Jarosite formation in the uranium processing circuit of Denison Mines Limited, Elliot Lake, Ontario

International Nuclear Information System (INIS)

Dutrizac, J.E.

1985-04-01

Jarosite precipitation occurs in several parts of the uranium processing circuit of Denison Mines Limited, Elliot Lake, Ontario. Extensive precipitation of jarosite takes place in the filter cloth and on the drum face of the secondary drum filters, and this precipitation causes severe operating difficulties. Precipitation of jarosite is also observed in the ion exchange beads, but it is not known whether the jarosite is responsible for the observed decrease in resin efficiency. The resin beads are also rimmed with significant quantities of silica, lead, phosphate, sulphate, etc. which could be responsible for the fouling of the resin. In every instance, potassium jarosite, containing only minor amounts of sodium or ammonium, was the observed species; the potassium likely originates from the acid leaching of muscovite in the ore. Potential methods of avoiding the jarosite problem are discussed, but these may not be compatible with the overall process requirements

Report on investigation of remedial measures for the radiation reduction and radioactive decontamination of Elliot Lake, Ontario

International Nuclear Information System (INIS)

1981-02-01

This is the fourth annual report on a program to monitor and reduce radon daughter exposures in the town of Elliot Lake, Ontario. Twelve month's WL survey measurements were completed in 1980 and showed that 22 houses exceeded the remedial action criterion of 0.02 WL. In a few cases gamma radiation levels were high enough to require remedial action in driveways and public areas, but not inside houses. During 1980 remedial work was carried out on 85 buildings; work was completed on 58. The most frequent routes of entry for radon and radon daughters were untrapped weeping tile connected to a floor drain or sump, and the wall to floor joint

Use of the emergency room in Elliot Lake, a rural community of Northern Ontario, Canada.

Science.gov (United States)

Harris, L; Bombin, M; Chi, F; DeBortoli, T; Long, J

2004-01-01

There is ample documentation that use of hospital emergency facilities for reasons other than urgencies/emergencies results in clogged services in many urban centers. However, little has been published about similar misuse of emergency rooms/departments in rural and remote areas, where the situation is usually compounded by a scarcity of healthcare professionals. In Canada there is a shortage of physicians in rural and remote areas as a consequence of misdistribution (most physicians staying in southern urban centers after residence), and there is a chronic misuse of facilities meant for urgencies/emergencies to cope with primary healthcare needs. We address the problem in Elliot Lake, a rural Northern Ontario community of 12,000 people. The economy of Elliot Lake was based on uranium mining until the mid-1990s, when it drastically changed to become a center for affordable retirement and recreational tourism. As a consequence, at the present time the proportion of seniors in Elliot Lake doubles the Canadian average. Our objectives are to elucidate the demographics of emergency room (ER) clients and the effect of the elderly population; the nature of ER use; the perceived level of urgency of clients versus health professionals; and possible alternatives offered to non-urgent/emergency visits. This is the first study of the kind in Northern Ontario, a region the size of France. The study, conducted in July 2001, used a prospective survey, completed by patients and attending clinicians at the time of a patient's presentation to the ER of St Joseph's General Hospital. This hospital is staffed by family physicians, a nurse practitioner, and registered nurses (RNs). The catchment area population (town plus surrounding areas) of the hospital is approximately 18,000 people. ER clients were interviewed verbally, and the attending health professionals responded to written questionnaires. Demographics were recorded (age, sex, employment and marital status), as was each client

Radionuclide uptake by various plants growing on uranium tailings, Elliot Lake, Ontario

International Nuclear Information System (INIS)

Dave, N.K.; Lim, T.P.; Cloutier, N.R.

1984-02-01

Detectable levels of Ra-226 (0.2 to 27.6 pCi/g), Ra-223 (<= 0.1 to 4.3 pCi/g) and Pb-210 (0.6 to 6.9 pCi/g) were measured in various species of vegetation growing on various uranium tailings in Elliot Lake. On the other hand levels of Th-232 (<= 0.1 pCi/g), Th-230 (<= 0.1 pCi/g) were near detection limits in the same vegetation samples. In tailings substrates, all radionuclides investigated were detectable: Ra-226 (8.8 to 552 pCi/g), Ra-223 (3.1 to 213 pCi/g), Pb-210 (5.4 to 441 pCi/g), Th-232 (1.6 to 15.4 pCi/g), Th-230 (4.9 to 62 pCi/g) and Th-228 (1.3 to 38 pCi/g). Lower Th than Ra and Pb levels in tailings substrate were believed to be the cause for the relatively lower Th levels measured in vegetation when compared to Ra and Pb concentrations. No correlation was observed between the level of a given radionuclide in tailings and in the vegetation growing on that tailings

Ra-226 concentrations in blueberries Vaccinium angustifolium Ait. near an inactive uranium tailings site in Elliot Lake, Ontario, Canada

International Nuclear Information System (INIS)

Dave, N.K.; Lim, T.P.; Cloutier, N.R.

1985-01-01

Ra-226 concentrations were measured in blueberries growing around the Stanrock uranium tailings area near Elliot Lake, Ontario, Canada. Elevated levels of total Ra-226 ranging between 20 to 290 mBq g -1 were observed in samples collected within 500 m from the tailings. Highest levels, approx. 285 mBq g -1 , were observed in a sample collected on a tailings spill. For sites located more than 500 m away in the upwind direction, and those situated at distances greater than 1 km downwind from the waste pile, the total Ra-226 concentrations approached background levels which were measured as 2 to 6 mBq g -1 . Approximately 17% of the total Ra-226 measured was removable by washing the samples with distilled water. Wind dispersal of the tailings material and its deposition in the form of dust on blueberries was believed to be responsible for the external contamination. Based on the ICRP recommended dose limits for oral intake of Ra-226, it was calculated that approximately 160 kg a -1 , 3350 kg a -1 and 47 kg a -1 of washed blueberries from inside and outside the influenced zone, and from the tailings spill site, respectively, would need to be consumed before the individual annual limit for the general public was exceeded. (author)

Uranium and thorium deposits of Northern Ontario

International Nuclear Information System (INIS)

Robertson, J.A.; Gould, K.L.

1983-01-01

This, the second edition of the uranium-thorium deposit inventory, describes briefly the deposits of uranium and/or thorium in northern Ontario, which for the purposes of this circular is defined as that part of Ontario lying north and west of the Grenville Front. The most significant of the deposits described are fossil placers lying at or near the base of the Middle Precambrian Huronian Supergroup. These include the producing and past-producing mines of the Elliot Lake - Agnew Lake area. Also included are the pitchblende veins spatially associated with Late Precambrian (Keweenawan) diabase dikes of the Theano Point - Montreal River area. Miscellaneous Early Precambrian pegmatite, pitchblende-coffinite-sulphide occurrences near the Middle-Early Precambrian unconformity fringing the Lake Superior basin, and disseminations in diabase, granitic rocks, alkalic complexes and breccias scattered throughout northern Ontario make up the rest of the occurrences

Surficial origin of North American pitchblende and related uranium deposits

International Nuclear Information System (INIS)

Langford, F.F.

1977-01-01

The ubiquitous association of pitchblende uranium deposits with terrestrial sediments is believed to be the natural result of formation of the orebodies by surficial processes operating under continental conditions. The major uranium deposits of North America illustrate this. The quartz-pebble conglomerate uranium deposits of Elliot Lake, Ontario, have thorium-rich uranium minerals that indicate a detrital origin. With the development of an oxygenic atmosphere before 1,700 m.y. ago, uranium was transported in solution in meteoric surface and near-surface ground water, and produced pitchblende veins in fractures in the basement and in lava flows in terrestrial environments. This accounts for the closee association of fluvial sediments with the pitchblende deposits at Beaverlodge, Rabbit Lake, Baker Lake, and Great Bear Lake, Canada. The development of land plants about 300 m.y. ago produced favorable environments within the terrestrial sandstones themselves, and resulted in the tabular uranium orebodies of the Colorado Plateau. The close relation of tabular orebodies to sedimentation is apparent when compared to recent fluvial sedimentation. In Wyoming, the stratigraphic restriction of the boundary-roll deposits to a few zones in Eocene rocks results from their being remobilized tabular deposits

The uranium deposits of Ontario

International Nuclear Information System (INIS)

Robertson, J.A.

1981-01-01

The principal types of uranium deposits in Ontario are carbonatites and fenites, alkalic volcanic rocks, pegiatites, calc-silicate rocks, pyritic quartz-pebble conglomerates, polymictic conglomerates and some pelitic rocks, and various 'pitchblende' deposits including late Precambrian unconformities, possibly late Precambrian diabase dikes, and other unconformities: carbonates, sandstones, lignites, and semi-pelitic rocks of middle and upper Precambrian age. Only red unzoned pegmatite and the pyritic quartz-pebble conglomerate have supported production. Ontario reasonably assured and estimated resources in the economic and subeconomic categories in 1977 amounted to 553 000 tonnes U, and 1977 production was 4000 tonnes U. Measured, indicated, and inferred resources in the Elliot Lake - Agnew Lake area are at least 400 000 tonnes U. The latter deposits are also a significant thorium resource. Geological features reflecting major changes in physics and chemistry are prime controls on distribution of uranium deposits. Geological province and subprovince boundaries, major faults, higher metamorphic grades, domain boundaries related to quartz monzonite batholiths, alkalic complexes, and the distribution of carbonate rocks are examples of such geological features

Cigar Lake, an original method for an exceptional deposit

International Nuclear Information System (INIS)

Caleix, C.

1997-01-01

In 1976, the discovery of the high grade Deposit at Cluff Lake in the north of the province of Saskatchewan (Canada) opened new prospects in uranium deposits, which in turn quickly led to the discovery of exceptional deposits both in terms of grade (up 10 % in metal uranium) and tonnage (150, 000 tons of metal per deposit and more). Among these deposits are Key Lake, Cigar Lake, Midwest, MacClean, and more recently, Mac Arthur. These discoveries as well as future ones make the north of Saskatchewan the world's greatest and most interesting uranium-producing province. (authors)

Sulphate deposition by precipitation into Lake Ontario

Energy Technology Data Exchange (ETDEWEB)

Shaw, R W; Whelpdale, D M

1973-01-01

Measurements of sulphate concentration in precipitation from individual snow storms of several hours duration in the western Lake Ontario region indicate that approximately 9-66 mg/M/sub 2/ of SO/sub 4//sup 2 -/ is being deposited into the lake per storm. This amount is up to several times more than daily average values over long periods found by other workers. Using a mean sulphate concentration of 4 mg/l and an annual accumulation of precipitation of 760 mm, the yearly sulphate deposition by precipitation is about 0.1% of the total mass of sulphate in the lake; however, more significantly, it is of the same order of magnitude as that discharged directly into the lake by industry.

Observations on stake holder confidence related to uranium mine waste management in the elliot lake region

International Nuclear Information System (INIS)

MacDonald, G.

2003-01-01

G. MacDonald, representing the Township of the North Shore and the Standing Environmental Committee (SEC) of the Serpent River Watershed, stated that she is a stakeholder living downstream from 175 million tonnes of acid-generating and radioactive uranium mine tailings. Public confidence in the Elliot Lake region is influenced by past mining issues: worker health concerns and difficulties in obtaining compensation; myriad observations of radium uptake; drinking water contamination issues and inequitable quality standards adverse to the Serpent River First Nation; loss of land use. Government failed to set aside funds for local monitoring of the decommissioned mining region, or to involve citizens in decisions as recommended by the Kirkwood Panel. These failures represent betrayals of trust and furthermore give public confidence little chance to improve. In these circumstances, the affected community has given attention on their own to mid- and long-term issues. At issue is not the current funding or management of the waste storage sites, but rather, creating and maintaining local knowledge and competence to monitor their management over the coming decades and generations. Concerned members of the community note that the federal government 'has done nothing long-lasting to ensure confidence', on this level. They highlight the importance of questions like: 'Do I have the knowledge to act in my best interest?' and 'Who can I trust to protect my interest?' - and have set out to answer them. (author)

Lake Austin uranium deposit, Western Australia

International Nuclear Information System (INIS)

Heath, A.G.; Deutscher, R.L.; Butt, C.R.M.

1984-01-01

The Lake Austin uranium deposit is a calcrete type deposit in the Yilgarn Block, near Cue, in a catchment area of granitoids and greenstones. The uranium is in valley fill and the sediments of the Lake Austin playa. The mineralization occurs over 1 to 6 meter thickness close to the water table in calcrete overlying clays and/or weathered bedrock. The principal uranium mineral is carnotite. Waters in nearby channels have an uranium content of over 30 ppb. The chloride content of the water increases downstream in the nearby drainages, as does the uranium and vanadium content. (author)

Elliot Lake study: factors affecting the uranium mine working environment prior to the introduction of current ventilation practices

International Nuclear Information System (INIS)

1985-03-01

A study was carried out to assist in the retrospective assessment of the underground environment that existed in the Elliot Lake uranium mines in the late 1950's and early 1960's. The environmental conditions and work practices of the late 1950's were established by a combination of literature review and interviews with veteran miners. The practices of the 1950's were imitated in a pilot raise, and extensive measurements of the radiation environment were made. Realistic values of radon and thoron daughter production and removal rates were obtained. The computer model demonstrated that it could reproduce all the observed features of the radiation environment given realistic input parameters. A realistic time and space dependent computer model was used to calculate and compare the average expsoure of the miner in the 1950's with the exposure that would be expected from contemporary measurements, and with that of the miner today. The calculated exposure is about half of that expected from contemporary measurements, which gives assurance that previous exposures for pilot raise miners were not underestimated. Relative to today's miner, the average exposure of the typical raise miner of the 1950's is estimated as three times higher for radon daughters, equal for thoron daughters, equal for exposure to gamma radiation, but much higher for uranium and quartz dust

Atmospheric nitrogen deposition influences denitrification and nitrous oxide production in lakes.

Science.gov (United States)

McCrackin, Michelle L; Elser, James J

2010-02-01

Microbially mediated denitrification is an important process that may ameliorate the effects of nitrogen (N) loading by permanently removing excess N inputs. In this study, we measured the rate of denitrification and nitrous oxide (N2O) production during denitrification in sediments from 32 Norwegian lakes at the high and low ends of a gradient of atmospheric N deposition. Denitrification and N2O production rates averaged 41.7 and 1.1 micromol N x m(-2) x h(-1), respectively, for high-deposition lakes. There was no detectable denitrification or N2O production in low-deposition lakes. Epilimnetic nitrate concentration was strongly correlated with denitrification rate (r2 = 0.67). We also measured the denitrification rate in response to experimental additions of organic carbon, nitrate, and phosphorus. Experimental nitrate additions stimulated denitrification in sediments of all lakes, regardless of N deposition level. In fact, the rate of denitrification in nitrate-amended treatments was the same magnitude for lakes in both deposition areas. These findings suggest that lake sediments possess considerable capacity to remove nitrate and that this capacity has not been saturated under conditions of chronic N loading. Further, nitrous oxide was nearly 3% of the total gaseous product during denitrification in high-deposition lakes, a fraction that is comparable to polluted marine sediments. Our findings suggest that, while lakes play an important role in N removal in the landscape, they may be a source of N2O emissions, especially in areas subject to elevated N inputs.

Evidence for the Importance of Atmospheric Nitrogen Deposition to Eutrophic Lake Dianchi, China

Science.gov (United States)

Zhan, X.; Bo, Y.; Zhou, F.; Liu, X.; Paerl, H. W.; Shen, J.; Wang, R.; Li, F. R.; Tao, S.; Yanjun, D.; Tang, X.

2017-12-01

Elevated atmospheric nitrogen (N) deposition has significantly influenced aquatic ecosystems, especially with regard to their N budgets and phytoplankton growth potentials. Compared to a considerable number of studies on oligotrophic lakes and oceanic waters, little evidence for the importance of N deposition has been generated for eutrophic lakes, even though emphasis has been placed on reducing external N inputs to control eutrophication in these lakes. Our high-resolution observations of atmospheric depositions and riverine inputs of biologically reactive N species into eutrophic Lake Dianchi (the sixth largest freshwater lake in China) shed new light onto the contribution of N deposition to total N loads. Annual N deposition accounted for 15.7% to 16.6% of total N loads under variable precipitation conditions, 2-fold higher than previous estimates (7.6%) for the Lake Dianchi. The proportion of N deposition to total N loads further increased to 27-48% in May and June when toxic blooms of the ubiquitous non-N2 fixing cyanobacteria Microcystis spp. are initiated and proliferate. Our observations reveal that reduced N (59%) contributes a greater amount than oxidized N to total N deposition, reaching 56-83% from late spring to summer. Progress toward mitigating eutrophication in Lake Dianchi and other bloom-impacted eutrophic lakes will be difficult without reductions in ammonia emissions and subsequent N deposition.

Factors associated with the deposition of Cladophora on Lake Michigan beaches in 2012

Science.gov (United States)

Riley, Stephen C.; Tucker, Taaja R.; Adams, Jean V.; Fogarty, Lisa R.; Lafrancois, Brenda Moraska

2015-01-01

Deposition of the macroalgae Cladophora spp. was monitored on 18 beaches around Lake Michigan during 2012 at a high temporal frequency. We observed a high degree of spatial variability in Cladophora deposition among beaches on Lake Michigan, even within local regions, with no clear regional pattern in the intensity of Cladophora deposition. A strong seasonal pattern in Cladophora deposition was observed, with the heaviest deposition occurring during mid-summer. Several beaches exhibited high temporal variability in Cladophora deposition over short time scales, suggesting that drifting algal mats may be extremely dynamic in nearshore environments of the Great Lakes. Cladophora deposition on Lake Michigan beaches was primarily related to the presence of nearshore structures, local population density, and nearshore bathymetry. There was relatively little evidence that waves, winds, or currents were associated with Cladophora deposition on beaches, but this may be due to the relatively poor resolution of existing nearshore hydrodynamic data. Developing a predictive understanding of beach-cast Cladophora dynamics in Great Lakes environments may require both intensive Cladophora monitoring and fine-scale local hydrodynamic modeling efforts.

Exploration of the Key Lake uranium deposits, Saskatchewan, Canada

International Nuclear Information System (INIS)

Gatzweiler, R.; Schmeling, B.; Tan, B.

1981-01-01

In 1969, one year after the discovery of the Rabbit Lake uranium deposit, exploration started in the Key Lake area as part of a major uranium rush into Northern Saskatchewan, and within the frame of a joint venture. The area was not chosen on the basis of a particular metallogenetic concept. The lack of exploratory success in 1969 and 1970, together with the introduction in March 1970 of foreign ownership restrictions for uranium mining in Canada, discouraged six of the nine companies forming the original joint venture. In 1971 the three remaining companies decided to continue under a redefined concept, based on the knowledge obtained from the Rabbit Lake deposit (Uranerz had acquired a 49% share in 1970) and from the newly discovered uranium deposits in the Pine Creek Geosyncline, Australia. In the same year, exploration work resulted in the discovery of two high-grade mineralized boulders and significant radioactive and geochemical anomalies 5 km SW of Key Lake deposits. Subsequent exploration, aimed at finding the source of the mineralized boulders, comprised geological, glacial geological and ground radiometric surveys, boulder tracing, air-photo interpretation, lake sediment and muskeg sampling surveys, radon surveys, ground magnetic, gravity, electromagnetic and IP surveys, and drilling. The systematic exploration efforts resulted in the discovery of the Gaertner ore body in July 1975 and the Deilmann ore body in June 1976, where glacial geology, lake sediment sampling, magnetic and electromagnetic surveys were the key methods in defining the drilling targets. Three further years and a total of about 2400 drillholes were needed to fully delineate the two ore bodies. (author)

Geochemistry of the Cigar Lake uranium deposit: XPS studies

International Nuclear Information System (INIS)

Sunder, S.; Cramer, J.J.; Miller, N.H.

1996-01-01

Samples of uranium ore from the Cigar Lake deposit in northern Saskatchewan, Canada, were analyzed using XPS. High-resolution spectra were recorded for the strongest bands of the major elements (U 4f, C 1 s, O 1 s, Pb 4 f, S 2 p, Cu 2 p, Fe 2 p, and the valence region (0-20 eV)) to obtain chemical state information for these samples. In general, the U VI /U IV ratio was very low, i.e., much less than 0.5, the threshold for the oxidative dissolution of UO 2 . The low values of the U VI /U IV ratio observed for samples from the Cigar Lake deposit indicate thermodynamic stability of the uranium ore in the reduced aqueous environment. Similarities between the disposal vault envisaged in the Canadian Nuclear Fuel Waste Management Program and the Cigar Lake deposit suggest that, if geochemical conditions in the vault were to be similar to those in the deposit, the long-term dissolution of UO 2 fuel would be very minimal. (orig.)

contaminant migration in a sand aquifer near an inactive uranium tailings impoundment, Elliot Lake, Ontario

International Nuclear Information System (INIS)

Morin, K.A.; Cherry, J.A.

1982-01-01

An investigation of the movement of contaminated groundwater from inactive uranium tailings through a sand aquifer is being conducted at the Nordic Main tailings impoundment near Elliot Lake, Ontario. During 1979 and 1980, multilevel bundle-type piezometers were installed at several locations around the edge of the tailings impoundment. Chemical analysis of water samples from the bundle piezometers indicate that a major contaminant plume extends outward through a sand aquifer from the southeastern part of the Nordic Main impoundment dam. In the vincinity of the contaminant plume, the sand aquifer varies in thickness from about 9 to 15 m. The plume has two distinct segments, referred to as the inner core and the outer zone. The inner core, which has a pH of 4.3-5.0 and extends about 15 m from the foot of the tailings dam, contains several grams per litre of iron and sulfate, and tens of pCi/L of 226 Ra and 210 Pb. Water levels in piezometers within the inner core show that groundwater is moving horizontally, away from the tailings impoundment, with a velocity of up to several hundred metres per year. The outer zone, which extends a few hundred metres downgradient from the dam, is characterized by hundreds to thousands of milligrams per litre of iron and sulfate, less than 15pCi/L of 226 Ra, and a pH greater than 5.7. Comparison of 1979 and 1980 data shows that the front of the inner core is advancing a few metres per year, which is less than a few percent of the groundwater velocity. This retardation of movement of the inner core is caused by neutralization of the acidic water as a result of dissolution of calcium carbonate in the sand. With the rise in pH, precipitation of iron carbonate and possibly some iron hydroxide occurs and the contaminants of main concern such as 226 Ra, 210 Pb, and uranium are removed from solution by adsorption or coprecipitation

Quantifying aquatic insect deposition from lake to land.

Science.gov (United States)

Dreyer, Jamin; Townsend, Philip A; Hook, James C; Hoekman, David; Vander Zanden, M Jake; Gratton, Claudio

2015-02-01

Adjacent ecosystems are influenced by organisms that move across boundaries, such as insects with aquatic larval stages and terrestrial adult stages, which transport energy and nutrients from water to land. However, the ecosystem-level effect of aquatic insects on land has generally been ignored, perhaps because the organisms themselves are individually small. At the naturally productive Lake Mývatn, Iceland, we used two readily measured quantities: total insect emergence from water and relative insect density on land, to demonstrate an approach for estimating aquatic insect deposition (e.g., kg N x m(-2) x yr(-1)) to shore. Estimates from emergence traps between 2008 and 20.11 indicated a range of 0.15-3.7 g x m(-2) x yr(-1), or a whole-lake emergence of 3.1-76 Mg/yr; all masses are given as dry mass. Using aerial infall trap measurements of midge relative abundance over land, we developed a local-maximum decay function model to predict proportional midge deposition with distance from the lake. The dispersal model predicted midge abundance with R2 = 0.89, a pattern consistent among years, with peak midge deposition occurring 20-25 m inland and 70% of midges deposited within 100 m of shore. During a high-midge year (2008), we estimate midge deposition within the first 50 m of shoreline to be 100 kg xha(-1) x yr(-1), corresponding to inputs of 10 kg N x ha(-1) x yr(-1) and 1 kg P x ha(-1) x yr(-1), or about three to five times above background terrestrial N deposition rates. Consistent with elevated N input where midges are most dense, we observed that soil available nitrate in resin bags decreases with increasing distance from the lake. Our approach, generalizable to other systems, shows that aquatic insects can be a major source of nutrients to terrestrial ecosystems and have the capacity to significantly affect ecosystem processes.

Modeling the global atmospheric transport and deposition of mercury to the Great Lakes

Directory of Open Access Journals (Sweden)

Mark D. Cohen

2016-07-01

Full Text Available Abstract Mercury contamination in the Great Lakes continues to have important public health and wildlife ecotoxicology impacts, and atmospheric deposition is a significant ongoing loading pathway. The objective of this study was to estimate the amount and source-attribution for atmospheric mercury deposition to each lake, information needed to prioritize amelioration efforts. A new global, Eulerian version of the HYSPLIT-Hg model was used to simulate the 2005 global atmospheric transport and deposition of mercury to the Great Lakes. In addition to the base case, 10 alternative model configurations were used to examine sensitivity to uncertainties in atmospheric mercury chemistry and surface exchange. A novel atmospheric lifetime analysis was used to characterize fate and transport processes within the model. Model-estimated wet deposition and atmospheric concentrations of gaseous elemental mercury (Hg(0 were generally within ∼10% of measurements in the Great Lakes region. The model overestimated non-Hg(0 concentrations by a factor of 2–3, similar to other modeling studies. Potential reasons for this disagreement include model inaccuracies, differences in atmospheric Hg fractions being compared, and the measurements being biased low. Lake Erie, downwind of significant local/regional emissions sources, was estimated by the model to be the most impacted by direct anthropogenic emissions (58% of the base case total deposition, while Lake Superior, with the fewest upwind local/regional sources, was the least impacted (27%. The U.S. was the largest national contributor, followed by China, contributing 25% and 6%, respectively, on average, for the Great Lakes. The contribution of U.S. direct anthropogenic emissions to total mercury deposition varied between 46% for the base case (with a range of 24–51% over all model configurations for Lake Erie and 11% (range 6–13% for Lake Superior. These results illustrate the importance of atmospheric

Nitrogen deposition effects on diatom communities in lakes from three National Parks in Washington State

Science.gov (United States)

Sheibley, Richard W.; Enache, Mihaela; Swarzenski, Peter W.; Moran, Patrick W.; Foreman, James R.

2014-01-01

The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (−1 year−1 and were variable both within and across the parks. Diatom assemblages in a single sediment core from Hoh Lake (Olympic National Park) displayed a shift to increased relative abundances of Asterionella formosa and Fragilaria tenera beginning in the 1969–1975 timeframe, whereas these species were not found at the remaining (nine) sites. These diatom species are known to be indicative of N enrichment and were used to determine an empirical critical load of N deposition, or threshold level, where changes in diatom communities were observed at Hoh Lake. However, N deposition at the remaining nine lakes does not seem to exceed a critical load at this time. At Milk Lake, also in Olympic National Park, there was some evidence that climate change might be altering diatom communities, but more research is needed to confirm this. We used modeled precipitation for Hoh Lake and annual inorganic N concentrations from a nearby National Atmospheric Deposition Program station, to calculate elevation-corrected N deposition for 1980–2009 at Hoh Lake. An exponential fit to this data was hindcasted to the 1969–1975 time period, and we estimate a critical load of 1.0 to 1.2 kg N ha−1 year−1 for wet deposition for this lake.

Carbonate deposition, Pyramid Lake subbasin, Nevada: 1. Sequence of formation and elevational distribution of carbonate deposits (Tufas)

Science.gov (United States)

Benson, L.

1994-01-01

During the late Quarternary, the elevation of terrace cutting and carbonate deposition in the Pyramid Lake subbasin were controlled by constancy of lake level imposed by spill to adjoining subbasins. Sill elevations are 1177-1183 m (Mud Lake Slough Sill), 1207 m (Emerson Pass Sill), and 1265 m (Darwin Pass Sill). Carbonate deposition was favored by: (1) hydrologic closure, (2) proximity to a source of calcium, (3) elevated water temperature, and (4) a solid substrate. The thickness and aspect of tufa are a function oflake-level dynamics. Relatively thin sheets and pendant sheets were deposited during a rising or falling lake. The upper parts of thick reef-form tufas have a horizontal aspect and were deposited in a lake which was stabilized by spill to the Carson Desert subbasin. The lower parts of the reef-form tufas are thinner and their outer surface has a vertical aspect, indicating that the lower part formed in a receding lake. The thickest and most complete sequences of tufa are mounds that border the Pyramid Lake shore. The tops of the tallest mounds reach the elevation of the Darwin Pass Sill and many mounds have been eroded to the elevations of the Mud Lake Slough Sill of the Emerson Pass Sill. The sequence of tufa formation (from oldest to youngest) displayed in these mounds is: (1) a beachrock containing carbonate-cemented volcanic cobbles, (2) broken and eroded old spheroids that contain thinolitic tufa and an outer rind of dense laminated tufa, (3) large cylindrical (tubular) tufas capped by (4) coatings of old dense tufas, and (5) several generations of old branching tufa commonly associated with thin, platy tufas and coatings of thinolitic tufa, (6) young spheroids that contain poorly oriented young thinolitic tufa in the center and several generations of radially oriented young thinolitic tufas near the outer edge, (7) a transitional thinolite-to-branching tufa, (8) two or more layers of young branching tufa, (9) a 0.5-cm-thick layer of fine

Shifts in lake N: P stoichiometry and nutrient limitation driven by atmospheric nitrogen deposition

Science.gov (United States)

Elser, J.J.; Andersen, T.; Baron, Jill S.; Bergstrom, A.-K.; Jansson, M.; Kyle, M.; Nydick, K.R.; Steger, L.; Hessen, D.O.

2009-01-01

Human activities have more than doubled the amount of nitrogen (N) circulating in the biosphere. One major pathway of this anthropogenic N input into ecosystems has been increased regional deposition from the atmosphere. Here we show that atmospheric N deposition increased the stoichiometric ratio of N and phosphorus (P) in lakes in Norway, Sweden, and Colorado, United States, and, as a result, patterns of ecological nutrient limitation were shifted. Under low N deposition, phytoplankton growth is generally N-limited; however, in high-N deposition lakes, phytoplankton growth is consistently P-limited. Continued anthropogenic amplification of the global N cycle will further alter ecological processes, such as biogeochemical cycling, trophic dynamics, and biological diversity, in the world's lakes, even in lakes far from direct human disturbance.

Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars

Science.gov (United States)

Grotzinger, J. P.; Gupta, S.; Malin, M. C.; Rubin, D. M.; Schieber, J.; Siebach, K.; Sumner, D. Y.; Stack, K. M.; Vasavada, A. R.; Arvidson, R. E.; Calef, F.; Edgar, L.; Fischer, W. F.; Grant, J. A.; Griffes, J.; Kah, L. C.; Lamb, M. P.; Lewis, K. W.; Mangold, N.; Minitti, M. E.; Palucis, M.; Rice, M.; Williams, R. M. E.; Yingst, R. A.; Blake, D.; Blaney, D.; Conrad, P.; Crisp, J.; Dietrich, W. E.; Dromart, G.; Edgett, K. S.; Ewing, R. C.; Gellert, R.; Hurowitz, J. A.; Kocurek, G.; Mahaffy, P.; McBride, M. J.; McLennan, S. M.; Mischna, M.; Ming, D.; Milliken, R.; Newsom, H.; Oehler, D.; Parker, T. J.; Vaniman, D.; Wiens, R. C.; Wilson, S. A.

2015-10-01

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).

Sedimentation rates and depositional processes in Lake Superior from 210Pb geochronology

International Nuclear Information System (INIS)

Evans, J.E.; Johnson, T.C.; Alexander, E.C. Jr.; Lively, R.S.; Eisenreich, S.J.

1981-01-01

Sedimentation rates range from 0.01 to 0.32 cm/yr in 17 sediment box cores from Lake Superior, as determined by 210 Pb geochronology. Shoreline erosion and resuspension of nearshore sediments causes moderate to high (0.05-0.11 cm/yr) sedimentation rates in the western arm of Lake Superior. Sedimentation rates are very high (> 0.15 cm/yr) in marginal bays adjoining Lake Superior; and moderate to very high (0.07-0.19 cm/yr) in open lake regions adjacent to marginal bays. Resuspension of nearshore and shoal top sediments in southern and southeastern Lake Superior by storms is responsible for depositional anomalies in 210 Pb profiles corresponding to 1905, 1916-1918, and 1940 storms. Sedimentation rates are very low (0.01-0.03 cm/yr) in the central basins due to isolation from sediment sources. These data indicate that sedimentation rates and processes vary significantly in different regions of Lake Superior. The sedimentation rates provided by this study, in conjunction with previously-reported sedimentation rates, yield a better understanding of the Lake Superior depositional environment

Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars.

Science.gov (United States)

Grotzinger, J P; Gupta, S; Malin, M C; Rubin, D M; Schieber, J; Siebach, K; Sumner, D Y; Stack, K M; Vasavada, A R; Arvidson, R E; Calef, F; Edgar, L; Fischer, W F; Grant, J A; Griffes, J; Kah, L C; Lamb, M P; Lewis, K W; Mangold, N; Minitti, M E; Palucis, M; Rice, M; Williams, R M E; Yingst, R A; Blake, D; Blaney, D; Conrad, P; Crisp, J; Dietrich, W E; Dromart, G; Edgett, K S; Ewing, R C; Gellert, R; Hurowitz, J A; Kocurek, G; Mahaffy, P; McBride, M J; McLennan, S M; Mischna, M; Ming, D; Milliken, R; Newsom, H; Oehler, D; Parker, T J; Vaniman, D; Wiens, R C; Wilson, S A

2015-10-09

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp). Copyright © 2015, American Association for the Advancement of Science.

Optimizing best management practices to control anthropogenic sources of atmospheric phosphorus deposition to inland lakes.

Science.gov (United States)

Weiss, Lee; Thé, Jesse; Winter, Jennifer; Gharabaghi, Bahram

2018-04-18

Excessive phosphorus loading to inland freshwater lakes around the globe has resulted in nuisance plant growth along the waterfronts, degraded habitat for cold water fisheries, and impaired beaches, marinas and waterfront property. The direct atmospheric deposition of phosphorus can be a significant contributing source to inland lakes. The atmospheric deposition monitoring program for Lake Simcoe, Ontario indicates roughly 20% of the annual total phosphorus load (2010-2014 period) is due to direct atmospheric deposition (both wet and dry deposition) on the lake. This novel study presents a first-time application of the Genetic Algorithm (GA) methodology to optimize the application of best management practices (BMPs) related to agriculture and mobile sources to achieve atmospheric phosphorus reduction targets and restore the ecological health of the lake. The novel methodology takes into account the spatial distribution of the emission sources in the airshed, the complex atmospheric long-range transport and deposition processes, cost and efficiency of the popular management practices and social constraints related to the adoption of BMPs. The optimization scenarios suggest that the optimal overall capital investment of approximately $2M, $4M, and $10M annually can achieve roughly 3, 4 and 5 tonnes reduction in atmospheric P load to the lake, respectively. The exponential trend indicates diminishing returns for the investment beyond roughly $3M per year and that focussing much of this investment in the upwind, nearshore area will significantly impact deposition to the lake. The optimization is based on a combination of the lowest-cost, most-beneficial and socially-acceptable management practices that develops a science-informed promotion of implementation/BMP adoption strategy. The geospatial aspect to the optimization (i.e. proximity and location with respect to the lake) will help land managers to encourage the use of these targeted best practices in areas that

The Lepanto Cu–Au deposit, Philippines: A fossil hyperacidic volcanic lake complex

Science.gov (United States)

Berger, Byron R.; Henley, Richard W.; Lowers, Heather; Pribil, Michael

2014-01-01

Hyperacidic lakes and associated solfatara in active volcanoes are the expression of magmatic gas expansion from source to surface. Here we show for the first time, that the vein system that comprises the ~ 2 Ma high-sulfidation, Lepanto copper–gold deposit in the Mankayan district (Philippines) was associated with a contemporary hyperacidic volcanic lake complex—possibly the first such lake recognized in the geological record. A 15–20‰ difference in sulfur isotopic composition between barite and sulfides and sulfosalts in the vent fumarole encrustations supports the interpretation that SO2-rich volcanic gas vented into the base of the lake and marginal to it and ties the mineralization directly to magmatic gas expansion, fracture propagation, and mineralization that occurred through a series of decompression steps within the feeder fracture network. These data confirm that crater lake environments such as Kawah Ijen (Java, Indonesia) provide modern day analogs of the Lepanto and other high sulfidation Cu–Au depositing environments.We also provide extensive analysis of sulfosalt–sulfide reactions during vein formation within the hyperacidic lake complex. Pyrite ±  silica deposited first at high temperature followed by enargite that preserves the vapor–solid diffusion of, for example, antimony, tin, and tellurium into the vapor from the crystallizing solid. Subsolidus, intra-crystalline diffusion continued as temperature declined. Pyrite and enargite are replaced by Fe-tennantite in the lodes which initially has low Sb/(Sb + As) atomic ratios around 13.5% close to the ideal tennantite formula, but evolves to higher ratios as crystallization proceeds. Fumarole encrustation clasts and sulfosalts in the lake sediment are more highly evolved with a larger range of trace element substitutions, including antimony. Substitution of especially Zn, Te, Ag, and Sn into tennantite records metal and semi-metal fractionation between the expanding magmatic

Trends in the chemistry of atmospheric deposition and surface waters in the Lake Maggiore catchment

Directory of Open Access Journals (Sweden)

M. Rogora

2001-01-01

Full Text Available The Lake Maggiore catchment is the area of Italy most affected by acid deposition. Trend analysis was performed on long-term (15-30 years series of chemical analyses of atmospheric deposition, four small rivers draining forested catchments and four high mountain lakes. An improvement in the quality of atmospheric deposition was detected, due to decreasing sulphate concentration and increasing pH. Similar trends were also found in high mountain lakes and in small rivers. Atmospheric deposition, however, is still providing a large and steady flux of nitrogen compounds (nitrate and ammonium which is causing increasing nitrogen saturation in forest ecosystems and increasing nitrate levels in rivers. Besides atmospheric deposition, an important factor controlling water acidification and recovery is the weathering of rocks and soils which may be influenced by climate warming. A further factor is the episodic deposition of Saharan calcareous dust which contributes significantly to base cation deposition. Keywords: trend, atmospheric deposition, nitrogen, stream water chemistry.

Depositional environments of Late Triassic lake, east-central New Mexico

Energy Technology Data Exchange (ETDEWEB)

Hester, P.M. (Bureau of Land Management, Albuquerque, NM (USA))

1989-09-01

The Redonda Member of the Chinle Formation represents deposition in a large, polymictic lake during the Late Triassic (Norian) in east-central New Mexico. This study documents and defines an extensive lacustrine system situated in western Pangaea which was influenced by both tectonic and climatic events. Areal extent of the lake may have been as much as 5,000 km{sup 2}.

Mud Lake, a modern analog of oil shale deposition in Florida

Energy Technology Data Exchange (ETDEWEB)

Burgess, J.D.

1987-01-01

Mud Lake in north-central Florida was identified by Bradley as an analog of oil shale-type kerogen deposition. This lake supports an abundant diatom and algal flora which is unique in that the accumulating algal ooze does not decay as long as it stays oxygenated. This same material does not nutritionally support many invertebrates, owing to its flocculent consistency and apparent indigestibility, although fish are abundant and an occasional crocodile is found in the lake. Accumulation of the algal ooze is very slow at roughly 1 foot per 52,000 years based on radiocarbon dates. An understanding of oil shale depositional conditions could be translated into a predictive model for location and recognition of hydrocarbon generating source rocks. When oil shales are mentioned the first association is likely to be that with the Eocene Green River Formation of the Western US. Conditions leading to deposition and preservation of this massive quantity of organic debris is difficult to comprehend, but recognition of modern analogs provide an available area for study and comparison.

Lake Sturgeon, Lake Whitefish, and Walleye egg deposition patterns with response to fish spawning substrate restoration in the St. Clair–Detroit River system

Science.gov (United States)

Fischer, Jason L.; Pritt, Jeremy J.; Roseman, Edward; Prichard, Carson G.; Craig, Jaquelyn M.; Kennedy, Gregory W.; Manny, Bruce A.

2018-01-01

Egg deposition and use of restored spawning substrates by lithophilic fishes (e.g., Lake Sturgeon Acipenser fulvescens, Lake Whitefish Coregonus clupeaformis, and Walleye Sander vitreus) were assessed throughout the St. Clair–Detroit River system from 2005 to 2016. Bayesian models were used to quantify egg abundance and presence/absence relative to site-specific variables (e.g., depth, velocity, and artificial spawning reef presence) and temperature to evaluate fish use of restored artificial spawning reefs and assess patterns in egg deposition. Lake Whitefish and Walleye egg abundance, probability of detection, and probability of occupancy were assessed with detection-adjusted methods; Lake Sturgeon egg abundance and probability of occurrence were assessed using delta-lognormal methods. The models indicated that the probability of Walleye eggs occupying a site increased with water velocity and that the rate of increase decreased with depth, whereas Lake Whitefish egg occupancy was not correlated with any of the attributes considered. Egg deposition by Lake Whitefish and Walleyes was greater at sites with high water velocities and was lower over artificial spawning reefs. Lake Sturgeon eggs were collected least frequently but were more likely to be collected over artificial spawning reefs and in greater abundances than elsewhere. Detection-adjusted egg abundances were not greater over artificial spawning reefs, indicating that these projects may not directly benefit spawning Walleyes and Lake Whitefish. However, 98% of the Lake Sturgeon eggs observed were collected over artificial spawning reefs, supporting the hypothesis that the reefs provided spawning sites for Lake Sturgeon and could mitigate historic losses of Lake Sturgeon spawning habitat.

Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

Science.gov (United States)

Nanus, L.; Williams, M.W.; Campbell, D.H.; Tonnessen, K.A.; Blett, T.; Clow, D.W.

2009-01-01

The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park (n = 244 lakes), Grand Teton National Park (n = 106 lakes), Great Sand Dunes National Park and Preserve (n = 11 lakes), Rocky Mountain National Park (n = 114 lakes), and Yellowstone National Park (n = 294 lakes). Lakes that had a high probability of having an ANC concentration 3000 m, with 80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

Anthropogenic mercury deposition to arctic lake sediments

Energy Technology Data Exchange (ETDEWEB)

Hermanson, M.H. [Westchester University, Westchester, PA (United States). Dept. of Health

1998-01-01

The history of atmospheric mercury inputs to remote arctic regions can be measured in lake sediment cores using lead-210 chronology. In the investigation, total mercury deposition is measured in sediments from Imitavik and Annak Lakes on the Belcher Islands in southeastern Hudson Bay, an area in the southern Canadian Arctic with no history of local industrial or agricultural sources of contamination. Both lakes received background and atmospheric inputs of mercury while Annak also received mercury from raw domestic sewage from the Hamlet of Sanikiluaq, a growing Inuit community of about 550 established in the late 1960s. Results from Imitavik show that anthropogenic mercury inputs, apparently transported through the atmosphere, began to appear in the mid-eighteenth century, and continued to the 1990s. Annak had a similar mercury history until the late 1960s when disposal of domestic sewage led to increased sediment and contaminant accumulation. The high input of mercury to Annak confirms that Sanikiluaq residents are exposed to mercury through native food sources. 39 refs., 7 figs., 3 tabs.

Inorganic Nitrogen Deposition and Its Impacts on N:P-Ratios and Lake Productivity

Directory of Open Access Journals (Sweden)

Dag O. Hessen

2013-03-01

Full Text Available The pronounced increase in the cycling and deposition of biologically reactive dissolved inorganic nitrogen (DIN over large areas globally not only cause increased concentrations of DIN in surface waters, but it will also affect nutrient ratios in rivers, lakes and coastal areas. This review addresses the flux and fate of DIN, focusing NO3 in lakes of boreal and alpine catchments. Not only DIN-deposition, but also catchment properties strongly affect the concentrations of NO3 in lakes, as well as NO3:total P (TP ratios. This ratio displays an extreme variability, and does also serve as an indicator of shift between N and P-limitation of aquatic autotrophs. A high share of forests and bogs in the catchment generally decreases NO3:total P ratios, while alpine and subalpine catchments with sparse vegetation cover may have high NO3:total P ratios, especially in regions with high DIN-deposition. Several empirical and experimental studies indicate a shift from an initial N to P-limitation, but for N-limited lakes, an increased growth of phytoplankton, periphytes and macrophytes may be accredited to elevated inputs of DIN. An intensified P-limitation may also be a consequence of elevated DIN-deposition. This P-limitation may again yield higher C:P-ratios in autotrophs with negative impacts on grazers and higher trophic levels.

Prospecting and exploration of the Key Lake uranium deposits, Saskatchewan, Canada

International Nuclear Information System (INIS)

Tan, B.H.

1980-01-01

The research activities which led to the detection of the Key Lake deposit and their model character for uranium prospecting in this area are discussed. The genesis of the ores and the surrounding rocks are described, and the possible genesis of the deposit is discussed on the basis of the present state of knowledge. (HP) [de

Stochastic and cyclic deposition of multiple subannual laminae in an urban lake (Twin Lake, Golden Valley, Minnesota, USA)

Science.gov (United States)

Myrbo, A.; Ustipak, K.; Demet, B.

2013-12-01

Twin Lake, a small, deep, meromictic urban lake in Minneapolis, Minnesota, annually deposits two to 10 laminae that are distinguished from one another by composition and resulting color. Sediment sources are both autochthonous and allochthonous, including pure and mixed laminae of authigenic calcite, algal organic matter, and diatoms, as well as at least three distinct types of sediment gravity flow deposits. Diagenetic iron sulfide and iron phosphate phases are minor components, but can affect color out of proportion to their abundance. We used L*a*b* color from digital images of a freeze core slab, and petrographic smear slides of individual laminae, to categorize 1080 laminae deposited between 1963 and 2010 CE (based on lead-210 dating). Some causal relationships exist between the ten categories identified: diatom blooms often occur directly above the debris of gravity flows that probably disrupt the phosphate-rich monimolomnion and fertilize the surface waters; calcite whitings only occur after diatom blooms that increase calcite saturation. Stochastic events, as represented by laminae rich in siliciclastics and other terrigenous material, or shallow-water microfossils and carbonate morphologies, are the dominant sediment source. The patterns of cyclic deposition (e.g., summer and winter sedimentation) that produce 'normal' varve couplets in some lakes are continually interrupted by these stochastic events, to such an extent that spectral analysis finds only a weak one-year cycle. Sediments deposited before about 1900, and extending through the entire Holocene sequence (~10m) are varve couplets interrupted by thick (20-90 cm) debris layers, indicating that gravity flows were lower in frequency but greater in magnitude before the historical period, probably due to an increased frequency of disturbance under urban land-use.

Detection to the DepositFan Occurring in the Sun Moon Lake Using Geophysical Sonar Data

Science.gov (United States)

Mimi, L.

2014-12-01

Located in central Taiwan, the Sun Moon Lake is an U-shaped basin with the waters capacity for 138.68 × 106m³. The water is input through two underground tunnels from the Wu-Jie dam in the upstream of the Zhuo-shui river. Although the Wu-Jie dam has been trying to keep the tunnels transporting clean water into the lake, the water is still mixed with muds. The silty water brings the deposits accumulating outwards from positions of the tunnel outlets resulting in a deposit fan formed in the lake. To monitor how the fan is accumulated is then very important in terms of environmental issue, tourism and electric power resources. Institute of Oceanography, National Taiwan University therefore conducted projects to use the multi-beam echo sounders to collect bathymetric data, and used the Chirp sub-bottom profiler to explore silted pattern inside the deposit fan. With these data, underwater topographic maps were plotted to observe the shape and internal structure of the fan. Moreover, two sets of data obtained in 2006 and 2012 were used to estimate the siltation magnitude and pattern in the six years period.The multi-beam sounder is Resons Seabat 9001s model; it collects 60 values in each of the swaths positioned by the DGPS method.The sub-bottom profiler is the EdgeTech 3100P Chirp Sonar, its acoustic wave frequency is in 2 ~ 16kHz. The data give the siltation amount in the Sun Moon Lake was around 3× 106 m³, which gives annual siltation rate at 5× 105 m³. The leading edge of the deposit fan has been expanded westwards 2 km from the water outlet since the tunnel was built 70 years ago; however, outside the deposit fan, the siltation shows insignificant amount on the water bottom.In the past few years the siltation mainly occurs outside in the east side of lake, more closer to the water outlets, the terrain had been increased from 744 m to 746 m (748.5 meters is stranded level of the lake).Observing sub-bottom profiler data, we can clearly see the location of the

Origin of the Mariano Lake uranium deposit, McKinley County, New Mexico

International Nuclear Information System (INIS)

Fishman, N.S.; Reynolds, R.L.

1986-01-01

The Mariano Lake uranium deposit, hosted by the Brushy Basin Member of the Jurassic Morrison Formation, occurs in the Smith Lake district of the Grants uranium region, New Mexico. The orebody, contains abundant amorphous organic material, which suggests that it represents a primary-type deposit; however, the orebody is close to a regional reduction-oxidation interface, which suggests that uranium was secondarily redistributed by oxidative processes. Uranium contents correlate positively with organic carbon contents. Petrographic evidence points to uranium residence in amorphous organic material that was postdepositionally introduced in the diagenetic history of the host sandstone. Uranium mineralization was preceded by precipitation of pyrite (δ/sup 34/S values of -11.0 to -38.2 per mil), mixed-layer smectite-illite clays, and quartz and potassium feldspar overgrowths; and also partial dissolution of some detrital feldspars. Alterations associated with uranium mineralization include precipitation of the organic material, microcrystalline quartz, and pyrite and marcasite (δ/sup 34/S values of -29.4 to -41.6 per mil), and the destruction of detrital Fe-Ti oxide grains. Following mineralization, calcite, dolomite, barite, and kaolinite were precipitated, and some iron disulfides were replaced by ferric oxides. Geochemical data and petrographic observations both indicate that the Mariano Lake orebody is a primary-type deposit. Oxidative processes have not noticeably redistributed uranium in the immediate vicinity of the deposit, nor have they greatly modified geochemical characteristics in the ore. Impedance of ground-water flow by local folds and the lower porosity characteristics of ore zones may have helped to preserve the deposit

High-coercivity minerals from North African Humid Period soil material deposited in Lake Yoa (Chad)

Science.gov (United States)

Just, J.; Kroepelin, S.; Wennrich, V.; Viehberg, F. A.; Wagner, B.; Rethemeyer, J.; Karls, J.; Melles, M.

2015-12-01

The Holocene is a period of fundamental climatic change in North Africa. Humid conditions during the so-called African Humid Period (AHP) have favored the formation of big lake systems. Only very few of these lakes persist until today. One of them is Lake Yoa (19°03'N/20°31'E) in the Ounianga Basin, Chad, which maintains its water level by ground water inflow. Here we present the magnetic characteristics together with proxies for lacustrine productivity and biota of a sediment core (Co1240) from Lake Yoa, retrieved in 2010 within the framework of the Collaborative Research Centre 806 - Our Way to Europe (Deutsche Forschungsgemeinschaft). Magnetic properties of AHP sediments show strong indications for reductive diagenesis. An up to ~ 80 m higher lake level is documented by lacustrine deposits in the Ounianga Basin, dating to the early phase of the AHP. The higher lake level and less strong seasonality restricted deep mixing of the lake. Development of anoxic conditions consequently lead to the dissolution of iron oxides. An exception is an interval with high concentration of high-coercivity magnetic minerals, deposited between 7800 - 8120 cal yr BP. This interval post-dates the 8.2 event, which was dry in Northern Africa and probably caused a reduced vegetation cover. We propose that the latter resulted in the destabilization of soils around Lake Yoa. After the re-establishment of humid conditions, these soil materials were eroded and deposited in the lake. Magnetic minerals appear well preserved in the varved Late Holocene sequence, indicating (sub-) oxic conditions in the lake. This is surprising, because the occurrence of varves is often interpreted as an indicator for anoxic conditions of the lake water. However, the salinity of lake water rose strongly after the AHP. We therefore hypothesize that the conservation of varves and absence of benthic organisms rather relates to the high salinity than to anoxic conditions.

Sediment deposition and sources into a Mississippi River floodplain lake; Catahoula Lake, Louisiana

Science.gov (United States)

Latuso, Karen D.; Keim, Richard F.; King, Sammy L.; Weindorf, David C.; DeLaune, Ronald D.

2017-01-01

Floodplain lakes are important wetlands on many lowland floodplains of the world but depressional floodplain lakes are rare in the Mississippi River Alluvial Valley. One of the largest is Catahoula Lake, which has existed with seasonally fluctuating water levels for several thousand years but is now in an increasingly hydrologically altered floodplain. Woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased since major human hydrologic modifications, such as channelization, levee construction, and dredging for improvement of navigation, but it remains unknown what role those modifications may have played in altering lake sedimentation processes. Profiles of thirteen 137Cs sediment cores indicate sedimentation has been about 0.26 cm y− 1 over the past 60 years and has been near this rate since land use changes began about 200 years ago (210Pb, and 14C in Tedford, 2009). Carbon sequestration was low (10.4 g m− 2 y− 1), likely because annual drying promotes mineralization and export. Elemental composition (high Zr and Ti and low Ca and K) and low pH of recent (sediments suggest Gulf Coastal Plain origin, but below the recent sediment deposits, 51% of sediment profiles showed influence of Mississippi River alluvium, rich in base cations such as K+, Ca2 +, and Mg2 +. The recent shift to dominance of Coastal Plain sediments on the lake-bed surface suggests hydrologic modification has disconnected the lake from sediment-bearing flows from the Mississippi River. Compared to its condition prior to hydrologic alterations that intensified in the 1930s, Catahoula Lake is about 15 cm shallower and surficial sediments are more acidic. Although these results are not sufficient to attribute ecological changes directly to sedimentological changes, it is likely the altered sedimentary and hydrologic environment is contributing to the increased dominance of woody vegetation.

Paleolimnological records of nitrogen deposition in shallow, high-elevation lakes of Grand Teton National Park, Wyoming, USA

Science.gov (United States)

Spaulding, Sarah A.; Otu, Megan K.; Wolfe, Alexander P.; Baron, Jill S.

2015-01-01

Reactive nitrogen (Nr) from anthropogenic sources has been altering ecosystem function in lakes of the Rocky Mountains, other regions of western North America, and the Arctic over recent decades. The response of biota in shallow lakes to atmospheric deposition of Nr, however, has not been considered. Benthic algae are dominant in shallow, high-elevation lakes and are less sensitive to nutrient inputs than planktonic algae. Because the benthos is typically more nutrient rich than the water column, shallow lakes are not expected to show evidence of anthropogenic Nr. In this study, we assessed sedimentary evidence for regional Nr deposition, sediment chronology, and the nature of algal community response in five shallow, high-elevation lakes in Grand Teton National Park (GRTE). Over 140 diatom taxa were identified from the sediments, with a relatively high species richness of taxa characteristic of oligotrophic conditions. The diatom assemblages were dominated by benthic taxa, especially motile taxa. The GRTE lakes demonstrate assemblage-wide shifts in diatoms, including 1) synchronous and significant assemblage changes centered on ~1960 AD; 2) pre-1960 assemblages differed significantly from post-1960 assemblages; 3) pre-1960 diatom assemblages fluctuated randomly, whereas post- 1960 assemblages showed directional change; 4) changes in δ15N signatures were correlated with diatom community composition. These results demonstrate recent changes in shallow high18 elevation lakes that are most correlated with anthropogenic Nr. It is also possible, however, that the combined effect of Nr deposition and warming is accelerating species shifts in benthic diatoms. While uncertainties remain about the potential synergy of Nr deposition and warming, this study adds shallow lakes to the growing list of impacted high-elevation localities in western North America.

A socially committed literary work: perspectives on Elliot Zondi’s Insumansumane

Directory of Open Access Journals (Sweden)

N.N. Mathonsi

2005-07-01

Full Text Available In this article Elliot Zondi’s historical drama, “Insumansumane”, is discussed as a committed literary work. The main character, Bhambada, urges his contemporaries to challenge the ideological domination of the apartheid system and to fight for their freedom to the last man, if necessary. According to Elliot Zondi, the 1906 Bhambada Rebellion was caused by a lack of consultation and utter disregard for the feelings of the African majority regarding taxation. The rebellion was also caused by the forceful introduction of Western culture and social values. The play in itself is actually a metaphor for the Zulu people living in the 1980s under the iron rule of President P.W. Botha. In this play the Zulu are urged to live up to the freedom ideals for which their forefathers had been ready to fight and to die. The development of the plot in the play emphasises that the “winds of change” at that time were becoming stronger, causing the undercurrent that was to bring about liberation in 1992 and in 1994.

Prospecting exploration and development of the uranium deposits Key Lake, Canada

International Nuclear Information System (INIS)

Kirchner, G.; Tan, B.H.

1977-01-01

This lecture gives a survey of the methods employed by the Uranerzbergbau-GmbH and Co. KG and the experience gained in connection with prospecting and exploration activities at the uranium deposits in Saskatchewan, illustrated by the case history Key Lake. (orig.) [de

A depositional model for spherulitic carbonates associated with alkaline, volcanic lakes

NARCIS (Netherlands)

Mercedes-Martín, Ramon; Brasier, Alexander T.; Rogerson, Mike; Reijmer, John J.G.; Vonhof, Hubert; Pedley, Martyn

2017-01-01

The South Atlantic Aptian ‘Pre-salt’ reservoirs are formed by a combination of spherulitic carbonates and Mg-rich clays accumulated in volcanic alkaline lake settings with exotic chemistries. So far, outcrop analogues characterised by metre-thick successions deposited in lacustrine scenarios are

Three air quality studies: Great Lakes ozone formation and nitrogen dry deposition; and Tucson aerosol chemical characterization

Science.gov (United States)

Foley, Theresa

(arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, and nickel) in the southern Tucson metropolitan area. A Tucson company that uses beryllium oxide to manufacture thermally conductive ceramics has prompted strong citizen concern. This study found that the study area has good air quality with respect to PM10 and metals, with ambient concentrations meeting US Environmental Protection Agency and World Health Organization standards. Beryllium was detected only once (during a dust storm) and was ascribed to naturally-occurring beryllium in the suspended soil. The third paper (to be submitted to the Journal of Great Lakes Research) studies nitrogen dry deposition over Lake Michigan and Lake Superior. Numerous studies have shown that wet and dry deposition of nitrogen has contributed to the eutrophication of coastal waters and declining productivity of marine fisheries. Nitrogen dry deposition over the Great Lakes themselves, as opposed to the shorelines, has not been documented in the peer-reviewed literature. This paper calculates nitrogen dry deposition over Lake Michigan and Lake Superior, using aircraft measurements from the LADCO Aircraft Study, and finds that over-water, nitrogen dry deposition is a significant source of nitrogen to Lake Michigan and Lake Superior.

Trends in historical mercury deposition inferred from lake sediment cores across a climate gradient in the Canadian High Arctic.

Science.gov (United States)

Korosi, Jennifer B; Griffiths, Katherine; Smol, John P; Blais, Jules M

2018-06-02

Recent climate change may be enhancing mercury fluxes to Arctic lake sediments, confounding the use of sediment cores to reconstruct histories of atmospheric deposition. Assessing the independent effects of climate warming on mercury sequestration is challenging due to temporal overlap between warming temperatures and increased long-range transport of atmospheric mercury following the Industrial Revolution. We address this challenge by examining mercury trends in short cores (the last several hundred years) from eight lakes centered on Cape Herschel (Canadian High Arctic) that span a gradient in microclimates, including two lakes that have not yet been significantly altered by climate warming due to continued ice cover. Previous research on subfossil diatoms and inferred primary production indicated the timing of limnological responses to climate warming, which, due to prevailing ice cover conditions, varied from ∼1850 to ∼1990 for lakes that have undergone changes. We show that climate warming may have enhanced mercury deposition to lake sediments in one lake (Moraine Pond), while another (West Lake) showed a strong signal of post-industrial mercury enrichment without any corresponding limnological changes associated with warming. Our results provide insights into the role of climate warming and organic carbon cycling as drivers of mercury deposition to Arctic lake sediments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Radiocarbon Ages and Environments of Deposition of the Wono and Trego Hot Springs Tephra Layers in the Pyramid Lake Subbasin, Nevada

Science.gov (United States)

Benson, L.V.; Smoot, J.P.; Kashgarian, Michaele; Sarna-Wojcicki, A.; Burdett, J.W.

