WorldWideScience

Sample records for microbial erosion transport

  1. Sand transport, erosion and granular electrification

    DEFF Research Database (Denmark)

    Merrison, J.P.

    2012-01-01

    is expanding our current understanding and outline the areas of advancement needed in the future. Presentation is made of current models for wind driven detachment/entrainment and the transport rates of sand and dust, including the effects of contact induced grain electrification. This ubiquitous phenomenon...... can affect grain transport through the generation of intense electric fields and processes of electrostatic assembly. Importantly the transport of sand is characterized by saltation, which is known to be an active process for erosion and therefore a source for dust and sand formation. Using novel...... erosion simulation techniques the link between grain transport rates and erosion rates has been quantified. Furthermore this can be linked to production rates for dust and has been associated with chemical and mineral alteration through a process of mechanical activation of fractured surfaces. This work...

  2. Corneal erosions, bacterial contamination of contact lenses, and microbial keratitis.

    Science.gov (United States)

    Willcox, Mark D P; Naduvilath, Thomas J; Vaddavalli, Pravin K; Holden, Brien A; Ozkan, Jerome; Zhu, Hua

    2010-11-01

    To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

  3. Dynamics of soil organic carbon and microbial biomass carbon in relation to water erosion and tillage erosion.

    Science.gov (United States)

    Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

    2013-01-01

    Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the (137)Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of (137)Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. (137)Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion.

  4. Integration of transport concepts for risk assessment of pesticide erosion.

    Science.gov (United States)

    Yang, Xiaomei; Van Der Zee, Sjoerd E A T M; Gai, Lingtong; Wesseling, Jan G; Ritsema, Coen J; Geissen, Violette

    2016-05-01

    Environmental contamination by agrochemicals has been a large problem for decades. Pesticides are transported in runoff and remain attached to eroded soil particles, posing a risk to water and soil quality and human health. We have developed a parsimonious integrative model of pesticide displacement by runoff and erosion that explicitly accounts for water infiltration, erosion, runoff, and pesticide transport and degradation in soil. The conceptual framework was based on broadly accepted assumptions such as the convection-dispersion equation and lognormal distributions of soil properties associated with transport, sorption, degradation, and erosion. To illustrate the concept, a few assumptions are made with regard to runoff in relatively flat agricultural fields: dispersion is ignored and erosion is modelled by a functional relationship. A sensitivity analysis indicated that the total mass of pesticide associated with soil eroded by water scouring increased with slope, rain intensity, and water field capacity of the soil. The mass of transported pesticide decreased as the micro-topography of the soil surface became more distinct. The timing of pesticide spraying and rate of degradation before erosion negatively affected the total amount of transported pesticide. The mechanisms involved in pesticide displacement, such as runoff, infiltration, soil erosion, and pesticide transport and decay in the topsoil, were all explicitly accounted for, so the mathematical complexity of their description can be high, depending on the situation. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Sediment Transport and erosion modeling at Heaundae Beach in Korea.

    Science.gov (United States)

    Do, K.; Yoo, J.; McCall, R. T.

    2016-12-01

    The sand pocket beaches with two headlands are global features, but it's not easy to predict berm and dune erosion due to alongshore variation of water depth. This study investigates the sediment transport and morphological change using available wave and beach profile data, as well as to assess the applicability of the XBeach morphological model (Roelvink et al., 2009). The Haeundae is small pocket beach, 1.4 km long, located in the southern corner of the Korean Peninsula. The Korea Institute of Ocean Science and Technology (KIOST) measured beach profile along 27 survey lines. The beach profiles were surveyed five times from 17 June 2014 to 10 October 2014. For this duration, a wave gauge (AWAC) was installed at a depth about 23 m off the coast of Haeundae Beach. Severe four storms attacked Haeundae Beach for this duration and these storms lasted about 1 2 days with a peak significant wave height of 2.5 4.0 m. The placed sand is fairly sorted and its median diameter is 0.23 mm. 2DH coastal morphological model, XBeach developed to simulate dune erosion due to storm impacts. The model is based on the nonlinear shallow water equation and resolves nearshore hydrodynamics by employing a 2DH description of wave groups and infragravity motions. In this study, the numerical model XBeach was compared with the field data and used to estimate the sediment transport pattern on the sand pocket beach. The numerical model resulted in a comparable prediction in the west-part, but the east-part cannot reproduce the erosion and accretion of the sand, partly due to complex bathymetry and the lack of sediment. This limitation needs to be improved to use measured sand thickness data in future study

  6. Comparative Study of Microbial Activity and Chemical Properties of Soil by Implementing Anti-erosion Measure Vertical Mulching with Organic Residues

    Directory of Open Access Journals (Sweden)

    Gergana Slavova Kuncheva

    2015-01-01

    Full Text Available Water soil erosion is a phenomenon in which soil particles are separated transported and translocated by the action of rain water. Removal of topsoil by water flow leads to a decrease of humus in the soil, deterioration of soil structure, compaction, and reduction of microbial activity.Developed and tested have been number of methods and technologies for soil protection from the effects of water erosion. Such technology is vertical mulching, and straw or compost applied as mulching material.This work is a study of the changes that occur in some soil chemical properties and soil microbiological activity, as a result in the implementation of anti-erosion measure vertical mulching with different mulching materials for growing corn and wheat grain on carbonate chernozem, on sloping agricultural lands.

  7. Divergent taxonomic and functional responses of microbial communities to field simulation of aeolian soil erosion and deposition.

    Science.gov (United States)

    Ma, Xingyu; Zhao, Cancan; Gao, Ying; Liu, Bin; Wang, Tengxu; Yuan, Tong; Hale, Lauren; Nostrand, Joy D Van; Wan, Shiqiang; Zhou, Jizhong; Yang, Yunfeng

    2017-08-01

    Aeolian soil erosion and deposition have worldwide impacts on agriculture, air quality and public health. However, ecosystem responses to soil erosion and deposition remain largely unclear in regard to microorganisms, which are the crucial drivers of biogeochemical cycles. Using integrated metagenomics technologies, we analysed microbial communities subjected to simulated soil erosion and deposition in a semiarid grassland of Inner Mongolia, China. As expected, soil total organic carbon and plant coverage were decreased by soil erosion, and soil dissolved organic carbon (DOC) was increased by soil deposition, demonstrating that field simulation was reliable. Soil microbial communities were altered (p soil erosion and deposition, with dramatic increase in Cyanobacteria related to increased stability in soil aggregates. amyA genes encoding α-amylases were specifically increased (p = .01) by soil deposition and positively correlated (p = .02) to DOC, which likely explained changes in DOC. Surprisingly, most of microbial functional genes associated with carbon, nitrogen, phosphorus and potassium cycling were decreased or unaltered by both erosion and deposition, probably arising from acceleration of organic matter mineralization. These divergent responses support the necessity to include microbial components in evaluating ecological consequences. Furthermore, Mantel tests showed strong, significant correlations between soil nutrients and functional structure but not taxonomic structure, demonstrating close relevance of microbial function traits to nutrient cycling. © 2017 John Wiley & Sons Ltd.

  8. Modeling soil erosion and transport on forest landscape

    Science.gov (United States)

    Ge Sun; Steven G McNulty

    1998-01-01

    Century-long studies on the impacts of forest management in North America suggest sediment can cause major reduction on stream water quality. Soil erosion patterns in forest watersheds are patchy and heterogeneous. Therefore, patterns of soil erosion are difficult to model and predict. The objective of this study is to develop a user friendly management tool for land...

  9. A field experiment on the controls of sediment transport on bedrock erosion

    Science.gov (United States)

    Beer, A. R.; Turowski, J. M.; Fritschi, B.; Rieke-Zapp, D.; Campana, L.; Lavé, J.

    2012-12-01

    The earth`s surface is naturally shaped by interactions of physical and chemical processes. In mountainous regions with steep topography river incision fundamentally controls the geomorphic evolution of the whole landscape. There, erosion of exposed bedrock sections by fluvial sediment transport is an important mechanism forming mountain river channels. The links between bedload transport and bedrock erosion has been firmly established using laboratory experiments. However, there are only few field datasets linking discharge, sediment transport, impact energy and erosion that can be used for process understanding and model evaluation. To fill this gap, a new measuring setup has been commissioned to raise an appropriate simultaneous dataset of hydraulics, sediment transport and bedrock erosion at high temporal and spatial resolution. Two natural stone slabs were installed flush with the streambed of the Erlenbach, a gauged stream in the Swiss Pre-Alps. They are mounted upon force sensors recording vertical pressure und downstream shear caused by passing sediment particles. The sediment transport rates can be assessed using geophone plates and an automated moving basket system taking short-term sediment samples. These devices are located directly downstream of the stone slabs. Bedrock erosion rates are measured continuously with erosion sensors at sub-millimeter accuracy at three points on each slab. In addition, the whole slab topography is surveyed with photogrammetry and a structured-light 3D scanner after individual flood events. Since the installation in 2011, slab bedrock erosion has been observed during several transport events. We discuss the relation between hydraulics, bedload transport, resulting pressure forces on the stone slabs and erosion rates. The aim of the study is the derivation of an empirical process law for fluvial bedrock erosion driven by moving sediment particles.

  10. Improved Soil Erosion and Sediment Transport in GSSHA

    Science.gov (United States)

    2010-08-01

    the USLE soil erodibility factor (0-1), soil cropping factor (0-1) and conservation factor (0-1) in the development by Julien (1995). The use of one...factor K represents a departure from Julien (1995), who used all three factors from the Universal Soil Loss Equation ( USLE ). This departure is justi...runoff using a research-quality data set. BACKGROUND: GSSHA simulates overland soil erosion and outputs erosion and deposition for any size class of

  11. Changes in soil erosion and sediment transport based on the RUSLE model in Zhifanggou watershed, China

    Science.gov (United States)

    Wang, Lei; Qian, Ju; Qi, Wen-Yan; Li, Sheng-Shuang; Chen, Jian-Long

    2018-04-01

    In this paper, changes of sediment yield and sediment transport were assessed using the Revised Universal Soil Loss Equation (RUSLE) and Geographical Information Systems (GIS). This model was based on the integrated use of precipitation data, Landsat images in 2000, 2005 and 2010, terrain parameters (slope gradient and slope length) and soil composition in Zhifanggou watershed, Gansu Province, Northwestern China. The obtained results were basically consistent with the measured values. The results showed that the mean modulus of soil erosion is 1224, 1118 and 875 t km-2 yr-1 and annual soil loss is 23 130, 21 130 and 16 536 in 2000, 2005 and 2010 respectively. The measured mean erosion modulus were 1581 and 1377 t km-2 yr-1, and the measured annual soil loss were 29 872 and 26 022 t in 2000 and 2005. From 2000 to 2010, the amount of soil erosion was reduced yearly. Very low erosion and low erosion dominated the soil loss status in the three periods, and moderate erosion followed. The zones classified as very low erosion were increasing, whereas the zones with low or moderate erosion were decreasing. In 2010, no zones were classified as high or very high soil erosion.

  12. Modeling of soil erosion and sediment transport in the East River Basin in southern China

    Science.gov (United States)

    Wu, Yping; Chen, Ji

    2012-01-01

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  13. Modeling of soil erosion and sediment transport in the East River Basin in southern China.

    Science.gov (United States)

    Wu, Yiping; Chen, Ji

    2012-12-15

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide. Published by Elsevier B.V.

  14. Formulating Fine to Medium Sand Erosion for Suspended Sediment Transport Models

    Directory of Open Access Journals (Sweden)

    François Dufois

    2015-08-01

    Full Text Available The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the model’s capacity to simulate sand transport rates for a large range of current and wave conditions and sand diameters in the range 100–500 μm. Measured transport rates were predicted within a factor two in 67% of cases with current only and in 35% of cases with both waves and current. In comparison with the results obtained by Camenen and Larroudé (2003, who provided the same indicators for several practical transport rate formulations (whose means are respectively 72% and 37%, the proposed approach gives reasonable results. Before fitting a new erosion law to our model, classical erosion rate formulations were tested but led to poor comparisons with expected sediment transport rates. We suggest that classical erosion laws should be used with care in advection/diffusion models similar to ours, and that at least a full validation procedure for transport rates involving a range of sand diameters and hydrodynamic conditions should be carried out.

  15. Development of regional scale soil erosion and sediment transport model; its calibration and validations

    International Nuclear Information System (INIS)

    Rehman, M.H.; Akhtar, M.N.

