfur oxidation and carbon fixation genes mainly affiliated with those of sulfur-oxidizing Gammaproteobacteria. The co-localization of key genes of sulfur and hydrogen oxidation pathways and their expression in genomes of uncultured Gammaproteobacteria illustrates an unknown metabolic plasticity for sulfur oxidizers in marine sediments. Given their global distribution and high abundance, we propose that a stable assemblage of metabolically flexible Gammaproteobacteria drives important parts of marine carbon and sulfur cycles.

  3. Anaerobic oxidation of methane by sulfate in hypersaline groundwater of the Dead Sea aquifer.

    Science.gov (United States)

    Avrahamov, N; Antler, G; Yechieli, Y; Gavrieli, I; Joye, S B; Saxton, M; Turchyn, A V; Sivan, O

    2014-11-01

    Geochemical and microbial evidence points to anaerobic oxidation of methane (AOM) likely coupled with bacterial sulfate reduction in the hypersaline groundwater of the Dead Sea (DS) alluvial aquifer. Groundwater was sampled from nine boreholes drilled along the Arugot alluvial fan next to the DS. The groundwater samples were highly saline (up to 6300 mm chlorine), anoxic, and contained methane. A mass balance calculation demonstrates that the very low δ(13) CDIC in this groundwater is due to anaerobic methane oxidation. Sulfate depletion coincident with isotope enrichment of sulfur and oxygen isotopes in the sulfate suggests that sulfate reduction is associated with this AOM. DNA extraction and 16S amplicon sequencing were used to explore the microbial community present and were found to be microbial composition indicative of bacterial sulfate reducers associated with anaerobic methanotrophic archaea (ANME) driving AOM. The net sulfate reduction seems to be primarily controlled by the salinity and the available methane and is substantially lower as salinity increases (2.5 mm sulfate removal at 3000 mm chlorine but only 0.5 mm sulfate removal at 6300 mm chlorine). Low overall sulfur isotope fractionation observed ((34) ε = 17 ± 3.5‰) hints at high rates of sulfate reduction, as has been previously suggested for sulfate reduction coupled with methane oxidation. The new results demonstrate the presence of sulfate-driven AOM in terrestrial hypersaline systems and expand our understanding of how microbial life is sustained under the challenging conditions of an extremely hypersaline environment.

  4. Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

    Institute of Scientific and Technical Information of China (English)

    PENG Yongzhen; HOU Hongxun; WANG Shuying; CUI Youwei; Zhiguo Yuan

    2008-01-01

    To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal(SNDPR),a whole course of SNDPR damage and recovery was studied in a pilot-scale,anaerobicanoxic oxidation ditch(OD),where the volumes of anaerobic zone,anoxic zone,and ditches zone of the OD system were 7,21,and 280L,respectively.The reactor was fed with municipal wastewater with a flow rate of 336 L/d.The concept of simultaneous nitrification and denitrification (SND)rate(rSND) was put forward to quantify SND.The results indicate that:(1)high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase,total nitrogen (TN) and total phosphate(TP) removal rates were 80%and 85%,respectively;(2)when the system was aerated excessively,the stability of SND was damaged,and rSND dropped from 80% to 20%or less;(3)the natural logarithm of the ratio of NOx to MJ4+ in the effluent had a linear correlation to oxidation-reduction potential (ORP);(4)when NO3- was less than 6 mg/L.high phosphorus removal efficiency could be achieved;(5)denitrifying phosphorus removal (DNPR) could take place in the anaerobic-anoxic OD system.The major innovation was that the SND rate was devised and quantified.

  5. Anoxic biodegradation of dimethyl phthalate (DMP) by activated sludge cultures under nitrate-reducing conditions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate (DMP) biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC-MS) analysis, mono-methyl phthalate (MMP) and phthalic acid (PA) were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand (CODCr) removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP → MMP → PA → … → CO2 + H2O.The molar ratio of DMP to nitrate consumed was found to be 9.0:1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4℃, respectively.

  6. Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery

    Science.gov (United States)

    Clarkson, M. O.; Wood, R. A.; Poulton, S. W.; Richoz, S.; Newton, R. J.; Kasemann, S. A.; Bowyer, F.; Krystyn, L.

    2016-07-01

    The end-Permian mass extinction, ~252 million years ago, is notable for a complex recovery period of ~5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe-S-C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota.

  7. Lenticulostriate arterial distribution pathology may underlie pediatric anoxic brain injury in drowning

    Science.gov (United States)

    Ishaque, Mariam; Manning, Janessa H.; Woolsey, Mary D.; Franklin, Crystal G.; Tullis, Elizabeth W.; Fox, Peter T.

    2016-01-01

    Drowning is a leading cause of neurological morbidity and mortality in young children. Anoxic brain injury (ABI) can result from nonfatal drowning and typically entails substantial neurological impairment. The neuropathology of drowning-induced pediatric ABI is not well established. Specifically, quantitative characterization of the spatial extent and tissue distribution of anoxic damage in pediatric nonfatal drowning has not previously been reported but could clarify the underlying pathophysiological processes and inform clinical management. To this end, we used voxel-based morphometric (VBM) analyses to quantify the extent and spatial distribution of consistent, between-subject alterations in gray and white matter volume. Whole-brain, high-resolution T1-weighted MRI datasets were acquired in 11 children with chronic ABI and 11 age- and gender-matched neurotypical controls (4–12 years). Group-wise VBM analyses demonstrated predominantly central subcortical pathology in the ABI group in both gray matter (bilateral basal ganglia nuclei) and white matter (bilateral external and posterior internal capsules) (P < 0.001); minimal damage was found outside of these deep subcortical regions. These highly spatially convergent gray and white matter findings reflect the vascular distribution of perforating lenticulostriate arteries, an end-arterial watershed zone, and suggest that vascular distribution may be a more important determinant of tissue loss than oxygen metabolic rate in pediatric ABI. Further, these results inform future directions for diagnostic and therapeutic modalities. PMID:26937385

  8. Lenticulostriate arterial distribution pathology may underlie pediatric anoxic brain injury in drowning

    Directory of Open Access Journals (Sweden)

    Mariam Ishaque

    2016-01-01

    Full Text Available Drowning is a leading cause of neurological morbidity and mortality in young children. Anoxic brain injury (ABI can result from nonfatal drowning and typically entails substantial neurological impairment. The neuropathology of drowning-induced pediatric ABI is not well established. Specifically, quantitative characterization of the spatial extent and tissue distribution of anoxic damage in pediatric nonfatal drowning has not previously been reported but could clarify the underlying pathophysiological processes and inform clinical management. To this end, we used voxel-based morphometric (VBM analyses to quantify the extent and spatial distribution of consistent, between-subject alterations in gray and white matter volume. Whole-brain, high-resolution T1-weighted MRI datasets were acquired in 11 children with chronic ABI and 11 age- and gender-matched neurotypical controls (4–12 years. Group-wise VBM analyses demonstrated predominantly central subcortical pathology in the ABI group in both gray matter (bilateral basal ganglia nuclei and white matter (bilateral external and posterior internal capsules (P < 0.001; minimal damage was found outside of these deep subcortical regions. These highly spatially convergent gray and white matter findings reflect the vascular distribution of perforating lenticulostriate arteries, an end-arterial watershed zone, and suggest that vascular distribution may be a more important determinant of tissue loss than oxygen metabolic rate in pediatric ABI. Further, these results inform future directions for diagnostic and therapeutic modalities.

  9. Microbial community in anoxic-oxic-settling-anaerobic sludge reduction process revealed by 454 pyrosequencing analysis.

    Science.gov (United States)

    Ning, Xinqiang; Qiao, Wenwen; Zhang, Lei; Gao, Xu

    2014-12-01

    Modification of the anoxic-oxic (AO) process by inserting a sludge holding tank (SHT) into the sludge return line forms an anoxic-oxic-settling-anaerobic (A+OSA) process that can achieve a 48.98% sludge reduction rate. The 454 pyrosequencing method was used to obtain the microbial communities of the AO and A+OSA processes. Results showed that the microbial community structures of the 2 processes were different as a result of the SHT insertion. Bacteria assigned to the phyla Proteobacteria and Bacteroidetes commonly existed and dominated the microbial populations of the 2 processes. However, the relative abundance of these populations shifted in the presence of SHT. The relative abundance of Proteobacteria decreased during the A+OSA process. A specific comparison at the class level showed that Sphingobacteria was enriched in the A+OSA process. The result suggested that the fermentative bacteria Sphingobacteria may have key functions in reducing the sludge from the A+OSA process. Uncultured Nitrosomonadaceae gradually became the dominant ammonia-oxidizing bacteria, and the nitrite-oxidizing bacterium Nitrospira was enriched in the A+OSA process. Both occurrences were favorable for stabilized nitrogen removal. The known denitrifying species in the A+OSA process were similar to those in the AO process; however, their relative abundance also decreased.

  10. Using biogenic sulfur gases as remotely detectable biosignatures on anoxic planets.

    Science.gov (United States)

    Domagal-Goldman, Shawn D; Meadows, Victoria S; Claire, Mark W; Kasting, James F

    2011-06-01

    We used one-dimensional photochemical and radiative transfer models to study the potential of organic sulfur compounds (CS(2), OCS, CH(3)SH, CH(3)SCH(3), and CH(3)S(2)CH(3)) to act as remotely detectable biosignatures in anoxic exoplanetary atmospheres. Concentrations of organic sulfur gases were predicted for various biogenic sulfur fluxes into anoxic atmospheres and were found to increase with decreasing UV fluxes. Dimethyl sulfide (CH(3)SCH(3), or DMS) and dimethyl disulfide (CH(3)S(2)CH(3), or DMDS) concentrations could increase to remotely detectable levels, but only in cases of extremely low UV fluxes, which may occur in the habitable zone of an inactive M dwarf. The most detectable feature of organic sulfur gases is an indirect one that results from an increase in ethane (C(2)H(6)) over that which would be predicted based on the planet's methane (CH(4)) concentration. Thus, a characterization mission could detect these organic sulfur gases-and therefore the life that produces them-if it could sufficiently quantify the ethane and methane in the exoplanet's atmosphere.

  11. Cross-regulation by CrcZ RNA controls anoxic biofilm formation in Pseudomonas aeruginosa

    Science.gov (United States)

    Pusic, Petra; Tata, Muralidhar; Wolfinger, Michael T.; Sonnleitner, Elisabeth; Häussler, Susanne; Bläsi, Udo

    2016-12-01

    Pseudomonas aeruginosa (PA) can thrive in anaerobic biofilms in the lungs of cystic fibrosis (CF) patients. Here, we show that CrcZ is the most abundant PA14 RNA bound to the global regulator Hfq in anoxic biofilms grown in cystic fibrosis sputum medium. Hfq was crucial for anoxic biofilm formation. This observation complied with an RNAseq based transcriptome analysis and follow up studies that implicated Hfq in regulation of a central step preceding denitrification. CrcZ is known to act as a decoy that sequesters Hfq during relief of carbon catabolite repression, which in turn alleviates Hfq-mediated translational repression of catabolic genes. We therefore inferred that CrcZ indirectly impacts on biofilm formation by competing for Hfq. This hypothesis was supported by the findings that over-production of CrcZ mirrored the biofilm phenotype of the hfq deletion mutant, and that deletion of the crcZ gene augmented biofilm formation. To our knowledge, this is the first example where competition for Hfq by CrcZ cross-regulates an Hfq-dependent physiological process unrelated to carbon metabolism.

  12. Anoxic depolarization of hippocampal astrocytes: possible modulation by P2X7 receptors.

    Science.gov (United States)

    Leichsenring, Anna; Riedel, Thomas; Qin, Ying; Rubini, Patrizia; Illes, Peter

    2013-01-01

    Current responses from CA1 neurons and stratum oriens astrocytes were recorded from hippocampal brain slices by means of the whole-cell patch-clamp technique. Anoxic depolarization (AD) was induced by an oxygen/glucose-deprived (OGD) medium also containing sodium iodoacetate and antimycin, in order to block glycolysis and oxidative phosphorylation, respectively. Anoxic depolarization has been reported to be due to the sudden increase of the extracellular K(+) concentration and the accompanying explosive rise in glutamate concentration. We asked ourselves whether the release of ATP activating P2X7 receptors is also involved in the AD. Although, the AD was evoked in absolute synchrony in neurons and astrocytes, and the NMDA receptor antagonistic AP-5 depressed these responses, neither the non-selective P2 receptor antagonist PPADS, nor the highly selective P2X7 receptor antagonist A438079 interfered with the AD or its delay time in neurons/astrocytes after inducing chemical hypoxia. However, A438079, but not PPADS increased in astrocytes the slow inward current observed in a hypoxic medium. It is concluded that ATP co-released with glutamate by hypoxic stimulation has only a minor function in the present brain slice system.