1997-01-01

Uncalibrated radiocarbon data from core PLC92B taken from Wizards Cove in the Pyramid Lake subbasin indicate that the Trego Hot Springs and Wono tephra layers were deposited 23,200 ?? 300 and 27,300 ??300 14C yr B.P. (uncorrected for reservoir effect). Sedimentological data from sites in the Pyramid Lake and Smoke Creek-Black Rock Desert subbasins indicate that the Trego Hot Springs tephra layer was deposited during a relatively dry period when Pyramid Lake was at or below its spill point (1177 m) to the Winnemucca Lake subbasin. The Wono tephra layer was deposited when lake depth was controlled by spill across Emerson Pass sill (1207 m) to the Smoke Creek-Black Rock Desert subbasin. 18O data from core PLC92B also support the concept that the Trego Hot Springs tephra fell into a relatively shallow Pyramid Lake and that the Wono tephra fell into a deeper spilling lake. ?? 1997 University of Washington.

Canada: The largest uranium producer

International Nuclear Information System (INIS)

Lowell, A.F.

1985-01-01

Despite all the current difficulties, previous erroneous forecasts and other mistakes, the longer term future looks good for uranium mining and for Canada's industry in particular. Saskatchewan continues to offer the most exciting new prospects, the huge and fabulously high grade Cigar Lake deposits being the most spectacular of the recent discoveries. Notwithstanding continuous mining for 30 years from Elliot Lake there still remain there significant uncommitted reserves which can be developed when the market for uranium is in better balance

Critical Loads of Acid Deposition for Wilderness Lakes in the Sierra Nevada (California) Estimated by the Steady-State Water Chemistry Model

Science.gov (United States)

Glenn D. Shaw; Ricardo Cisneros; Donald Schweizer; James O. Sickman; Mark E. Fenn

2014-01-01

Major ion chemistry (2000-2009) from 208 lakes (342 sample dates and 600 samples) in class I and II wilderness areas of the Sierra Nevada was used in the Steady-State Water Chemistry (SSWC) model to estimate critical loads for acid deposition and investigate the current vulnerability of high elevation lakes to acid deposition. The majority of the lakes were dilute (...

Arctic deltaic lake sediments as recorders of fluvial organic matter deposition

Directory of Open Access Journals (Sweden)

Jorien E Vonk

2016-08-01

Full Text Available Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13C, 14C and molecular organic geochemistry (lignin, leaf waxes. High-resolution age models (137Cs, 210Pb of downcore lake sediment records (n=11 along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels. Comparison with earlier published Mackenzie River depth profiles shows that (i lake sediments reflect the riverine surface suspended load, and (ii hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale riverine fluxes and may prove instrumental in shedding light on past behaviour of arctic rivers, as well as how they respond to a changing climate.

The impact of an urban-industrial region on the magnitude and variability of persistent organic pollutant deposition to Lake Michigan.

Science.gov (United States)

Hornbuckle, Keri C; Green, Mark L

2003-09-01

A predictive model for gas-phase PCBs and trans-nonachlor over Lake Michigan has been constructed and the resulting data examined for trends. In this paper, we describe the model results to show how the magnitude and variability of a plume of contaminants from the Chicago area contributes to a highly variable region of net contaminant deposition over the entire lake. For the whole lake, gross annual deposition of PCBs is approximately 3200 kg, although the net annual gas exchange is not significantly different from zero. The data-driven model illustrates that on a daily basis, the net exchange of persistent organic pollutants (POPs) can change from net deposition to net volatilization depending on the area of plume impact. These findings suggest that i) control of urban areas can accelerate the rate of volatilization from lakes; and ii) release of POPs from urban areas is largely a result of volatilization processes.

From lab to field: Geotechnical properties for predicting embankment settlement on Lake Bonneville deposits

International Nuclear Information System (INIS)

Hoagland, K.C.; Sampaco, C.L.; Anderson, L.R.; Caliendo, J.A.; Rausher, L.; Keane, E.

1994-01-01

The results of a laboratory analysis, to determine geotechnical properties of lacustrine Lake Bonneville deposits, within the I-15 corridor of Salt Lake City, Utah, is presented. Laboratory vertical and horizontal consolidation coefficients are compared with those back-calculated from observed, field settlement data and linear relationships established. The results are used to select vertical and horizontal field coefficients and predict settlement rate of an existing embankment, scheduled for enlargement. 27 refs., 9 figs

Inter- and intra-annual chemical variability during the ice-free season in lakes with different flushing rates and acid deposition histories.

Science.gov (United States)

Arnott, Shelley E; Dillon, Peter J; Somers, Keith; Keller, Bill

2003-01-01

Quantifying chemical variability in different lake types is important for the assessment of both chemical and biological responses to environmental change. For monitoring programs that emphasize a large number of lakes at the expense of frequent samples, high variability may influence how representative single samples are of the average conditions of individual lakes. Intensive temporal data from long-term research sites provide a unique opportunity to assess chemical variability in lakes with different characteristics. We compared the intra- and inter-annual variability of four acidification related variables (Gran alkalinity, pH, sulphate concentration, and total base cation concentration) in four lakes with different flushing rates and acid deposition histories. Variability was highest in lakes with high flushing rates and was not influenced by historic acid deposition in our study lakes. This has implications for the amount of effort required in monitoring programs. Lakes with high flushing rates will require more frequent sampling intervals than lakes with low flushing rates. Consideration of specific lake types should be included in the design of monitoring programs.

The Cigar Lake uranium deposit: Analog information for Canada's nuclear fuel waste disposal concept

International Nuclear Information System (INIS)

Cramer, J.J.

1995-05-01

The Cigar Lake uranium deposit, located in northern Saskatchewan, has many features that parallel those being considered within the Canadian concept for disposal of nuclear fuel waste. The study of these natural structures and processes provides valuable insight toward the eventual design and site selection of a nuclear fuel waste repository. The main feature of this analog is the absence of any indication on the surface of the rich uranium ore 450 m below. This shows that the combination of natural barriers has been effective in isolating the uranium ore from the surface environment. More specifically, the deposit provides analog information relevant to the stability of UO 2 fuel waste, the performance of clay-based and general aspects of water-rock interaction. The main geotechnical studies on this deposit focus on the evolution of groundwater compositions in the deposit and on their redox chemistry with respect to the uranium, iron and sulphide systems. This report reviews and summarizes the analog information and data from the Cigar Lake analog studies for the processes and scenarios expected to occur in the disposal system for used nuclear fuel proposed in Canada. (author). 45 refs., 10 figs

Whole-lake algal responses to a century of acidic industrial deposition on the Canadian Shield

International Nuclear Information System (INIS)

Vinebrooke, R.D.; Dixit, S.S.; Graham, M.D.; Gunn, J.M.; Chen, Y.-W.; Belzile, N.

2002-01-01

A century of cultural acidification is hypothesized to have altered algal community structure in boreal lakes. To date, this hypothesis has remained untested because of both the lack of data predating the onset of industrial pollution and incomplete estimates of whole-lake algal community structure. High-pressure liquid chromatography (HPLC) of sedimentary pigments was used to quantify whole-lake algal responses to acid deposition in six boreal lakes located in Killarney Park, Ontario, Canada. Concomitant significant increases in chlorophyll and carotenoid concentrations, diatom-inferred lake acidity, and metal levels since 1900 suggested that algal abundances in four acidified lakes and one small, circumneutral lake were enhanced by aerial pollution. An alternate explanation is that increased acidity and underwater light availability in the acidified lakes shifted algal abundance towards phytobenthos and deepwater phytoplankton, whose pigment signatures were better preserved in the sediments. Taxonomically diagnostic pigment stratigraphies were consistent with shifts in algal community structure towards filamentous green phytobenthos and deepwater phytoflagellates in the acidified lakes. Our findings suggest that decades of aerial pollution have altered the base of foodwebs in boreal lakes, potentially rendering them less resilient to other environmental stressors. (author)

The impact of acid deposition and forest harvesting on lakes and their forested catchments in south central Ontario: a critical loads approach

Directory of Open Access Journals (Sweden)

S. A. Watmough

2002-01-01

Full Text Available The impact of acid deposition and tree harvesting on three lakes and their representative sub-catchments in the Muskoka-Haliburton region of south-central Ontario was assessed using a critical loads approach. As nitrogen dynamics in forest soils are complex and poorly understood, for simplicity and to allow comparison among lakes and their catchments, CLs (A for both lakes and forest soils were calculated assuming that nitrate leaching from catchments will not change over time (i.e. a best case scenario. In addition, because soils in the region are shallow, base cation weathering rates for the representative sub-catchments were calculated for the entire soil profile and these estimates were also used to calculate critical loads for the lakes. These results were compared with critical loads obtained by the Steady State Water Chemistry (SSWC model. Using the SSWC model, critical loads for lakes were between 7 and 19 meq m-2yr-1 higher than those obtained from soil measurements. Lakes and forests are much more sensitive to acid deposition if forests are harvested, but two acid-sensitive lakes had much lower critical loads than their respective forested sub-catchments implying that acceptable acid deposition levels should be dictated by the most acid-sensitive lakes in the region. Under conditions that assume harvesting, the CL (A is exceeded at two of the three lakes and five of the six sub-catchments assessed in this study. However, sulphate export from catchments greatly exceeds input in bulk deposition and, to prevent lakes from falling below the critical chemical limit, sulphate inputs to lakes must be reduced by between 37% and 92% if forests are harvested. Similarly, sulphate leaching from forested catchments that are harvested must be reduced by between 16 and 79% to prevent the ANC of water draining the rooting zone from falling below 0 μeq l-1. These calculations assume that extremely low calcium leaching losses (9–27 μeq l-1 from

Depositional environment of a fan delta in a Vistulian proglacial lake (Skaliska Basin, north-eastern Poland

Directory of Open Access Journals (Sweden)

Woronko Barbara

2013-06-01

Full Text Available The study reconstructed the environment of a fan delta filling the vast end depression of the Skaliska Basin, and its overlying aeolian deposits. The formation of the large fan delta is associated with the presence of an ice-dammed lake functioning during the retreat of the Vistulian Glaciation (MIS 2. The examined material was collected from five boreholes. Sediments were analysed for their granulometric composition and subjected to analyses of frosting and rounding of quartz grains. Grain size analysis showed that the fan delta deposits are built of sand sediments of very low lateral and vertical variability. The fan delta was supplied with fluvioglacial sediments. Accumulation of sediments occurred in shallow water with a very low-gradient slope. The exposed fan delta became a site conducive to aeolian processes after the lake waters fell and the Skaliska Basin depression dried. Dune deposits overlying the fan were affected by short-distance transport so they did not acquire features typical for aeolian deposits.

Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

Science.gov (United States)

Miller, David; Haddon, Elizabeth; Langenheim, Victoria; Cyr, Andrew J.; Wan, Elmira; Walkup, Laura; Starratt, Scott W.

2018-01-01

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin.Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river

Analysis of Atmospheric Nitrate Deposition in Lake Tahoe Using Multiple Oxygen Isotopes

Science.gov (United States)

McCabe, J. R.; Michalski, G. M.; Hernandez, L. P.; Thiemens, M. H.; Taylor, K.; Kendall, C.; Wankel, S. D.

2002-12-01

Lake Tahoe in the Sierra Nevada Mountain Range is world renown for its depth and water clarity bringing 2.2 million visitors per year resulting in annual revenue of \\1.6 billion from tourism. In past decades the lake has suffered from decreased water clarity (from 32 m plate depth to less than 20), which is believed to be largely the result of algae growth initiated by increased nutrient loading. Lake nutrients have also seen a shift from a nitrogen limited to a phosphorous limited system indicating a large increase in the flux of fixed nitrogen. Several sources of fixed nitrogen of have been suggested including surface runoff, septic tank seepage from ground water and deposition from the atmosphere. Bio-available nitrogen in the form of nitrate (NO_{3}$-) is a main component of this system. Recent studies have estimated that approximately 50% of the nitrogen input into the lake is of atmospheric origin (Allison et al. 2000). However, the impact and magnitude of atmospheric deposition is still one of the least understood aspects of the relationship between air and water quality in the Basin (TRPA Threshold Assessment 2002). The utility of stable isotopes as tracers of nitrate reservoirs has been shown in several studies (Bohlke et al. 1997, Kendall and McDonnell 1998, Durka et al. 1994). Stable nitrogen (δ15N) and oxygen (δ18O) isotopes have been implemented in a dual isotope approach to characterize the various nitrate sources to an ecosystem. While δ18O distinguishes between atmospheric and soil sources of nitrate, processes such as denitrification can enrich the residual nitrate in δ18O leaving a misleading atmospheric signature. The benefit of δ15N as a tracer for NO3- sources is the ability to differentiate natural soil, fertilizer, and animal or septic waste, which contain equivalent δ18O values. The recent implementation of multiple oxygen isotopes to measure Δ17O in nitrate has proven to be a more sensitive tracer of atmospheric deposition. The

Spatial and Temporal Variability of Dust Deposition in the San Juan Mountains, CO: A Network of Late Holocene Lake Sediment Records

Science.gov (United States)

Arcusa, S.; Routson, C.; McKay, N.

2017-12-01

Millions of stakeholders living in the arid southwestern US rely on snowmelt from the San Juan Mountains of Colorado. However, dust deposition on snow accelerates snowmelt, challenging water management. Dustiness in the southwestern US is primarily mediated by drought, which is projected to increase in frequency and severity. Over the past several millennia, multidecadal-length megadroughts are hypothesized to have enhanced regional dustiness. These past megadroughts were more frequent during the Roman (ca. 1-400 CE) and Medieval (ca. 800-1300 CE) time periods and were similar in duration and severity to those projected for the future. Developing an understanding of the temporal and spatial patterns of past dust deposition in the San Juan Mountains will help inform adaptation strategies for future droughts. A network of short sediment cores from six alpine lakes in the San Juan Mountains were collected in 2016 and 2017 to investigate the spatial patterns of dust deposition. The range in lake basin characteristics in the network, such as catchment size, helps to constrain the influence of secondary dust deposition. Grain size analysis and X-ray Fluorescence were combined with radiocarbon dating to trace the temporal patterns in dust flux over the Late Holocene (the last 2000 years). The End-member Modelling Algorithm (EMMA) was used to estimate the dust proportion in the lake sediment, distinguishing from locally derived catchment material. Comparisons to modern dust-on-snow samples were made to identify the dust size distribution. The results show that deposition trends were not uniform between the south-eastern and north-western San Juans, with increasing trends towards the present in the former, possibly reflecting a shift in dust sources associated with changes in wind speed and direction. Dust levels greater than long term averages were recorded during the Medieval and Roman periods. The network also showed the influence of lake basin parameters, such as the

36Cl production and mobility in the Cigar Lake uranium deposit

International Nuclear Information System (INIS)

Cornett, R.J.; Fabryka-Martin, J.; Cramer, J.J.; Andrew, H.R.; Koslowsky, V.T.

2010-01-01

Can accelerator mass spectrometry (AMS) studies validate risk assessments of the long-term behaviour of contaminants such as radionuclides? AMS measurements on samples from the 1.3 billion-year-old Cigar Lake uranium ore deposit provide one approach to address this question. In Cigar Lake, elevated concentrations of uranium enhance the in situ neutron flux that produces 36 Cl and other radionuclides. We calculated the production of 36 Cl using a Monte Carlo neutron transport code. We then tested for the loss of 36 Cl from ore samples collected from an 8 m stratigraphic section through the deposit by comparing the predicted values (assuming equilibrium between production and decay) with the concentrations measured by AMS. The 36 Cl:Cl atom ratios within the ore were more than two orders of magnitude higher than in the surrounding host rock and ranged from 4 to 64 x 10 -12 . The 36 Cl concentrations in the ore, rock, clay and fracture infilling minerals all agree with the values predicted by the Monte Carlo simulations. We conclude that 36 Cl has very limited mobility. Even in matrix adjacent to more permeable fractures, there is no evidence that the measured isotopic ratios deviate significantly from the predicted values.

Modern processes of palynomorph deposition at lakes of the northern region of the Rio de Janeiro State, Brazil.

Science.gov (United States)

Luz, Cynthia F P da; Barth, Ortrud M; Silva, Cleverson G

2010-09-01

Palynological analysis of pollen, Pteridophyta spores and algae deposited in the superficial sediments at Lagoa de Cima and Lagoa do Campelo Lakes, located in the north of Rio de Janeiro state, was used to determine the spatial variation of the palynomorphs deposition. A total of 67 pollen types were identified at Lagoa de Cima, with an expressive contribution of regional arboreous taxa, hydrophytes and ruderal plants of the pastureland. The depositional pattern of palynomorphs depends on the fluvial leakage, the proximity of the local sedimentation to the inlet of the Imbé and Urubu Rivers and the bathymetry of lake bottom. The highest concentrations of palynomorphs were observed in the decentralized and less deeper area, without the interference of the northeastern wind. At Lagoa do Campelo, a total of 58 pollen types were identified, among which the majority of the pollen grains came from hydrophytes, with the highest concentrations found along the northeastern shore. The southeastern shore showed high percentages of pollen and spores with degraded exine and mechanical damage, due to the transport through the lake by the currents caused by the wind, confirmed by the depositional trend of damaged palinomorphs along the same direction as the prevailing winds.

Christmas Island lagoonal lakes, models for the deposition of carbonate–evaporite–organic laminated sediments

OpenAIRE

Trichet , Jean; Défarge , Christian; Tribble , J.; Tribble , G.W.; Sansone , F.J.

2001-01-01

The atoll of Christmas Island (now known as Kiritimati) in the Kiribati Republic (Central Pacific) lies at about 2°N in the intertropical convergence zone. Much of the surface area of the atoll (ca. 360 km2) is occupied by numerous lakes in which carbonate, evaporite (calcium sulfate, halite) and organic layers are deposited. Observations suggest that deposition of these different laminae is controlled by climatic and biologic factors. It is thought that periodic climatic variations, such as ...

Holocene Lake-Level Fluctuations of Lake Aricota, Southern Peru

Science.gov (United States)

Placzek, Christa; Quade, Jay; Betancourt, Julio L.

2001-09-01

Lacustrine deposits exposed around Lake Aricota, Peru (17° 22‧S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (<350 yr). Diatomites associated with highstands several meters above the modern lake level indicate wet episodes. Maximum Holocene lake level was attained before 6100 14C yr B.P. and ended ∼2700 14C yr B.P. Moderately high lake levels occurred at 1700 and 1300 14C yr B.P. The highstand at Lake Aricota during the middle Holocene is coeval with a major lowstand at Lake Titicaca (16°S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes.

Depth of cinder deposits and water-storage capacity at Cinder Lake, Coconino County, Arizona

Science.gov (United States)

Macy, Jamie P.; Amoroso, Lee; Kennedy, Jeff; Unema, Joel

2012-01-01

The 2010 Schultz fire northeast of Flagstaff, Arizona, burned more than 15,000 acres on the east side of San Francisco Mountain from June 20 to July 3. As a result, several drainages in the burn area are now more susceptible to increased frequency and volume of runoff, and downstream areas are more susceptible to flooding. Resultant flooding in areas downgradient of the burn has resulted in extensive damage to private lands and residences, municipal water lines, and roads. Coconino County, which encompasses Flagstaff, has responded by deepening and expanding a system of roadside ditches to move flood water away from communities and into an area of open U.S. Forest Service lands, known as Cinder Lake, where rapid infiltration can occur. Water that has been recently channeled into the Cinder Lake area has infiltrated into the volcanic cinders and could eventually migrate to the deep regional groundwater-flow system that underlies the area. How much water can potentially be diverted into Cinder Lake is unknown, and Coconino County is interested in determining how much storage is available. The U.S. Geological Survey conducted geophysical surveys and drilled four boreholes to determine the depth of the cinder beds and their potential for water storage capacity. Results from the geophysical surveys and boreholes indicate that interbedded cinders and alluvial deposits are underlain by basalt at about 30 feet below land surface. An average total porosity for the upper 30 feet of deposits was calculated at 43 percent for an area of 300 acres surrounding the boreholes, which yields a total potential subsurface storage for Cinder Lake of about 4,000 acre-feet. Ongoing monitoring of storage change in the Cinder Lake area was initiated using a network of gravity stations.

Response of lake chemistry to atmospheric deposition and climate in selected Class I wilderness areas in the western United States, 1993-2009

Science.gov (United States)

Mast, M. Alisa

2011-01-01

The U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Forest Service, Air Resource Management, conducted a study to evaluate long-term trends in lake-water chemistry for 64 high-elevation lakes in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming during 1993 to 2009. Understanding how and why lake chemistry is changing in mountain areas is essential for effectively managing and protecting high-elevation aquatic ecosystems. Trends in emissions, atmospheric deposition, and climate variables (air temperature and precipitation amount) were evaluated over a similar period of record. A main objective of the study was to determine if changes in atmospheric deposition of contaminants in the Rocky Mountain region have resulted in measurable changes in the chemistry of high-elevation lakes. A second objective was to investigate linkages between lake chemistry and air temperature and precipitation to improve understanding of the sensitivity of mountain lakes to climate variability.

Carbonate deposition, Pyramid Lake subbasin, Nevada: 3. The use of87Sr values in carbonate deposits (tufas) to determine the hydrologic state of paleolake systems

Science.gov (United States)

Benson, L.; Peterman, Z.

1996-01-01

Sierran rivers that discharge to the Lahontan basin have much lower (???4.5%o) ??87Sr values than the Humboldt River which drains northeastern Nevada. The ??87Sr values of tufas deposited during the last lake cycle were used to determine when Humboldt derived Sr entered the Pyramid Lake subbasin. Prior to ~ 15,000 yr B.P., the Humboldt River flowed to the Smoke Creek-Black Rock Desert subbasin. During the recession of Lake Lahontan, the Humboldt River diverted to the Carson Desert subbasin. This study has demonstrated that 87Sr can be used to determine drainage histories of multi-basin lake systems if the ??87Sr values of rivers that discharge to the basins are sufficiently different. ?? 1995 Elsevier Science B.V. All rights reserved.

Studies of dry deposition of trace elements and diesel soot onto Lake Michigan and the Chesapeake Bay

International Nuclear Information System (INIS)

Ondov, J.M.; Caffrey, P.F.; Suarez, A.E.; Han, M.; Borgoul, P.V.

1995-01-01

As part of the Atmospheric Exchange Over Lakes and Oceans Study (AEOLOS) study, the University of Maryland participated in four intensive field campaigns, three on Lake Michigan (LM) and one on the Chesapeake Bay (CB), to determine the size distributions of potentially toxic elemental aerosol constituents, determine their sources, and their dry deposition loadings to surface waters. The work further seeks to elucidate the relative importance of constituents of fine- and coarse particles, as differentiation of these modes is essential to the eventual formation of control strategies. Unique components of the UMCP studies include (1) resolution of toxic elemental components of aerosol particles depositing to LM and CB by particle size and by source and (2) a Lake-wide evaluation of the importance of fine and coarse particle deposition to inorganic contamination of LM surface waters. In addition, a unique component of the Baltimore Study was the application of a sensitive iridium tracer to intentionally tag emissions form the City of Baltimore's sanitation truck fleet to tag the Baltimore urban plume and to determine the atmospheric behavior of diesel soot particles, a major source of urban carbon aerosol and the principle carrier of toxic polynuclear aromatic hydrocarbons. The work encompasses results for >40 elements by X-ray fluorescence and instrumental neutron activation analyses of more than 700 individual size-segregated aerosol, deposition, urban dust, and surface-water-suspended particulate samples. An overview of the results of these studies will be presented

Polycyclic aromatic hydrocarbon (PAH) deposition to and exchange at the air-water interface of Luhu, an urban lake in Guangzhou, China

International Nuclear Information System (INIS)

Li Jun; Cheng Hairong; Zhang Gan; Qi Shihua; Li Xiangdong

2009-01-01

Urban lakes are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs from wet and dry atmospheric deposition. Little was reported on the seasonal patterns of atmospheric deposition of PAHs under Asian monsoon climate. Bulk (dry + wet) particle deposition, air-water diffusion exchange, and vapour wet deposition of PAHs in a small urban lake in Guangzhou were estimated based on a year-round monitoring. The total PAH particle deposition fluxes observed were 0.44-3.46 μg m -2 day -1 . The mean air-water diffusive exchange flux was 20.7 μg m -2 day -1 . The vapour deposition fluxes of PAHs ranged 0.15-8.26 μg m -2 day -1 . Remarkable seasonal variations of particulate PAH deposition, air-water exchange fluxes and vapour wet deposition were influenced by seasonal changes in meteorological parameters. The deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season. - The PAH deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season

Glacial-interglacial variations of microbial communities in permafrost and lake deposits in the Siberian Arctic

Science.gov (United States)

Mangelsdorf, Kai; Bischoff, Juliane; Gattinger, Andreas; Wagner, Dirk

2013-04-01

The Artic regions are expected to be very sensitive to the currently observed climate change. When permafrost is thawing, the stored carbon becomes available again for microbial degradation, forming a potential source for the generation of carbon dioxide and methane with their positive feedback effect on the climate warming. For the prediction of future climate evolution it is, therefore, important to improve our knowledge about the microbial-driven greenhouse gas dynamics in the Siberian Arctic and their response to glacial-interglacial changes in the past. Sample material was drilled on Kurungnahk Island (Russian-German LENA expedition) located in the southern part of the Lena delta and in lake El'gygytgyn (ICDP-project) in the eastern part of Siberia. The Kurungnahk samples comprise Late Pleistocene to Holocene deposits, whereas the lake El'gygytgyn samples cover Middle to Late Pleistocene sediments. Samples were investigated applying a combined biogeochemical and microbiological approach. The methane profile of the Kurungnahk core reveals highest methane contents in the warm and wet Holocene and Late Pleistocene (LP) deposits and correlates largly to the organic carbon (TOC) contents. Archaeol concentrations, being a biomarker for past methanogenic archaea, are also high during the warm and wet Holocene and LP intervals and low during the cold and dry LP periods. This indicates that part of the methane might be produced and trapped in the past. However, biomarkers for living microorganisms (bacteria and archaea) and microbial activity measurements of methanogens point, especially, for the Holocene to a viable archaeal community, indicating a possible in-situ methane production. Furthermore, warm/wet-cold/dry climate cycles are recorded in the archaeal diversity as revealed by genetic fingerprint analysis. Although the overlying lake water buffers the temperature effect on the lake sediments, which never became permafrost, the bacterial and archaeal biomarker

Numerical simulation of ground-water flow through glacial deposits and crystalline bedrock in the Mirror Lake area, Grafton County, New Hampshire

Science.gov (United States)

Tiedeman, Claire; Goode, Daniel J.; Hsieh, Paul A.

1997-01-01

This report documents the development of a computer model to simulate steady-state (long-term average) flow of ground water in the vicinity of Mirror Lake, which lies at the eastern end of the Hubbard Brook valley in central New Hampshire. The 10-km2 study area includes Mirror Lake, the three streams that flow into Mirror Lake, Leeman's Brook, Paradise Brook, and parts of Hubbard Brook and the Pemigewasset River. The topography of the area is characterized by steep hillsides and relatively flat valleys. Major hydrogeologic units include glacial deposits, composed of till containing pockets of sand and gravel, and fractured crystalline bedrock, composed of schist intruded by granite, pegmatite, and lamprophyre. Ground water occurs in both the glacial deposits and bedrock. Precipitation and snowmelt infiltrate to the water table on the hillsides, flow downslope through the saturated glacial deposits and fractured bedrock, and discharge to streams and to Mirror Lake. The model domain includes the glacial deposits, the uppermost 150m of bedrock, Mirror Lake, the layer of organic sediments on the lake bottom, and streams and rivers within the study area. A streamflow routing package was included in the model to simulate baseflow in streams and interaction between streams and ground water. Recharge from precipitation is assumed to be areally uniform, and riparian evapotranspiration along stream banks is assumed negligible. The spatial distribution of hydraulic conductivity is represented by dividing the model domain into several zones, each having uniform hydraulic properties. Local variations in recharge and hydraulic conductivities are ignored; therefore, the simulation results characterize the general ground-water system, not local details of ground-water movement. The model was calibrated using a nonlinear regression method to match hydraulic heads measured in piezometers and wells, and baseflow in three inlet streams to Mirror Lake. Model calibration indicates that

Morphogenesis of the Czechowskie Lake as inferred from the sedimentological analysis of limnic, colluvial and glacifluvial deposits (Eastern Pomerania, North Central Poland)

Science.gov (United States)

Kordowski, Jaroslaw; Błaszkiewicz, Mirosław; Kramkowski, Mateusz; Słowiński, Michał; Tyszkowski, Sebastian; Brauer, Achim; Ott, Florian

2014-05-01

Czechowskie Lake is situated in north-central Poland in Tuchola Forest, about 100 kilometers SW away from Gdańsk. In the deepest parts of the lake bottom, there are hidden laminated sediments which hold the Late Glacial and Holcene climatic record. These deposits are subject of detailled work of the joint German-Polish Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association. It has the area of 76,6 ha. Actual water level is at 109,9 m a.s.l. The average depth is 9,59 m, maximal 32 m. The lake occupies a large subglacial channel, reproduced within the glacifluvial sediments of the Pomeranian Phase of the last glaciation. In the widest place it has the width of 1 kilometer. The maximal depth of the channel (counting from the channel edges to the reconstructed deepest lake mineral floor (after removal of the limnic sediments)) may reach 70 meters. Inside of the channel some throughs and small hills do exist which are built of outwash sediments but, considering internal structures, they bear some similarity to the dead ice moraines and kames. The vicinity of the channel consists of two outwash plain levels. The lower one was created on the dead ice blocks. The maximum infilling with the limnic and telmatic sediments reaches over 12 m. In the bottom of the lake there is a marked presence of many overdeepenings with the diameter of dozen or several dozen meters and the depth of up to 10 m with numerous, distinct throughs between them. They favoured the preservation of the lamination in the deepest parts of the lake due to waves hampering and stopping of the density circulation in the lake waterbody. In the colluvial and fluvioglacial deposits there were carried out carefull sedminetological analyses. Limnic sediments were identified by bore holes with preserved undisturbed structure. All done works revealed that some of the glacifluvial deposits were deposited in subglacial conditions in supercritical flow regime. They were

Lores, legends and lodes from lake superior - Mother of copper deposits

Digital Repository Service at National Institute of Oceanography (India)

Iyer, S.D.

.GEOL.SOC.INDIA, VOL.60, NOV. 2002 glaciers during the Pleistocene produced a number of lakes. The Cu deposits are closely related with silver with both having similarities in their occurrence, associated minerals and crystal habits. Native Ag is widespread... but is relatively less and occurs irregularly and unexpectedly. Since mining was confined largely to Cu, Ag was something like a "finders-keepers". Few early mines showed abundant Ag in the upper levels, that for a time Cu was looked upon as a by-product, as more...

Uranium-bearing and associated minerals in their geochemical and sedimentological context, Elliot Lake, Ontario

International Nuclear Information System (INIS)

Theis, N.J.

1979-01-01

The depositional energy environment of the Rio Algom-Denison ore reef was investigated on a regional scale using several parameters including pebble size. Regional trends of decreasing pebble size coincide with the regional direction of sediment transport. Pebble size was also used to characterize the depositional energy environment at the sample level. Quartz-pebble size and pyrite-grain size as determined from the same samples have a correlation coefficient of 0.93 which indicates that the coarse granular pyrite is detrital. Bulk chemical analyses of selected elements (U, Th, Pb, Ti, Ce, La, Y and Zr) which were chosen to reflect specific minerals (uraninite, brannerite, monazite and zircon), showed strong correlation with quartz-pebble size of the respective samples. Electron microprobe analyses of uraninite and brannerite are reported. The uraninites have typical pegmatitic compositions. Several types of brannerite are described; the conclusion reached is that although some brannerite may be detrital, most of it formed by adsorption of uranium onto titania collectors. Redistribution of some of the uranium has not changed the placer nature of the ore reef. Genesis of individual minerals (pyrite, uraninite, brannerite, zircon and monazite) is discussed. It is concluded that the mineralogy and its geochemical expression have been controlled by processes of fluvial deposition. As a result of the regional patterns in depositional environment, the ore reef shows a broad mineralogical zoning. Fluctuations in depositional energy have also produced lithologically related mineral zoning on a smaller scale. (author)

Holocene lake-level fluctuations of Lake Aricota, Southern Peru

Science.gov (United States)

Placzek, C.; Quade, Jay; Betancourt, J.L.

2001-01-01

Lacustrine deposits exposed around Lake Aricota, Peru (17?? 22???S), a 7.5-km2 lake dammed by debris flows, provide a middle to late Holocene record of lake-level fluctuations. Chronological context for shoreline deposits was obtained from radiocarbon dating of vascular plant remains and other datable material with minimal 14C reservoir effects (Titicaca (16?? S), which is only 130 km to the northeast and shares a similar climatology. Comparisons with other marine and terrestrial records highlight emerging contradictions over the nature of mid-Holocene climate in the central Andes. ?? 2001 University of Washington.

Radioactivity assessment of the waste deposited in Candonga's lake after the FundÃO Dam's collapse

Energy Technology Data Exchange (ETDEWEB)

Freire, Carolina Braccini; Cuccia, Valeria; Lameiras, Fernando Soares; Rocha, Zildete, E-mail: cbf@cdtn.br, E-mail: vc@cdtn.br, E-mail: fsl@cdtn.br, E-mail: rochaz@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Santos, Talita Oliveira, E-mail: talitaolsantos@yahoo.com.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem; Sales, Gabriel Lopes, E-mail: gabriellopessales@hotmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Brazil). Dept. de Engenharia Química

2017-07-01

The collapse of the Fundão dam on November 5{sup th} 2015 caused impacts along the hydrographic basin of Rio Doce. Renova Foundation has the mission to repair, restore and reconstruct the regions affected by this disaster. After the collapse, a huge amount of waste was deposited in Risoleta Neves Hydroelectric Power Plant’s lake (Candonga). This waste has been dredged out from the lake and deposited in a nearby pile. The use of the waste from this pile is being considered for civil construction. Samples of this waste pile were collected and they were characterized by X-rays diffraction and EDS analyses, which showed that it consists of 80% quartz, 11% hematite, 8% goethite and 1% clays, mainly kaolinite. There is also organic matter consisting of branches, roots and leaves of trees and plants. Previous radiological analyses made before the collapse showed that the radionuclide content of the waste deposited in Fundão dam was very low. However, the waste deposited in Candonga's lake has a new composition and it is important to evaluate its radioactivity assessment. The analyses results of the Candonda's waste samples will be presented and compared to the results obtained in the Fundão dam samples, before its collapse. (author)

Radioactivity assessment of the waste deposited in Candonga's lake after the FundÃO Dam's collapse

International Nuclear Information System (INIS)

Freire, Carolina Braccini; Cuccia, Valeria; Lameiras, Fernando Soares; Rocha, Zildete; Santos, Talita Oliveira; Sales, Gabriel Lopes

2017-01-01

The collapse of the Fundão dam on November 5 th 2015 caused impacts along the hydrographic basin of Rio Doce. Renova Foundation has the mission to repair, restore and reconstruct the regions affected by this disaster. After the collapse, a huge amount of waste was deposited in Risoleta Neves Hydroelectric Power Plant’s lake (Candonga). This waste has been dredged out from the lake and deposited in a nearby pile. The use of the waste from this pile is being considered for civil construction. Samples of this waste pile were collected and they were characterized by X-rays diffraction and EDS analyses, which showed that it consists of 80% quartz, 11% hematite, 8% goethite and 1% clays, mainly kaolinite. There is also organic matter consisting of branches, roots and leaves of trees and plants. Previous radiological analyses made before the collapse showed that the radionuclide content of the waste deposited in Fundão dam was very low. However, the waste deposited in Candonga's lake has a new composition and it is important to evaluate its radioactivity assessment. The analyses results of the Candonda's waste samples will be presented and compared to the results obtained in the Fundão dam samples, before its collapse. (author)

Deposition of Boron in Possible Evaporite Deposits in Gale Crate

Science.gov (United States)

Gasda, P. J.; Peets, E.; Lamm, S. N.; Rapin, W.; Lanza, N.; Frydenvang, J.; Clark, B. C.; Herkenhoff, K. E.; Bridges, J.; Schwenzer, S. P.; Haldeman, E. B.; Wiens, R. C.; Maurice, S.; Clegg, S. M.; Delapp, D.; Sanford, V.; Bodine, M. R.; McInroy, R.

2017-12-01

Boron has been previously detected in Gale crater using the ChemCam instrument on board the NASA Curiosity rover within calcium sulfate fracture fill hosted by lacustrine mudstone and eolian sandstone units. Recent results show that up to 300 ppm B is present in the upper sections of the lacustrine unit. Boron has been detected in both the groundwater-emplaced calcium sulfate fracture fill materials and bedding-parallel calcium sulfate layers. The widespread bedding-parallel calcium sulfate layers within the upper strata of the lacustrine bedrock that Curiosity has encountered recently could be interpreted as primary evaporite deposits. We have two hypotheses for the history of boron in Gale crater. In both hypotheses, borates were first deposited as lake water evaporated, depositing primary evaporates that were later re-dissolved by groundwater, which redistributed the boron into secondary evaporitic calcium sulfate fracture fill deposits. In the first scenario, Gale crater may have undergone a period of perennial lake formation during a drier period of martian history, depositing layers of evaporitic minerals (including borates) among lacustrine mudstone layers. In the second scenario, lake margins could have become periodically exposed during cyclic drops in lake level and subsequently desiccated. Evaporites were deposited and desiccation features were formed in lowstand deposits. Either hypothetical scenario of evaporite deposition would promote prebiotic chemical reactions via wet-dry cycles. Boron may be an important prebiotic element, and as such, its presence in ancient martian surface and groundwater provides evidence that important prebiotic chemical reactions could occur on Mars if organics were present. The presence of boron in ancient Gale crater groundwater also provides additional evidence that a habitable environment existed in the martian subsurface well after the expected disappearance of liquid water on the surface of Mars. We will report on the

Modelling the role of nitrogen in acidification of Swedish lakes: future scenarios of acid deposition, climate change and forestry practices

Energy Technology Data Exchange (ETDEWEB)

Moldan, Filip (Swedish Environmental Research Institute Ltd., Stockholm (Sweden)); Cosby, B. Jack (Dept. of Env. Sciences, Univ. of Virginia, Charlottesville, VA (United States)); Wright, Richard F. (Norwegian Inst. for Water Research, Kjelsas, Oslo (Norway))

2009-12-15

There are three major drivers that can cause future changes in lake water chemistry: air pollution, land use and climate change. In this report we used an extensive set of Swedish lakes sampled in 1995, 2000 and in 2005 to model future lake water chemistry under 5 different scenarios. The base case scenario represented deposition of air pollutants under current legislation (CLE); that is assuming that emissions of sulphur (S) and nitrogen (N) will be reduced as currently agreed by the Gothenburg protocol, NEC directive and other legislation. After the agreed emission reductions were achieved, no further reduction in deposition was assumed and deposition was maintained constant up to year 2100. The base scenario assumed no change in current forestry practices and no climate change. A second other deposition scenario was based on maximum (technically) feasible emission reduction (MFR). The MFR scenario also did not assume change of either forestry practices or climate. A maximum biomass harvest was modelled (land use, LU, scenario), which entailed harvest of tree stems, slash and stumps. A scenario of climate change (CC) followed the IPCC A2 scenario downscaled to Sweden by SMHI. Finally climate change and land use were combined (CCLU scenario). The CC, LU and CCLU scenarios were driven by the 'current legislation' (CLE) deposition scenario for S and N deposition. The biogeochemical model MAGIC was used in this project, and scenarios were evaluated up to year 2100. Special attention was paid to the impact of the future scenarios on N leaching

Response of lake chemistry to changes in atmospheric deposition and climate in three high-elevation wilderness areas of Colorado

Science.gov (United States)

Mast, M. Alisa; Turk, John T.; Clow, David W.; Campbell, Donald D.

2011-01-01

Trends in precipitation chemistry and hydrologic and climatic data were examined as drivers of long-term changes in the chemical composition of high-elevation lakes in three wilderness areas in Colorado during 1985-2008. Sulfate concentrations in precipitation decreased at a rate of -0.15 to -0.55 μeq/l/year at 10 high-elevation National Atmospheric Deposition Program stations in the state during 1987-2008 reflecting regional reductions in SO2 emissions. In lakes where sulfate is primarily derived from atmospheric inputs, sulfate concentrations also decreased although the rates generally were less, ranging from -0.12 to -0.27 μeq/l/year. The similarity in timing and sulfur isotopic data support the hypothesis that decreases in atmospheric deposition are driving the response of high-elevation lakes in some areas of the state. By contrast, in lakes where sulfate is derived primarily from watershed weathering sources, sulfate concentrations showed sharp increases during 1985-2008. Analysis of long-term climate records indicates that annual air temperatures have increased between 0.45 and 0.93°C per decade throughout most mountainous areas of Colorado, suggesting climate as a factor. Isotopic data reveal that sulfate in these lakes is largely derived from pyrite, which may indicate climate warming is preferentially affecting the rate of pyrite weathering.

Mid Holocene lake level and shoreline behavior during the Nipissing phase of the upper Great Lakes at Alpena, Michigan, USA

Science.gov (United States)

Thompson, T.A.; Lepper, K.; Endres, A.L.; Johnston, J.W.; Baedke, S.J.; Argyilan, E.P.; Booth, R.K.; Wilcox, D.A.

2011-01-01

The Nipissing phase was the last pre-modern high-water stage of the upper Great Lakes. Represented as either a one- or two-peak highstand, the Nipissing occurred following a long-term lake-level rise. This transgression was primarily an erosional event with only the final stage of the transgression preserved as barriers, spits, and strandplains of beach ridges. South of Alpena, Michigan, mid to late Holocene coastal deposits occur as a strandplain between Devils Lake and Lake Huron. The landward part of this strandplain is a higher elevation platform that formed during the final stage of lake-level rise to the Nipissing peak. The pre-Nipissing shoreline transgressed over Devils Lake lagoonal deposits from 6.4 to 6.1. ka. The first beach ridge formed ~ 6. ka, and then the shoreline advanced toward Lake Huron, producing beach ridges about every 70. years. This depositional regression produced a slightly thickening wedge of sediment during a lake-level rise that formed 20 beach ridges. The rise ended at 4.5. ka at the Nipissing peak. This peak was short-lived, as lake level fell > 4. m during the following 500. years. During this lake-level rise and subsequent fall, the shoreline underwent several forms of shoreline behavior, including erosional transgression, aggradation, depositional transgression, depositional regression, and forced regression. Other upper Great Lakes Nipissing platforms indicate that the lake-level change observed at Alpena of a rapid pre-Nipissing lake-level rise followed by a slower rise to the Nipissing peak, and a post-Nipissing rapid lake-level fall is representative of mid Holocene lake level in the upper Great Lakes. ?? 2011 Elsevier B.V.

Monitoring Water Quality at Lake Merritt, Oakland, CA Following Improvements to the Tidal Channel to the San Francisco Bay

Science.gov (United States)

Bracho, H.; Martinez, J.; Johnson, M.; Turrey, A.; Avila, M.; Medina, S.; Rubio, E.; Ahumada, E.; Nguyen, S.; Guzman, Y.

2014-12-01

Elliot Ahumada, Esosa Oghogho, Samantha Nguyen, Humberto Bracho, Diego Quintero, Ashanti Johnson and Kevin Cuff Lake Merritt is a tidal lagoon in the center of Oakland, California, just east of Downtown. Water quality at Lake Merritt has been a major concern for community members and researchers for many years (Pham 200X). Results of past research lead to recommendations to lengthen a channel that connects Lake Merritt with the San Francisco Bay to improve water flow and quality. In 2012 the City of Oakland responded to these recommendations by initiating the creation of a 230-meter long channel. In conducting our research we use a water quality index that takes into account measurements of pH, temperature, water hardness (dissolved solids), ammonia, salinity, dissolved oxygen, and nitrate. Newly collected data is then compared with that collected by Pham using comparable parameters to assess the impact of recent changes at the Lake on its overall water quality. In addition, we measured the abundance of aquatic species at four different sites within the Lake. Preliminary results suggest that an increase in the abundance of fish and improved overall water quality have resulted from channel extension at Lake Merritt.

Late Quaternary sedimentary features of Bear Lake, Utah and Idaho

Science.gov (United States)

Smoot, J.P.

2009-01-01

Bear Lake sediments were predominantly aragonite for most of the Holocene, reflecting a hydrologically closed lake fed by groundwater and small streams. During the late Pleistocene, the Bear River flowed into Bear Lake and the lake waters spilled back into the Bear River drainage. At that time, sediment deposition was dominated by siliciclastic sediment and calcite. Lake-level fluctuation during the Holocene and late Pleistocene produced three types of aragonite deposits in the central lake area that are differentiated primarily by grain size, sorting, and diatom assemblage. Lake-margin deposits during this period consisted of sandy deposits including well-developed shoreface deposits on margins adjacent to relatively steep gradient lake floors and thin, graded shell gravel on margins adjacent to very low gradient lake-floor areas. Throughout the period of aragonite deposition, episodic drops in lake level resulted in erosion of shallow-water deposits, which were redeposited into the deeper lake. These sediment-focusing episodes are recognized by mixing of different mineralogies and crystal habits and mixing of a range of diatom fauna into poorly sorted mud layers. Lake-level drops are also indicated by erosional gaps in the shallow-water records and the occurrence of shoreline deposits in areas now covered by as much as 30 m of water. Calcite precipitation occurred for a short interval of time during the Holocene in response to an influx of Bear River water ca. 8 ka. The Pleistocene sedimentary record of Bear Lake until ca. 18 ka is dominated by siliciclastic glacial fl our derived from glaciers in the Uinta Mountains. The Bear Lake deep-water siliciclastic deposits are thoroughly bioturbated, whereas shallow-water deposits transitional to deltas in the northern part of the basin are upward-coarsening sequences of laminated mud, silt, and sand. A major drop in lake level occurred ca. 18 ka, resulting in subaerial exposure of the lake floor in areas now covered by

Canadian experience with uranium tailings disposal

International Nuclear Information System (INIS)

Culver, K.B.

1982-06-01

During the first years of uranium production in Canada uranium tailings were discharged directly into valleys or lakes near the mill. Treatment with barium chloride to precipitate radium began in 1965 at the Nordic Mine at Elliot Lake, Ontario. In the mid-60s and early 70s water quality studies indicated that discharges from uranium tailings areas were causing degradation to the upper part of the Serpent River water system. Studies into acid generation, revegetation, and leaching of radium were initiated by the mining companies and resulted in the construction of treatment plants at a number of sites. Abandoned tailings sites were revegetated. At hearings into the expansion of the Elliot Lake operations the issue of tailings management was a major item for discussion. As a result federal and provincial agencies developed guidelines for the siting and development of urnaium tailings areas prior to issuing operating licences. Western Canadian uranium producers do not have the acid generation problem of the Elliot Lake operations. The Rabbit Lake mill uses settling ponds followed by filtration. High-grade tailings from Cluff Lake are sealed in concrete and buried. Uranium producers feel that the interim criteria developed by the Atomic Energy Control Board, if adopted, would have a harmful effect on the viability of the Canadian uranium industry

A post-Calumet shoreline along southern Lake Michigan

Science.gov (United States)

Capps, D.K.; Thompson, T.A.; Booth, R.K.

2007-01-01

The southern shore of Lake Michigan is the type area for many of ancestral Lake Michigan's late Pleistocene lake phases, but coastal deposits and features of the Algonquin phase of northern Lake Michigan, Lake Huron, and Lake Superior are not recognized in the area. Isostatic rebound models suggest that Algonquin phase deposits should be 100 m or more below modern lake level. A relict shoreline, however, exists along the lakeward margin of the Calumet Beach that was erosional west of Deep River and depositional east of the river. For this post-Calumet shoreline, the elevation of basal foreshore deposits east of Deep River and the base of the scarp west of Deep River indicate a slightly westward dipping water plane that is centered at ???184 m above mean sea level. Basal foreshore elevations also indicate that lake level fell ???2 m during the development of the shoreline. The pooled mean of radiocarbon dates from the surface of the peat below post-Calumet shoreline foreshore deposits indicate that the lake transgressed over the peat at 10,560 ?? 70 years B.P. Pollen assemblages from the peat are consistent with this age. The elevation and age of the post-Calumet shoreline are similar to the Main Algonquin phase of Lake Huron. Recent isostatic rebound models do not adequately address a high-elevation Algonquin-age shoreline along the southern shore of Lake Michigan, but the Goldthwait (1908) hinge-line model does. ?? 2006 Springer Science+Business Media B.V.

226Ra concentrations in crayfish tissues, water, and sediments from the Serpent River Basin in Northeastern Ontario, Canada

International Nuclear Information System (INIS)

Alikhan, M.A.

1996-01-01

Lower Serpent River, as well as Elliot, McCarthy and McCabe lakes had highest 226 Ra contamination, Chrisman, Quirke and Whiskey lakes a moderate one, Flack and Semiwhite lakes and the 'distant' control, Lake Wanapitei, the lowest. 226 Ra activity in Cambarus robustus tissues was directly related to their background levels. Thus, concentration coefficient (tissue/sediment concentrations) for 226 Ra ranged from 0.53 to 0.74 in highly contaminated Elliot and McCarthy lakes, 0.28 to 0.59 in moderately contaminated Quirke and Whiskey lakes, and from 0.27 to 3.44 in least contaminated Semiwhite and Flack lakes. Among various organs analysed, exoskeleton showed the highest (43.04 - 90.69%) and the tail muscles the lowest (2.95 -17.14%) 226 Ra activity. 226 Ra concentrations in the alimentary canal were considered a part of the ambient environment as they had not been absorbed

The uranium mine Key Lake, Canada, as an example of final deposition of radioactive tailings

International Nuclear Information System (INIS)

Schmitz, T.

1984-01-01

The main part of that waste handling system is tailing storage. The other parts include the water storage reservoirs and monitoring ponds. Soil conditions and design features of the tailings pond are described in detail as well as the method of tailings disposal. Finally the method of deposition results in a laminated radioactive tailings deposit and the tailings reach a degree of compactness comparable to concrete. The Key Lake Mining Corporation and its consultants have developed a tailings handling program in order to minimize environmental impact and to take advantage of the natural topography and soil materials in the project area. (orig./HP) [de

Men of Good Will: The Religious Education Association, J. Elliot Ross, and the National Conference of Jews and Christians

Science.gov (United States)

Nolan, Lucinda A.

2009-01-01

An impetus of the Religious Education Association (REA) toward becoming an actively intercultural and interreligious agency emerged in the third decade of its existence. This article explores this period through an examination of the involvement of the REA members, Father John Elliot Ross and others (1884-1946) in a series of seminars conducted by…

Evaporite deposition in a shallow perennial lake, Qaidam basin, western China

Energy Technology Data Exchange (ETDEWEB)

Schubel, K.A.; Lowenstein, T.K. (SUNY, Binghampton, NY (United States)); Spencer, R.J. (Univ. of Calgary, Alberta (Canada)); Pengxi, Z. (Institute of Salt Lakes, Xining (China))

1991-03-01

Evaporites accumulate in ephemeral saline-pans, shallow perennial lakes or lagoons, and deep perennial systems. Continuous brine trench exposures of Holocene evaporites from the Qaidam basin provide criteria for the recognition of shallow perennial lake sediments. Based on Landsat photographs, lateral extent of beds (at least 7 km), and sequence thicknesses (maximum 2.5 m), the paleolake is interpreted to have been less than 2.5 m deep and at least 120 km{sup 2} in area. Sediments consist of laminated siliciclastic mud overlain by mud-halite couplets (mm- to cm-scale layers), which represent one vertical shallowing- and concentrating-upwards sequence. The basal laminite marks the onset of deposition in this shallow perennial paleolake. Syndepositional halite textures and fabrics in the overlying mud-halite couplets include cumulates, rafts, and chevrons, draped by mud laminae, and halite layers truncated by horizontal dissolution surfaces (increasing in frequency upwards). Paleolake brines, determined from fluid inclusion melting temperatures, are Na-Mg-Cl-rich and evolve from 0.84 m Mg{sup 2} to 1.52 m Mg{sup 2+} (near the surface). Combinations of the following criteria may be used for the recognition of shallow, nonstratified, perennial lake sediments: lateral continuity of layers; muds undisrupted by subaerial exposure; vertical bottom-growth of halite; halite layers conformably overlain by mud; halite layers truncated by nonuniformly spaced horizontal dissolution surfaces; erosional scours and channels filled with cross-laminated gypsum, halite, and siliciclastic sand and mud; and salinity fluctuations over small stratigraphic intervals within an overall concentrating-upwards sequence.

Quantifying nutrient export and deposition with a dynamic landscape evolution model for the lake Bolsena watershed, Italy

Science.gov (United States)

Pelorosso, Raffaele; Temme, Arnoud; Gobattoni, Federica; Leone, Antonio

2010-05-01

Excessive nutrient loads from upstream watershed activities such as agriculture, hydrological modifications, and urban runoff, have been identified as the leading cause of deterioration in assessed lakes and reservoirs (USEPA, 2000; Leone et al., 2001; Leone et al., 2003). Excessive nutrient transport into lakes and reservoirs may accelerate eutrophication rates, causing negative impacts on aesthetic and water quality. As reservoirs become eutrophic, they are depleted in oxygen and enriched in suspended solids, with heavy consequences for ecosystems and natural habitats. Management of nutrient loads into reservoirs requires knowledge of nutrient transport and delivery from the watershed-stream system (Ripa, 2003). Managing uncultivated lands in watersheds may be a cost effective way to improve water quality in agricultural landscapes, and recent advances in landscape ecology highlight important relationships between the structural configuration of these lands and nutrient redistribution (e.g., Forman 1987; Barrett and others 1990). Many studies have been carried out to underline and explain how landscape characteristics and structure may affect these processes. In these studies, relations between land cover and nutrient storage were analyzed using geographic information systems (GIS) (e.g. Lucas, 2002). Nutrients are generally transported from the landscape into streams during runoff events; however, they may also enter stream flow from other sources such as groundwater recharge and point source effluent discharges (Lucas, 2002; Nielsen, 2007; Waldron, 2008; Castillo, 2009). Water moves nutrients and delivers them to downstream water bodies such as lakes and reservoirs so that erosion phenomena play an essential role in determining nutrients fluxes and deposition. On the one hand, several hydrological models take into account nutrients reactions, movements and deposition - coupling soil erosion processes with transport equations (Bartley, 2004; Lű, 2010). On the

Spatial patterns and temporal trends in mercury concentrations, precipitation depths, and mercury wet deposition in the North American Great Lakes region, 2002–2008

International Nuclear Information System (INIS)

Risch, Martin R.; Gay, David A.; Fowler, Kathleen K.; Keeler, Gerard J.; Backus, Sean M.; Blanchard, Pierrette; Barres, James A.; Dvonch, J. Timothy

2012-01-01

Annual and weekly mercury (Hg) concentrations, precipitation depths, and Hg wet deposition in the Great Lakes region were analyzed by using data from 5 monitoring networks in the USA and Canada for a 2002–2008 study period. High-resolution maps of calculated annual data, 7-year mean data, and net interannual change for the study period were prepared to assess spatial patterns. Areas with 7-year mean annual Hg concentrations higher than the 12 ng per liter water-quality criterion were mapped in 4 states. Temporal trends in measured weekly data were determined statistically. Monitoring sites with significant 7-year trends in weekly Hg wet deposition were spatially separated and were not sites with trends in weekly Hg concentration. During 2002–2008, Hg wet deposition was found to be unchanged in the Great Lakes region and its subregions. Any small decreases in Hg concentration apparently were offset by increases in precipitation. - Highlights: ► Data from 5 Hg and precipitation networks in the USA and Canada were combined for the first time. ► High-resolution maps and statistical trends tests were used for spatial and temporal data analysis. ► Some 7-year mean annual Hg concentrations exceeded a 12 ng per liter water-quality criterion. ► Small, localized decreases in Hg concentration were offset by increases in precipitation. ► Hg wet deposition was unchanged in the Great Lakes region and its subregions during 2002–2008. - Analysis of monitoring data from 5 networks in the USA and Canada determined that mercury wet deposition was unchanged in the North American Great Lakes region during 2002–2008.

{sup 226}Ra concentrations in crayfish tissues, water, and sediments from the Serpent River Basin in Northeastern Ontario, Canada

Energy Technology Data Exchange (ETDEWEB)

Alikhan, M.A. [Laurentian Univ., Sudbury, ON (Canada). Dept of Biology

1996-12-31

Lower Serpent River, as well as Elliot, McCarthy and McCabe lakes had highest {sup 226}Ra contamination, Chrisman, Quirke and Whiskey lakes a moderate one, Flack and Semiwhite lakes and the `distant` control, Lake Wanapitei, the lowest. {sup 226}Ra activity in Cambarus robustus tissues was directly related to their background levels. Thus, concentration coefficient (tissue/sediment concentrations) for {sup 226}Ra ranged from 0.53 to 0.74 in highly contaminated Elliot and McCarthy lakes, 0.28 to 0.59 in moderately contaminated Quirke and Whiskey lakes, and from 0.27 to 3.44 in least contaminated Semiwhite and Flack lakes. Among various organs analysed, exoskeleton showed the highest (43.04 - 90.69%) and the tail muscles the lowest (2.95 -17.14%) {sup 226}Ra activity. {sup 226}Ra concentrations in the alimentary canal were considered a part of the ambient environment as they had not been absorbed. 12 refs, 1 fig, 1 tab.

Effects of Simulated Nitrogen Deposition on Soil Respiration in a Populus euphratica Community in the Ebinur Lake Area, a Desert Ecosystem of Northwestern China.

Science.gov (United States)

He, Xuemin; Lv, Guanghui; Qin, Lu; Chang, Shunli; Yang, Min; Yang, Jianjun; Yang, Xiaodong

2015-01-01

One of the primary limiting factors for biological activities in desert ecosystems is nitrogen (N). This study therefore examined the effects of N and investigated the responses of an arid ecosystem to global change. We selected the typical desert plant Populus euphratica in a desert ecosystem in the Ebinur Lake area to evaluate the effects of N deposition on desert soil respiration. Three levels of N deposition (0, 37.5 and 112.5 kg·N·ha-1·yr-1) were randomly artificially provided to simulate natural N deposition. Changes in the soil respiration rates were measured from July to September in both 2010 and 2013, after N deposition in April 2010. The different levels of N deposition affected the total soil N, soil organic matter, soil C/N ratio, microorganism number, and microbial community structure and function. However, variable effects were observed over time in relation to changes in the magnitude of N deposition. Simulated high N deposition significantly reduced the soil respiration rate by approximately 23.6±2.5% (Pdesert ecosystem of the Ebinur Lake area, N deposition indirectly changes the soil respiration rate by altering soil properties.

Acidification in Three Lake District Tarns: Historical Iong term trends and modelled future behaviour under changing sulphate and nitrate deposition

Directory of Open Access Journals (Sweden)

P. G. Whitchead

1997-01-01

Full Text Available Three upland Lake District Tarns, Scoat, Greendale and Burnmoor, have been evaluated using MAGIC (Model of Acidification of Groundwater In Catchments to reconstruct past, present and future chemical behaviour. The modelled historical changes in acidity are compared with palaeoecological estimation of pH to demonstrate model validity. Chemistry as simulated for all anions and cations and two of the three lakes are shown to have undergone significant acidification. The effects of changing atmospheric pollution levels on lake chemistry is evaluated and 80-90% sulphur reduction levels are required to achieve zero alkalinity. The impacts of increased nitrogen deposition are assessed and are shown to further delay reversibility.