    2005-01-01

    Despite of the fact that many soil erosion models have been developed in the past more than 5 decades including empirical based models like USLE and RUSLE and many process based soil erosion and sediment transport models like WEPP, EUROSEM and SHETRAN, the application of these models to regional scales remained questionable. To address the problem, a process-based soil erosion and sediment transport model has been developed to estimate the soil erosion, deposition, transport and sediment yield at regional scale. The soil erosion processes are modeled as the detachment of soil by the raindrop impact over the entire grid and detachment of soil due to overland flow only within the equivalent channels, whereas sediment is routed to the forward grid considering the transport capacity of the flow. The loss of heterogeneity in the spatial information of the topography due to slope averaging effect is reproduced by adapting a Fractal analysis approach. The model has been calibrated for Nan river basin (N.13A) and validated to the Yom river basin (Y.6) and Nam Mae Klang river basin (P.24A) of Thailand, simulated results show good agreements with the observed sediment discharge data. The developed model with few new components can also be applied for predicting the sediment discharges of the river Indus. (author)

  16. Cambrian rivers and floodplains: the significance of microbial cementation, groundwater and aeolian sediment transport

    Science.gov (United States)

    Reesink, A. J. H.; Best, J.; Freiburg, J. T.; Nathan, W.

    2016-12-01

    Rivers that existed before land plants colonized the Earth are commonly considered to be unaffected by microbial activity on their floodplains, because the limited cementation produced by microbial activity is insufficient to stabilize the river banks. Although this assumption is likely correct, such emphasis on channel dynamics ignores the potential role of floodplain dynamics as an integral component of the river system. Detailed analysis of cores from the Cambrian Mount Simon Sandstone, Illinois, suggests that a significant proportion of the terrestrial sequence is composed of flat-bedded `crinkly' structures that provide evidence of cementation by soil crusts and microbial biofilms, and that promoted the adhesion of sediment to sticky surfaces. Wind ripples and local desert pavements were abundant. These findings highlight that sediment deposition on Cambrian floodplains was often dominated by wind in locations where the ground water table reached the surface, and was thus likely independent of sediment transport within the river channel. Erosion by wind would thus have been hindered by surface cementation and the formation of desert pavements. Such ground water control on deposition, and resistance to erosion by floodplain surface hardening, appear to have been the primary controls on Cambrian floodplain topography. Because floodplain topography poses a key control on channel and floodplain flow, these processes may have affected patterns of erosion and deposition, as well as reach-scale dynamics such as channel avulsions. The autonomous operation of wind-and-groundwater controlled floodplains makes pre-vegetated river systems more sensitive to climatic conditions such as precipitation and evaporation, and strikingly different from those that occurred after the development of land plants.

  17. Analysis of erosion and transport of carbon impurity in the TFTR inner bumper limiter region

    International Nuclear Information System (INIS)

    Hua, T.Q.; Brooks, J.N.

    1992-01-01

    Carbon sputtering and transport on the TFTR inner graphite bumper limiter is investigated with the impurity transport code REDEP. Analysis is carried out for a series of ohmic discharges in TFTR. Predictions for Z eff in the core plasma agree well with in-situ experimental measurements. Run-away self-sputtering of carbon is predicted at low densities and high edge plasma temperatures when the limiter surface was purged of deuterium. Surface erosion and deposition is analyzed. In general, redeposition reduces the peak erosion by about a factor of five. Analysis is also carried out for a typical neutral beam heated discharge with a noncircular plasma. Spatial surface erosion and deposition profiles are compared qualitatively with beta backscattering measurements of metal deposition found on the limiter

  18. Simulation of tungsten erosion and transport near the divertor plate during ELMs by a kinetic method

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhenyue; Sang, Chaofeng; Hu, Wanpeng; Du, Hailong; Wang, Dezhen, E-mail: wangdez@dlut.edu.cn

    2016-11-01

    Highlights: • A kinetic method is used to simulate tungsten erosion and transport during ELMs. • The erosion of tungsten plate by different species (deuterium and carbon ions) is shown. • The charge states of sputtered tungsten particles are given statistically. - Abstract: Tungsten (W) is fore seen as one of the most important candidates of the plasma-facing materials (PFM) for future fusion devices, due to its beneficial properties. However, the high-Z characteristic makes it a potential contamination to the core plasma. Divertor is the main component that directly contacts the plasma, therefore, it is very important to understand the erosion of W divertor plate and the corresponding transport of the eroded wall impurity, especially during edge localized modes (ELMs). In this work, a one-dimension-in-space and three-dimensions-in-velocity particle-in-cell code (EPPIC1D) is used to simulate the erosion of W divertor plate, and the transport of eroded W impurity near the divertor plate is studied by a Monte Carlo code. Benefiting from the kinetic simulation, energy/particle flux to the target could be calculated accurately, and the erosion of W plate by different species is simulated during ELMs. The trajectories and distributions of eroded W impurity particles are demonstrated, which shows us a basic idea of how these impurity particles are generated and transported. It is found that C{sup 3+} plays a dominated role on the erosion of W divertor plate during ELMs even when its concentration is low. Both W atoms and ions distribute mainly near the divertor plate, indicating only a very small fraction of W impurity particles could escape from divertor region and penetrate into the core plasma.

  19. Short-term transport of glyphosate with erosion in Chinese loess soil - a flume experiment

    NARCIS (Netherlands)

    Yang, X.; Wang, Fei; Martins Bento, Celia; Xue, Sha; Gai, L.; Dam, van R.C.J.; Mol, J.G.J.; Ritsema, C.J.; Geissen, V.

    2015-01-01

    Repeated applications of glyphosate may contaminate the soil and water and threaten their quality both within the environmental system and beyond it through water erosion related processes and leaching. In this study, we focused on the transport of glyphosate and its metabolite aminomethylphosphonic

  20. Decay characteristics and erosion-related transport of glyphosate in Chinese loess soil under field conditions

    NARCIS (Netherlands)

    Yang, X.; Wang, Fei; Martins Bento, Celia; Meng, L.; Dam, van R.C.J.; Mol, J.G.J.; Liu, Guobin; Ritsema, C.J.; Geissen, V.

    2015-01-01

    The decay characteristics and erosion-related transport of glyphosate and aminomethylphosphonic acid (AMPA) were monitored for 35 d at different slope gradients and rates of application in plots with loess soil on the Loess Plateau, China. The initial glyphosate decayed rapidly (half-life of 3.5 d)

  1. Structural practices for controlling sediment transport from erosion

    Science.gov (United States)

    Gabriels, Donald; Verbist, Koen; Van de Linden, Bruno

    2013-04-01

    Erosion on agricultural fields in the hilly regions of Flanders, Belgium has been recognized as an important economical and ecological problem that requires effective control measures. This has led to the implementation of on-site and off-site measures such as reduced tillage and the installation of grass buffers trips, and dams made of vegetative materials. Dams made out of coir (coconut) and wood chips were evaluated on three different levels of complexity. Under laboratory conditions, one meter long dams were submitted to two different discharges and three sediment concentrations under two different slopes, to assess the sediment delivery ratios under variable conditions. At the field scale, discharge and sediment concentrations were monitored under natural rainfall conditions on six 3 m wide plots, of which three were equipped with coir dams, while the other three served as control plots. The same plots were also used for rainfall simulations, which allowed controlling sediment delivery boundary conditions more precisely. Results show a clear advantage of these dams to reduce discharge by minimum 49% under both field and laboratory conditions. Sediment delivery ratios (SDR) were very small under laboratory and field rainfall simulations (4-9% and 2% respectively), while larger SDRs were observed under natural conditions (43%), probably due to the small sediment concentrations (1-5 g l-1) observed and as such a larger influence of boundary effects. Also a clear enrichment of larger sand particles (+167%) could be observed behind the dams, showing a significant selective filtering effect.

  2. Development of a transport model for the microbial degradation of ...

    African Journals Online (AJOL)

    A mathematical model for first order reaction rate under isothermal condition was developed for predicting the diffusivity and transport rate of anthracene and pyrene during biodegradation using two microbial strains (corynebacteria spp and pseudomonas putida) in a heterogeneous porous medium. The formulation ...

  3. Integration of transport concepts for risk assessment of pesticide erosion

    NARCIS (Netherlands)

    Yang, Xiaomei; Zee, van der Sjoerd E.A.T.M.; Gai, Lingtong; Wesseling, Jan G.; Ritsema, Coen J.; Geissen, Violette

    2016-01-01

    Environmental contamination by agrochemicals has been a large problem for decades. Pesticides are transported in runoff and remain attached to eroded soil particles, posing a risk to water and soil quality and human health. We have developed a parsimonious integrative model of pesticide

  4. Development and application of the microbial fate and transport module for the Agricultural Policy/Environmental eXtender (APEX) model

    Science.gov (United States)

    Hong, E.; Park, Y.; Muirhead, R.; Jeong, J.; Pachepsky, Y. A.

    2017-12-01

    Pathogenic microorganisms in recreational and irrigation waters remain the subject of concern. Water quality models are used to estimate microbial quality of water sources, to evaluate microbial contamination-related risks, to guide the microbial water quality monitoring, and to evaluate the effect of agricultural management on the microbial water quality. The Agricultural Policy/Environmental eXtender (APEX) is the watershed-scale water quality model that includes highly detailed representation of agricultural management. The APEX currently does not have microbial fate and transport simulation capabilities. The objective of this work was to develop the first APEX microbial fate and transport module that could use the APEX conceptual model of manure removal together with recently introduced conceptualizations of the in-stream microbial fate and transport. The module utilizes manure erosion rates found in the APEX. Bacteria survival in soil-manure mixing layer was simulated with the two-stage survival model. Individual survival patterns were simulated for each manure application date. Simulated in-stream microbial fate and transport processes included the reach-scale passive release of bacteria with resuspended bottom sediment during high flow events, the transport of bacteria from bottom sediment due to the hyporheic exchange during low flow periods, the deposition with settling sediment, and the two-stage survival. Default parameter values were available from recently published databases. The APEX model with the newly developed microbial fate and transport module was applied to simulate seven years of monitoring data for the Toenepi watershed in New Zealand. Based on calibration and testing results, the APEX with the microbe module reproduced well the monitored pattern of E. coli concentrations at the watershed outlet. The APEX with the microbial fate and transport module will be utilized for predicting microbial quality of water under various agricultural

  5. Microbial transport : Adaptations to natural environments

    NARCIS (Netherlands)

    Konings, W.N

    2006-01-01

    The cytoplasmic membrane of bacteria is the matrix for metabolic energy transducing processes such as proton motive force generation and solute transport. Passive permeation of protons across the cytoplasmic membrane is a crucial determinant in the proton motive generating capacity of the organisms.

  6. Microbial transport : Adaptations to natural environments

    NARCIS (Netherlands)

    Konings, W.N

    The cytoplasmic membrane of bacteria is the matrix for metabolic energy transducing processes such as proton motive force generation and solute transport. Passive permeation of protons across the cytoplasmic membrane is a crucial determinant in the proton motive generating capacity of the organisms.

  7. Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications

    Directory of Open Access Journals (Sweden)

    Mohammad Hajigholizadeh

    2018-03-01

    Full Text Available The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability.

  8. Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications.

    Science.gov (United States)

    Hajigholizadeh, Mohammad; Melesse, Assefa M; Fuentes, Hector R

    2018-03-14

    The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid) is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability.

  9. Managing erosion, sediment transport and water quality in drained peatland catchments

    Energy Technology Data Exchange (ETDEWEB)

    Marttila, H.