  13. Seasonal changes of magnetic minerals and their grain sizes in the Hiroshima Bay sediments

    Science.gov (United States)

    Kawamura, N.; Ishikawa, N.

    2011-12-01

    Frequent outbreaks of red tide have been reported since 1970 in the Hiroshima bay, and the red tide is caused by a bloom of dinoflagellates. Iron is an essential element for dinoflagellates, and is supplied as bivalent or trivalent ions and iron compounds from lands to sea. For damage predictions of red tide, it is important to research the distribution of iron in the bay. The acidification of seawater during summer has been also observed in the Hiroshima Bay. Increase of CO2 concentration and decrease of dissolved oxygen (DO) content in seawater cause an anoxic condition in the bay. It is known that iron oxides are dissolved and sulfides are formed in an anoxic condition. For clarifying variations of the distribution and mode of iron in sediments and bottom water in the Hiroshima Bay, we investigated kinds of iron compounds in the sediments and the amount of dissolved iron in the bottom waters. Sediment cores of 5cm in depth were taken at three sites in the Hiroshima Bay by using a multiple corer and crab sampler. Data of oceanographic observations at these sites showed that the temperature of the bottom water increased, whereas DO and pH values decreased during the sampling period. The sediment samples were composed of clayey silt. We measured dissolved iron concentration in interstitial and bottom waters filtered above 0.45 um grains, and performed magnetic hysteresis measurements and high temperature magnetometry on the sediment samples. The presence of magnetite (Fe3O4) and hematite (Fe2O3) were recognized in all analyzed samples, whereas greigite (Fe3S4) appeared at these sites with an anoxic condition in the bottom water. Magnetic grain size increased from June to August, while iron concentration increased in the bottom waters. It is suggested that magnetite and hematite were dissolved and greigite was formed, associated with the proceeding of the anoxic condition, and that the grain-size of magnetic minerals and the iron concentration of the bottom water

  14. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model

    Science.gov (United States)

    Stelzer, Robert S.; Bartsch, Lynn

    2012-01-01

    Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher, on average, in shallower core sections. However, core sections deeper than 5 cm accounted for 70%, on average, of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L but the relationship broke down at higher concentrations (> 5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates

  15. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model

    Science.gov (United States)

    Stelzer, Robert S.; Bartsch, Lynn A.

    2012-06-01

    Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher on average in shallower core sections. However, core sections deeper than 5 cm accounted for 70% on average of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L, but the relationship broke down at higher concentrations (>5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates can

  16. Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations

    Science.gov (United States)

    Ameen, Nawrass

    2013-04-01

    This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hradčany, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified

  17. Exploring Microbial Life in Oxic Sediments Underlying Oligotrophic Ocean Gyres

    Science.gov (United States)

    Ziebis, W.; Orcutt, B.; Wankel, S. D.; D'Hondt, S.; Szubin, R.; Kim, J. N.; Zengler, K.

    2015-12-01

    Oxygen, carbon and nutrient availability are defining parameters for microbial life. In contrast to organic-rich sediments of the continental margins, where high respiration rates lead to a depletion of O2 within a thin layer at the sediment surface, it was discovered that O2 penetrates several tens of meters into organic-poor sediments underlying oligotrophic ocean gyres. In addition, nitrate, another important oxidant, which usually disappears rapidly with depth in anoxic sediments, tends to accumulate above seawater concentrations in the oxic subsurface, reflecting the importance of nitrogen cycling processes, including both nitrification and denitrification. Two IODP drilling expeditions were vital for exploring the nature of the deep subsurface beneath oligotrophic ocean gyres, expedition 329 to the South Pacific Gyre (SPG) and expedition 336 to North Pond, located on the western flank of the Mid-Atlantic ridge beneath the North Atlantic Gyre. Within the ultra-oligotrophic SPG O2 penetrates the entire sediment column from the sediment-water interface to the underlying basement to depths of > 75 m. At North Pond, a topographic depression filled with sediment and surrounded by steep basaltic outcrops, O2 penetrates deeply into the sediment (~ 30 m) until it eventually becomes depleted. O2 also diffuses upward into the sediment from seawater circulating within the young crust underlying the sediment, resulting in a deep oxic layer several meters above the basalt. Despite low organic carbon contents microbial cells persist throughout the entire sediment column within the SPG (> 75 m) and at North Pond, albeit at low abundances. We explored the nature of the subsurface microbial communities by extracting intact cells from large volumes of sediment obtained from drill cores of the two expeditions. By using CARD-FiSH, amplicon (16s rRNA) and metagenome sequencing we shed light on the phylogenetic and functional diversity of the elusive communities residing in the

  18. Interstitial brines in playa sediments

    Science.gov (United States)

    Jones, B.F.; Van Denburgh, A.S.; Truesdell, A.H.; Rettig, S.L.

    1969-01-01

    Study of several closed drainages in the Great Basin has shown that the interstitial solutions of shallow, fine-grained playa deposits store a large quantity of dissolved solids and are often more concentrated than associated lakes and ponds, except in peripheral zones of stream or ground-water inflow. These interstitial fluids, when compared with local runoff, impoundments, or spring waters, commonly have a distinctive ionic composition which sometimes cannot be explained by either simple mixing of surface and subsurface inflow or by evaporative concentration. At Abert Lake, Oregon, the interstitial solute concentrations increased with depth to values as much as five times greater than the lake, except where springs indicate significant ground-water input. Where Na+, Cl, and CO2 species constitute more than 90% of the solutes, Na+ Cl- ratios in the lake water are lower than in interstitial solutions of bottom cores and higher than in playa fluids. At the same time, Na+ K+ ratios are highest in the fluids of lake bottom muds and lowest in playa interstitials. In deeper playa profiles, interstitial Na+ Cl- tended to decrease with depth (5 ft. maximum). In the Abert Lake area, as in other parts of the western Great Basin, Na+ Cl- ratios are indicative of total CO2 in solution and the effects of organic decay in surficial sediments. These ratios, coupled with data on silica and bulk density, show that higher PCO2 accompanying decay promotes silicate dissolution and hydrogen ion exchange, stripping alkalis from sediment which had preferentially adsorbed K+ when entering the lake. On subsequent loss of pore fluid in the playa regime, silica initially released to solution in the lake environment is readsorbed on dissolution products. ?? 1969.

  19. Biological Phosphorus Release and Uptake Under Alternating Anaerobic and Anoxic Conditions In a Fixed-Film Reactor

    DEFF Research Database (Denmark)

    Kerrn-Jespersen, Jens Peter; Henze, Mogens; Strube, Rune

    1994-01-01

    Biological phosphorus removal was investigated in a fixed-film reactor with alternating anaerobic and anoxic conditions. The tests showed that biological phosphorus removal can be obtained in a fixed-film reactor with nitrate as oxidising agent. In the anaerobic period, 0.52 mg of PO4-P...... potassium taken up and phosphate taken up in the anoxic phase was determined to be 0.36 mg K/mg P. The phosphorus concentration in the sludge was determined at 8–10% of dry solids....

  20. Arsenic in Bangladesh Groundwater: Where it Comes From and why

    Science.gov (United States)

    Zheng, Y.; van Geen, A.; Stute, M.; Dhar, R.; Mo, Z.; Cheng, Z.; Horneman, A.; Simpson, H. J.; Gavrieli, I.; Ahmed, K. M.

    2002-12-01

    Arsenic (As) is a highly toxic, ubiquitous metalloid and realization is growing that water-borne As now poses a significant threat to human and ecosystem health worldwide. Elevated concentrations of As in groundwater have emerged as a major health threat in the Ganges-Brahmaputra Delta region where tens of millions of people are exposed to [As] 10 to 100 times higher than the drinking water standard of 10 μg/L recommended by the WHO. Extensive sampling by the British Geological Survey has shown that water from shallow aquifers with recent alluvial sediments carries distinctly higher [As] than does water from deeper aquifers with presumed pre-Holocene sediments. However, the reasons why such a large contrast in [As] exists between younger, Holocene aquifers and older, Pleistocene aquifers are not well understood. Furthermore, although As is generally believed to be of natural origin and is mobilized in reducing groundwater, the sources of particle phase As and mechanisms of arsenic release to groundwater remain poorly understood. Hydrological and geochemical factors contributing to elevated arsenic concentrations (up to 800 μg/L) in the shallow aquifers and much lower [As](Bangladesh. Araihazar is on the margin of the Holocene Mehgna fluvial floodplain where the transition occurs from the uplifted mid Pleistocene Madhupur tract to much younger, incised Meghna river channel deposits from west to east. Coring confirmed that the aquifers were separated by a multiple-layered silt/clay section. At least at one site, radiocarbon dating of peat layers within the silt/clay section suggests that a Holocene aquifer is unconformably overlying a Pleistocene sequence. Based on radiocarbon and tritium dating, the residence time of groundwater in the high-As shallow, Holocene aquifers (4 - 30 m) is years to decades, much less than that of the low-As deep aquifer (50- 100 m), which is a thousand to tens of thousands of years. This hydrological separation is important in

  1. Nitrate bioreduction in redox-variable low permeability sediments

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Sen [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Liu, Yuanyuan [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Liu, Chongxuan, E-mail: chongxuan.liu@pnnl.gov [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Shi, Liang; Shang, Jianying [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Shan, Huimei [China University of Geosciences, Wuhan 430074 (China); Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Zachara, John; Fredrickson, Jim; Kennedy, David; Resch, Charles T.; Thompson, Christopher; Fansler, Sarah [Pacific Northwest National Laboratory, Richland, WA 99354 (United States)

    2016-01-01

    Low permeability zone (LPZ) can play an important role as a sink or secondary source in contaminant transport in groundwater system. This study investigated the rate and end product of nitrate bioreduction in LPZ sediments. The sediments were from the U.S. Department of Energy's Hanford Site, where nitrate is a groundwater contaminant as a by-product of radionuclide waste discharges. The LPZ at the Hanford site consists of two layers with an oxidized layer on top and reduced layer below. The oxidized layer is directly in contact with the overlying contaminated aquifer, while the reduced layer is in contact with an uncontaminated aquifer below. The experimental results showed that nitrate bioreduction rate and end-product differed significantly in the sediments. The bioreduction rate in the oxidized sediment was significantly faster than that in the reduced one. A significant amount of N{sub 2}O was accumulated in the reduced sediment; while in the oxidized sediment, N{sub 2}O was further reduced to N{sub 2}. RT-PCR analysis revealed that nosZ, the gene that codes for N{sub 2}O reductase, was below detection limit in the reduced sediment. Batch experiments and kinetic modeling were performed to provide insights into the role of organic carbon bioavailability, biomass growth, and competition between nitrate and its reducing products for electrons from electron donors. The results revealed that it is important to consider sediment redox conditions and functional genes in understanding and modeling nitrate bioreduction in subsurface sediments. The results also implied that LPZ sediments can be important sink of nitrate and a potential secondary source of N{sub 2}O as a nitrate bioreduction product in groundwater. - Highlights: • Low permeability zones (LPZ) can microbially remove nitrate in groundwater. • The rate and end product of nitrate bioreduction vary within LPZ. • Greenhouse gas N{sub 2}O can be the end product of nitrate bioreduction in LPZ.