Modelling regional response of lakewater chemistry to changes in acidic deposition: the MAGIC model applied to lake surveys in southernmost Norway 1974-1986-1995

Directory of Open Access Journals (Sweden)

B. J. Cosby

1998-01-01

Full Text Available Two methods for modelling regional responses of lake water quality to changes in acidic deposition in southernmost Norway were examined. Both methods are based upon the MAGIC model but differ in mode of regional application; one uses site-specific while the other uses Monte-Carlo methods for model calibration. The simulations of regional responses from both methods were compared with observed responses based on data from three lake surveys in southernmost Norway conducted in 1974, 1986 and 1995. The regional responses of the two modelling approaches were quite similar and agreed well with the observed regional distributions of lakewater chemistry variables. From 1974 to 1986 the observed data indicated that despite a decline of approximately 10% in sulphate (SO4 deposition, the mean acid neutralizing capacity (ANC of lakes in southernmost Norway declined by approximately 6 μeq l-1. Both modelling approaches simulated no change or a very small decline in mean ANC for that period. From 1986 to 1995 the observed data indicated that, in response to an approximate 40% decline in SO4 deposition, the mean ANC of lakes in southernmost Norway increased by 11-16 μeq l-1. The modelling approaches simulated increases of 9-10 μeq l-1 in mean ANC for the same period. Both simulations and observations indicate that > 65% of lakes in southernmost Norway were acidic in 1974 and 1995. Both simulation methods predict that >65% of the lakes in southernmost Norway will have positive ANC values within 10 years of reductions of SO4 deposition to 20% of 1974 levels. Of the two regionalization methods the site-specific method appears preferable, because whereas the Monte-Carlo method gives results for a region as a whole, the site-specific method also reveals patterns within the region. The maintenance of a one-to-one correspondence between simulated and observed systems means that simulation results can be mapped for a geographically explicit presentation of model

International Uranium Resources Evaluation Project (IUREP) national favourability studies: Canada

International Nuclear Information System (INIS)

1977-08-01

Exploration for mineral deposits in Canada resulted in the discovery of large uranium deposits, such as at Great. Bear Lake, Northwest Territories (1930), in the Elliot Lake area, Ontario (1949); Beaverlodge, Wollaston Lake Fold Belt and Carswell Structure in Saskatchewan (1946-1975) and many uranium occurrences in the Canadian Shield, in the Orogenic Belts and in the Platforms. Uranium output in Canada since 1942 until and including 1976 amounted to 112,000 tonnes U. Reasonably Assured uranium resources as of 1976 amounted to 167,000 tonnes U (at a price up to $40/lb. U 3 0 8 ) and 15,000 tonnes U (at a price more than $40 up to $60/lb. U 3 O 8 ). Estimated Additional uranium resources as of 1976 amounted to 392,000 tonnes U (at a price up to $40/lb. U-Og) and 264,000 tonnes U (at a price more than $40 up to $60/lb. U 3 0 8 ). Possible further potential beyond the above mentioned classes is tentatively estimated to be in the 6th category according to NEA/IAEA favourability classification. (author)

Historical records of polycyclic aromatic hydrocarbon deposition in a shallow eutrophic lake: Impacts of sources and sedimentological conditions.

Science.gov (United States)

Li, Chaocan; Huo, Shouliang; Yu, Zhiqiang; Guo, Wei; Xi, Beidou; He, Zhuoshi; Zeng, Xiangying; Wu, Fengchang

2016-03-01

Sediment core samples collected from Lake Chaohu were analyzed for 15 priority polycyclic aromatic hydrocarbons (PAHs) to assess the spatial and temporal distributions of the PAHs during lacustrine sedimentary processes and regional economic development. Assessing the PAH sedimentary records over an approximately 100-year time span, we identified two stages in the PAH inputs and sources (before the 1970s and after the 1970s) in the eastern lake region near a village, whereas three stages (before the 1950s, 1950s-1990s and after the 1990s) were identified in the western lake region near urban and industrial areas. Rapid increases in the PAH depositional fluxes occurred during the second stage due to increased human activities in the Lake Chaohu basin. The composition and isomeric ratios of the PAHs revealed that pyrolysis is the main source of PAHs in this lake. Strong positive relationships between PAH concentration and the total organic carbon concentration, sediment grain size (energy consumption and the levels of urban industrialization and civilization, affect both the composition and abundance of the PAHs. Copyright © 2015. Published by Elsevier B.V.

Earthquake-induced soft-sediment deformation structures in Late Pleistocene lacustrine deposits of Issyk-Kul lake (Kyrgyzstan)

Science.gov (United States)

Gladkov, A. S.; Lobova, E. U.; Deev, E. V.; Korzhenkov, A. M.; Mazeika, J. V.; Abdieva, S. V.; Rogozhin, E. A.; Rodkin, M. V.; Fortuna, A. B.; Charimov, T. A.; Yudakhin, A. S.

2016-10-01

This paper discusses the composition and distribution of soft-sediment deformation structures induced by liquefaction in Late Pleistocene lacustrine terrace deposits on the southern shore of Issyk-Kul Lake in the northern Tien Shan mountains of Kyrgyzstan. The section contains seven deformed beds grouped in two intervals. Five deformed beds in the upper interval contain load structures (load casts and flame structures), convolute lamination, ball-and-pillow structures, folds and slumps. Deformation patterns indicate that a seismic trigger generated a multiple slump on a gentle slope. The dating of overlying subaerial deposits suggests correlation between the deformation features and strong earthquakes in the Late Pleistocene.

Submission to the Royal Commission on Health and Environmental Protection - Uranium Mining. Phase VII: public and worker health

International Nuclear Information System (INIS)

Seguin, H.

1980-01-01

This submission is intended to provide a brief resume of Elliot Lake's uranium mining/milling history, particularly with respect to the adverse effects on workers' health and the environment in general. Elliot Lake has pioneered various uranium mining and processing techniques. Its operations have also been directly linked with death and incapacities of workers and considerable destruction of the surrounding environment. The union believes that many unknowns continue to exist and that considerable research is required before various answers are available. It is for for these reasons that the union approaches uranium mining expansion and new developments with extreme caution

Trends in lake chemistry in response to atmospheric deposition and climate in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming, 1993-2009

Science.gov (United States)

Mast, M. Alisa; Ingersoll, George P.

2011-01-01

In 2010, the U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Forest Service, Air Resource Management, began a study to evaluate long-term trends in lake-water chemistry for 64 high-elevation lakes in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming during 1993 to 2009. The purpose of this report is to describe trends in the chemical composition of these high-elevation lakes. Trends in emissions, atmospheric deposition, and climate variables (air temperature and precipitation amount) are evaluated over a similar period of record to determine likely drivers of changing lake chemistry. Sulfate concentrations in precipitation decreased over the past two decades at high-elevation monitoring stations in the Rocky Mountain region. The trend in deposition chemistry is consistent with regional declines in sulfur dioxide emissions resulting from installation of emission controls at large stationary sources. Trends in nitrogen deposition were not as widespread as those for sulfate. About one-half of monitoring stations showed increases in ammonium concentrations, but few showed significant changes in nitrate concentrations. Trends in nitrogen deposition appear to be inconsistent with available emission inventories, which indicate modest declines in nitrogen emissions in the Rocky Mountain region since the mid-1990s. This discrepancy may reflect uncertainties in emission inventories or changes in atmospheric transformations of nitrogen species that may be affecting deposition processes. Analysis of long-term climate records indicates that average annual mean air temperature minimums have increased from 0.57 to 0.75 °C per decade in mountain areas of the region with warming trends being more pronounced in Colorado. Trends in annual precipitation were not evident over the period 1990 to 2006, although wetter than average years during 1995 to 1997 and drier years during 2001 to 2004 caused a notable decline in precipitation

Geology and ore deposits of the Section 23 Mine, Ambrosia Lake District, New Mexico

Science.gov (United States)

Granger, H.C.; Santos, E.S.

1982-01-01

The section 23 mine is one of about 18 large uranium mines opened in sandstones of the fluvial Westwater Canyon Member of the Jurassic Morrison Formation in the Ambrosia Lake mining district during the early 1960s. The Ambrosia Lake district is one of several mining districts within the Grants mineral belt, an elongate zone containing many uranium deposits along the southern flank of the San Juan basin. Two distinct types of ore occur in the mine. Primary ore occurs as peneconcordant layers of uranium-rich authigenic organic matter that impregnates parts of the reduced sandstone host rocks and which are typically elongate in an east-southeast direction subparallel both to the sedimentary trends and to the present-day regional strike of the strata. These are called prefault or trend ores because of their early genesis and their elongation and alinement. A second type of ore in the mine is referred to as postfault, stacked, or redistributed ore. Its genesis was similar to that of the roll-type deposits in Tertiary rocks of Wyoming and Texas. Oxidation, related to the development of a large tongue of oxidized rock extending from Gallup to Ambrosia Lake, destroyed much of the primary ore and redistributed it as massive accumulations of lower grade ores bordering the redox interface at the edge of the tongue. Host rocks in the southern half of sec. 23 (T. 14 N., R. 10 W.) are oxidized and contain only remnants of the original, tabular, organic-rich ore. Thick bodies of roll-type ore are distributed along the leading edge of the oxidized zone, and pristine primary ore is found only near the north edge of the section. Organic matter in the primary ore was derived from humic acids that precipitated in the pores of the sandstones and fixed uranium as both coffinite and urano-organic compounds. Vanadium, molybdenum, and selenium are also associated with the ore. The secondary or roll-type ores are essentially free of organic carbon and contain uranium both as coffinite and

Acidic deposition: State of science and technology. Report 10. Watershed and lake processes affecting surface-water acid-base chemistry. Final report

International Nuclear Information System (INIS)

Turner, R.S.; Cook, R.B.; Miegroet, H.V.; Johnson, D.W.; Elwood, J.W.

1990-09-01

The acid-base chemistry of surface waters is governed by the amount and chemistry of deposition and by the biogeochemical reactions that generate acidity or acid neutralizing capacity (ANC) along the hydrologic pathways that water follows through watersheds to streams and lakes. The amount of precipitation and it chemical loading depend on the area's climate and physiography, on it proximity to natural or industrial gaseous or particulate sources, and on local or regional air movements. Vegetation interacts with the atmosphere to enhance both wet and dry deposition of chemicals to a greater or lesser extent, depending on vegetation type. Vegetation naturally acidifies the environment in humid regions through processes of excess base cation uptake and generation of organic acids associated with many biological processes. Natural acid production and atmospheric deposition of acidic materials drive the acidification process. The lake or stream NAC represents a balance between the acidity-and ANC-generating processes that occur along different flow paths in the watershed and the relative importance of each flow path

A meta-analytic review of Elliot's (1999 Hierarchical Model of Approach and Avoidance Motivation in the sport, physical activity, and physical education literature

Directory of Open Access Journals (Sweden)

Marc Lochbaum

2017-03-01

Conclusion: Future research is encouraged to grow and enrich the understanding of achievement goals within Elliot's complete Hierarchical Model of Approach and Avoidance Motivation to include both antecedents and outcomes simultaneously to improve upon the understanding of achievement motivation in sport, exercise, and physical activity settings.

Effects of Simulated Nitrogen Deposition on Soil Respiration in a Populus euphratica Community in the Ebinur Lake Area, a Desert Ecosystem of Northwestern China.

Directory of Open Access Journals (Sweden)

Xuemin He

Full Text Available One of the primary limiting factors for biological activities in desert ecosystems is nitrogen (N. This study therefore examined the effects of N and investigated the responses of an arid ecosystem to global change. We selected the typical desert plant Populus euphratica in a desert ecosystem in the Ebinur Lake area to evaluate the effects of N deposition on desert soil respiration. Three levels of N deposition (0, 37.5 and 112.5 kg·N·ha-1·yr-1 were randomly artificially provided to simulate natural N deposition. Changes in the soil respiration rates were measured from July to September in both 2010 and 2013, after N deposition in April 2010. The different levels of N deposition affected the total soil N, soil organic matter, soil C/N ratio, microorganism number, and microbial community structure and function. However, variable effects were observed over time in relation to changes in the magnitude of N deposition. Simulated high N deposition significantly reduced the soil respiration rate by approximately 23.6±2.5% (P<0.05, whereas low N deposition significantly increased the soil respiration rate by approximately 66.7±2.7% (P<0.05. These differences were clearer in the final growth stage (September. The different levels of N deposition had little effect on soil moisture, whereas N deposition significantly increased the soil temperature in the 0-5 cm layer (P<0.05. These results suggest that in the desert ecosystem of the Ebinur Lake area, N deposition indirectly changes the soil respiration rate by altering soil properties.

Post-Depositional Behavior of Cu in a Metal-Mining Polishing Pond (East Lake, Canada)

Science.gov (United States)

Martin, A.J.; Jambor, J.L.; Pedersen, Thomas F.; Crusius, J.

2003-01-01

The post-depositional behavior of Cu in a gold-mining polishing pond (East Lake, Canada) was assessed after mine closure by examination of porewater chemistry and mineralogy. The near-surface (upper 1.5 cm) sediments are enriched in Cu, with values ranging from 0.4 to 2 wt %. Mineralogical examination revealed that the bulk of the Cu inventory is present as authigenic copper sulfides. Optical microscopy, energy-dispersion spectra, and X-ray data indicate that the main Cu sulfide is covellite (CuS). The formation of authigenic Cu-S phases is supported by the porewater data, which demonstrate that the sediments are serving as a sink for dissolved Cu below sub-bottom depths of 1-2 cm. The zone of Cu removal is consistent with the occurrence of detectable sulfide and the consumption of sulfate. The sediments can be viewed as a passive bioreactor that permanently removes Cu as insoluble copper sulfides. This process is not unlike that which occurs in other forms of bioremediation, such as wetlands and permeable reactive barriers. Above the zone of Cu removal, dissolved Cu maxima in the interfacial porewaters range from 150 to 450 ??g L-1 and reflect the dissolution of a Cu-bearing phase in the surface sediments. The reactive phase is thought to be a component of treatment sludges delivered to the lake as part of cyanide treatment. Flux calculations indicate that the efflux of dissolved Cu from the sediments to the water column (14-51 ??g cm-2 yr-1) can account for the elevated levels of dissolved Cu in lake waters (???50 ??g L-1). Implications for lake recovery are discussed.

Cosmogenic 10Be Dating of Northern Quebec-Labrador Glacial Lake Shorelines and Drainage Deposits: Implications for the Final Meltwater Discharges of the Last Deglaciation

Science.gov (United States)

Roy, M.; Dube-Loubert, H.; Schaefer, J. M.; Hébert, S.

2017-12-01

The decay of the Laurentide ice sheet played an important role in the climate variability of the last deglaciation, notably through large discharges of meltwater from glacial lakes that disturbed the Atlantic meridional overturning oceanic circulation (AMOC). These former climate-forcing events are now under focus due to growing evidence showing that the present-day increase in freshwater releases from Greenland and other Arctic glaciers may potentially lead to a slowdown of the AMOC and cause important climate feedbacks. In northern Quebec and Labrador, the end of the deglaciation led to the formation of at least 10 important glacial lakes that drained into the nearby Labrador Sea where repeated meltwater discharges could have destabilized the ocean surface conditions in this key sector of the North Atlantic Ocean. Although the drainage of these ice-dammed lakes may form a good analogue for modern processes, the lack of direct constraints on the physiographic configuration and temporal evolution of these lakes limits our understanding of the timing and climate impact of these final meltwater pulses. Here we applied cosmogenic 10Be dating to raised boulder shorelines belonging to Lake Naskaupi, one of the largest glacial lakes in northern Quebec and Labrador. We reconstructed the lake extent and meltwater volume, as well as its lake-level history by systematic mapping of geomorphic features. We sampled a total of 16 boulders at 4 sites along the valley. In addition, we dated five boulders belonging to a large-scale outburst flood deposit recording the abrupt drainage of the lake. The distribution of the 21 ages shows a remarkable consistency, yielding a mean age of 7.8 ± 0.4 ka (1 outlier excluded). The ages from the shorelines are indistinguishable from those of the outburst flood deposit, suggesting that Lake Naskaupi existed for a relatively short time span. These new chronological data constrain the timing of the lake development and attendant drainage

Trends in summer chemistry linked to productivity in lakes recovering from acid deposition in the Adirondack region of New York

Science.gov (United States)

Momen, B.; Lawrence, G.B.; Nierzwicki-Bauer, S. A.; Sutherland, J.W.; Eichler, L.W.; Harrison, J.P.; Boylen, C.W.

2006-01-01

The US Environmental Protection Agency established the Adirondack Effects Assessment Program (AEAP) to evaluate and monitor the status of biological communities in lakes in the Adirondack region of New York that have been adversely affected by acid deposition. This program includes chemical analysis of 30 lakes, sampled two to three times each summer. Results of trends analysis for lake chemistry and chlorophyll a (chlor a) are presented for 1994 to 2003, and a general comparison is made with recent results of the Adirondack Long-Term Monitoring (ALTM) Program, which included chemical analysis of all but two of these lakes (plus an additional 24 lakes) monthly, year-round for 1992-2004. Increases in pH were found in 25 of the 30 AEAP lakes (P level of P level of P level of P level of P level of P chemistry were similar to those of the ALTM Program, although decreases in SO 42- concentrations were more evident in the year-round ALTM record. Overall, the results suggest (a) a degree of chemical recovery from acidification during the summer, (b) an increase in phytoplankton productivity, and (c) a decreasing trend in NO 3- concentrations resulting from the increased productivity. ?? 2007 Springer Science+Business Media, Inc.

Geology and ore deposits of Johnny M mine, Ambrosia Lake District

International Nuclear Information System (INIS)

Falkowski, S.K.

1980-01-01

The Johnny M mine is one of very few mines in the Ambrosia Lake district with uranium ore in two members of the Morrison Formation (Jurassic); these members are the Westwater Canyon Sandstone and the Brushy Basin Shale. The Westwater Canyon ore is contained in the two upper sandstone units of the member, and the Brushy Basin ore is contained in the Poison Canyon sandstone (informal usage). The sedimentary features and structures in the Westwater Canyon sandstones indicate that the sediments were deposited by a system of aggrading braided streams, possibly at the distal end of coalescing alluvial fans. The Poison Canyon sandstone was probably the result of deposition in a complex environment of meandering and braided streams. Paleocurrent-direction indicators, such as fossilized-log orientation, foreset azimuths, and the axes of crossbeds and channel scours, suggest that the local palostream flow was to the east and southeast. The uranium mineralization is closely associated with 1) local accumulations of carbonaceous (humate) matter derived from the decay of organic material and 2) paleostream channels preserved in the rocks. The ore elements were derived from the leaching of volcanic air-fall tuffs and ash, which were introduced into the fluvial system during volcanic activity in the western United States. The mobile ore-element ions were reduce and concentrated by humic acids and bacteria present in the fluvial system and ultimately remobilized into the forms present today. The uranium is thus envisioned as forming either essentially on the surface as the sediments were being deposited or at very shallow depth

Factors controlling localization of uranium deposits in the Dakota Sandstone, Gallup and Ambrosia Lake mining districts, McKinley County, New Mexico

Science.gov (United States)

Pierson, Charles Thomas; Green, Morris W.

1977-01-01

Geologic studies were made at all of the uranium mines and prospects in the Dakota Sandstone of Early(?) and Late Cretaceous age in the Gallup mining district, McKinley County, New Mexico. Dakota mines in the adjacent Ambrosia Lake mining district were visited briefly for comparative purposes. Mines in the eastern part of the Gallup district, and in the Ambrosia Lake district, are on the Chaco slope of the southern San Juan Basin in strata which dip gently northward toward the central part of the basin. Mines in the western part of the Gallup district are along the Gallup hogback (Nutria monocline) in strata which dip steeply westward into the Gallup sag. Geologic factors which controlled formation of the uranium deposits in the Dakota Sandstone are: (1) a source of uranium, believed to be uranium deposits of the underlying Morrison Formation of Late Jurassic age; (2) the accessibility to the Dakota of uranium-bearing solutions from the Morrison; (3) the presence in the Dakota of permeable sandstone beds overlain by impermeable carbonaceous shale beds; and (4) the occurrence within the permeable Dakota sandstone beds of carbonaceous reducing material as bedding-plane laminae, or as pockets of carbonaceous trash. Most of the Dakota uranium deposits are found in the lower part of the formation in marginal-marine distributary-channel sandstones which were deposited in the backshore environment. However, the Hogback no. 4 (Hyde) Mine (Gallup district) occurs in sandy paludal shale of the backshore environment, and another deposit, the Silver Spur (Ambrosia Lake district), is found in what is interpreted to be a massive beach or barrier-bar sandstone of the foreshore environment in the upper part of the Dakota. The sedimentary depositional environment most favorable for the accumulation of uranium is that of backshore areas lateral to main distributary channels, where levee, splay, and some distributary-channel sandstones intertongue with gray carbonaceous shales and

Circulation and sedimentation in a tidal-influenced fjord lake: Lake McKerrow, New Zealand

Science.gov (United States)

Pickrill, R. A.; Irwin, J.; Shakespeare, B. S.

1981-01-01

Lake McKerrow is a tide-influenced fjord lake, separated from the open sea by a Holocene barrier spit. Fresh, oxygenated waters of the epilimnion overlie saline, deoxygenated waters of the hypolimnion. During winter, water from the Upper Hollyford River interflows along the pycnocline, depositing coarse silt on the steep delta and transporting finer sediment down-lake. An extensive sub-lacustrine channel system on the foreset delta slope is possibly maintained by turbidity currents. Saline waters of the hypolimnion are periodically replenished. During high tides and low lake levels saline water flows into the lake and downslope into the lake basin as a density current in a well defined channel.

Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars

OpenAIRE

Grotzinger, JP; Gupta, S; Malin, MC; Rubin, DM; Schieber, J; Siebach, K; Sumner, DY; Stack, KM; Vasavada, AR; Arvidson, RE; Calef, F; Edgar, L; Fischer, WF; Grant, JA; Griffes, J

2015-01-01

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittentl...

Forest blowdown and lake acidification

International Nuclear Information System (INIS)

Dobson, J.E.; Rush, R.M.; Peplies, R.W.

1990-01-01

The authors examine the role of forest blowdown in lake acidification. The approach combines geographic information systems (GIS) and digital remote sensing with traditional field methods. The methods of analysis consist of direct observation, interpretation of satellite imagery and aerial photographs, and statistical comparison of two geographical distributions-one representing forest blow-down and another representing lake chemistry. Spatial and temporal associations between surface water pH and landscape disturbance are strong and consistent in the Adirondack Mountains of New York. In 43 Adirondack Mountain watersheds, lake pH is associated with the percentage of the watershed area blown down and with hydrogen ion deposition (Spearman rank correlation coefficients of -0.67 and -0.73, respectively). Evidence of a temporal association is found at Big Moose Lake and Jerseyfield Lake in New York and the Lygners Vider Plateau of Sweden. They conclude that forest blowdown facilities the acidification of some lakes by altering hydrologic pathways so that waters (previously acidified by acid deposition and/or other sources) do not experience the neutralization normally available through contact with subsurface soils and bedrock. Increased pipeflow is suggested as a mechanism that may link the biogeochemical impacts of forest blowdown to lake chemistry

Aerial gamma ray and magnetic survey: Minnesota Project, Cheboygan and Alpena quadrangles, Michigan. Final report

International Nuclear Information System (INIS)

1980-02-01

The Cheboygan and Alpena 1 0 x 2 0 quadrangles of Michigan are covered almost everywhere (United States only) with Wisconsin age glacial deposits (moraines, outwash, leak deposits, etc.) of variable thickness. Where exposed, bedrock is of Early and Middle Paleozoic age, and consists almost entirely of limestone and dolomite. There are no uranium deposits (or occurrences) known within the study area, though the Elliot Lake quartz pebble conglomerate uranium deposit lies to the north in the Canadian section of the Blind River quadrangle. Magnetic data illustrate relative depth to magnetic basement in the area. Higher frequency/amplitude wavelengths in the eastern and northern sections of the lower peninsula may be a reflection of the lithologic character of the Precambrian bedrock. Twenty-four groups of uranium samples were defined as anomalies and are discussed briefly in this report. None of them are considered significant

Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada)

Science.gov (United States)

Cooke, Colin A.; Kirk, Jane L.; Muir, Derek C. G.; Wiklund, Johan A.; Wang, Xiaowa; Gleason, Amber; Evans, Marlene S.

2017-12-01

The mining and processing of the Athabasca oil sands (Alberta, Canada) has been occurring for decades; however, a lack of consistent regional monitoring has obscured the long-term environmental impact. Here, we present sediment core results to reconstruct spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region. Early mining operations (during the 1970s and 1980s) led to elevated V and Pb inputs to lakes located quality guidelines, and no spatial or temporal trends were observed in the frequency of guideline exceedence. Our results demonstrate that early mining efforts had an even greater impact on trace element cycling than has been appreciated previously, placing recent monitoring efforts in a critical long-term context.

Littoral sedimentation of rift lakes: an illustrated overview from the modern to Pliocene Lake Turkana (East African Rift System, Kenya)

Science.gov (United States)

Schuster, Mathieu; Nutz, Alexis

2015-04-01

Existing depositional models for rift lakes can be summarized as clastics transported by axial and lateral rivers, then distributed by fan-deltas and/or deltas into a standing water body which is dominated by settling of fine particles, and experiencing occasional coarser underflows. Even if known from paleolakes and modern lakes, reworking of clastics by alongshore drift, waves and storms are rarely considered in depositional models. However, if we consider the lake Turkana Basin (East African Rift System, Kenya) it is obvious that this vision is incomplete. Three representative time slices are considered here: the modern Lake Turkana, the Megalake Turkana which developed thanks to the African Humid Period (Holocene), and the Plio-Pleistocene highstand episodes of paleolake Turkana (Nachukui, Shungura and Koobi Fora Formations, Omo Group). First, remarkable clastic morphosedimentary structures such as beach ridges, spits, washover fans, lagoons, or wave-dominated deltas are very well developed along the shoreline of modern lake Turkana, suggesting strong hydrodynamics responsible for a major reworking of the fluvial-derived clastics all along the littoral zone (longshore and cross-shore transport) of the lake. Similarly, past hydrodynamics are recorded from prominent raised beach ridges and spits, well-preserved all around the lake, above its present water-level (~360 m asl) and up to ~455 m. These large-scale clastic morphosedimentary structures also record the maximum extent of Megalake Turkana during the African Humid Period, as well as its subsequent regression forced by the end of the Holocene climatic optimum. Several hundreds of meters of fluvial-deltaic-lacustrine deposits spanning the Pliocene-Pleistocene are exposed in the Turkana basin thanks to tectonic faulting. These deposits are world famous for their paleontological and archeological content that documents the very early story of Mankind. They also preserve several paleolake highstand episodes with

Lakes, Lagerstaetten, and Evolution

Science.gov (United States)

Kordesch, E. G.; Park, L. E.

2001-12-01

The diversity of terrestrial systems is estimated to be greater than in the marine realm. However no hard data yet exists to substantiate this claim. Ancient lacustrine deposits may preserve an exceptionally diverse fossil fauna and aid in determining continental faunal diversities. Fossils preserved in lake deposits, especially those with exceptional preservation (i.e. Konservat Lagerstaetten), may represent a dependable method for determining species diversity changes in the terrestrial environment because of their faunal completeness. Important Konservat Lagerstaetten, such as the Green River Formation (US) and Messel (Germany), both Eocene in age, are found in lake sediments and show a remarkable faunal diversity for both vertebrates and invertebrates. To date information from nearly 25 lake lagerstaetten derived from different types of lake basins from the Carboniferous to the Miocene have been collected and described. Carboniferous sites derive from the cyclothems of Midcontinent of the US while many Cenozoic sites have been described from North and South America as well as Europe and Australia. Asian sites contain fossils from the Mesozoic and Cenozoic. With this data, insight into the evolutionary processes associated with lake systems can be examined. Do lakes act as unique evolutionary crucibles in contrast to marine systems? The speciation of cichlid fishes in present-day African lakes appears to be very high and is attributed to the diversity of environments found in large rift lakes. Is this true of all ancient lakes or just large rift lakes? The longevity of a lake system may be an important factor in allowing speciation and evolutionary processes to occur; marine systems are limited only in the existence of environments as controlled by tectonics and sea level changes, on the order of tens of millions of years. Rift lakes are normally the longest lived in the millions of years. Perhaps there are only certain types of lakes in which speciation of

Water and chemical budgets of gravel pit lakes : Case studies of fluvial gravel pit lakes along the Meuse River (The Netherlands) and coastal gravel pit lakes along the Adriatic Sea (Ravenna, Italy)

NARCIS (Netherlands)

Mollema, P.N.

2016-01-01

Gravel pit lakes form when gravel is excavated from below the water table of a phreatic or shallow confined aquifer. Typically many of these lakes are concentrated along naturally occurring sedimentary gravel deposits in areas where gravel is needed for construction. Most gravel pit lakes are

Timing of lake-level changes for a deep last-glacial Lake Missoula: optical dating of the Garden Gulch area, Montana, USA

Science.gov (United States)

Smith, Larry N.; Sohbati, Reza; Buylaert, Jan-Pieter; Lian, Olav B.; Murray, Andrew; Jain, Mayank

2018-03-01

Glaciolacustrine sediments in the Clark Fork River valley at Garden Gulch, near Drummond, Montana, USA record highstand positions of the ice-dammed glacial Lake Missoula and repeated subaerial exposure. During these highstands the lake was at greater than 65% of its recognized maximum capacity. The initial lake transgression deposited a basal sand unit. Subsequent cycles of lake-level fluctuations are recorded by sequences of laminated and cross laminated silt, sand, and clay deformed by periglacial processes during intervening periods of lower lake levels. Optically stimulated luminescence (OSL) dating of quartz sand grains, using single-aliquot regenerative-dose procedures, was carried out on 17 samples. Comparison of infrared stimulated luminescence (IRSL) from K-rich feldspar to OSL from quartz for all the samples suggests that they were well bleached prior to deposition and burial. Ages for the basal sand and overlying glaciolacustrine exposure surfaces are indistinguishable within one standard deviation, and give a weighted mean age of 20.9 ± 1.3 ka (n = 11). Based on sedimentological and stratigraphic analysis we infer that the initial transgression, and at least six cycles of lake-level fluctuation, occurred over time scales of decades to ∼2 ka. Bioturbated sandy slopewash dated at 10.6 ± 0.9 ka and 11.9 ± 1.2 ka unconformably overlies the upper glaciolacustrine deposits. The uppermost sediments, above the glaciolacustrine section, are younger than the Glacier Peak tephra (13.7-13.4 cal ka B.P.), which was deposited across parts of the drained lake basin, but has not been found at Garden Gulch. Our study indicates that glacial Lake Missoula reached >65 percent of maximum capacity by about 20.9 ± 1.3 ka and either partially or completely drained twelve times from this position. Rapid lowering from the lake's highstand position due to ice-dam failure likely led to scour in the downstream portions of the glacial Lake Missoula basin and megafloods in the

Possible pitfalls in the search for uranium deposits using lake sediments and lake waters

International Nuclear Information System (INIS)

Levinson, A.A.; Bland, C.J.

1978-01-01

The organic-rich sediments from the centres of Canadian lakes are a valuable sampling medium in the search for uranium. However, because of the young age of hydromorphically transported uranium in these sediments, which must post-date the last period of glaciation, there has been insufficient time for the isotope 214 Bi to reach equilibrium with its ancestor 238 U. This results in equivalent uranium (eU) values significantly lower than actual uranium values determined by fluorometry or delayed neutron activation analysis. Radiometric ( 226 Ra) analyses of 12 centre-lake sediments from Seahorse Lake, Saskatchewan illustrate the potential pitfalls which may be encountered using gamma-ray spectrometry, as only 3-8% of the actual uranium present in most of the samples would have been detected. (author)

Sources of mercury in sediments, water, and fish of the lakes of Whatcom County, Washington

Science.gov (United States)

Paulson, Anthony J.

2004-01-01

Concerns about mercury (Hg) contamination in Lake Whatcom, Washington, were raised in the late 1990s after a watershed protection survey reported elevated concentrations of Hg in smallmouth bass. The U.S. Geological Survey, the Whatcom County Health Department, and the Washington State Department of Ecology (Ecology) cooperated to develop a study to review existing data and collect new data that would lead to a better understanding of Hg deposition to Lake Whatcom and other lakes in Whatcom County, Washington. A simple atmospheric deposition model was developed that allowed comparisons of the deposition of Hg to the surfaces of each lake. Estimates of Hg deposition derived from the model indicated that the most significant deposition of Hg would have occurred to the lakes north of the City of Bellingham. These lakes were in the primary wind pattern of two municipal waste incinerators. Of all the lakes examined, basin 1 of Lake Whatcom would have been most affected by the Hg emissions from the chlor-alkali plant and the municipal sewage-sludge incinerator in the City of Bellingham. The length-adjusted concentrations of Hg in largemouth and smallmouth bass were not related to estimated deposition rates of Hg to the lakes from local atmospheric sources. Total Hg concentrations in the surface sediments of Lake Whatcom are affected by the sedimentation of fine-grained particles, whereas organic carbon regulates the concentration of methyl-Hg in the surface sediments of the lake. Hg concentrations in dated sediment core samples indicate that increases in Hg sedimentation were largest during the first half of the 20th century. Increases in Hg sedimentation were smaller after the chlor-alkali plant and the incinerators began operating between 1964 and 1984. Analysis of sediments recently deposited in basin 1 of Lake Whatcom, Lake Terrell, and Lake Samish indicates a decrease in Hg sedimentation. Concentrations of Hg in Seattle precipitation and in tributary waters were

Advances in the exploration model for Athabasca unconformity uranium deposits

International Nuclear Information System (INIS)

Wheatley, K.; Murphy, J.; Leppin, M.; Cutts, C.; Climie, J.A.

1997-01-01

This paper covers the genetic model of ore formation and exploration techniques Uranerz Exploration and Mining is presently using to explore for unconformity uranium deposits in the deeper parts of the Athabasca Basin. The main objectives of this paper are: 1) to present a genetic model for unconformity uranium deposits which is being used in our current exploration strategy, and 2) to present the sequence of exploration techniques used by Uranerz to explore for uranium in areas of the Athabasca Basin with up to 1000 m of sandstone cover. The Athabasca unconformity deposits are located in northern Saskatchewan, Canada. Within the Precambrian Athabasca Basin, exploration companies have discovered 18 uranium deposits. These contain more than 500 million kilograms of uranium, with average grades ranging from 0.3 to 12%. Uranerz discovered the Key Lake deposits in 1975, currently the largest and richest open pit uranium mine in the world. Uranerz also holds interests in the Rabbit Lake, Midwest Lake and McArthur River deposits, all in Saskatchewan, and is also actively exploring for uranium worldwide. The first discovery in the eastern Athabasca Basin was in 1968 at Rabbit Lake, followed by Key Lake in 1975. Both deposits had surficial indicators, such as radioactive boulders, strong geochemical anomalies in the surrounding lakes and swamps, and well-defined geophysical signatures. After the Key Lake discovery, an exploration model was devised which incorporated the underlying graphitic horizon and its strong electro-magnetic signature. Since then, there have been numerous new discoveries made by systematically drilling along these electro-magnetic conductors. The advancements in geophysical and geochemical techniques have led to discoveries at increasing depths. In 1988, the McArthur River deposit was discovered at a depth of 500 m. (author). 6 refs

Conifer density within lake catchments predicts fish mercury concentrations in remote subalpine lakes

Science.gov (United States)

Eagles-Smith, Collin A.; Herring, Garth; Johnson, Branden L.; Graw, Rick

2016-01-01

Remote high-elevation lakes represent unique environments for evaluating the bioaccumulation of atmospherically deposited mercury through freshwater food webs, as well as for evaluating the relative importance of mercury loading versus landscape influences on mercury bioaccumulation. The increase in mercury deposition to these systems over the past century, coupled with their limited exposure to direct anthropogenic disturbance make them useful indicators for estimating how changes in mercury emissions may propagate to changes in Hg bioaccumulation and ecological risk. We evaluated mercury concentrations in resident fish from 28 high-elevation, sub-alpine lakes in the Pacific Northwest region of the United States. Fish total mercury (THg) concentrations ranged from 4 to 438 ng/g wet weight, with a geometric mean concentration (±standard error) of 43 ± 2 ng/g ww. Fish THg concentrations were negatively correlated with relative condition factor, indicating that faster growing fish that are in better condition have lower THg concentrations. Across the 28 study lakes, mean THg concentrations of resident salmonid fishes varied as much as 18-fold among lakes. We used a hierarchal statistical approach to evaluate the relative importance of physiological, limnological, and catchment drivers of fish Hg concentrations. Our top statistical model explained 87% of the variability in fish THg concentrations among lakes with four key landscape and limnological variables: catchment conifer density (basal area of conifers within a lake's catchment), lake surface area, aqueous dissolved sulfate, and dissolved organic carbon. Conifer density within a lake's catchment was the most important variable explaining fish THg concentrations across lakes, with THg concentrations differing by more than 400 percent across the forest density spectrum. These results illustrate the importance of landscape characteristics in controlling mercury bioaccumulation in fish.

PREDICTED SEDIMENTARY SECTION OF SUBGLACIAL LAKE VOSTOK

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G. I. Leychenkov

2012-01-01

Full Text Available In early February 2012, the drill hole at the Vostok Station encountered theLakeVostokwater. This step is important to study the lake composition including possible microbial life and to model subglacial environments however, the next ambitious target of the Vostok Drilling Project is sampling of bottom sediments, which contain the unique record of ice sheet evolution and environmental changes in centralAntarcticafor millions of years. In this connection, the forecast of sedimentary succession based on existing geophysical data, study of mineral inclusions in the accretion ice cores and tectonic models is important task. Interpretation of Airborne geophysical data suggests thatLakeVostokis the part of spacious rift system, which exists at least from Cretaceous. Reflection and refraction seismic experiments conducted in the southern part ofLakeVostokshow very thin (200–300 m stratified sedimentary cover overlying crystalline basement with velocity of 6.0–6.2 km/s. At present, deposition in southernLakeVostokis absent and similar conditions occurred likely at least last3 m.y. when ice sheet aboveLakeVostokchanged insignificantly. It can be also inferred that from the Late Miocene the rate of deposition inLakeVostokwas extremely low and so the most of sedimentary section is older being possibly of Oligocene to early to middle Miocene age when ice sheet oscillated and deposition was more vigorous. If so, the sampling of upper few meters of this condensed section is very informative in terms of history of Antarctic glaciation. Small thickness of sedimentary cover raises a question about existence of lake (rift depression during preglacial and early glacial times.

Surficial geologic map of Berrien County, Michigan, and the adjacent offshore area of Lake Michigan

Science.gov (United States)

Stone, Byron D.; Kincare, Kevin A.; O'Leary, Dennis W.; Newell, Wayne L.; Taylor, Emily M.; Williams, Van S.; Lundstrom, Scott C.; Abraham, Jared E.; Powers, Michael H.

2017-12-13

The surficial geologic map of Berrien County, southwestern Michigan (sheet 1), shows the distribution of glacial and postglacial deposits at the land surface and in the adjacent offshore area of Lake Michigan. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics, stratigraphic relationships, and age. Drill-hole information correlated in cross sections provides details of typical stratigraphic sequences that compose one or more penetrated geologic map units. A new bedrock geologic map (on sheet 2) includes contours of the altitude of the eroded top of bedrock and shows the distribution of middle Paleozoic shale and carbonate units in the subcrop. A sediment thickness map (also on sheet 2) portrays the extent of as much as 150 meters of surficial materials that overlie the bedrock surface.The major physical features of the county are related principally to deposits of the last Laurentide ice sheet that advanced and then retreated back through the region from about 19,000 to 14,000 radiocarbon years before present. Glacial and postglacial deposits underlie the entire county; shale bedrock crops out only in the adjacent offshore area on the bottom of Lake Michigan. All glacial deposits and glacial meltwater deposits in Berrien County are related to the late Wisconsinan glacial advances of the Lake Michigan ice lobe and its three regional recessional moraines, which cross the county as three north-northeast-trending belts.From east to west (oldest to youngest), the three moraine belts are known as the Kalamazoo, Valparaiso, and Lake Border morainic systems. The till-ridge morainic systems (Lake Border and local Valparaiso morainic systems) consist of multiple, elongate moraine ridges separated by till plains and lake-bottom plains. Tills in ground and end moraines in Berrien County are distinguished as informal units, and are correlated with three proposed regional till units in southwestern Michigan

Bathymetric Contour Maps of Lakes Surveyed in Iowa in 2005

Science.gov (United States)

Linhart, S.M.; Lund, K.D.

2008-01-01

The U.S. Geological Survey, in cooperation with the Iowa Department of Natural Resources, conducted bathymetric surveys on seven lakes in Iowa during 2005 (Arrowhead Pond, Central Park Lake, Lake Keomah, Manteno Park Pond, Lake Miami, Springbrook Lake, and Yellow Smoke Lake). The surveys were conducted to provide the Iowa Department of Natural Resources with information for the development of total maximum daily load limits, particularly for estimating sediment load and deposition rates. The bathymetric surveys provide a baseline for future work on sediment loads and deposition rates for these lakes. All of the lakes surveyed in 2005 are man-made lakes with fixed spillways. Bathymetric data were collected using boat-mounted, differential global positioning system, echo depth-sounding equipment, and computer software. Data were processed with commercial hydrographic software and exported into a geographic information system for mapping and calculating area and volume. Lake volume estimates ranged from 47,784,000 cubic feet (1,100 acre-feet) at Lake Miami to 2,595,000 cubic feet (60 acre-feet) at Manteno Park Pond. Surface area estimates ranged from 5,454,000 square feet (125 acres) at Lake Miami to 558,000 square feet (13 acres) at Springbrook Lake.

Aqueous-chlorine leaching of typical Canadian uranium ores

International Nuclear Information System (INIS)

Haque, K.E.

1982-01-01

Laboratory-scale aqueous-chlorine leaches were conducted on quartz-pebble conglomerates, pegmatite and vein-type ores. Optimum leach temperatures, pulp density and retention times were determined. Uranium extraction of 98 per cent was obtained from the Elliot Lake, Madawaska Mines of Bancroft and Rabbit Lake ores, 96 per cent from the Key Lake ore and 86 per cent from the Agnew Lake ore. However, tailings containing 15-20 pCi g -1 of radium-226 were obtained only from the Elliot Lake and Agnew lake quartz-pebble conglomerates and Bancroft pegmatite-type ores by second-stage leaches with HCl. The second-stage leach results indicate that multistage (3 or 4) acid-chloride or salt-chloride leaches might be effective to obtain tailings containing 15-20 pCi 226 Ra g -1 from the high-grade vein-type ores. Comparative reagent-cost estimates show that the sulphuric-acid leach process is far less expensive than aqueous chlorine leaching. Nevertheless, only the aqueous chlorine and acid-chloride leaches in stages are effective in producing tailings containing 15-20 pCi 226 Ra g -1 from the typical Canadian uranium ores. (Auth.)

Maggie's Struggle in Placing Her Existence at the Patriarchal Society in the Mill on the Floss by George Elliot

OpenAIRE

INDRIANI, FRISCA ARUM

2013-01-01

Novel The Mill on the Floss is one of George Elliot's novels that describing the situation and condition of the English society and also representing human life in 1837-1901 century which is called Victorian Era. At the moment, women were dominated by men and considered inferior. The condition is portrayed in this novel because the novel tells about the life of women, especially the life of the main female character, Maggie Tulliver, who is the victim of the standard beauty in her family. It ...

THE LATE QUATERNARY TECTONO-STRATIGRAPHIC EVOLUTION OF THE LAKE VAN, TURKEY

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Naci GÖRÜR

2015-12-01

Full Text Available Many of the terraces around the Lake Van record a relatively short period of the much lon- ger geological history of the Lake Van Basin. Their deposition took place during the last ca. 125 ka BP. They accumulated in a large array of shallow lake and lake margin environments, such as alluvial fan/braided river, beach, Gilbert-type delta, nearshore lake and offshore la- ke. Variability of their lithofacies provides evidence for climatic and tectonic controls of the- ir depositional conditions. During their deposition high relief areas in the watershed delive- red abundant detritus to the coastal areas of the lake. The sedimentation was therefore domi- nated by terrigenous clastic deposits. The highest concentrations  of the coarse clastic sedi- ments were at the mouths of the major streams where they formed Gilbert-type deltas. The- se river-dominated lacustrine deltas formed during rising lake levels and are relatively more abundant and thicker in the eastern margin of the lake, indicating that this margin mostly had a low-energy coast sheltered from the prevailing westerly winds. However, some areas of the same margin adjacent to deltas were also supplied with sediments by waves and storm-indu- ced longshore currents to form beaches. Storms and storm-generated  traction currents were perhaps active agents along the shores of the Lake Paleo-Van as suggested by the presence of the coarse-grained material in its nearshore facies. Somehow, during times of lake high- stands, turbidity currents seem not to have played an important role in the sediment transpor- tation along the lake margin, because the nearshore sediments hardly show any evidence of turbidite depositon, such as graded bedding and sole-marks. The offshore lake was relatively quite standing water, depositing laterally persistent, thinly-bedded to varved and fine-grained sandstones and mudstones in part with hydroplastic disruptions, such as slumps and convo- lute beddings. Because of

Mass-movement deposits in the lacustrine Eocene Green River Formation, Piceance Basin, western Colorado

Science.gov (United States)

Johnson, Ronald C.; Birdwell, Justin E.; Brownfield, Michael E.; Mercier, Tracey J.

2015-01-01

The Eocene Green River Formation was deposited in two large Eocene saline lakes, Lake Uinta in the Uinta and Piceance Basins and Lake Gosiute in the Greater Green River Basin. Here we will discuss mass-movement deposits in just the Piceance Basin part of Lake Uinta.

Description of the Panel Mine tailings area Rio Algom Ltd., Elliot Lake, Ontario, Canada

International Nuclear Information System (INIS)

Pullen, P.F.; Davis, J.B.

1982-01-01

The geomorphological setting of the Panel Mine tailings management area is described in relation to the geology of the Canadian Shield subject to recent glaciation and subsequent weathering and erosion in a humid climate with temperature extremes. For the deposition of uranium tailings a topographic low is chosen that is surrounded by bedrock with a low water permeability. This latter is evaluated by a detailed geological investigation and by drilling to investigate the relative pemeability of suspected seepage paths. It is estimated that seepage from the basin used will be less than one litre per second. Monitor wells have been established to determine the quality of the groundwater flows

Recent changes in mercury deposition and primary productivity inferred from sediments of lakes from the Hudson Bay Lowlands, Ontario, Canada

International Nuclear Information System (INIS)

Brazeau, Michelle L.; Poulain, Alexandre J.; Paterson, Andrew M.; Keller, Wendel; Sanei, Hamed; Blais, Jules M.

2013-01-01

Spatial and temporal changes in mercury (Hg) concentrations and organic carbon in lake sediments were examined from the Hudson Bay Lowlands to investigate whether Hg deposition to sediments is related to indicators of autochthonous production. Total organic carbon, “S2” carbon (mainly algal-derived OC), C:N and ∂ 13 C indicators suggest an increase in autochthonous productivity in recent decades. Up-core profiles of S2 concentrations and fluxes were significantly correlated with Hg suggesting that varying algal matter scavenging of Hg from the water column may play an important role in the temporal profiles of Hg throughout the sediment cores. Absence of significant relationship between total Hg and methyl Hg (MeHg) in surficial sediments suggested that inorganic Hg supply does not limit MeHg production. MeHg and OC were highly correlated across lakes in surface and deep sediment layers, indicating that sediment organic matter content explains part of the spatial variation in MeHg concentrations between lakes. - Highlights: ► Hg concentrations in sediment cores correlate with autochthonous organic production. ► Inorganic Hg supply in sediment does not limit MeHg production. ► Sediment methylmercury concentration is highly correlated with organic C content. - Increased mercury concentrations in lake sediment cores coincide with evidence of increased autochthonous production in lakes of the Hudson Bay Lowlands, Canada.

Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification

Science.gov (United States)

Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

2017-01-01

Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The ~7,700 calendar year B.P. climactic eruption of Mount Mazama, USA vented ~50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Mazama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ±1 m lateral and ±4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow- parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of pit craters caused by phreatic explosions, fractures and cracks caused by extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented

Monitoring climate signal transfer into the varved lake sediments of Lake Czechowskie, Poland

Science.gov (United States)

Groß-Schmölders, Miriam; Ott, Florian; Brykała, Dariusz; Gierszewski, Piotr; Kaszubski, Michał; Kienel, Ulrike; Brauer, Achim

2015-04-01

In 2012 we started a monitoring program at Lake Czechowskie, Poland, because the lake comprises a long Holocene time series of calcite varves until recent times. The aim of the program is to understand how environmental and climatic conditions influence the hydrological conditions and, ultimately, the sediment deposition processes of the lake. Lake Czechowskie is located in the north of Poland in the Pomeranian Lake District and is part of the national park Tuchola Forest. The landscape and the lake is formed by the glacier retreat after the last glaciation (Weichselian). Lake Czechowskie is a typical hardwater lake and has a length of 1.4 km, an average width of 600 m and a lake surface area of ca 4 km. The maximum depth of 32 m is reached in a rather small hollow in the eastern part of the lake. Two different types of sediment traps provide sediment samples with monthly resolution from different water depths (12m, 26m). In addition, hydrological data including water temperature in different depths, water inflow, throughflow and outflow and the depth of visibility are measured. These data allow to describe strength and duration of lake mixing in spring and autumn and its influence on sedimentation. The sediment samples were analyzed with respect to their dry weight (used to calculate mean daily sediment flux), their inorganic and organic carbon contents, the stable C- and O-isotopes of organic matter and calcite as well as N-isotopes of organic matter. For selected samples dominant diatom taxa are determined. Our first results demonstrate the strong influence of the long winter with ice cover until April in 2013 on the sedimentation. A rapid warming in only 9 days starting on April 9th from -0,3 C° to 15,2 C° resulted in fast ice break-up and a short but intensive lake mixing. In consequence of this short mixing period a strong algal bloom especially of Fragilaria and Crysophycea commenced in April and had its maximum in May. This bloom further induced biogenic

Wind-driven Water Bodies : a new paradigm for lake geology

Science.gov (United States)

Nutz, A.; Schuster, M.; Ghienne, J. F.; Roquin, C.; Bouchette, F. A.

2015-12-01

In this contribution we emphasize the importance in some lakes of wind-related hydrodynamic processes (fair weather waves, storm waves, and longshore, cross-shore and bottom currents) as a first order forcing for clastics remobilization and basin infill. This alternative view contrasts with more classical depositional models for lakes where fluvial-driven sedimentation and settling dominates. Here we consider three large lakes/paleo-lakes that are located in different climatic and geodynamic settings: Megalake Chad (north-central Africa), Lake Saint-Jean (Québec, Canada), and Lake Turkana (Kenya, East African Rift System). All of these three lake systems exhibit well developed modern and ancient high-energy littoral morphosedimentary structures which directly derive from wind-related hydrodynamics. The extensive paleo-shorelines of Megalake Chad are composed of beach-foredune ridges, spits, wave-dominated deltas, barriers, and wave-ravinment surface. For Lake Saint-Jean the influence of wind is also identified below the wave-base at lake bottom from erosional surfaces, and sediment drifts. In the Lake Turkana Basin, littoral landforms and deposits are identified for three different time intervals (today, Holocene, Plio-Pleistocene) evidencing that wind-driven hydrodynamics can be preserved in the geological record. Moreover, a preliminary global survey suggests that numerous modern lakes (remote sensing) and paleo-lakes (bibliographic review) behave as such. We thus coin the term "Wind-driven Water Bodies" (WWB) to refer to those lake systems where sedimentation (erosion, transport, deposition) is dominated by wind-induced hydrodynamics at any depth, as it is the case in the marine realm for shallow seas. Integrating wind forcing in lake models has strong implications for basin analysis (paleoenvironments and paleoclimates restitutions, resources exploration), but also for coastal engineering, wildlife and reservoirs management, or leisure activities.

Properties of soils and tree-wood tissue across a Lake States sulfate-deposition gradient. Forest Service resource bulletin

International Nuclear Information System (INIS)

Ohmann, L.F.; Grigal, D.F.

1991-01-01

There is general concern that atmospheric pollutants may be affecting the health of forests in the USA. The hypotheses tested were that the wet sulfate deposition gradient across the Lake States: (1) is reflected in the amount of accumulated sulfur in the forest floor-soil system and tree woody tissue and (2) is related to differences in tree radial increment. The authors present the properties of the soil and tree woody tissue (mostly chemical) on the study plots. Knowledge of the properties of soil and woody tree tissue is needed for understanding and interpreting relations between sulfate deposition, sulfur accumulation in the ecosystem, soil and tree chemistry, and tree growth and climatic variation. The report provides a summary of those data for study, analysis, and interpretation

Paleolimnological assessment of riverine and atmospheric pathways and sources of metal deposition at a floodplain lake (Slave River Delta, Northwest Territories, Canada)

Energy Technology Data Exchange (ETDEWEB)

MacDonald, Lauren A., E-mail: L7macdon@uwaterloo.ca [Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Wiklund, Johan A. [Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Elmes, Matthew C.; Wolfe, Brent B. [Department of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, ON N2L 3C5 (Canada); Hall, Roland I., E-mail: rihall@uwaterloo.ca [Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1 (Canada)

2016-02-15

Growth of natural resource development in northern Canada has raised concerns about the effects on downstream aquatic ecosystems, but insufficient knowledge of pre-industrial baseline conditions continues to undermine ability of monitoring programs to distinguish industrial-derived contaminants from those supplied by natural processes. Here, we apply a novel paleolimnological approach to define pre-industrial baseline concentrations of 13 priority pollutant metals and vanadium and assess temporal changes, pathways and sources of these metals at a flood-prone lake (SD2) in the Slave River Delta (NWT, Canada) located ~ 500 km north of Alberta's oil sands development and ~ 140 km south of a former gold mine at Yellowknife, NWT. Results identify that metal concentrations, normalized to lithium concentration, are not elevated in sediments deposited during intervals of high flood influence or low flood influence since onset of oil sands development (post-1967) relative to the 1920–1967 baseline established at SD2. When compared to a previously defined baseline for the upstream Athabasca River, several metal-Li relations (Cd, Cr, Ni, Zn, V) in post-1967 sediments delivered by floodwaters appear to plot along a different trajectory, suggesting that the Peace and Slave River watersheds are important natural sources of metal deposition at the Slave River Delta. However, analysis revealed unusually high concentrations of As deposited during the 1950s, an interval of very low flood influence at SD2, which corresponded closely with emission history of the Giant Mine gold smelter indicating a legacy of far-field atmospheric pollution. Our study demonstrates the potential for paleolimnological characterization of baseline conditions and detection of pollution from multiple pathways in floodplain ecosystems, but that knowledge of paleohydrological conditions is essential for interpretation of contaminant profiles. - Highlights: • We examine metal depositional history at a

Mass-movement and flood-induced deposits in Lake Ledro, southern Alps, Italy: implications for Holocene palaeohydrology and natural hazards

Directory of Open Access Journals (Sweden)

A. Simonneau

2013-03-01

Full Text Available High-resolution seismic profiles and sediment cores from Lake Ledro combined with soil and riverbed samples from the lake's catchment area are used to assess the recurrence of natural hazards (earthquakes and flood events in the southern Italian Alps during the Holocene. Two well-developed deltas and a flat central basin are identified on seismic profiles in Lake Ledro. Lake sediments have been finely laminated in the basin since 9000 cal. yr BP and frequently interrupted by two types of sedimentary events (SEs: light-coloured massive layers and dark-coloured graded beds. Optical analysis (quantitative organic petrography of the organic matter present in soil, riverbed and lacustrine samples together with lake sediment bulk density and grain-size analysis illustrate that light-coloured layers consist of a mixture of lacustrine sediments and mainly contain algal particles similar to the ones observed in background sediments. Light-coloured layers thicker than 1.5 cm in the main basin of Lake Ledro are synchronous to numerous coeval mass-wasting deposits remoulding the slopes of the basin. They are interpreted as subaquatic mass-movements triggered by historical and pre-historical regional earthquakes dated to AD 2005, AD 1891, AD 1045 and 1260, 2545, 2595, 3350, 3815, 4740, 7190, 9185 and 11 495 cal. yr BP. Dark-coloured SEs develop high-amplitude reflections in front of the deltas and in the deep central basin. These beds are mainly made of terrestrial organic matter (soils and lignocellulosic debris and are interpreted as resulting from intense hyperpycnal flood event. Mapping and quantifying the amount of soil material accumulated in the Holocene hyperpycnal flood deposits of the sequence allow estimating that the equivalent soil thickness eroded over the catchment area reached up to 5 mm during the largest Holocene flood events. Such significant soil erosion is interpreted as resulting from the combination of heavy rainfall and snowmelt. The

Acidic deposition: State of science and technology. Report 11. Historical changes in surface-water acid-base chemistry in response to acidic deposition. Final report

International Nuclear Information System (INIS)

Sullivan, T.J.; Small, M.J.; Kingston, J.C.; Bernert, J.A.; Thomas, D.R.

1990-09-01

The objectives of the analyses reported in the State of Science report are to: identify the lake and stream populations in the United States that have experienced chronic changes in biologically significant constituents of surface water chemistry (e.g. pH, Al) in response to acidic deposition; quantify biologically meaningful historical changes in chronic surface water chemistry associated with acidic deposition, with emphasis on ANC, pH, and Al; estimate the proportion of lakes nor acidic that were not acidic in pre-industrial times; estimate the proportional response of each of the major chemical constituents that have changed in response to acidic deposition using a subset of statistically selected Adirondack lakes for which paleolimnological reconstructions of pre-industrial surface water chemistry have been performed; evaluate and improve, where appropriate and feasible, empirical models of predicting changes in ANC; and evaluate the response of seepage lakes to acidic deposition

A 31,000 year record of paleoenvironmental and lake-level change from Harding Lake, Alaska, USA

Science.gov (United States)

Finkenbinder, Matthew S.; Abbott, Mark B.; Edwards, Mary E.; Langdon, Catherine T.; Steinman, Byron A.; Finney, Bruce P.

2014-03-01

Physical and geochemical proxy analyses of sediment cores from Harding Lake in central Alaska are used to reconstruct paleoenvironmental change and millennial scale fluctuations in lake level for the last ˜31,000 years. We analyzed a composite 422 cm core from the lake depocenter (42.1 m water depth) and identified 4 distinct lithologic units based on variability in dry bulk density, organic matter, biogenic silica, carbon to nitrogen mass ratios (C/N), organic matter carbon isotopes (δ13C), pollen, and elemental abundances via scanning X-ray fluorescence, with age control provided by 16 Accelerator Mass Spectrometry radiocarbon dates and 210Pb dating. In addition, we analyzed a transect of cores from 7.1 m, 10.75 m, 15.91 m, and 38.05 m water depths to identify lake level fluctuations and to characterize sediment compositional changes as a function of water depth. Organic matter content and magnetic susceptibility values in surface sediments from all transect cores show a strong correlation with water depth. Interpretation of four lithologic units with well-dated contacts produced a record of water-depth variations that is consistent with independent climate records from eastern Beringia. Basal coarse-grained sediments (quartz pebble diamicton) were deposited prior to 30,700 calendar years before present (yr BP), possibly from fluvial reworking or deflation during a period of severe aridity. Unit 1 sediments were deposited between 30,700 and 15,700 yr BP and are characterized by a low organic matter content, a high magnetic susceptibility, and low biogenic silica concentrations resulting from very low lake levels, low terrestrial and in-lake productivity and a high flux of clastic sediment. An abrupt increase in organic matter and biogenic silica concentration marks the transition into Unit 2 sediments, which were deposited between 15,700 and 9,400 yr BP when lake levels were higher and variable (relative to Unit 1). The transition to full interglacial

Map showing thickness of saturated Quaternary deposits, Sugar House quadrangle, Salt Lake County, Utah, February 1972

Science.gov (United States)

Mower, R.W.

1973-01-01

Saturated Quaternary deposits in the Sugar Horse quadrangle supply significant quantities of water to wells from which water is withdrawn for domestic, municipal, industrial, and irrigation uses. The deposits consist of clay, silt, sand, and gravel; individual beds range from a few inches to several tens of feet thick. The principal aquifer, which is almost completely within the Quaternary deposits, supplied about 4 percent, or 9,000 acre-feet, of the municipal and industrial water used annually in Salt Lake County during 1964-68.As a general rule, more water is stored and more water will be yielded to a well where aquifers are thicker. This map can be used as a general guide to those areas where greatest amounts of water are stored in the aquifer, and where yields to wells may be greater. Local variations in the ability of saturated deposits to transmit water can alter the general relationship between aquifer thickness and yield of wells.The thickness of saturated Quaternary deposits within the area of the Sugar Horse quadrangle ranges from zero to about 650 feet, as shown on the map. The thickest section of these deposits is near the southwestern corner of the quadrangle, and the thinnest section is along the mountain front adjacent to the approximate eastern limit of saturated Quaternary deposits.The thickness of saturated Quaternary deposits shown on this map is based on drillers’ logs for 55 deep wells (which show the thickness of the Quaternary deposits) and on water-level measurements made in February 1972 in wells in unconfined shallow aquifers.Reports in the following list of selected references contain other information about the saturated Quaternary deposits in this and adjacent parts of Jordan Valley, Utah. The basic-data reports and releases contain well logs, water-level measurements, and other types of basic ground-water data. The interpretive repots contain discussions of the occurrence of ground water, tests to determine hydraulic properties of

Lake-sediment record of PAH, mercury, and fly-ash particle deposition near coal-fired power plants in Central Alberta, Canada.