    2010-07-01

    Peatland drainage changes catchment conditions and increases the transport of suspended solids (SS) and nutrients. New knowledge and management methods are needed to reduce SS loading from these areas. This thesis examines sediment delivery and erosion processes in a number of peatland drainage areas and catchments in order to determine the effects of drainage on sediment and erosion dynamics and mechanics. Results from studies performed in peat mining, peatland forestry and disturbed headwater catchments in Finland are presented and potential sediment load management methods are discussed for drainage areas and headwater brooks. Particular attention is devoted to erosion of organic peat, sediment transport and methods to reduce the impacts of peatland drainage in boreal headwaters. This thesis consists of six articles. The first and second papers focus on the erosion and sediment transport processes at peat harvesting and peatland forestry drainage networks. The results indicate that in-channel processes are important in drained peatland, since the drainage network often constitutes temporary inter-storm storage for eroding and transporting material. Sediment properties determine the bed sediment erosion sensitivity, as fluffy organic peat sediment consolidates over time. As flashiness and peak runoff control sediment entrainment and transport from drained peatland areas, water quality management should include peak runoff management. The third, fourth and fifth papers studies use and application of peak runoff control (PRC) method to the peat harvesting and peatland forestry conditions for water protection. Results indicate that effective water quality management in drained peatland areas can be achieved using this method. Installation of the PRC structures is a useful and cost-effective way of storing storm runoff waters temporarily in the ditch system and providing a retention time for eroded sediment to settle to the ditch bed and drainage network. The main

  10. A Stochastic Multi-Media Model of Microbial Transport in Watersheds

    Science.gov (United States)

    Yeghiazarian, L.; Safwat, A.; Whiteaker, T.; Teklitz, A.; Nietch, C.; Maidment, D. R.; Best, E. P.

    2012-12-01

    Fecal contamination is the leading cause of surface-water impairment in the US, and fecal pathogens are capable of triggering massive outbreaks of gastrointestinal disease. The difficulty in prediction of water contamination has its roots in the stochastic variability of fecal pathogens in the environment, and in the complexity of microbial dynamics and interactions on the soil surface and in water. To address these challenges, we have developed a stochastic model whereby the transport of microorganisms in watersheds is considered in two broad categories: microorganisms that are attached to mineral or organic substrates in suspended sediment; and unattached microorganisms suspended in overland flow. The interactions of microorganisms with soil particles on the soil surface and in the overland flow lead to transitions of microorganisms between solid and aqueous media. The strength of attachment of microorganisms to soil particles is determined by the chemical characteristics of soils which are highly correlated with the particle size. The particle size class distribution in the suspended sediment is predicted by the Water Erosion Prediction Project (WEPP). The model is integrated with ArcGIS, resulting in a general transport-modeling framework applicable to a variety of biological and chemical surface water contaminants. Simulations are carried out for a case study of contaminant transport in the East Fork Little Miami River Watershed in Ohio. Model results include the spatial probability distribution of microbes in the watershed and can be used for assessment of (1) mechanisms dominating microbial transport, and (2) time and location of highest likelihood of microbial occurrence, thus yielding information on best water sampling strategies.

  11. Particle transport patterns of short-distance soil erosion by wind-driven rain, rain and wind

    Science.gov (United States)

    Marzen, Miriam; Iserloh, Thomas; de Lima, João L. M. P.; Ries, Johannes B.

    2015-04-01

    Short distance erosion of soil surface material is one of the big question marks in soil erosion studies. The exact measurement of short-distance transported soil particles, prior to the occurrence of overland flow, is a challenge to soil erosion science due to the particular requirements of the experimental setup and test procedure. To approach a quantification of amount and distance of each type of transport, we applied an especially developed multiple-gutter system installed inside the Trier Portable Wind and Rainfall Simulator (PWRS). We measured the amount and travel distance of soil particles detached and transported by raindrops (splash), wind-driven rain (splash-saltation and splash-drift) and wind (saltation). The test setup included three different erosion agents (rain/ wind-driven rain/ wind), two substrates (sandy/ loamy), three surface structures (grain roughness/ rills lengthwise/ rills transversal) and three slope angles (0°/+7°/-7°). The results present detailed transport patterns of the three erosion agents under the varying soil and surface conditions up to a distance of 1.6 m. Under the applied rain intensity and wind velocity, wind-driven rain splash generates the highest erosion. The erodibility and travel distance of the two substrates depend on the erosion agent. The total erosion is slightly higher for the slope angle -7° (downslope), but for wind-driven rain splash, the inclination is not a relevant factor. The effect of surface structures (rills) changes with traveling distance. The wind driven rain splash generates a much higher amount of erosion and a further travel distance of the particles due to the combined action of wind and rain. The wind-driven rain factor appears to be much more significant than the other factors. The study highlights the effects of different erosion agents and surface parameters on short-distance particle transport and the powerful impact of wind-driven rain on soil erosion.

  12. Applying transport-distance specific SOC distribution to calibrate soil erosion model WaTEM

    Science.gov (United States)

    Hu, Yaxian; Heckrath, Goswin J.; Kuhn, Nikolaus J.

    2016-04-01

    Slope-scale soil erosion, transport and deposition fundamentally decide the spatial redistribution of eroded sediments in terrestrial and aquatic systems, which further affect the burial and decomposition of eroded SOC. However, comparisons of SOC contents between upper eroding slope and lower depositional site cannot fully reflect the movement of eroded SOC in-transit along hillslopes. The actual transport distance of eroded SOC is decided by its settling velocity. So far, the settling velocity distribution of eroded SOC is mostly calculated from mineral particle specific SOC distribution. Yet, soil is mostly eroded in form of aggregates, and the movement of aggregates differs significantly from individual mineral particles. This urges a SOC erodibility parameter based on actual transport distance distribution of eroded fractions to better calibrate soil erosion models. Previous field investigation on a freshly seeded cropland in Denmark has shown immediate deposition of fast settling soil fractions and the associated SOC at footslopes, followed by a fining trend at the slope tail. To further quantify the long-term effects of topography on erosional redistribution of eroded SOC, the actual transport-distance specific SOC distribution observed on the field was applied to a soil erosion model WaTEM (based on USLE). After integrating with local DEM, our calibrated model succeeded in locating the hotspots of enrichment/depletion of eroded SOC on different topographic positions, much better corresponding to the real-world field observation. By extrapolating into repeated erosion events, our projected results on the spatial distribution of eroded SOC are also adequately consistent with the SOC properties in the consecutive sample profiles along the slope.

  13. Short-term transport of glyphosate with erosion in Chinese loess soil--a flume experiment.

    Science.gov (United States)

    Yang, Xiaomei; Wang, Fei; Bento, Célia P M; Xue, Sha; Gai, Lingtong; van Dam, Ruud; Mol, Hans; Ritsema, Coen J; Geissen, Violette

    2015-04-15

    Repeated applications of glyphosate may contaminate the soil and water and threaten their quality both within the environmental system and beyond it through water erosion related processes and leaching. In this study, we focused on the transport of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) related to soil erosion at two slope gradients (10 and 20°), two rates of pesticide with a formulation of glyphosate (Roundup®) application (360 and 720 mg m(-2)), and a rain intensity of 1.0 mm min(-1) for 1 h on bare soil in hydraulic flumes. Runoff and erosion rate were significantly different within slope gradients (psoil at the end of the experiment decreased significantly with depth (psoil layers, respectively. The risk of contamination in deep soil and the groundwater was thus low, but 5% of the initial application did reach the 2-10 cm soil layer. The risk of contamination of surface water through runoff and sedimentation, however, can be considerable, especially in regions where rain-induced soil erosion is common. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Transport mechanisms of soil-bound mercury in the erosion process during rainfall-runoff events.

    Science.gov (United States)

    Zheng, Yi; Luo, Xiaolin; Zhang, Wei; Wu, Xin; Zhang, Juan; Han, Feng

    2016-08-01

    Soil contamination by mercury (Hg) is a global environmental issue. In watersheds with a significant soil Hg storage, soil erosion during rainfall-runoff events can result in nonpoint source (NPS) Hg pollution and therefore, can extend its environmental risk from soils to aquatic ecosystems. Nonetheless, transport mechanisms of soil-bound Hg in the erosion process have not been explored directly, and how different fractions of soil organic matter (SOM) impact transport is not fully understood. This study investigated transport mechanisms based on rainfall-runoff simulation experiments. The experiments simulated high-intensity and long-duration rainfall conditions, which can produce significant soil erosion and NPS pollution. The enrichment ratio (ER) of total mercury (THg) was the key variable in exploring the mechanisms. The main study findings include the following: First, the ER-sediment flux relationship for Hg depends on soil composition, and no uniform ER-sediment flux function exists for different soils. Second, depending on soil composition, significantly more Hg could be released from a less polluted soil in the early stage of large rainfall events. Third, the heavy fraction of SOM (i.e., the remnant organic matter coating on mineral particles) has a dominant influence on the enrichment behavior and transport mechanisms of Hg, while clay mineral content exhibits a significant, but indirect, influence. The study results imply that it is critical to quantify the SOM composition in addition to total organic carbon (TOC) for different soils in the watershed to adequately model the NPS pollution of Hg and spatially prioritize management actions in a heterogeneous watershed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Erosion, Transportation, and Deposition on Outer Solar System Satellites: Landform Evolution Modeling Studies

    Science.gov (United States)

    Moore, Jeffrey Morgan; Howard, Alan D.; Schenk, Paul M.

    2013-01-01

    Mass movement and landform degradation reduces topographic relief by moving surface materials to a lower gravitational potential. In addition to the obvious role of gravity, abrasive mechanical erosion plays a role, often in combination with the lowering of cohesion, which allows disaggregation of the relief-forming material. The identification of specific landform types associated with mass movement and landform degradation provides information about local sediment particle size and abundance and transportation processes. Generally, mass movements can be classified in terms of the particle sizes of the transported material and the speed the material moved during transport. Most degradation on outer planet satellites appears consistent with sliding or slumping, impact erosion, and regolith evolution. Some satellites, such as Callisto and perhaps Hyperion and Iapetus, have an appearance that implies that some additional process is at work, most likely sublimation-driven landform modification and mass wasting. A variant on this process is thermally driven frost segregation as seen on all three icy Galilean satellites and perhaps elsewhere. Titan is unique among outer planet satellites in that Aeolian and fluvial processes also operate to erode, transport, and deposit material. We will evaluate the sequence and extent of various landform-modifying erosional and volatile redistribution processes that have shaped these icy satellites using a 3-D model that simulates the following surface and subsurface processes: 1) sublimation and re-condensation of volatiles; 2) development of refractory lag deposits; 3) disaggregation and downward sloughing of surficial material; 4) radiative heating/cooling of the surface (including reflection, emission, and shadowing by other surface elements); 5) thermal diffusion; and 6) vapor diffusion. The model will provide explicit simulations of landform development and thusly predicts the topographic and volatile evolution of the surface

  16. Quantification of soil erosion and transport processes in the in the Myjava Hill Land

    Science.gov (United States)

    Hlavcová, Kamila; Kohnová, Silvia; Velisková, Yvetta; Studvová, Zuzana; Socuvka, Valentin; Németová, Zuzana; Duregová, Maria

    2017-04-01

    The aim of the study is a complex analysis of soil erosion processes and proposals for erosion control in the region of the Myjava Hill Land located in western Slovakia. The Myjava Hill Land is characteristic of quick runoff response, intensive soil erosion by water and related muddy floods, which are determined by both natural and socio-economic conditions. In this paper a case study in the Svacenický Creek catchment, with a focus on the quantification of soil loss from the agriculturally arable lands and sediment transport to the dry water reservoir (polder) of the Svacenický Creek is presented. Erosion, sediment transport, and the deposition of sediments in the water reservoir represent a significant impact on its operation, mainly with regard to reducing its accumulation volume. For the analysis of the soil loss and sediment transport from the Svacenický Creek catchment, the Universal Soil Loss Equation, the USLE 2D, and the Sediment Delivery Ratio (SDR) models were applied. Because the resulting values of the soil loss exceeded the values of the tolerated soil loss, erosion control measures by strip cropping were designed. Strip cropping is based on altering crop strips with protective (infiltration) strips. The effectiveness of the protective (infiltration) strips for reducing runoff from the basin by the SCS-CN method was estimated. Monitoring the morphological parameters of bottom sediments and their changes over time is crucial information in the field of water reservoir operations. In September 2015, the AUV EcoMapper was used to gather the data information on the Svacenický Creek reservoir. The data includes information about the sediment depths and parameters of the water quality. The results of the surveying are GIS datasets and maps, which provide a higher resolution of the bathymetric data and contours of the bottom reservoir. To display the relief of the bottom, the ArcMap 10.1. software was used. Based on the current status of the bottom

  17. [Sediment transport characteristics at different erosion stages for non-hardened roads of the Shenfu Coalfield, west China].