  2. Effects of temperature changes on groundwater ecosystems

    Science.gov (United States)

    Griebler, Christian; Kellermann, Claudia; Schreglmann, Kathrin; Lueders, Tillmann; Brielmann, Heike; Schmidt, Susanne; Kuntz, David; Walker-Hertkorn, Simone

    2014-05-01

    The use of groundwater as a carrier of thermal energy is becoming more and more important as a sustainable source of heating and cooling. At the same time, the present understanding of the effects of aquifer thermal usage on geochemical and biological aquifer ecosystem functions is extremely limited. Recently we started to assess the effects of temperature changes in groundwater on the ecological integrity of aquifers. In a field study, we have monitored hydrogeochemical, microbial, and faunal parameters in groundwater of an oligotrophic aquifer in the vicinity of an active thermal discharge facility. The observed seasonal variability of abiotic and biotic parameters between wells was considerable. Yet, due to the energy-limited conditions no significant temperature impacts on bacterial or faunal abundances and on bacterial productivity were observed. In contrast, the diversity of aquifer bacterial communities and invertebrate fauna was either positively or negatively affected by temperature, respectively. In follow-up laboratory experiments temperature effects were systematically evaluated with respect to energy limitation (e.g. establishment of unlimited growth conditions), geochemistry (e.g. dynamics of DOC and nutrients), microbiology (e.g. survival of pathogens), and fauna (temperature preference and tolerance). First, with increased nutrient and organic carbon concentrations even small temperature changes revealed microbiological dynamics. Second, considerable amounts of adsorbed DOC were mobilized from sediments of different origin with an increase in temperatures. No evidence was obtained for growth of pathogenic bacteria and extended survival of viruses at elevated temperatures. Invertebrates clearly preferred natural thermal conditions (10-12°C), where their highest frequency of appearance was measured in a temperature gradient. Short-term incubations (48h) of invertebrates in temperature dose-response tests resulted in LT50 (lethal temperature) values

  3. A2O工艺缺氧生物磷去除%Anoxic Biological Phosphorus Uptake in A2O Process

    Institute of Scientific and Technical Information of China (English)

    王晓莲; 王淑莹; 彭永臻

    2005-01-01

    A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen (92.3%, 95.5%, 96% and 79.5%, respectively) could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation.

  4. Heterogeneous oxygenation states in the Atlantic and Tethys oceans during Oceanic Anoxic Event 2

    Science.gov (United States)

    Westermann, Stéphane; Vance, Derek; Cameron, Vyllinniskii; Archer, Corey; Robinson, Stuart A.

    2014-10-01

    The Cenomanian-Turonian boundary (ca. 93.5 Ma) is marked by an episode of profound environmental change, including a major perturbation of the carbon cycle and an Oceanic Anoxic Event (OAE-2). Here, we present molybdenum (Mo) isotope variations within the OAE-2 interval for four sections from the western Tethys (Furlo and La Contessa) and the North-Atlantic (ODP site 1276 and DSDP site 367). The main target of this study is to investigate the extent of reducing conditions (truly global in extent or restricted to poorly-ventilated restricted deep basins), with particular reference to the relationship between the change in the oxygenation state of the ocean and the link to global perturbations of the carbon cycle recorded in carbon isotopes. All four sections show fluctuations in the redox sensitive trace metal (RSTE) distribution, suggesting rapid variations in local redox conditions, ranging from anoxic to euxinic. The RSTE enrichment factors (EFs) also suggest different depositional conditions and paleoceanographic processes in the western Tethys versus the North Atlantic. Whereas the North Atlantic sites show evidence of weak watermass restriction associated with the action of a particulate shuttle within the water column, the EFs of the Tethyan sections are characteristic of unrestricted marine systems. Mo isotopes show surprisingly negative values through the Tethyan sections. At the onset of OAE-2, an increasing trend in δMo98 is observed, with values ranging from -0.6 to 0.6‰. During the second half of OAE-2, the δMo98 curve shows a progressive shift towards more negative values. In the North Atlantic, δMo98 signatures from ODP site 1276 show a similar behaviour as observed in the western Tethys. At DSDP site 367, Mo isotopes are generally heavier during OAE-2, fluctuating around an average value of 1.1‰. This is consistent with fully euxinic conditions and the black shales deposited may have recorded the seawater signature during OAE-2. The Mo isotope

  5. Metabolic Strategies in Energy-Limited Microbial Communities in the Anoxic Subsurface (Frasassi Cave System, Italy)

    Science.gov (United States)

    McCauley, R. L.; Jones, D. S.; Schaperdoth, I.; Steinberg, L.; Macalady, J. L.

    2010-12-01

    Two major sources of energy, light and chemical potential, are available to microorganisms. However, energy is not always abundant and is often a limiting factor in microbial survival and replication. The anoxic, terrestrial subsurface offers a unique opportunity to study microorganisms and their potentially novel metabolic strategies that are relevant for understanding biogeochemistry and biosignatures as related to the non-photosynthetic, energy-limited environments on the modern and ancient Earth and elsewhere in the solar system. Geochemical data collected in a remote stratified lake 600 m below ground surface in the sulfidic Frasassi cave system (Italy) suggest that little redox energy is available for life, consistent with low signal from domain-specific FISH probes. The carbon isotope signatures of biofilms (-33‰) and DIC (-9‰) in the anoxic water suggest in situ production by lithoautotrophs using RuBisCO. 16S rDNA libraries constructed from the biofilm are dominated by diverse sulfate reducing bacteria. The remaining bacterial and archaeal clones affiliate with more than 11 major uncultivated or novel prokaryotic lineages. Diverse dsrAB gene sequences are consistent with high sulfate concentrations and undetectable or extremely low oxygen, nitrate, and iron concentrations. However, the electron donor for sulfate reduction is unclear. Methane is detectable in the anoxic water although no 16S rDNA sequences associated with known methanogens or anaerobic methane oxidizers were retrieved. mcrA gene sequences retrieved from the biofilm by cloning are not related to cultivated methanogens or to known anaerobic methane oxidizers. Non-purgable organic carbon (NPOC) is below detection limits (i.e. <42 μM acetate) suggesting that alternative electron donors or novel metabolisms may be important. A sample collected by cave divers in October 2009 was pyrosequenced at the Pennsylvania State University Genomics Core Facility using Titanium chemistry (454 Life

  6. Role of diatoms in the spatial-temporal distribution of intracellular nitrate in intertidal sediment.

    Directory of Open Access Journals (Sweden)

    Peter Stief

    Full Text Available Intracellular nitrate storage allows microorganisms to survive fluctuating nutrient availability and anoxic conditions in aquatic ecosystems. Here we show that diatoms, ubiquitous and highly abundant microalgae, represent major cellular reservoirs of nitrate in an intertidal flat of the German Wadden Sea and are potentially involved in anaerobic nitrate respiration. Intracellular nitrate (ICNO3 was present year-round in the sediment and was spatially and temporally correlated with fucoxanthin, the marker photopigment of diatoms. Pyrosequencing of SSU rRNA genes of all domains of life confirmed that ICNO3 storage was most likely due to diatoms rather than other known nitrate-storing microorganisms (i.e., large sulfur bacteria and the eukaryotic foraminifers and gromiids. Sedimentary ICNO3 concentrations reached up to 22.3 µmol dm(-3 at the sediment surface and decreased with sediment depth to negligible concentrations below 5 cm. Similarly, the ICNO3/fucoxanthin ratio and porewater nitrate (PWNO3 concentrations decreased with sediment depth, suggesting that ICNO3 of diatoms is in equilibrium with PWNO3, but is enriched relative to PWNO3 by 2-3 orders of magnitude. Cell-volume-specific ICNO3 concentrations in a diatom mat covering the sediment surface during spring were estimated at 9.3-46.7 mmol L(-1. Retrieval of 18S rRNA gene sequences related to known nitrate-storing and nitrate-ammonifying diatom species suggested that diatoms in dark and anoxic sediment layers might be involved in anaerobic nitrate respiration. Due to the widespread dominance of diatoms in microphytobenthos, the total nitrate pool in coastal marine sediments may generally be at least two times larger than derived from porewater measurements and partially be recycled to ammonium.

  7. Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic

    Science.gov (United States)

    Dando, P. R.; Southward, A. J.; Southward, E. C.; Lamont, P.; Harvey, R.

    2008-08-01

    The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000-2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide 'mining', a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.

  8. Influence of upwelling saline groundwater on iron and manganese cycling in the Rio Grande floodplain aquifer

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, Matthew F. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States)], E-mail: matthew.f.kirk@gmail.com; Crossey, Laura J. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Takacs-Vesbach, Cristina [Department of Biology, University of New Mexico, Albuquerque, NM 87131 (United States); Newell, Dennis L. [Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 (United States); Bowman, Robert S. [Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801 (United States)

    2009-03-15

    Salinity contributions from upwelling groundwater significantly degrade water quality in the Rio Grande, a major source of water for the southwestern USA. This study considers the influence of this upwelling water on the geochemistry and microbiology of the Rio Grande floodplain alluvial aquifer. The composition of surface water, groundwater, and floodplain sediment samples collected from three transects in the Socorro Basin was examined. Terminal-restriction fragment length polymorphism (T-RFLP) was also used to examine microbial biomass samples. The distribution of salinity in the floodplain groundwater largely reflects the configuration of local groundwater flow and mixing of two major water sources, deeply-sourced saline groundwater and river water. Microbial populations in the shallow aquifer consume O{sub 2} and NO{sub 3}{sup -} and serve to redistribute metal oxides from the saturated zone to locations of groundwater discharge at the surface and possibly near the water table. The upwelling saline groundwater affects floodplain microbial processes by transporting reduced metals and organic electron donors to the alluvial aquifer system. This enhances metal reduction in the saturated zone and ultimately metal oxidation at or near the surface. Geochemical modeling suggests that mixing of the saline groundwater with more dilute water in the floodplain creates conditions more favorable for metal oxidation to occur and thereby influences the distribution of metal oxides.

  9. Predicting geogenic arsenic contamination in shallow groundwater of south Louisiana, United States.

    Science.gov (United States)

    Yang, Ningfang; Winkel, Lenny H E; Johannesson, Karen H

    2014-05-20

    Groundwater contaminated with arsenic (As) threatens the health of more than 140 million people worldwide. Previous studies indicate that geology and sedimentary depositional environments are important factors controlling groundwater As contamination. The Mississippi River delta has broadly similar geology and sedimentary depositional environments to the large deltas in South and Southeast Asia, which are severely affected by geogenic As contamination and therefore may also be vulnerable to groundwater As contamination. In this study, logistic regression is used to develop a probability model based on surface hydrology, soil properties, geology, and sedimentary depositional environments. The model is calibrated using 3286 aggregated and binary-coded groundwater As concentration measurements from Bangladesh and verified using 78 As measurements from south Louisiana. The model's predictions are in good agreement with the known spatial distribution of groundwater As contamination of Bangladesh, and the predictions also indicate high risk of As contamination in shallow groundwater from Holocene sediments of south Louisiana. Furthermore, the model correctly predicted 79% of the existing shallow groundwater As measurements in the study region, indicating good performance of the model in predicting groundwater As contamination in shallow aquifers of south Louisiana.

  10. Hanford Site groundwater monitoring for Fiscal Year 1997

    Energy Technology Data Exchange (ETDEWEB)

    Hartman, M.J.; Dresel, P.E. [eds.] [and others

    1998-02-01

    This report presents the results of groundwater and vadose-zone monitoring for fiscal year (FY) 1997 on the Hanford Site, Washington. Soil-vapor extraction continued in the 200-West Area to remove carbon tetrachloride from the vadose zone. Characterization and monitoring of the vadose zone comprised primarily spectral gamma logging, soil-vapor monitoring, and analysis and characterization of sediments sampled below a vadose-zone monitoring well. Source-term analyses for strontium-90 in 100-N Area vadose-zone sediments were performed using recent groundwater-monitoring data and knowledge of strontium`s ion-exchange properties. Water-level monitoring was performed to evaluate groundwater-flow directions, to track changes in water levels, and to relate such changes to evolving disposal practices. Water levels over most of the Hanford Site continued to decline between June 1996 and June 1997. Water levels near the Columbia River increased during this period because the river stage was unusually high. Groundwater chemistry was monitored to track the extent of contamination, to note trends, and to identify emerging groundwater-quality problems. The most widespread radiological contaminant plumes were tritium and iodine-129. Concentrations of technetium-99, uranium, strontium-90, and carbon-14 also exceeded drinking water standards in smaller plumes. Plutonium and cesium-137 exceeded standards only near the 216-B-5 injection well. Derived concentration guide levels specified in U.S. Department of Energy Order 5400.5 were exceeded for tritium, uranium, strontium-90, and plutonium in small plumes or single wells. Nitrate is the most extensive chemical contaminant. Carbon tetrachloride, chloroform, chromium, cis-1,2-dichloroethylene, fluoride, and trichloroethylene also were present in smaller areas at levels above their maximum contaminant levels. Cyanide concentrations were elevated in one area but were below the maximum contaminant level.