Science.gov (United States)

Barst, Benjamin D; Ahad, Jason M E; Rose, Neil L; Jautzy, Josué J; Drevnick, Paul E; Gammon, Paul R; Sanei, Hamed; Savard, Martine M

2017-12-01

We report a historical record of atmospheric deposition in dated sediment cores from Hasse Lake, ideally located near both currently and previously operational coal-fired power plants in Central Alberta, Canada. Accumulation rates of spheroidal carbonaceous particles (SCPs), an unambiguous marker of high-temperature fossil-fuel combustion, in the early part of the sediment record (pre-1955) compared well with historical emissions from one of North America's earliest coal-fired power plants (Rossdale) located ∼43 km to the east in the city of Edmonton. Accumulation rates in the latter part of the record (post-1955) suggested inputs from the Wabamun region's plants situated ∼17-25 km to the west. Increasing accumulation rates of SCPs, polycyclic aromatic hydrocarbons (PAHs) and Hg coincided with the previously documented period of peak pollution in the Wabamun region during the late 1960s to early 1970s, although Hg deposition trends were also similar to those found in western North American lakes not directly affected by point sources. A noticeable reduction in contaminant inputs during the 1970s is attributed in part to technological improvements and stricter emission controls. The over one hundred-year historical record of coal-fired power plant emissions documented in Hasse Lake sediments has provided insight into the impact that both environmental regulations and changes in electricity output have had over time. This information is crucial to assessing the current and future role of coal in the world's energy supply. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Atmospheric deposition, water-quality, and sediment data for selected lakes in Mount Rainer, North Cascades, and Olympic National Parks, Washington, 2008-10

Science.gov (United States)

Sheibley, Rich W.; Foreman, James R.; Moran, Patrick W.; Swarzenski, Peter W.

2012-01-01

To evaluate the potential effect from atmospheric deposition of nitrogen to high-elevation lakes, the U.S. Geological Survey partnered with the National Park Service to develop a "critical load" of nitrogen for sediment diatoms. A critical load is defined as the level of a given pollutant (in this case, nitrogen) at which detrimental effects to a target endpoint (sediment diatoms) result. Because sediment diatoms are considered one of the "first responders" to ecosystem changes from nitrogen, they are a sensitive indicator for nitrogen deposition changes in natural areas. This report presents atmospheric deposition, water quality, sediment geochronology, and sediment diatom data collected from July 2008 through August 2010 in support of this effort.

The geology of the Cluff Lake uranium deposits

International Nuclear Information System (INIS)

Harper, C.T.

1978-01-01

The uranium deposits discovered by Amok (Canada) Ltd. in the Cluff Lake area of northwestern Saskatchewan occur at or near the southern edge of the uplifted basement core of the Carswell circular structure. Two types of mineralization, distinguishable by their geological and structural setting and mineral paragenesis, have been recognized. The N-Claude type is characterized by a relatively simple mineral assemblage, consisting of uraninite or pitchblende with coffinite, and is accompanied by variable amounts of graphite and organic matter, and Fe, Cu, Pb and Mo sulphides. Both N and Claude orebodies occur within quartzofeldpathic gneisses of the basement core. On the other hand, the D-type ore has a complex mineral assemblage consisting of: uraninite, pitchblende, tucholite and coffinite, along with native gold and selenium; gold tellurides, and selenides of Pb, Bi, Ni and Co; sulphides of Fe, Cu and Pb; and organic matter. The D orebody occurs within carbonaceous shales at the base of the Athabasca Formation as well as in fault zones in regolithic quartzofeldspathic gneisses above the inverted unconformity. An age of 1050 m.y., which is consistent with a period (circa 1200-1000 m.y.) of widespread hydrothermal activity and uranium mineralization or reworking within and adjacent to the Athabasca Basin, has been obtained from uranium mineralization from the D orebody. Later reworking (circa 470 m.y.) of the mineralization occurred at the intersection of older mineralized shear zones with radial faults produced during meteorite impact. (auth)

Reconstruction of historical atmospheric Pb using Dutch urban lake sediments: A Pb isotope study

Energy Technology Data Exchange (ETDEWEB)

Walraven, N., E-mail: n.walraven@geoconnect.nl [GeoConnect, Meester Dekkerstraat 4, 1901 PV Castricum (Netherlands); Os, B.J.H. van, E-mail: b.vanos@rce.nl [Rijksdienst voor Archeologie, Cultuurlandschap en Monumenten, P.O. Box 1600, 3800 BP Amersfoort (Netherlands); Klaver, G.Th., E-mail: g.klaver@brgm.nl [BRGM, 3 avenue Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2 (France); Middelburg, J.J., E-mail: j.b.m.middelburg@uu.nl [University Utrecht, Faculty of Geosciences, P.O. Box 80021, 3508 TA Utrecht (Netherlands); Davies, G.R., E-mail: g.r.davies@vu.nl [VU University Amsterdam, Faculty of Earth and Life Sciences, Petrology, De Boelelaan 1085, 1081 HV Amsterdam (Netherlands)

2014-06-01

Lake sediments provide a record of atmospheric Pb deposition and changes in Pb isotope composition. To our knowledge, such an approach has not previously been performed in The Netherlands or linked to national air monitoring data. Results are presented for Pb content and isotope composition of {sup 137}Cs dated lake sediments from 2 Dutch urban lakes. Between 1942 and 2002 A.D. anthropogenic atmospheric Pb deposition rates in the two lakes varied from 12 ± 2 to 69 ± 16 μg cm{sup −2} year{sup −1}. The rise and fall of leaded gasoline is clearly reflected in the reconstructed atmospheric Pb deposition rates. After the ban on leaded gasoline, late 1970s/early 1980s, atmospheric Pb deposition rates decreased rapidly in the two urban lakes and the relative contributions of other anthropogenic Pb sources — incinerator ash (industrial Pb) and coal/galena — increased sharply. Atmospheric Pb deposition rates inferred from the lake record a clear relationship with nearby measured annual mean air Pb concentrations. Based on this relationship it was estimated that air Pb concentrations between 1942 and 2002 A.D. varied between 5 and 293 ng/m{sup 3}. - Highlights: • Sixty years of atmospheric Pb was reconstructed using urban lake sediments. • Stable Pb isotopes were applied to determine Pb sources in urban lakes. • The rise and fall of leaded gasoline is clearly reflected in the lake sediments. • Other dominant anthropogenic Pb sources are incinerator ash and coal/galena. • The lake Pb record shows a clear relationship with measured air Pb concentrations.

Increase deposition of organic matter, polychlorinated biphenyls, and cadmium by zebra mussels (Dreissena polymorpha) in western Lake Erie

Energy Technology Data Exchange (ETDEWEB)

Dobson, E. P; Mackie, G. L. [Guelph Univ., Dept. of Zoology, ON (Canada)

1998-05-01

Biodeposition of polychlorinated biphenyls (PCBs)and cadmium by zebra mussels in the western basin of Lake Erie was investigated using sediment traps, and compared to natural rates of sedimentation. On a per unit area of organic matter, deposition rates by zebra mussels up to eight to ten times higher than natural rates of sedimentation were found. These results suggest that zebra mussels are altering contaminant movement in western Lake Erie. At the same time, it was also suggested that the net effect of biodeposition may not be as great as shown in this study since only the effects of zebra mussels on the flux of the contaminants was examined and the re-suspension factor was not considered. It was recommended that to better understand the overall effects of zebra mussels on contaminant dynamics in aquatic environments, future studies should incorporate the re-suspension factors. 27 refs., 8 tabs., 3 figs.

Surficial geology and stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

Science.gov (United States)

Reheis, Marith C.; Redwine, Joanna R.; Wan, Elmira; McGeehin, John P.; VanSistine, D. Paco

2014-01-01

Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault. Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit

Spatially Modeling the Impact of Terrain on Wind Speed and Dry Particle Deposition Across Lake Perris in Southern California to Determine In Situ Sensor Placement

Science.gov (United States)

Brooks, A. N.

2014-12-01

While developed countries have implemented engineering techniques and sanitation technologies to keep water resources clean from runoff and ground contamination, air pollution and its contribution of harmful contaminants to our water resources has yet to be fully understood and managed. Due to the large spatial and temporal extent and subsequent computational intensity required to understand atmospheric deposition as a pollutant source, a geographic information system (GIS) was utilized. This project developed a multi-step workflow to better define the placement of in situ sensors on Lake Perris in Southern California. Utilizing a variety of technologies including ArcGIS 10.1 with 3D and Spatial Analyst extensions and WindNinja, the impact of terrain on wind speed and direction was simulated and the spatial distribution of contaminant deposition across Lake Perris was calculated as flux. Specifically, the flux of particulate matter (PM10) at the air - water interface of a lake surface was quantified by season for the year of 2009. Integrated Surface Hourly (ISH) wind speed and direction data and ground station air quality measurements from the California Air Resources Board were processed and integrated for use within ModelBuilder. Results indicate that surface areas nearest Alessandro Island and the dam of Lake Perris should be avoided when placing in situ sensors. Furthermore, the location of sensor placement is dependent on seasonal fluctuations of PM10 which can be modeled using the techniques used in this study.

Converting the Key Lake mill process for McArthur River ore

Energy Technology Data Exchange (ETDEWEB)

Rodgers, C. [McArthur River Operation, Cameco Corporation, Saskatoon, Saskatchewan (Canada)

2000-07-01

The Key Lake mill was commissioned in 1983 to process the two Key Lake ore deposits. With the depletion of these ore bodies in 1999, the plant was converted to mill the exceptionally rich McArthur River deposit located seventy eight kilometers northeast of the Key Lake mine site. This paper describes in detail the Key Lake milling process. The mill consists of a grinding circuit, a leach/counter current decantation circuit, a solvent extraction circuit, a yellowcake precipitation/calciner circuit, an ammonium sulphate crystallization circuit, and a waste treatment circuit. The paper also describes process changes to handle McArthur River ore, including the ore receiving station. (author)

Freshwater diatomite deposits in the western United States

Science.gov (United States)

Wallace, Alan R.; Frank, David G.; Founie, Alan

2006-01-01

Freshwater diatomite deposits in the Western United States are found in lake beds that formed millions of years ago. These diatom-rich sediments are among the Nation's largest commercial diatomite deposits. Each deposit contains billions of tiny diatom skeletons, which are widely used for filtration, absorption, and abrasives. New studies by the U.S. Geological Survey (USGS) are revealing how ancient lakes in the Western States produced such large numbers of diatoms. These findings can be used by both land-use managers and mining companies to better evaluate diatomite resources in the region.

Stable isotope ratios in swale sequences of Lake Superior as indicators of climate and lake level fluctuations during the Late Holocene

Science.gov (United States)

Sharma, Shruti; Mora, G.; Johnston, J.W.; Thompson, T.A.

2005-01-01

Beach ridges along the coastline of Lake Superior provide a long-term and detailed record of lake level fluctuations for the past 4000 cal BP. Although climate change has been invoked to explain these fluctuations, its role is still in debate. Here, we reconstruct water balance by employing peat samples collected from swale deposits present between beach ridge sequences at two locations along the coastline of Lake Superior. Carbon isotope ratios for Sphagnum remains from these peat deposits are used as a proxy for water balance because the presence or absence of water films on Sphagnum controls the overall isotope discrimination effects. Consequently, increased average water content in Sphagnum produces elevated ??13C values. Two maxima of Sphagnum ??13C values interpreted to reflect wetter conditions prevailed from 3400 to 2400 cal BP and from about 1900 to 1400 cal BP. There are two relatively short drier periods as inferred from low Sphagnum ??13C values: one is centered at about 2300 cal BP, and one begins at 1400 cal BP. A good covariance was found between Sphagnum ??13C values and reconstructed lake-levels for Lake Michigan in which elevated carbon isotope values correlate well with higher lake levels. Based on this covariance, we conclude that climate exerts a strong influence on lake levels in Lake Superior for the past 4000 cal BP. ?? 2005 Elsevier Ltd. All rights reserved.

A fluvial mercury budget for Lake Ontario.

Science.gov (United States)

Denkenberger, Joseph S; Driscoll, Charles T; Mason, Edward; Branfireun, Brian; Warnock, Ashley

2014-06-03

Watershed mercury (Hg) flux was calculated for ten inflowing rivers and the outlet for Lake Ontario using empirical measurements from two independent field-sampling programs. Total Hg (THg) flux for nine study watersheds that directly drain into the lake ranged from 0.2 kg/yr to 13 kg/yr, with the dominant fluvial THg load from the Niagara River at 154 kg/yr. THg loss at the outlet (St. Lawrence River) was 68 kg/yr and has declined approximately 40% over the past decade. Fluvial Hg inputs largely (62%) occur in the dissolved fraction and are similar to estimates of atmospheric Hg inputs. Fluvial mass balances suggest strong in-lake retention of particulate Hg inputs (99%), compared to dissolved total Hg (45%) and methyl Hg (22%) fractions. Wetland land cover is a good predictor of methyl Hg yield for Lake Ontario watersheds. Sediment deposition studies, coupled atmospheric and fluvial Hg fluxes, and a comparison of this work with previous measurements indicate that Lake Ontario is a net sink of Hg inputs and not at steady state likely because of recent decreases in point source inputs and atmospheric Hg deposition.

The McClean Lake uranium project

International Nuclear Information System (INIS)

Blaise, J.R.

2001-01-01

The McClean Lake Uranium Project, located in the northern part of Saskatchewan, consists of five uranium deposits, Jeb - Sue A - Sue B - Sue C - McClean, scattered in three different locations on the mineral lease. On 16 March 1995, COGEMA Resources Inc and its partners, Denison Mines Ltd and OURD (Canada) Co Ltd, made the formal decision to develop the McClean Lake Project. Construction of the mine and mill started during summer 1995 and should be finished by mid 1997. Mining of the first deposit, Jeb started in 1996, ore being currently mined. The start of the yellowcake production is scheduled to start this fall. (author)

Surficial geologic map of the Red Rock Lakes area, southwest Montana

Science.gov (United States)

Pierce, Kenneth L.; Chesley-Preston, Tara L.; Sojda, Richard L.

2014-01-01

The Centennial Valley and Centennial Range continue to be formed by ongoing displacement on the Centennial fault. The dominant fault movement is downward, creating space in the valley for lakes and the deposition of sediment. The Centennial Valley originally drained to the northeast through a canyon now represented by a chain of lakes starting with Elk Lake. Subsequently, large landslides blocked and dammed the drainage, which created Lake Centennial, in the Centennial Valley. Sediments deposited in this late Pleistocene lake underlie much of the valley floor and rest on permeable sand and gravel deposited when the valley drained to the northeast. Cold Pleistocene climates enhanced colluvial supply of gravelly sediment to mountain streams and high peak flows carried gravelly sediment into the valley. There, the lower gradient of the streams resulted in deposition of alluvial fans peripheral to Lake Centennial as the lake lowered through time to the level of the two present lakes. Pleistocene glaciers formed in the high Centennial Range, built glacial moraines, and also supplied glacial outwash to the alluvial fans. Winds from the west and south blew sand to the northeast side of the valley building up high dunes. The central part of the map area is flat, sloping to the west by only 0.6 meters in 13 kilometers (2 feet in 8 miles) to form a watery lowland. This lowland contains Upper and Lower Red Rock Lakes, many ponds, and peat lands inside the “water plane,” above which are somewhat steeper slopes. The permeable sands and gravels beneath Lake Centennial sediments provide a path for groundwater recharged from the adjacent uplands. This groundwater leaks upward through Lake Centennial sediments and sustains wetland vegetation into late summer. Upper and Lower Red Rock Lakes are formed by alluvial-fan dams. Alluvial fans converge from both the south and the north to form outlet thresholds that dam the two shallow lakes upstream. The surficial geology aids in

Modern process study on Chen Co and Ranwu Lake of Tibetan Plateau

Science.gov (United States)

Ju, J.

2013-12-01

Lakes are important junctions of geospheres. There are many lakes distributed on the Tibetan Plateau (TP). Lake sediment is one of the important media for retrieving the past environmental changes. Because of the uniqueness of environment of the TP, sediment, water and ecological system in lakes has local characteristic inevitably. Modern process research on different lakes will benefit interpreting the proxies more accurately. The development of observation station makes the observation and sampling more convenient. Modern process of lakes can be fulfilled in two ways, spatial or seasonal variation study, with a same aim finding out the dominant factors controlling the variations. Chen Co is a closed lake locating at inland area of southern Tibet. Ranwu Lake is an open lake locating at outflow area of SE Tibet. In this study, I studied the spatial and (or) seasonal variation of lake water and sediment in the two distinct types of lakes to make clear the mechanism of modern process. Particular attention was given to the pattern and degree of influence of rivers supplied by glaciers on lakes. Preliminary conclusions are outlined as follow: (1) In the lakes with glacier melt supplying rivers, the patterns of supply of the rivers to the lake are different. In close lake Chen Co, the influence of glacier melt is mainly reflected in the south lake area. In the open lake Ranwu Lake, the influence is comprehensive and direct. This difference influencing patterns how the lake sediments reflected the glacier melt under the past environmental changes. (2) The supply of Kaluxiong Qu River, supplied mainly by glacier melt, to Chen co has North-South difference: more directly to south lake area, reflecting by lower value of conductivity and pH, finer grain size and west to east transporting trend, greater deposition rate, more allogenic fine sediments, not obvious biological and endogenic deposition there. This enlightens the site selection for lake cores and interpretation of

Questa baseline and premining ground-water quality investigation. 8. Lake-sediment geochemical record from 1960 to 2002, Eagle Rock and Fawn Lakes, Taos County, New Mexico

Science.gov (United States)

Church, S.E.; Fey, D.L.; Marot, M.E.

2005-01-01

Geochemical studies of lake sediment from Eagle Rock Lake and upper Fawn Lake were conducted to evaluate the effect of mining at the Molycorp Questa porphyry molybdenum deposit located immediately north of the Red River. Two cores were taken, one from each lake near the outlet where the sediment was thinnest, and they were sampled at 1-cm intervals to provide geochemical data at less than 1-year resolution. Samples from the core intervals were digested and analyzed for 34 elements using ICP-AES (inductively coupled plasma-atomic emission spectrometry). The activity of 137Cs has been used to establish the beginning of sedimentation in the two lakes. Correlation of the geochemistry of heavy-mineral suites in the cores from both Fawn and Eagle Rock Lakes has been used to develop a sedimentation model to date the intervals sampled. The core from upper Fawn Lake, located upstream of the deposit, provided an annual sedimentary record of the geochemical baseline for material being transported in the Red River, whereas the core from Eagle Rock Lake, located downstream of the deposit, provided an annual record of the effect of mining at the Questa mine on the sediment in the Red River. Abrupt changes in the concentrations of many lithophile and deposit-related metals occur in the middle of the Eagle Rock Lake core, which we correlate with the major flood-of-record recorded at the Questa gage at Eagle Rock Lake in 1979. Sediment from the Red River collected at low flow in 2002 is a poor match for the geochemical data from the sediment core in Eagle Rock Lake. The change in sediment geochemistry in Eagle Rock Lake in the post-1979 interval is dramatic and requires that a new source of sediment be identified that has substantially different geochemistry from that in the pre-1979 core interval. Loss of mill tailings from pipeline breaks are most likely responsible for some of the spikes in trace-element concentrations in the Eagle Rock Lake core. Enrichment of Al2O3, Cu, and Zn

Contemporaneous deposition of phyllosilicates and sulfates: Using Australian acidic saline lake deposits to describe geochemical variability on Mars

Science.gov (United States)

Baldridge, A.M.; Hook, S.J.; Crowley, J.K.; Marion, G.M.; Kargel, J.S.; Michalski, J.L.; Thomson, B.J.; de Souza, Filho C.R.; Bridges, N.T.; Brown, A.J.

2009-01-01

Studies of the origin of the Martian sulfate and phyllosilicate deposits have led to the hypothesis that there was a marked, global-scale change in the Mars environment from circum-neutral pH aqueous alteration in the Noachian to an acidic evaporitic system in the late Noachian to Hesperian. However, terrestrial studies suggest that two different geochemical systems need not be invoked to explain such geochemical variation.Western Australian acidic playa lakes have large pH differences separated vertically and laterally by only a few tens of meters, demonstrating how highly variable chemistries can coexist over short distances in natural environments. We suggest diverse and variable Martian aqueous environments where the coetaneous formation of phyllosilicates and sulfates at the Australian sites are analogs for regions where phyllosilicates and sulfates coexist on Mars. In these systems, Fe and alkali earth phyllosilicates represent deep facies associated with upwelling neutral to alkaline groundwater, whereas aluminous phyllosilicates and sulfates represent near-surface evaporitic facies formed from more acidic brines. Copyright 2009 by the American Geophysical Union.

Late Quaternary stratigraphy, sedimentology, and geochemistry of an underfilled lake basin in the Puna (north-west Argentina)

Science.gov (United States)

McGlue, Michael M.; Cohen, Andrew S.; Ellis, Geoffrey S.; Kowler, Andrew L.

2013-01-01

Depositional models of ancient lakes in thin-skinned retroarc foreland basins rarely benefit from appropriate Quaternary analogues. To address this, we present new stratigraphic, sedimentological and geochemical analyses of four radiocarbon-dated sediment cores from the Pozuelos Basin (PB; northwest Argentina) that capture the evolution of this low-accommodation Puna basin over the past ca. 43 cal kyr. Strata from the PB are interpreted as accumulations of a highly variable, underfilled lake system represented by lake-plain/littoral, profundal, palustrine, saline lake and playa facies associations. The vertical stacking of facies is asymmetric, with transgressive and thin organic-rich highstand deposits underlying thicker, organic-poor regressive deposits. The major controls on depositional architecture and basin palaeogeography are tectonics and climate. Accommodation space was derived from piggyback basin-forming flexural subsidence and Miocene-Quaternary normal faulting associated with incorporation of the basin into the Andean hinterland. Sediment and water supply was modulated by variability in the South American summer monsoon, and perennial lake deposits correlate in time with several well-known late Pleistocene wet periods on the Altiplano/Puna plateau. Our results shed new light on lake expansion–contraction dynamics in the PB in particular and provide a deeper understanding of Puna basin lakes in general.

Net atmospheric mercury deposition to Svalbard: Estimates from lacustrine sediments

Science.gov (United States)

Drevnick, Paul E.; Yang, Handong; Lamborg, Carl H.; Rose, Neil L.

2012-11-01

In this study we used lake sediments, which faithfully record Hg inputs, to derive estimates of net atmospheric Hg deposition to Svalbard, Norwegian Arctic. With the exception of one site affected by local pollution, the study lakes show twofold to fivefold increases in sedimentary Hg accumulation since 1850, likely due to long-range atmospheric transport and deposition of anthropogenic Hg. Sedimentary Hg accumulation in these lakes is a linear function of the ratio of catchment area to lake area, and we used this relationship to model net atmospheric Hg flux: preindustrial and modern estimates are 2.5 ± 3.3 μg m-2 y-1 and 7.0 ± 3.0 μg m-2 y-1, respectively. The modern estimate, by comparison with data for Hg wet deposition, indicates that atmospheric mercury depletion events (AMDEs) or other dry deposition processes contribute approximately half (range 0-70%) of the net flux. Hg from AMDEs may be moving in significant quantities into aquatic ecosystems, where it is a concern because of contamination of aquatic food webs.

AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

Science.gov (United States)

Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

1996-01-01

A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in

Can There Ever Be Enough to Impact Water Quality? Evaluating BMPs in Elliot Ditch, Indiana Using the LTHIA-LID Model

Science.gov (United States)

Rahman, M. S.; Hoover, F. A.; Bowling, L. C.

2017-12-01

Elliot Ditch is an urban/urbanizing watershed located in the city of Lafayette, IN, USA. The city continues to struggle with stormwater management and combined sewer overflow (CSO) events. Several best-management practices (BMP) such as rain gardens, green roofs, and bioswales have been implemented in the watershed, but the level of adoption needed to achieve meaningful impact is currently unknown. This study's goal is to determine what level of BMP coverage is needed to impact water quality, whether meaningful impact is determined by achieving water quality targets or statistical significance. A power analysis was performed using water quality data for total suspended solids (TSS), E.coli, total phosphorus (TP) and nitrate (NO3-N) from Elliot Ditch from 2011 to 2015. The minimum detectable difference (MDD) was calculated as the percent reduction in load needed to detect a significant change in the watershed. The water quality targets were proposed by stakeholders as part of a watershed management planning process. The water quality targets and the MDD percentages were then compared to simulated load reductions due to BMP implementation using the Long-term Hydrologic Impact Assessment-Low Impact Development (LTHIA-LID) model. Seven baseline model scenarios were simulated by implementing the maximum number of each of six types of BMPs (rain barrels, permeable patios, green roofs, grassed swale/bioswales, bioretention/rain gardens, and porous pavement), as well as all the practices combined in the watershed. These provide the baseline for targeted implementation scenarios designed to determine if statistically and physically meaningful load reductions can be achieved through BMP implementation alone.

Plutonium and americium in Lake Michigan sediments

International Nuclear Information System (INIS)

Edgington, D.N.; Alberts, J.J.; Wahlgren, M.A.; Karttunen, J.O.; Reeve, C.A.

1975-01-01

The vertical distributions of 239 , 240 Pu, 238 Pu, and 137 Cs have been measured in sediment cores taken from Lake Michigan. Sections from a limited number of cores have been analyzed for 241 Am. In addition, grab samples from ten locations in the southern basin of the lake have been analyzed for phase distribution of 239 , 240 Pu using a sequential extraction technique. The results indicate that the 239 , 240 Pu, 238 Pu, and 137 Cs from weapons testing, and the 241 Am formed in situ are concentrated in the sediments. A comparison of the total deposition of 239 , 240 Pu and 137 Cs indicates that 137 Cs may be valuable as a monitor for 239 , 240 Pu deposition in the sediments. Values of the 238 Pu/ 239 , 240 Pu ratio are in agreement with values reported in Lake Ontario sediments (and Lake Michigan plankton) and show little variation with depth. 241 Am data support the concept of in situ production with little preferential mobility after formation. Studies of sedimentary phase distributions show that 239 , 240 Pu is associated with hydrous oxide phases which are chemically stable under the prevailing conditions in lake sediments. Since Lake Michigan sediments remain aerobic, relatively little 239 , 240 Pu is available for chemical mobilization from the hydrous oxide or organic phases present in the sediments

A mass balance mercury budget for a mine-dominated lake: Clear Lake, California

Science.gov (United States)

Suchanek, T.H.; Cooke, J.; Keller, K.; Jorgensen, S.; Richerson, P.J.; Eagles-Smith, Collin A.; Harner, E.J.; Adam, D.P.

2009-01-01

The Sulphur Bank Mercury Mine (SBMM), active intermittently from 1873–1957 and now a USEPA Superfund site, was previously estimated to have contributed at least 100 metric tons (105 kg) of mercury (Hg) into the Clear Lake aquatic ecosystem. We have confirmed this minimum estimate. To better quantify the contribution of the mine in relation to other sources of Hg loading into Clear Lake and provide data that might help reduce that loading, we analyzed Inputs and Outputs of Hg to Clear Lake and Storage of Hg in lakebed sediments using a mass balance approach. We evaluated Inputs from (1) wet and dry atmospheric deposition from both global/regional and local sources, (2) watershed tributaries, (3) groundwater inflows, (4) lakebed springs and (5) the mine. Outputs were quantified from (1) efflux (volatilization) of Hg from the lake surface to the atmosphere, (2) municipal and agricultural water diversions, (3) losses from out-flowing drainage of Cache Creek that feeds into the California Central Valley and (4) biotic Hg removal by humans and wildlife. Storage estimates include (1) sediment burial from historic and prehistoric periods (over the past 150–3,000 years) from sediment cores to ca. 2.5m depth dated using dichloro diphenyl dichloroethane (DDD), 210Pb and 14C and (2) recent Hg deposition in surficial sediments. Surficial sediments collected in October 2003 (11 years after mine site remediation) indicate no reduction (but a possible increase) in sediment Hg concentrations over that time and suggest that remediation has not significantly reduced overall Hg loading to the lake. Currently, the mine is believed to contribute ca. 322–331 kg of Hg annually to Clear Lake, which represents ca. 86–99% of the total Hg loading to the lake. We estimate that natural sedimentation would cover the existing contaminated sediments within ca. 150–300 years.

Rise and fall of a small ice-dammed lake - Role of deglaciation processes and morphology

Science.gov (United States)

Nehyba, Slavomír; Hanáček, Martin; Engel, Zbyněk; Stachoň, Zdeněk

2017-10-01

A small ice-dammed lake, which developed along the margin of Nordenskiöldbreen on the northern coast of Adolfbukta, (central Spitsbergen, Svalbard) has been studied by a combination of facies analysis, ground penetrating radar, analysis of photos and satellite imagery, and by surface mapping by Unmanned Aerial Vehicle (drone). The lake existed between the years 1990-2012 and occupied two partial depressions in the bedrock, separated by a bedrock ridge for the dominant period of its history. Whereas the eastern depression was almost completely infilled due to direct fluvial input, the western depression revealed only thin sedimentary cover and was dotted from the eastern depression by an outflow of surficial waters. Gilbert delta deposits with typical tripartite zones of topset, foreset and bottomset were recognised in the eastern depression. Topset was comprised by deposits of a braided river. Foreset is formed by deposits of sediment gravity flows (turbidity currents and debris flows). Bottomset is represented by alternating suspension deposits and deposits of hyperpycnal underflows (low-density turbidity currents). The ruling factors of the evolution of the delta were glacier retreat, bedrock morphology, both affecting the relative lake level, and the rate of sediment delivery. Glacier retreat over stepped and inclined bedrock morphology led to delta prograding and downstepping. The recognised fluvio-deltaic terraces revealed four lake level falls followed by fluvial downcutting, erosion and redeposition of the older deltaic/lake deposits, the shifting of the lake's position towards the damming glacier and the transition of the sediment input in the same direction. The termination of the lake was a result of further glacier retreat and the opening of subglacial drainage.

Spatial characterization of acid rain stress in Canadian Shield Lakes

Science.gov (United States)

Tanis, Fred J.

1987-01-01

The acidification of lake waters from airborne pollution is of continental proportions both in North America and Europe. A major concern of the acid rain problem is the cumulative ecosystem damage to lakes and forest. The number of lakes affected in northeastern U.S. and on the Canadian Shield is though to be enormous. How seasonal changes in lake transparency are related to annual acidic load was examined. The relationship between variations in lake acidification and ecophysical units was also examined. The utility of Thematic Mapper based observations to measure seasonal changes in the optical transparency in acid lakes was investigated. The potential for this optical response is related to a number of local ecophysical factors with bedrock geology being, perhaps, the most important. Other factors include sulfate deposition, vegetative cover, and terrain drainage/relief. The area of southern Ontario contains a wide variety of geologies from the most acid rain sensitive granite quartzite types to the least sensitive limestone dolomite sediments. Annual sulfate deposition ranges from 1.0 to 4.0 grams/sq m.

The role of Lake Dongting in regulating the sediment budget of the Yangtze River

Directory of Open Access Journals (Sweden)

Shi-bao Dai

2005-01-01

Full Text Available Lake Dongting, the second largest freshwater lake in China and located in the middle reaches of the River Yangtze catchment, was formed at the beginning of the Holocene period by sea level rise and has varied in size with changes in local weather patterns. The sedimentation rate in Lake Dongting during the Holocene is about 50×106 m3 yr-1, or 80×106 t yr-1 (a sand bulk density of 1.6×103 kg m-3, given the sediment deposition rate as 10 mm yr-1 and the average lake size as 5000 km2. By comparing the sediment import and export, it is estimated that the sediment deposition rate of Lake Dongting was 110.6×106 t yr-1 from 1956 to 2003. Siltation and raised embankments reduced the size of the lake and its capacity to accommodate floods. The sediment delivery ratio (SDR of the middle and lower Yangtze is about 0.92 (total sediment output divided by total sediment input given that the total sediment supply into the middle and lower Yangtze is 455.1×106 t yr-1 and the total sediment discharge into the sea is 419×106 t yr-1. Therefore, if it were not for Lake Dongting, the sediment flux at Datong would be 73.6×106 t yr-1 (80×106 t yr-1×0.92 more, an increase of 27% during the Holocene and an increase of 26% to 101.75×106 t yr-1 from 1956 to 2003. Historically, Lake Dongting had a considerable influence in regulating the sediment budget of the Yangtze. However, afforestation and the construction of large dams, such as the Three Gorges Dam, reduced significantly the sediment deposition in Lake Dongting. In 2003, the completion of the Three Gorges Dam and the subsequent impoundment of water reduced the sediment input from the Yangtze and net deposition in Lake Dongting dropped to 25% and 18% of the mean values of the historic records (1956-2003. During the same period, the amount of sediment deposited in Lake Dongting was only 10% of the sediment discharge at Datong. The influence of the sediment deposited in Lake Dongting on the sediment flux to

BOTTOM DEPOSITS OF STRATIFIED, SEEPAGE, URBAN LAKE (ON EXAMPLE OF TYRSKO LAKE, POLAND AS A FACTOR POTENTIALLY SHAPING LAKE WATER QUALITY

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Renata Augustyniak

2017-09-01

The obtained results revealed, that bottom sediment of Tyrsko Lake can be classified as mixed, silica-organic type, with quite high content of iron (over 4% Fe in d.w.. The total phosphorus content was ca. 3.5 mg P g-1 d.w. on average. Phosphorus in bottom sediment was bound mainly with organic matter (NaOH-nrP fraction, which had over 50% share in TP. Easy mobile fractions (NH4-Cl-P and BD-P together included ca 5% to 7 % TP only. The obtained results show, that bottom sediment of Tyrsko Lake can bind phosphorus quite effectively. Calculated internal mineral phosphorus loading during summer stagnation period was 10.9 kg P and it was lower that the assessed annual external phosphorus load (22.6 kg P y-1. The assessed annual phosphorus loading from both sources still was lower than critical load according to Vollenweider criteria. But due to the fact that internal loading phenomenon is occurring in the lake it should be taken into consideration that the lake water quality can deteriorate gradually during the longer time perspective. These findings should be taken into consideration in the future if the potential protection and restoration procedures will be developed.

Allogenic sedimentary components of Bear Lake, Utah and Idaho

Science.gov (United States)

Rosenbaum, J.G.; Dean, W.E.; Reynolds, R.L.; Reheis, M.C.

2009-01-01

Bear Lake is a long-lived lake filling a tectonic depression between the Bear River Range to the west and the Bear River Plateau to the east, and straddling the border between Utah and Idaho. Mineralogy, elemental geochemistry, and magnetic properties provide information about variations in provenance of allogenic lithic material in last-glacial-age, quartz-rich sediment in Bear Lake. Grain-size data from the siliciclastic fraction of late-glacial to Holocene carbonate-rich sediments provide information about variations in lake level. For the quartz-rich lower unit, which was deposited while the Bear River fl owed into and out of the lake, four source areas are recognized on the basis of modern fluvial samples with contrasting properties that reflect differences in bedrock geology and in magnetite content from dust. One of these areas is underlain by hematite-rich Uinta Mountain Group rocks in the headwaters of the Bear River. Although Uinta Mountain Group rocks make up a small fraction of the catchment, hematite-rich material from this area is an important component of the lower unit. This material is interpreted to be glacial fl our. Variations in the input of glacial flour are interpreted as having caused quasi-cyclical variations in mineralogical and elemental concentrations, and in magnetic properties within the lower unit. The carbonate-rich younger unit was deposited under conditions similar to those of the modern lake, with the Bear River largely bypassing the lake. For two cores taken in more than 30 m of water, median grain sizes in this unit range from ???6 ??m to more than 30 ??m, with the coarsest grain sizes associated with beach or shallow-water deposits. Similar grain-size variations are observed as a function of water depth in the modern lake and provide the basis for interpreting the core grain-size data in terms of lake level. Copyright ?? 2009 The Geological Society of America.

Lake Turkana National Parks Kenya.

OpenAIRE

2005-01-01

Lake Turkana is the largest, most northerly and most saline of Africa's Rift Valley lakes and an outstanding laboratory for the study of plant and animal communities. The three National Parks are a stopover for migrant waterfowl and are major breeding grounds for the Nile crocodile and hippopotamus. The Koobi Fora deposits are rich in pre-human, mammalian, molluscan and other fossil remains and have contributed more to the understanding of Quaternary palaeoenvironments than any other site on ...

Mirror Lake: Past, present and future: Chapter 6

Science.gov (United States)

Likens, Gene E.; LaBaugh, James W.; Winter, Thomas C.; Likens, Gene E.

2009-01-01

This chapter discusses the hydrological and biogeochemical characteristics of Mirror Lake and the changes that resulted from air-land-water interactions and human activities. Since the formation of Mirror Lake, both the watershed and the lake have undergone many changes, such as vegetation development and basin filling. These changes are ongoing, and Mirror Lake is continuing along an aging pathway and ultimately, it will fill with sediment and no longer be a lake. The chapter also identifies major factors that affected the hydrology and biogeochemistry of Mirror Lake: acid rain, atmospheric deposition of lead and other heavy metals, increased human settlement around the lake, the construction of an interstate highway through the watershed of the Northeast Tributary, the construction of an access road through the West and Northeast watersheds to the lake, and climate change. The chapter also offers future recommendations for management and protection of Mirror Lake.

Lake-0: A model for the simulation of nuclides transfer in lake scenarios

International Nuclear Information System (INIS)

Garcia-Olivares, A.; Aguero, A.; Pinedo, P.

1994-01-01

This report presents documentation and a user's manual for the program LAKE-0, a mathematical model of nuclides transfer in lake scenarios. Mathematical equations and physical principles used to develop the code are presented in section 2. The program use is presented in section 3 including input data sets and output data. Section 4 presents two example problems, and some results. The complete program listing including comments is presented in Appendix A. Nuclides are assumed to enter the lake via atmospheric deposition and carried by the water runoff and the dragged sediments from the adjacent catchment. The dynamics of the nuclides inside the lake is based in the model proposed by Codell (11) as modified in (5). The removal of concentration from the lake water is due to outflow from the lake and to the transfer of activity to the bottom sediments. The model has been applied to the Esthwaite Water (54 degree 21 minute N, 03 degree 00 minute W at 65 m. asl.) in the frame of the VAMP Aquatic Working Group (8) and to Devoke Water (54 degree 21 minute 5'N, 03 degree, 18 minute W at 230 m. asl.)

LAKE-0: a model for the simulation of nuclides transfer in lake scenarios

International Nuclear Information System (INIS)

Garcia-Olivares, A.; Aguero, A.; Pinedo, P.

1994-01-01

This report presents documentation and a user's manual for the program LAKE-0, a mathematical model of nuclides transfer in lake scenarios. Mathematical equations and physical principles used to develop the code are presented in section 2. The program use is presented in section 3 including input data sets and output data. Section 4 presents two example problems, and some results. The complete program listing including comments is presented in Appendix A. Nuclides are assumed to center the lake via atmospheric deposition and carried by the water runoff and the dragged sediments from the adjacent catchment. The dynamics of the nuclides inside the lake is based in the model proposed by Codell (11) as modified in (5). The removal of concentration from the lake water is due to out flow from the lake and to the transfer of activity to the button sediments. The model has been applied to the Esthwaite Water (54 degree celsius 2 l'N, 03 degree celsius 00'W at 65 m. asi.) in the frame of the VAMP Aquatic Working Group (8) and to Devoke Water (5 21.5'N, 03H8'W at 230 m. asi.). (Author). 13 refs

Carbonaceous particle record in lake sediments from the Arctic and other remote areas of the northern hemisphere

International Nuclear Information System (INIS)

Rose, N.L.

1995-01-01

Lake sediments, including spheroidal carbonaceous particles produced by high temperature combustion of fossil fuels, contain a record of lake, catchment and atmospheric deposition history. The spatial and temporal distributions of these particles can indicate the extent to which a single lake or a region has been contaminated by airborne pollutants (e.g. sulfur, polycyclic aromatic hydrocarbons (PAHs)) derived from fossil fuels. The carbonaceous particle records of two Arctic lakes, Shuonijavr and Stepanovichjarvi, close to local pollution sources on the Kola Peninsula, Russia, are compared with the record of a remote lake on Svalbard and with mid-latitude remote mountain lakes in Europe and Asia. Although, Shuonijavr and Stepanovichjarvi show relatively high levels of contamination, as expected, the presence of carbonaceous particles at all of the remote sites studied suggests there is a hemispherical background of these particles. Other less remote mountain lakes in Europe have been found to contain significant concentrations of particles and these may represent regional deposition patterns. Carbonaceous particle analysis may provide an effective assessment of whether a lake site is receiving local, regional or background levels of deposition

Sources and Deposition of Polycyclic Aromatic Hydrocarbons to Western U.S. National Parks

Science.gov (United States)

USENKO, SASCHA; MASSEY SIMONICH, STACI L.; HAGEMAN, KIMBERLY J.; SCHRLAU, JILL E.; GEISER, LINDA; CAMPBELL, DON H.; APPLEBY, PETER G.; LANDERS, DIXON H.

2010-01-01

Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) in order to determine their current and historical deposition, as well as to identify their potential sources. Seasonal snowpack was measured to determine the current wintertime atmospheric PAH deposition; lichens were measured to determine the long-term, year around deposition; and the temporal PAH deposition trends were reconstructed using lake sediment cores dated using 210Pb and 137Cs. The fourteen remote lake catchments ranged from low-latitude catchments (36.6° N) at high elevation (2900 masl) in Sequoia National Park, CA to high-latitude catchments (68.4° N) at low elevation (427 masl) in the Alaskan Arctic. Over 75% of the catchments demonstrated statistically significant temporal trends in ΣPAH sediment flux, depending on catchment proximity to source regions and topographic barriers. The ΣPAH concentrations and fluxes in seasonal snowpack, lichens, and surficial sediment were 3.6 to 60,000 times greater in the Snyder Lake catchment of Glacier National Park than the other 13 lake catchments. The PAH ratios measured in snow, lichen, and sediment were used to identify a local aluminum smelter as a major source of PAHs to the Snyder Lake catchment. These results suggest that topographic barriers influence the atmospheric transport and deposition of PAHs in high-elevation ecosystems and that PAH sources to these national park ecosystems range from local point sources to diffuse regional and global sources. PMID:20465303

Multidisciplinary characterisation of sedimentary processes in a recent maar lake (Lake Pavin, French Massif Central and implication for natural hazards

Directory of Open Access Journals (Sweden)

E. Chapron

2010-09-01

Full Text Available Sedimentation processes occurring in the most recent maar lake of the French Massif Central (Lake Pavin are documented for the first time based on high resolution seismic reflection and multibeam bathymetric surveys and by piston coring and radiocarbon dating on a sediment depocentre developed on a narrow sub aquatic plateau. This new data set confirms the mid Holocene age of maar lake Pavin formation at 6970±60 yrs cal BP and highlights a wide range of gravity reworking phenomena affecting the basin. In particular, a slump deposit dated between AD 580–640 remoulded both mid-Holocene lacustrine sediments, terrestrial plant debris and some volcanic material from the northern crater inner walls. Between AD 1200 and AD 1300, a large slide scar mapped at 50 m depth also affected the southern edge of the sub aquatic plateau, suggesting that these gas-rich biogenic sediments (laminated diatomite are poorly stable. Although several triggering mechanisms can be proposed for these prehistoric sub-aquatic mass wasting deposits in Lake Pavin, we argue that such large remobilisation of gas-rich sediments may affect the gas stability in deep waters of meromictic maar lakes. This study highlights the need to further document mass wasting processes in maar lakes and their impacts on the generation of waves, favouring the development of dangerous (and potentially deadly limnic eruptions.

Transfer of Chernobyl-derived 137Cs into fishes in some Finnish lakes

International Nuclear Information System (INIS)

Saxen, R.; Koskelainen, U.; Alatalo, M.

2000-09-01

This report summarises STUK's work for the hydrological modelling (WG 4) in RODOS C, a project co-ordinated by the EU, in 1996-1999. The role of STUK in the project was to provide a data set on the radio-caesium contents in different types of fish and lakes in northern European environmental conditions for the development of a dynamic regional model describing radio-caesium transfer into fish. The co-operating institute, Technical Research Centre of Finland (VTT), was responsible for the modelling work in this project. Besides the analysed data on 137 Cs in the various fish species in the lakes, background information was produced on lakes and their drainage areas that might affect radio-caesium transfer into fish, which was needed for the development of fish, lake and drainage basin models. The role of STUK included also providing another, independent data set for the validation of the model. The proposals and needs of the co-operating institute, VTT, were taken into account. One of the factors strongly affecting the transfer of 137 Cs into fish is the nutrition level of the lake. The average transfer of 137 Cs in predators at the time of maximum activity concentrations in oligotrophic lakes was found to be up to 0.10 m 2 /kg, implying that approximately 10% of the amount of 137 Cs deposited on one square metre is transferred into 1 kg of fish. The corresponding transfer in eutrophic lakes was clearly lower,.i.e. 3- 4%, at the time of maximum concentrations, which usually occurred 1- 3 years after the deposition, depending on the fish species. These time-dependent transfer coefficients can be regarded as a kind of a lake-specific model. If deposition to the lake is known, the activity concentrations in fish can be estimated within specific uncertainty limits, by multiplying the deposition value by the transfer coefficient at a certain time point. Temporal changes in annual averages of transfer coefficients with variation for a certain set of lakes and for three

Management of polluted deposit in lake and river

Energy Technology Data Exchange (ETDEWEB)

Lee, Chang Hee; Kim, Eun Jung [Korea Environment Institute, Seoul (Korea)

1998-12-01

In this study, the perception and problem of polluted deposit in Korea, which does not have a clear concept of it, were analyzed and the need of a comprehensive polluted deposit management, including the present condition of pollution, assessment, pollution prevention, and disposal of polluted deposit, was presented. Based on the analysis on foreign management system, the framework of polluted deposit management in Korea was provided. 84 refs., 11 figs., 40 tabs.

Adirondack lakes survey: An interpretive analysis of fish communities and water chemistry, 1984--1987

Energy Technology Data Exchange (ETDEWEB)

Baker, J.P. (Baker (Joan P.), Raleigh, NC (USA)); Gherini, S.A.; Munson, R.K. (Tetra Tech, Inc., Pasadena, CA (USA)); Christensen, S.W. (Oak Ridge National Lab., TN (USA)); Driscoll, C.T. (Syracuse Univ., NY (USA)); Gallagher, J. (Adirondack Lakes Survey Corp., Ray Brook, NY (USA)); Newton, R.M. (Smith Coll., Northampton, MA (USA)); Reckhow, K.H. (Duke Univ., Durham, NC (USA)); Schofield, C.L. (Co

1990-01-01

The Adirondack Lakes Survey Corporation (ALSC) was formed as a cooperative effort of the New York State Department of Environmental Conservation and the Empire State Electric Energy Research Corporation to better characterize the chemical and biological status of Adirondack lakes. Between 1984 and 1987, the ALSC surveyed 1469 lakes within the Adirondack ecological zone. As a follow-up to the survey, the ALSC sponsored a series of interpretive analyses of the ALSC data base. The primary objectives of these analyses were as follows: Evaluate the influence of mineral acids (from acidic deposition) and nonmineral acids (natural organic acids) on lake pH levels; classify Adirondack lakes according to lake and watershed features expected to influence their responsiveness to changes in acidic deposition; evaluate the sensitivity of Adirondack lakes to changes in environmental conditions, such as changes in mineral acids or dissolved organic carbon concentrations; identify lake characteristics important in explaining the observed present-day status of fish communities in Adirondack lakes, in particular the relative importance of lake acidity; evaluate changes that have occurred over time in Adirondack fish communities and probable causes for these trends by using the available historical data on fish communities in the Adirondacks and the ALSC data base; and determine the degree to which the existing fish resource might be at risk from continued acidic deposition, or might recover if acidity levels were reduced. The basic approach examined relationships observed in the ALSC data base among watershed characteristics, lake chemistry, and fish status. Individual reports are processed separately for the data bases.

Effects of historical and modern mining on mercury deposition in southeastern Peru.

Science.gov (United States)

Beal, Samuel A; Jackson, Brian P; Kelly, Meredith A; Stroup, Justin S; Landis, Joshua D

2013-11-19

Both modern anthropogenic emissions of mercury (Hg), primarily from artisanal and small-scale gold mining (ASGM), and preindustrial anthropogenic emissions from mining are thought to have a large impact on present-day atmospheric Hg deposition. We study the spatial distribution of Hg and its depositional history over the past ∼400 years in sediment cores from lakes located regionally proximal (∼90-150 km) to the largest ASGM in Peru and distal (>400 km) to major preindustrial mining centers. Total Hg concentrations in surface sediments from fourteen lakes are typical of remote regions (10-115 ng g(-1)). Hg fluxes in cores from four lakes demonstrate preindustrial Hg deposition in southeastern Peru was spatially variable and at least an order of magnitude lower than previously reported fluxes in lakes located closer to mining centers. Average modern (A.D. 2000-2011) Hg fluxes in these cores are 3.4-6.9 μg m(-2) a(-1), compared to average preindustrial (A.D. 1800-1850) fluxes of 0.8-2.5 μg m(-2) a(-1). Modern Hg fluxes determined from the four lakes are on average 3.3 (±1.5) times greater than their preindustrial fluxes, similar to those determined in other remote lakes around the world. This agreement suggests that Hg emissions from ASGM are likely not significantly deposited in nearby down-wind regions.

Mercury contamination in the Laurentian Great Lakes region: Introduction and overview

International Nuclear Information System (INIS)

Wiener, James G.; Evers, David C.; Gay, David A.; Morrison, Heather A.; Williams, Kathryn A.

2012-01-01

The Laurentian Great Lakes region of North America contains substantial aquatic resources and mercury-contaminated landscapes, fish, and wildlife. This special issue emanated from a bi-national synthesis of data from monitoring programs and case studies of mercury in the region, here defined as including the Great Lakes, the eight U.S. states bordering the Great Lakes, the province of Ontario, and Lake Champlain. We provide a retrospective overview of the regional mercury problem and summarize new findings from the synthesis papers and case studies that follow. Papers in this issue examine the chronology of mercury accumulation in lakes, the importance of wet and dry atmospheric deposition and evasion to regional mercury budgets, the influence of land–water linkages on mercury contamination of surface waters, the bioaccumulation of methylmercury in aquatic foods webs; and ecological and health risks associated with methylmercury in a regionally important prey fish. - Highlights: ► We describe a bi-national synthesis of Hg data from the Great Lakes region. ► Emission controls have reduced Hg inputs to inland lakes about 20% since the 1980s. ► Wet and dry deposition and evasion are regionally important atmospheric Hg fluxes. ► Land use affects Hg inputs to surface waters and bioaccumulation of methylmercury. ► In some waters, Hg levels in yellow perch pose risks to fish, wildlife, and humans. - A synthesis of Hg data from the Great Lakes region reveals the chronology of contamination; the importance of wet and dry deposition and evasion to Hg budgets; the influence of land–water linkages; bioaccumulation in aquatic foods webs; and risks associated with Hg in an important prey fish.

Preliminary Report on Unique Laminated Holocene Sediments from the Qarun Lake in Egypt

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Marks Leszek

2016-06-01

Full Text Available The Lake Qarun (Faiyum Oasis, northern Egypt is a relic of the much larger Holocene lake. Past lake levels and extensions were reconstructed, based on setting of archaeological sites scattered along northern paleoshores of the ancient lake. However, geoarcheological works did not yield enough data to establish continuous environmental history of the lake. A deep drilling FA-1 on the southeastern shore of the lake, performed in 2014, supplied with a core, 26 m long that is the one of the longest lake sediment cores in northeastern Africa. The basal section of the core consisted of thin-laminated diatom marly deposits, underlain at the Late Pleistocene/Holocene boundary by coarse-grained sands. The sediment lamine were quite well developed, especially in the lower part of the core. Preliminary results indicated annually deposited sediment sequence with seasonality signals provided by microlamine of diatoms, calcite, organic matter and clastic material. Early Holocene varved sediments from the Faiyum Oasis supplied with exceptional paleoenvironmental data for northeastern Africa, which enriched a record from previous logs drilled at the southwestern margin of the Qarun Lake.

Ground-water availability in the eastern part of the Lake Ontario Basin, New York

Science.gov (United States)

Miller, Todd S.

1986-01-01

A set of three maps show surficial geology, significant unconsolidated aquifers and well yield, and selected well locations for the Lake Ontario basin, New York. In the low areas , glaciers and wave action of former high-level lakes deposited permeable sand and gravel to form aquifers that yield more than 10 gal/min of water to wells. Small quantities of water (less than 2 gal/min) can be pumped from dug wells that top till and fine lake-sediment deposits. (USGS)

Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

Science.gov (United States)

Smoot, J.P.

1991-01-01

The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the

Radioactivity monitoring in Irish upland lakes 1988 - 1992

International Nuclear Information System (INIS)

O'Sullivan, M.; McGarry, A.T.; Lyons, S.; McEnri, C.; Cunningham, J.D.

1995-04-01

In 1988, monitoring of radioactivity in upland lakes was initiated in areas of Ireland which had been subjected to highest deposition following the Chernobyl accident. The monitoring programme was continued in 1989 and extended in 1990 to include 25 lakes in 13 counties. This survey provided a comprehensive national picture of the distribution of Chernobyl contamination in Irish freshwater lakes. In 1991 and 1992, the monitoring programme concentrated on those lakes which had shown highest levels in the 1990 survey. This report details the results of the freshwater lake monitoring programme for the years 1988 - 1992. As assessment of the radiation doses to those consumers who include relatively large amounts of freshwater fish in their diet is also made

Sedimentary record of polycyclic aromatic hydrocarbons in a sediment core from a maar lake, Northeast China: evidence in historical atmospheric deposition.

Science.gov (United States)

Guan, Yu-Feng; Sun, Jian-Lin; Ni, Hong-Gang; Guo, Jian-Yang

2012-09-01

A maar lake is an excellent ecosystem to study the atmospheric deposition of pollutants, as its contaminants are primarily by atmospheric deposition. In this study, a sediment core from Sihailongwan Maar Lake, Northeast China, was collected and the historical atmospherically deposited polycyclic aromatic hydrocarbons (PAHs) were analyzed. The concentrations of TPAHs (the sum of the US EPA proposed 16 priority PAHs, excluding naphthalene and pyrene) ranged from 473.9 to 2289 ng g(-1) with a slow increasing stage in the deeper sediments and a sharp increasing stage in the upper sediments. The input rate of TPAHs, especially that of PAH(9) (the sum of fluoranthene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(ah)anthrathene, and benzo(ghi)perylene), correlated well to the Chinese historical socioeconomic data. This indicates that sediment PAHs were mainly derived from human activities and PAH(9) can be regarded as a better indicator of the local socioeconomic development. Source identification suggested that PAHs were originated primarily from mixed sources (e.g., coal and biomass burning and petroleum combustion), except for perylene which was mostly of diagenetic origin. In addition, the down-core PAHs profile clearly illustrated that PAHs sources in Northeast China experienced a transformation from low- and moderate temperature to high-temperature combustion processes, especially after the late 1980s. Additionally, an ecological risk assessment using two redefined biological thresholds (TEQ(ERL) and TEQ(ERM)) indicated that most of the PAHs measured in the present sediment core would not cause an immediate toxic effect; only FLU and PHEN are a potential source of concern for biological impairment.

Geology and geomorphology of Bear Lake Valley and upper Bear River, Utah and Idaho

Science.gov (United States)

Reheis, M.C.; Laabs, B.J.C.; Kaufman, D.S.

2009-01-01

Bear Lake, on the Idaho-Utah border, lies in a fault-bounded valley through which the Bear River flows en route to the Great Salt Lake. Surficial deposits in the Bear Lake drainage basin provide a geologic context for interpretation of cores from Bear Lake deposits. In addition to groundwater discharge, Bear Lake received water and sediment from its own small drainage basin and sometimes from the Bear River and its glaciated headwaters. The lake basin interacts with the river in complex ways that are modulated by climatically induced lake-level changes, by the distribution of active Quaternary faults, and by the migration of the river across its fluvial fan north of the present lake. The upper Bear River flows northward for ???150 km from its headwaters in the northwestern Uinta Mountains, generally following the strike of regional Laramide and late Cenozoic structures. These structures likely also control the flow paths of groundwater that feeds Bear Lake, and groundwater-fed streams are the largest source of water when the lake is isolated from the Bear River. The present configuration of the Bear River with respect to Bear Lake Valley may not have been established until the late Pliocene. The absence of Uinta Range-derived quartzites in fluvial gravel on the crest of the Bear Lake Plateau east of Bear Lake suggests that the present headwaters were not part of the drainage basin in the late Tertiary. Newly mapped glacial deposits in the Bear River Range west of Bear Lake indicate several advances of valley glaciers that were probably coeval with glaciations in the Uinta Mountains. Much of the meltwater from these glaciers may have reached Bear Lake via groundwater pathways through infiltration in the karst terrain of the Bear River Range. At times during the Pleistocene, the Bear River flowed into Bear Lake and water level rose to the valley threshold at Nounan narrows. This threshold has been modified by aggradation, downcutting, and tectonics. Maximum lake

Subaquatic moraine amphitheatre in Lake Thun

OpenAIRE

Fabbri, Stefano Claudio; Weiss, Benedikt J.; Hübscher, Christian; Horstmeyer, Heinrich; Schmelzbach, Cédric; Büchi, Marius; Herwegh, Marco; Schlunegger, Fritz; Anselmetti, Flavio

2016-01-01

The combination of a recently acquired high-resolution multibeam bathymetric dataset with 2D multichannel reflection seismic data from perialpine Lake Thun reveals new insights into the evolution of the lake basin upon deglaciation and a so far unknown subaquatic moraine. These new data improve our socomprehension of the landforms associated with the ice-contact zone, the facies architecture of the sub- to proglacial units, the related depositional processes, and thus the retreat mechanisms o...

Siderite formation in mining lakes. Sanitation strategy for the Spreetal Nordost lake; Sideritbildung in Tagebaurestseen. Moegliche Sanierungsstrategie des Restlochs Spreetal Nordost

Energy Technology Data Exchange (ETDEWEB)

Unger, Y.; Wolkersdorfer, C. [Technische Univ. Bergakademie Freiberg (Germany)

2006-07-01

The treatment of acid mine lakes is a worldwide problem. In this study, it will be investigated since the sludge from acid mine drainage (AMD) treatment plants combined with carbon dioxide injections may improve the water quality in such pit lakes. Simultaneously, the emissions of carbon dioxide into the atmosphere may be reduced. The CO{sub 2} will be sequestered in the lake sediments as siderite (FeCO{sub 3}). The acid mine lake Spreetal-Nordost (Lusatia/Germany) was chosen as a test site. Since 1998 iron hydroxide sludge from an AMD treatment plant was deposited into the lake. In preliminary tests the feasibility of this treatment scheme will be investigated. (orig.)

Using ground-penetrating radar and sidescan sonar to compare lake bottom geology in New England

Science.gov (United States)

Nesbitt, I. M.; Campbell, S. W.; Arcone, S. A.; Smith, S. M.

2017-12-01

Post-Laurentide Ice Sheet erosion and re-deposition has had a significant influence on the geomorphology of New England. Anthropogenic activities such as forestry, farming, and construction of infrastructure such as dams and associated lake reservoirs, has further contributed to near surface changes. Unfortunately, these surface dynamics are difficult to constrain, both in space and time. One analog that can be used to estimate erosion and deposition, lake basin sedimentation, is typically derived from lake bottom sediment core samples. Reliance on core records assumes that derived sedimentation rates are representative of the broader watershed, despite being only a single point measurement. Geophysical surveys suggest that this assumption can be highly erroneous and unrepresentative of an entire lake basin. Herein, we conducted ground-penetrating radar (GPR) and side-scan sonar (SSS) surveys of multiple lakes in Maine, New Hampshire, and Vermont which are representative of different basin types to estimate sedimentation rates since Laurentide retreat. Subsequent age constraints from cores on multiple GPR-imaged horizons could be used to refine estimates of sedimentation rate change caused by evolving physical, biological, and chemical processes that control erosion, transport, and re-deposition. This presentation will provide a summary of GPR and SSS data collection methods, assumptions and limitations, structural and surficial interpretations, and key findings from multiple lake basins in New England. Results show that GPR and SSS are efficient, cost effective, and relatively accurate tools for helping to constrain lake erosion and deposition processes.