    Science.gov (United States)

    Guo, Ming-ming; Wang, Wen-long; Li, Jian-ming; Huang, Peng-fei; Zhu, Bao-cai; Wang, Zhen; Luo, Ting

    2015-02-01

    Non-hardened roads formed in the production of the Shenfu Coalfield have a unique condition of underlying surface. The road surface is composed of a regolith layer with a certain thickness resulted from long-term rolling and thus, is characterized by weakened anti-scourabilty and anti-erodibility. In contrast, soil layer below the regolith has a higher bulk density and anti-erodibility. The processes of soil erosion on the non-hardened roads exhibit some differences under rainfall condition. The process of sediment transport and the relationship between sediment transport rate and erosion factors at different erosion stages were studied on non-hardened roads with slope degrees ranging from 3° to 12° (3°, 6°, 9°, 12°) by a field experiment under artificial rainfall. Results showed that the first peak of sediment transport on the regolith surface was observed at the sheet erosion stage. Sheet erosion occurred only at 3° slope degree, with an average variation coefficient of 0.07 for sediment transport rate. Rills in every testing began to develop at slope degrees of 6° to 12° about 15 min after runoff initiation. At the sheet erosion stage, the process of sediment transport fluctuated considerably at rainfall intensities of > 1.5 mm · min(-1), but the differences in its variation were little at the three slope degrees, with average variation coefficients of 0.20, 0.19 and 0.16, respectively. Rainfall intensity had a more significant impact on sediment transport rate than slope degree. The process of sediment transport at the rill erosion stage fluctuated, but the fluctuation was obviously smaller than that at the sheet erosion stage, with average variation coefficients of 0.05, 0.09 and 0.10 at the three slope degrees. Many wide and shallow rills evolved at the rill erosion stage. The sediment transport rate could be well predicted by a power function of rainfall intensity and slope degree at the sheet and rill erosion stages. The stable sediment transport

  18. A simplified 137Cs transport model for estimating erosion rates in undisturbed soil

    International Nuclear Information System (INIS)

    Zhang Xinbao; Long Yi; He Xiubin; Fu Jiexiong; Zhang Yunqi

    2008-01-01

    137 Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of 137 Cs fallout from atmosphere in 1963. 137 Cs fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The 137 Cs nuclide tracing technique has been used for assessment of soil losses for both undisturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the 137 Cs depth distribution in profile, where the maximum 137 Cs occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total 137 Cs fallout amount deposited on the earth surface in 1963 and the 137 Cs profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land. However, temporal variations of 137 Cs depth distribution in undisturbed soils after its deposition on the ground due to downward transport processes are not considered in the previous simple profile-shape model. Thus, the soil losses are overestimated by the model. On the base of the erosion assessment model developed by Walling, D.E., He, Q. [1999. Improved models for estimating soil erosion rates from cesium-137 measurements. Journal of Environmental Quality 28, 611-622], we discuss the 137 Cs transport process in the eroded soil profile and make some simplification to the model, develop a method to estimate the soil erosion rate more expediently. To compare the soil erosion rates calculated by the simple profile-shape model and the simple transport model, the soil losses related to different 137 Cs loss proportions of the reference inventory at the Kaixian site of the

  19. Impact of Microbial Growth on Subsurface Perfluoroalkyl Acid Transport

    Science.gov (United States)

    Weathers, T. S.; Higgins, C. P.; Sharp, J.

    2014-12-01

    The fate and transport of poly and perfluoroalkyl substances (PFASs) in the presence of active microbial communities has not been widely investigated. These emerging contaminants are commonly utilized in aqueous film-forming foams (AFFF) and have often been detected in groundwater. This study explores the transport of a suite of perfluorocarboxylic acids and perfluoroalkylsulfonates, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), in microbially active settings. Single point organic carbon normalized sorption coefficients derived by exposing inactive cellular material to PFASs result in more than an order of magnitude increase in sorption compared to soil organic carbon sorption coefficients found in literature. For example, the sorption coefficients for PFOS are 4.05±0.07 L/kg and 2.80±0.08 L/kg for cellular organic carbon and soil organic carbon respectively. This increase in sorption, coupled with enhanced extracellular polymeric substance production observed during growth of a common hydrocarbon degrading soil microbe exposed to source-level concentrations of PFASs (10 mg/L of 11 analytes, 110 mg/L total) may result in PFAS retardation in situ. To address the upscaling of this phenomenon, flow-through columns packed with low-organic carbon sediment and biostimulated with 10 mg/L glucose were exposed to PFAS concentrations from 15 μg/L to 10 mg/L of each 11 analytes. Breakthrough and tailing of each analyte was measured and modeled with Hydrus-1D to explore sorption coefficients over time for microbially active columns.

  20. Transport of silver nanoparticles by runoff and erosion - A flume experiment.

    Science.gov (United States)

    Mahdi, Karrar N M; Commelin, Meindert; Peters, Ruud J B; Baartman, Jantiene E M; Ritsema, Coen; Geissen, Violette

    2017-12-01

    Silver nanoparticles (AgNPs) are being used in many products as they have unique antimicrobial-biocidal properties. After disposal of these products AgNPs can reach the soil environment possibly affecting soil organisms and disrupting plants. This work aimed to study the transport of AgNPs by water and sediment during overland flow and soil erosion. This was done in a laboratory setting, using a flume and rainfall simulator. A low concentration of AgNPs (50μg·kg -1 ) was applied to two soil-flumes with slope percentages of 20% and 10%. The rainfall was applied in four events of 15min each with a total amount of rainfall of 15mm during each event. After applying the rainfall, samples of the non-transported background soil (BS) and the transported sediment (Sf) were collected from the flume surface. Runoff sediment (RS) and water (RW) were collected from the outlet. AgNPs were detected in all samples collected. However, concentration varied according to sample type (soil or water), time of collection (for runoff water and sediment) and the slope of the soil flume. Higher concentrations of AgNPs in soil were detected in the BS than in the Sf likely due to the BS having more fine particles (silt and clay). The AgNPs concentration in the runoff sediments increased with subsequent applied rain events. In addition, increasing the slope of the flume from 10% to 20% increased the total AgNPs transported with the runoff sediment by a factor 1.5. The study confirms that AgNPs can be transported by both overland flow and sediment due to erosion. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Lateral transport of soil carbon and land−atmosphere CO2 flux induced by water erosion in China

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-01-01

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land−atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y−1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y−1, equivalent to 8–37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m−2⋅y−1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty. PMID:27247397

  2. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China.

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G L; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-14

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y(-1) of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y(-1), equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the "hotspots," largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m(-2)⋅y(-1)), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  3. Development and evaluation of the microbial fate and transport module for the Agricultural Policy/Environmental eXtender (APEX) model

    Science.gov (United States)

    Hong, Eun-Mi; Park, Yongeun; Muirhead, Richard; Pachepsky, Yakov

    2017-04-01

    Pathogenic microorganisms in recreational and irrigation waters remain the subject of concern. Water quality models are used to estimate microbial quality of water sources, to evaluate microbial contamination-related risks, to guide the microbial water quality monitoring, and to evaluate the effect of agricultural management on the microbial water quality. The Agricultural Policy/Environmental eXtender (APEX) is the watershed-scale water quality model that includes highly detailed representation of agricultural management. The APEX currently does not have microbial fate and transport simulation capabilities. The objective of this work was to develop the first APEX microbial fate and transport module that could use the APEX conceptual model of manure removal together with recently introduced conceptualizations of the in-stream microbial fate and transport. The module utilizes manure erosion rates found in the APEX. The total number of removed bacteria was set to the concentrations of bacteria in soil-manure mixing layer and eroded manure amount. Bacteria survival in soil-manure mixing layer was simulated with the two-stage survival model. Individual survival patterns were simulated for each manure application date. Simulated in-stream microbial fate and transport processes included the reach-scale passive release of bacteria with resuspended bottom sediment during high flow events, the transport of bacteria from bottom sediment due to the hyporheic exchange during low flow periods, the deposition with settling sediment, and the two-stage survival. Default parameter values were available from recently published databases. The APEX model with the newly developed microbial fate and transport module was applied to simulate seven years of monitoring data for the Toenepi watershed in New Zealand. The stream network of the watershed ran through grazing lands with the daily bovine waste deposition. Based on calibration and testing results, the APEX with the microbe module

  4. A fast, parallel algorithm to solve the basic fluvial erosion/transport equations

    Science.gov (United States)

    Braun, J.

    2012-04-01

    Quantitative models of landform evolution are commonly based on the solution of a set of equations representing the processes of fluvial erosion, transport and deposition, which leads to predict the geometry of a river channel network and its evolution through time. The river network is often regarded as the backbone of any surface processes model (SPM) that might include other physical processes acting at a range of spatial and temporal scales along hill slopes. The basic laws of fluvial erosion requires the computation of local (slope) and non-local (drainage area) quantities at every point of a given landscape, a computationally expensive operation which limits the resolution of most SPMs. I present here an algorithm to compute the various components required in the parameterization of fluvial erosion (and transport) and thus solve the basic fluvial geomorphic equation, that is very efficient because it is O(n) (the number of required arithmetic operations is linearly proportional to the number of nodes defining the landscape), and is fully parallelizable (the computation cost decreases in a direct inverse proportion to the number of processors used to solve the problem). The algorithm is ideally suited for use on latest multi-core processors. Using this new technique, geomorphic problems can be solved at an unprecedented resolution (typically of the order of 10,000 X 10,000 nodes) while keeping the computational cost reasonable (order 1 sec per time step). Furthermore, I will show that the algorithm is applicable to any regular or irregular representation of the landform, and is such that the temporal evolution of the landform can be discretized by a fully implicit time-marching algorithm, making it unconditionally stable. I will demonstrate that such an efficient algorithm is ideally suited to produce a fully predictive SPM that links observationally based parameterizations of small-scale processes to the evolution of large-scale features of the landscapes on

  5. Sediment transport capacity for soil erosion modelling at hillslope scale: an experimental approach

    NARCIS (Netherlands)

    Ali, M.

    2012-01-01

    Soil erosion is a common global problem that has negative impacts on agriculture production, water storage facilities, water conveyance system, and water quality. To assess water erosion problems in catchments, scientists have developed several spatially distributed soil erosion models with

  6. Application of polyacrylamide (PAM) through lay-flat polyethylene 1 tubing: effects on infiltration, erosion, N and P transport, and corn yield

    Science.gov (United States)

    Polyacrylamides (PAMs), when applied as a soil amendment, purportedly improve soil infiltration, decrease erosion, and reduce off-site agrochemical transport. The effect of PAM on infiltration, erosion, agrochemical transport, and crop yield when applied in-furrow to Mid-South production systems has...

  7. Investigating erosion of building materials used in an installation for pneumatic transport of coke breeze and coal

    Energy Technology Data Exchange (ETDEWEB)

    Bandrowski, J.; Kot-Borkowska, Z.; Misztal, M.; Raczek, J.; Kaczmarzyk, G.

    1980-09-01

    This article investigates the influence of the following factors on erosion of building material used in pneumatic transport of coal and coke breeze: intensity of coal or coke breeze flow within the range of 47 to 120 kg/h for coke and 99 to 165 kg/h for coal; speed of solid material particles within the range 3.71 to 7.97 m/s for coke, and 3.30 to 7.58 m/s for coal; duration of the experiments 0.5 to 1.5 h for coke and 2.0 to 5.0 for coal; angle of inclination of the sample of building material 30 to 60 degrees for both coal and coke breeze. Three types of construction material used in pneumatic transport were tested: steel, concrete and chamotte bricks. Investigations show that concrete is characterized by the highest erosion, chamotte bricks by medium erosion and steel by the lowest erosion. As a result of mathematical processing of experimental data, empirical models of erosion of the three materials are constructed. (7 refs.)

  8. (210)Pb as a tracer of soil erosion, sediment source area identification and particle transport in the terrestrial environment.