  11. Groundwater hydrology instructional system

    Science.gov (United States)

    Schmidt, Ronald G.

    Wright State University, Dayton, Ohio, is preparing for its third cycle of the Interactive Remote Instructional System (IRIS) in groundwater hydrology, beginning January 15, 1986. The first cycle finished with an impressive completion ratio for registered participants, and the second cycle has currently been underway since July. This comprehensive hydrogeology program was originally developed for the Soil Conservation Service (of the U.S. Department of Agriculture) to prepare their personnel for professional practice work. Since its evolution into IRIS, an 80% participant completion rate has been recorded for the first cycle, which is a significant departure from success rates traditionally recorded by correspondence courses. This excellent rate of success is the result of 2 years of refinement and demonstrates the progressive nature of the program. IRIS has met the needs of participants by developing a curriculum that reflects current trends in the groundwater industry and has provided a unique educational approach that ensures maximum interaction between the instructional staff and participants.

  12. Bridging the Faraoni and Selli oceanic anoxic events: short and repetitive dys- and anaerobic episodes during the late Hauterivian to early Aptian in the central Tethys

    Science.gov (United States)

    Föllmi, K. B.; Bôle, M.; Jammet, N.; Froidevaux, P.; Godet, A.; Bodin, S.; Adatte, T.; Matera, V.; Fleitmann, D.; Spangenberg, J. E.

    2011-06-01

    A detailed stratigraphical and geochemical analysis was performed on the upper part of the Maiolica Formation outcropping in the Breggia (southern Switzerland) and Capriolo sections (northern Italy). In these localities, the Maiolica Formation consists of well-bedded, partly siliceous, pelagic, micritic carbonate, which lodges numerous thin, dark and organic-rich layers. Stable-isotope, phosphorus, organic-carbon and a suite of redox-sensitive trace-metal contents (RSTE: Mo, U, Co, V and As) were measured. Higher densities of organic-rich layers were identified in the uppermost Hauterivian, lower Barremian and the Barremian-Aptian boundary intervals, whereas the upper Barremian interval and the interval immediately following the Barremian-Aptian boundary interval are characterized by lower densities of organic-rich layers. TOC contents, RSTE pattern and Corg:Ptot ratios indicate that most layers were deposited under dysaerobic rather than anaerobic conditions and that latter conditions were likely restricted to short intervals in the latest Hauterivian, the early Barremian and the pre-Selli early Aptian. Correlations are possible with organic-rich intervals in central Italy (the Gorgo a Cerbara section) and the Boreal northwest German Basin, and with the facies and drowning pattern in the evolution of the Helvetic segment of the northern Tethyan carbonate platform. Our data and correlations suggest that the latest Hauterivian witnessed the progressive installation of dysaerobic conditions in the Tethys, which went along with the onset in sediment condensation, phosphogenesis and platform drowning on the northern Tethyan margin, and which culminated in the Faraoni anoxic episode. This brief episode is followed by further episodes of dysaerobic conditions in the Tethys and the northwest German Basin, which became more frequent and progressively stronger in the late early Barremian. Platform drowning persisted and did not halt before the latest early Barremian. The

  13. Contain contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Mutch, R.D. Jr.; Caputi, J.R. [Eckenfelder, Inc., Mahwah, NJ (United States); Ash, R.E. IV [Eckenfelder Inc., Nashville, TN (United States)

    1997-05-01

    Despite recent progress in innovative treatment technologies, many problems with contaminated groundwater still require the use of barrier walls, typically in combination with extraction and treatment systems. New technologies for subsurface barrier walls, mostly based on geomembranes, advancements in self-hardening slurries and permeation grouts with materials such as colloidal silica gel and montan wax emulsions, are being developed at an unprecedented pace. The paper discusses deep soil mixing, jet grouting, slurry trenches, and permeation grouting.

  14. Naturally occurring arsenic in the groundwater at the Kansas City Plant

    Energy Technology Data Exchange (ETDEWEB)

    Korte, N.E.

    1990-12-01

    This report describes an investigation concerning the presence of arsenic in concentrations exceeding 0.4 mg/L in the groundwater under the Department of Energy's Kansas City Plant (KCP). The study consisted of four distinct phases: a thorough review of the technical literature, a historical survey of arsenic use at the facility, a laboratory study of existing techniques for determining arsenic speciation, and a field program including water, soil, and sediment sampling. The historical survey and literature review demonstrated that plant activities had not released significant quantities of arsenic to the environment but that similar occurrences of arsenic in alluvial groundwater are widespread in the midwestern United States. Laboratory studies showed that a chromatographic separation technique was necessary to accurately determine arsenic speciation for the KCP groundwater samples. Field studies revealed that naturally occurring reducing conditions prevalent in the subsurface are responsible for dissolving arsenic previously sorbed by iron oxides. Indeed, the data demonstrated that the bulk arsenic concentration of site subsoils and sediments is {approximately}7 mg/kg, whereas the arsenic content of iron oxide subsamples is as high as 84 mg/kg. Literature showed that similar concentrations of arsenic in sediments occur naturally and are capable of producing the levels of arsenic found in groundwater monitoring wells at the KCP. The study concludes, therefore, that the arsenic present in the KCP groundwater is the result of natural phenomena. 44 refs., 8 figs., 14 tabs.

  15. Leaching of UO2 pellets doped with alpha-emitters (238/239Pu) in synthetic deep Callovian-Oxfordian groundwater

    Science.gov (United States)

    Tribet, M.; Jégou, C.; Broudic, V.; Marques, C.; Rigaux, P.; Gavazzi, A.

    2010-03-01

    The reactivity of a polycrystalline UO2 surface under alpha irradiation in contact with groundwater is investigated, in the hypothesis of direct disposal of spent fuel in a deep geological repository. Two series of plutonium-doped UO2 samples (specific alpha activity of 18 and 385 MBq·g-1UO2) were leached in a synthetic Callovian-Oxfordian deep groundwater under anoxic conditions (Ar/CO2 3000 ppm, 3.5 bar relative pressure) to assess both the impact of alpha radiolysis of water and the complexing capacity of the groundwater ions on the dissolution of UO2. This study follows a prior one performed in pure and carbonated waters. Firstly, technical developments were necessary for the analyses in the groundwater solution because of its high salt concentrations: quantification limits were determined for the measurement of uranium and radiolytic H2O2 traces in this medium. Secondly, given the very high reactivity of these samples in the presence of air and in order to minimize any prior surface oxidation, a strict experimental protocol was followed, based on high-temperature annealing in Ar + 4% H2 with preleaching cycles. Each type of UO2 pellet was then leached under static conditions for 30 days (anoxic conditions, deep groundwater solutions). Results on the evolution of uranium releases are presented. For the lowest alpha activity (18 MBq·g-1UO2), uranium releases in groundwater were below the quantification limit of 2 × 10-8 mol·L-1 with a kinetic phosphorescence analyzer, even after 30 days. However, for higher alpha activity (385 MBq·g-1UO2) the uranium releases begin to exceed the quantification limit after 14 days of leaching and then increase exponentially. This increase is comparable to results previously obtained in carbonated solutions.

  16. An Updated View of the Microbial Diversity in Deep Hypersaline Anoxic Basins

    KAUST Repository

    Mapelli, Francesca

    2017-03-02

    Deep hypersaline anoxic basins (DHABs) are marine extreme habitats, firstly discovered in the 1970s of the last century, located in several oceanographic regions, including the Mediterranean and Red Sea and the Gulf of Mexico. These basins are filled with brines that do not mix with the overlying seawater, due to a density difference. Brine and seawater result separated by a thick interface acting as a trap for particulate and cells. Some microbiological studies focused on seawater-brine interfaces of DHABs, showing that microbial populations are differentially distributed according to the gradient of salinity, oxygen, and nutrients occurring in such transition zones. Moreover, DHABs’ brines were intensively studied showing that specific bacterial, archaeal, and eukaryotic populations thrive there. In the last few years, cultivation and “omics”-based approaches have been used with samples collected from DHABs around the world, allowing clarifying metabolic processes of paramount ecological importance and pointing out the high biotechnological potential of the inhabiting extremophiles.

  17. Photocatalytic decomposition of humic acids in anoxic aqueous solutions producing hydrogen, oxygen and light hydrocarbons.

    Science.gov (United States)

    Klauson, Deniss; Budarnaja, Olga; Beltran, Ignacio Castellanos; Krichevskaya, Marina; Preis, Sergei

    2014-01-01

    Photocatalytic water splitting for hydrogen and oxygen production requires sacrificial electron donors, for example, organic compounds. Titanium dioxide catalysts doped with platinum, cobalt, tungsten, copper and iron were experimentally tested for the production of hydrogen, oxygen and low molecular weight hydrocarbons from aqueous solutions of humic substances (HS). Platinum-doped catalyst showed the best results in hydrogen generation, also producing methane, ethene and ethane, whereas the best oxygen production was exhibited by P25, followed by copper--and cobalt-containing photocatalysts. Iron-containing photocatalyst produced carbon monoxide as a major product. HS undergoing anoxic photocatalytic degradation produce hydrogen with minor hydrocarbons, and/or oxygen. It appears that better hydrogen yield is achieved when direct HS splitting takes place, as opposed to HS acting as electron donors for water splitting.

  18. Microbiology of the Red Sea (and other) deep-sea anoxic brine lakes

    KAUST Repository

    Antunes, Andre

    2011-05-30

    Summary: The Red Sea harbours approximately 25 deep-sea anoxic brine pools. They constitute extremely unique and complex habitats with the conjugation of several extreme physicochemical parameters rendering them some of the most inhospitable environments on Earth. After 50 years of research mostly driven by chemists, geophysicists and geologists, the microbiology of the brines has been receiving increased interest in the last decade. Recent molecular and cultivation-based studies have provided us with a first glimpse on the enormous biodiversity of the local microbial communities, the identification of several new taxonomic groups, and the isolation of novel extremophiles that thrive in these environments. This review presents a general overview of these unusual biotopes and compares them with other similar environments in the Mediterranean Sea and the Gulf of Mexico, with a focus on their microbial ecology. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  19. Vasoactivity of hydrogen sulfide in normoxic and anoxic turtles (Trachemys scripta)

    DEFF Research Database (Denmark)

    Stecyk, Jonathan A.W.; Jensen, Nini Skovgaard; Nilsson, Göran E.;

    2010-01-01

    Systemic vascular resistance (Rsys) of freshwater turtles increases substantially during anoxia, but the underlying mechanisms are not fully understood. We investigated whether hydrogen sulfide (H2S), an endogenously produced metabolite believed to be an O2 sensor/transducer of vasomotor tone......, contributes to the increased Rsys of anoxic red-eared slider turtles (Trachemys scripta). Vascular infusion of the H2S donor NaHS in anesthetized turtles at 21°C and fully recovered normoxic turtles at 5°C and 21°C revealed H2S to be a potent vasoconstrictor of the systemic circulation. Likewise, wire...... myography of isolated turtle mesenteric and pulmonary arteries demonstrated H2S to mediate an anoxia-induced constriction. Intriguingly, however, NaHS did not exert vasoconstrictory effects during anoxia (6 h at 21°C; 14 days at 5°C) when plasma H2S concentration, estimated from the colorimetric measurement...