Evaluating the behavior of polychlorinated biphenyl compounds in Lake Superior using a dynamic multimedia model

Science.gov (United States)

Khan, T.; Perlinger, J. A.; Urban, N. R.

2017-12-01

Certain toxic, persistent, bioaccumulative, and semivolatile compounds known as atmosphere-surface exchangeable pollutants or ASEPs are emitted into the environment by primary sources, are transported, deposited to water surfaces, and can be later re-emitted causing the water to act as a secondary source. Polychlorinated biphenyl (PCB) compounds, a class of ASEPs, are of major concern in the Laurentian Great Lakes because of their historical use primarily as additives to oils and industrial fluids, and discharge from industrial sources. Following the ban on production in the U.S. in 1979, atmospheric concentrations of PCBs in the Lake Superior region decreased rapidly. Subsequently, PCB concentrations in the lake surface water also reached near equilibrium as the atmospheric levels of PCBs declined. However, previous studies on long-term PCB levels and trends in lake trout and walleye suggested that the initial rate of decline of PCB concentrations in fish has leveled off in Lake Superior. In this study, a dynamic multimedia flux model was developed with the objective to investigate the observed levelling off of PCB concentrations in Lake Superior fish. The model structure consists of two water layers (the epilimnion and the hypolimnion), and the surface mixed sediment layer, while atmospheric deposition is the primary external pathway of PCB inputs to the lake. The model was applied for different PCB congeners having a range of hydrophobicity and volatility. Using this model, we compare the long-term trends in predicted PCB concentrations in different environmental media with relevant available measurements for Lake Superior. We examine the seasonal depositional and exchange patterns, the relative importance of different process terms, and provide the most probable source of the current observed PCB levels in Lake Superior fish. In addition, we evaluate the role of current atmospheric PCB levels in sustaining the observed fish concentrations and appraise the need

Does historical wildfire activity alter metal fluxes to northern lakes?

Science.gov (United States)

Pelletier, N.; Chetelat, J.; Vermaire, J. C.; Palmer, M.; Black, J.; Pellisey, J.; Tracz, B.; van der Wielen, S.

2017-12-01

Current drought conditions in northwestern Canada are conducive to more frequent and severe wildfires that may mobilize mercury and other metals accumulated in soil and biomass. There is evidence that wildfires can remobilize and transport mercury within and outside catchments by atmospheric volatilization, particulate emissions and catchment soil erosion. However, the effect of fires on mercury fluxes to nearby lake sediments remains unclear. In this study, we use a combination of 10 dated lake sediment cores and four nearby ombrotrophic peatland cores to investigate the effects of wildfires on mercury fluxes to lake sediments. Lakes varying in catchment size and distance from recent fire events were sampled. Mercury concentrations in the environmental archives were measured, and macroscopic charcoal particles (>100 um) were counted at high resolution in the sediments to observe the co-variation of the local fire history and mercury fluxes. Mercury flux recorded in ombrotrophic peat cores provided an estimate of the historical atmospheric mercury flux from local and regional atmospheric deposition. The mercury flux recorded in lake sediments corresponds to the sum of direct atmospheric deposition and catchment transport. In combination, these archives will allow for the partitioning of mercury loading attributable to catchment transport from direct atmospheric deposition. After correcting the fluxes for particle focusing and terragenic elements input, flux from different lakes will be compared based on their catchment size and their temporal and spatial proximity known fire events. Altogether, our preliminary results using these paleolimnological methods will provide new insights on mercury transport processes that are predicted to become more important under a changing climate.

Hydrological and solute budgets of Lake Qinghai, the largest lake on the Tibetan Plateau

Energy Technology Data Exchange (ETDEWEB)

Jin, Zhangdong [Chinese Academy of Sciences (CAS), Beijing (China); National Cheng Kung Univ., Tainan City (Taiwan); You, Chen-Feng [National Cheng Kung Univ., Tainan City (Taiwan); Wang, Yi [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shi, Yuewei [Bureau of Hydrology and Water Resources of Qinghai Province, Xining (China)

2009-12-04

Water level and chemistry of Lake Qinghai are sensitive to climate changes and are important for paleoclimatic implications. An accurate understanding of hydrological and chemical budgets is crucial for quantifying geochemical proxies and carbon cycle. Published results of water budget are firstly reviewed in this paper. Chemical budget and residence time of major dissolved constituents in the lake are estimated using reliable water budget and newly obtained data for seasonal water chemistry. The results indicate that carbonate weathering is the most important riverine process, resulting in dominance of Ca ²⁺ and DIC for river waters and groundwater. Groundwater contribution to major dissolved constituents is relatively small (4.2 ± 0.5%). Wet atmospheric deposition contributes annually 7.4–44.0% soluble flux to the lake, resulting from eolian dust throughout the seasons. Estimates of chemical budget further suggest that (1) the Buha-type water dominates the chemical components of the lake water, (2) Na⁺, Cl^-, Mg ²⁺ , and K⁺ in lake water are enriched owing to their conservative behaviors, and (3) precipitation of authigenic carbonates (low-Mg calcite, aragonite, and dolomite) transits quickly dissolved Ca ²⁺ into the bottom sediments of the lake, resulting in very low Ca ²⁺ in the lake water. Therefore, authigenic carbonates in the sediments hold potential information on the relative contribution of different solute inputs to the lake and the lake chemistry in the past.

Future recovery of acidified lakes in southern Norway predicted by the MAGIC model

Directory of Open Access Journals (Sweden)

R. F. Wright

2003-01-01

Full Text Available The acidification model MAGIC was used to predict recovery of small lakes in southernmost Norway to future reduction of acid deposition. A set of 60 small headwater lakes was sampled annually from either 1986 (35 lakes or 1995 (25 lakes. Future acid deposition was assumed to follow implementation of current agreed legislation, including the Gothenburg protocol. Three scenarios of future N retention were used. Calibration of the sites to the observed time trends (1990–1999 as well as to one point in time considerably increased the robustness of the predictions. The modelled decline in SO4* concentrations in the lakes over the period 1986–2001 matched the observed decline closely. This strongly suggests that soil processes such as SO4 adsorption/desorption and S reduction/oxidation do not delay the response of runoff by more than a few years. The slope of time trends in ANC over the period of observations was less steep than that observed, perhaps because the entire soil column does not interact actively with the soilwater that emerges as runoff. The lakes showed widely differing time trends in NO3 concentrations over the period 1986–2000. The observed trends were not simulated by any of the three N scenarios. A model based on the C/N ratio in soil was insufficient to account for N retention and leaching at these sites. The large differences in modelled NO3, however, produced only minor differences in ANC between the three scenarios. In the year 2050, the difference was only about 5 μeq l-1. Future climate change entailing warming and increased precipitation could also increase NO3 loss to surface waters. SO4* concentrations in the lakes were predicted to decrease in parallel with the future decreases in S deposition. Fully 80% of the expected decline to year 2025, however, had already occurred by the year 2000. Similarly, ANC concentrations were predicted to increase in the future, but again about 67% of the expected change has already

Transfer of Chernobyl-derived {sup 137}Cs into fishes in some Finnish lakes

Energy Technology Data Exchange (ETDEWEB)

Saxen, R.; Koskelainen, U.; Alatalo, M

2000-09-01

This report summarises STUK's work for the hydrological modelling (WG 4) in RODOS C, a project co-ordinated by the EU, in 1996-1999. The role of STUK in the project was to provide a data set on the radio-caesium contents in different types of fish and lakes in northern European environmental conditions for the development of a dynamic regional model describing radio-caesium transfer into fish. The co-operating institute, Technical Research Centre of Finland (VTT), was responsible for the modelling work in this project. Besides the analysed data on {sup 137}Cs in the various fish species in the lakes, background information was produced on lakes and their drainage areas that might affect radio-caesium transfer into fish, which was needed for the development of fish, lake and drainage basin models. The role of STUK included also providing another, independent data set for the validation of the model. The proposals and needs of the co-operating institute, VTT, were taken into account. One of the factors strongly affecting the transfer of {sup 137}Cs into fish is the nutrition level of the lake. The average transfer of {sup 137}Cs in predators at the time of maximum activity concentrations in oligotrophic lakes was found to be up to 0.10 m{sup 2}/kg, implying that approximately 10% of the amount of {sup 137}Cs deposited on one square metre is transferred into 1 kg of fish. The corresponding transfer in eutrophic lakes was clearly lower,.i.e. 3- 4%, at the time of maximum concentrations, which usually occurred 1- 3 years after the deposition, depending on the fish species. These time-dependent transfer coefficients can be regarded as a kind of a lake-specific model. If deposition to the lake is known, the activity concentrations in fish can be estimated within specific uncertainty limits, by multiplying the deposition value by the transfer coefficient at a certain time point. Temporal changes in annual averages of transfer coefficients with variation for a certain

Tsunami deposits

Energy Technology Data Exchange (ETDEWEB)

NONE

2013-08-15

The NSC (the Nuclear Safety Commission of Japan) demand to survey on tsunami deposits by use of various technical methods (Dec. 2011), because tsunami deposits have useful information on tsunami activity, tsunami source etc. However, there are no guidelines on tsunami deposit survey in JAPAN. In order to prepare the guideline of tsunami deposits survey and evaluation and to develop the method of tsunami source estimation on the basis of tsunami deposits, JNES carried out the following issues; (1) organizing information of paleoseismological record and tsunami deposit by literature research, (2) field survey on tsunami deposit, and (3) designing the analysis code of sediment transport due to tsunami. As to (1), we organize the information gained about tsunami deposits in the database. As to (2), we consolidate methods for surveying and identifying tsunami deposits in the lake based on results of the field survey in Fukui Pref., carried out by JNES. In addition, as to (3), we design the experimental instrument for hydraulic experiment on sediment transport and sedimentation due to tsunamis. These results are reflected in the guideline on the tsunami deposits survey and evaluation. (author)

Tsunami deposits

International Nuclear Information System (INIS)

2013-01-01

The NSC (the Nuclear Safety Commission of Japan) demand to survey on tsunami deposits by use of various technical methods (Dec. 2011), because tsunami deposits have useful information on tsunami activity, tsunami source etc. However, there are no guidelines on tsunami deposit survey in JAPAN. In order to prepare the guideline of tsunami deposits survey and evaluation and to develop the method of tsunami source estimation on the basis of tsunami deposits, JNES carried out the following issues; (1) organizing information of paleoseismological record and tsunami deposit by literature research, (2) field survey on tsunami deposit, and (3) designing the analysis code of sediment transport due to tsunami. As to (1), we organize the information gained about tsunami deposits in the database. As to (2), we consolidate methods for surveying and identifying tsunami deposits in the lake based on results of the field survey in Fukui Pref., carried out by JNES. In addition, as to (3), we design the experimental instrument for hydraulic experiment on sediment transport and sedimentation due to tsunamis. These results are reflected in the guideline on the tsunami deposits survey and evaluation. (author)

LAKE-0: a model for the simulation of nuclides transfer in lake scenarios

Energy Technology Data Exchange (ETDEWEB)

Garcia-Olivares, A.; Aguero, A.; Pinedo, P.

1994-07-01

This report presents documentation and a user's manual for the program LAKE-0, a mathematical model of nuclides transfer in lake scenarios. Mathematical equations and physical principles used to develop the code are presented in section 2. The program use is presented in section 3 including input data sets and output data. Section 4 presents two example problems, and some results. The complete program listing including comments is presented in Appendix A. Nuclides are assumed to center the lake via atmospheric deposition and carried by the water runoff and the dragged sediments from the adjacent catchment. The dynamics of the nuclides inside the lake is based in the model proposed by Codell (11) as modified in (5). The removal of concentration from the lake water is due to out flow from the lake and to the transfer of activity to the button sediments. The model has been applied to the Esthwaite Water (54 degree celsius 2 l'N, 03 degree celsius 00'W at 65 m. asi.) in the frame of the VAMP Aquatic Working Group (8) and to Devoke Water (5 21.5'N, 03H8'W at 230 m. asi.). (Author). 13 refs.

Deglaciation, lake levels, and meltwater discharge in the Lake Michigan basin

Science.gov (United States)

Colman, Steven M.; Clark, J.A.; Clayton, L.; Hansel, A.K.; Larsen, C.E.

1994-01-01

The deglacial history of the Lake Michigan basin, including discharge and routing of meltwater, is complex because of the interaction among (1) glacial retreats and re-advances in the basin (2) the timing of occupation and the isostatic adjustment of lake outlets and (3) the depositional and erosional processes that left evidence of past lake levels. In the southern part of the basin, a restricted area little affected by differential isostasy, new studies of onshore and offshore areas allow refinement of a lake-level history that has evolved over 100 years. Important new data include the recognition of two periods of influx of meltwater from Lake Agassiz into the basin and details of the highstands gleaned from sedimentological evidence. Major disagreements still persist concerning the exact timing and lake-level changes associated with the Algonquin phase, approximately 11,000 BP. A wide variety of independent data suggests that the Lake Michigan Lobe was thin, unstable, and subject to rapid advances and retreats. Consequently, lake-level changes were commonly abrupt and stable shorelines were short-lived. The long-held beliefs that the southern part of the basin was stable and separated from deformed northern areas by a hinge-line discontinuity are becoming difficult to maintain. Numerical modeling of the ice-earth system and empirical modeling of shoreline deformation are both consistent with observed shoreline tilting in the north and with the amount and pattern of modern deformation shown by lake-level gauges. New studies of subaerial lacustrine features suggest the presence of deformed shorelines higher than those originally ascribed to the supposed horizontal Glenwood level. Finally, the Lake Michigan region as a whole appears to behave in a similar manner to other areas, both local (other Great Lakes) and regional (U.S. east coast), that have experienced major isostatic changes. Detailed sedimentological and dating studies of field sites and additional

The Younger Dryas phase of Great Salt Lake, Utah, USA

Science.gov (United States)

Oviatt, Charles G.; Miller, D.M.; McGeehin, J.P.; Zachary, C.; Mahan, S.

2005-01-01

Field investigations at the Public Shooting Grounds (a wildlife-management area on the northeastern shore of Great Salt Lake) and radiocarbon dating show that the Great Salt Lake rose to the Gilbert shoreline sometime between 12.9 and 11.2 cal ka. We interpret a ripple-laminated sand unit exposed at the Public Shooting Grounds, and dated to this time interval, as the nearshore sediments of Great Salt Lake deposited during the formation of the Gilbert shoreline. The ripple-laminated sand is overlain by channel-fill deposits that overlap in age (11.9-11.2 cal ka) with the sand, and by wetland deposits (11.1 to 10.5 cal ka). Consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments, including those of emergent aquatic plants, but mollusk shells from spring and marsh deposits yielded anomalously old ages, probably because of a variable radiocarbon reservoir effect. The Bonneville basin was effectively wet during at least part of the Younger Dryas global-cooling interval, however, conflicting results from some Great Basin locations and proxy records indicate that the regional effects of Younger Dryas cooling are still not well understood. ?? 2005 Elsevier B.V. All rights reserved.

Huguangyan Maar Lake (SE China): A solid record of atmospheric mercury pollution history in a non-remote region

Science.gov (United States)

Zeng, Yan; Chen, Jingan; Yang, Yongqiong; Wang, Jianxu; Zhu, Zhengjie; Li, Jian

2017-10-01

Mercury is a highly toxic metal that can cause harm to environment and human health. As atmospheric deposition is the main source of total Hg input to aquatic system in remote and pristine regions, almost all the studies on atmospheric Hg pollution history concentrated in these areas, while the studies in non-remote areas are much limited, especially for the long history records. In this study, Huguangyan Maar Lake, an undisturbed lake system at low altitude in China, was selected to reconstruct the atmospheric mercury pollution history. Variation patterns of TOC, Hg and non-residual Sr in the sediment core indicated that, compared to the direct atmospheric Hg deposition, the effect of either Hg scavenging from water column by algae or the catchment inputs of previously deposited Hg on the Hg accumulation in the lake sediment was limited. The sediment Hg content in Huguangyan Lake was mainly controlled by the atmospheric Hg deposition, and thus accurately reflected the atmospheric Hg pollution history. The Hga (Hg content from atmospheric deposition) in Huguangyan Lake presented a comparable variation pattern to that in remote sites. It had the same variation trend as the global atmospheric Hg before 1950 CE, which could be attributed to the Industrial Revolution. After that, it was mainly controlled by Hg emissions from Asian countries. The variation of Hga also indicated that atmospheric Hg deposition accelerated significantly since 2000 CE. This study, along with other investigations in remote sites in China, showed that the sediment Hg in Huguangyan Lake responded to the atmospheric Hg pollution more sensitively than in the alpine regions. It should be noted that, the more intensive acceleration of Hg deposition in Huguangyan Lake may imply that the South of China suffered from much more serious atmospheric Hg pollution than previous studies revealed.

Transport processes of Cs-137 in lake environments

International Nuclear Information System (INIS)

Hilton, J.; Carrick, T.R.; Lishman, J.P.; Rigg, E.; Davison, W.; Kelly, M.; Hamilton-Taylor, J.

1992-01-01

Radiocesium levels in the waters of the Lake District dropped after the initial deposition following the Chernobyl reactor accident. However they continued to be measurable several years after the event. Caesium 137 concentrations were measured in the sediments of Esthwaite water and Windermere to determine the input of caesium 137 from the catchment area to the lakes. Experiments were conducted to ascertain the chemical conditions such as pH value, adsorption, competing ions which might contribute to maintaining caesium levels in the lakes. (U.K.)

Effects of Simulated Nitrogen Deposition on Soil Respiration in a Populus euphratica Community in the Ebinur Lake Area, a Desert Ecosystem of Northwestern China

Science.gov (United States)

He, Xuemin; Lv, Guanghui; Qin, Lu; Chang, Shunli; Yang, Min; Yang, Jianjun; Yang, Xiaodong

2015-01-01

One of the primary limiting factors for biological activities in desert ecosystems is nitrogen (N). This study therefore examined the effects of N and investigated the responses of an arid ecosystem to global change. We selected the typical desert plant Populus euphratica in a desert ecosystem in the Ebinur Lake area to evaluate the effects of N deposition on desert soil respiration. Three levels of N deposition (0, 37.5 and 112.5 kg·N·ha-1·yr-1) were randomly artificially provided to simulate natural N deposition. Changes in the soil respiration rates were measured from July to September in both 2010 and 2013, after N deposition in April 2010. The different levels of N deposition affected the total soil N, soil organic matter, soil C/N ratio, microorganism number, and microbial community structure and function. However, variable effects were observed over time in relation to changes in the magnitude of N deposition. Simulated high N deposition significantly reduced the soil respiration rate by approximately 23.6±2.5% (Psoil respiration rate by approximately 66.7±2.7% (Psoil moisture, whereas N deposition significantly increased the soil temperature in the 0–5 cm layer (Psoil respiration rate by altering soil properties. PMID:26379186

Fine-scale acoustic telemetry reveals unexpected lake trout, Salvelinus namaycush, spawning habitats in northern Lake Huron, North America

Science.gov (United States)

Binder, Thomas; Farha, Steve A.; Thompson, Henry T.; Holbrook, Christopher; Bergstedt, Roger A.; Riley, Stephen; Bronte, Charles R.; He, Ji; Krueger, Charles C.

2018-01-01

Previous studies of lake trout, Salvelinus namaycush, spawning habitat in the Laurentian Great Lakes have used time- and labour-intensive survey methods and have focused on areas with historic observations of spawning aggregations and on habitats prejudged by researchers to be suitable for spawning. As an alternative, we used fine-scale acoustic telemetry to locate, describe and compare lake trout spawning habitats. Adult lake trout were implanted with acoustic transmitters and tracked during five consecutive spawning seasons in a 19–27 km2 region of the Drummond Island Refuge, Lake Huron, using the VEMCO Positioning System. Acoustic telemetry revealed discrete areas of aggregation on at least five reefs in the study area, subsequently confirmed by divers to contain deposited eggs. Notably, several identified spawning sites would likely not have been discovered using traditional methods because either they were too small and obscure to stand out on a bathymetric map or because they did not conform to the conceptual model of spawning habitat held by many biologists. Our most unique observation was egg deposition in gravel and rubble substrates located at the base of and beneath overhanging edges of large boulders. Spawning sites typically comprised <10% of the reef area and were used consistently over the 5-year study. Evaluation of habitat selection from the perspective of fish behaviour through use of acoustic transmitters offers potential to expand current conceptual models of critical spawning habitat.

WATER TEMPERATURE and other data from LEWIS B. PULLER, ELLIOT and USS DE WERT in the TOGA Area - Pacific, Caribbean Sea and NW Atlantic from 1986-11-07 to 1987-05-31 (NCEI Accession 9400029)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The data in this accession were collected in Caribbean Sea, NW Atlantic (limit-40 W), and TOGA Area - Pacific (30 N to 30 S) from ship ELLIOT, USS DE WERT, and LEWIS...

Lake-sediment evidence for the date of deglaciation of the Hidden Lake area, Kenai Peninsula, Alaska

Science.gov (United States)

Rymer, Michael J.; Sims, John D.

1982-06-01

An abrupt environmental change is reflected in a core from Hidden Lake, Alaska, by differences in sediment type, chlorite crystallinity, and content of organic carbon and water of the sediments. This abrupt change in the sedimentary record occurred about 14,500 14C yr ago and probably marks the time of recession of the glacier from the Hidden Lake drainage basin. Deglaciation of the area was then underway, and rock flour was being deposited in the lake. After recession of the glacier from the Hidden Lake drainage basin, rock flour was no longer introduced, and organic-matter content of the sediment increased. By the dating of these changes in sediment type, we show that retreat of glaciers in this area took place significantly earlier than previously estimated; this agrees with the timing of retreat of alpine glaciers elsewhere in western North America.

MERGANSER: an empirical model to predict fish and loon mercury in New England lakes.

Science.gov (United States)

Shanley, James B; Moore, Richard; Smith, Richard A; Miller, Eric K; Simcox, Alison; Kamman, Neil; Nacci, Diane; Robinson, Keith; Johnston, John M; Hughes, Melissa M; Johnston, Craig; Evers, David; Williams, Kate; Graham, John; King, Susannah

2012-04-17

MERGANSER (MERcury Geo-spatial AssessmeNtS for the New England Region) is an empirical least-squares multiple regression model using mercury (Hg) deposition and readily obtainable lake and watershed features to predict fish (fillet) and common loon (blood) Hg in New England lakes. We modeled lakes larger than 8 ha (4404 lakes), using 3470 fish (12 species) and 253 loon Hg concentrations from 420 lakes. MERGANSER predictor variables included Hg deposition, watershed alkalinity, percent wetlands, percent forest canopy, percent agriculture, drainage area, population density, mean annual air temperature, and watershed slope. The model returns fish or loon Hg for user-entered species and fish length. MERGANSER explained 63% of the variance in fish and loon Hg concentrations. MERGANSER predicted that 32-cm smallmouth bass had a median Hg concentration of 0.53 μg g(-1) (root-mean-square error 0.27 μg g(-1)) and exceeded EPA's recommended fish Hg criterion of 0.3 μg g(-1) in 90% of New England lakes. Common loon had a median Hg concentration of 1.07 μg g(-1) and was in the moderate or higher risk category of >1 μg g(-1) Hg in 58% of New England lakes. MERGANSER can be applied to target fish advisories to specific unmonitored lakes, and for scenario evaluation, such as the effect of changes in Hg deposition, land use, or warmer climate on fish and loon mercury.

Late Glacial and Holocene sedimentary evolution of Czechowskie Lake (Eastern Pomerania, North Central Poland)

Science.gov (United States)

Kordowski, Jarosław; Błaszkiewicz, Mirosław; Kramkowski, Mateusz; Noryśkiewicz, Agnieszka M.; Słowiński, Michał; Tyszkowski, Sebastian; Brauer, Achim; Ott, Florian

2015-04-01

Czechowskie Lake is located in north-central Poland in Tuchola Forest, about 100 kilometers SW away from Gdańsk. In the deepest parts of the lake there are preserved laminated sediments with an excellent Holocene climatic record. The lake has the area of 76,6 ha. Actual water level is at 109,9 m a.s.l. The average depth is 9,59 m, maximal 32 m. It occupies a large subglacial channel, reproduced within the glacifluvial sediments of the last glaciation. The lake has a history reaching back to Pommeranian phase which is proved by analysis of sedimentary succesions in the vicinity of present-day waterbody. Primarily it come to existence as an very variable ice dammed lake but after dead ice and permafrost desintegration it changed into a stable lake. In the terrestrialised part oft the lake and in its litoral zone there were curried out numerous boreholes within limnic and slope sediments. They have been analysed in respect to lithology and structure. Some of them were also investigated palynologically which along with radiocarbon datings allowed to reconstruct major phases of the water level fluctuations. The maximum infilling with the limnic and telmatic sediments reaches over 12 m. In the bottom of the lake there is a marked presence of many overdeepenings with the diameter of dozen or several dozen meters and the depth of up to 10 m with numerous, distinct throughs between them. They favoured the preservation of the lamination in the deepest parts of the lake due to waves hampering and stopping of the density circulation in the lake waterbody. The analysis of limnic sediments revealed considerable spatial and temporal variability mainly in dependance of the area of the water body and water level in time of deposition. In the lake are recorded three distinct phases of lake level decrease. The sedimentary evolution in the isolated minor lake basins showed gradual decrease of mineral and organic deposition in favour for carbonate one although in places separated by

Ground-water availability in the central part of Lake Ontario basin, New York

Science.gov (United States)

Miller, Todd S.; Krebs, Martha M.

1988-01-01

A set of three maps showing surficial geology, distribution of glacial aquifers, and potential well yield in the 708 sq mi central part of the Lake Ontario basin are presented at a scale of 1:125,000. The basin is parallel to Lake Ontario and extends from Rochester in the west to Oswego in the east. Aquifers consisting primarily of sand and gravel formed where meltwaters from glaciers deposited kame and outwash sand and gravel and where wave action along shores of glacial lakes eroded, reworked , and deposited beaches. Thick deposits of well-sorted sand and gravel yield relatively large quantities of water - typically more than 100 gal/min. Aquifers consisting of thin beds of sand and (or) gravel or thick gravel that contain a large proportion of silt and fine sand yield moderate amounts of water, 10 to 100 gal/min. Dug and driven wells that tap fine to medium sand deposits typically yield 1 to 10 gal/min. (USGS)

Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

Energy Technology Data Exchange (ETDEWEB)

Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L; Brown, T A

2007-02-25

A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.

Magnetic and gravity studies of Mono Lake, east-central, California

Science.gov (United States)

Athens, Noah D.; Ponce, David A.; Jayko, Angela S.; Miller, Matt; McEvoy, Bobby; Marcaida, Mae; Mangan, Margaret T.; Wilkinson, Stuart K.; McClain, James S.; Chuchel, Bruce A.; Denton, Kevin M.

2014-01-01

From August 26 to September 5, 2011, the U.S. Geological Survey (USGS) collected more than 600 line-kilometers of shipborne magnetic data on Mono Lake, 20 line-kilometers of ground magnetic data on Paoha Island, 50 gravity stations on Paoha and Negit Islands, and 28 rock samples on Paoha and Negit Islands, in east-central California. Magnetic and gravity investigations were undertaken in Mono Lake to study regional crustal structures and to aid in understanding the geologic framework, in particular regarding potential geothermal resources and volcanic hazards throughout Mono Basin. Furthermore, shipborne magnetic data illuminate local structures in the upper crust beneath Mono Lake where geologic exposure is absent. Magnetic and gravity methods, which sense contrasting physical properties of the subsurface, are ideal for studying Mono Lake. Exposed rock units surrounding Mono Lake consist mainly of Quaternary alluvium, lacustrine sediment, aeolian deposits, basalt, and Paleozoic granitic and metasedimentary rocks (Bailey, 1989). At Black Point, on the northwest shore of Mono Lake, there is a mafic cinder cone that was produced by a subaqueous eruption around 13.3 ka. Within Mono Lake there are several small dacite cinder cones and flows, forming Negit Island and part of Paoha Island, which also host deposits of Quaternary lacustrine sediments. The typical density and magnetic properties of young volcanic rocks contrast with those of the lacustrine sediment, enabling us to map their subsurface extent.

An introduction to the processes, problems, and management of urban lakes

Science.gov (United States)

Britton, L.J.; Averett, R.C.; Ferreira, R.F.

1975-01-01

Lakes are bodies of water formed in depressions on the earth's surface, and as such, act as depositories for a variety of chemical and biological materials. The study of lakes has become increasingly prevalent in recent years. Lakes are a valuable resource, and their multiple uses have made them susceptible to water-quality problems such as algal blooms, sediment deposition and fish kills. These problems are products of the eutrophication process (enrichment, aging and extinction of lakes), which is often accelerated by man. Therefore, it becomes important to understand the properties and processes of lakes which govern lake enrichment, and the measures available to control enrichment.

A catastrophic event in Lake Geneva region during the Early Bronze Age?

Science.gov (United States)

Kremer, Katrina; Yrro, Blé; Marillier, François; Hilbe, Michael; Corboud, Pierre; Rachoud-Schneider, Anne-Marie; Girardclos, Stéphanie

2013-04-01

Similarly to steep oceanic continental margins, lake slopes can collapse, producing large sublacustrine landslides and tsunamis. Lake sediments are excellent natural archives of such mass movements and their study allows the reconstructions of these prehistoric events, such as the 563 AD large tsunami over Lake Geneva (Kremer et al, 2012). In Lake Geneva, more than 100 km of high-resolution seismic reflection profiles reveal the late Holocene sedimentation history. The seismic record shows a succession of five large lens-shaped seismic units (A to I), characterized by transparent/chaotic seismic facies with irregular lower boundaries, and interpreted as mass-movement deposits. These units are interbedded with parallel, continuous and strong amplitude reflections, interpreted as the 'background' lake sediments. The oldest dated mass movement (Unit D) covers a surface of 22 km2 in the deep basin, near the city of Lausanne. This deposit has an estimated minimum volume of 0.18 km3 and thus was very likely tsunamigenic (Kremer et al, 2012). A 12-m-long sediment core confirms the seismic interpretation of the mass movement unit and shows that the uppermost 3 m of Unit D are characterized by deformed hemipelagic sediments topped by a 5 cm thick turbidite. This deposit can be classified as a slump whose scar can be interpreted in the seismic data and visualized by multibeam bathymetry. This slump of Lausanne was likely triggered by an earthquake but a spontaneous slope collapse cannot be excluded (Girardclos et al, 2007). Radiocarbon dating of plant macro-remains reveals that the unit D happened during Early Bronze Age. Three other mass wasting deposits occurred during the same time period and may have been triggered during the same event, either by a single earthquake or by a tsunami generated by the slump of Lausanne. Although the exact trigger mechanism of the all these mass-wasting deposits remains unknown, a tsunami likely generated by this event may have affected the

Magnetostratigraphy and 230Th dating of a drill core from the southeastern Qaidam Basin: Salt lake evolution and tectonic implications

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An-Dong Chen

2018-05-01

Full Text Available The Qarhan Salt Lake area is the Quaternary depocenter of the Qaidam Basin, and carries thick lacustrine sediments, as well as rich potassium and magnesium salt deposits. The abundant resources and thick sediments in this lake provide an ideal place for the study of biogas formation and preservation, salt lake evolution, and the uplift of the Tibetan Plateau. In this study, we attempt to construct a paleomagnetic and 230Th age model and to obtain information on tectonic activity and salt lake evolution through detailed studies on a 1300-m-long drill core (15DZK01 from the northwestern margin of the Qarhan Salt Lake area (Dongling Lake. Based on gypsum 230Th dating, the age of the uppermost clastic deposit was calculated to be around 0.052 Ma. The polarity sequence consist of 13 pairs of normal and reversed zones, which can be correlated with subchrons C2r.1r-C1n of the geomagnetic polarity timescale (GPTS 2012 (from ∼2.070 Ma to ∼0.052 Ma. Sedimentary characteristics indicate that Dongling Lake witnessed freshwater environment between ∼2.070 Ma and 1.546 Ma. During this period, the sedimentary record reflects primarily lakeshore, shallow-water and swamp environments, representing favourable conditions for the formation of hydrocarbon source rocks. Between 1.546 Ma and ∼0.052 Ma, the Dongling Lake was in sulphate deposition stage, which contrasts with the central Qarhan Salt Lake area, where this stage did not occur in the meantime. During this stage, Dongling Lake was in a shallow saltwater lake environment, but several periods of reduced salinity occurred during this stage. During the late Pleistocene at ∼0.052 Ma, the Dongling Lake experienced uplift due to tectonic activity, and saltwater migrated through the Sanhu Fault to the central Qarhan Salt Lake area, resulting in the absence of halite deposition stage. The residual saline water was concentrated into magnesium-rich brine due to the lack of freshwater, and few

Volcanic influence of Mt. Fuji on the watershed of Lake Motosu and its impact on the lacustrine sedimentary record

Science.gov (United States)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Vander Auwera, Jacqueline; Obrochta, Stephen; Boes, Evelien; Nakamura, Atsunori; Fujiwara, Osamu; Shishikura, Masanobu; Schmidt, Sabine; Siani, Giuseppe; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.; QuakeRecNankai Team

2018-01-01

Lacustrine sediments are particularly sensitive to modifications within the lake catchment. In a volcanic area, sedimentation rates are directly affected by the history of the volcano and its eruptions. Here, we investigate the impact of Mt. Fuji Volcano (Japan) on Lake Motosu and its watershed. The lacustrine infill is studied by combining seismic reflection profiles and sediment cores. We show evidence of changes in sedimentation patterns during the depositional history of Lake Motosu. The frequency of large mass-transport deposits recorded within the lake decreases over the Holocene. Before 8000 cal yr BP, large sublacustrine landslides and turbidites were filling the lacustrine depression. After 8000 cal yr BP, only one large sublacustrine landslide was recorded. The change in sedimentation pattern coincides with a change in sediment accumulation rate. Over the last 8000 cal yr BP, the sediment accumulation rate was not sufficient enough to produce large sublacustrine slope failures. Consequently, the frequency of large mass-transport deposits decreased and only turbidites resulting from surficial slope reworking occurred. These constitute the main sedimentary infill of the deep basin. We link the change in sediment accumulation rate with (i) climate and vegetation changes; and (ii) the Mt. Fuji eruptions which affected the Lake Motosu watershed by reducing its size and strongly modified its topography. Moreover, this study highlights that the deposition of turbidites in the deep basin of Lake Motosu is mainly controlled by the paleobathymetry of the lakefloor. Two large mass-transport deposits, occurring around 8000 cal yr BP and 2000 cal yr BP respectively, modified the paleobathymetry of the lakefloor and therefore changed the turbidite depositional pattern of Lake Motosu.

Pleistocene lake level changes in Western Mongolia

Science.gov (United States)

Borodavko, P. S.

2009-04-01

Global cooling in the Early Pleistocene caused extensive continental glaciation in the northern hemisphere including the arid areas of Central Asia. The reduction of temperatures (particularly summer temperatures) reduced evaporation and strengthened the importance of precipitation. The simultaneity of "lakes periods" (pluvials) and stages of glaciation is established experience confirmed by investigations in the west of North America and Russia. In the Mongolian Great Lakes Depression new evidence for similar conditions is found. The Great Lakes Depression is one of the largest in Central Asia, and is divided into 2 main Lakes basins: Hyargas Lake Basin and Uvs Lake Basin. The basin is 600-650 km in length with a width of 200-250 km in the north and 60-100 km in the south. Total catchment area is about 186600 km2. The elevation of the basin floor is from 1700 m a.s.l. to 760 m a.s.l., decreasing to the north and south-east. The depression extends south-north and is bounded by mountains: Tannu-Ola to the north, Hangai to the east; Gobi Altai to the south and Mongolian Altay to the west. The maximum elevation of the mountains is 4000 m a.s.l. There are some mountains with an elevation between 2000 and 3000 m a.s.l in the lake catchment. These mountains are not glaciated today. The geological record [1] suggests the Great Lakes Depression already existed in the Mesozoic, but assumed its modern form only during the Pliocene-Quaternary when tectonic movements caused the uplift of the surrounding mountains. A phase of tectonic stability occurred during the Late Quaternary. The depression is filled by Quaternary fluvial, aeolian and lacustrine deposits (e.g. sand, pebbles). The Neogene deposits are represented by coloured clay, marl, sand and sandstone [1]. Hyargas Lake is the end base level of erosion of the lake group consisting of the Hara-Us Nur, Dorgon, Hara Nur and Airag lakes. Hyargas is one of the largest lakes in Mongolia, with a water surface of 1,407 km2. The

Drastic lake level changes of Lake Van (eastern Turkey) during the past ca. 600 ka: climatic, volcanic and tectonic control

Science.gov (United States)

Cukur, D.; Krastel, S.; Schmincke, H.; Sumita, M.; Tomonaga, Y.; Damci, E.

2013-12-01

Lake Van is the largest soda lake in the world with a present surface of 3,574 km2 and a maximum water depth of 450 m. Sedimentary deposits in the lake preserve one of the most complete record of continental climate in the Middle East since the Middle Pleistocene. We studied these deposits to characterize the evolution of the lake level and its possible relationships with changes in climate, volcanic, and regional tectonics since the formation of the lake ca. 600 ka ago. Changes in lake level were determined based on high-resolution seismic reflection profiles showing erosional surfaces, changes in stratal geometries such as downward shifts in coastal onlap, and recognition of distinctive stratigraphic features such as prograding delta clinoforms. Our results show that Lake Van has undergone drastic changes in surface elevation by as much as 600 meters over the past ca. 600 ka. Five major lowstands occurred at ca. ~600 ka, ca. 365-340 ka, ca 290-230 ka; ca. 150-130 ka; and ca. 30-14 ka. During a first period (A) (ca. 600-ca 230 ka) lake levels changed drastically by hundreds of m but at longer time intervals between low and high stands. Changes occurred more frequently but mostly by a few tens of m during the past ca. 230 ka years where we can distinguish a first period (B1) of stepwise transgressions between ca. 230 and 150 ka followed by a short regression between ca. 150 and 130 ka. Lake level rose stepwise again during period B2 lasting until ca 30 ka. During the past 30 ka a regression and a final transgression each lasted ca. 15 ka years. The major lowstand periods in Lake Van occurred during glacial periods, arguing for a climatic control of these lake-level fluctuations (i.e., significantly reduced precipitation leading to lake level low stands). Although climate forcing may have been the dominant cause for the drastic lake level changes of Lake Van, volcanic and tectonic forcing factors are also invoked. For example, the number of distinct tephra layers

Geomorphic and sedimentologic evidence for the separation of Lake Superior from Lake Michigan and Huron

Science.gov (United States)

Johnston, J.W.; Thompson, T.A.; Wilcox, D.A.; Baedke, S.J.

2007-01-01

A common break was recognized in four Lake Superior strandplain sequences using geomorphic and sedimentologic characteristics. Strandplains were divided into lakeward and landward sets of beach ridges using aerial photographs and topographic surveys to identify similar surficial features and core data to identify similar subsurface features. Cross-strandplain, elevation-trend changes from a lowering towards the lake in the landward set of beach ridges to a rise or reduction of slope towards the lake in the lakeward set of beach ridges indicates that the break is associated with an outlet change for Lake Superior. Correlation of this break between study sites and age model results for the strandplain sequences suggest that the outlet change occurred sometime after about 2,400 calendar years ago (after the Algoma phase). Age model results from one site (Grand Traverse Bay) suggest an alternate age closer to about 1,200 calendar years ago but age models need to be investigated further. The landward part of the strandplain was deposited when water levels were common in all three upper Great Lakes basins (Superior, Huron, and Michigan) and drained through the Port Huron/Sarnia outlet. The lakeward part was deposited after the Sault outlet started to help regulate water levels in the Lake Superior basin. The landward beach ridges are commonly better defined and continuous across the embayments, more numerous, larger in relief, wider, have greater vegetation density, and intervening swales contain more standing water and peat than the lakeward set. Changes in drainage patterns, foreshore sediment thickness and grain size help in identifying the break between sets in the strandplain sequences. Investigation of these breaks may help identify possible gaps in the record or missing ridges in strandplain sequences that may not be apparent when viewing age distributions and may justify the need for multiple age and glacial isostatic adjustment models. ?? 2006 Springer Science

Pollutant transformations over Lake Michigan

International Nuclear Information System (INIS)

Alkezweeny, A.J.; Arbuthnot, D.R.; Busness, K.M.; Easter, R.C.; Hales, J.M.; Lee, R.N.; Young, J.M.

1979-01-01

An aircraft, a chartered boat, and a constant altitude balloon were used to study pollutant transformations over Lake Michigan in a Lagrangian frame of reference. The experiments were conducted during the summer under strong atmospheric stability where diffusion and dry deposition of pollutants can be neglected

Radiocaesium in lake fishes - pre and post Chernobyl evaluation of transfer factors from deposition

International Nuclear Information System (INIS)

Dominici, G.; Malvicini, A.

1991-01-01

The amounts and concentration of radiocaesium in fishes and in lake water, taken from major lakes in the Varese region for the periods pre and post Chernobyl are reported. Some relationships are obtained which permit to forecast the intake on behalf of the fishes knowing the quantity of radioactivity entering into the lake bed. (15 tabs; 18 figs)

Study on behavior of Cs-137 and Pu-239, 240 in lake and marine environments on basis of sediment analysis

International Nuclear Information System (INIS)

Nagao, Seiya

1998-01-01

An investigation was made on the sediment mechanisms of artificial radioactive isotopes in relation to environmental factors through utilizing the differences in deposition behaviors of 137 Cs and 239,240 Pu. Cumulus deposit samples were collected from 4 lake and 7 ocean areas of different environmental and deposit conditions; oligotrophic, mesotrophic, acidtrophic and dystrophic lakes, and coastal and hemipelagic ocean areas. After purification of these deposit samples using ionchromatography, β-ray from 137 Cs and α-ray from Pu were spectroscopically determined to plat the respective concentration as a function of the depth in core. Based on the data of mean ratio of 239,240 Pu/ 137 Cs as to the organic sulfides and residual fractions and the total deposits, it was thought that when the ratio of Pu/Cs of lake deposits was higher than the fallout value, organic materials in the lake might be involved. Pu was mostly abundant in organic fractions compared with Cs, whereas Cs was present in all the four fractions of carbonates, oxides, organic materials and aluminosilicates. (M.N.)

Recent geologic development of Lake Michigan (U.S.A.)

Science.gov (United States)

Gross, D.L.; Cahill, R.A.

1983-01-01

The stresses placed on Lake Michigan since the advent of industrialization require knowledge of the sedimentology of the whole lake in order to make informed decisions for environmental planning. Sediment accumulation rates are low: areas of the lake receiving the most sediment average only 1 mm a-1; deep-water basins average 0.1 to 0.5 mm a-1; and large areas are not receiving any sediment. Sediment was deposited rapidly (typically 5 mm a-1), in the form of rock flour, during the deglaciation of both Lake Michigan and Lake Superior Basins. Then the rate of accumulation decreased by 80-90% and has remained relatively constant since final deglaciation. Because active sedimentation occurs mostly in the deep water areas of the lake, the sediment remains undisturbed and contains a record of the chemical history of the lake. ?? 1983 Dr W. Junk Publishers.

Glacial lakes in Austria - Distribution and formation since the Little Ice Age

Science.gov (United States)

Buckel, J.; Otto, J. C.; Prasicek, G.; Keuschnig, M.

2018-05-01

Glacial lakes constitute a substantial part of the legacy of vanishing mountain glaciation and act as water storage, sediment traps and sources of both natural hazards and leisure activities. For these reasons, they receive growing attention by scientists and society. However, while the evolution of glacial lakes has been studied intensively over timescales tied to remote sensing-based approaches, the longer-term perspective has been omitted due a lack of suitable data sources. We mapped and analyzed the spatial distribution of glacial lakes in the Austrian Alps. We trace the development of number and area of glacial lakes in the Austrian Alps since the Little Ice Age (LIA) based on a unique combination of a lake inventory and an extensive record of glacier retreat. We find that bedrock-dammed lakes are the dominant lake type in the inventory. Bedrock- and moraine-dammed lakes populate the highest landscape domains located in cirques and hanging valleys. We observe lakes embedded in glacial deposits at lower locations on average below 2000 m a.s.l. In general, the distribution of glacial lakes over elevation reflects glacier erosional and depositional dynamics rather than the distribution of total area. The rate of formation of new glacial lakes (number, area) has continuously accelerated over time with present rates showing an eight-fold increase since LIA. At the same time the total glacier area decreased by two-thirds. This development coincides with a long-term trend of rising temperatures and a significant stepping up of this trend within the last 20 years in the Austrian Alps.

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

Consequences of radioactive deposition on aquatic environments

International Nuclear Information System (INIS)

Suolanen, V.

1994-12-01

The publication concentrates on the analyses of the main effects of radioactive deposition on Nordic aquatic environments. A modelling approach is applied for predicting the temporal behaviour of concentrations in fish of inland freshwater ecosystems. The observed values are considered in parallel with the calculations. The time-integrated consequences, the radiation doses are estimated for the relatively significant dose pathways. After a preliminary study of various lake environments in Nordic countries, three representative examples of lake systems were selected for closer consideration: small forest lake, medium-sized forest lake and mountain lake. The effects of changes in the trophic levels of lakes are also tentatively accounted for. The results of the analyses indicate that the radiological consequences of shallow forest lakes are greater than those of mountain lakes which usually have shorter turnover times compared to forest lakes. In long-term consideration, the fish ingestion pathway may in general become important and, in addition to the external exposure, has a high contribution to the expected doses. (orig.) (8 refs., 11 figs., 9 tabs.)

Late Pleistocene Hansel Valley basaltic ash, northern Lake Bonneville, Utah, USA

Science.gov (United States)

Miller, D.M.; Oviatt, Charles G.; Nash, B.P.

2008-01-01

The Hansel Valley ash bed lies within 5 cm of the base of deposits of Lake Bonneville (???28 ka) in the vicinity of Great Salt Lake and provides a useful stratigraphic marker for this area of the lake basin. However, it has not been matched to an eruptive edifice, presumably because such an edifice was eroded by waves of Lake Bonneville. We present data for the chemical composition of the tephra and for possible matching lavas and tephras of the region, as well as grain size data for the tephra in an attempt to identify the location of the eruption. Matches with other tephras are negative, but lavas near the coarsest ash deposits match well with the distinctive high values of TiO2 and P2O5 of the ash. Neither chemistry nor grain size data points uniquely to a source area, but an area near the northwest shore of Great Salt Lake and within Curlew Valley is most likely. The Hansel Valley ash is an example of an ash that has no direct numerical date from proximal deposits, despite considerable study, yet nonetheless is useful for stratigraphic studies by virtue of its known stratigraphic position and approximate age. Basaltic tephras commonly are not as widespread as their rhyolitic counterparts, and in some cases apparently are produced by eruptive sources that are short lived and whose edifices are not persistent. ?? 2007 Elsevier Ltd and INQUA.

Shifts in alpine lakes' ecosystems in Japan driven by increasing Asian dusts

Science.gov (United States)

Tsugeki, N. K.; Tani, Y.; Ueda, S.; Agusa, T.; Toyoda, K.; Kuwae, M.; Oda, H.; Tanabe, S.; Urabe, J.

2011-12-01

Recently in East Asia the amount of fossil fuel combustion have increased with economic growth. It has caused a problem of trans-boundary air pollution in the whole of eastern Asia. Furthermore, Asian dust storms contribute episodically to the global aerosol load. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. If biologically important nutrients such as nitrogen (N) and phosphorus (P) are transported via air dust, the atmospheric deposition of the dust may have serious impacts on recipient aquatic ecosystems because the biological production is limited by these nutrient elements. A previous report using sedimentary records has evaluated that atmospheric P inputs to the alpine lakes in the United States increased fivefold following the increased western settlement to this country during the nineteenth century. Since P is the most deficient nutrient for production in many lakes increase in P loading through atmospheric deposition of anthropogenically-derived dust might greatly affect the lake ecosystems. We examined fossil pigments and zooplankton remains from Pb-dated sediments taken from a high mountain lake of Hourai-Numa, located in the Towada-Hachimantai National Park of Japan, to uncover historical changes in the phyto- and zooplankton community over the past 100 years. Simultaneously, we measured the biogeochemical variables of TOC, TN, TP, δ13C, δ15N, and 206Pb/207Pb, 208Pb/207Pb in the sediments to identify environmental factors causing such changes. As a result, despite little anthropogenic activities in the watersheds, alpine lakes in Japan Islands increased algal and herbivore plankton biomasses by 3-6 folds for recent years depending on terrestrial the surrounded vegetations and landscape conditions. Biological and biogeochemical proxies recorded in the lake sediments indicate that this eutrophication occurred after the 1990s when P deposition increased due to atmospheric loading transported from Asian

Geology and mineral deposits of Churchill County, Nevada

Science.gov (United States)

Willden, Ronald; Speed, Robert C.

1974-01-01

Churchill County, in west-central Nevada, is an area of varied topography and geology that has had a rather small total mineral production. The western part of the county is dominated by the broad low valley of the Carson Sink, which is underlain by deposits of Lake Lahontan. The bordering mountain ranges to the west and south are of low relief and underlain largely by Tertiary volcanic and sedimentary units. Pre-Tertiary rocks are extensively exposed east of the Carson Sink in the Stillwater Range, Clan Alpine Mountains, Augusta Mountains, and New Pass Mountains. The eastern valleys are underlain by Quaternary alluvial and lacustrine deposits contemporaneous with the western deposits of Lake Lahontan. The eastern mountain ranges are more rugged than the western ranges and have higher relief; the eastern valleys are generally narrower.

Streamwater fluxes of total mercury and methylmercury into and out of Lake Champlain

International Nuclear Information System (INIS)

Shanley, James B.; Chalmers, Ann T.

2012-01-01

From 2000 to 2004, we sampled for total mercury (THg) and methylmercury (MeHg) in inlet streams to Lake Champlain, targeting high flow periods to capture increases in THg and MeHg concentrations with increasing flow. We used these data to model stream THg and MeHg fluxes for Water Years 2001 through 2009. In this mountainous forested basin with a high watershed-to-lake area ratio of 18, fluvial export from the terrestrial watershed was the dominant source of Hg to the lake. Unfiltered THg and MeHg fluxes were dominated by the particulate fraction; about 40% of stream THg was in the filtered ( −2 yr −1 , or about 13% of atmospheric Hg wet and dry deposition to the basin. THg export from the lake represented only about 3% of atmospheric Hg input to the basin. - Highlights: ► We monitored total mercury and methylmercury in major tributaries to Lake Champlain. ► Mercury and methylmercury export was primarily as particulates during high flow. ► Only 13% of atmospheric total mercury input reached the lake via streams. ► Only 3% of atmospheric total mercury input reached the lake outlet. - Eighty-seven percent of total mercury deposition to the Lake Champlain basin is retained in the terrestrial basin; stream export of total and methylmercury to the lake is primarily in the particulate phase.

Orbital rhythms, monsoons, and playa lake response, Olduvai basin, Equatorial East Africa at 1.85-1.75 Ma

Science.gov (United States)

Ashley, G. M.

2001-12-01

Wet-dry cycles in low latitudes are generally attributed to changes in solar radiation related to the 21 kyr tempo of orbital precession. Stronger insolation drives stronger summer monsoon maxima that increase precipitation and in closed basins produce larger lakes. However, a Plio-Pleistocene record from a closed rift-platform basin near the equator suggests that the obliquity (41 kyr) signal is also present. The 1.85-1.75 Ma sedimentary record deposited in the Olduvai basin, 3oN, reveals clear evidence of periodic expansion and contraction of paleolake Olduvai. The closed basin was 50 km wide and infilled by volcaniclastic material from Ngorongoro volcanic complex in several depositional environments.. A saline-alkaline lake expanded up to 15 km in width and deposited Mg-smectitic claystones. The lake clays in the central basin vary in clay mineralogy and the number of calcite crystal horizons reflecting compositional changes in the lake water. Lake expansions are recorded at the margins where lake clays are intercollated with deltaic and ephemeral fluvial sands and with lake margin wetland deposits. Marine dust records, off both west and east Africa, suggest that the precession signal (21kyr) dominated the climate until 2.8 Ma and the obliquity signal (41kyr) from 2.8 to 0.9 Ma (deMenocal, 1995). In contrast, the stratigraphic sequence for playa lake expansion at Olduvai, that is constrained by the tephra chronology (1.85-1.75 Ma) and paleomagnetic record, documents the combined effects of both obliquity and precession cycles.

Chernobyl accident. The ground deposition of radionuclides in Padana plain and in Alps Valleys and the radioactive contamination of the Como lake

Energy Technology Data Exchange (ETDEWEB)

Capra, D; Facchini, U; Gianelle, V; Ravasini, G; Ravera, O; Volta, L; Pizzola, A; Bacci, P

1988-01-01

The radioactive cloud released during the Chernobyl accident reached the Padana plain and Lombardy in the night of April 30th 1986; the cloud remained in the northern Italian skies for a few days and then disappeared either dispersed by winds and washed by rains. The evidence in atmosphere of radionuclides as Tellurium, Iodine, Cesium, was promptly observed. The intense rain, in first week of may, washed the radioactivity and fall-out contamined the land, soil, grass. The present work concerns the overall contamination of the Northern Italy territory and in particular the radioactive fall-out in the Lakes region. Samples of soil have been measured at the gamma spectroscope; a correlation is found between the radionuclides concentration in soil samples and the rain intensity, when appropriate deposition models are considered. A number of measurements has been done on the Como'lake ecosystem: sediments, plankton, fishes and the overall fall-out in the area has been investigated.

GEOLOGICAL FEATURES OF NEOGENE BASINS HOSTING BORATE DEPOSITS: AN OVERVIEW OF DEPOSITS AND FUTURE FORECAST, TURKEY

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Cahit HELVACI

2015-12-01

hydroboracite are present in west Anatolia, Death Valley, California, and Sijes (Argentina. Quaternary borates are present in salars (Andes and playa- lakes and salt pans (USA-Tibet. Boron is a rare element in the Earth’s crust, but extraordinary concentrations can be found in limited places. The formation of borate deposits can be classified as follows: a skarn group associated with intrusives and consisting of silicates and iron oxides; a magnesium oxide group hosted by marine evaporitic sediments; and a sodium– and calcium–borate hydrates group associated with playa-lake sediments and explosive volcanic activity. Some conditions are essential for the formation of economically viable borate deposits in playa-lake volcano-sedimentary sequences: formation of playa-lake environment; concentration of boron in the playa lake, sourced from andesitic to rhyolitic volcanics, direct ash fall into the basin, or hydrothermal solutions along graben faults; thermal springs near the area of volcanism; arid to semi-arid climatic conditions; and lake water with a pH of between 8.5 and 11. A borate is defined as any compound that contains or supplies boric oxide (B2O3. A large number of minerals contain boric oxide, but the three that are most important from a worldwide commercial standpoint are borax, ulexite, and colemanite, which are produced in a limited number of countries. Turkey has the largest borax, ulexite and colemanite reserves in the world and all the world’s countries are dependent upon the colemanite and ulexite reserves of Turkey. Most of the world’s commercial borate deposits are mined by open pit methods. Brines from Searles Lake, and presumably the Chinese sources, are recovered by either controlled evaporation or carbonation. Boric acid is one of the final products produced from most of the processes. Further research on the mineralogy and chemistry of borate minerals and associated minerals will the production and utilization of borate end-products. �

Numerical experiment on tsunami deposit distribution process by using tsunami sediment transport model in historical tsunami event of megathrust Nankai trough earthquake

Science.gov (United States)

Imai, K.; Sugawara, D.; Takahashi, T.

2017-12-01

A large flow caused by tsunami transports sediments from beach and forms tsunami deposits in land and coastal lakes. A tsunami deposit has been found in their undisturbed on coastal lakes especially. Okamura & Matsuoka (2012) found some tsunami deposits in the field survey of coastal lakes facing to the Nankai trough, and tsunami deposits due to the past eight Nankai Trough megathrust earthquakes they identified. The environment in coastal lakes is stably calm and suitable for tsunami deposits preservation compared to other topographical conditions such as plains. Therefore, there is a possibility that the recurrence interval of megathrust earthquakes and tsunamis will be discussed with high resolution. In addition, it has been pointed out that small events that cannot be detected in plains could be separated finely (Sawai, 2012). Various aspects of past tsunami is expected to be elucidated, in consideration of topographical conditions of coastal lakes by using the relationship between the erosion-and-sedimentation process of the lake bottom and the external force of tsunami. In this research, numerical examination based on tsunami sediment transport model (Takahashi et al., 1999) was carried out on the site Ryujin-ike pond of Ohita, Japan where tsunami deposit was identified, and deposit migration analysis was conducted on the tsunami deposit distribution process of historical Nankai Trough earthquakes. Furthermore, examination of tsunami source conditions is possibly investigated by comparison studies of the observed data and the computation of tsunami deposit distribution. It is difficult to clarify details of tsunami source from indistinct information of paleogeographical conditions. However, this result shows that it can be used as a constraint condition of the tsunami source scale by combining tsunami deposit distribution in lakes with computation data.

Spatiotemporal patterns of mercury accumulation in lake sediments of western North America

Science.gov (United States)

Drevnick, Paul; Cooke, Colin A.; Barraza, Daniella; Blais, Jules M.; Coale, Kenneth; Cumming, Brian F.; Curtis, Chris; Das, Biplob; Donahue, William F.; Eagles-Smith, Collin A.; Engstrom, Daniel R.; Fitzgerald, William F.; Furl, Chad V.; Gray, John R.; Hall, Roland I.; Jackson, Togwell A.; Laird, Kathleen R.; Lockhart, W. Lyle; Macdonald, Robie W.; Mast, M. Alisa; Mathieu, Callie; Muir, Derek C.G.; Outridge, Peter; Reinemann, Scott; Rothenberg, Sarah E.; Ruiz-Fernandex, Ana Carolina; St. Louis, V.L.; Sanders, Rhea; Sanei, Hamed; Skierszkan, Elliott; Van Metre, Peter C.; Veverica, Timothy; Wiklund, Johan A.; Wolfe, Brent B.

2016-01-01

For the Western North America Mercury Synthesis, we compiled mercury records from 165 dated sediment cores from 138 natural lakes across western North America. Lake sediments are accepted as faithful recorders of historical mercury accumulation rates, and regional and sub-regional temporal and spatial trends were analyzed with descriptive and inferential statistics. Mercury accumulation rates in sediments have increased, on average, four times (4×) from 1850 to 2000 and continue to increase by approximately 0.2 μg/m2 per year. Lakes with the greatest increases were influenced by the Flin Flon smelter, followed by lakes directly affected by mining and wastewater discharges. Of lakes not directly affected by point sources, there is a clear separation in mercury accumulation rates between lakes with no/little watershed development and lakes with extensive watershed development for agricultural and/or residential purposes. Lakes in the latter group exhibited a sharp increase in mercury accumulation rates with human settlement, stabilizing after 1950 at five times (5×) 1850 rates. Mercury accumulation rates in lakes with no/little watershed development were controlled primarily by relative watershed size prior to 1850, and since have exhibited modest increases (in absolute terms and compared to that described above) associated with (regional and global) industrialization. A sub-regional analysis highlighted that in the ecoregion Northwestern Forest Mountains, mercury deposited to watersheds is delivered to lakes. Research is warranted to understand whether mountainous watersheds act as permanent sinks for mercury or if export of “legacy” mercury (deposited in years past) will delay recovery when/if emissions reductions are achieved.

Enumeration and characterization of microorganisms associated with the uranium ore deposit at Cigar Lake, Canada. Informal report

International Nuclear Information System (INIS)

Francis, A.J.; Joshi-Tope, G.; Gillow, J.B.; Dodge, C.J.

1994-03-01

The high-grade uranium deposit at Cigar Lake, Canada, is being investigated as a natural analog for the disposal of nuclear fuel waste. Geochemical aspects of the site have been studied in detail, but the microbial ecology has not been fully investigated. Microbial populations in an ore sample and in groundwater samples from the vicinity of the ore zone were examined to determine their effect on uranium mobility. Counts of the total number of bacteria and of respiring bacteria were obtained by direct microscopy, and the viable aerobic and anaerobic bacteria were assessed as colony forming units (CFUs) by the dilution plating technique. In addition, the population distribution of denitrifiers, fermenters, iron- and sulfur-oxidizers, iron- and sulfate-reducers, and methanogens was determined by the most probable number (MPN) technique

MERGANSER - A Predictive Model of Mercury in Fish and Loons in New England Lakes

Science.gov (United States)

Moore, R. B.; Shanley, J. B.; Smith, R. A.; Miller, E. K.; Simcox, A.; Kamman, N. C.; Nacci, D. E.; Robinson, K. W.; Johnston, J. M.; Hughes, M.; Johnston, C. M.; Williams, K.; Graham, J.; King, S.