    Science.gov (United States)

    Matisoff, Gerald

    2014-12-01

    Although (137)Cs has been used extensively to study soil erosion and particle transport in the terrestrial environment, there has been much less work using excess or unsupported (210)Pb ((210)Pbxs) to study the same processes. Furthermore, since (137)Cs activities in soils are decreasing because of radioactive decay, some locations have an added complication due to the addition of Chernobyl-derived (137)Cs, and the activities of (137)Cs in the southern hemisphere are low, there is a need to develop techniques that use (210)Pbxs to provide estimates of rates of soil erosion and particle transport. This paper reviews the current status of (210)Pbxs methods to quantify soil erosion rates, to identify and partition suspended sediment source areas, and to determine the transport rates of particles in the terrestrial landscape. Soil erosion rates determined using (210)Pbxs are based on the unsupported (210)Pb ((210)Pbxs) inventory in the soil, the depth distribution of (210)Pbxs, and a mass balance calibration ('conversion model') that relates the soil inventory to the erosion rate using a 'reference site' at which neither soil erosion nor soil deposition has occurred. In this paper several different models are presented to illustrate the effects of different model assumptions such as the timing, depth and rates of the surface soil mixing on the calculated erosion rates. The suitability of model assumptions, including estimates of the depositional flux of (210)Pbxs to the soil surface and the post-depositional mobility of (210)Pb are also discussed. (210)Pb can be used as one tracer to permit sediment source area identification. This sediment 'fingerprinting' has been extended far beyond using (210)Pb as a single radioisotope to include numerous radioactive and stable tracers and has been applied to identifying the source areas of suspended sediment based on underlying rock type, land use (roads, stream banks, channel beds, cultivated or uncultivated lands, pasture lands

  9. First ERO2.0 modeling of Be erosion and non-local transport in JET ITER-like wall

    Science.gov (United States)

    Romazanov, J.; Borodin, D.; Kirschner, A.; Brezinsek, S.; Silburn, S.; Huber, A.; Huber, V.; Bufferand, H.; Firdaouss, M.; Brömmel, D.; Steinbusch, B.; Gibbon, P.; Lasa, A.; Borodkina, I.; Eksaeva, A.; Linsmeier, Ch; Contributors, JET

    2017-12-01

    ERO is a Monte-Carlo code for modeling plasma-wall interaction and 3D plasma impurity transport for applications in fusion research. The code has undergone a significant upgrade (ERO2.0) which allows increasing the simulation volume in order to cover the entire plasma edge of a fusion device, allowing a more self-consistent treatment of impurity transport and comparison with a larger number and variety of experimental diagnostics. In this contribution, the physics-relevant technical innovations of the new code version are described and discussed. The new capabilities of the code are demonstrated by modeling of beryllium (Be) erosion of the main wall during JET limiter discharges. Results for erosion patterns along the limiter surfaces and global Be transport including incident particle distributions are presented. A novel synthetic diagnostic, which mimics experimental wide-angle 2D camera images, is presented and used for validating various aspects of the code, including erosion, magnetic shadowing, non-local impurity transport, and light emission simulation.

  10. Investigation of Soil Erosion and Phosphorus Transport within an Agricultural Watershed

    Science.gov (United States)

    Klik, A.; Jester, W.; Muhar, A.; Peinsitt, A.; Rampazzo, N.; Mentler, A.; Staudinger, B.; Eder, M.

    2003-04-01

    In a 40 ha agricultural used watershed in Austria, surface runoff, soil erosion and nutrient losses are measured spatially distributed with 12 small erosion plots. Crops during growing season 2002 are canola, corn, sunflower, winter wheat, winter barley, rye, sugar beets, and pasture. Canopy height and canopy cover are observed in 14-day intervals. Four times per year soil water content, shear stress and random roughness of the surface are measured in a 25 x 25 m grid (140 points). The same raster is sampled for soil texture analyses and content of different phosphorus fractions in the 0-10 cm soil depth. Spatially distributed data are used for geostatistical analysis. Along three transects hydrologic conditions of the hillslope position (top, middle, foot) are investigated by measuring soil water content and soil matrix potential. After erosive events erosion features (rills, deposition, ...) are mapped using GPS. All measured data will be used as input parameters for the Limburg Soil Erosion Model (LISEM).

  11. Minimization of gully erosion on reclaimed surface mines using the stable slope and sediment transport computer model

    International Nuclear Information System (INIS)

    McKenney, R.A.; Gardner, T.G.

    1992-01-01

    Disequilibrium between slope form and hydrologic and erosion processes on reclaimed surface coal mines in the humid temperate northeastern US, can result in gully erosion and sediment loads which are elevated above natural, background values. Initial sheetwash erosion is surpassed by gully erosion on reclamation sites which are not in equilibrium with post-mining hydrology. Long-term stability can be attained by designing a channel profile which is in equilibrium with the increased peak discharges found on reclaimed surface mines. The Stable Slope and Sediment transport model (SSAST) was developed to design stable longitudinal channel profiles for post-mining hydrologic and erosional processes. SSAST is an event based computer model that calculates the stable slope for a channel segment based on the post-mine hydrology and median grain size of a reclaimed surface mine. Peak discharge, which drives post-mine erosion, is calculated from a 10-year, 24-hour storm using the Soil Conservation Service curve number method. Curve number calibrated for Pennsylvania surface mines are used. Reclamation sites are represented by the rectangle of triangle which most closely fits the shape of the site while having the same drainage area and length. Sediment transport and slope stability are calculated using a modified Bagnold's equation with a correction factor for the irregular particle shapes formed during the mining process. Data from three reclaimed Pennsylvania surface mines were used to calibrate and verify SSAST. Analysis indicates that SSAST can predict longitudinal channel profiles for stable reclamation of surface mines in the humid, temperate northeastern US

  12. Kinetic modeling of microbially-driven redox chemistry of radionuclides in subsurface environments: Coupling transport, microbial metabolism and geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    WANG,YIFENG; PAPENGUTH,HANS W.

    2000-05-04

    Microbial degradation of organic matter is a driving force in many subsurface geochemical systems, and therefore may have significant impacts on the fate of radionuclides released into subsurface environments. In this paper, the authors present a general reaction-transport model for microbial metabolism, redox chemistry, and radionuclide migration in subsurface systems. The model explicitly accounts for biomass accumulation and the coupling of radionuclide redox reactions with major biogeochemical processes. Based on the consideration that the biomass accumulation in subsurface environments is likely to achieve a quasi-steady state, they have accordingly modified the traditional microbial growth kinetic equation. They justified the use of the biogeochemical models without the explicit representation of biomass accumulation, if the interest of modeling is in the net impact of microbial reactions on geochemical processes. They then applied their model to a scenario in which an oxic water flow containing both uranium and completing organic ligands is recharged into an oxic aquifer in a carbonate formation. The model simulation shows that uranium can be reduced and therefore immobilized in the anoxic zone created by microbial degradation.

  13. Kinetic modeling of microbially-driven redox chemistry of radionuclides in subsurface environments: Coupling transport, microbial metabolism and geochemistry

    International Nuclear Information System (INIS)

    Wang, Yifeng; Papenguth, Hans W.

    2000-01-01

    Microbial degradation of organic matter is a driving force in many subsurface geochemical systems, and therefore may have significant impacts on the fate of radionuclides released into subsurface environments. In this paper, the authors present a general reaction-transport model for microbial metabolism, redox chemistry, and radionuclide migration in subsurface systems. The model explicitly accounts for biomass accumulation and the coupling of radionuclide redox reactions with major biogeochemical processes. Based on the consideration that the biomass accumulation in subsurface environments is likely to achieve a quasi-steady state, they have accordingly modified the traditional microbial growth kinetic equation. They justified the use of the biogeochemical models without the explicit representation of biomass accumulation, if the interest of modeling is in the net impact of microbial reactions on geochemical processes. They then applied their model to a scenario in which an oxic water flow containing both uranium and completing organic ligands is recharged into an oxic aquifer in a carbonate formation. The model simulation shows that uranium can be reduced and therefore immobilized in the anoxic zone created by microbial degradation

  14. Microbial and Organic Fine Particle Transport Dynamics in Streams - a Combined Experimental and Stochastic Modeling Approach

    Science.gov (United States)

    Drummond, Jen; Davies-Colley, Rob; Stott, Rebecca; Sukias, James; Nagels, John; Sharp, Alice; Packman, Aaron

    2014-05-01

    Transport dynamics of microbial cells and organic fine particles are important to stream ecology and biogeochemistry. Cells and particles continuously deposit and resuspend during downstream transport owing to a variety of processes including gravitational settling, interactions with in-stream structures or biofilms at the sediment-water interface, and hyporheic exchange and filtration within underlying sediments. Deposited cells and particles are also resuspended following increases in streamflow. Fine particle retention influences biogeochemical processing of substrates and nutrients (C, N, P), while remobilization of pathogenic microbes during flood events presents a hazard to downstream uses such as water supplies and recreation. We are conducting studies to gain insights into the dynamics of fine particles and microbes in streams, with a campaign of experiments and modeling. The results improve understanding of fine sediment transport, carbon cycling, nutrient spiraling, and microbial hazards in streams. We developed a stochastic model to describe the transport and retention of fine particles and microbes in rivers that accounts for hyporheic exchange and transport through porewaters, reversible filtration within the streambed, and microbial inactivation in the water column and subsurface. This model framework is an advance over previous work in that it incorporates detailed transport and retention processes that are amenable to measurement. Solute, particle, and microbial transport were observed both locally within sediment and at the whole-stream scale. A multi-tracer whole-stream injection experiment compared the transport and retention of a conservative solute, fluorescent fine particles, and the fecal indicator bacterium Escherichia coli. Retention occurred within both the underlying sediment bed and stands of submerged macrophytes. The results demonstrate that the combination of local measurements, whole-stream tracer experiments, and advanced modeling

  15. Human impact on erosion patterns and sediment transport in the Yangtze River

    NARCIS (Netherlands)

    Sun, Xilin; Li, Chang'an; Kuiper, K. F.; Zhang, Zengjie; Gao, Jianhua; Wijbrans, J. R.

    2016-01-01

    Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill

  16. Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kieft, T.L.; Murphy, E.M.; Haldeman, D.L.; Amy, P.S.; Bjornstad, B.N.; McDonald, E.V.; Ringelberg, D.B.; White, D.C.; Stair, J.; Griffiths, R.P.; Gsell, T.C.; Holben, W.E.; Boone, D.R.

    1995-01-05

    Two chronosequence of unsaturated buried loess sediments ranging in age from <10,000 years to >1 million years were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession were inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Samples were collected by coring at two sites 40 km apart in the Palouse region of eastern Washington State near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the elevation of the Winona site is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was {approx}250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: {approx}1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Sediments of equivalent age had equal quantities of microorganisms, but differing community types. Differences in community make-up between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the ages of the microbial communities can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be

  17. Live Cell Discovery of Microbial Vitamin Transport and Enzyme-Cofactor Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Lindsey N.; Koech, Phillip K.; Plymale, Andrew E.; Landorf, Elizabeth V.; Konopka, Allan; Collart, Frank; Lipton, Mary S.; Romine, Margaret F.; Wright, Aaron T.

    2016-02-02

    The rapid completion of microbial genomes is inducing a conundrum in functional gene discovery. Novel methods are critically needed to shorten the gap between characterizing a microbial genome and experimentally validating bioinformatically-predicted functions. Of particular importance are transport mechanisms, used to shuttle nutrients and metabolites across cell mem-branes, such as B vitamins, which are indispensable to metabolic reactions crucial to the survival of diverse microbes ranging from members of environmental microbial communities to human pathogens. Methods to accurately assign function and specificity for a wide range of experimentally unidentified and/or predicted membrane-embedded transport proteins, and characterization of intra-cellular enzyme-cofactor/nutrient associations are needed to enable a significantly improved understanding of microbial biochemis-try and physiology, how microbes associate with others, and how they sense and respond to environmental perturbations. Chemical probes derived from B vitamins B1, B2, and B7 have allowed us to experimentally address the aforementioned needs by identifying B vitamin transporters and intracellular protein-cofactor associations through live cell labeling of the filamentous anoxygenic pho-toheterotroph, Chloroflexus aurantiacus J-10-fl, known for both B vitamin biosynthesis and environmental salvage. Our probes provide a unique opportunity to directly link cellular activity and protein function back to ecosystem and/or host dynamics by iden-tifying B vitamin transport and disposition mechanisms required for survival.

  18. Runoff erosion

    OpenAIRE

    Evelpidou, Niki (Ed.); Cordier, Stephane (Ed.); Merino, Agustin (Ed.); Figueiredo, Tomás de (Ed.); Centeri, Csaba (Ed.)

    2013-01-01

    Table of Contents PART I – THEORY OF RUNOFF EROSION CHAPTER 1 - RUNOFF EROSION – THE MECHANISMS CHAPTER 2 - LARGE SCALE APPROACHES OF RUNOFF EROSION CHAPTER 3 - MEASURING PRESENT RUNOFF EROSION CHAPTER 4 - MODELLING RUNOFF EROSION CHAPTER 5 - RUNOFF EROSION AND HUMAN SOCIETIES: THE INFLUENCE OF LAND USE AND MANAGEMENT PRACTICES ON SOIL EROSION PART II - CASE STUDIES CASE STUDIES – INTRODUCTION: RUNOFF EROSION IN MEDITERRANEAN AREA CASE STUDY 1: Soil Erosion Risk...