  20. Glial Hsp70 Protects K+ Homeostasis in the Drosophila Brain during Repetitive Anoxic Depolarization

    Science.gov (United States)

    Armstrong, Gary A. B.; Xiao, Chengfeng; Krill, Jennifer L.; Seroude, Laurent; Dawson-Scully, Ken; Robertson, R. Meldrum

    2011-01-01

    Neural tissue is particularly vulnerable to metabolic stress and loss of ion homeostasis. Repetitive stress generally leads to more permanent dysfunction but the mechanisms underlying this progression are poorly understood. We investigated the effects of energetic compromise in Drosophila by targeting the Na+/K+-ATPase. Acute ouabain treatment of intact flies resulted in subsequent repetitive comas that led to death and were associated with transient loss of K+ homeostasis in the brain. Heat shock pre-conditioned flies were resistant to ouabain treatment. To control the timing of repeated loss of ion homeostasis we subjected flies to repetitive anoxia while recording extracellular [K+] in the brain. We show that targeted expression of the chaperone protein Hsp70 in glial cells delays a permanent loss of ion homeostasis associated with repetitive anoxic stress and suggest that this is a useful model for investigating molecular mechanisms of neuroprotection. PMID:22174942

  1. Glial Hsp70 protects K+ homeostasis in the Drosophila brain during repetitive anoxic depolarization.

    Directory of Open Access Journals (Sweden)

    Gary A B Armstrong

    Full Text Available Neural tissue is particularly vulnerable to metabolic stress and loss of ion homeostasis. Repetitive stress generally leads to more permanent dysfunction but the mechanisms underlying this progression are poorly understood. We investigated the effects of energetic compromise in Drosophila by targeting the Na(+/K(+-ATPase. Acute ouabain treatment of intact flies resulted in subsequent repetitive comas that led to death and were associated with transient loss of K(+ homeostasis in the brain. Heat shock pre-conditioned flies were resistant to ouabain treatment. To control the timing of repeated loss of ion homeostasis we subjected flies to repetitive anoxia while recording extracellular [K(+] in the brain. We show that targeted expression of the chaperone protein Hsp70 in glial cells delays a permanent loss of ion homeostasis associated with repetitive anoxic stress and suggest that this is a useful model for investigating molecular mechanisms of neuroprotection.

  2. Reduction of Biological Sludge Production Applying an Alternating Oxic/anoxic Process in Water Line.

    Science.gov (United States)

    Eusebi, Anna Laura; Panigutti, Maximiliano; Battistoni, Paolo

    2016-06-01

    Alternating oxic/anoxic process, applied for the main objective of the improvement of nitrogen performances, was studied in terms of secondary effect of biomass reduction. The process was carried out in one real water resource recovery facility and the data were compared with the previous conventional period when a conventional process was adopted. The main mechanism of the process for the sludge minimization is recognized in the metabolic uncoupling. In fact, an increase of the specific oxygen uptake rate in the biological reactor was recorded stimulated by the change of the oxidation reduction potential environment. Moreover, the heterotrophic growth yield was measured equal to 0.385 kgVSS/kgCOD. The global percentage of reduction was tested with the mass balance of solids. The process is able to decrease the observed sludge yield up to 20%. The specific energy consumption was evaluated.

  3. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    Science.gov (United States)

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b.

  4. Microbial pathways for the mobilization of mercury as Hg(O) in anoxic subsurface environments

    Energy Technology Data Exchange (ETDEWEB)

    Barkay, Tamar

    2005-06-01

    The goal of our project which was initiated in June 2005 is focused on the presence of merA in microbial communities of anoxic environments and the effect of anaerobic respiratory pathways on MR expression and activities. The following progress has been made to date: PCR primers were designed to span the known phylogenetic range of merA genes of Gram-negative bacteria. In control experiments, these primers successfully amplified a 288 bp region at the 3? end of previously characterized merA genes from Shewanella putrefaciens pMERPH, Acidithiobacillus ferrooxidans, Pseudomonas stutzeri pPB, Tn5041, Pseudomonas sp. K-62, and Serratia marcescens pDU1358.

  5. From clinical judgment to odds: a history of prognostication in anoxic-ischemic coma.

    Science.gov (United States)

    Wijdicks, Eelco F M

    2012-08-01

    Persistent coma from a major anoxic-ischemic injury to the brain may indicate there is less chance for full recovery. The tools of prognostication to assess comatose survivors of cardiopulmonary resuscitation have developed over several decades. Physicians would initially base their judgment on experience and data on outcome in these patients in the early years were merely on awakening not on disability. In the late 1970s, a large multicenter prospective study was performed on outcome in nontraumatic coma. The impetus for this study was the result of Plum and Jennet's collaboration. In 1981--for the first time--complex statistics were used to improve the accuracy of prognosis and became known as the "Levy algorithms." These early seminal studies shaped the prediction models and implied that clinical information alone could assist physicians in making a prediction. Later, probabilistic methods became more commonplace.

  6. Arsenic in groundwater of the Red River floodplain, Vietnam: Controlling geochemical processes and reactive transport modeling

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Larsen, Flemming; Hue, N.T.M.;

    2007-01-01

    chemistry over depth is homogeneous and a reactive transport model was constructed to quantify the geochemical processes along the vertical groundwater flow component. A redox zonation model was constructed using the partial equilibrium approach with organic carbon degradation in the sediment as the only...

  7. On metal diagenesis in contaminated sediments of the Deule river (northern France)

    Energy Technology Data Exchange (ETDEWEB)

    Lesven, L. [Universite Lille 1 (USTL), FRE CNRS 3298 Geosystemes, Equipe de Chimie Analytique et Marine, 59655 Villeneuve d' Ascq cedex (France); Lourino-Cabana, B. [Universite Lille 1 (USTL), FRE CNRS 3298 Geosystemes, Equipe de Chimie Analytique et Marine, 59655 Villeneuve d' Ascq cedex (France)] [Faculty of Natural Sciences and Technology, Department of Chemistry, 7491 Trondheim (Norway); Billon, G.; Recourt, P. [Universite Lille 1 (USTL), FRE CNRS 3298 Geosystemes, Equipe de Chimie Analytique et Marine, 59655 Villeneuve d' Ascq cedex (France); Ouddane, B., E-mail: baghdad.ouddane@univ-lille1.fr [Universite Lille 1 (USTL), FRE CNRS 3298 Geosystemes, Equipe de Chimie Analytique et Marine, 59655 Villeneuve d' Ascq cedex (France); Mikkelsen, O. [Faculty of Natural Sciences and Technology, Department of Chemistry, 7491 Trondheim (Norway); Boughriet, A. [Universite d' Artois, I.U.T. de Bethune Departement de Chimie, Rue de l' Universite, B.P. 819, 62408 Bethune cedex (France)

    2010-09-15

    Research highlights: {yields} Behaviour and fate of metal contaminants in sediments (remobilisation, dredging ...). {yields} Implication of metal contaminations on biogeochemical processes in anoxic sediments. {yields} Impacts on the distribution of anthropogenic metal in sediments. - Abstract: The objective of the present work was to assess depth-related variations in the (bio)geochemical processes involved in anoxic sediments from the Deule river, and to examine particularly their impacts on the distribution of anthropogenically sourced metals. Anoxic sediment samples were sliced and analyzed to determine total concentrations vs. depth of elements and corresponding pore waters were analyzed to determine concentration profiles with depth of pH, Eh, alkalinity, O{sub 2}, dissolved organic carbon (DOC), and main inorganic anions and cations present in the medium. It was shown that rapid depletions of O{sub 2}, NO{sub 3}{sup -} and SO{sub 4}{sup 2-}, accompanied with HCO{sub 3}{sup -} generation and a sharp decrease in the redox potential occurred within the first centimeters of the surface sediment as a consequence of early diagenesis. Bacterial reductive dissolution of Mn(III and IV) and Fe(III) oxides/hydroxides to Mn(II) and Fe(II) accompanied by microbial degradation of organic matter took place as well, and resulted in trace metal increases in the pore water at levels that raised the possibility of mineral generation. Thermodynamic calculations predicted removal of metals from interstitial waters through combinations with carbonates and/or sulfides. These took place either by direct precipitation to form pure crystals, or by coprecipitation/sorption with/into calcite and with pyritic compounds. Chemical sequential extraction data were useful in this work to support, at least partially, some thermodynamic predictions concerning the existence of interactions between trace metals and carbonate and sulfide ions to generate (co)precipitates. Electron paramagnetic

  8. Genome sequence of Halorhabdus tiamatea, the first archaeon isolated from a deep-sea anoxic brine lake.

    KAUST Repository

    Antunes, Andre

    2011-09-01

    We present the draft genome of Halorhabdus tiamatea, the first member of the Archaea ever isolated from a deep-sea anoxic brine. Genome comparison with Halorhabdus utahensis revealed some striking differences, including a marked increase in genes associated with transmembrane transport and putative genes for a trehalose synthase and a lactate dehydrogenase.

  9. Metabolic profiling of heat or anoxic stress in mouse C2C12 myotubes using multinuclear magnetic resonance spectroscopy.

    Science.gov (United States)

    Straadt, Ida K; Young, Jette F; Petersen, Bent O; Duus, Jens Ø; Gregersen, Niels; Bross, Peter; Oksbjerg, Niels; Bertram, Hanne C

    2010-06-01

    In the present study, the metabolic effects of heat and anoxic stress in myotubes from the mouse cell line C2C12 were investigated by using a combination of (13)C, (1)H, and (31)P nuclear magnetic resonance (NMR) spectroscopy and enrichment with [(13)C]-glucose. Both the (13)C and the (1)H NMR spectra showed reduced levels of the amino acids alanine, glutamate, and aspartate after heat or anoxic stress. The decreases were smallest at 42 degrees C, larger at 45 degrees C, and most pronounced after anoxic conditions. In addition, in both the (1)H and the (31)P NMR spectra, decreases in the high-energy phosphate compounds adenosine triphosphate and phosphocreatine with increasing severity of stress were identified. At anoxic conditions, an increase in (13)C-labeled lactate and appearance of glycerol-3-phosphate were observed. Accumulation of lactate and glycerol-3-phosphate is in agreement with a shift to anaerobic metabolism due to inhibition of the aerobic pathway in the mitochondria. Conversely, lower levels of unlabeled ((12)C) lactate were apparent at increasing severity of stress, which indicate that lactate is released from the myotubes to the medium. In conclusion, the metabolites identified in the present study may be useful markers for identifying severity of stress in muscles.

  10. Spatial extent and degree of oxygen depletion in the deep proto-North Atlantic basin during Oceanic Anoxic Event 2

    NARCIS (Netherlands)

    van Helmond, Niels A. G. M.; Ruvalcaba Baroni, Itzel; Sluijs, Appy; Sinninghe Damste, Jaap S.; Slomp, Caroline P.

    2014-01-01

    Massive organic matter burial due to widespread ocean anoxia across the Cenomanian/Turonian boundary event (∼94 Ma) resulted in a major perturbation of the global carbon cycle: the so-called Oceanic Anoxic Event 2 (OAE2). The characteristics and spatial distribution of the OAE2 deposits that forme

  11. Treatment of phenolics, aromatic hydrocarbons, and cyanide-bearing wastewater in individual and combined anaerobic, aerobic, and anoxic bioreactors.

    Science.gov (United States)

    Sharma, Naresh K; Philip, Ligy

    2015-01-01

    Studies were conducted on a mixture of pollutants commonly found in coke oven wastewater (CWW) to evaluate the biodegradation of various pollutants under anaerobic, aerobic, and anoxic conditions. The removal of the pollutants was monitored during individual bioreactor operation and using a combination of bioreactors operating in anaerobic-aerobic-anoxic sequence. While studying the performance of individual reactors, it was observed that cyanide removal (83.3 %) was predominant in the aerobic bioreactor, while much of the chemical oxygen demand (COD) (69 %) was consumed in the anoxic bioreactor. With the addition of cyanide, the COD removal efficiency was affected in all the bioreactors, and several intermediates were detected. While treating synthetic CWW using the combined bioreactor system, the overall COD removal efficiency was 86.79 % at an OLR of 2.4 g COD/L/day and an HRT of 96 h. The removal efficiency of 3,5-xylenol and cyanide, with inlet concentration of 150 and 10 mg/L, was found to be 91.8 and 93.6 % respectively. It was found that the impact of xylenol on the performance of the bioreactors was less than cyanide toxicity. Molecular analysis using T-RFLP revealed the dominance of strictly aerobic, mesophilic proteobacterium, Bosea minatitlanensis, in the aerobic bioreactor. The anoxic bioreactor was dominant with Rhodococcus pyridinivorans, known for its remarkable aromatic decomposing activity, while an unclassified Myxococcales bacterium was identified as the predominant bacterial species in the anaerobic bioreactor.