2010-12-01

MERGANSER (MERcury Geo-spatial AssessmeNtS for the New England Region) is an empirical least squares multiple regression model using atmospheric deposition of mercury (Hg) and readily obtainable lake and watershed features to predict fish and common loon Hg in New England lakes. We modeled lakes larger than 8 ha and with drainage area completely within the USA (4404 lakes), using 3827 fish (12 species) and loon Hg values from 420 lakes. MERGANSER predictor variables included Hg deposition, watershed alkalinity, percent wetlands, percent forest canopy, percent agriculture, drainage area, population, mean annual temperature and watershed slope. The model returns fish tissue or loon blood Hg for user-entered species and length. MERGANSER explained 63% of the variance in fish fillet and loon Hg concentrations. MERGANSER predicted that 32-cm small mouth bass had a median Hg concentration of 0.53 µg g-1 and exceeded EPA’s maximum contaminant level (MCL) of 0.3 µg/g Hg in 90% of New England lakes. Common loon had a median Hg concentration of 1.07 µg g-1 and was in the moderate or higher risk category of >1 µg/g Hg in 58% of New England lakes.

Multi-proxy paleoenvironmental reconstruction of saline lake carbonates: Paleoclimatic and paleogeographic implications (Priabonian-Rupelian, Issirac Basin, SE France)

Science.gov (United States)

Lettéron, Alexandre; Fournier, François; Hamon, Youri; Villier, Loïc; Margerel, Jean-Pierre; Bouche, Alexandre; Feist, Monique; Joseph, Philippe

2017-08-01

A 200-m thick carbonate succession has been deposited in shallow-water, saline lake environments during the Priabonian-Rupelian in the Issirac Basin (South-East France). The palaeoenvironmental and palaeogeographic significance of such saline lake carbonates has been characterized on the basis of a multi-proxy analysis including 1) depositional and diagenetic features, 2) biological components (molluscs, ostracods, benthic foraminifers, characean) and 3) carbon, oxygen and strontium stable isotopes. Biological associations are indicative of dominantly shallow (climate (dry versus humid) are the three key factors controlling the water composition, carbonate production and depositional environments in the Issirac lake. Although the ASCI (Alès-Issirac-Saint-Chaptes) lacustrine system likely represents an athalassic (inland) lake system evolving through times, the stable isotope composition (C, O and Sr) of carbonates strongly suggests the occurrence of transient connections of the ASCI lake water with water bodies influenced by seawater and/or fed with sulfates deriving from Triassic evaporites. The Issirac Basin may be therefore interpreted as a sill area connecting the ASCI lacustrine system with the Rhône valley (Mormoiron and Valence) saline lake systems during maximum flooding periods. Finally, changes in depositional features, biota and stable isotope composition of carbonates in unit U3 suggest a transition from relatively dry to more humid climate during the uppermost Priabonian or earliest Rupelian.

The PIRLA project: paleoecological investigations of recent lake acidification

Energy Technology Data Exchange (ETDEWEB)

Charles, D F; Whitehead, D R

1986-12-19

The PIRLA project is a broadly interdisciplinary paleolimnological investigation of five to fifteen comparable watershed lake systems from each of four low-alkalinity regions in North America that are currently receiving acid deposition. The areas are the Adirondack Mountains (N.Y.), northern New England, northern Great Lakes states, and northern Florida. The primary objective of the study is to provide a detailed reconstruction of the recent acidification histories of a representative suite of lakes from each of the regions. The study will increase our understanding of the timing, rates, and magnitude of acidification (and other chemical changes), and the regional and inter-regional patterns of lake acidification. 3 figs., 2 tabs., 41 refs.

Final report of the AECL/SKB Cigar Lake analog study

International Nuclear Information System (INIS)

Cramer, J.J.

1994-07-01

The Cigar Lake uranium deposit is located in northern Saskatchewan, Canada. The 1.3-billion-year-old deposit is located at a depth of about 450 m below surface in a water-saturated sandstone at the unconformity contact with the high-grade metamorphic rocks of the Canadian Shield. The uranium mineralization, consisting primarily of uraninite (UO 2 ), is surrounded by a clay-rich halo in both sandstone and basement rocks, and remains extremely well preserved and intact. The average grade of the mineralization is ∼ 8 wt.% U; locally grades are as high as ∼ 55 wt.%U. The Cigar lake deposit has many features that parallel those being considered within the Canadian concept for disposal of nuclear fuel waste. Specifically, the deposit provides analog information relevant to the stability of UO 2 fuel waste, the performance of clay-based barriers, radionuclide migration, colloid formation, radiolysis, fission-product geochemistry and general aspects of water-rock interaction. The main geochemical studies on this deposit focus on the evolution of groundwater compositions in the deposit and on their redox chemistry with respect to the uranium, iron and sulphide systems. Since 1984, through cooperation from the owners of the Cigar lake deposit, analog studies have been conducted. AECL, with support from Ontario Hydro under the auspices of the CANDU Owners Group, initiated international participation in 1989 through collaboration with the Swedish Nuclear Fuel and Waste Management Company (SKB) and, more recently, with the Los Alamos National Laboratory (LANL). This report gives the results of the various studies carried out during the 3-year collaboration between AECL and SKB, as well as a summary of the LANL study. It provides detailed information on the generated databases and models, and integrates this information into conclusions for use in safety assessment of the Canadian, Swedish and United States disposal concepts. 15 refs., 25 figs., 55 tabs

Clay minerals trap hydrogen in the Earth's crust: Evidence from the Cigar Lake uranium deposit, Athabasca

Science.gov (United States)

Truche, Laurent; Joubert, Gilles; Dargent, Maxime; Martz, Pierre; Cathelineau, Michel; Rigaudier, Thomas; Quirt, David

2018-07-01

Hydrogen (H2)-rich fluids are observed in a wide variety of geologic settings including gas seeps in serpentinized ultramafic rocks, sub-seafloor hydrothermal vents, fracture networks in crystalline rocks from continental and oceanic crust, and volcanic gases. Natural hydrogen sources can sustain deep microbial ecosystems, induce abiotic hydrocarbons synthesis and trigger the formation of prebiotic organic compounds. However, due to its extreme mobility and small size, hydrogen is not easily trapped in the crust. If not rapidly consumed by redox reactions mediated by bacteria or suitable mineral catalysts it diffuses through the rocks and migrates toward the surface. Therefore, H2 is not supposed to accumulate in the crust. We challenge this view by demonstrating that significant amount of H2 may be adsorbed by clay minerals and remain trapped beneath the surface. Here, we report for the first time H2 content in clay-rich rocks, mainly composed of illite, chlorite, and kaolinite from the Cigar Lake uranium ore deposit (northern Saskatchewan, Canada). Thermal desorption measurements reveal that H2 is enriched up to 500 ppm (i.e. 0.25 mol kg-1 of rock) in these water-saturated rocks having a very low total organic content (reported elsewhere for pure clay minerals or shales. Sudoite (Al-Mg di-trioctahedral chlorite) is probably the main mineral responsible for H2 adsorption in the present case. The presence of multiple binding sites in interlinked nanopores between crystal layers of illite-chlorite particles offers the ideal conditions for hydrogen sorption. We demonstrate that 4 to 17% of H2 produced by water radiolysis over the 1.4-Ga-lifetime of the Cigar Lake uranium ore deposit has been trapped in the surrounding clay alteration haloes. As a result, sorption processes on layered silicates must not be overlooked as they may exert an important control on the fate and mobility of H2 in the crust. Furthermore, the high capacity of clay minerals to sorb molecular

Recovery of acidified mountain lakes in Norway as predicted by the MAGIC model

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Bernard J. COSBY

2004-02-01

Full Text Available As part of the EU project EMERGE the biogeochemical model MAGIC was used to reconstruct acidification history and predict future recovery for mountain lakes in two regions of Norway. Central Norway (19 lakes receives low levels of acid deposition, most of the lakes have undergone only minor amounts of acidification, and all are predicted to recover in the future. Central Norway thus represents a reference area for more polluted regions in southern Norway and elsewhere in Europe. Southern Norway (23 lakes, on the other hand, receives higher levels of acid deposition, nearly all the studied lakes were acidified and had lost fish populations, and although some recovery has occurred during the period 1980-2000 and additional recovery is predicted for the next decades, the model simulations indicated that the majority of the lakes will not achieve water quality sufficient to support trout populations. Uncertainties in these predictions include possible future N saturation and the exacerbating effects of climate change. The mountain lakes of southern Norway are among the most sensitive in Europe. For southern Norway additional measures such as stricter controls of emissions of air pollutants will be required to obtain satisfactory water quality in the future.

Topographic and depositional signature of old anthropic lakes in northern part of the Moldavian Plateau (NE Romania)

Science.gov (United States)

Ciprian Margarint, Mihai; Niculita, Mihai; Nemeth, Alexandra; Cristea, Ionut

2017-04-01

The role of humans and theirs social activities in reshaping earth surface is obvious in many places of the world. Anthropic fingerprints on Earth's surface morphology are recognizable by theirs topographic and depositional signatures that can cause considerable changes in geomorphological organization of the landscape, with direct consequences on Earth surface processes. Anthropic dams and their associated sediments represent recent archives that record environmental changes. They can provide substantial data to reconstruct general models in geomorphic evolution of hydrologic catchments and the identification of extreme meteorological events and sediment fluxes. Also, geochemical tracers provide us relevant indicators about climatic patterns and local condition of sedimentation processes. Until quite recently, the identification and counting the old lakes have been carried out mostly by studying different old maps and less by analyzing their fingerprints on the Earth surface. Considered a real revolution in geomorphology, the high-resolution LiDAR data allow us nowadays a more precise recognition of minor landforms, their extent and cross-relationships, as well as to discover surface features that have escaped the attention before. Furthermore, by using Electrical Resistivity Tomography techniques, the 3D extension of the sediments can be revealed. Anthropic lakes are one of the most particular hydrological anthropic features of the landscape in the northern part of the Moldavian Plateau (Eastern Carpathian lowland). The need for water supply, have forced the inhabitants to build dams of various sizes along the entire river network. Over the time, many dams were abandoned, while others have been relocated with an impressive dynamic at historical time scale. For more than 3000 sq km we have carried out an accurate inventory of abandoned dams using LIDAR imagery. Taking into consideration the last appearance of the lakes on the old maps, they were classified: pre

Sensitivity to acidification of subalpine ponds and lakes in north-western Colorado

Science.gov (United States)

Campbell, D.H.; Muths, E.; Turk, J.T.; Corn, P.S.

2004-01-01

Although acidifying deposition in western North America is lower than in many parts of the world, many high-elevation ecosystems there are extremely sensitive to acidification. Previous studies determined that the Mount Zirkel Wilderness Area (MZWA) has the most acidic snowpack and aquatic ecosystems that are among the most sensitive in the region. In this study, spatial and temporal variability of ponds and lakes in and near the MZWA were examined to determine their sensitivity to acidification and the effects of acidic deposition during and after snowmelt. Within the areas identified as sensitive to acidification based on bedrock types, there was substantial variability in acid-neutralizing capacity (ANC), which was related to differences in hydrological flowpaths that control delivery of weathering products to surface waters. Geological and topographic maps were of limited use in predicting acid sensitivity because their spatial resolution was not fine enough to capture the variability of these attributes for lakes and ponds with small catchment areas. Many of the lakes are sensitive to acidification (summer and autumn ANC pH value was 5·4, and pH generally remained less than 6·0 throughout early summer in the most sensitive ponds, indicating that biological effects of acidification are possible at levels of atmospheric deposition that occurred during the study. The aquatic chemistry of lakes was dominated by atmospheric deposition and biogeochemical processes in soils and shallow ground water, whereas the aquatic chemistry of ponds was also affected by organic acids and biogeochemical processes in the water column and at the sediment–water interface. These results indicate that conceptual and mechanistic acidification models that have been developed for lakes and streams may be inadequate for predicting acidification in less-understood systems such as ponds.

Environmental restoration of uranium mines in Canada: Progress over 52 years

International Nuclear Information System (INIS)

Feasby, D.G.

1997-01-01

In Canada, the technology for disposal of uranium mine wastes and reclamation of mines has evolved over a period of 52 years. Early practice involved dumping untreated wastes into the nearest depression or lake and leaving rock and infrastructure in place. Now, the practice is to deposit chemically-stabilized tailings, waste rock and building rubble into highly engineered waste management facilities or mine openings. Similarly the ''footprint'' of the mining activity has been reduced to a very small area and the site is restored as-close-as-possible to pre-mining status. This paper describes the evolution of disposal and reclamation methods and the criteria which have determined the development path followed. Remediation techniques to bring older and now unacceptable tailings deposits into satisfactory compliance with current regulations are reviewed. Some monitoring results are presented. All of the uranium mines in Elliot Lake, Ontario, a large uranium producer since 1957, are now permanently closed. Considerable progress has been made on decommissioning the tailings areas by developing long term maintenance of water covers on some, and water treatment plants and stable soil covers on the others. The innovative methods being used to develop the water covers are described, along with the challenges remaining. Methods now under development in Saskatchewan for subaqueous deposition of paste tailings for permanent disposal in mined out open pits are also described. This method will provide for the first time, ''walkaway'', meaning no long term monitoring and maintenance will be required

Timing of lake-level changes for a deep last-glacial Lake Missoula: optical dating of the Garden Gulch area, Montana, USA

DEFF Research Database (Denmark)

Smith, Larry N.; Sohbati, Reza; Buylaert, Jan-Pieter

2018-01-01

Glaciolacustrine sediments in the Clark Fork River valley at Garden Gulch, near Drummond, Montana, USA record highstand positions of the ice-dammed glacial Lake Missoula and repeated subaerial exposure. During these highstands the lake was at greater than 65% of its recognized maximum capacity......-level fluctuation, occurred over time scales of decades to ∼2 ka. Bioturbated sandy slopewash dated at 10.6 ± 0.9 ka and 11.9 ± 1.2 ka unconformably overlies the upper glaciolacustrine deposits. The uppermost sediments, above the glaciolacustrine section, are younger than the Glacier Peak tephra (13.7-13.4 cal ka B...... the lake's highstand position due to ice-dam failure likely led to scour in the downstream portions of the glacial Lake Missoula basin and megafloods in the Channeled Scabland....

Modern processes of palynomorph deposition at lakes of the northern region of the Rio de Janeiro State, Brazil

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Cynthia F.P. da Luz

2010-09-01

Full Text Available Palynological analysis of pollen, Pteridophyta spores and algae deposited in the superficial sediments at Lagoa de Cima and Lagoa do Campelo Lakes, located in the north of Rio de Janeiro state, was used to determine the spatial variation of the palynomorphs deposition. A total of 67 pollen types were identified at Lagoa de Cima, with an expressive contribution of regional arboreous taxa, hydrophytes and ruderal plants of the pastureland. The depositional pattern of palynomorphs depends on the fluvial leakage, the proximity of the local sedimentation to the inlet of the Imbé and Urubu Rivers and the bathymetry of lake bottom. The highest concentrations of palynomorphs were observed in the decentralized and less deeper area, without the interference of the northeastern wind. At Lagoa do Campelo, a total of 58 pollen types were identified, among which the majority of the pollen grains came from hydrophytes, with the highest concentrations found along the northeastern shore. The southeastern shore showed high percentages of pollen and spores with degraded exine and mechanical damage, due to the transport through the lakeby the currents caused by the wind, confirmed by the depositional trend of damaged palinomorphs along the same direction as the prevailing winds.A análise palinológica de grãos de pólen, esporos de Pteridophyta e algas depositados nos sedimentos superficiais da Lagoa de Cima e Lagoa do Campelo, norte do Rio de Janeiro, foi usada para a avaliação da variação espacial de deposição dos palinomorfos. Um total de 67 tipos polínicos foi identificado na Lagoa de Cima, com expressiva contribuição de taxons arbóreos regionais, plantas hidrófitas e ruderais de pastagens. O padrão deposicional dos palinomorfos está sujeito às vazões fluviais, à proximidade do local de sedimentação em relação à desembocadura dos rios Imbé e Urubu e à batimetria do leito da lagoa. As maiores concentrações de palinomorfos foram

Sources and deposition of polycyclic aromatic hydrocarbons to western US national parks

Science.gov (United States)

Seasonal snowpack, lichens, and lake sediment cores were collected from fourteen lake catchments in eight western U.S. National Parks and analyzed for sixteen polycyclic aromatic hydrocarbons (PAHs) to determine their current and historical deposition, as well as to identify thei...

Some metallogenic features of the Huronian and post-Huronian uraniferous conglomerates

International Nuclear Information System (INIS)

Ruzicka, V.

1981-01-01

Uraniferous conglomerates with syngenetic mineralization are restricted to lower Proterozoic sediments. The depositional environment was near volcanic centres; excessive sulfur, a product a volcanic and postvolcanic activity, apparently caused sulfurization of some minerals and of hydrocarbon. The sedimentary syngenetic origin of uranium mineralization may be illustrated. The cycle starts with deposition of coarse grains of quartz, continues with the deposition of a mixture of finer grains of quartz and pyrite with distinct graded bedding, is followed by deposition of monazite and brannerite, and ends with deposition of fragmented fine grains of uraninite embedded in sulfur-rich hydrocarbon. This situation apparently testifies to the fact that the carbonaceous material is a product of algal mats that existed in quiet times between cycles of sedimentation. The succeeding cycle again starts with the deposition of coarse grains of quartz. Uraniferous conglomerates with epigenetic mineralization are localized in regions containing rocks with higher contents of uranium. Primary concentration of uranium minerals in these source rocks can also be syngenetic. Deposition of uranium took place by one or more epigenetic processes: adsorption, complexing, precipitation, or redox changes according to the degrees of solubility and stability of uranium compounds. Evidence of these mentioned features is based upon studies on the Huronian uraniferous conglomerate from Elliot Lake, Canada, and on the late Precambrian and Paleozoic radioactive conglomerates from the eastern Ural Mountains and Enisey Crest region, USSR

Suspended-sediment budget, flow distribution, and lake circulation for the Fox Chain of Lakes in Lake and McHenry Counties, Illinois, 1997-99

Science.gov (United States)

Schrader, David L.; Holmes, Robert R.

2000-01-01

The Fox Chain of Lakes is a glacial lake system in McHenry and Lake Counties in northern Illinois and southern Wisconsin. Sedimentation and nutrient overloading have occurred in the lake system since the first dam was built (1907) in McHenry to raise water levels in the lake system. Using data collected from December 1, 1997, to June 1, 1999, suspended-sediment budgets were constructed for the most upstream lake in the system, Grass Lake, and for the lakes downstream from Grass Lake. A total of 64,900 tons of suspended sediment entered Grass Lake during the study, whereas a total of 70,600 tons of suspended sediment exited the lake, indicating a net scour of 5,700 tons of sediment. A total of 44,100 tons of suspended sediment was measured exiting the Fox Chain of Lakes at Johnsburg, whereas 85,600 tons entered the system downstream from Grass Lake. These suspended-sediment loads indicate a net deposition of 41,500 tons downstream from Grass Lake, which represents a trapping efficiency of 48.5 percent. A large amount of recreational boating takes place on the Fox Chain of Lakes during summer months, and suspended-sediment load was observed to rise from 110 tons per day to 339 tons per day during the 1999 Memorial Day weekend (May 26 ?31, 1999). Presumably, this rise was the result of the boating traffic because no other hydrologic event is known to have occurred that might have caused the rise. This study covers a relatively short period and may not represent the long-term processes of the Fox Chain of Lakes system, although the sediment transport was probably higher than an average year. The bed sediments found on the bottom of the lakes are composed of mainly fine particles in the silt-clay range. The Grass Lake sediments were characterized as black peat with an organic content of between 9 and 18 percent, and the median particle size ranged from 0.000811 to 0.0013976 inches. Other bed material samples were collected at streamflow-gaging stations on the

Early and late Holocene glacial fluctuations and tephrostratigraphy, Cabin Lake, Alaska

Science.gov (United States)

Zander, Paul D.; Kaufman, Darrell S.; Kuehn, Stephen C.; Wallace, Kristi L.; Anderson, R. Scott

2013-01-01

Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non-glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier-than-present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid-Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.

Effects of the exotic zebra mussel (Dreissena polymorpha) on metal cycling in Lake Erie

International Nuclear Information System (INIS)

Klerks, P.L.; Fraleigh, P.C.; Lawniczak, J.E.

1997-01-01

This research demonstrated the impact of high densities of the zebra mussel (Dreissena polymorpha) on the cycling of copper, nickel, and zinc in a lake environment. Experiments with mussels on sedimentation traps in western Lake Erie and with mussels in flow-through tanks receiving Lake Erie water showed that zebra mussels remove metals from the water column, incorporate metals in their tissues, and deposit metals on the lake bottom. Removal of metals from the water column was estimated at 10-17%·day -1 of the amounts present. This material was largely deposited on the lake bottom; zebra mussels more than doubled the rate at which metals were being added to the lake bottom. Metal biodeposition rates were extremely high (e.g., 50 mg Zn·m -2 ·day -1 ) in high-turbidity areas with elevated metal levels. Two factors contributed to metal biodeposition by zebra mussels. First, their production of feces and pseudofeces increased the rate at which suspended matter was being added to the sediment (accounting for 92% of the increased metal biodeposition). Second, the material coming out of suspension had higher metal concentrations when zebra mussels were present (constituting 8% of the increased biodeposition). (author)

Factors Affecting Mercury Stable Isotopic Distribution in Piscivorous Fish of the Laurentian Great Lakes.

Science.gov (United States)

Lepak, Ryan F; Janssen, Sarah E; Yin, Runsheng; Krabbenhoft, David P; Ogorek, Jacob M; DeWild, John F; Tate, Michael T; Holsen, Thomas M; Hurley, James P

2018-03-06

Identifying the sources of methylmercury (MeHg) and tracing the transformations of mercury (Hg) in the aquatic food web are important components of effective strategies for managing current and legacy Hg sources. In our previous work, we measured stable isotopes of Hg (δ 202 Hg, Δ 199 Hg, and Δ 200 Hg) in the Laurentian Great Lakes and estimated source contributions of Hg to bottom sediment. Here, we identify isotopically distinct Hg signatures for Great Lakes trout ( Salvelinus namaycush) and walleye ( Sander vitreus), driven by both food-web and water-quality characteristics. Fish contain high values for odd-isotope mass independent fractionation (MIF) with averages ranging from 2.50 (western Lake Erie) to 6.18‰ (Lake Superior) in Δ 199 Hg. The large range in odd-MIF reflects variability in the depth of the euphotic zone, where Hg is most likely incorporated into the food web. Even-isotope MIF (Δ 200 Hg), a potential tracer for Hg from precipitation, appears both disconnected from lake sedimentary sources and comparable in fish among the five lakes. We suggest that similar to the open ocean, water-column methylation also occurs in the Great Lakes, possibly transforming recently deposited atmospheric Hg deposition. We conclude that the degree of photochemical processing of Hg is controlled by phytoplankton uptake rather than by dissolved organic carbon quantity among lakes.

Unexpected stasis in a changing world: Lake nutrient and chlorophyll trends since 1990

Science.gov (United States)

Oliver, Samantha K.; Collins, Sarah M.; Soranno, Patricia A.; Wagner, Tyler; Stanley, Emily H.; Jones, John R.; Stow, Craig A.; Lottig, Noah R.

2017-01-01

The United States (U.S.) has faced major environmental changes in recent decades, including agricultural intensification and urban expansion, as well as changes in atmospheric deposition and climate—all of which may influence eutrophication of freshwaters. However, it is unclear whether or how water quality in lakes across diverse ecological settings has responded to environmental change. We quantified water quality trends in 2913 lakes using nutrient and chlorophyll (Chl) observations from the Lake Multi-Scaled Geospatial and Temporal Database of the Northeast U.S. (LAGOS-NE), a collection of preexisting lake data mostly from state agencies. LAGOS-NE was used to quantify whether lake water quality has changed from 1990 to 2013, and whether lake-specific or regional geophysical factors were related to the observed changes. We modeled change through time using hierarchical linear models for total nitrogen (TN), total phosphorus (TP), stoichiometry (TN:TP), and Chl. Both the slopes (percent change per year) and intercepts (value in 1990) were allowed to vary by lake and region. Across all lakes, TN declined at a rate of 1.1% year−1, while TP, TN:TP, and Chl did not change. A minority (7%–16%) of individual lakes had changing nutrients, stoichiometry, or Chl. Of those lakes that changed, we found differences in the geospatial variables that were most related to the observed change in the response variables. For example, TN and TN:TP trends were related to region-level drivers associated with atmospheric deposition of N; TP trends were related to both lake and region-level drivers associated with climate and land use; and Chl trends were found in regions with high air temperature at the beginning of the study period. We conclude that despite large environmental change and management efforts over recent decades, water quality of lakes in the Midwest and Northeast U.S. has not overwhelmingly degraded or improved.

The Geologic History of Lake of the Woods, Minnesota, Reconstructed Using Seismic-Reflection Imaging and Sediment Core Analysis

Science.gov (United States)

Hougardy, Devin D.

The history of glacial Lake Agassiz is complex and has intrigued researchers for over a century. Over the course of its ˜5,000 year existence, the size, shape, and location of Lake Agassiz changed dramatically depending on the location of the southern margin of the Laurentide Ice Sheet (LIS), the location and elevation of outflow channels, and differential isostatic rebound. Some of the best-preserved sequences of Lake Agassiz sediments are found in remnant lake basins where erosional processes are less pronounced than in adjacent higher-elevation regions. Lake of the Woods (LOTW), Minnesota, is among the largest of the Lake Agassiz remnant lakes and is an ideal location for Lake Agassiz sediment accumulation. High-resolution seismic-reflection (CHIRP) data collected from the southern basin of LOTW reveal up to 28 m of stratified lacustrine sediment deposited on top of glacial diamicton and bedrock. Five seismic units (SU A-E) were identified and described based on their reflection character, reflection configuration, and external geometries. Three prominent erosional unconformities (UNCF 1-3) underlie the upper three seismic units and indicate that deposition at LOTW was interrupted by a series of relatively large fluctuations in lake level. The lowermost unconformity (UNCF-1) truncates uniformly draped reflections within SU-B at the margins of the basin, where as much as four meters of sediment were eroded. The drop in lake level is interpreted to be contemporaneous with the onset of the low-stand Moorhead phase of Lake Agassiz identified from subaerial deposits in the Red River Valley, Rainy River basin, and Lake Winnipeg. A rise in lake level, indicated by onlapping reflections within SU-C onto UNCF-1, shifted the wave base outwards and as much as 11 m of sediment were deposited (SU-C) in the middle of the basin before a second drop, and subsequent rise, in lake level resulted in the formation of UNCF-2. Reflections in the lower part of SU-D onlap onto UNCF-2

Isotopic composition of dissolved inorganic nitrogen in high mountain lakes: variation with altitude in the Pyrenees

Science.gov (United States)

Bartrons, M.; Camarero, L.; Catalan, J.

2010-05-01

Nitrogen deposition in remote areas has increased, but the effect on ecosystems is still poorly understood. For aquatic systems, knowledge of the main processes driving the observed variation is limited, as is knowledge of how changes in nitrogen supply affect lake biogeochemical and food web processes. Differences in dissolved inorganic nitrogen (DIN) between lakes cannot be understood without considering catchment characteristics. In mountains, catchment features (e.g., thermal conditions, land cover) vary considerably with elevation. The isotopic composition of nitrogen (δ15N) is increasingly used to study aquatic ecosystem dynamics. Here we explore the variability of δ15N in DIN in high mountain lakes and show that environmental conditions that change with altitude can affect the isotopic ratio. We measured ammonium and nitrate δ15N values in atmospheric deposition, epilimnetic water, deep chlorophyll maximum water (DCMW) and sediment pore water (SPW) from eight mountain lakes in the Pyrenees, both above and below the treeline. Lakes showed relatively uniform δ15N-NH4+ values in SPW (2.2±1.6‰), with no variation corresponding to catchment or lake characteristics. We suggest that organic matter diagenesis under similar sediment conditions is responsible for the low variation between the lakes. In the water column, the range of δ15N values was larger for ammonium (-9.4‰ to 7.4‰) than for nitrate (-11.4‰ to -3.4‰), as a result of higher variation both between and within lakes (epilimnetic vs. DCM water). For both compounds part of the difference correlated with altitude or catchment features (e.g., scree proportion). Based on concentration, chemical and isotopic tendencies, we suggest that patterns arise from the distinct relative contributions of two types of water flow paths to the lakes: one from snowpack melting, with little soil interaction; and another highly influenced by soil conditions. The snow-type flow path contributes low DIN

Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

Science.gov (United States)

Dijkstra, Nikki; Hagens, Mathilde; Egger, Matthias; Slomp, Caroline P.

2018-02-01

Phosphorus (P) concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an iron(II)-phosphate mineral, might significantly alter trends in P with sediment depth. To assess its importance, we investigate a sediment record from the Bornholm Basin that was retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013, consisting of lake sediments overlain by brackish-marine deposits. Combining bulk sediment geochemistry with microanalysis using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and synchrotron-based X-ray absorption spectroscopy (XAS), we demonstrate that vivianite-type minerals rich in manganese and magnesium are present in the lake deposits just below the transition to the brackish-marine sediments (at 11.5 to 12 m sediment depth). In this depth interval, phosphate that diffuses down from the organic-rich, brackish-marine sediments meets porewaters rich in dissolved iron in the lake sediments, resulting in the precipitation of iron(II) phosphate. Results from a reactive transport model suggest that the peak in iron(II) phosphate originally occurred at the lake-marine transition (9 to 10 m) and moved downwards due to changes in the depth of a sulfidization front. However, its current position relative to the lake-marine transition is stable as the vivianite-type minerals and active sulfidization fronts have been spatially separated over time. Experiments in which vivianite was subjected to sulfidic conditions demonstrate that incorporation of manganese or magnesium in vivianite does not affect its susceptibility to sulfide-induced dissolution. Our work highlights that post-depositional formation of iron(II) phosphates such as vivianite has the potential to strongly

Profundal sideritic mudstone from an Eocene lake in Alaska

International Nuclear Information System (INIS)

Dickinson, K.A.

1987-01-01

Sideritic lacustrine mudstone was found in drill core from a uranium deposit in the Death Valley area in the eastern part of the Seward Peninsula, Alaska. The precursor sediments for this rock were deposited in an unusual iron-meromictic Eocene lake, herein named Lake Tubutulik, which occupied part of the Boulder Creek basin, a graben that is probably a southern extension of the larger Death Valley basin. The Boulder Creek basin is bounded on the west by granite of the Upper Cretaceous Darby pluton and on the east by Precambrian to Paleozoic metasedimentary rocks. The lake basin was formed by basaltic flows that dammed the valley of the ancestral Tubutulik River in early Eocene time. The lake sediments included a nearshore facies of fine-grained organic mud and an offshore facies of laminated sideritic mud. The offshore (profundal) laminated mudstone consists of alternating layers of authigenic siderite and detrital grains, mostly quartz and clay minerals. Both lacustrine facies contain turbidites. The lacustrine rocks graded laterally into an onshore facies of colluvial and fluvial sandstone, paludal mudstone, and coal. The ancient lake occupied a small, deep basin in a tectonically active area of high relief. Meromixis was apparently stabilized by reduced iron and bicarbonate dissolved in the monimolimnion. The intensity of meromixis decreased as the lake became shallower from sediment filling. The source of the dissolved iron in the monoimolimnion was probably the Eocene basalt. Carbon isotope analysis of the siderite suggests that the dissolved bicarbonate in the profundal facies was largely inorganic. Sideritic carbon in one sample from the onshore paludal facies has an isotopic signature (δ 13 C = +16.9) consistent with residual carbonate formed during methanogenic fermentation

MERGANSER - An Empirical Model to Predict Fish and Loon Mercury in New England Lakes

Science.gov (United States)

MERGANSER (MERcury Geo-spatial AssessmeNtS for the New England Region) is an empirical least-squares multiple regression model using mercury (Hg) deposition and readily obtainable lake and watershed features to predict fish (fillet) and common loon (blood) Hg in New England lakes...

Isotopic fingerprints of anthropogenic molybdenum in lake sediments.

Science.gov (United States)

Chappaz, Anthony; Lyons, Timothy W; Gordon, Gwyneth W; Anbar, Ariel D

2012-10-16

We measured the molybdenum isotope compositions (δ(98)Mo) of well-dated sediment cores from two lakes in eastern Canada in an effort to distinguish between natural and anthropogenic contributions to these freshwater aquatic systems. Previously, Chappaz et al. (1) ascribed pronounced 20th-century Mo concentration enrichments in these lakes to anthropogenic inputs. δ(98)Mo values in the deeper sediments (reflecting predominantly natural Mo sources) differ dramatically between the two lakes: -0.32 ± 0.17‰ for oxic Lake Tantare and +0.64 ± 0.09‰ for anoxic Lake Vose. Sediment layers previously identified as enriched in anthropogenic Mo, however, reveal significant δ(98)Mo shifts of ± 0.3‰, resulting in isotopically heavier values of +0.05 ± 0.18‰ in Lake Tantare and lighter values of +0.31 ± 0.03‰ in Lake Vose. We argue that anthropogenic Mo modifies the isotopic composition of the recent sediments, and we determine δ(98)Mo(anthropogenic) values of 0.1 ± 0.1‰ (Lake Vose) and 0.2 ± 0.2‰ (Lake Tantare). These calculated inputs are consistent with the δ(98)Mo of molybdenite (MoS(2)) likely delivered to the lakes via smelting of porphyry copper deposits (Lake Vose) or through combustion of coal and oil also containing Mo (Lake Tantare). Our results confirm the utility of Mo isotopes as a promising fingerprint of human impacts and perhaps the specific sources of contamination. Importantly, the magnitudes of the anthropogenic inputs are large enough, relative to the natural Mo cycles in each lake, to have an impact on the microbiological communities.

Final report of the AECL/SKB Cigar Lake analog study

International Nuclear Information System (INIS)

Cramer, J.

1994-05-01

The Cigar Lake uranium deposit is located in northern Saskatchewan, Canada. The 1.3-billion-year-old deposit is located at a depth of about 450 m below surface in a water-saturated sandstone at the unconformity contact with the high-grade metamorphic rocks of the Canadian Shield. The Cigar Lake deposit has many features that parallel those being considered within the Canadian concept for disposal of nuclear fuel waste. The study of these natural structures and processes provides valuable insight toward the eventual design and site selection of a nuclear fuel waste repository. The main feature of this analog is the absence of any indication on the surface of the rich uranium ore 450 m below. This indicates that the combination of natural barriers has been effective in isolating the uranium ore from the surface environment. More specifically, the deposit provides analog information relevant to the stability of UO 2 fuel waste, the performance of clay-based barriers, radionuclide migration, colloid formation, radiolysis, fission-product geochemistry and general aspects of water-rock interaction. The main geochemical studies on this deposit focus on the evolution of groundwater compositions in the deposit and on their redox chemistry with respect to the uranium, iron and sulphide systems. Since 1984, through cooperation from the owners of the Cigar Lake deposit, analog studies have been conducted. AECL, with support from Ontario Hydro under the auspices of the CANDU Owners Group, initiated international participation in 1989 through collaboration with the Swedish Nuclear Fuel and Waste Management Company (SKB) and, more recently, with the Los Alamos National Laboratory (LANL). This report gives the results of the various studies carried out during the 3-year collaboration between AECL and SKB, as well as a summery of the LANL study. It provides detailed information on the generated databases and models, and integrates this information into conclusions for use in safety

Estimating Spring Condensation on the Great Lakes

Science.gov (United States)

Meyer, A.; Welp, L.

2017-12-01

The Laurentian Great Lakes region provides opportunities for shipping, recreation, and consumptive water use to a large part of the United States and Canada. Water levels in the lakes fluctuate yearly, but attempts to model the system are inadequate because the water and energy budgets are still not fully understood. For example, water levels in the Great Lakes experienced a 15-year low period ending in 2013, the recovery of which has been attributed partially to decreased evaporation and increased precipitation and runoff. Unlike precipitation, the exchange of water vapor between the lake and the atmosphere through evaporation or condensation is difficult to measure directly. However, estimates have been constructed using off-shore eddy covariance direct measurements of latent heat fluxes, remote sensing observations, and a small network of monitoring buoys. When the lake surface temperature is colder than air temperature as it is in spring, condensation is larger than evaporation. This is a relatively small component of the net annual water budget of the lakes, but the total amount of condensation may be important for seasonal energy fluxes and atmospheric deposition of pollutants and nutrients to the lakes. Seasonal energy fluxes determine, and are influenced by, ice cover, water and air temperatures, and evaporation in the Great Lakes. We aim to quantify the amount of spring condensation on the Great Lakes using the National Center for Atmospheric Prediction North American Regional Reanalysis (NCEP NARR) Data for Winter 2013 to Spring 2017 and compare the condensation values of spring seasons following high volume, high duration and low volume, low duration ice cover.

Dynamics of floodplain lakes in the Upper Amazon Basin during the late Holocene

Science.gov (United States)

Quintana-Cobo, Isabel; Moreira-Turcq, Patricia; Cordeiro, Renato C.; Aniceto, Keila; Crave, Alain; Fraizy, Pascal; Moreira, Luciane S.; Duarte Contrera, Julia Maria de Aguiar; Turcq, Bruno

2018-01-01

To better understand the impact of channel migration processes and climate change on the depositional dynamics of floodplain lakes of the upper Amazon Basin during the late Holocene, we collected three sediment cores from floodplain lakes of the Ucayali River and one from the Marañón River. The cores were dated with 14C, radiographed and described. Bulk density, grain size analysis and total organic carbon (TOC) were determined. The results show that sedimentation in Ucayali floodplain lakes was marked by variations during the late Holocene, with periods of intense hydrodynamic energy and abrupt accumulations, a gap in the record between about 2870 and 690 cal yr BP, and periods of more lacustrine conditions. These changes in sedimentation were associated with variations in the river's influence related to changes in its meandering course (2870 cal yr BP) and a period of severe flooding between 3550 and 3000 cal yr BP. Lake Lagarto on the Marañón River floodplain exhibits a different sedimentary environment of low hydrodynamics with palm trees and macrophytes. Apparently, the lake has not experienced intense migration processes during the last 600 cal yr BP (base of the core). Nevertheless, the river sediment flux to the lake was important from 600 to 500 cal yr BP, although it decreased thereafter until the present. This decrease in the mineral accumulation rate indicates a decrease in river discharge since 500 cal yr BP, which coincides with precipitation records from the central Andes. In the upper part of the three Ucayali floodplain cores, a 30- to 250-cm-thick layer of reworked sediments has been deposited since 1950 AD (post-bomb). In Lake Carmen, this layer is associated with invasion of the lake by the levee of a migrating meander of the Ucayali. In Lakes Hubos and La Moringa, however, the river is still far away and the deposition must be interpreted as the result of extreme flooding. The beginning of the Ucayali meander migration is dated back to

Mercury pollution in the lake sediments and catchment soils of anthropogenically-disturbed sites across England.

Science.gov (United States)

Yang, Handong; Turner, Simon; Rose, Neil L

2016-12-01

Sediment cores and soil samples were taken from nine lakes and their catchments across England with varying degrees of direct human disturbance. Mercury (Hg) analysis demonstrated a range of impacts, many from local sources, resulting from differing historical and contemporary site usage and management. Lakes located in industrially important areas showed clear evidence for early Hg pollution with concentrations in sediments reaching 400-1600 ng g -1 prior to the mid-19th century. Control of inputs resulting from local management practices and a greater than 90% reduction in UK Hg emissions since 1970 were reflected by reduced Hg pollution in some lakes. However, having been a sink for Hg deposition for centuries, polluted catchment soils are now the major Hg source for most lakes and consequently recovery from reduced Hg deposition is being delayed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Source of Lake Vostok Cations Constrained with Strontium Isotopes

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William Berry Lyons

2016-08-01

Full Text Available Lake Vostok is the largest sub-glacial lake in Antarctica. The primary source of our current knowledge regarding the geochemistry and biology of the lake comes from the analysis of refrozen lake water associated with ice core drilling. Several sources of dissolved ions and particulate matter to the lake have been proposed, including materials from the melted glacier ice, the weathering of underlying geological materials, hydrothermal activity and underlying, ancient evaporitic deposits. A sample of Lake Vostok Type 1 accretion ice has been analyzed for its 87Sr/86Sr signature as well as its major cation and anion and Sr concentrations. The strontium isotope ratio of 0.71655 and the Ca/Sr ratio in the sample strongly indicate that the major source of the Sr is from aluminosilicate minerals from the continental crust. These data imply that at least a portion of the other cations in the Type 1 ice also are derived from continental crustal materials and not hydrothermal activity, the melted glacier ice, or evaporitic sources.

The paleolimnological development of the twin lakes Etujärvi and Takajärvi in Askola, southern Finland – implications for lake management

Directory of Open Access Journals (Sweden)

Samu E. Valpola

2006-01-01

Full Text Available The twin lakes Etujärvi and Takajärvi in Askola, southern Finland, are closely interconnected mesotrophic headwater lakes with a relatively small catchment area. Both of the lakes have suffered from eutrophication and its consequences. Remediation activities such as oxygenation and biomanipulation have not resolved the problems. In this study a large set of paleolimnological techniques (radiometric AMS dating, spherical carbonaceous particles analysis, sediment lithology, grain-size analysis, phosphorus fractionation, and diatom analysis were applied to put together the development of the basin and its water level fluctuations during the Holocene. The age for observed Trapa natans -horizons was determined, and lake management options were discussed. The studied lakes dried up after isolation from the Ancylus Lake at about 9500 cal. B.P. and remained at very low water level until ca. 8700–8500 cal. B.P. The mid-Holocene risein water level resulted in fluctuating water levels, and led to the most recent rise starting about 2500 cal. B.P. as wet and cool climate conditions prevailed. The pronounced water level fluctuations led to the extensive growth of peat deposits surrounding the lake andprobably also forced T. natans to disappear from lake flora. The unstable, erodable peat rims impact the lakes, causing heavy load of humic substances to the lake and presenting additional deterioration to their recreational value.

Synthetic musk fragrances in Lake Michigan.

Science.gov (United States)

Peck, Aaron M; Hornbuckle, Keri C

2004-01-15

Synthetic musk fragrances are added to a wide variety of personal care and household products and are present in treated wastewater effluent. Here we report for the first time ambient air and water measurements of six polycyclic musks (AHTN, HHCB, ATII, ADBI, AHMI, and DPMI) and two nitro musks (musk xylene and musk ketone) in North America. The compounds were measured in the air and water of Lake Michigan and in the air of urban Milwaukee, WI. All of the compounds except DPMI were detected. HHCB and AHTN were found in the highest concentrations in all samples. Airborne concentrations of HHCB and AHTN average 4.6 and 2.9 ng/m3, respectively, in Milwaukee and 1.1 and 0.49 ng/m3 over the lake. The average water concentration of HHCB and AHTN in Lake Michigan was 4.7 and 1.0 ng/L, respectively. A lake-wide annual mass budget shows that wastewater treatment plant discharge is the major source (3470 kg/yr) of the synthetic musks while atmospheric deposition contributes less than 1%. Volatilization and outflow through the Straits of Mackinac are major loss mechanisms (2085 and 516 kg/yr for volatilization and outflow, respectively). Concentrations of HHCB are about one-half the predicted steady-state water concentrations in Lake Michigan.

Organic carbon accumulation and reactivity in central Swedish lakes during the Holocene

Science.gov (United States)

Chmiel, H.; Kokic, J.; Niggemann, J.; Dittmar, T.; Sobek, S.

2012-04-01

Sedimentation and burial of particulate organic carbon (POC), received from terrestrial sources and from lake internal primary production, are responsible for the progressive accumulation and long-term storage of organic matter in lake basins. For lakes in the boreal zone of central Sweden it can be presumed, that the onset of POC accumulation occurred during the early Holocene (˜8000 BP.) after the retreat of the Scandinavian ice sheet. In this study we investigated carbon mass accumulation rates (CMARs), as well as sources and reactivity of deposited organic material, for seven lakes in central Sweden (60°N, 15°E), in order to obtain a detailed temporal resolution of carbon burial and preservation in boreal lakes. Sediment long-cores were sampled in March 2011 from the ice, and CMARs were calculated from water contents, dry bulk densities, carbon contents and radiocarbon (14C) ages of the depth profiles. To indicate the sources of the organic material and characterize its diagenetic state, we determined carbon-nitrogen ratios (C/N) as well as amounts and compositions of lignin phenols. The transitions from organic rich sediment layers to glacial till deposits were found to be in sediment depths of ˜3 m in each lake. POC contents were on average highest (25-34 wt. % C), in small lakes (≤ 0.07 km2) and lowest (10-18 wt. % C) in the larger lakes (≥ 165 km2). The CMARs over the Holocene showed significant variations and were on average lower in the early Holocene, compared to recent accumulation rates. C/N values and the composition of lignin phenols further provided indications of important changes in organic matter source and reactivity over the Holocene. In summary, our data suggest that boreal lake sediments were a significantly stronger sink for organic carbon during the last ~150 years than during earlier periods of the Holocene.

Ecosystem evolution of Lake Gusinoe (Transbaikal region, Russia)

Energy Technology Data Exchange (ETDEWEB)

Pisarsky, B.L.; Hardina, A.M.; Naganawa, H. [Russian Academy of Science, Irkutsk (Russian Federation). Siberian Division

2005-12-01

Lake Gusinoe is situated on a basin originating from Paleozoic and Mesozoic deposits. The recorded history of the lake's ecosystem evolution is no more than 300 years. The present lake drainage basin was formed mainly in the Cenozoic era, but during the past century, major anthropogenic impacts on the lake have occurred. The human-influenced evolution of the ecosystem began in the 1940s with the development of opencut coal mining nearby the lake. Population increase and the building of the Gusinoozersk State Regional Power Plant, the TransMongolian Railroad and an associated station, and military installations were the major sources of anthropogenic impacts. Since the early 1950s about five species of fish have been introduced into Lake Gusinoe or have invaded the lake, and at least six of the native species have disappeared or are in danger of extinction. From our recent investigations, the present environment of the Lake Gusinoe Basin (Gusinoozersk Basin) is divided into four zones hydro-geochemically: (1) ultrafreshwater, (2) freshwater, (3) mineralized water, and (4) hyposaline and saltwater. Some additional data on changes of the chemical components of the drainage basin waters, as well as on the transition of zooplankton and zoobenthic fauna, are presented in consideration of the risk of industrial development, and the perspectives are discussed.

Refurbished Stanleigh shaft, gives uranium mine new life

International Nuclear Information System (INIS)

Johnson, B.

1982-01-01

In August 1979, work began to dewater the Stanleigh mine of Rio Algom Limited near Elliot Lake, Ontario, which had lain dormant in a flooded state since early-1961. Under terms of an agreement with Ontario Hydro, Rio Algom is well on its way towards reactivating the mine and is scheduled to begin producing yellowcake on July, 1, 1983

Interpretation of some geochemical distributions in Key and Seahorse Lakes, Saskatchewan

Energy Technology Data Exchange (ETDEWEB)

Parslow, G.R.

1979-04-01

U, Fe, Mn, Ni, Cu, Zn and Co data for the sediment in both Key and Seahorse lakes, which overlie portions of known economic uranium deposits in the region, are presented. With the exception of U, Fe and Mn, the elemental distributions can be considered anomalous, in a statistical sense, in both lakes. The U values are of particular interest in that Key Lake is not anomalous, whereas Seahorse Lake is markedly anomalous. Tentative correlations made with background data from other surveys in attempt to differentiate between anomalous and background values indicate that deviations from linearity in a distribution, and not absolute mean or maximum values, are indicative of anomalous samples within the distribution.

Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

Science.gov (United States)

Kite, Edwin S.; Gao, Peter; Goldblatt, Colin; Mischna, Michael A.; Mayer, David P.; Yung, Yuk L.

2017-10-01

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluviolacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds’ little-weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, although inconsistent with many previously proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake-forming climates, if methane clathrate initially occupies more than 4% of the total volume in which it is thermodynamically stable. Such occupancy fractions are consistent with methane production by water-rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars.

Effects of the exotic zebra mussel (Dreissena polymorpha) on metal cycling in Lake Erie

Energy Technology Data Exchange (ETDEWEB)

Klerks, P.L. [Univ. of Southwestern Louisiana, Dept. of Biology, Lafayette, Louisiana (United States)]. E-mail: klerks@usl.edu; Fraleigh, P.C.; Lawniczak, J.E. [Univ. of Toledo, Dept. of Biology, Toledo, Ohio (United States)

1997-07-15

This research demonstrated the impact of high densities of the zebra mussel (Dreissena polymorpha) on the cycling of copper, nickel, and zinc in a lake environment. Experiments with mussels on sedimentation traps in western Lake Erie and with mussels in flow-through tanks receiving Lake Erie water showed that zebra mussels remove metals from the water column, incorporate metals in their tissues, and deposit metals on the lake bottom. Removal of metals from the water column was estimated at 10-17%{center_dot}day{sup -1} of the amounts present. This material was largely deposited on the lake bottom; zebra mussels more than doubled the rate at which metals were being added to the lake bottom. Metal biodeposition rates were extremely high (e.g., 50 mg Zn{center_dot}m{sup -2}{center_dot}day{sup -1}) in high-turbidity areas with elevated metal levels. Two factors contributed to metal biodeposition by zebra mussels. First, their production of feces and pseudofeces increased the rate at which suspended matter was being added to the sediment (accounting for 92% of the increased metal biodeposition). Second, the material coming out of suspension had higher metal concentrations when zebra mussels were present (constituting 8% of the increased biodeposition). (author)

Tsunami-generated sediment wave channels at Lake Tahoe, California-Nevada, USA

Science.gov (United States)

Moore, James G.; Schweickert, Richard A.; Kitts, Christopher A.

2014-01-01

A gigantic ∼12 km3 landslide detached from the west wall of Lake Tahoe (California-Nevada, USA), and slid 15 km east across the lake. The splash, or tsunami, from this landslide eroded Tioga-age moraines dated as 21 ka. Lake-bottom short piston cores recovered sediment as old as 12 ka that did not reach landslide deposits, thereby constraining the landslide age as 21–12 ka.Movement of the landslide splashed copious water onto the countryside and lowered the lake level ∼10 m. The sheets of water that washed back into the lake dumped their sediment load at the lowered shoreline, producing deltas that merged into delta terraces. During rapid growth, these unstable delta terraces collapsed, disaggregated, and fed turbidity currents that generated 15 subaqueous sediment wave channel systems that ring the lake and descend to the lake floor at 500 m depth. Sheets of water commonly more than 2 km wide at the shoreline fed these systems. Channels of the systems contain sediment waves (giant ripple marks) with maximum wavelengths of 400 m. The lower depositional aprons of the system are surfaced by sediment waves with maximum wavelengths of 300 m.A remarkably similar, though smaller, contemporary sediment wave channel system operates at the mouth of the Squamish River in British Columbia. The system is generated by turbidity currents that are fed by repeated growth and collapse of the active river delta. The Tahoe splash-induced backwash was briefly equivalent to more than 15 Squamish Rivers in full flood and would have decimated life in low-lying areas of the Tahoe region.

Historical changes in the ecosystem condition of a small mountain lake over the past 60 years as revealed by plankton remains and Daphnia ephippial carapaces stored in lake sediments.

Directory of Open Access Journals (Sweden)

Hajime Ohtsuki

Full Text Available To examine if changes in species composition of a plankton community in the past due to anthropogenic activities can be clarified in lakes without any monitoring data, we analyzed genetically ephippial carapaces of Daphnia with plankton remains stored in the bottom sediments of Lake Hataya Ohunma in Japan. In the lake, abundance of most plankton remains in the sediments was limited and TP flux was at low levels (2-4 mg/m2/y before 1970. However TP flux increased two-fold during the period from 1980s to 1990 s. In parallel with this increase, abundance of most plankton remains increased although abundance of benthic testate amoebae's remains decreased, indicating that the lake trophic condition had changed from oligo- to mesotrophic for the past 60 years. According to cluster analysis, the stratigraphic sediments were divided into two periods with different features of the phytoplankton composition. Chronological comparison with events in the watershed suggested that eutrophication occurred because of an increase in visitors to the watershed and deposition of atmospheric dust. In this lake more than 50% of resting eggs produced by Daphnia over the past 60 years hatched. However, genetic analysis of the ephippial carapaces (remains showed that the Daphnia population was originally composed of D. dentifera but that D. galeata, or its hybrid with D. dentifera, invaded and increased the population density when the lake was eutrophied. Subsequently, large D. pulex established populations in the 1980s when largemouth bass were anonymously introduced. These results indicated that the Lake Hataya Ohunma plankton community underwent significant changes despite the fact that there were no notable changes in land cover or land use in the watershed. Since increases in atmospheric deposition and release of fish have occurred in many Japanese lakes, the changes in the plankton community described here may be widespread in these lakes.

Uranium in surficial deposits and waters at Palmottu

International Nuclear Information System (INIS)

Ahonen, L.; Blomqvist, R.; Ervanne, H.; Suksi, J.; Jaakkola, T.

1994-01-01

Occurrence of uranium in surficial formations in the vicinity of an underground U deposit was studied. Several water samples from the Lake Palmottu and nearby springs, three lake sediment cores and three peat cores were collected for the study. Uranium concentrations in the water samples varied from 1.4 to 6.9 mBq/l, reflecting the average concentration of near-surface waters in Finland. In some samples, however, the 234 U/ 238 U activity ratio and water chemistry suggest a partial mixing with deeper groundwaters. In the lake sediments, uranium concentrations increases from 53 Bq/kg in surface layer to five fold in the bottom layers deposited 9000 years ago. In peat cores large variations in uranium concentrations can be observed: from tens of Bq/kg to over 20 kBq/kg of peat ash. The large variation also in the 234 U/ 238 U activity ratio, from 0.79 to l.91, tends to indicate uranium migration to the peat from more than one uranium source. (orig.) (19 refs., 5 figs., 1 tab.)

Optical dating of fluvio-deltaic clastic lake-fill sediments - A feasibility study in the Holocene Rhine delta (western Netherlands)

NARCIS (Netherlands)

Wallinga, J.; Bos, I.J.

2010-01-01

We test the applicability of quartz optically stimulated luminescence (OSL) dating on clastic lake sediments to investigate whether this dating method can be applied to study the timing and rate of deposition in Holocene fluvio-deltaic lakes. Our study concerns the filling of a lake by the

Scale and watershed features determine lake chemistry patterns across physiographic regions in the far north of Ontario, Canada

Directory of Open Access Journals (Sweden)

Josef MacLeod

2016-11-01

Full Text Available Changes in the far north of Ontario (>50°N latitude, like climate warming and increased industrial development, will have direct effects on watershed characteristics and lakes. To better understand the nature of remote northern lakes that span the Canadian Shield and Hudson Bay Lowlands, and to address the pressing need for limnological data for this vast, little-studied area of Ontario, lake chemistry surveys were conducted during 2011-2012. Lakes at the transition between these physiographic regions displayed highly variable water chemistry, reflecting the peatland landscape with a mix of bog and fen watersheds, and variations in the extent of permafrost. In the transition area, Shield and Lowlands lakes could not be clearly differentiated based on water chemistry; peat cover decouples, to varying degrees, the lakes from the influences of bedrock and surficial deposits. Regional chemistry differences were apparent across a much broader area of northern Ontario, due to large-scale spatial changes in geology and in the extent of peatlands and permafrost.  Shield lakes in the far northwest of Ontario had Ca, Mg, and TP concentrations markedly higher than those of many Lowlands lakes and previously studied Shield lakes south of 50°N, related to an abundance of lacustrine and glacial end-moraine deposits in the north.

A caveat regarding diatom-inferred nitrogen concentrations in oligotrophic lakes

Science.gov (United States)

Arnett, Heather A.; Saros, Jasmine E.; Mast, M. Alisa

2012-01-01

Atmospheric deposition of reactive nitrogen (Nr) has enriched oligotrophic lakes with nitrogen (N) in many regions of the world and elicited dramatic changes in diatom community structure. The lakewater concentrations of nitrate that cause these community changes remain unclear, raising interest in the development of diatom-based transfer functions to infer nitrate. We developed a diatom calibration set using surface sediment samples from 46 high-elevation lakes across the Rocky Mountains of the western US, a region spanning an N deposition gradient from very low to moderate levels (phosphorus, and hypolimnetic water temperature were related to diatom distributions. A transfer function was developed for nitrate and applied to a sedimentary diatom profile from Heart Lake in the central Rockies. The model coefficient of determination (bootstrapping validation) of 0.61 suggested potential for diatom-inferred reconstructions of lakewater nitrate concentrations over time, but a comparison of observed versus diatom-inferred nitrate values revealed the poor performance of this model at low nitrate concentrations. Resource physiology experiments revealed that nitrogen requirements of two key taxa were opposite to nitrate optima defined in the transfer function. Our data set reveals two underlying ecological constraints that impede the development of nitrate transfer functions in oligotrophic lakes: (1) even in lakes with nitrate concentrations below quantification (<1 μg L−1), diatom assemblages were already dominated by species indicative of moderate N enrichment; (2) N-limited oligotrophic lakes switch to P limitation after receiving only modest inputs of reactive N, shifting the controls on diatom species changes along the length of the nitrate gradient. These constraints suggest that quantitative inferences of nitrate from diatom assemblages will likely require experimental approaches.

Isotopic composition of dissolved inorganic nitrogen in high mountain lakes: variation with altitude in the Pyrenees

Directory of Open Access Journals (Sweden)

M. Bartrons

2010-05-01

Full Text Available Nitrogen deposition in remote areas has increased, but the effect on ecosystems is still poorly understood. For aquatic systems, knowledge of the main processes driving the observed variation is limited, as is knowledge of how changes in nitrogen supply affect lake biogeochemical and food web processes. Differences in dissolved inorganic nitrogen (DIN between lakes cannot be understood without considering catchment characteristics. In mountains, catchment features (e.g., thermal conditions, land cover vary considerably with elevation. The isotopic composition of nitrogen (δ¹⁵N is increasingly used to study aquatic ecosystem dynamics. Here we explore the variability of δ¹⁵N in DIN in high mountain lakes and show that environmental conditions that change with altitude can affect the isotopic ratio.

We measured ammonium and nitrate δ¹⁵N values in atmospheric deposition, epilimnetic water, deep chlorophyll maximum water (DCMW and sediment pore water (SPW from eight mountain lakes in the Pyrenees, both above and below the treeline. Lakes showed relatively uniform δ¹⁵N-NH₄⁺ values in SPW (2.2±1.6‰, with no variation corresponding to catchment or lake characteristics. We suggest that organic matter diagenesis under similar sediment conditions is responsible for the low variation between the lakes.

In the water column, the range of δ¹⁵N values was larger for ammonium (−9.4‰ to 7.4‰ than for nitrate (−11.4‰ to −3.4‰, as a result of higher variation both between and within lakes (epilimnetic vs. DCM water. For both compounds part of the difference correlated with altitude or catchment features (e.g., scree proportion. Based on concentration, chemical and isotopic tendencies, we suggest that patterns arise from the distinct relative contributions of two types of water flow paths to the lakes: one from snowpack melting, with little soil

User's guide and data dictionary for Kenai Lakes Investigation Project

International Nuclear Information System (INIS)

Newell, A.D.; Mitch, M.E.