  19. Microbial electron transport and energy conservation – the foundation for optimizing bioelectrochemical systems

    Science.gov (United States)

    Kracke, Frauke; Vassilev, Igor; Krömer, Jens O.

    2015-01-01

    Microbial electrochemical techniques describe a variety of emerging technologies that use electrode–bacteria interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and the production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyze the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g., cytochromes, ferredoxin, quinones, flavins) are identified and analyzed regarding their possible role in electrode–microbe interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bioelectrochemical

  20. A faster numerical scheme for a coupled system modeling soil erosion and sediment transport

    Science.gov (United States)

    Le, M.-H.; Cordier, S.; Lucas, C.; Cerdan, O.

    2015-02-01

    Overland flow and soil erosion play an essential role in water quality and soil degradation. Such processes, involving the interactions between water flow and the bed sediment, are classically described by a well-established system coupling the shallow water equations and the Hairsine-Rose model. Numerical approximation of this coupled system requires advanced methods to preserve some important physical and mathematical properties; in particular, the steady states and the positivity of both water depth and sediment concentration. Recently, finite volume schemes based on Roe's solver have been proposed by Heng et al. (2009) and Kim et al. (2013) for one and two-dimensional problems. In their approach, an additional and artificial restriction on the time step is required to guarantee the positivity of sediment concentration. This artificial condition can lead the computation to be costly when dealing with very shallow flow and wet/dry fronts. The main result of this paper is to propose a new and faster scheme for which only the CFL condition of the shallow water equations is sufficient to preserve the positivity of sediment concentration. In addition, the numerical procedure of the erosion part can be used with any well-balanced and positivity preserving scheme of the shallow water equations. The proposed method is tested on classical benchmarks and also on a realistic configuration.

  1. Transport-distance specific SOC distribution: Does it skew erosion induced C fluxes?

    DEFF Research Database (Denmark)

    Hu, Yaxian; Berbe, Asmerat Asefaw; Fogel, Marilyn L.

    2016-01-01

    Abstract The net effect of soil erosion by water, as a sink or source of atmospheric carbon dioxide (CO2), is determined by the spatial (re-)distribution and stability of eroded soil organic carbon (SOC), and the dynamic replacement of eroded C by the production of new photosynthate. The depositi......Abstract The net effect of soil erosion by water, as a sink or source of atmospheric carbon dioxide (CO2), is determined by the spatial (re-)distribution and stability of eroded soil organic carbon (SOC), and the dynamic replacement of eroded C by the production of new photosynthate...... the actual movement of eroded soil fractions along hillslopes, let alone the re-distribution pattern of SOC fractions. Eroding sandy soils and sediment were sampled after a series of rainfall events along a slope on a freshly seeded cropland in Jutland, Denmark. All the soil samples were fractionated...... into five settling classes using a settling tube apparatus. The spatial distribution of soil settling classes shows a coarsening effect immediately below the eroding slope, followed by a fining trend at the slope tail. These findings support the validity of the conceptual model proposed by Starr et al...

  2. An Outflow Event on the Left Side of Harvey: Erosion of Barrier Sand and Seaward Transport Through Aransas Pass

    Science.gov (United States)

    Goff, J.; Swartz, J. M.; Gulick, S. P. S.

    2017-12-01

    Barrier islands provide critical support and protection for coastal communities and ecosystems, but are potentially vulnerable to net losses of sand during major storms. Evidence from satellite imagery, ground observations and tide stations indicates that Hurricane Harvey in 2017 caused a large outflow event of waters moving from the bays out towards the sea in the Port Aransas, Texas region. Rather than just an ebb of a storm surge, this event may have been driven by seaward-directed winds on the left side of storm. Less than a month after landfall, we conducted a swath mapping and sampling survey in Lydia Ann Channel and Aransas Pass, where we had earlier mapped in 2009 and 2012 as part of the UT marine geology and geophysical field course. These waterways are important conduits linking Corpus Christi and Aransas bays to the Gulf of Mexico. This multi-year record allows us to gauge the impact of the outflow event on these waterways in the context of "normal" coastal processes. Both satellite imagery and sonar mapping reveal that the outflow event caused significant erosion, both on land and beneath the water, along the edges of Lydia Ann Channel and Corpus Christi ship channel. It also caused seaward-directed flow and erosion through breaches in the foredunes along southern San Jose Island, from waters that overtopped Lydia Ann Channel. Much of the sand that was transported seaward settled in Lydia Ann Channel and Aransas Pass (up to 6.5 m accumulation), possibly during the waning stages of the event. However, a likely large (but unknown) quantity of barrier and estuarine sand could have been transported well out to sea, beyond the jetties, at the peak of the event. If so, it would have resulted in a net loss of sand from the barrier island system.

  3. Categorization of erosion control matting.

    Science.gov (United States)

    2012-05-29

    Erosion control is a critical aspect of any Georgia Department of Transportation (GDOT) : construction project, with the extreme negative impacts of high sediment loads in natural : waterways having been well documented. A variety of erosion control ...

  4. Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

    International Nuclear Information System (INIS)

    Kieft, T.L.; Murphy, E.M.; Haldeman, D.L.; Amy, P.S.; Bjornstad, B.N.; McDonald, E.V.; Ringelberg, D.B.; White, D.C.; Stair, J.; Griffiths, R.P.; Gsell, T.C.; Holben, W.E.; Boone, D.R.

    1995-01-01

    Two chronosequence of unsaturated buried loess sediments ranging in age from and lt;10,000 years to and gt;1 million years were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession were inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Samples were collected by coring at two sites 40 km apart in the Palouse region of eastern Washington State near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the elevation of the Winona site is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was(approx)250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age:(approx)1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Sediments of equivalent age had equal quantities of microorganisms, but differing community types. Differences in community make-up between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the ages of the microbial communities can be constrained by porewater and sediment ages. In the shallower sediments ( and lt;9 m at Washtucna, and lt;12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the

  5. The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

    Science.gov (United States)

    Shobe, Charles M.; Tucker, Gregory E.; Barnhart, Katherine R.

    2017-12-01

    Models of landscape evolution by river erosion are often either transport-limited (sediment is always available but may or may not be transportable) or detachment-limited (sediment must be detached from the bed but is then always transportable). While several models incorporate elements of, or transition between, transport-limited and detachment-limited behavior, most require that either sediment or bedrock, but not both, are eroded at any given time. Modeling landscape evolution over large spatial and temporal scales requires a model that can (1) transition freely between transport-limited and detachment-limited behavior, (2) simultaneously treat sediment transport and bedrock erosion, and (3) run in 2-D over large grids and be coupled with other surface process models. We present SPACE (stream power with alluvium conservation and entrainment) 1.0, a new model for simultaneous evolution of an alluvium layer and a bedrock bed based on conservation of sediment mass both on the bed and in the water column. The model treats sediment transport and bedrock erosion simultaneously, embracing the reality that many rivers (even those commonly defined as bedrock rivers) flow over a partially alluviated bed. SPACE improves on previous models of bedrock-alluvial rivers by explicitly calculating sediment erosion and deposition rather than relying on a flux-divergence (Exner) approach. The SPACE model is a component of the Landlab modeling toolkit, a Python-language library used to create models of Earth surface processes. Landlab allows efficient coupling between the SPACE model and components simulating basin hydrology, hillslope evolution, weathering, lithospheric flexure, and other surface processes. Here, we first derive the governing equations of the SPACE model from existing sediment transport and bedrock erosion formulations and explore the behavior of local analytical solutions for sediment flux and alluvium thickness. We derive steady-state analytical solutions for

  6. Microbial behaviour and cross contamination between cargoes in containerized transportation of food

    DEFF Research Database (Denmark)

    Abban, Stephen

    Transportation is central to the global food and feed supply chain. Thus issues of safety, especially cross contamination with pathogens during food transit should be important in food handling operations. A large proportion of the worlds’ food cargo is moved using intermodal cargo containers...... chain, its role in food safety cannot be ignored. Unfortunately not much effort has been put, scientifically, into understanding the role of the various features of the transportation links in food cross contamination (compared to studies for homes, processing factories and farm yards). The PhD project...... has attempted to shed light on containerized food transport and some of its important attributes as regards hygiene and cross contamination. The overall aim of the study was to ‘identify possible microbial hazards and ways of cross contamination during containerized transportation of foods...

  7. Transport of silver nanoparticles by runoff and erosion – A flume experiment

    NARCIS (Netherlands)

    Mahdi, Karrar N.M.; Commelin, Meindert; Peters, Ruud J.B.; Baartman, Jantiene E.M.; Ritsema, Coen; Geissen, Violette

    2017-01-01

    Silver nanoparticles (AgNPs) are being used in many products as they have unique antimicrobial-biocidal properties. After disposal of these products AgNPs can reach the soil environment possibly affecting soil organisms and disrupting plants. This work aimed to study the transport of AgNPs by

  8. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, J.H.; Madilyn Fletcher

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

  9. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component. Final report

    International Nuclear Information System (INIS)

    Cushman, J.H.

    2000-01-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

  10. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    Energy Technology Data Exchange (ETDEWEB)

    Cushman, J.H.

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media.

  11. Scales and erosion

    Science.gov (United States)

    There is a need to develop scale explicit understanding of erosion to overcome existing conceptual and methodological flaws in our modelling methods currently applied to understand the process of erosion, transport and deposition at the catchment scale. These models need to be based on a sound under...

  12. User manual of Soil and Cesium Transport (SACT), a program to predict long-term Cs distribution using USLE for soil erosion, transportation and deposition

    International Nuclear Information System (INIS)

    Saito, Hiroshi; Yamaguchi, Masaaki; Kitamura, Akihiro

    2016-12-01

    This manual provides useful and necessary information to users of 'SACT' (Soil and Cesium Transport), which Japan Atomic Energy Agency (JAEA) has developed to predict a long-term distribution of Cs deposited on the land surface of Fukushima due to the Fukushima Daiichi Nuclear Power Station accident on March 11, 2011. SACT calculates soil movement (erosion, transportation and deposition) and resulting Cs migration, and predicts its future distribution, with the assumption that Cs is adhered to soil initially. SACT uses USLE (Universal Soil Loss Equation) for potential soil loss and simple hydraulic equations for soil transportation and deposition in which soil is divided into course-grained sand and fine-grained silt/clay. The amount of Cs moved with soil is predicted by the amount of above-mentioned soil movement and concentration ratio of Cs for each grain-size. SACT utilizes the 'ArcGIS' software and the GIS (Geographical Information System). SACT is characterized by its simplicity which enables fast calculation for wide area for long-term duration, using existing simple equations including USLE. Data for used parameters are widely available, and site-specific calculations are possible by using data obtained from the targeted area. (author)

  13. Bentonite erosion: effects on the long term performance of the engineered barrier and radionuclide transport - The BELBAR project

    International Nuclear Information System (INIS)

    Sellin, P.; Sundman, D.; Bailey, L.; Missana, T.; Schaefer, T.; Cervinka, R.; Koskinen, K.