  12. Characterization of microbial arsenate reduction in the anoxic bottom waters of Mono Lake, California

    Science.gov (United States)

    Hoeft, S.E.; Lucas, F.; Hollibaugh, J.T.; Oremland, R.S.

    2002-01-01

    Dissimilatory reduction of arsenate (DAsR) occurs in the arsenic-rich, anoxic water column of Mono Lake, California, yet the microorganisms responsible for this observed in situ activity have not been identified. To gain insight as to which microorganisms mediate this phenomenon, as well as to some of the biogeochemical constraints on this activity, we conducted incubations of arsenate-enriched bottom water coupled with inhibition/amendment studies and Denaturing Gradient Gel Electrophoresis (DGGE) characterization techniques. DAsR was totally inhibited by filter-sterilization and by nitrate, partially inhibited (~50%) by selenate, but only slightly (~25%) inhibited by oxyanions that block sulfate-reduction (molybdate and tungstate). The apparent inhibition by nitrate, however, was not due to action as a preferred electron acceptor to arsenate. Rather, nitrate addition caused a rapid, microbial re-oxidation of arsenite to arsenate, which gave the overall appearance of no arsenate loss. A similar microbial oxidation of As(III) was also found with Fe(III), a fact that has implications for the recycling of As(V) in Mono Lake's anoxic bottom waters. DAsR could be slightly (10%) stimulated by substrate amendments of lactate, succinate, malate, or glucose, but not by acetate, suggesting that the DAsR microflora is not electron donor limited. DGGE analysis of amplified 16S rDNA gene fragments from incubated arsenate-enriched bottom waters revealed the presence of two bands that were not present in controls without added arsenate. The resolved sequences of these excised bands indicated the presence of members of the epsilon (Sulfurospirillum) and delta (Desulfovibrio) subgroups of the Proteobacteria, both of which have representative species that are capable of anaerobic growth using arsenate as their electron acceptor.

  13. Enhanced dechlorination of tetrachloroethylene by zerovalent silicon in the presence of polyethylene glycol under anoxic conditions.

    Science.gov (United States)

    Lee, Chun-Chi; Doong, Ruey-An

    2011-03-15

    The combination of zerovalent silicon (Si(0)) with polyethylene glycol (PEG) is a novel technique to enhance the dechlorination efficiency and rate of chlorinated hydrocarbons. In this study, the dechlorination of tetrachloroethylene (PCE) by Si(0) in the presence of various concentrations of PEG was investigated under anoxic conditions. Several surfactants including cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 were also selected for comparison. Addition of SDS and Tween 80 had little effect on the enhancement of PCE dechlorination, while CTAB and PEG significantly enhanced the dechlorination efficiency and rate of PCE by Si(0) under anoxic conditions. The Langmuir-Hinshelwood model was used to describe the dechlorination kinetics of PCE and could be simplified to pseudo-first-order kinetics at low PCE concentration. The rate constants (k(obs)) for PCE dechlorination were 0.21 and 0.36 h(-1) in the presence of CTAB and PEG, respectively. However, the reaction mechanisms for CTAB and PEG are different. CTAB could enhance the apparent water solubility of PCE in solution containing Si(0), leading to the enhancement of dechlorination efficiency and rate of PCE, while PEG prevented the formation of silicon dioxide, and significantly enhanced the dechlorination efficiency and rate of PCE at pH 8.3 ± 0.2. In addition, the dechlorination rate increased upon increasing PEG concentration and then leveled off to a plateau when the PEG concentration was higher than 0.2 μM. The k(obs) for PCE dechlorination by Si(0) in the presence of PEG was 106 times higher than that by Si(0) alone. Results obtained in this study would be helpful in facilitating the development of processes that could be useful for the enhanced degradation of cocontaminants by zerovalent silicon.

  14. Microbialite of anoxic condition from Permian-Triassic transition in Guizhou,China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.

  15. Microbialite of anoxic condition from Permian-Triassic transition in Guizhou, China

    Institute of Scientific and Technical Information of China (English)

    WU YaSheng; JIANG HongXia; YANG Wan; FAN JiaSong

    2007-01-01

    Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun, Guizhou Province. They generally range from 0.15 to 0.30 mm across, with micritic wall and filled by micro-sparry calcites, and are evenly scattered in micritic matrix. Their abundance makes the rock assigned to microbialites. The accompanied organisms include ostracods and algal mat, but no gastropods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections, this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the microbial organism was benthic, and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus, it does not belong to these two phyla. It may belong to lower green algae, and is assigned to a new species in a new genus, Ziyunosphaeridium sinensis gen. et sp. nov. Up to now, the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997), (2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999), (3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999), (4) spherical microbial limestone adapted to anoxic environments described from Ziyun, Guizhou reported in this paper, (5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005), and (6) stromatolites. All these microbialites are not reefs in the proper sense, and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.

  16. Experimental Study on Anoxic/Oxic Bioreactor and Constructed Wetland for Rural Domestic Wastewater Treatment

    Directory of Open Access Journals (Sweden)

    John Leju Celestino Ladu

    2014-01-01

    Full Text Available This study examined the removal of nutrients from the domestic wastewater through the application of integrated anoxic/oxic (A/O bio-reactor and constructed wetland system. Influent and effluent samples were collected from the system and experimented for Chemical Oxygen Demand (COD, NH4+-N, NO3--N and TP in the laboratory. Different Hydraulic Retention Time (HRT and recycle ratios were applied in the reactor to evaluate their influence on removal efficiency of nutrients. The temperature was controlled between 20 to 24°C and pH ranges was 7.6-8.1. The result revealed average COD removal efficiencies of 47, 68, 74, 83 and 85% at HRT of 1.5, 4, 2, 3 and 5 h. The average removal of NH4+-N was 60.3, 63.0, 64.4, 71 and 91.8 % operated with HRT of 2, 3, 5, 1.5 and 4 h, respectively. The average removal of NO3- -N was 92, 94, 95 and 97% run with HRT of 2, 1.5, 3, 5 and 4 h, respectively. The average removal of TP was 78, 85, 88 and 89% operated with HRT of 5, 3, 2 and 1 h. This system removed up to 74.1, 94.4 and 85% of NH4+-N, NO3- -N and TP with proper pH control using external source of alkalinity. The result showed the optimum recycle ratio of 3. The results obtained attest that, the integrated anoxic/oxic bioreactor and constructed wetland is feasible and efficient for wastewater treatment.

  17. Effect of Cretaceous oceanic anoxic events on the evolutionary trend of planktonic foraminifera

    Science.gov (United States)

    Kuroyanagi, A.; Ozaki, K.; Kawahata, H.

    2014-12-01

    It is widely thought that oceanic redox state is essential for the evolutionary history of life on the earth, and "anoxic events" have been proposed as one of the causal mechanisms for mass extinctions. During mid-Cretaceous, widely known as the extremely warm period, oceanic anoxic events (OAEs) occurred several times and they would have caused a substantial impact on the biosphere. Planktonic foraminifera are marine planktons with calcite tests and their productions constitute ~30-80% of the modern deep-marine calcite budget, thus they play an important role in the global carbon cycle. Previous study reported that planktonic foraminifera displayed the high turnover (extinction and speciation) rate at or near the major OAEs. However, the impact of Cretaceous OAEs on the evolutionary trend of planktonic foraminifera remains obscure. In this study, we investigated the role of spatiotemporal extent of anoxia on the evolutionary trend of planktonic foraminifera by assessing the extinction/speciation rate of planktonic foraminifera around Cretaceous OAEs. The number of foraminiferal species increased across the OAE1a and then showed a peak after this episode. Around OAE2, several planktonic foraminifera species became extinct and several speciated, however, long-term trends in foraminiferal evolution showed no drastic changes near the event. Therefore these results suggest that the ocean surface environment at OAEs would not have a direct effect on foraminiferal extinction/speciation. This interpretation is reinforced when considering the recent culturing results, which demonstrate that modern planktonic foraminifera have a high tolerance to extremely low dissolved oxygen levels than expected. Accumulating geochemical data also suggest a spatial heterogeneity of oceanic anoxia/euxinia during OAE2. These results lead us to conclude that Cretaceous OAEs would not directly related to planktonic foraminiferal extinction due to regional distribution of anoxia/euxinia.

  18. SPECIFIC SOLUTIONS GROUNDWATER FLOW EQUATION

    OpenAIRE

    Syahruddin, Muhammad Hamzah

    2014-01-01

    Geophysic publication Groundwater flow under surface, its usually slow moving, so that in laminer flow condition can find analisys using the Darcy???s law. The combination between Darcy law and continuity equation can find differential Laplace equation as general equation groundwater flow in sub surface. Based on Differential Laplace Equation is the equation that can be used to describe hydraulic head and velocity flow distribution in porous media as groundwater. In the modeling Laplace e...

  19. GROUNDWATER PROTECTION MANAGEMENT PROGRAM DESCRIPTION.

    Energy Technology Data Exchange (ETDEWEB)

    PAQUETTE,D.E.; BENNETT,D.B.; DORSCH,W.R.; GOODE,G.A.; LEE,R.J.; KLAUS,K.; HOWE,R.F.; GEIGER,K.

    2002-05-31

    THE DEPARTMENT OF ENERGY ORDER 5400.1, GENERAL ENVIRONMENTAL PROTECTION PROGRAM, REQUIRES THE DEVELOPMENT AND IMPLEMENTATION OF A GROUNDWATER PROTECTION PROGRAM. THE BNL GROUNDWATER PROTECTION MANAGEMENT PROGRAM DESCRIPTION PROVIDES AN OVERVIEW OF HOW THE LABORATORY ENSURES THAT PLANS FOR GROUNDWATER PROTECTION, MONITORING, AND RESTORATION ARE FULLY DEFINED, INTEGRATED, AND MANAGED IN A COST EFFECTIVE MANNER THAT IS CONSISTENT WITH FEDERAL, STATE, AND LOCAL REGULATIONS.

  20. Groundwater types in Southeast Srem

    Directory of Open Access Journals (Sweden)

    Gregorić Enike

    2009-01-01

    Full Text Available The region of Southeast Srem is rich in ground waters, which is of great significance to agricultural production. The objective of this paper was to designate the zones of different groundwater types from the aspect of recharge, based on the analysis of groundwater regimes in the study area. A very complex groundwater regime in Southeast Srem, which depends on a great number of natural and some anthropogenic factors, makes it difficult to designate clearly the zones of the three main types of groundwater regime. Still, the boundaries of the zones of groundwater regime types were defined based on the results of correlation analysis of the basic factors affecting the groundwater regime. Zone I includes the climatic type of groundwater. Its fluctuation corresponds to the vertical factors of water balance (precipitation and evaporation and it is not affected by the river water level. This zone extends North and East of the line Putinci, Golubinci, Stara Pazova, Batajnica, Dobanovci, mainly in the area of the loess plateau. Within the zone, groundwater is at a relatively great depth. Only exceptionally, in the valleys, it appears almost on the surface. Zone II includes the climatic-hydrological groundwater type, which is the transition between the climatic type and the hydrological type. The fluctuation of groundwater regime is affected both by the effect of vertical balance factors, and by the effect of watercourses. Climatic-hydrological groundwater type covers the central and the lowest part of the study area and the South part of the middle terrace. Zone III is classified as the hydrological groundwater type and it covers the riparian areas along the Sava and the Danube. The aquifer is hydraulically connected with the river Sava.

  1. A fully coupled depth-integrated model for surface water and groundwater flows

    Science.gov (United States)

    Li, Yuanyi; Yuan, Dekui; Lin, Binliang; Teo, Fang-Yenn

    2016-11-01

    This paper presents the development of a fully coupled surface water and groundwater flow model. The governing equations of the model are derived based on a control volume approach, with the velocity profiles of the two types of flows being both taken into consideration. The surface water and groundwater flows are both modelled based on the unified equations and the water exchange and interaction between the two types of flows can be taken into account. The model can be used to simulate the surface water and groundwater flows simultaneously with the same numerical scheme without other effort being needed to link them. The model is not only suitable for the porous medium consisting of fine sediments, but also for coarse sediments and crushed rocks by adding a quadratic friction term. Benchmark tests are conducted to validate the model. The model predictions agree well with the data.