1992-03-01

In 1984, the U.S. Environmental Protection Agency (EPA) implemented the National Surface Water Survey (NSWS) as part of the Aquatic Effects Research Program (AERP). The AERP conducted several integrated studies in areas containing surface waters considered potentially sensitive to change as a result of acidic deposition. The NSWS focused its assessment on lakes and streams located in the contiguous United States. Since the majority of the systems examined in the NSWS receive moderate to high levels of acidic deposition, it is difficult to evaluate the role of natural factors in controlling the chemistry of aquatic ecosystems. Therefore, the EPA implemented a project to collect data on lakes in the Kenai Peninsula of Alaska, an area expected to receive low levels of acidic deposition. The database guide provides a brief overview of the survey and the KLIP database. Detailed information on KLIP results is found in Eilers et al. The document also summarizes the sampling and analytical methods, sources of geographic information, and precision and accuracy results from quality assurance (QA) analysis. The datasets are described in Section 3 and their formats in Section 6. The variables are defined in Section 5, and Appendix A contains a listof the lakes and their chemistry. Appendix B provides reference values taken from the Long Range Transport of Airborne Pollutants (LRTAP) Project audit samples

Strontium-90 in the bottom sediments of some Finnish lakes

Energy Technology Data Exchange (ETDEWEB)

Ilus, E.; Puhakainen, M.; Saxen, R

1999-07-01

The {sup 90}Sr concentrations in surface waters varied from 14 to 29 Bq m{sup -3} in 1988 and from 16 to 23 Bq m{sup -3} in 1990. In Lake Pielinen almost all the {sup 90}Sr seemed to originate from weapons test fallout, whereas in Lakes Ontojaervi, Naesijaervi and Pyhaejaervi the share of the Chernobyl fallout was equal to that of weapons test fallout. In the sediments, the total amount of {sup 90}Sr per square metre varied from 97 to 1060 Bq m{sup -2} in 1988 and from 310 to 1160 Bq m{sup -2} in 1990. The maximum values occurred in Lake Naesijaervi. The local amount of deposition and the type of sediment were the most important factors affecting strontium values in sediments. In addition, the large variation in total amounts of {sup 90}Sr was due to other environmental factors. The total amounts of {sup 90}Sr in sediments were generally of the same order of magnitude as the {sup 90}Sr deposition on the ground in the area. The concentrations of {sup 90}Sr in surface waters also conformed quite well to the distribution pattern of the deposition values. At some stations there was a clear maximum in a deeper sediment layer, which could be construed as a marker of the nuclear weapons tests in the 1960s. (orig.)

Anthropogenic influences on Pb/Al and lead isotope signature in annually layered Holocene Maar lake sediments

International Nuclear Information System (INIS)

Schettler, G.; Romer, R.L.

1998-01-01

Annually laminated sediments from two Maar lakes in the West Eifel volcanic field (Germany) show anomalously high Pb within sections deposited during the first centuries A.D. exceeding the local geological background 8.5-fold in Lake Meerfelder Maar (MFM) and 4-fold in Lake Schalkenmehrener Maar (SMM). These Pb anomalies are associated with a distinct shift in the Pb isotope signature to less radiogenic compositions. The excess Pb causing the anomaly has the same isotopic composition as galena deposits 60 km to the NW of the Maar lakes. It is suggested that this component was transported airborne into the Maar lakes and originates from regional Roman Pb refinement and cupellation of argentiferous Pb. Varve chronostratigraphy of correlated cores indicates that significant Roman Pb input lasted for about 230 a. SMM does not get fluviatile input. Its sedimentary record is more sensitive to variations in airborne input than that of MFM, which had an inflow. SMM sediment sections deposited during periods of low soil erosion (early Holocene, Dark Ages) with comparably high Pb/Al values also show little radiogenic Pb. This is caused by airborne minerogenic matter from a geochemically and isotopically distinct remote source that becomes apparent only in sedimentation periods of very restricted local allochthonous input. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Preliminary study of the chronology of the sedimentation process in lakes

International Nuclear Information System (INIS)

Patrocinio Junior, Antonio C.; Andrello, Avacir C.

2009-01-01

The soil erosion accelerated which produces the presence of sediment in rivers is one of the main environmental problems and represents a challenge for the sustainable use of soil and water resources. The problems associated with the increased sediments production are mainly related to the rivers siltation, reduced storage capacity of dams and reservoirs and reduction in the quality of aquatic environment. Thus, further information on sedimentation rates in lakes and reservoirs are required, as a parameter for estimating the chronology of production rates of sediment. Therefore, methods to establish the chronology of recent sediments are central base for such research. The cesium-137 is an artificial radionuclide with a half life of 30.2 years, inserted in the environment through the 'fallout' radioactive between the 1950's and 1970's, with two predominant peaks of deposition in 1959 and 1964. The basis for using the cesium-137 in this context (chronology of sediments) is that the cesium-137 is rapidly and strongly adsorbed to fine particles of soil and its distribution in the sediment profile directly reflects the chronology of sediment deposition. The purpose of this work is to use the cesium-137 profile in lake sediments to assess the history of deposition and to obtain information about the erosive process. For this, lake sediments of a mini-hydroelectric power plant built in the 1940's in the city of Londrina-PR were analyzed, showing that cesium-137 can be used as a source of data for chronological assessment of erosive processes occurring in the vicinity of the lake. (author)

Snowmelt Timing as a Determinant of Lake Inflow Mixing

Science.gov (United States)

Roberts, D. C.; Forrest, A. L.; Sahoo, G. B.; Hook, S. J.; Schladow, S. G.

2018-02-01

Snowmelt is a significant source of carbon, nutrient, and sediment loads to many mountain lakes. The mixing conditions of snowmelt inflows, which are heavily dependent on the interplay between snowmelt and lake thermal regime, dictate the fate of these loads within lakes and their ultimate impact on lake ecosystems. We use five decades of data from Lake Tahoe, a 600 year residence-time lake where snowmelt has little influence on lake temperature, to characterize the snowmelt mixing response to a range of climate conditions. Using stream discharge and lake profile data (1968-2017), we find that the proportion of annual snowmelt entering the lake prior to the onset of stratification increases as annual snowpack decreases, ranging from about 50% in heavy-snow years to close to 90% in warm, dry years. Accordingly, in 8 recent years (2010-2017) where hourly inflow buoyancy and discharge could be quantified, we find that decreased snowpack similarly increases the proportion of annual snowmelt entering the lake at weak to positive buoyancy. These responses are due to the stronger effect of winter precipitation conditions on streamflow timing and temperature than on lake stratification, and point toward increased nearshore and near-surface mixing of inflows in low-snowpack years. The response of inflow mixing conditions to snowpack is apparent when isolating temperature effects on snowpack. Snowpack levels are decreasing due to warming temperatures during winter precipitation. Thus, our findings suggest that climate change may lead to increased deposition of inflow loads in the ecologically dynamic littoral zone of high-residence time, snowmelt-fed lakes.

20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.

Science.gov (United States)

Molnia, B.F.; Post, A.; Carlson, P.R.

1996-01-01

Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus Lake consists of five deep bedrock basins, separated by interbasinal highs. Glacial erosion has cut these basins as much as 250 m below sea level. High-resolution seismic reflection surveys conducted in 1991 and 1993 of four of Vitus Lake's basins reveal a complex, variable three-component acoustic stratigraphy. Although not fully sampled, the stratigraphy is inferred to be primarily glacial-marine units of (1) basal contorted and deformed glacial-marine and glacial sediments deposited by basal ice-contact processes and submarine mass-wasting; (2) acoustically well-stratified glacial-marine sediment, which unconformably overlies the basal unit and which grades upward into (3) acoustically transparent or nearly transparent glacial-marine sediment. Maximum thicknesses of conformable glacial-marine sediment exceed 100 m. All of the acoustically transparent and stratified deposits in Vitus Lake are modern in age, having accumulated between 1967 and 1993. The basins where these three-part sequences of "present-day" glacial-marine sediment are accumulating are themselves cut into older sequences of stratified glacial and glacial-marine deposits. These older units outcrop on the islands in Vitus Lake. In 1967, as the result of a major surge, glacier ice completely filled all five basins. Subsequent terminus retreat, which continued through August 1993, exposed these basins, providing new locations for glacial-marine sediment accumulation. A correlation of sediment thicknesses measured from seismic profiles at specific locations within the basins, with the year that each location became ice-free, shows that the sediment accumulation at some locations

Rock magnetic properties of sediments from Lake Sanabria and its catchment (NW Spain): paleoenvironmental implications

Science.gov (United States)

Larrasoaña, J. C.; Borruel, V.; Gómez-Paccard, M.; Rico, M.; Valero-Garces, B.; Moreno-Caballud, A.; Soto, R.

2013-12-01

Lake Sanabria is located in the NW Spanish mountains at 1000 m a.s.l., and constitutes the largest lake of glacial origin in the Iberian Peninsula. Here we present an environmental magnetic study of a Late Pleistocene-Holocene sediment core from Lake Sanabria and from different lithologies that crop out in its catchment, which includes Paleozoic plutonic, metamorphic and vulcanosedimentary rocks, and Quaternary deposits of glacial origin. This study was designed to complement sedimentologic and geochemical studies aimed at unraveling the climatic evolution of the NW Iberian Peninsula during the last deglaciation. Our results indicate that magnetite and pyrrhotite dominate the magnetic assemblage of both the sediments from the lower half of the studied sequence (25.6 - 13 cal kyr BP) deposited in a proglacial environment, and the Paleozoic rocks that make up most of the catchment of the lake. The occurrence of these minerals both in the catchment rocks and in the lake sediments indicates that sedimentation was then driven by the erosion of a glacial flour, which suffered minimal chemical transformation in response to a rapid and short routing to the lake. Sediments from the upper half of the studied sequence, accumulated after 12.4 cal kyr BP in a fluviolacustrine environment, contain magnetite and greigite. This points to a prominent role of post-depositional reductive dissolution, driven by a sharp increase in the accumulation of organic matter into the lake and the creation of anoxic conditions in the sediments, in shaping the magnetic assemblage of Holocene sediments. Pyrrhotite is stable under reducing conditions as opposed to magnetite, which is unstable. We therefore interpret that previous pedogenic processes occurred in the then deglaciated catchment of the lake were responsible for the oxidation of pyrrhotite and authigenic formation of magnetite, which survived subsequent reductive diagenesis given its initial larger concentrations. This interpretation is

The luminescence dating chronology of a deep core from Bosten Lake (NW China) in arid central Asia reveals lake evolution over the last 220 ka

DEFF Research Database (Denmark)

Li, Guoqiang; Duan, Yanwu; Huang, Xiaozhong

2016-01-01

The lacustrine deposits of lakes in arid central Asia (ACA) potentially record palaeoclimatic changes on orbital and suborbital time scales, but such changes are still poorly understood due to the lack of reliable chronologies. Bosten Lake, the largest freshwater inland lake in China, is located...... in the southern Tianshan Mountains in central ACA. A 51.6-m-deep lacustrine succession was retrieved from the lake and 30 samples from the succession were used for luminescence dating to establish a chronology based on multi-grain quartz OSL and K-feldspar post-IR IRSL (pIRIR290) dating. Quartz OSL ages were only....... A stable deep lake occurred at c. 220, 210–180, c. 165, 70–60, 40–30 and 20–5 ka, while shallow levels occurred at c. 215, 180–165, 100–70, 60–40 and 30–20 ka. Bosten Lake levels decreased by at least ~29 m and possibly the lake even dried up between c. 160 and c. 100 ka. We suggest that the water...

Preliminary U-Th Dating of Endogenic Gypsum From Lake Petén-Itzá, Guatemala

Science.gov (United States)

Gamble, V. C.; Gallup, C. D.; Hodell, D.; Anselmetti, F.; Brenner, M.; Ariztegui, D.

2007-05-01

Uranium-thorium dating of lake sediments can provide accurate ages beyond the range of radiocarbon dating. Many lakes have endogenic precipitation of calcium bearing minerals that allow for substitution by uranium within their crystal structures. The water chemistry of Lake Petén-Itzá, located in northern Guatemala, is dominated by calcium, sulfate and carbonate ions (Deevey et al. 1980; Curtis et al. 1998). Changes in regional climate due to suspected shifts in the ITCZ over the past 85,000 years resulted in both calcite and gypsum deposition, especially during drier periods (Hodell et al. 2006). Both precipitates incorporate uranium from the lake water and can be used for U-Th dating. U-Th dating is problematic in lake systems for several reasons: the potential for 1) diagenetic alteration or dissolution while the endogenic precipitates are settling and after deposition and 2) contamination by detrital thorium. Contamination is a primary issue because of the difficulty of separating the precipitates from the sediment. Despite these concerns, U-Th dating of lake sediments has the potential to be successful with careful selection of precipitates and thorough analysis of the precipitate, the lake system, and the diagenetic environment. Preliminary samples of Lake Petén-Itzá gypsum contain euhedral crystals, indicating a lack of post-depositional alteration. However, the samples have high background thorium levels, indicating the necessity of using the U-Th total sample dissolution isochron dating method (as described by Ku, 2000) to quantify authigenic thorium. Curtis J.H., Brenner M., Hodell D.A., Balser R.A., Islebe G.A., Hooghiemstra H. 1998. A multi-proxy study of Holocene environmental change in the Maya lowlands of Petén, Guatemala. Journal of Paleolimnology 19, 139-159. Deevey E.S., Brenner M., Flannery M.S., Yezdani G.H. 1980. Lakes Yaxha and Scanab, Petén, Guatemala: Limnology and hydrology. Arch. Hydrobiol. 57, 419-460. Hodell D.A., Anselmetti F

The post-depositional accumulation of metal-rich cyanide phases in submerged tailings deposits

International Nuclear Information System (INIS)

Jambor, J.L.; Martin, A.J.; Gerits, J.

2009-01-01

The characterization and accumulation pathway of metal-rich cyanide phases in mine-contaminated Balmer Lake (Ontario, Canada) were assessed through detailed examination of sediment mineralogy and porewater composition. The near-surface deposits in the lake consist of fine-grained calcareous tailings intermixed with natural organic-rich lake sediments. The tailings contain blue to greenish Fe-dominant cyanide that has formed in situ within the tailings. X-ray diffraction confirmed the presence of a mixed ferri/ferrocyanide [Fe 4 III (Fe II (CN) 6 ) 3 ], commonly referred to as 'Prussian Blue' but it is likely other metal-cyanide complexes are present as evidenced by the distinct colour variations. The cyanide phases occur in up to 1 wt.% as discrete particles and as bedded layers, where the cyanide phases act to cement other siliceous tailings components into a heterogeneous blend. Energy Dispersion X-ray Spectroscopy (EDS) analyses indicate that the authigenic cyanide precipitates contain variable amounts of Ni, Cu and Zn. Quantitatively, the cyanide compounds represent the dominant repository for Cu in Balmer Lake sediments. For Ni and Zn, cyanide associations are secondary in importance to Fe oxyhydroxides. High-resolution porewater profiles and solubility considerations suggest that the formation of the cyanide complexes is a feature of historical (pre-1990) conditions when aqueous cyanide concentrations were higher in the lake.

The post-depositional accumulation of metal-rich cyanide phases in submerged tailings deposits

Energy Technology Data Exchange (ETDEWEB)

Jambor, J.L. [Leslie Research and Consulting, 316 Rosehill Wynd, Tsawwassen, BC, V4M 3L9 (Canada); Martin, A.J., E-mail: ajm@lorax.ca [Lorax Environmental Services, 2289 Burrard St., Vancouver, BC, V6J 3H9 (Canada); Gerits, J. [Lorax Environmental Services, 2289 Burrard St., Vancouver, BC, V6J 3H9 (Canada)

2009-12-15

The characterization and accumulation pathway of metal-rich cyanide phases in mine-contaminated Balmer Lake (Ontario, Canada) were assessed through detailed examination of sediment mineralogy and porewater composition. The near-surface deposits in the lake consist of fine-grained calcareous tailings intermixed with natural organic-rich lake sediments. The tailings contain blue to greenish Fe-dominant cyanide that has formed in situ within the tailings. X-ray diffraction confirmed the presence of a mixed ferri/ferrocyanide [Fe{sub 4}{sup III}(Fe{sup II}(CN){sub 6}){sub 3}], commonly referred to as 'Prussian Blue' but it is likely other metal-cyanide complexes are present as evidenced by the distinct colour variations. The cyanide phases occur in up to 1 wt.% as discrete particles and as bedded layers, where the cyanide phases act to cement other siliceous tailings components into a heterogeneous blend. Energy Dispersion X-ray Spectroscopy (EDS) analyses indicate that the authigenic cyanide precipitates contain variable amounts of Ni, Cu and Zn. Quantitatively, the cyanide compounds represent the dominant repository for Cu in Balmer Lake sediments. For Ni and Zn, cyanide associations are secondary in importance to Fe oxyhydroxides. High-resolution porewater profiles and solubility considerations suggest that the formation of the cyanide complexes is a feature of historical (pre-1990) conditions when aqueous cyanide concentrations were higher in the lake.

Pluvial lakes in the Great Basin of the western United States: a view from the outcrop

Science.gov (United States)

Reheis, Marith C.; Adams, Kenneth D.; Oviatt, Charles G.; Bacon, Steven N.

2014-01-01

Paleo-lakes in the western United States provide geomorphic and hydrologic records of climate and drainage-basin change at multiple time scales extending back to the Miocene. Recent reviews and studies of paleo-lake records have focused on interpretations of proxies in lake sediment cores from the northern and central parts of the Great Basin. In this review, emphasis is placed on equally important studies of lake history during the past ∼30 years that were derived from outcrop exposures and geomorphology, in some cases combined with cores. Outcrop and core records have different strengths and weaknesses that must be recognized and exploited in the interpretation of paleohydrology and paleoclimate. Outcrops and landforms can yield direct evidence of lake level, facies changes that record details of lake-level fluctuations, and geologic events such as catastrophic floods, drainage-basin changes, and isostatic rebound. Cores can potentially yield continuous records when sampled in stable parts of lake basins and can provide proxies for changes in lake level, water temperature and chemistry, and ecological conditions in the surrounding landscape. However, proxies such as stable isotopes may be influenced by several competing factors the relative effects of which may be difficult to assess, and interpretations may be confounded by geologic events within the drainage basin that were unrecorded or not recognized in a core. The best evidence for documenting absolute lake-level changes lies within the shore, nearshore, and deltaic sediments that were deposited across piedmonts and at the mouths of streams as lake level rose and fell. We review the different shorezone environments and resulting deposits used in such reconstructions and discuss potential estimation errors. Lake-level studies based on deposits and landforms have provided paleohydrologic records ranging from general changes during the past million years to centennial-scale details of fluctuations during the

An innovative jet boring mining method available for the high grade uranium ore underground deposits

International Nuclear Information System (INIS)

Narcy, J.L.

1996-01-01

An innovative mining method, based on the capability of a high pressure water jet to desaggregate rock, has been conceived and tested with success at the highest grade uranium ore deposit in the world, the Cigar Lake deposit in Saskatchewan, Canada. 113 tonnes of ore at 13% U were mined out by a new jet-boring mining method operated on a semi-industrial basis, in 1992 during the test mining program of Cigar Lake Project. (author). 9 figs

Geochemical evolution of groundwater in the Mud Lake area, eastern Idaho, USA

Science.gov (United States)

Rattray, Gordon W.

2015-01-01

Groundwater with elevated dissolved-solids concentrations—containing large concentrations of chloride, sodium, sulfate, and calcium—is present in the Mud Lake area of Eastern Idaho. The source of these solutes is unknown; however, an understanding of the geochemical sources and processes controlling their presence in groundwater in the Mud Lake area is needed to better understand the geochemical sources and processes controlling the water quality of groundwater at the Idaho National Laboratory. The geochemical sources and processes controlling the water quality of groundwater in the Mud Lake area were determined by investigating the geology, hydrology, land use, and groundwater geochemistry in the Mud Lake area, proposing sources for solutes, and testing the proposed sources through geochemical modeling with PHREEQC. Modeling indicated that sources of water to the eastern Snake River Plain aquifer were groundwater from the Beaverhead Mountains and the Camas Creek drainage basin; surface water from Medicine Lodge and Camas Creeks, Mud Lake, and irrigation water; and upward flow of geothermal water from beneath the aquifer. Mixing of groundwater with surface water or other groundwater occurred throughout the aquifer. Carbonate reactions, silicate weathering, and dissolution of evaporite minerals and fertilizer explain most of the changes in chemistry in the aquifer. Redox reactions, cation exchange, and evaporation were locally important. The source of large concentrations of chloride, sodium, sulfate, and calcium was evaporite deposits in the unsaturated zone associated with Pleistocene Lake Terreton. Large amounts of chloride, sodium, sulfate, and calcium are added to groundwater from irrigation water infiltrating through lake bed sediments containing evaporite deposits and the resultant dissolution of gypsum, halite, sylvite, and bischofite.

Late Holocene distribution of lake sediment and peat in NE Uppland, Sweden

International Nuclear Information System (INIS)

Bergstroem, Elisabeth

2001-02-01

This report is part of a larger project conducted by SKB. The aim is to carry out investigations of eight lakes and one bog, with respect to stratigraphic and geographic distribution of sediment and peat. More than 150 corings were made with a Russian peat sampler. The bog was investigated regarding its isolation from the Baltic basin. This site is included in the shore displacement model elaborated from other sites situated at the same isobase for the Litorina Sea. Northern Uppland is an area with a smooth topography, which also affects the lake basins. The water depth is generally shallow, 1-3 metres. The bedrock mainly consists of granitoids. A few areas consist of meta volcanics, younger granites and pegmatites. The Quaternary deposits in Uppland are more or less calcareous, which is reflected in the rich flora with e. g. orchids and saw grass. Till is the most common deposit in the area covering considerable areas but rarely forming geomorphological features. Glaciofluvial deposits i. e. eskers, stretches in more or less S-N direction, being generally small. In northern Uppland, large areas are covered by mires. Most of them are affected by human activities in the form of ditching; some are used for cultivation or as pasture land. One site, Vissomossen, with a levelled isolation threshold at 27. 4 m a. s. l. , is mainly a fen, with a bog developing in the central part. Diatom analyses and AMS dates show that the basin was earlier a bay of the Litorina Sea and isolated 3500-3600 14 C years BP. The former lake basin was as large as the present extension of the mire. Accumulated material reveals that the lake during time has been filled in with sediment, overgrown and finally forming a mire. The result of the present study is summarized as an extended shore displacement model for northern Uppland, and it reflects an ongoing regression in the area. A decline in regression can be compared with the Litorina transgression 3 (L3), which in the Stockholm area is dated

AL:PE - Acidification of Mountain Lakes: Palaeolimnology and Ecology. Part 2 - Remote Mountain Lakes as Indicators of Air Pollution and Climate Change

Energy Technology Data Exchange (ETDEWEB)

Wathne, Bente M; Patrick, Simon; Cameron, Nigel [eds.

1997-07-01

AL:PE is a multi-disciplinary and multi-national project coordinated by research groups in London and Oslo. It is funded by the European Commission, The project is described in this report. The project is the first comprehensive study of remote mountain lakes on a European scale. It is concerned with ecosystems in the arctic and alpine regions of Europe that are threatened by acid deposition, toxic air pollutants and climatic change despite their remoteness. The studies are important not only for ecosystems of the lakes, for which they were designed, but for the arctic and alpine regions in general, since the lakes with their sediment records act as environmental sensors. The AL:PE results illustrate two overarching issues: (1) the importance of these remote and sensitive ecosystems as sensors of long-range transported pollutants and as providers of early warning signals for more widespread environmental change; and (2) the importance and urgency of understanding the present and future impact of pollutants, both singly and in combination, on aquatic ecosystems. Currently, acid deposition is considered the most potent threat. In the context of global warming, however, it is a formidable scientific challenge to disentangle the interactions between the effects of changing deposition patterns of acids, nutrients, trace metals and trace organics. The AL:PE programme has begun to address this challenge and its successor EU project, MOLAR, is designed to tackle the issues more more specifically by focusing on in-depth studies of key sites. 97 refs., 192 figs., 100 tabs.

Lava lake activity at the summit of Kīlauea Volcano in 2016

Science.gov (United States)

Patrick, Matthew R.; Orr, Tim R.; Swanson, Donald A.; Elias, Tamar; Shiro, Brian

2018-04-10

The ongoing summit eruption at Kīlauea Volcano, Hawai‘i, began in March 2008 with the formation of the Overlook crater, within Halema‘uma‘u Crater. As of late 2016, the Overlook crater contained a large, persistently active lava lake (250 × 190 meters). The accessibility of the lake allows frequent direct observations, and a robust geophysical monitoring network closely tracks subtle changes at the summit. These conditions present one of the best opportunities worldwide for understanding persistent lava lake behavior and the geophysical signals associated with open-vent basaltic eruptions. In this report, we provide a descriptive and visual summary of lava lake activity during 2016, a year consisting of continuous lava lake activity. The lake surface was composed of large black crustal plates separated by narrow incandescent spreading zones. The dominant motion of the surface was normally from north to south, but spattering produced transient disruptions to this steady motion. Spattering in the lake was common, consisting of one or more sites on the lake margin. The Overlook crater was continuously modified by the deposition of spatter (often as a thin veneer) on the crater walls, with frequent collapses of this adhered lava into the lake. Larger collapses, involving lithic material from the crater walls, triggered several small explosive events that deposited bombs and lapilli around the Halema‘uma‘u Crater rim, but these did not threaten public areas. The lava lake level varied over several tens of meters, controlled primarily by changes in summit magma reservoir pressure (in part driven by magma supply rates) and secondarily by fluctuations in spattering and gas release from the lake (commonly involving gas pistoning). The lake emitted a persistent gas plume, normally averaging 1,000–8,000 metric tons per day (t/d) of sulfur dioxide (SO2), as well as a constant fallout of small juvenile and lithic particles, including Pele’s hair and tears. The

Complex Drilling Logistics for Lake El’gygytgyn, NE Russia

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Martin Melles,

2009-03-01

Full Text Available Lake El’gygytgyn was formed by astrophysical chance when a meteorite struck the Earth 100 km north of the Arctic Circle in Chukotka 3.6 Myrs ago (Layer, 2000 on the drainage divide between the Arctic Ocean and the Bering Sea. The crater measures ~18 km in diameter and lies nearly in the center of what was to become Beringia, the largestcontiguous landscape in the Arctic to have escaped continental scale glaciation. Within the crater rim today, Lake El’gygytgyn is 12 km in diameter and 170 m deep, enclosing 350–400 m of sediment deposited since the time of impact (Gebhardt et al., 2006. This setting makes the lake ideal for paleoclimate and impact research.

Subaqueous geology and a filling model for Crater Lake, Oregon

Science.gov (United States)

Nathenson, M.; Bacon, C.R.; Ramsey, D.W.

2007-01-01

Results of a detailed bathymetric survey of Crater Lake conducted in 2000, combined with previous results of submersible and dredge sampling, form the basis for a geologic map of the lake floor and a model for the filling of Crater Lake with water. The most prominent landforms beneath the surface of Crater Lake are andesite volcanoes that were active as the lake was filling with water, following caldera collapse during the climactic eruption of Mount Mazama 7700 cal. yr B.P. The Wizard Island volcano is the largest and probably was active longest, ceasing eruptions when the lake was 80 m lower than present. East of Wizard Island is the central platform volcano and related lava flow fields on the caldera floor. Merriam Cone is a symmetrical andesitic volcano that apparently was constructed subaqueously during the same period as the Wizard Island and central platform volcanoes. The youngest postcaldera volcanic feature is a small rhyodacite dome on the east flank of the Wizard Island edifice that dates from 4800 cal. yr B.P. The bathymetry also yields information on bedrock outcrops and talus/debris slopes of the caldera walls. Gravity flows transport sediment from wall sources to the deep basins of the lake. Several debris-avalanche deposits, containing blocks up to 280 m long, are present on the caldera floor and occur below major embayments in the caldera walls. Geothermal phenomena on the lake floor are bacterial mats, pools of solute-rich warm water, and fossil subaqueous hot spring deposits. Lake level is maintained by a balance between precipitation and inflow versus evaporation and leakage. High-resolution bathymetry reveals a series of up to nine drowned beaches in the upper 30 m of the lake that we propose reflect stillstands subsequent to filling of Crater Lake. A prominent wave-cut platform between 4 m depth and present lake level that commonly is up to 40 m wide suggests that the surface of Crater Lake has been at this elevation for a very long time

Geomorphology and hydrochemistry of 12 Alpine lakes in the Gran Paradiso National Park, Italy

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Aldo MARCHETTO

2010-08-01

Full Text Available Twelve Alpine lakes located in the Gran Paradiso National Park, in the western Italian Alps, were sampled during the ice free period in 2008 and analysed for the main morphological, chemical and physical variables in relation to the characteristics of their watershed, with the aim to create a reference database for present and future ecological studies and to support conservation politics with scientific data. The results highlighted that weathering process and direct precipitation input are the main factors determining the hydrochemistry of the studied lakes; moreover the morphological characteristics highly affects the physical properties of the lakes starting from stratification process. The acidification status, the atmospheric input of N compounds and the supply of nutrients were considered in detail. The studied lakes seem to be well preserved by acidification risk. Comparing data from Gran Paradiso National Park with data from European mountain regions ranging in N deposition rates, allows to consider long range anthropogenic impact: the detection of relative low Total Nitrogen (TN concentration is not necessarily a synonym of a soft impact of long range pollutants, being the final nitrogen concentration dependent from retention process, closely related to catchment characteristics, besides N deposition rates; moreover the dominance of Inorganic Nitrogen (IN on Organic Nitrogen (ON highlights that the lakes are interested by N deposition and probably by long range transport of pollutants produced in the urbanized area surrounding the massif. However the Gran Paradiso National Park area is by far less affected by atmospheric pollutants than other Alpine regions, as the Central Alps. Total Phosphorus (TP concentration in Gran Paradiso lakes (1-13 μg L-1, mean level = 4 μg L-1 is an index of oligotrophic and ultraoligotrophic conditions and according to Redfield's ratio phosphorus is mainly the phytoplankton growth limiting element

Radionuclide dating ({sup 21}Pb, {sup 137}Cs, {sup 241}Am) of recent lake sediments in a highly active geodynamic setting (Lakes Puyehue and Icalma-Chilean Lake District)

Energy Technology Data Exchange (ETDEWEB)

Arnaud, F. [Processus et Bilan en Domaine Sedimentaire, UMR CNRS 8110, Bat. SN5, UST Lille 1, F-59655 Villeneuve d' Ascq (France); Geodynamique des Chaines Alpines, UMR CNRS 5025, Bat. Belledonne, Universite de Savoie, F-73373 Le Bourget du Lac (France); Magand, O. [Laboratoire de Glaciologie et Geophysique de l' Environnement, UMR CNRS 5183, 54 rue Moliere, F-38402 Saint Martin d' Heres Cedex (France)]. E-mail: magand@lgge.obs.ujf-grenoble.fr; Chapron, E. [Renard Centre of Marine Geology, University of Gent, Department of Geology and Soil Science, Krijgslaan 281 S8, B-9000 Gent (Belgium); Bertrand, S. [U.R. Argiles et Paleoclimats, University of Liege, Allee du 6 Aout, B18, ULG-Sart-Tilman, B-4000 Liege (Belgium); Boes, X. [U.R. Argiles et Paleoclimats, University of Liege, Allee du 6 Aout, B18, ULG-Sart-Tilman, B-4000 Liege (Belgium); Charlet, F. [Renard Centre of Marine Geology, University of Gent, Department of Geology and Soil Science, Krijgslaan 281 S8, B-9000 Gent (Belgium); Melieres, M.-A. [Laboratoire de Glaciologie et Geophysique de l' Environnement, UMR CNRS 5183, 54 rue Moliere, F-38402 Saint Martin d' Heres Cedex (France)

2006-08-01

This study presents an attempt to use radionuclide profiles to date four short sediment cores taken from two Chilean lakes located in a highly active geodynamic setting. In such settings, sediment series commonly contain earthquake-triggered reworked layers and/or volcanic ash layers. All of these layers affect the vertical distribution of radionuclides. The drawing up of accurate chronologies is made even more problematic by the low fallout rates of both natural ({sup 21}Pb) and artificial ({sup 137}Cs, {sup 241}Am) radionuclides. However, radionuclide profiles can be 'corrected' by subtracting the influence of instantaneous deposits that have been identified from detailed sedimentological studies. Thus, radionuclides can be used to provide approximate dates for sediment. Independent confirmation of these dates can be provided by varve counting and/or the recognition of historical events. For Lake Puyehue, this approach has allowed particular sediment features to be related to the effects of the 1960 Chilean earthquake (Mw 9.5) on the lake basin and its catchment area. For Lake Icalma, there is a good agreement between radionuclide dates and the dates of the three tephra layers formed during large eruptions of the Llaima volcano in 1946, 1917 and 1883. For both lakes, artificial radionuclide fallout, which culminated in 1965, provides more robust chronological information than {sup 21}Pb dating.

Stratigraphy and paleohydrology of delta channel deposits, Jezero crater, Mars

Science.gov (United States)

Goudge, Timothy A.; Mohrig, David; Cardenas, Benjamin T.; Hughes, Cory M.; Fassett, Caleb I.

2018-02-01

The Jezero crater open-basin lake contains two well-exposed fluvial sedimentary deposits formed early in martian history. Here, we examine the geometry and architecture of the Jezero western delta fluvial stratigraphy using high-resolution orbital images and digital elevation models (DEMs). The goal of this analysis is to reconstruct the evolution of the delta and associated shoreline position. The delta outcrop contains three distinct classes of fluvial stratigraphy that we interpret, from oldest to youngest, as: (1) point bar strata deposited by repeated flood events in meandering channels; (2) inverted channel-filling deposits formed by avulsive distributary channels; and (3) a valley that incises the deposit. We use DEMs to quantify the geometry of the channel deposits and estimate flow depths of ∼7 m for the meandering channels and ∼2 m for the avulsive distributary channels. Using these estimates, we employ a novel approach for assessing paleohydrology of the formative channels in relative terms. This analysis indicates that the shift from meandering to avulsive distributary channels was associated with an approximately four-fold decrease in the water to sediment discharge ratio. We use observations of the fluvial stratigraphy and channel paleohydrology to propose a model for the evolution of the Jezero western delta. The delta stratigraphy records lake level rise and shoreline transgression associated with approximately continuous filling of the basin, followed by outlet breaching, and eventual erosion of the delta. Our results imply a martian surface environment during the period of delta formation that supplied sufficient surface runoff to fill the Jezero basin without major drops in lake level, but also with discrete flooding events at non-orbital (e.g., annual to decadal) timescales.

Effects of Hypolimnetic Oxygenation on Mercury Cycling in Twin Lake, Washington

Science.gov (United States)

Beutel, M.; Dent, S.; Reed, B.; Moore, B.; Yonge, D.; Shallenberger, E.

2010-12-01

The accumulation of mercury in freshwater aquatic food webs is a widespread health concern. Nearly one-third of US lakes have fish consumption advisories in place due to elevated concentrations of mercury in fish tissue. Mercury, primarily from fossil fuel combustion, is widely deposited across the landscape in the form of ionic mercury. The deposited ionic mercury can be transformed to toxic methylmercury by anaerobic bacteria in anoxic waters and sediments. Once produced, methylmercury is taken up by algae and seston, and then biomagnified up the aquatic food web with levels increasing in successive trophic levels. This presentation summarizes three years (2008-2010) of mercury monitoring at North and South Twin Lakes, moderately deep (maximum depth ~15 m) meso-eutrophic lakes located on the Colville Indian Reservation in eastern Washington State. The objective of the study was to evaluate spatial and temporal patterns of the total and methyl mercury in the water column and zooplankton before and after the implementation of hypolimnetic oxygenation in North Twin Lake in 2009. The working hypothesis was that maintenance of an oxic hypolimnion would repress methylmercury enrichment in bottom waters, and subsequent uptake into zooplankton. Initial results confirm that oxygenation repressed hypolimnetic enrichment of methylmercury. In 2008, prior to oxygenation, peak levels of methylmercury in anaerobic bottom waters of North and South Twin Lakes were 0.4-0.6 ng/L. In 2009 levels were less than 0.05 ng/L in oxygenated North Twin Lake, but were again elevated in anaerobic bottom waters of South Twin Lake. Interestingly, during a two-week oxygenation test in North Twin Lake in the fall of 2008, bottom waters exhibited a short-term and reversible loss of methylmercury that correlated with a decrease in dissolved iron and manganese. Regarding zooplankton, total mercury was higher in zooplankton from oxygenated North Twin Lake relative to non-oxygenated South Twin Lake

Eutrophication of Lake Waters in China: Cost, Causes, and Control

Science.gov (United States)

Le, C.; Zha, Y.; Li, Y.; Sun, D.; Lu, H.; Yin, B.

2010-04-01

Lake water eutrophication has become one of the most important factors impeding sustainable economic development in China. Knowledge of the current status of lake water eutrophicatoin and determination of its mechanism are prerequisites to devising a sound solution to the problem. Based on reviewing the literature, this paper elaborates on the evolutional process and current state of shallow inland lake water eutrophication in China. The mechanism of lake water eutrophication is explored from nutrient sources. In light of the identified mechanism strategies are proposed to control and tackle lake water eutrophication. This review reveals that water eutrophication in most lakes was initiated in the 1980s when the national economy underwent rapid development. At present, the problem of water eutrophication is still serious, with frequent occurrence of damaging algal blooms, which have disrupted the normal supply of drinking water in shore cities. Each destructive bloom caused a direct economic loss valued at billions of yuan. Nonpoint pollution sources, namely, waste discharge from agricultural fields and nutrients released from floor deposits, are identified as the two major sources of nitrogen and phosphorus. Therefore, all control and rehabilitation measures of lake water eutrophication should target these nutrient sources. Biological measures are recommended to rehabilitate eutrophied lake waters and restore the lake ecosystem in order to bring the problem under control.

Investigation of environmental change on the Tega Lake based on lake sediment analysis. Pt. 2. Dating of sediment by the lead-210/cesium-137 method and environmental change detected by the diatom assemblage analysis

International Nuclear Information System (INIS)

Hamada, Takaomi

1998-01-01

Sediment collected in the Tega Lake was dated by lead-210/cesium-137 method and environmental change in the Tega Lake was investigated by analysis of diatom remain assemblages in the sediment. Dating of the lead-210/cesium-137 method proved that the surface 30 cm-thickness of sediment in the Tega Lake was deposited during the recent 50 years. Diatom remain assemblage change in the Hon-Tega Lake sediment started in the early half of 1960's and the changes is characterized decrease of Fragilaria construens, that does not prefer to inhabit eutrophic water, and increase of Cyclotella meneghiniana that prefers to inhabit eutrophic water. This diatom assemblage change indicates that the Tega Lake was eutrophicated, and probably suggests water pollution in the Tega Lake. It is detected that influence of residential development around the Tega Lake and reclaiming by drainage on the Tega Lake. (author)

Occurrence and sources of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in surficial sediments of Lakes Superior and Huron

International Nuclear Information System (INIS)

Shen Li; Gewurtz, Sarah B.; Reiner, Eric J.; MacPherson, Karen A.; Kolic, Terry M.; Khurana, Vin; Helm, Paul A.; Howell, E. Todd; Burniston, Debbie A.; Brindle, Ian D.; Marvin, Chris H.

2009-01-01

Concentrations and congener profile patterns of 2378-substituted PCDD/Fs and DLPCBs in offshore, nearshore and tributary sediments of Lakes Superior and Huron are reported, and spatial trends and source contributions assessed. PCDD/F concentrations ranged from 5 to 18 000 pg/g dw (Lake Superior) and 3 to 6100 pg/g dw (Lake Huron); DLPCBs ranged from 9 to 11 000 pg/g dw (Lake Superior) and 9 to 27 000 pg/g dw (Lake Huron). Our analysis indicated atmospheric deposition is a primary source to depositional areas of both lakes; however, greater PCDD/F and DLPCB concentrations were observed at several nearshore and tributary sites, and were attributed to corresponding land use in the watershed. Statistical analysis and pattern comparison suggested that industrial inputs mainly associated with wood treatment plants, pulp and paper mills, mining operations, and chlorine-based chemical manufacturing also contributed to contamination by PCDD/Fs and DLPCBs in certain nearshore and offshore areas of Lakes Superior and Huron. - Lake-wide 2378-PCDD/F and DLPCB concentrations, spatial trends, and congener patterns are first reported in Lakes Superior and Huron sediments

Stratigraphy and Evolution of Delta Channel Deposits, Jezero Crater, Mars

Science.gov (United States)

Goudge, T. A.; Mohrig, D.; Cardenas, B. T.; Hughes, C. M.; Fassett, C. I.

2017-01-01

The Jezero impact crater hosted an open-basin lake that was active during the valley network forming era on early Mars. This basin contains a well exposed delta deposit at the mouth of the western inlet valley. The fluvial stratigraphy of this deposit provides a record of the channels that built the delta over time. Here we describe observations of the stratigraphy of the channel deposits of the Jezero western delta to help reconstruct its evolution.

A previously unrecognized path of early Holocene base flow and elevated discharge from Lake Minong to Lake Chippewa across eastern Upper Michigan

Science.gov (United States)

Loope, Walter L.; Jol, Harry M.; Fisher, Timothy G.; Blewett, William L.; Loope, Henry M.; Legg, Robert J.

2014-01-01

It has long been hypothesized that flux of fresh meltwater from glacial Lake Minong in North America's Superior Basin to the North Atlantic Ocean triggered rapid climatic shifts during the early Holocene. The spatial context of recent support for this idea demands a reevaluation of the exit point of meltwater from the Superior Basin. We used ground penetrating radar (GPR), foundation borings from six highway bridges, a GIS model of surface topography, geologic maps, U.S. Department of Agriculture–Natural Resources Conservation Service soils maps, and well logs to investigate the possible linkage of Lake Minong with Lake Chippewa in the Lake Michigan Basin across eastern Upper Michigan. GPR suggests that a connecting channel lies buried beneath the present interlake divide at Danaher. A single optical age hints that the channel aggraded to 225 m as elevated receipt of Lake Agassiz meltwater in the Superior Basin began to wane GIS model of Minong's shoreline are consistent with another transgression of Minong after ca. 9.5 ka. At the peak of the latter transgression, the southeastern rim of the Superior Basin (Nadoway Drift Barrier) failed, ending Lake Minong. Upon Minong's final drop, aggradational sediments were deposited at Danaher, infilling the prior breach.

LIMNOLOGY, LAKE BASINS, LAKE WATERS

Directory of Open Access Journals (Sweden)

Petre GÂŞTESCU

2009-06-01

Full Text Available Limnology is a border discipline between geography, hydrology and biology, and is also closely connected with other sciences, from it borrows research methods. Physical limnology (the geography of lakes, studies lake biotopes, and biological limnology (the biology of lakes, studies lake biocoenoses. The father of limnology is the Swiss scientist F.A. Forel, the author of a three-volume entitled Le Leman: monographie limnologique (1892-1904, which focuses on the geology physics, chemistry and biology of lakes. He was also author of the first textbook of limnology, Handbuch der Seenkunde: allgemeine Limnologie,(1901. Since both the lake biotope and its biohydrocoenosis make up a single whole, the lake and lakes, respectively, represent the most typical systems in nature. They could be called limnosystems (lacustrine ecosystems, a microcosm in itself, as the American biologist St.A. Forbes put it (1887.

Spatiotemporal drivers of dissolved organic matter in high alpine lakes: Role of Saharan dust inputs and bacterial activity.

Science.gov (United States)

Mladenov, Natalie; Pulido-Villena, Elvira; Morales-Baquero, Rafael; Ortega-Retuerta, Eva; Sommaruga, Ruben; Reche, Isabel

2008-01-01

The effects of many environmental stressors such as UV radiation are mediated by dissolved organic matter (DOM) properties. Therefore, determining the factors shaping spatial and temporal patterns is particularly essential in the most susceptible, low dissolved organic carbon (DOC) lakes. We analyzed spatiotemporal variations in dissolved organic carbon concentration and dissolved organic matter optical properties (absorption and fluorescence) in 11 transparent lakes located above tree line in the Sierra Nevada Mountains (Spain), and we assessed potential external (evaporation and atmospheric deposition) and internal (bacterial abundance, bacterial production, chlorophyll a, and catchment vegetation) drivers of DOM patterns. At spatial and temporal scales, bacteria were related to chromophoric DOM (CDOM). At the temporal scale, water soluble organic carbon (WSOC) in dust deposition and evaporation were found to have a significant influence on DOC and CDOM in two Sierra Nevada lakes studied during the ice-free periods of 2000-2002. DOC concentrations and absorption coefficients at 320 nm were strongly correlated over the spatial scale (n = 11, R(2) = 0.86; p DOC concentration and CDOM to these factors. At the continental scale, higher mean DOC concentrations and more CDOM in lakes of the Sierra Nevada than in lakes of the Pyrenees and Alps may be due to a combination of more extreme evaporation, and greater atmospheric dust deposition.

Hydrology of the Goat Lake watershed, Snohomish County, Washington, 1982-87

Science.gov (United States)

Dion, N.P.; Ebbert, J.C.; Poole, J.E.; Peck, B.S.

1989-01-01

The Goat Lake watershed in Snohomish County, Washington, functions as an ' experimental watershed ' for long-term studies to determine the effects of acidic precipitation on water resources. Data have been collected there by the U.S. Geological Survey since 1982. The watershed is in a wilderness area of the Cascade Range and is downwind of an industrial and urban area that produces chemical compounds found in acidic precipitation. The lake is considered sensitive to acidic inputs from atmospheric deposition and streamflow. The mean annual discharge of the Goat Lake outflow is 35 cu ft/sec; precipitation on the watershed is calculated to be about 170 in/yr. The inflow to Goat Lake is sufficient to replace the entire contents of the lake basin on an average every 21.5 days, or 17 times/year. Water in Goat Lake, and that of the inlet and outlet, is of low ionic strength and of calcium-bicarbonate type. The lake, although considered oligotrophic, is sufficiently deep to stratify thermally, and summer dissolved-oxygen concentrations in the hypolimnion are depressed. Even though alkalinity and specific conductance at Goat Lake are in the range considered sensitive to acidic inputs , the pH of water in the lake has consistently ranged from 6.1 to 7.2, indicating that the lake is not acidified at this time. (USGS)

Phosphorus loading of mountain lakes: Terrestrial export and atmospheric deposition

Czech Academy of Sciences Publication Activity Database

Kopáček, Jiří; Hejzlar, Josef; Vrba, Jaroslav; Stuchlík, E.

2011-01-01

Roč. 56, č. 4 (2011), s. 1343-1354 ISSN 0024-3590 R&D Projects: GA ČR(CZ) GA206/09/1764; GA ČR(CZ) GA206/07/1200; GA ČR(CZ) GA526/09/0567 Institutional research plan: CEZ:AV0Z60170517 Keywords : oligotrophic lakes * stoichiometry * dissolved organic carbon * C:P ratio Subject RIV: DA - Hydrology ; Limnology Impact factor: 3.416, year: 2011

Changes in sediment volume in Alder Lake, Nisqually River Basin, Washington, 1945-2011

Science.gov (United States)

Czuba, Jonathan A.; Olsen, Theresa D.; Czuba, Christiana R.; Magirl, Christopher S.; Gish, Casey C.

2012-01-01

The Nisqually River drains the southwest slopes of Mount Rainier, a glaciated stratovolcano in the Cascade Range of western Washington. The Nisqually River was impounded behind Alder Dam when the dam was completed in 1945 and formed Alder Lake. This report quantifies the volume of sediment deposited by the Nisqually and Little Nisqually Rivers in their respective deltas in Alder Lake since 1945. Four digital elevation surfaces were generated from historical contour maps from 1945, 1956, and 1985, and a bathymetric survey from 2011. These surfaces were used to compute changes in sediment volume since 1945. Estimates of the volume of sediment deposited in Alder Lake between 1945 and 2011 were focused in three areas: (1) the Nisqually River delta, (2) the main body of Alder Lake, along a 40-meter wide corridor of the pre-dam Nisqually River, and (3) the Little Nisqually River delta. In each of these areas the net deposition over the 66-year period was 42,000,000 ± 4,000,000 cubic meters (m3), 2,000,000 ± 600,000 m3, and 310,000 ± 110,000 m3, respectively. These volumes correspond to annual rates of accumulation of 630,000 ± 60,000 m3/yr, 33,000 ± 9,000 m3/yr, and 4,700 ± 1,600 m3/yr, respectively. The annual sediment yield of the Nisqually (1,100 ± 100 cubic meters per year per square kilometer [(m3/yr)/km2]) and Little Nisqually River basins [70 ± 24 (m3/yr)/km2] provides insight into the yield of two basins with different land cover and geomorphic processes. These estimates suggest that a basin draining a glaciated stratovolcano yields approximately 15 times more sediment than a basin draining forested uplands in the Cascade Range. Given the cumulative net change in sediment volume in the Nisqually River delta in Alder Lake, the total capacity of Alder Lake since 1945 decreased about 3 percent by 1956, 8 percent by 1985, and 15 percent by 2011.

Water Surface Overgrowing of the Tatra’s Lakes

Directory of Open Access Journals (Sweden)

Kapusta Juraj

2018-03-01

Full Text Available Tatra’s lakes are vulnerable ecosystems and an important element of the alpine landscape. Mainly some shallow lake basins succumb to intense detritus sedimentation, fine fractions of material from the catchment area or to the overgrowing of water level by vegetation. In this paper, changes and dynamics of the 12 Tatra’s lake shorelines that were selected based on the detailed mapping of their extent are pointed out. Changes were assessed by accurate comparisons of historical and current orthophoto maps from the years 1949, 1955 and 2015 – and therefore, based on the oldest and the latest relevant materials. Due to the overgrowing of lakes caused by vegetation, their water surface decreased from −0.9% up to −47.9%, during the examined period. Losses were caused by the overgrowing of open water surface by the communities of sedges and peat bogs. The most significant dynamics of the shorelines during the last decades were reached by those lakes, into which fine sediments were simultaneously deposited by means of mountain water coarse. These sediments made the marginal parts of the lake basins shallower and accelerated rapid expansion of vegetation to the detriment of the open water surface. The overgrowing of shallow moraine lakes lying in the vegetation zone is a significant phenomenon of the High Tatras alpine landscape. It leads to their gradual extinction, turn into peat bogs and wet alpine meadows.

An integrated method for removal of harmful cyanobacterial blooms in eutrophic lakes

International Nuclear Information System (INIS)

Wang Zhicong; Li Dunhai; Qin Hongjie; Li Yinxia

2012-01-01

As the eutrophication of lakes becomes an increasingly widespread phenomenon, cyanobacterial blooms are occurring in many countries. Although some research has been reported, there is currently no good method for bloom removal. We propose here a new two-step integrated approach to resolve this problem. The first step is the inactivation of the cyanobacteria via the addition of H 2 O 2 . We found 60 mg/L was the lowest effective dose for a cyanobacterial concentration corresponding to 100 μg/L chlorophyll-a. The second step is the flocculation and sedimentation of the inactivated cyanobacteria. We found the addition of lake sediment clay (2 g/L) plus polymeric ferric sulfate (20 mg/L) effectively deposited them on the lake bottom. Since algaecides and flocculants had been used separately in previous reports, we innovatively combined these two types of reagents to remove blooms from the lake surface and to improve the dissolved oxygen content of lake sediments. - Graphical abstract: The mechanism for the removal of cyanobacterial blooms by using H 2 O 2 , polymeric ferric sulfate (PFS) and lake sediment clay. Display Omitted Highlights: ► We combined algaecide and flocculants together to control cyanobacterial blooms. ► H 2 O 2 was used to irreversibly inactivate the photosynthesis of cyanobacteria. ► Lake sediment clay and polymeric ferric sulfate were used to deposit cyanobacteria. ► Removal rate was very high and re-suspension rate was very low under disturbance. ► The inactivated cyanobacteria could not serve as a seed source for the next bloom. - Inactivation by H 2 O 2 and sedimentation using polymeric ferric sulfate and sediment clay demonstrated high integrated efficiency in removal of cyanobacterial blooms.

What fraction of the total metal flux into lakes is retained in the sediments

Energy Technology Data Exchange (ETDEWEB)

Nriagu, J O; Wong, H K.T.

1986-12-01

The concentrations of, and deposition rates for, the pollutant metals (Pb, Cu, Zn, Ni, and Cd) and the rare earth elements are reported for the sediments and settling particulates in a large, remote lake (Lake Opeongo) in the Algonquin Provincial Park, Ontario. Using a mass conservation model based on the rare earth elements, it is estimated that only 40 to 60% of pollutant metals getting into the lake is retained by the sediments. The low retention rate may explain the widely reported intrabasin and intra-lake differences in metal contents of sediments and casts some doubt on the use of pollutant metal profiles in retrospective assessment of the human contribution to the metal flux into many lake basins. 22 references.

Effects of emission reductions from the smelters in Sudbury on recovery of lakes within the metal deposition zone

Energy Technology Data Exchange (ETDEWEB)

Keller, W.; Heneberry, J.; Clark, M.; Malette, M.; Gunn, J. [Laurentian Univ., Sudbury, ON (Canada) Dept. of Biology

1999-07-01

Recent trends are examined in the chemistry of Sudbury lakes for evidence of further chemical recovery, as well as some of the biological characteristics of recovering Sudbury lakes. Preliminary results are provided from studies investigating physical, chemical and biological factors that may influence the lake recovery process with a focus on the lakes close to Sudbury that were historically the most severely affected. Smelter emission reductions in the Sudbury area have led to substantial changes in the water quality of area lakes, and decreases in acidity, sulfate, and copper and nickel concentrations followed the substantial decreases in emissions during the 1970s and similar trends are continuing after the implementation of large additional smelter emission reductions in the 1990s. Some of the most highly affected lakes close to the Sudbury smelters have showed very dramatic reductions in acidity and metal concentrations during the 1990s. Evaluation of the direct effects of the recent emissions reductions is confounded by the potential continuing effects of previous emission reductions and the effects of weather variations on chemistry time trends in Sudbury lakes. Continued monitoring of Sudbury lakes is essential to evaluate the ultimate effect of emission reduction programs, to develop an understanding of the recovery process, and to determine the need for any additional emission reduction requirements. 38 refs., 7 figs.

A review on anthropogenic impact to the Micro Prespa lake and its damages

Science.gov (United States)

Frasheri, N.; Pano, N.; Frasheri, A.; Beqiraj, G.; Bushati, S.; Taska, E.

2012-04-01

Paper presents the results of the integrated and multidisciplinary studies for investigation of the anthropogenic damages to Albanian part of the transborder Micro Prespa Lake. Remote sensing with Landsat images was used for identification of environmental changes in time for the period 1970 - 2010. Micro Prespa Lake is lake with international status, as Ramsar Convection, International Park and Special Protection Area-79/409/EEC. According to the studies, investigations and analyses, the following were concluded: Devolli River- Micro Prespa Lake irrigation system was not scientifically supported by environmental engineering, hydroeconomy and International Rights principles. It does work according to the projected parameters, and also, doesn't supply the agricultural needs. About of 10 % of the water volume, discharges by Devolli River in Micro Prespa Lake during the winter, is taken from this lake for the irrigation in summer. Great surface of Albanian part of Micro Prespa Lake is destroyed. The other part of the lake is atrophied and the habitat and biodiversity are damaged. Important and unique species of fish, birds and plants of national and international values are risked. The underground karstic connection ways for water circulation are blocked. There are ruining the historic values of the area, such the encient Treni cave from the Bronze Age. The Albanian part of the Micro Prespa Lake has been damaged by the human activities. A huge amount of 1,2 million cubic meters alluvium has been deposited on the lake bottom and lakeshore, which was transported by the Devolli River waters, since 1974. This river waters, rich in alluvium and organic coal material from outcropped geological formations, also absorbed free chemical toxic remains by the drainage of Devolli farm ground, which have changed the chemical features of the lake water and degrading it. Micro Prespa Lake communicates with Macro Prespa Lake, and together with Ohrid Lake. Blockage of underground

Sulfur accumulation and atmospherically deposited sulfate in the Lake States.

Science.gov (United States)

Mark B. David; George Z. Gernter; David F. Grigal; Lewis F. Ohmann

1989-01-01

Characterizes the mass of soil sulfur (adjusted for nitrogen), and atmospherically deposited sulfate along an acid precipitation gradient from Minnesota to Michigan. The relationship of these variables, presented graphically through contour mapping, suggests that patterns of atmospheric wet sulfate deposition are reflected in soil sulfur pools.

A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia

Science.gov (United States)

Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam

2014-01-01

The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into

Sedimentation influx and volcanic interactions in the Fuji Five Lakes: implications for paleoseismological records

Science.gov (United States)

Lamair, Laura; Hubert-Ferrari, Aurélia; Yamamoto, Shinya; El Ouahabi, Meriam; Garrett, Ed; Shishikura, Masanobu; Schmidt, Sabine; Boes, Evelien; Obrochta, Stephen; Nakamura, Atsunori; Miyairi, Yosuke; Yokoyama, Yusuke; De Batist, Marc; Heyvaert, Vanessa M. A.

2017-04-01

The Fuji Fives Lakes are located at the foot of Mount Fuji volcano close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. These lakes are ideally situated to study Mount Fuji volcanism and the interaction between volcanism, changes in lake sedimentation rates and the ability of lakes to record paleoearthquakes. Here, we present newly acquired geological data of Lake Yamanaka and Lake Motosu, including seismic reflection profiles, gravity and piston cores. These two lakes and their respective watersheds were affected by several eruptions of Mount Fuji. Lake Yamanaka, a very shallow lake (max. depth 14 m), was heavily impacted by the scoria fall-out of the A.D. 1707 Hoei eruption of Mount Fuji. A detailed investigation of the effect of the Hoei eruption was conducted on short gravity cores, using high resolution XRD, C/N and 210Pb/137Cs analyses. The preliminary results suggest that the sedimentation rate of Lake Yamanaka drastically reduced after the Hoei eruption, followed by an increase until the present day. Similarly, lacustrine sedimentation in Lake Motosu (max. depth 122 m) was disturbed by Mount Fuji volcanism at a larger scale. The watershed of Lake Motosu was impacted by several lava flows and scoria cones. For example, the Omuro scoria cone reduced the catchment size of Lake Motosu and modified its physiography. The related scoria fall out covered an extensive part of the lake catchment and reduced terrigenous sedimentary influx to Lake Motosu. Within the deep basin of Lake Motosu, seismic reflection data shows two different periods that are distinguished by a major change in the dominant sedimentary processes. During the first period, sublacustrine landslides and turbidity currents were the dominant sedimentation processes. During the second one, the seismic stratigraphy evidences only deposition of numerous turbidites interrupting the hemipelagic sedimentation. Changes in sedimentary processes

Flow of groundwater from great depths into the near surface deposits - modelling of a local domain in northeast Uppland

International Nuclear Information System (INIS)

Holmen, Johan G.; Forsman, Jonas

2005-01-01

Purpose: To study the flow of groundwater from rock masses at great depths and into the surface near deposits by use of mathematical models; and to estimate the spatial and temporal distribution of groundwater from great depths in the surface near deposits (quaternary deposits). The study is about the hydraulic interaction between the geosphere and the biosphere. Methodology: The system studied is represented by time dependent three dimensional mathematical models. The models include groundwater flows in the rock mass and in the quaternary deposits as well as surface water flows. The established groundwater models have such a resolution (degree of detail) that both rock masses at great depth and near surface deposits are included in the flow system studied. The modelling includes simulations under both steady state conditions and transient conditions The transient simulations represents the varying state of the groundwater system studied, caused by the variation in hydro-meteorological conditions during a normal year, a wet-year and a dry-year. The boundary condition along the topography of the model is a non-linear boundary condition, representing the ground surface above the sea and the varying actual groundwater recharge. Area studied: The area studied is located in Sweden, in the Northeast of the Uppland province, close to the Forsmark nuclear power plant. Water balance modelling: To obtain three significantly different groundwater recharge periods for the transient groundwater flow simulations a water balance modelling was carried out based on a statistical analysis of available hydro-meteorological data. To obtain a temporal distribution of the runoff (i.e. potential groundwater recharge), we have conducted a numerical time dependent water balance modelling. General conclusions of groundwater modelling: The discharge areas for the flow paths from great depth are given by the topography and located along valleys and lakes; the spatial and temporal extension of

Flow of groundwater from great depths into the near surface deposits - modelling of a local domain in northeast Uppland

Energy Technology Data Exchange (ETDEWEB)

Holmen, Johan G.; Forsman, Jonas [Golder Associates, Stockholm (Sweden)

2005-01-15

Purpose: To study the flow of groundwater from rock masses at great depths and into the surface near deposits by use of mathematical models; and to estimate the spatial and temporal distribution of groundwater from great depths in the surface near deposits (quaternary deposits). The study is about the hydraulic interaction between the geosphere and the biosphere. Methodology: The system studied is represented by time dependent three dimensional mathematical models. The models include groundwater flows in the rock mass and in the quaternary deposits as well as surface water flows. The established groundwater models have such a resolution (degree of detail) that both rock masses at great depth and near surface deposits are included in the flow system studied. The modelling includes simulations under both steady state conditions and transient conditions The transient simulations represents the varying state of the groundwater system studied, caused by the variation in hydro-meteorological conditions during a normal year, a wet-year and a dry-year. The boundary condition along the topography of the model is a non-linear boundary condition, representing the ground surface above the sea and the varying actual groundwater recharge. Area studied: The area studied is located in Sweden, in the Northeast of the Uppland province, close to the Forsmark nuclear power plant. Water balance modelling: To obtain three significantly different groundwater recharge periods for the transient groundwater flow simulations a water balance modelling was carried out based on a statistical analysis of available hydro-meteorological data. To obtain a temporal distribution of the runoff (i.e. potential groundwater recharge), we have conducted a numerical time dependent water balance modelling. General conclusions of groundwater modelling: The discharge areas for the flow paths from great depth are given by the topography and located along valleys and lakes; the spatial and temporal extension of

Magnetic Signature of Glacial Flour in Sediments From Bear Lake, Utah/Idaho

Science.gov (United States)

Rosenbaum, J. G.; Dean, W. E.; Colman, S. M.; Reynolds, R. L.