    2012-01-01

    Document available in extended abstract form only. BELBaR is a Collaborative Project within the Seventh Framework Programme of the European Atomic Energy Community (Euratom) for nuclear research and training activities. The main aim of BELBaR is to increase knowledge of the processes that control clay colloid stability, generation and its ability to transport radionuclides. The overall purpose of the project is to come up with a new way of treating issues in long-term safety/performance assessment. The project started March 1, 2012 and has a duration of 48 months. The project has 14 partners from seven European countries. The main aim of BELBaR is to reduce the uncertainties in the description of the effect of clay colloids on the long term performance of the engineered barrier and on radionuclide transport as illustrated in Figure 1. This is done by: - Improving the understanding on when bentonite colloids are unstable. For a given site/site evolution, this is critical information, since it determines whether or not clay colloids need to be included in the long-term assessment. - Improving the quantitative models for erosion on the bentonite barrier for the cases when the colloids are stable - Improving the understanding of how radionuclides attach to clay colloids. This information will be used to formulate improved transport models for the assessment of radionuclide transport in the geosphere. To meet the main aim a number of experimental and modelling activities will be undertaken within the project. BELBaR consists of six RTD (research and technical development) work packages and one project management work package. WP1 will have the responsibility to ensure that that the type and values of the parameters selected for experimental and modelling work are those that represent as much as possible the full range of conditions and situations that can be expected in a repository. Drawing on the work undertaken in WP 2 to 5, the general objective of this work package

  14. Retention and transport of an anaerobic trichloroethene dechlorinating microbial culture in anaerobic porous media.

    Science.gov (United States)

    Zhang, Huixin; Ulrich, Ania C; Liu, Yang

    2015-06-01

    The influence of solution chemistry on microbial transport was examined using the strictly anaerobic trichloroethene (TCE) bioaugmentation culture KB-1(®). A column was employed to determine transport behaviors and deposition kinetics of three distinct functional species in KB-1(®), Dehalococcoides, Geobacter, and Methanomethylovorans, over a range of ionic strengths under a well-controlled anaerobic condition. A quantitative polymerase chain reaction (qPCR) was utilized to enumerate cell concentration and complementary techniques were implemented to evaluate cell surface electrokinetic potentials. Solution chemistry was found to positively affect the deposition rates, which was consistent with calculated Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Retained microbial profiles showed spatially constant colloid deposition rate coefficients, in agreement with classical colloid filtration theory (CFT). It was interesting to note that the three KB-1(®) species displayed similar transport and retention behaviors under the defined experimental conditions despite their different cell electrokinetic properties. A deeper analysis of cell characteristics showed that factors, such as cell size and shape, concentration, and motility were involved in determining adhesion behavior. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Erosion and erosion-corrosion

    International Nuclear Information System (INIS)

    Isomoto, Yoshinori

    2008-01-01

    It is very difficult to interpret the technical term of erosion-corrosion' which is sometimes encountered in piping systems of power plants, because of complicated mechanisms and several confusing definitions of erosion-corrosion phenomena. 'FAC (flow accelerated corrosion)' is recently introduced as wall thinning of materials in power plant systems, as a representative of 'erosion-corrosion'. FAC is, however, not necessarily well understood and compared with erosion-corrosion. This paper describes firstly the origin, definition and fundamental understandings of erosion and erosion-corrosion, in order to reconsider and reconfirm the phenomena of erosion, erosion-corrosion and FAC. Next, typical mapping of erosion, corrosion, erosion-corrosion and FAC are introduced in flow velocity and environmental corrosiveness axes. The concept of damage rate in erosion-corrosion is finally discussed, connecting dissolution rate, mass transfer of metal ions in a metal oxide film and film growth. (author)

  16. Application of Polyacrylamide (PAM) through Lay-Flat Polyethylene Tubing: Effects on Infiltration, Erosion, N and P Transport, and Corn Yield.

    Science.gov (United States)

    McNeal, J P; Krutz, L J; Locke, M A; Kenty, M M; Atwill, R L; Pickelmann, D M; Bryant, C J; Wood, C W; Golden, B R; Cox, M S

    2017-07-01

    Polyacrylamides (PAMs), when applied as a soil amendment, purportedly improve soil infiltration, decrease erosion, and reduce offsite agrochemical transport. The effect of PAM on infiltration, erosion, agrochemical transport, and crop yield when applied in furrow to mid-southern US production systems has not been evaluated. The objective of this study was to assess PAM effects on infiltration, erosion, corn ( L.) grain yield, and nitrogen (N) and phosphorus (P) transport when applied at 10 mg L through lay-flat polyethylene tubing. A 2-yr field study was conducted at the Mississippi State Delta Research and Extension Center in Stoneville, MS, on a Dundee silt loam and a Forestdale silty clay loam. The experimental design was a randomized complete block with four replications of each treatment: irrigated plus no PAM (control) and irrigated plus PAM at 10 mg L. Each irrigation event delivered 102 mm of water at 18.9 L m per furrow, and runoff was captured in a holding tank on the lower end of each plot. Pooled over year and soil texture, PAM increased infiltration and corn grain yield by 6% ( ≤ 0.0398). Polyacrylamide effects on the offsite transport of sediment and N and P were inconsistent, varying across year and soil texture. Results indicate that PAM improves infiltration and corn grain yield on silt loam and silty clay loam textured soils; however, further research is required before PAM can be recommended as a best management practice for mitigating erosion and offsite agrochemical transport in mid-southern production systems. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  17. Terrace erosion and sediment transport model: a new tool for soil conservation planning in bench-terraced steeplands.

    NARCIS (Netherlands)

    van Dijk, A.I.J.M.; Bruijnzeel, L.A.

    2003-01-01

    Despite widespread bench-terracing soil erosion remains a major problem in Java's uplands. To elucidate the causes for this lack of impact, runoff and erosion processes were studied at a variety of spatial scales within a volcanic catchment in West Java. Research indicated that soil loss occurs via

  18. Modelling the transport and decay processes of microbial tracers in a macro-tidal estuary.

    Science.gov (United States)

    Abu-Bakar, Amyrhul; Ahmadian, Reza; Falconer, Roger A

    2017-10-15

    The Loughor Estuary is a macro-tidal coastal basin, located along the Bristol Channel, in the South West of the U.K. The maximum spring tidal range in the estuary is up to 7.5 m, near Burry Port Harbour. This estuarine region can experience severe coastal flooding during high spring tides, including extreme flooding of the intertidal saltmarshes at Llanrhidian, as well as the lower industrial and residential areas at Llanelli and Gowerton. The water quality of this estuarine basin needs to comply with the designated standards for safe recreational bathing and shellfish harvesting industries. The waterbody however, potentially receives overloading of bacterial inputs that enter the estuarine system from both point and diffuse sources. Therefore, a microbial tracer study was carried out to get a better understanding of the faecal bacteria sources and to enable a hydro-environmental model to be refined and calibrated for both advection and dispersion transport. A two-dimensional hydro-environmental model has been refined and extended to predict the highest water level covering the intertidal floodplains of the Loughor Estuary. The validated hydrodynamic model for both water levels and currents, was included with the injected mass of microbial tracer, i.e. MS2 coliphage from upstream of the estuary, and modelled as a non-conservative tracer over several tidal cycles through the system. The calibration and validation of the transport and decay of microbial tracer was undertaken, by comparing the model results and the measured data at two different sampling locations. The refined model developed as a part of this study, was used to acquire a better understanding of the water quality processes and the potential sources of bacterial pollution in the estuary. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Incorporating Geochemical And Microbial Kinetics In Reactive Transport Models For Generation Of Acid Rock Drainage

    Science.gov (United States)

    Andre, B. J.; Rajaram, H.; Silverstein, J.

    2010-12-01

    Acid mine drainage, AMD, results from the oxidation of metal sulfide minerals (e.g. pyrite), producing ferrous iron and sulfuric acid. Acidophilic autotrophic bacteria such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans obtain energy by oxidizing ferrous iron back to ferric iron, using oxygen as the electron acceptor. Most existing models of AMD do not account for microbial kinetics or iron geochemistry rigorously. Instead they assume that oxygen limitation controls pyrite oxidation and thus focus on oxygen transport. These models have been successfully used for simulating conditions where oxygen availability is a limiting factor (e.g. source prevention by capping), but have not been shown to effectively model acid generation and effluent chemistry under a wider range of conditions. The key reactions, oxidation of pyrite and oxidation of ferrous iron, are both slow kinetic processes. Despite being extensively studied for the last thirty years, there is still not a consensus in the literature about the basic mechanisms, limiting factors or rate expressions for microbially enhanced oxidation of metal sulfides. An indirect leaching mechanism (chemical oxidation of pyrite by ferric iron to produce ferrous iron, with regeneration of ferric iron by microbial oxidation of ferrous iron) is used as the foundation of a conceptual model for microbially enhanced oxidation of pyrite. Using literature data, a rate expression for microbial consumption of ferrous iron is developed that accounts for oxygen, ferrous iron and pH limitation. Reaction rate expressions for oxidation of pyrite and chemical oxidation of ferrous iron are selected from the literature. A completely mixed stirred tank reactor (CSTR) model is implemented coupling the kinetic rate expressions, speciation calculations and flow. The model simulates generation of AMD and effluent chemistry that qualitatively agrees with column reactor and single rock experiments. A one dimensional reaction

  20. Coupled Transport/Reaction Modelling of Copper Canister Corrosion Aided by Microbial Processes

    Energy Technology Data Exchange (ETDEWEB)

    Jinsong Liu [Royal Institute of Technology, Stockholm (Sweden). Dept. of Chemical Engineering and Technology

    2006-04-15

    Copper canister corrosion is an important issue in the concept of a nuclear fuel repository. Previous studies indicate that the oxygen-free copper canister could hold its integrity for more than 100,000 years in the repository environment. Microbial processes may reduce sulphate to sulphide and considerably increase the amount of sulphides available for corrosion. In this paper, a coupled transport/reaction model is developed to account for the transport of chemical species produced by microbial processes. The corroding agents like sulphide would come not only from the groundwater flowing in a fracture that intersects the canister, but also from the reduction of sulphate near the canister. The reaction of sulphate-reducing bacteria and the transport of sulphide in the bentonite buffer are included in the model. The depth of copper canister corrosion is calculated by the model. With representative 'central values' of the concentrations of sulphate and methane at repository depth at different sites in Fennoscandian Shield the corrosion depth predicted by the model is a few millimetres during 10{sup 5} years. As the concentrations of sulphate and methane are extremely site-specific and future climate changes may significantly influence the groundwater compositions at potential repository sites, sensitivity analyses have been conducted. With a broad perspective of the measured concentrations at different sites in Sweden and in Finland, and some possible mechanisms (like the glacial meltwater intrusion and interglacial seawater intrusion) that may introduce more sulphate into the groundwater at intermediate depths during future climate changes, higher concentrations of either/both sulphate and methane than what is used as the representative 'central' values would be possible. In worst cases. locally, half of the canister thickness could possibly be corroded within 10{sup 5} years.

  1. Coupled Transport/Reaction Modelling of Copper Canister Corrosion Aided by Microbial Processes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jinsong [Royal Institute of Technology, Stockholm (Sweden). Dept. of Chemical Engineering and Technology

    2006-04-15

    Copper canister corrosion is an important issue in the concept of a nuclear fuel repository. Previous studies indicate that the oxygen-free copper canister could hold its integrity for more than 100,000 years in the repository environment. Microbial processes may reduce sulphate to sulphide and considerably increase the amount of sulphides available for corrosion. In this paper, a coupled transport/reaction model is developed to account for the transport of chemical species produced by microbial processes. The corroding agents like sulphide would come not only from the groundwater flowing in a fracture that intersects the canister, but also from the reduction of sulphate near the canister. The reaction of sulphate-reducing bacteria and the transport of sulphide in the bentonite buffer are included in the model. The depth of copper canister corrosion is calculated by the model. With representative 'central values' of the concentrations of sulphate and methane at repository depth at different sites in Fennoscandian Shield the corrosion depth predicted by the model is a few millimetres during 10{sup 5} years. As the concentrations of sulphate and methane are extremely site-specific and future climate changes may significantly influence the groundwater compositions at potential repository sites, sensitivity analyses have been conducted. With a broad perspective of the measured concentrations at different sites in Sweden and in Finland, and some possible mechanisms (like the glacial meltwater intrusion and interglacial seawater intrusion) that may introduce more sulphate into the groundwater at intermediate depths during future climate changes, higher concentrations of either/both sulphate and methane than what is used as the representative 'central' values would be possible. In worst cases. locally, half of the canister thickness could possibly be corroded within 10{sup 5} years.