  2. The early Toarcian anoxic event: what the beginning and the end of the story are?

    Science.gov (United States)

    Mattioli, Emanuela; Plancq, Julien; Raucsik, Béla

    2010-05-01

    The early Toarcian anoxic event: what the beginning and the end of the story are? E. Mattioli (1), J. Plancq (1), and B. Rauksik (2) (1) UMR 5125 PEPS, CNRS, France; Université Lyon 1, Campus de la DOUA, Bâtiment Géode, 69622 Villeurbanne Cedex, France (emanuela.mattioli@univ-lyon1.fr) (2) Department of Earth and Environmental Sciences, University of Pannonia, Veszprém, Hungary The early Toarcian anoxic event (T-OAE) and the associated biotic crisis have received much attention in the last decade. However, the events forewarning the crisis as well as its aftermath are still poorly known. The T-OAE coincides with a prominent carbon isotope negative excursion (T-CIE) that is preceded by an excursion of similar intensity at the Pliensbachian-Toarcian boundary (Hesselbo et al., 2007). The onset of T-CIE occurred some 700 kyr later than the end of the Boundary-CIE (Suan et al., 2008a). This succession of events demonstrates that the T-OAE was a complex suite of environmental perturbations. In this work, we focused on calcareous nannofossil assemblages occurring in the Peniche section (Portugal) during the Boundary-CIE with the aim to understand if calcifying plankton reacted in a similar/different way to the two CIEs. Also, two sections and one borehole located along a W-E transect, along the NW-Tethyan shelf (in the Yorkshire coast, in the E Paris Basin, and in Mecsek Basin, respectively), were investigated to assess which way calcareous nannoplankton recovered after the crisis, and if the recovery was a synchronous event. The production by nannoplankton collapsed during the T-CIE, as demonstrated by the lowest absolute abundance of nannofossils measured in Peniche and other studied sites (Mattioli et al., 2008). Besides this nannofossil abundance decrease, also the size of the incertae sedis Schizosphaerella test was drastically reduced (Suan et al., 2008b). If a similar size decrease is also recorded during the Boundary-CIE, calcareous nannofossil abundances are

  3. Importance of Unattached Bacteria and Bacteria Attached to Sediment in Determining Potentials for Degradation of Xenobiotic Organic Contaminants in an Aerobic Aquifer

    DEFF Research Database (Denmark)

    Nielsen, Per Henning; Albrechtsen, Hans-Jørgen; Christensen, Thomas Højlund;

    1992-01-01

    , was attached to the groundwater sediment (18 x 106 to 25 x 106 cells per g [dry weight]), and only a minor part was unattached in the groundwater (0.6 x 106 to 5.5 x 106 cells per ml). Experiments involving aquifer sediment suspensions showed identical degradation potentials in the laboratory and in the field...... for studying the degradation potential for xenobiotic organic contaminants should contain sediment to obtain the highest numbers of bacteria as well as the broadest and most stable degradation. When only the fine (silt- and clay-size) particles of the sediment were used, nearly the same advantages were gained...

  4. Airborne and ground-based transient electromagnetic mapping of groundwater salinity in the Machile–Zambezi Basin, southwestern Zambia

    DEFF Research Database (Denmark)

    Chongo, Mkhuzo; Vest Christiansen, Anders; Tembo, Alice

    2015-01-01

    The geological and morphological evolution of the Kalahari Basin of Southern Africa has given rise to a complex hydrogeological regime that is affected by water quality issues. Among these concerns is the occurrence of saline groundwater. Airborne and ground-based electromagnetic surveying...... is an efficient tool for mapping groundwater quality variations and has been used extensively to explore the Kalahari sediments, e.g., in Botswana and Namibia. Recently, airborne and groundbased mapping of groundwater salinity was conducted in the Machile–Zambezi Basin, southwestern Zambia, using the versatile....... The saline lacustrine sediments infilling the Machile Graben are responsible for the low formation resistivity (below 13 Ωm) and high salinity (above 7000 µS/cm) observed in the groundwater and are probably related to the complex evolutionary history of Palaeo-Lake Makgadikgadi....

  5. Does shallow geothermal energy use threaten groundwater ecosystem functions?

    Science.gov (United States)

    Brielmann, Heike; Schmidt, Susanne I.; Ferraro, Francesco; Schreglmann, Kathrin; Griebler, Christian; Lueders, Tillmann

    2010-05-01

    Today, the use of geothermal energy is strongly promoted as an alternative and sustainable source of energy. However, regarding the authorization, regulation and monitoring of such facilities with respect to possible environmental impacts, a severe lack of knowledge has been identified. Aquifers are not only abiotic reservoirs of water and sediment, but they are complex ecosystems harbouring an almost untapped diversity of microorganisms and fauna. Intrinsic groundwater organisms are highly adapted to extremely oligotrophic, but stable conditions including temperature. At the same time, groundwater biota are the key drivers of important ecosystem services, especially functions connected to water quality. So what happens if groundwater biota need to cope with sudden temperature dynamics caused by GSHP use? Potential effects of thermal use on pristine aquifers, and on groundwater systems already facing enhanced loads of nutrients or contamination require urgent scientific attention. Within this project, we have assessed - both in the field and in the laboratory - the impacts of temperature discharge and withdrawal on biotic parameters and functional characteristics of exemplary shallow groundwater systems. In the field, aquifer microbes did not show significant impacts under increased temperatures in terms of total cell numbers, selected enzyme activities and carbon production. However, bacterial diversity clearly increased with temperature, accompanied by the appearance of new bacterial lineages and the disappearance of others. On the contrary, faunal diversity decreased with temperature, highlighting the temperature sensitivity of groundwater invertebrates. These results demonstrate that aquifer thermal energy discharge can affect intrinsic aquifer biotic populations, while at the same time being only one of several drivers contributing to total variability connected to seasonal dynamics and spatial heterogeneity. In laboratory column experiments covering a larger

  6. The comparative geochemistries of lignins and carbohydrates in an anoxic fjord

    Science.gov (United States)

    Hamilton, Susan E.; Hedges, John I.

    1988-01-01

    A reducing, varved sediment core and monthly (May-September) plankton and sediment trap samples from Saanich Inlet, B.C., Canada, were analyzed for their elemental, lignin and neutral sugar compositions. Total yields of lignin-derived phenols from both the sediment trap and core samples indicated less than 15% and 30%, respectively, of chemically recognizable vascular plant remains, derived predominantly from gymnosperm wood and nonwoody angiosperm tissues. The elevated vanillyl and syringyl acid/aldehyde ratios of this material compared to fresh plant material indicated that it suffered mild aerobic decomposition prior to introduction to the Inlet. Most of the remaining particular organic material was nitrogen-rich, carbohydrate-poor and apparently plankton-derived. Organic carbon, total nitrogen, and total neutral sugars and lignin phenols all exhibited decreasing concentrations with depth in a region of uniform varving (upper 15 cm) in the sediment core. All profiles exhibited particularly steep concentration decreases within the top 2 cm of sediment. First-order decay constants for all four chemical categories within the upper 14 cm of the core ranged between 0.1-0.2 yr -1. Neutral sugars were consistently the most reactive chemical class, accounting for roughly 15% of the total organic carbon turnover. Although lignin appeared to be degraded within the sediment core, this degradation was nonselective for different lignin types and did not lead to increased acid/aldehyde ratios as occur during aerobic lignin decomposition. Comparisons of the yields of individual neutral sugars from the sediment and sediment trap samples to those expected from the vascular plant component alone indicated that the vascular plant debris in the upper portion of the sediment core had lost a portion of its initial glucose, lyxose, and mannose. In contrast, rhamnose and fucose were produced by all samples in large excess of total yields expected for chemically intact vascular plant

  7. Simultaneous Organics and Nutrients Removal from Domestic Wastewater in a Combined Cylindrical Anoxic/Aerobic Moving Bed Biofilm Reactor

    Directory of Open Access Journals (Sweden)

    Husham T. Ibrahim

    2014-03-01

    Full Text Available The aim of present study was to design and construct an continuous up-flow pilot scale Moving Bed Biofilm Reactor (MBBR which is consists of combined cylindrical Anoxic/Aerobic MBBR in nested form with anoxic/aerobic volume ratio equal to 0.16 to treated 4 m3 /days of domestic wastewater in Chongqing city at Southwest China. The treatment must be satisfactory to meet with grade B of discharge standard of pollutants for municipal wastewater treatment plant in China (GB/T18918-2002. Kaldnes (K1 media was used as a carrier in both reactors at a media fill ratio equal to 50%. The reactors was operated under the Anoxic/Oxic (An/O process which must meet stringent TN limits without sludge returning into the system and only an internal recycling was performed from aerobic to anoxic reactor. After developing the biofilm on the media, reactor was operated at 3 different Hydraulic Residence Time (HRT ranging from 4.95 to 8.25 h. During operation the internal recycle ratio to eliminate nitrogen compounds were 100% of inflow rate and the average Dissolved Oxygen concentration (DO in aerobic and anoxic MBBRs were 4.49 and 0.16 mg/L, respectively. The obtained results showed that the HRT of 6.2 h was suitable for simultaneous removal of COD, NH4+-N, TN and TP. In this HRT the average removal efficiencies were 93.15, 98.06, 71.67 and 90.88% for COD, NH4+-N, TN and TP, respectively.

  8. Metatranscriptomic analyses of plankton communities inhabiting surface and subpycnocline waters of the Chesapeake Bay during oxic-anoxic-oxic transitions.

    Science.gov (United States)

    Hewson, Ian; Eggleston, Erin M; Doherty, Mary; Lee, Dong Yoon; Owens, Michael; Shapleigh, James P; Cornwell, Jeffrey C; Crump, Byron C

    2014-01-01

    We used metatranscriptomics to study the gene transcription patterns of microbial plankton (0.2 to 64 μm) at a mesohaline station in the Chesapeake Bay under transitions from oxic to anoxic waters in spring and from anoxic to oxic waters in autumn. Samples were collected from surface (i.e., above pycnocline) waters (3 m) and from waters beneath the pycnocline (16 to 22 m) in both 2010 and 2011. Metatranscriptome profiles based on function and potential phylogeny were different between 2010 and 2011 and strongly variable in 2011. This difference in variability corresponded with a highly variable ratio of eukaryotic to bacterial sequences (0.3 to 5.5), reflecting transient algal blooms in 2011 that were absent in 2010. The similarity between metatranscriptomes changed at a lower rate during the transition from oxic to anoxic waters than after the return to oxic conditions. Transcripts related to photosynthesis and low-affinity cytochrome oxidases were significantly higher in shallow than in deep waters, while in deep water genes involved in anaerobic metabolism, particularly sulfate reduction, succinyl coenzyme A (succinyl-CoA)-to-propionyl-CoA conversion, and menaquinone synthesis, were enriched relative to in shallow waters. Expected transitions in metabolism between oxic and anoxic deep waters were reflected in elevated levels of anaerobic respiratory reductases and utilization of propenediol and acetoin. The percentage of archaeal transcripts increased in both years in late summer (from 0.1 to 4.4% of all transcripts in 2010 and from 0.1 to 6.2% in 2011). Denitrification-related genes were expressed in a predicted pattern during the oxic-anoxic transition. Overall, our data suggest that Chesapeake Bay microbial assemblages express gene suites differently in shallow and deep waters and that differences in deep waters reflect variable redox states.