2002-12-01

Variations in magnetic properties within an interval of Bear Lake sediments correlative with oxygen isotope stage 2 (OIS 2) and OIS 3 provide a record of glacial flour production for the Uinta Mountains. Like sediments of the same age from Upper Klamath Lake (OR), these Bear Lake sediments have high magnetic susceptibilities (MS) relative to non-glacial-age sediments and contain well-defined millennial-scale variations in magnetic properties. In contrast to glacial flour derived from volcanic rocks surrounding Upper Klamath Lake, glacial flour derived from the Uinta Mountains and deposited in Bear Lake by the Bear River has low magnetite content but high hematite content. The relatively low MS values of younger and older non-glacial-age sediments are due entirely to dilution by non-magnetic endogenic carbonate and to the effects of sulfidic alteration of detrital Fe-oxides. Analysis of samples from streams entering Bear Lake and from along the course of the Bear River demonstrates that, in comparison to other areas of the catchment, sediment derived from the Uinta Mountains is rich in hematite (high HIRM) and aluminum, and poor in magnetite (low MS) and titanium. Within the glacial-age lake sediments, there are strong positive correlations among HIRM, Al/Ti, and fine sediment grain size. MS varies inversely with theses three variables. These relations indicate that the observed millennial-scale variations in magnetic and chemical properties arise from varying proportions of two detrital components: (1) very fine-grained glacial flour derived from Proterozoic metasedimentary rocks in the Uinta Mountains and characterized by high HIRM and low MS, and (2) somewhat coarser material, characterized by higher MS and lower HIRM, derived from widespread sedimentary rocks along the course of the Bear River and around Bear Lake. Measurement of glacial flour incorporated in lake sediments can provide a continuous history of alpine glaciation, because the rate of accumulation

Localized enrichment of polycyclic aromatic hydrocarbons in soil, spruce needles, and lake sediments linked to in-situ bitumen extraction near Cold Lake, Alberta

International Nuclear Information System (INIS)

Korosi, J.B.; Irvine, G.; Skierszkan, E.K.; Doyle, J.R.; Kimpe, L.E.; Janvier, J.; Blais, J.M.

2013-01-01

The extraction of bitumen from the Alberta oil sands using in-situ technologies is expanding at a rapid rate; however, investigations into the environmental impacts of oil sands development have focused on surface mining in the Athabasca region. We measured polycyclic aromatic hydrocarbons (PAH) in soils, spruce needles, and lake sediment cores in the Cold Lake oil sands region to provide a historical and spatial perspective on PAH contamination related to in-situ extraction activities. A pronounced increase in PAH concentrations was recorded in one of two study lakes (Hilda Lake) corresponding to the onset of commercial bitumen production in ∼1985. Distance from extraction rigs was not an important predictor of PAH concentrations in soils, although two samples located near installations were elevated in alkyl PAHs. Evidence of localized PAH contamination in Hilda Lake and two soil samples suggests that continued environmental monitoring is justified to assess PAH contamination as development intensifies. -- Highlights: •In-situ bitumen extraction linked to rise in alkyl PAHs in one of two study lakes. •Alkyl PAHs elevated in two soil samples. •PAH contamination likely related to effluent sources, not atmospheric deposition. -- PAHs in sediments and soils were generally low in areas adjacent to in-situ bitumen extraction rigs in the Cold Lake Alberta oil sands, but evidence of localized contamination at some sites was evident

Tracing the sources of PCDD/Fs and PCBs in Lake Baikal

Energy Technology Data Exchange (ETDEWEB)

Mamontov, A.A.; Mamontova, E.A.; Tarasova, E.N.; McLachlan, M.S.

2000-03-01

Lake Baikal is a unique freshwater ecosystem that has been declared a UNESCO World Heritage Site. It contains high levels of PCBs, and Baikal seal were recently found to have PCDD/F concentrations comparable to those in the Baltic Sea. In this work fish and soil were analyzed to trace the sources of these compounds to the lake. The fish samples indicated that the PCDD/F and PCB contamination of Lake Baikal does not originate from background inputs and that the contamination increases from north to south. The soil inventory was determined at 34 sites around Lake Baikal and in the Angara River valley. For the PCDD/Fs and most PCBs, the soil inventory is a good approximation of the cumulative atmospheric deposition. It varied over a factor of 1,000, with the highest levels in Usol'ye Sibirskoe, a city 110 km north of the southwestern tip of the lake in the highly industrialized Angara River valley, and the lowest values in the pristine areas to the northeast of the lake. A continuous decrease in the soil inventory was observed moving from Usol'ye S. up the Angara River valley to Lake Baikal and from there northeastward along the lake.

Geochemical characteristics of The Emet (Espey-Hisarcik) borate deposits, Kütahya, Turkey

Science.gov (United States)

Koçak, İ.; Koç, Ş.

2018-06-01

Nearly 72% world's borate reserves are in western part of Turkey. The Emet (Kütahya) deposit is one of these deposits. The Emet borate deposit, like other deposits in western Anatolia, was deposited in Miocene lacustrine environment whose formation coincides with volcanic activity started in Paleogene and lasted to the beginning of Quaternary. The borate ore displaying lenticular structure is alternated with claystone, marl, tuff and thin bedded limestone. The mineral paragenesis is composed of colemanite, hydroboracite, Veatchite, dolomite, calcite, montmorillonite and illite. The Emet borate deposit has been the subject of various geologic and mineralogical studies. In the present study major and trace element contents of 60 borate samples from this deposit are discussed. Among the trace elements, significant enrichment was found in As, Se, Sr, Cs, Sb and Li. Element correlations indicate volcanic source for boron (exhalations and hydrothermal solutions) whilst other elements are found to be derived from a terrestrial source. According to REE data, high Ce concentrations and anomalies are generally indicative of oxygenated depositional environment whilst low Ce contents facilitated the lake waters to be low oxygenated as a result of H2S-rich hydrothermal solutions. The weak negative anomaly detected only in the Hisarcık region is attributed to lacking of Eu contribution to the lake due to insufficient alteration on the continent.

Glaciolacustrine deposits formed in an ice-dammed tributary valley in the south-central Pyrenees: New evidence for late Pleistocene climate

Science.gov (United States)

Sancho, Carlos; Arenas, Concha; Pardo, Gonzalo; Peña-Monné, José Luis; Rhodes, Edward J.; Bartolomé, Miguel; García-Ruiz, José M.; Martí-Bono, Carlos

2018-04-01

Combined geomorphic features, stratigraphic characteristics and sedimentologic interpretation, coupled with optically stimulated luminescence (OSL) dates, of a glacio-fluvio-lacustrine sequence (Linás de Broto, northern Spain) provide new information to understand the palaeoenvironmental significance of dynamics of glacier systems in the south-central Pyrenees during the Last Glacial Cycle (≈130 ka to 14 ka). The Linás de Broto depositional system consisted of a proglacial lake fed primarily by meltwater streams emanating from the small Sorrosal glacier and dammed by a lateral moraine of the Ara trunk glacier. The resulting glacio-fluvio-lacustrine sequence, around 55 m thick, is divided into five lithological units consisting of braided fluvial (gravel deposits), lake margin (gravel and sand deltaic deposits) and distal lake (silt and clay laminites) facies associations. Evolution of the depositional environment reflects three phases of progradation of a high-energy braided fluvial system separated by two phases of rapid expansion of the lake. Fluvial progradation occurred during short periods of ice melting. Lake expansion concurred with ice-dam growth of the trunk glacier. The first lake expansion occurred over a time range between 55 ± 9 ka and 49 ± 11 ka, and is consistent with the age of the Viu lateral moraine (49 ± 8 ka), which marks the maximum areal extent of the Ara glacier during the Last Glacial Cycle. These dates confirm that the maximum areal extent of the glacier occurred during Marine Isotope Stages 4 and 3 in the south-central Pyrenees, thus before the Last Glacial Maximum. The evolution of the Linás de Broto depositional system during this maximum glacier extent was modulated by climate oscillations in the northern Iberian Peninsula, probably related to latitudinal shifts of the atmospheric circulation in the southern North-Atlantic Ocean, and variations in summer insolation intensity.

Analysis on metallogenic conditions of paleochannel sandstone type uranium deposits in kelulun region

Energy Technology Data Exchange (ETDEWEB)

Mingyue, Feng [Beijing Research Inst. of Uranium Geology, Beijing (China)

1999-07-01

On the basis of comprehensively analyzing metallogenic conditions of paleochannel sandstone type uranium deposits, the author discusses regional geologic background, characteristics of the basement and sedimentary cover of Kelulun basin and Huchawula-Hulun Lake basin, and the metallogenic potential of paleochannel sandstone type uranium deposits is proposed.

Analysis on metallogenic conditions of paleochannel sandstone type uranium deposits in kelulun region

International Nuclear Information System (INIS)

Feng Mingyue

1999-01-01

On the basis of comprehensively analyzing metallogenic conditions of paleochannel sandstone type uranium deposits, the author discusses regional geologic background, characteristics of the basement and sedimentary cover of Kelulun basin and Huchawula-Hulun Lake basin, and the metallogenic potential of paleochannel sandstone type uranium deposits is proposed

The predominance of young carbon in Arctic whole-lake CH4 and CO2 emissions and implications for Boreal yedoma lakes.

Science.gov (United States)

Elder, C.; Xu, X.; Walker, J. C.; Walter Anthony, K. M.; Pohlman, J.; Arp, C. D.; Townsend-Small, A.; Hinkel, K. M.; Czimczik, C. I.

2017-12-01

Lakes in Arctic and Boreal regions are hotspots for atmospheric exchange of the greenhouse gases CO2 and CH4. Thermokarst lakes are a subset of these Northern lakes that may further accelerate climate warming by mobilizing ancient permafrost C (> 11,500 years old) that has been disconnected from the active C cycle for millennia. Northern lakes are thus potentially powerful agents of the permafrost C-climate feedback. While they are critical for projecting the magnitude and timing these feedbacks from the rapidly warming circumpolar region, we lack datasets capturing the diversity of northern lakes, especially regarding their CH4contributions to whole-lake C emissions and their ability to access and mobilize ancient C. We measured the radiocarbon (14C) ages of CH4 and CO2 emitted from 60 understudied lakes and ponds in Arctic and Boreal Alaska during winter and summer to estimate the ages of the C sources yielding these gases. Integrated mean ages for whole-lake emissions were inferred from the 14C-age of dissolved gases sampled beneath seasonal ice. Additionally, we measured concentrations and 14C values of gases emitted by ebullition and diffusion in summer to apportion C emission pathways. Using a multi-sourced mass balance approach, we found that whole-lake CH4 and CO2 emissions were predominantly sourced from relatively young C in most lakes. In Arctic lakes, CH4 originated from 850 14C-year old C on average, whereas dissolved CO2 was sourced from 400 14C-year old C, and represented 99% of total dissolved C flux. Although ancient C had a minimal influence (11% of total emissions), we discovered that lakes in finer-textured aeolian deposits (Yedoma) emitted twice as much ancient C as lakes in sandy regions. In Boreal, yedoma-type lakes, CH4 and CO2 were fueled by significantly older sources, and mass balance results estimated CH4-ebullition to comprise 50-60% of whole-lake CH4 emissions. The mean 14C-age of Boreal emissions was 6,000 14C-years for CH4-C, and 2

Late Holocene distribution of lake sediment and peat in NE Uppland, Sweden

Energy Technology Data Exchange (ETDEWEB)

Bergstroem, Elisabeth [Stockholm Univ. (Sweden). Dept. of Physical Geography and Quaternary Geology

2001-02-01

This report is part of a larger project conducted by SKB. The aim is to carry out investigations of eight lakes and one bog, with respect to stratigraphic and geographic distribution of sediment and peat. More than 150 corings were made with a Russian peat sampler. The bog was investigated regarding its isolation from the Baltic basin. This site is included in the shore displacement model elaborated from other sites situated at the same isobase for the Litorina Sea. Northern Uppland is an area with a smooth topography, which also affects the lake basins. The water depth is generally shallow, 1-3 metres. The bedrock mainly consists of granitoids. A few areas consist of meta volcanics, younger granites and pegmatites. The Quaternary deposits in Uppland are more or less calcareous, which is reflected in the rich flora with e. g. orchids and saw grass. Till is the most common deposit in the area covering considerable areas but rarely forming geomorphological features. Glaciofluvial deposits i. e. eskers, stretches in more or less S-N direction, being generally small. In northern Uppland, large areas are covered by mires. Most of them are affected by human activities in the form of ditching; some are used for cultivation or as pasture land. One site, Vissomossen, with a levelled isolation threshold at 27. 4 m a. s. l. , is mainly a fen, with a bog developing in the central part. Diatom analyses and AMS dates show that the basin was earlier a bay of the Litorina Sea and isolated 3500-3600 {sup 14}C years BP. The former lake basin was as large as the present extension of the mire. Accumulated material reveals that the lake during time has been filled in with sediment, overgrown and finally forming a mire. The result of the present study is summarized as an extended shore displacement model for northern Uppland, and it reflects an ongoing regression in the area. A decline in regression can be compared with the Litorina transgression 3 (L3), which in the Stockholm area is

On the radiocesium behavior in a small humic lake (Lithuania)

International Nuclear Information System (INIS)

Tarasiuk, N.; Koviazina, E.; Karpicz, R.; Moisejenkova, A.; Astrauskiene, N.

2009-01-01

Peculiarities of radiocesium contamination of a small humic lake, which became meromictic some thirty-five years ago due to the inflow of a large amount of humic water, are presented. The lake consists of two separate water layers, which do not intermix. A lower water layer of the lake below some 3-m depth is stagnant and anaerobic, and radiocesium load of the sediments is mainly caused by nuclear weapons fallout. The radiocesium load of the sediments of the upper monomictic water layer is significantly larger due to additional contamination after the Chernobyl accident. Radiocesium activity concentrations in lake water increase with depth, and even in the surface layer, they are commonly the largest among the neighboring lakes with transparent water. It is shown that bottom areas of the monomictic part of the lake with the elevated radiocesium deepening into sediments are related to the favorite sites of the tench (Tinca tinca) winter torpor. Sediment bioturbation and redistribution due to tench activities distort naturally formed radiocesium vertical profiles and they cannot be used for estimations of sedimentation rates and sediment chronology. The studied lake can be useful as an analogous model in analyzing structural and radiological consequences of humic water inflows to closed lakes. Concerning extreme radiological situations in closed humic lakes related to their specific vertical structure, they may be treated as critical objects in assessing the risk to humans after radionuclide deposition events. (authors)

Environmental impact of uranium mining and milling

International Nuclear Information System (INIS)

Dory, A.B.

1981-08-01

The Atomic Energy Control Board is now involved from the early planning stages in the development of uranium mine/mill facilities. As a result, new facilities (including tailings management areas) are designed and developed to meet a high standard. The impact of the mines and tailings areas in the Elliot Lake area on ground and surface waters and air quality is discussed in detail

Second workshop on radon and radon daughters in urban communities associated with uranium mining and processing

International Nuclear Information System (INIS)

1979-01-01

A second meeting of Atomic Energy Control Board staff, federal and provincial government representatives, and consultants was held to discuss progress in reducing the concentrations of radon and its daughter products in houses in communities like Bancroft, Elliot Lake, Port Hope, and Uranium City. Participants discussed successful and unsuccessful remedial techniques, possible sources of radon, and methods of measuring radon and radon daughters in buildings

Workshop on radon and radon daughters in urban communities associated with uranium mining and processing

International Nuclear Information System (INIS)

1978-01-01

This meeting of Atomic Energy Control Board staff, representatives of other government departments, and consultants was called to exchange information on steps taken to lower radiation levels in houses in communities such as Elliot Lake, Uranium City, and Port Hope. Discussions covered the sources of radon and radon daughters in these houses, radon measurement techniques, and remedial methods that worked or were not successful

High temperature chlorination of uranium and some radionuclides from rich sulphide ores

International Nuclear Information System (INIS)

Mahdy, M.A.

1992-01-01

This work is concerned with the application of the high temperature chlorination technique upon a sulphide-rich uranium ore from elliot lake, ontario, canada. The purpose is to find a substitute to conventional sulphuric acid leaching which involves both acid drainage and radionuclide dissolution problems. Test work has therefore been directed towards studying some relevant factors of chlorination beside the effect of a number of additives

Episodes of low dissolved oxygen indicated by ostracodes and sediment geochemistry at Crystal Lake, Illinois, USA

Science.gov (United States)

Curry, B. Brandon; Filippelli, G.M.

2010-01-01

Low dissolved oxygen during the summer and early fall controls profundal continental ostracode distribution in Crystal Lake (McHenry County), Illinois, favoring Cypria ophthalmica and Physocypria globula at water depths from 6 to 13 m. These species also thrived in the lake's profundal zone from 14,165 to 9600 calendar year before present (cal yr b.p.) during the late Boiling, Allerod, and Younger Dryas chronozones, and early Holocene. Characterized by sand, cemented tubules, large aquatic gastropod shells, and littoral ostracode valves, thin (1-6 cm) tempestite deposits punctuate thicker deposits of organic gyttja from 16,080 to 11,900 cal yr b.p. The succeeding 2300 yr (11,900-9600 cal yr b.p.) lack tempestites, and reconstructed water depths were at their maximum. Deposition of marl under relatively well-oxygenated conditions occurred during the remainder of the Holocene until the arrival of Europeans, when the lake returned to a pattern of seasonally low dissolved oxygen. Such conditions are also indicated in the lake sediment by the speciation of phosphorus, high concentrations of organic carbon, and abundant iron and manganese occluded to mineral grains. Initial low dissolved oxygen was probably caused by the delivery of dissolved P and Fe in shallow groundwater, the chemistry of which was influenced by Spodosol pedogenesis under a spruce forest. The triggering may have been regionally warm and wet conditions associated with retreat of the Lake Michigan lobe (south-central Laurentide Ice Sheet). ?? 2010, by the American Society of Limnology and Oceanography Inc.

Reconstruction of Late Pleistocene Paleoenvironments using bulk geochemistry of paleosols from the Lake Victoria Region

Science.gov (United States)

Beverly, Emily J.; Peppe, Daniel J.; Driese, Steven G.; Blegen, Nick; Faith, J. Tyler; Tryon, Christian A.; Stinchcomb, Gary E.

2017-11-01

The impact of changing environments on the evolution and dispersal of Homo sapiens is highly debated, but few data are available from equatorial Africa. Lake Victoria is the largest freshwater lake in the tropics and is currently a biogeographic barrier between the eastern and western branches of the East African Rift. The lake has previously desiccated at 17 ka and again at 15 ka, but little is known from this region prior to the Last Glacial Maximum. The Pleistocene terrestrial deposits on the northeast coast of Lake Victoria (94 to 36 ka) are ideal for paleoenvironmental reconstructions where volcaniclastic deposits (tuffs), fluvial deposits, tufa, and paleosols are exposed, which can be used to reconstruct Critical Zones (CZ) of the past (paleo-CZs). The paleo-CZ is a holistic concept that reconstructs the entire landscape using geologic records of the atmosphere, hydrosphere, lithosphere, biosphere, and pedosphere (the focus of this study). New paleosol-based mean annual precipitation (MAP) proxies from Karungu, Rusinga Island, and Mfangano Island indicate an average MAP of 750108 mm yr-1 (CALMAG), 800182 mm yr-1 (CIA-K), and 1010228 mm yr-1 (PPM1.0) with no statistical difference throughout the 11 m thick sequence. This corresponds to between 54 and 72% of modern precipitation. Tephras bracketing these paleosols have been correlated across seven sites, and sample a regional paleo-CZ across a 55 km transect along the eastern shoreline of the modern lake. Given the sensitivity of Lake Victoria to precipitation, it is likely that the lake was significantly smaller than modern between 94 ka and 36 ka. This would have removed a major barrier for the movement of fauna (including early modern humans) and provided a dispersal corridor across the equator and between the rifts. It is also consistent with the associated fossil faunal assemblage indicative of semi-arid grasslands. During the Late Pleistocene, the combined geologic and paleontological evidence suggests a

Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

Directory of Open Access Journals (Sweden)

Emily J. Beverly

2017-11-01

Full Text Available The impact of changing environments on the evolution and dispersal of Homo sapiens is highly debated, but few data are available from equatorial Africa. Lake Victoria is the largest freshwater lake in the tropics and is currently a biogeographic barrier between the eastern and western branches of the East African Rift. The lake has previously desiccated at ~17 ka and again at ~15 ka, but little is known from this region prior to the Last Glacial Maximum. The Pleistocene terrestrial deposits on the northeast coast of Lake Victoria (94–36 ka are ideal for paleoenvironmental reconstructions where volcaniclastic deposits (tuffs, fluvial deposits, tufa, and paleosols are exposed, which can be used to reconstruct Critical Zones (CZ of the past (paleo-CZs. The paleo-CZ is a holistic concept that reconstructs the entire landscape using geologic records of the atmosphere, hydrosphere, lithosphere, biosphere, and pedosphere (the focus of this study. New paleosol-based mean annual precipitation (MAP proxies from Karungu, Rusinga Island, and Mfangano Island indicate an average MAP of 750 ± 108 mm year−1 (CALMAG, 800 ± 182 mm year−1 (CIA-K, and 1,010 ± 228 mm year−1 (PPM1.0 with no statistical difference throughout the 11 m thick sequence. This corresponds to between 54 and 72% of modern precipitation. Tephras bracketing these paleosols have been correlated across seven sites, and sample a regional paleo-CZ across a ~55 km transect along the eastern shoreline of the modern lake. Given the sensitivity of Lake Victoria to precipitation, it is likely that the lake was significantly smaller than modern between 94 and 36 ka. This would have removed a major barrier for the movement of fauna (including early modern humans and provided a dispersal corridor across the equator and between the rifts. It is also consistent with the associated fossil faunal assemblage indicative of semi-arid grasslands. During the Late Pleistocene, the combined geologic and

Rapid atmospheric transport and large-scale deposition of recently synthesized plant waxes

Science.gov (United States)

Nelson, Daniel B.; Ladd, S. Nemiah; Schubert, Carsten J.; Kahmen, Ansgar

2018-02-01

Sedimentary plant wax 2H/1H ratios are important tools for understanding hydroclimate and environmental changes, but large spatial and temporal uncertainties exist about transport mechanisms from ecosystem to sediments. To assess atmospheric pathways, we collected aerosol samples for two years at four locations within a ∼60 km radius in northern Switzerland. We measured n-alkane distributions and 2H/1H ratios in these samples, and from local plants, leaf litter, and soil, as well as surface sediment from six nearby lakes. Increased concentrations and 2H depletion of long odd chain n-alkanes in early summer aerosols indicate that most wax aerosol production occurred shortly after leaf unfolding, when plants synthesize waxes in large quantities. During autumn and winter, aerosols were characterized by degraded n-alkanes lacking chain length preferences diagnostic of recent biosynthesis, and 2H/1H values that were in some cases more than 100‰ higher than growing season values. Despite these seasonal shifts, modeled deposition-weighted average 2H/1H values of long odd chain n-alkanes primarily reflected summer values. This was corroborated by n-alkane 2H/1H values in lake sediments, which were similar to deposition-weighted aerosol values at five of six sites. Atmospheric deposition rates for plant n-alkanes on land were ∼20% of accumulation rates in lakes, suggesting a role for direct deposition to lakes or coastal oceans near similar production sources, and likely a larger role for deposition on land and transport in river systems. This mechanism allows mobilization and transport of large quantities of recently produced waxes as fine-grained material to low energy sedimentation sites over short timescales, even in areas with limited topography. Widespread atmospheric transfer well before leaf senescence also highlights the importance of the isotopic composition of early season source water used to synthesize waxes for the geologic record.

Gamma-emitting radionuclides in the bottom sediments of some Finnish lakes

International Nuclear Information System (INIS)

Ilus, E.; Puhakainen, M.; Saxen, R.

1993-10-01

In 1988 and 1990 bottom sediment and surface water samples were taken from eight large lakes representing all five categories of deposition regions contaminated by the chernobyl fallout in Finland. All samples were analysed for gamma-emitting radionuclides. The 137 Cs concentrations in surface waters varied in 1988 from 20 to 310 Bq/m 3 and in 1990 from 78 to 170 Bq/m 3 . The other radionuclides of Chernobyl origin detected in water samples were 106 Ru, 125 Sb and 134 Cs. In the sediments the total amount of 137 Cs per square metre varied in 1988 from 1100 to 160 000 Bq/m 2 and in 1990 from 14 000 to 250 000 Bq/m 2 . The maximum values were in Lake Pyhaejaervi. The maximum concentration of 137 Cs in the surface layer of sediment (0-2cm) was 55 700 Bq/kg dry wt in Lake Naesijaervi. In addition to the cesium isotopes 137 Cs and 134 Cs , Chernobyl derived 106 Ru, 125 Sb amd 144 Ce were detected i the surface layer of sediment in most lakes. 54 Mn, 60 Co and 110m Ag were also detected in some lakes situated in the regions most contaminated by the Chernobyl fallout. In 1988 the maximum concentrations of 137 Cs and 134 Cs were in the uppermost layer of sediment (0-2cm) at almost all stations. In 1990, the cesium peaks already occurred at many stations in the second slice (2-5cm), which may indicate downward diffusion of cesium in sediments or mixing of sediment layers during sampling. The most important factors affecting cesium values in sediments were the local amount of deposition and the type of sediment. This study did not reveal any correletion between the maximum depth of the lake and the area of the lake with the cesium amounts in the sediments. (orig.). (23 refs., 10 figs., 6 tabs.)

Sediment trace metal profiles in lakes of Killarney Park, Canada from regional to continental influence

International Nuclear Information System (INIS)

Belzile, Nelson; Chen Yuwei; Gunn, John M.; Dixit, Sushil S.

2004-01-01

The lakes in Killarney Provincial Park (KPP) located 40-60 km southwest of Sudbury, Ontario are beginning to recover after decades of being severely affected by acidification and atmospheric pollutants. Detailed profiles of acid-recoverable trace elements (As. Cd, Cu, Co. Fe, Mn, Ni, Pb and Zn) were obtained after aqua regia digestion and ICP-OES analysis of sediment cores taken from six Park lakes. Results permitted the identification of two types of profiles. The first type applies to elements such as Fe, Mn, As and Co for which historical deposition and recent recovery are strongly masked by diagenetic remobilization. The second type of profile applies to elements such as Cd, Cu, Ni, Pb and Zn on which the history of industrialisation in North America and mining activities in Sudbury can be superimposed. Based on sediment data of trace elements less affected by diagenetic remobilization (Cd, Cu, Ni, Pb, Zn), chemical recovery indices can be estimated from depth profiles. Indices of maximum (C p ) and surface (C s ) contamination were calculated by dividing the concentration of a given metal by the pre-industrial level. The ratio of the two indices provided a simple estimation of the chemical recovery of lakes that does not consider the influence of the watershed or the lake pH. Profiles of metals in sediment of KPP complement the water quality monitoring data and tend to indicate that this area is in transition from dominant influence of regional pollution sources to becoming controlled by continental atmospheric deposition. - Lakes in Killarney Park are in transition from being impacted by regional pollution to being controlled by continental atmospheric deposition

Characteristics of the summit lakes of Ambae volcano and their potential for generating lahars

Directory of Open Access Journals (Sweden)

P. Bani

2009-08-01

Full Text Available Volcanic eruptions through crater lakes often generate lahars, causing loss of life and property. On Ambae volcano, recent eruptive activities have rather tended to reduce the water volume in the crater lake (Lake Voui, in turn, reducing the chances for outburst floods. Lake Voui occupies a central position in the summit caldera and is well enclosed by the caldera relief. Eruptions with significantly higher magnitude than that of 1995 and 2005 are required for an outburst. A more probable scenario for lahar events is the overflow from Lake Manaro Lakua bounded on the eastern side by the caldera wall. Morphology and bathymetry analysis have been used to identify the weakest point of the caldera rim from which water from Lake Manaro Lakua may overflow to initiate lahars. The 1916 disaster described on south-east Ambae was possibly triggered by such an outburst from Lake Manaro Lakua. Taking into account the current level of Lake Manaro Lakua well below a critical overflow point, and the apparently low potential of Lake Voui eruptions to trigger lahars, the Ambae summit lakes may not be directly responsible for numerous lahar deposits identified around the Island.

Biogeochemical conversion of sulfur species in saline lakes of Steppe Altai

Science.gov (United States)

Borzenko, Svetlana V.; Kolpakova, Marina N.; Shvartsev, Stepan L.; Isupov, Vitaly P.

2017-08-01

The aim of the present research is to identify the main mechanisms of sulfur behavior in saline lakes in the course of time and followed transformations in their chemical composition. The influence of water on chemical composition of biochemical processes involved in decomposition of organic matter was determined by the study of behavior of reduced forms of sulfur in lakes. The determination of reduced forms of sulfur was carried out by successive transfer of each form of sulfur to hydrogen sulfide followed by photometric measurements. The other chemical components were determined by standard methods (atomic absorption, potentiometric method, titration method and others). The salt lakes of the Altai steppe were studied in summer season 2013-2015. Analysis of the chemical composition of the saline lakes of Altai Krai has shown that carbonate-, hydrocarbonate- and chloride ions dominate among anions; sodium is main cation; sulfates are found in subordinate amounts. Reduced forms of sulfur occur everywhere: hydrogen and hydrosulfide sulfur S2- prevail in the bottom sediments; its derivative—elemental S0—prevails in the lakes water. The second important species in water of soda lakes is hydrosulfide sulfur S2-, and in chloride lakes is thiosulfate sulfur S2O3 2- . The lag in the accumulation of sulfates in soda lakes in comparison to chloride lakes can be explained by their bacterial reduction, followed by the formation and deposition of iron sulfides in sediments. In chloride lakes gypsum is a predominantly barrier for sulfates.

Sinkhole risk assessment by ERT: The case study of Sirino Lake (Basilicata, Italy)

Science.gov (United States)

Giampaolo, V.; Capozzoli, L.; Grimaldi, S.; Rizzo, E.

2016-01-01

The presence of natural or artificial lakes and reservoirs that can drain because of natural phenomena can generate catastrophic events affecting urban and agricultural areas next to the source area. Therefore, geophysical prospecting techniques have been applied in the study of Sirino Lake, which, during the last century, was affected by the sudden opening of small sinkholes, resulting in the almost total draining of the lake and in the sudden increase of water flow rates of distal springs. Two electrical resistivity tomographies (ERTs) were carried out across the lake, using electrode arrays located on land and across the water body. Self-potential (SP) data were acquired around the lake shore and the surrounding area. The geophysical prospecting contributed significant data toward explaining the unique hydrogeological characteristics of the lake. Integration of geophysical, geological, hydrogeological, and geomorphological data allowed us to estimate the thickness of the lacustrine deposits beneath the lake, to describe the main patterns of the subsurface fluid flows in the area, and to identify possible water escape routes causing the piping phenomena.

Forsmark site investigation. Investigation of marine and lacustrine sediment in lakes. Field data 2003

Energy Technology Data Exchange (ETDEWEB)

Hedenstroem, Anna [SGU, Uppsala (Sweden)

2003-04-01

The aim of this activity is to describe the aerial and stratigraphical distribution of marine and lacustrine sediment i.e. sediment overlaying the glacial till and/or bedrock surface, in lakes in the Forsmark area. The investigation is carried out within areas where mapping of unconsolidated Quaternary deposits is presently carried out. Since small and shallow lakes cover a large part of the region, this work will give important information on the distribution and stratigraphy of sedimentary deposits not included in the regular mapping of unconsolidated Quaternary deposits within the site investigation programme. Samples were also collected for laboratory analyses of grain size distribution, mineralogical composition as well as the total content of C, N and S and calcium carbonate. The analyses will be carried out on selected samples of representative sedimentary units in order to characterise the chemical and physical properties of the unconsolidated deposits. The analytical data will be useful for the hydrogeological modelling and for models of the Quaternary evolution of the area. The mineralogical analyses of clay may provide information on the origin of the clay particles. One stratigraphic sequence from Lake Eckarfjaerden will be stored for later analyses, e.g. pollen analysis. This report includes field data from spring 2003. Together, the field data and the forthcoming results from the laboratory analyses will form the basis for construction of stratigraphical profiles to be presented in a following report in the fall 2003.

Forsmark site investigation. Investigation of marine and lacustrine sediment in lakes. Field data 2003

International Nuclear Information System (INIS)

Hedenstroem, Anna

2003-04-01

The aim of this activity is to describe the aerial and stratigraphical distribution of marine and lacustrine sediment i.e. sediment overlaying the glacial till and/or bedrock surface, in lakes in the Forsmark area. The investigation is carried out within areas where mapping of unconsolidated Quaternary deposits is presently carried out. Since small and shallow lakes cover a large part of the region, this work will give important information on the distribution and stratigraphy of sedimentary deposits not included in the regular mapping of unconsolidated Quaternary deposits within the site investigation programme. Samples were also collected for laboratory analyses of grain size distribution, mineralogical composition as well as the total content of C, N and S and calcium carbonate. The analyses will be carried out on selected samples of representative sedimentary units in order to characterise the chemical and physical properties of the unconsolidated deposits. The analytical data will be useful for the hydrogeological modelling and for models of the Quaternary evolution of the area. The mineralogical analyses of clay may provide information on the origin of the clay particles. One stratigraphic sequence from Lake Eckarfjaerden will be stored for later analyses, e.g. pollen analysis. This report includes field data from spring 2003. Together, the field data and the forthcoming results from the laboratory analyses will form the basis for construction of stratigraphical profiles to be presented in a following report in the fall 2003

Near-surface lithogeochemical halo as an aid to discovery of deeply buried unconformity-type uranium deposits, Athabasca Basin, Canada

International Nuclear Information System (INIS)

Clark, L.A.

1987-01-01

Unconformity-type U deposits are being found to depths of more than 400 m where graphitic rocks underlie the Proterozoic sandstone unconformity. Exploration to date involves drilling weak electromagnetic conductors that reflect the graphitic basement. Geochemically detectable zones of alteration are reported for cross-sections through the Deilmann, Midwest, and McClean deposits. Well-developed anomalies lie vertically above the richest portion of the Cigar Lake deposit in an area 150 x 600 m and a weak anomaly in many elements continues over the 1800-m length that was sampled. Total and leachable U are 13 to 8 times background with maximum values of 53 and 26 ppm, respectively. Anomalies 50-100 m by 250-600 m in size are often displaced up to 100 m northeast of the 11B Zone of Dawn Lake. Both total and leachable U anomalies are 16 to 8 times background. By contrast, at the Wolf Lake deposit, only irregular variations occur for most of these elements. The unusual patterns may reflect post-alteration tectonism of the sandstone overlying the deposit as regional thrust faulting occurs nearby. Detection of near-surface lithogeochemical haloes using grids of shallow holes would facilitate discovery of deep deposits and reduce expensive, deep drilling. 12 refs.; 3 figs.; 2 tabs

The Cigar Lake analog study: An international R ampersand D project

International Nuclear Information System (INIS)

Cramer, J.J.; Sargent, F.P.

1994-01-01

This paper provides background information and summarizes the results of AECL's analog study on the Cigar Lake uranium deposit. This R ampersand D project includes national and international cooperation with many organizations directly or indirectly involved in nuclear waste management research. The emphasis is on the analog aspects of this deposit and the implications of modelling activities related to the environmental and safety assessment of the Canadian disposal concept for nuclear fuel waste

Atmospheric wet deposition of mercury in North America

Energy Technology Data Exchange (ETDEWEB)

Sweet, C.W.; Prestbo, E.; Brunette, B.

1999-07-01

Currently, 39 states in the US and 5 Canadian provinces have issued advisories about the dangers of eating mercury-contaminated fish taken from waters within their boundaries. The problem is most severe in the Great Lakes region, the Northeast US states, the Canadian maritime provinces, and in south Florida where many lakes and streams contain fish with concentrations of 1 ppm or higher. For many rural and remote locations, atmospheric deposition is the primary source of mercury. In 1995, the National Atmospheric Deposition Program (NADP) initiated a program to monitor total mercury and methylmercury (MMHg) in wet deposition (rain and snow) in North America. In this program, the Mercury Deposition Network (MDN), individual monitoring sites are funded and operated by a variety of local, state, and federal agencies. However, sampling and analysis are coordinated through a central laboratory so that all of the samples are collected and analyzed using the same protocols. Weekly wet-only precipitation samples are collected using an all-glass sampling train and special handling techniques. Analysis is by cold vapor atomic fluorescence spectrometry using USEPA Method 1631 for total mercury. Nearly 40 MDN sites are in operation in 1999. Most of the sites are in the eastern US and Canada. During 1996 and 1997, the volume-weighted mean concentration of total mercury in precipitation collected at 22 sites ranged from 6.0 to 18.9 ng/L. Annual deposition varied between 2.1 and 25.3 {micro} g/m{sup 2}. The average weekly wet deposition of total mercury is more than three times higher in the summer (June-August) than in the winter (December-February). This increase is due to both higher amounts of precipitation and higher concentrations of mercury in precipitation during the summer. The highest values for mercury concentration in precipitation and wet deposition of mercury were measured in the southeastern US.

Minimum size limits for yellow perch (Perca flavescens) in western Lake Erie

Science.gov (United States)

Hartman, Wilbur L.; Nepszy, Stephen J.; Scholl, Russell L.

1980-01-01

During the 1960's yellow perch (Perca flavescens) of Lake Erie supported a commercial fishery that produced an average annual catch of 23 million pounds, as well as a modest sport fishery. Since 1969, the resource has seriously deteriorated. Commercial landings amounted to only 6 million pounds in 1976, and included proportionally more immature perch than in the 1960's. Moreover, no strong year classes were produced between 1965 and 1975. An interagency technical committee was appointed in 1975 by the Lake Erie Committee of the Great Lakes Fishery Commission to develop an interim management strategy that would provide for greater protection of perch in western Lake Erie, where declines have been the most severe. The committee first determined the age structure, growth and mortality rates, maturation schedule, and length-fecundity relationship for the population, and then applied Ricker-type equilibrium yield models to determine the effects of various minimum length limits on yield, production, average stock weight, potential egg deposition, and the Abrosov spawning frequency indicator (average number of spawning opportunities per female). The committee recommended increasing the minimum length limit of 5.0 inches to at least 8.5 inches. Theoretically, this change would increase the average stock weight by 36% and potential egg deposition by 44%, without significantly decreasing yield. Abrosov's spawning frequency indicator would rise from the existing 0.6 to about 1.2.

A coupled regolith-lake development model applied to the Forsmark site

Energy Technology Data Exchange (ETDEWEB)

Brydsten, Lars; Stroemgren, Maarten (Umeaa Univ., Umeaa (Sweden))

2010-11-15

The Quaternary geology at the Forsmark site has been characterized using both a map of Quaternary deposits and a regolith depth model (RDM) that show the stratigraphy and thickness of different deposits. Regolith refers to all the unconsolidated deposits overlying the bedrock. The surface geology and regolith depth are important parameters for hydrogeological and geochemical modelling and for the overall understanding of the area. The safety assessment analysis should focus on processes involved during a period of 120,000 years, which includes a full glacial cycle; however, the investigations within the site description model do not cover the temporal change of the regolith, a limitation that does not fulfil the requirements for the safety assessment. To this end, this study constructs a model that can predict the surface geology, stratigraphy, and thickness of different strata at any time during a glacial cycle and applies this model to the Forsmark site. The Weichselian ice sheet covered the study area until around 9500 BC. The deglaciation revealed a marine landscape with bedrock, till and glacial clay. For the safety assessment, the most important unconsolidated strata are clay or silt: these small grains can bind nuclear elements more easily than coarser sediment particles. Thick layers of clay can be found where post-glacial clay settled on top of glacial clay, especially where the middle-aged erosion of postglacial clay is missing and where there is an uninterrupted sequence of accumulation of finegrained particles. Such areas could be found in deep marine basins that later become lakes when raised into a supra-marine position. The coupled regolith-lake development model (RLDM) predicts the course of events described above during an interglacial, especially the dynamics of the clay and silt particles. The RLDM is divided into two modules: a marine module that predicts the sediment dynamics caused by wind waves and a lake module that predicts the lake infill

A coupled regolith-lake development model applied to the Forsmark site

International Nuclear Information System (INIS)

Brydsten, Lars; Stroemgren, Maarten

2010-11-01

The Quaternary geology at the Forsmark site has been characterized using both a map of Quaternary deposits and a regolith depth model (RDM) that show the stratigraphy and thickness of different deposits. Regolith refers to all the unconsolidated deposits overlying the bedrock. The surface geology and regolith depth are important parameters for hydrogeological and geochemical modelling and for the overall understanding of the area. The safety assessment analysis should focus on processes involved during a period of 120,000 years, which includes a full glacial cycle; however, the investigations within the site description model do not cover the temporal change of the regolith, a limitation that does not fulfil the requirements for the safety assessment. To this end, this study constructs a model that can predict the surface geology, stratigraphy, and thickness of different strata at any time during a glacial cycle and applies this model to the Forsmark site. The Weichselian ice sheet covered the study area until around 9500 BC. The deglaciation revealed a marine landscape with bedrock, till and glacial clay. For the safety assessment, the most important unconsolidated strata are clay or silt: these small grains can bind nuclear elements more easily than coarser sediment particles. Thick layers of clay can be found where post-glacial clay settled on top of glacial clay, especially where the middle-aged erosion of postglacial clay is missing and where there is an uninterrupted sequence of accumulation of finegrained particles. Such areas could be found in deep marine basins that later become lakes when raised into a supra-marine position. The coupled regolith-lake development model (RLDM) predicts the course of events described above during an interglacial, especially the dynamics of the clay and silt particles. The RLDM is divided into two modules: a marine module that predicts the sediment dynamics caused by wind waves and a lake module that predicts the lake infill

Microplastic pollution in lakes and lake shoreline sediments - A case study on Lake Bolsena and Lake Chiusi (central Italy).

Science.gov (United States)

Fischer, Elke Kerstin; Paglialonga, Lisa; Czech, Elisa; Tamminga, Matthias

2016-06-01

Rivers and effluents have been identified as major pathways for microplastics of terrestrial sources. Moreover, lakes of different dimensions and even in remote locations contain microplastics in striking abundances. This study investigates concentrations of microplastic particles at two lakes in central Italy (Lake Bolsena, Lake Chiusi). A total number of six Manta Trawls have been carried out, two of them one day after heavy winds occurred on Lake Bolsena showing effects on particle distribution of fragments and fibers of varying size categories. Additionally, 36 sediment samples from lakeshores were analyzed for microplastic content. In the surface waters 2.68 to 3.36 particles/m(3) (Lake Chiusi) and 0.82 to 4.42 particles/m(3) (Lake Bolsena) were detected, respectively. Main differences between the lakes are attributed to lake characteristics such as surface and catchment area, depth and the presence of local wind patterns and tide range at Lake Bolsena. An event of heavy winds and moderate rainfall prior to one sampling led to an increase of concentrations at Lake Bolsena which is most probable related to lateral land-based and sewage effluent inputs. The abundances of microplastic particles in sediments vary from mean values of 112 (Lake Bolsena) to 234 particles/kg dry weight (Lake Chiusi). Lake Chiusi results reveal elevated fiber concentrations compared to those of Lake Bolsena what might be a result of higher organic content and a shift in grain size distribution towards the silt and clay fraction at the shallow and highly eutrophic Lake Chiusi. The distribution of particles along different beach levels revealed no significant differences. Copyright © 2016 Elsevier Ltd. All rights reserved.

Neutron activation analysis of sediment core samples of Lake Erhai in southern China and a Salt Lake in India

International Nuclear Information System (INIS)

Toyoda, Kazuhiro; Shinozuka, Yoshitsugu; Miura, Masahiro; Moriyasu, Yuki

2005-01-01

The purpose of this research is in the verification of the hypothesis that the long-lived nuclide ratio of Th/Sc in the deposit sample dug up in the lake with the hinterland of the granite quality is the index of a past change of precipitation and of the event such as earthquakes. As a preceding step the relation between an environmental change and a climate change was studied by the measuring result of the ratio of Th/Sc by the neutron activation analysis about the digging core sample of the Nepalese Katmandu basin (For the past 700,000 years) and the core sample (For 40,000 years and 8,000 years of the past) in Lake Biwa. (H. Katsuta)

History of metal contamination in Lake Illawarra, NSW, Australia.

Science.gov (United States)

Schneider, Larissa; Maher, William; Potts, Jaimie; Batley, Graeme; Taylor, Anne; Krikowa, Frank; Chariton, Anthony; Zawadzki, Atun; Heijnis, Henk; Gruber, Bernd

2015-01-01

Lake Illawarra has a long history of sediment contamination, particularly by metals, as a result of past and current industrial operations and land uses within the catchment. In this study, we examined the history of metal contamination in sediments using metal analysis and (210)Pb and (137)Cs dating. The distributions of copper, zinc, arsenic, selenium, cadmium and lead concentrations within sediment cores were in agreement with historical events in the lake, and indicated that metal contamination had been occurring since the start of industrial activities in Port Kembla in the late 1800 s. Most metal contamination, however, has occurred since the 1960s. Sedimentation rates were found to be 0.2 cm year(-1) in Griffins Bay and 0.3 cm year(-1) in the centre of the lake. Inputs from creeks bringing metals from Port Kembla in the northeast of the lake and a copper slag emplacement from a former copper refinery on the Windang Peninsula were the main sources of metal inputs to Lake Illawarra. The metals of highest concern were zinc and copper, which exceeded the Australian and New Zealand sediment quality guideline values at some sites. Results showed that while historical contamination persists, current management practices have resulted in reduced metal concentrations in surface sediments in the depositional zones in the centre of the lake. Copyright © 2014 Elsevier Ltd. All rights reserved.

210Pb-137Cs dating of glacial lake sediments

International Nuclear Information System (INIS)

Graham, I.J.; Ditchburn, R.G.; Barry, B.J.

2004-01-01

Sediments deposited in New Zealand lakes in the recent past provide excellent archives of local climate change via their trapped biodiversity, varve structure ad sedimentological composition. To unlock the archival information, accurate and fine-scale dating of the deposits is essential. A combination of 210 Pb and 137 Cs dating provides the most reliable and robust approach. Under favourable conditions, 210 Pb dating can provide a detailed chronology to c.120-140 y, and can be accurately calibrated by 137 Cs for the last 40 y or thereabouts. (author). 6 refs., 4 figs

Do invasive mussels restrict offshore phosphorus transport in Lake Huron?

Science.gov (United States)

Cha, Yoonkyung; Stow, Craig A; Nalepa, Thomas F; Reckhow, Kenneth H

2011-09-01

Dreissenid mussels were first documented in the Laurentian Great Lakes in the late 1980s. Zebra mussels (Dreissena polymorpha) spread quickly into shallow, hard-substrate areas; quagga mussels (Dreissena rostriformis bugensis) spread more slowly and are currently colonizing deep, offshore areas. These mussels occur at high densities, filter large water volumes while feeding on suspended materials, and deposit particulate waste on the lake bottom. This filtering activity has been hypothesized to sequester tributary phosphorus in nearshore regions reducing offshore primary productivity. We used a mass balance model to estimate the phosphorus sedimentation rate in Saginaw Bay, a shallow embayment of Lake Huron, before and after the mussel invasion. Our results indicate that the proportion of tributary phosphorus retained in Saginaw Bay increased from approximately 46-70% when dreissenids appeared, reducing phosphorus export to the main body of Lake Huron. The combined effects of increased phosphorus retention and decreased phosphorus loading have caused an approximate 60% decrease in phosphorus export from Saginaw Bay to Lake Huron. Our results support the hypothesis that the ongoing decline of preyfish and secondary producers including diporeia (Diporeia spp.) in Lake Huron is a bottom-up phenomenon associated with decreased phosphorus availability in the offshore to support primary production.

The endemic mollusks reveal history of the long-lived Pliocene Lake Slavonia in NW Croatia

Science.gov (United States)

Mandic, Oleg; Kurečić, Tomislav; Neubauer, Thomas A.; Harzhauser, Mathias

2015-04-01

The present investigation deals with the fossil mollusk record of the long-lived Pliocene Lake Slavonia settled in the southern Pannonian Basin. The samples originate from Vukomeričke gorice, a low hill-range situated north of the Kupa River in the area between the towns of Zagreb, Sisak and Karlovac in NW Croatia. Representing the SW margin of the Lake Slavonia the freshwater deposits alternate there with the alluvial series, providing altogether about 400-m-thick, Pliocene continental succession, known in literature by informal name Paludina beds (acc. to a junior synonym of Viviparus). The endemic fauna of the Lake Slavonia became particularly well-known in the late 19th century after Melchior Neumayr demonstrated that the gradual evolutionary change of the mollusk phenotypes toward more complex morphology represents a function of adaptation to environmental change in the paleolake. Even Charles Darwin commented that result as by far the best case which I have ever met with, showing the direct influence of the conditions of life on the organization. The deposition in the Lake Slavonia (~4.5 to ~1.8 Ma) coincides with the Pliocene Climate Optimum (PCO), but captures also the transition into the Pleistocene climate marked by the initial Ice Age pulse at 2.59 Ma. The increase of polar temperatures resulted during PCO in a significant melting of the ice caps leading to a global sea level rise tentatively getting up to 25 m higher than today. Coincidence of the climate and geodynamic settings in southeastern Europe provided conditions supporting extended settlement of lacustrine environments including Lake Slavonia, Lake Kosovo, Lake Transylvania and Lake Dacia, all characterized by explosive adaptive radiations of viviparid snails. In particular, the latter adaptive radiations resulted in the regional phylostratigraphy of Lake Slavonia Viviparus species enabling excellent stratigraphic control for the investigated deposits. Hence, based on this evidence, the

Changes in water and sediment exchange between the Changjiang River and Poyang Lake under natural and anthropogenic conditions, China.

Science.gov (United States)

Gao, Jian Hua; Jia, Jianjun; Kettner, Albert J; Xing, Fei; Wang, Ya Ping; Xu, Xia Nan; Yang, Yang; Zou, Xin Qing; Gao, Shu; Qi, Shuhua; Liao, Fuqiang

2014-05-15

To study the fluvial interaction between Changjiang River and Poyang Lake, we analyze the observed changes of riverine flux of the mid-upstream of Changjiang River catchment, the five river systems of Poyang Lake and Poyang Lake basin. Inter-annual and seasonal variations of the water discharge and sediment exchange processes between Changjiang River and Poyang Lake are systematically explored to determine the influence of climate change as well as human impact (especially the Three Gorges Dam (TGD)). Results indicate that climate variation for the Changjiang catchment and Poyang Lake watershed is the main factor determining the changes of water exchanges between Changjiang River and Poyang Lake. However, human activities (including the emplacement of the TGD) accelerated this rate of change. Relative to previous years (1956-1989), the water discharge outflow from Poyang Lake during the dry season towards the Changjiang catchment increased by 8.98 km(3)y(-1) during 2003-2010. Evidently, the water discharge flowing into Poyang Lake during late April-late May decreased. As a consequence, water storage of Poyang Lake significantly reduced during late April-late May, resulting in frequent spring droughts after 2003. The freshwater flux of Changjiang River towards Poyang Lake is less during the flood season as well, significantly lowering the magnitude and frequency of the backflow of the Changjiang River during 2003-2010. Human activities, especially the emplacement and operation of the TGD and sand mining at Poyang Lake impose a major impact on the variation of sediment exchange between Changjiang main river and Poyang Lake. On average, sediments from Changjiang River deposited in Poyang Lake before 2000. After 2000, Changjiang River no longer supplied sediment to Poyang Lake. As a consequence, the sediment load of Changjiang River entering the sea increasingly exists of sediments from Lake Poyang during 2003-2010. As a result, Poyang Lake converted from a

Ancillary effects of selected acid deposition control policies

Energy Technology Data Exchange (ETDEWEB)

Moe, R.J.; Lyke, A.J.; Nesse, R.J.

1986-08-01

NAPAP is examining a number of potential ways to reduce the precursors (sulfur dioxide and nitrogen oxides) to acid deposition. However, the policies to reduce acid deposition will have other physical, biological and economic effects unrelated to acid deposition. For example, control policies that reduce sulfur dioxide emissions may also increase visibility. The effects of an acid deposition policy that are unrelated to acid deposition are referred to as ''ancillary'' effects. This reserch identifies and characterizes the principle physical and economic ancillary effects associated with acid deposition control and mitigation policies. In this study the ancillary benefits associated with four specific acid deposition policy options were investigated. The four policy options investigated are: (1) flue gas desulfurization, (2) coal blending or switching, (3) reductions in automobile emissions of NO/sub x/, and (4) lake liming. Potential ancillary benefits of each option were identified and characterized. Particular attention was paid to the literature on economic valuation of potential ancillary effects.

Challenges with modifications of the McClean Lake mill to process midwest ore

International Nuclear Information System (INIS)

Nguyen, T.T.; Backham, L.

2010-01-01

Midwest is a unique uranium deposit with exceptionally high arsenic content. The ore body is located 17 km west of the McClean Lake operation. The McClean Lake mill will be modified to process Midwest ore and handle solid wastes from the Midwest water treatment plant. This paper describes the modifications required of the McClean Lake mill, process challenges associated with treatment of the arsenic, and the possibility of recovering nickel and cobalt as a by-product. It also reviews the complexity in the design of the Midwest water treatment facility which incorporates reverse osmosis technology with conventional physical-chemical water treatment. (author)

The depositional environments of Schöningen 13 II-4 and their archaeological implications.

Science.gov (United States)

Stahlschmidt, Mareike C; Miller, Christopher E; Ligouis, Bertrand; Goldberg, Paul; Berna, Francesco; Urban, Brigitte; Conard, Nicholas J

2015-12-01

Geoarchaeological research at the Middle Pleistocene site of Schöningen 13 II-4, often referred to as the Speerhorizont, has focused on describing and evaluating the depositional contexts of the well-known wooden spears, butchered horses, and stone tools. These finds were recovered from the transitional contact between a lacustrine marl and an overlying organic mud, originally thought to be a peat that accumulated in place under variable moisture conditions. The original excavators proposed that hominin activity, including hunting and butchery, occurred on a dry lake shore and was followed by a rapid sedimentation of organic deposits that embedded and preserved the artifacts. Our geoarchaeological analysis challenges this model. Here, we present evidence that the sediments of Schöningen 13 II-4 were deposited in a constantly submerged area of a paleolake. Although we cannot exclude the possibility that the artifacts were deposited during a short, extreme drying event, there are no sedimentary features indicative of surface exposure in the sediments. Accordingly, this paper explores three main alternative models of site formation: anthropogenic disposal of materials into the lake, a geological relocation of the artifacts, and hunting or caching on lake-ice. These models have different behavioral ramifications concerning hominin knowledge and exploitation of the landscape and their subsistence strategies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Geology and ore deposits of the Section 23 mine, Ambrosia Lake District, New Mexico

International Nuclear Information System (INIS)

Granger, H.C.; Santos, E.S.

1986-01-01

The Section 23 mine is one of about 18 large uranium mines opened in sandstones of the fluvial Westwater Canyon Member of the Jurassic Morrison Formation, in the Ambrosia Lake uranium district, during the early 1960s. Two distinct types of unoxidized ore occur in the mine. One type consists of uranium-rich authigenic organic matter that impregnates parts of the reduced sandstone host rocks. This type of ore occurs as peneconcordant layers which are typically elongate east-southeast, subparallel both to the sedimentary trends and to the regional strike of the host rock. A second type of ore is essentially devoid of organic matter and occurs in thick zones which conform to interfaces that separate oxidized from reduced parts of the host rocks. Genesis of the second type of ore is similar to that of roll-type deposits in Tertiary rocks of Wyoming and Texas. Organic matter in the primary ores was probably introduced into the host rock as humic acids that precipitated in the pores of the sandstone. This material is inferred first to have fixed uranium as urano-organic compounds but with further diagenesis, to have released some of the uranium to form coffinite. Vanadium, molybdenum, and selenium are associated with primary ore and may also have been fixed by the organic matter. The secondary or roll-type ores contain uranium mostly in the form of coffinite and only rarely as uraninite. They also contain vanadium and selenium but are virtually devoid of molybdenum

Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho

Science.gov (United States)

Heil, C.W.; King, J.W.; Rosenbaum, J.G.; Reynolds, R.L.; Colman, Steven M.

2009-01-01

A ???220,000-year record recovered in a 120-m-long sediment core from Bear Lake, Utah and Idaho, provides an opportunity to reconstruct climate change in the Great Basin and compare it with global climate records. Paleomagnetic data exhibit a geomagnetic feature that possibly occurred during the Laschamp excursion (ca. 40 ka). Although the feature does not exhibit excursional behavior (???40?? departure from the expected value), it might provide an additional age constraint for the sequence. Temporal changes in salinity, which are likely related to changes in freshwater input (mainly through the Bear River) or evaporation, are indicated by variations in mineral magnetic properties. These changes are represented by intervals with preserved detrital Fe-oxide minerals and with varying degrees of diagenetic alteration, including sulfidization. On the basis of these changes, the Bear Lake sequence is divided into seven mineral magnetic zones. The differing magnetic mineralogies among these zones reflect changes in deposition, preservation, and formation of magnetic phases related to factors such as lake level, river input, and water chemistry. The occurrence of greigite and pyrite in the lake sediments corresponds to periods of higher salinity. Pyrite is most abundant in intervals of highest salinity, suggesting that the extent of sulfidization is limited by the availability of SO42-. During MIS 2 (zone II), Bear Lake transgressed to capture the Bear River, resulting in deposition of glacially derived hematite-rich detritus from the Uinta Mountains. Millennial-scale variations in the hematite content of Bear Lake sediments during the last glacial maximum (zone II) resemble Dansgaard-Oeschger (D-O) oscillations and Heinrich events (within dating uncertainties), suggesting that the influence of millennial-scale climate oscillations can extend beyond the North Atlantic and influence climate of the Great Basin. The magnetic mineralogy of zones IV-VII (MIS 5, 6, and 7

The discovery and character of Pleistocene calcrete uranium deposits in the Southern High Plains of west Texas, United States

Science.gov (United States)

Van Gosen, Bradley S.; Hall, Susan M.

2017-12-18

This report describes the discovery and geology of two near-surface uranium deposits within calcareous lacustrine strata of Pleistocene age in west Texas, United States. Calcrete uranium deposits have not been previously reported in the United States. The west Texas uranium deposits share characteristics with some calcrete uranium deposits in Western Australia—uranium-vanadium minerals hosted by nonpedogenic calcretes deposited in saline lacustrine environments.In the mid-1970s, Kerr-McGee Corporation conducted a regional uranium exploration program in the Southern High Plains province of the United States, which led to the discovery of two shallow uranium deposits (that were not publicly reported). With extensive drilling, Kerr-McGee delineated one deposit of about 2.1 million metric tons of ore with an average grade of 0.037 percent U3O8 and another deposit of about 0.93 million metric tons of ore averaging 0.047 percent U3O8.The west-Texas calcrete uranium-vanadium deposits occur in calcareous, fine-grained sediments interpreted to be deposited in saline lakes formed during dry interglacial periods of the Pleistocene. The lakes were associated with drainages upstream of a large Pleistocene lake. Age determinations of tephra in strata adjacent to one deposit indicate the host strata is middle Pleistocene in age.Examination of the uranium-vanadium mineralization by scanning-electron microscopy indicated at least two generations of uranium-vanadium deposition in the lacustrine strata identified as carnotite and a strontium-uranium-vanadium mineral. Preliminary uranium-series results indicate a two-component system in the host calcrete, with early lacustrine carbonate that was deposited (or recrystallized) about 190 kilo-annum, followed much later by carnotite-rich crusts and strontium-uranium-vanadium mineralization in the Holocene (about 5 kilo-annum). Differences in initial 234U/238U activity ratios indicate two separate, distinct fluid sources.

Waste management implications of concentrating slimes - characteristics and potential problems

International Nuclear Information System (INIS)