  9. Radon in groundwater of eastern Doon valley, Outer Himalaya

    Energy Technology Data Exchange (ETDEWEB)

    Choubey, V.M. E-mail: vchoubey1@rediffmail.com; Bartarya, S.K.; Ramola, R.C

    2003-06-01

    The radon content in water may serve as a useful tracer for several geohydrological processes. The hydrodynamic factor, presence of radium in host rocks, as well as the soil porosity and permeability control its concentration in groundwater. In order to understand the factors that control the occurrence of radon in groundwater of Doon valley in Outer Himalaya, a total of 34 groundwater samples were collected from handpumps and tubewells covering three hydrogeological units/areas in the eastern part of Doon valley. Radon variation in tubewells and handpumps varies from 25.4{+-}1.8 to 92.5{+-}3.4 Bq/l with an average of 53.5{+-}2.6 Bq/l. A significant positive correlation between radon concentration and depth of the wells was observed in the Doiwala-Dudhli and Jolleygrant areas suggesting that radon concentration increases with drilling depth in areas consisting of sediments of younger Doon gravels, whereas samples of the Ganga catchment show negative correlation. The high radon levels at shallower depths in the Ganga catchment (consisting of fluvial terraces of Ganga basin) indicate uranium-rich sediments at shallower depth.

  10. Groundwater-quality data and regional trends in the Virginia Coastal Plain, 1906-2007

    Science.gov (United States)

    McFarland, E. Randolph

    2010-01-01

    A newly developed regional perspective of the hydrogeology of the Virginia Coastal Plain incorporates updated information on groundwater quality in the area. Local-scale groundwater-quality information is provided by a comprehensive dataset compiled from multiple Federal and State agency databases. Groundwater-sample chemical-constituent values and related data are presented in tables, summaries, location maps, and discussions of data quality and limitations. Spatial trends in groundwater quality and related processes at the regional scale are determined from interpretive analyses of the sample data. Major ions that dominate the chemical composition of groundwater in the deep Piney Point, Aquia, and Potomac aquifers evolve eastward and with depth from (1) 'hard' water, dominated by calcium and magnesium cations and bicarbonate and carbonate anions, to (2) 'soft' water, dominated by sodium and potassium cations and bicarbonate and carbonate anions, and lastly to (3) 'salty' water, dominated by sodium and potassium cations and chloride anions. Chemical weathering of subsurface sediments is followed by ion exchange by clay and glauconite, and subsequently by mixing with seawater along the saltwater-transition zone. The chemical composition of groundwater in the shallower surficial and Yorktown-Eastover aquifers, and in basement bedrock along the Fall Zone, is more variable as a result of short flow paths between closely located recharge and discharge areas and possibly some solutes originating from human sources. The saltwater-transition zone is generally broad and landward-dipping, based on groundwater chloride concentrations that increase eastward and with depth. The configuration is convoluted across the Chesapeake Bay impact crater, however, where it is warped and mounded along zones having vertically inverted chloride concentrations that decrease with depth. Fresh groundwater has flushed seawater from subsurface sediments preferentially around the impact crater

  11. Groundwater controls on biogeomorphic succession and river channel morphodynamics

    Science.gov (United States)

    Bätz, N.; Colombini, P.; Cherubini, P.; Lane, S. N.

    2016-10-01

    Biogeomorphic succession describes feedbacks between vegetation succession and fluvial processes that, at the decadal timescale, lead to a transition from bare river-deposited sediment to fully developed riparian forest. Where the rate of stabilization by biogeomorphic succession is greater than the rate of ecological disturbance by fluvial processes, a river is likely to evolve into less dynamic states. While river research has frequently considered the physical dimensions of morphodynamics, less is known about physical controls on succession rates, and how these impact stream morphodynamics. Here we test the hypothesis that groundwater dynamics influence morphodynamics via the rate of biogeomorphic succession. We applied historic imagery analysis in combination with dendroecological methods for willows growing on young gravelly fluvial landforms along a steep groundwater-depth gradient. We determined the following: floodplain morphodynamics and plant encroachment at the decadal scale, pioneer willow growth rates, and their relationships to hydrological variables. Willow growth rates were correlated with moisture availability (groundwater, discharge, and precipitation variability) in the downwelling reach, while little correlation was found in the upwelling reach. After a reduction in ecological disturbance frequency, data suggest that where groundwater is upwelling, biogeomorphic succession is fast, the engineering effect of vegetation is quickly established, and hence channel stability increased and active channel width reduces. Where groundwater is downwelling, deeper and more variable, biogeomorphic succession is slower, the engineering effect is reduced, and a wider active width is maintained. Thus, groundwater is an important control on biogeomorphic feedbacks intensity and, through the stabilizing effect of vegetation, may drive long-term river channel morphodynamics.

  12. Statistical characterisation and stochastic parameterisation of sedimentary geological formations on their reaction capacity for sustainable groundwater quality management

    OpenAIRE

    Griffioen, J.; Vermooten, S.; Keijzer, T.; Bakr, M; Valstar, J.

    2012-01-01

    The fate of contaminants in groundwater aquifers is determined by the buffering capacity of those aquifers together with the composition of inflowing groundwater. A nationwide characterisation of the environmental geochemistry of the shallow subsurface (down to 30 m below surface) has been started in the Netherlands. This covers: 1. the reaction capacity of sediments as buffer for contamination, and 2. typical elemental composition of geological formations and the association between trace el...

  13. Combining local lithofacies and global geochemical signals to test the acidification hypothesis for the onset of Oceanic Anoxic Event 2 in the U.S. Western Interior Basin

    Science.gov (United States)

    Jones, M. M.; Sageman, B. B.; Selby, D. S.; Oakes, R. L.; Bralower, T. J.; Parker, A. L.; Leckie, R. M.; Sepulveda, J.

    2015-12-01

    Strata preserving Oceanic Anoxic Event 2 (OAE2), which span the Cenomanian-Turonian (C/T; Late Cretaceous), exhibit evidence of widespread anoxia, a major perturbation to the global carbon cycle, and increased biotic turnover rates. It has been hypothesized that a major volcanic (LIP) eruption, increased CO2 levels, and significant climate warming triggered the event. Recently, OAE2 has also been cited as a potential example of ocean acidification in Earth history and therefore has potential to offer predictive insights on impacts of increasing modern pCO2 levels. As part of an effort to test this hypothesis, the 131-m Smoky Hollow #1 (SH-1) core was drilled near Big Water, Utah during the summer of 2014. The core recovered an expanded stratigraphic record of OAE2 from the mud-rich western margin of the Western Interior Seaway. A high-resolution stable carbon isotope record from bulk organic carbon (δ13Corg) indicates near-continuous preservation of OAE2 with a sustained +2.5‰ excursion that is over 5 times the thickness of the same excursion at the C/T GSSP in Pueblo, Colorado. Notably, this record is characterized by a 1-m thick carbonate-barren interval at the δ13C excursion's onset. This may indicate an episode of ocean acidification driving suppressed carbonate sedimentation or carbonate dissolution. An alternative interpretation is that variations in carbonate concentrations are unrelated to changes in ocean chemistry and are instead driven by changes in local sedimentation patterns (e.g. transgressive-regressive parasequences). To test these hypotheses, a regional lithostratigraphic correlation to the nearshore Cottonwood Canyon section is constructed to assess whether prograding sandy parasequences may have altered carbonate sedimentation rates at the SH-1 locality. Initial osmium and δ13C chemostratigraphies are also developed to constrain the timing of perturbations in global geochemical cycles at the initiation of OAE2, including the onset of large

  14. The groundwater subsidy to vegetation: groundwater exchanges between landcover patches

    Science.gov (United States)

    Steven, L. I.; Gimenez, R.; Jobbagy, E. G.

    2015-12-01

    The Gran Chaco is a hot, dry plain, that spans over 60 million hectares across Bolivia, Paraguay, Brazil and Argentina. It supports high biodiversity in its dry forest and savannahs, but is rapidly being converted to agriculture in response to growing soy demand and technology including genetic modification and zero-till, that has made cultivation in drier landscapes more viable. Under natural conditions, the deep-rooted, native vegetation of the Chaco effectively captured all rainfall for evapotranspiration resulting in near zero groundwater recharge under the dry forest. Conversion to shallower rooted soy and corn, combined with the fallow period prior to the growing season, reduces evapotranspiration and allows some water to percolate through the root zone and recharge the groundwater system. When this groundwater recharge occurs, it creates groundwater mounding and a hydraulic gradient that drives flow to adjacent landcover patches where recharge does not occur. As the watertable rises, groundwater becomes available to the deep-rooted, dry forest vegetation. We develop a soil and groundwater flow model to simulate infiltration, percolation, evaporation, rootwater uptake, groundwater recharge and the lateral transfer of water between adjacent landcover patches to quantify this groundwater subsidy from converted agricultural lands to remnant patches of dry forest.

  15. Groundwater dynamics in wetland soils control the production and transfer mechanisms of dissolved reactive phosphorus in an agricultural landscape

    Science.gov (United States)

    Dupas, Rémi; Gu, Sen; Gruau, Gérard; Gascuel-Odoux, Chantal

    2015-04-01

    Because of its high sorption affinity on soils solid phase, mitigation options to reduce diffuse P transfer usually focus on trapping particulate P forms delivered via surface flowpaths. Therefore, vegetated buffer zones placed between croplands and watercourses have been promoted worldwide, sometimes in wetland areas. To investigate the risk of such P trapping riparian wetlands (RWs) releasing dissolved P to rivers, we monitored molybdate reactive P (MRP) in the free soil solution of two RWs in an intensively farmed catchment. Two main mechanisms causing MRP release were identified in light of the geochemical and hydrological conditions in the RWs, controlled by groundwater dynamics. First, soil rewetting after the dry summer was associated with the presence of a pool of mobile P, limited in size. Its mobilization started under conditions of water saturation caused by groundwater uprise in RW organo-mineral soil horizons. Second, the establishment of anoxic conditions in the end of the winter caused reductive solubilization of Fe oxide-hydroxide, along with release of P. Comparison between sites revealed that the first MRP release occurred only in a RW with P enriched soils, whereas the second was recorded even in a RW with a low soil P status. Seasonal variations in MRP concentrations in the stream were synchronized with those in RW soils. Hence, enriched and/or periodically anoxic RWs can act as a key component of the P transfer continuum in agricultural landscapes by converting particulate P from croplands into MRP released to rivers.

  16. Hydrogeology and simulation of groundwater flow and land-surface subsidence in the northern part of the Gulf Coast aquifer system, Texas, 1891-2009

    Science.gov (United States)

    Kasmarek, Mark C.

    2012-01-01

    In cooperation with the Harris–Galveston Subsidence District, Fort Bend Subsidence District, and Lone Star Groundwater Conservation District, the U.S. Geological Survey developed and calibrated the Houston Area Groundwater Model (HAGM), which simulates groundwater flow and land-surface subsidence in the northern part of the Gulf Coast aquifer system in Texas from predevelopment (before 1891) through 2009. Withdrawal of groundwater since development of the aquifer system has resulted in potentiometric surface (hydraulic head, or head) declines in the Gulf Coast aquifer system and land-surface subsidence (primarily in the Houston area) from depressurization and compaction of clay layers interbedded in the aquifer sediments.

  17. Dissolution of unirradiated UO{sub 2} fuel in synthetic groundwater. Final report (1996-1998)

    Energy Technology Data Exchange (ETDEWEB)

    Ollila, K. [VTT Chemical Technology, Espoo (Finland)

    1999-05-01

    with all groundwater compositions. Longer contact times are needed to identify secondary phases predicted by modelling (EQ3/6). In the anoxic dissolution experiments with UO{sub 2} pellets, the solubilities of U in synthetic groundwaters ranged from 9.6 x 10{sup -10} ... 3.5 10{sup -8} M. The lowest concentrations (10{sup -9} M) were measured in synthetic groundwaters with redox control (low Eh: -0.2 ... 0.3 V). The composition of the groundwater had a minor effect. The solubilities measured in the oversaturation experiments were generally in good agreement with the pellet experiments. A trend towards lower solubility was observed with fresh (Allard) composition. According to the analyses with XRD, a weakly crystalline UO{sub 2}-U{sub 3}O{sub 7}, was precipitated with all compositions. In saline groundwaters, an impure U(IV)-oxide, including possibly Sr or Ca, seemed to precipitate with the UO{sub 2}-U{sub 3}O{sub 7}. The measured Eh values in the anoxic experiments suggest that the presence of the U solid phase had a buffering effect on Eh. (orig.) 26 refs.

  18. Nitrate bioreduction in redox-variable low per