  2. Coupled Transport/Reaction Modelling of Copper Canister Corrosion Aided by Microbial Processes

    International Nuclear Information System (INIS)

    Jinsong Liu

    2006-04-01

    Copper canister corrosion is an important issue in the concept of a nuclear fuel repository. Previous studies indicate that the oxygen-free copper canister could hold its integrity for more than 100,000 years in the repository environment. Microbial processes may reduce sulphate to sulphide and considerably increase the amount of sulphides available for corrosion. In this paper, a coupled transport/reaction model is developed to account for the transport of chemical species produced by microbial processes. The corroding agents like sulphide would come not only from the groundwater flowing in a fracture that intersects the canister, but also from the reduction of sulphate near the canister. The reaction of sulphate-reducing bacteria and the transport of sulphide in the bentonite buffer are included in the model. The depth of copper canister corrosion is calculated by the model. With representative 'central values' of the concentrations of sulphate and methane at repository depth at different sites in Fennoscandian Shield the corrosion depth predicted by the model is a few millimetres during 10 5 years. As the concentrations of sulphate and methane are extremely site-specific and future climate changes may significantly influence the groundwater compositions at potential repository sites, sensitivity analyses have been conducted. With a broad perspective of the measured concentrations at different sites in Sweden and in Finland, and some possible mechanisms (like the glacial meltwater intrusion and interglacial seawater intrusion) that may introduce more sulphate into the groundwater at intermediate depths during future climate changes, higher concentrations of either/both sulphate and methane than what is used as the representative 'central' values would be possible. In worst cases. locally, half of the canister thickness could possibly be corroded within 10 5 years

  3. Wind erosion of soils burned by wildfire

    Science.gov (United States)

    N. S. Wagenbrenner; M. J. Germino; B. K. Lamb; R. B. Foltz; P. R. Robichaud

    2011-01-01

    Wind erosion and aeolian transport processes are largely unstudied in the post-wildfire environment, but recent studies have shown that wind erosion can play a major role in burned landscapes. A wind erosion monitoring system was installed immediately following a wildfire in southeastern Idaho, USA to measure wind erosion from the burned area (Figure 1). This paper...

  4. Reply to 'Comment on kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' by J. Griffioen

    Science.gov (United States)

    Hunter, K. S.; Van Cappellen, P.

    2000-01-01

    Our paper, 'Kinetic modeling of microbially-driven redox chemistry of subsurface environments: coupling transport, microbial metabolism and geochemistry' (Hunter et al., 1998), presents a theoretical exploration of biogeochemical reaction networks and their importance to the biogeochemistry of groundwater systems. As with any other model, the kinetic reaction-transport model developed in our paper includes only a subset of all physically, biologically and chemically relevant processes in subsurface environments. It considers aquifer systems where the primary energy source driving microbial activity is the degradation of organic matter. In addition to the primary biodegradation pathways of organic matter (i.e. respiration and fermentation), the redox chemistry of groundwaters is also affected by reactions not directly involving organic matter oxidation. We refer to the latter as secondary reactions. By including secondary redox reactions which consume reduced reaction products (e.g., Mn2+, FeS, H2S), and in the process compete with microbial heterotrophic populations for available oxidants (i.e. O2, NO3-, Mn(IV), Fe(III), SO42-), we predict spatio-temporal distributions of microbial activity which differ significantly from those of models which consider only the biodegradation reactions. That is, the secondary reactions have a significant impact on the distributions of the rates of heterotrophic and chemolithotrophic metabolic pathways. We further show that secondary redox reactions, as well as non-redox reactions, significantly influence the acid-base chemistry of groundwaters. The distributions of dissolved inorganic redox species along flowpaths, however, are similar in simulations with and without secondary reactions (see Figs. 3(b) and 7(b) in Hunter et al., 1998), indicating that very different biogeochemical reaction dynamics may lead to essentially the same chemical redox zonation of a groundwater system.

  5. The importance of OH − transport through anion exchange membrane in microbial electrolysis cells

    KAUST Repository

    Ye, Yaoli

    2018-01-11

    In two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact electrochemical performance. However, ion transport between the chambers will also impact performance, which is a factor not included in those calculations. To separate the impacts of pH and ion transport on MEC performance, a high molecular weight polymer buffer (PoB), which was retained in the catholyte due to its low AEM transport and cationic charge, was compared to PBS in MECs and abiotic electrochemical half cells (EHCs). In MECs, catholyte pH control was less important than ion transport. MEC tests using the PoB catholyte, which had a higher buffer capacity and thus maintained a lower catholye pH (<8), resulted in a 50% lower hydrogen production rate (HPR) than that obtained using PBS (HPR = 0.7 m3-H2 m−3 d−1) where the catholyte rapidly increased to pH = 12. The main reason for the decreased performance using PoB was a lack of hydroxide ion transfer into the anolyte to balance pH. The anolyte pH in MECs rapidly decreased to 5.8 due to a lack of hydroxide ion transport, which inhibited current generation by the anode, whereas the pH was maintained at 6.8 using PBS. In abiotic tests in ECHs, where the cathode potential was set at −1.2 V, the HPR was 133% higher using PoB than PBS due to catholyte pH control, as the anolyte pH was not a factor in the performance. These results show that maintaining charge transfer to control anolyte pH is more important than obtaining a more neutral pH catholyte.

  6. Coupling a basin erosion and river sediment transport model into a large scale hydrological model: an application in the Amazon basin

    Science.gov (United States)

    Buarque, D. C.; Collischonn, W.; Paiva, R. C. D.

    2012-04-01

    This study presents the first application and preliminary results of the large scale hydrodynamic/hydrological model MGB-IPH with a new module to predict the spatial distribution of the basin erosion and river sediment transport in a daily time step. The MGB-IPH is a large-scale, distributed and process based hydrological model that uses a catchment based discretization and the Hydrological Response Units (HRU) approach. It uses physical based equations to simulate the hydrological processes, such as the Penman Monteith model for evapotranspiration, and uses the Muskingum Cunge approach and a full 1D hydrodynamic model for river routing; including backwater effects and seasonal flooding. The sediment module of the MGB-IPH model is divided into two components: 1) prediction of erosion over the basin and sediment yield to river network; 2) sediment transport along the river channels. Both MGB-IPH and the sediment module use GIS tools to display relevant maps and to extract parameters from SRTM DEM (a 15" resolution was adopted). Using the catchment discretization the sediment module applies the Modified Universal Soil Loss Equation to predict soil loss from each HRU considering three sediment classes defined according to the soil texture: sand, silt and clay. The effects of topography on soil erosion are estimated by a two-dimensional slope length (LS) factor which using the contributing area approach and a local slope steepness (S), both estimated for each DEM pixel using GIS algorithms. The amount of sediment releasing to the catchment river reach in each day is calculated using a linear reservoir. Once the sediment reaches the river they are transported into the river channel using an advection equation for silt and clay and a sediment continuity equation for sand. A sediment balance based on the Yang sediment transport capacity, allowing to compute the amount of erosion and deposition along the rivers, is performed for sand particles as bed load, whilst no

  7. Soil erosion transport through multiple rainfall events in the presence of stone cover: Laboratory flume experiments and analysis with the Hairsine-Rose model

    Science.gov (United States)

    Jomaa, S.; Barry, D. A.; Brovelli, A.; Heng, B. P.; Sander, G. C.; Parlange, J.

    2011-12-01

    Soil erosion is a major environmental problem that can lead to loss of fertility and degradation of agricultural fields. In order to develop efficient strategies to mitigate the impact of precipitation and reduce the erosion rate, a process-based understanding of the mechanisms that govern sediment transport and delivery is necessary. Soil state and physical properties prior to a precipitation event can affect significantly the erosion rate. Among the most important soil variables are moisture content, compaction and infiltration capacity. Additionally, the presence of stones on the topsoil surface retards the overland flow discharge, reduces runoff generation as well as the sediment delivery and prevents the development of a surface seal, which in turn maintains the infiltration rate. The aim of this study was to examine in detail the effect of surface stones, soil compaction and sealing for a sequence of rainfall events on soil erosion. Experiments were conducted using the EPFL erosion flume, which was divided into two identical flumes (one with stone and one without). The experiment involved four rainfall events with the precipitation rates: 28, 74, 74 and 28 mm h-1. After each 2-h event, the soil was allowed to air dry for 22 h. The total sediment concentration, the concentration of seven sediment size classes and the flow discharge were measured during each event at the outlet of each flume. Experimental results were analyzed using the Hairsine and Rose (H-R) soil erosion model. Results showed that (i) within each precipitation event, the proportion of each size class for the bare/stone-covered flume pairs at steady state were similar, whereas the initial response differed significantly; (ii) in all cases the effluent was enriched in finer particles relative to the original soil; and (iii) the effluent sediment composition was different from that of the original soil, and there was no clear trend towards the parent soil sediment size composition with time. The

  8. Mineral solubility and free energy controls on microbial reaction kinetics: Application to contaminant transport in the subsurface

    Energy Technology Data Exchange (ETDEWEB)

    Taillefert, Martial [Georgia Inst. of Technology, Atlanta, GA (United States); Van Cappellen, Philippe [Univ. of Waterloo, ON (Canada)

    2016-11-14

    Recent developments in the theoretical treatment of geomicrobial reaction processes have resulted in the formulation of kinetic models that directly link the rates of microbial respiration and growth to the corresponding thermodynamic driving forces. The overall objective of this project was to verify and calibrate these kinetic models for the microbial reduction of uranium(VI) in geochemical conditions that mimic as much as possible field conditions. The approach combined modeling of bacterial processes using new bioenergetic rate laws, laboratory experiments to determine the bioavailability of uranium during uranium bioreduction, evaluation of microbial growth yield under energy-limited conditions using bioreactor experiments, competition experiments between metabolic processes in environmentally relevant conditions, and model applications at the field scale. The new kinetic descriptions of microbial U(VI) and Fe(III) reduction should replace those currently used in reactive transport models that couple catabolic energy generation and growth of microbial populations to the rates of biogeochemical redox processes. The above work was carried out in collaboration between the groups of Taillefert (batch reactor experiments and reaction modeling) at Georgia Tech and Van Cappellen (retentostat experiments and reactive transport modeling) at University of Waterloo (Canada).

  9. Structure and function of subsurface microbial communities affecting radionuclide transport and bioimmobilization

    Energy Technology Data Exchange (ETDEWEB)

    Kostka, Joel E. [Florida State Univ., Tallahassee, FL (United States); Prakash, Om [Florida State Univ., Tallahassee, FL (United States); Green, Stefan J. [Florida State Univ., Tallahassee, FL (United States); Akob, Denise [Florida State Univ., Tallahassee, FL (United States); Jasrotia, Puja [Florida State Univ., Tallahassee, FL (United States); Kerkhof, Lee [Rutgers Univ., New Brunswick, NJ (United States); Chin, Kuk-Jeong [Georgia State Univ., Atlanta, GA (United States); Sheth, Mili [Georgia State Univ., Atlanta, GA (United States); Keller, Martin [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Venkateswaran, Amudhan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Elkins, James G. [Univ. of Illinois, Urbana-Champaign, IL (United States); Stucki, Joseph W. [Univ. of Illinois, Urbana-Champaign, IL (United States)

    2012-05-01

    Our objectives were to: 1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), 2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and 3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations. Field sampling was conducted at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee. The ORFRC subsurface is exposed to mixed contamination predominated by uranium and nitrate. In short, we effectively addressed all 3 stated objectives of the project. In particular, we isolated and characterized a large number of novel anaerobes with a high bioremediation potential that can be used as model organisms, and we are now able to quantify the function of subsurface sedimentary microbial communities in situ using state-of-the-art gene expression methods (molecular proxies).

  10. Ability of One-Dimensional Hairsine-Rose Erosion Model to Predict Sediment Transport over a Soil with Significant Surface Stones

    Science.gov (United States)

    Jomaa, S.; Barry, D. A.; Sander, G. C.; Parlange, J.-Y.; Heng, B. C. P.; Tromp-van Meerveld, H. J.

    2010-05-01

    Surface stones affect erosion rates by reducing raindrop-driven detachment and protecting the original soil against overland flow induced-hydraulic stress. Numerous studies have shown that the effect of surface stones on erosion depends on both the stone characteristics (e.g., size, distribution) and the soil properties. The aim of this study was (i) to quantify how the stone characteristics can affect the total sediment concentration and the concentrations of the individual size classes, (ii) to test if stones affect preferentially a particular size class within the eroded sediment and (iii) to determine whether the 1D Hairsine-Rose (H-R) erosion model can represent the experimental data. A series of laboratory experiments were conducted using the 2 m × 6 m EPFL erosion flume for a high rainfall intensity (60 mm/h) event on a gentle slope (2.2%). The flume was divided into two identical 1-m wide flumes. This separation was done to allow simultaneous replicate experiments. Experiments were conducted with different configurations and scenarios (stone coverage, size and emplacement). Three coverage proportions (20%, 40%, and 70%), two stone diameters (3-4 and 6-7 cm) and two emplacement types (topsoil and partially embedded) were tested. For each experiment, the total sediment concentration, the concentration for the individual size classes, and the flume discharge were measured. Infiltration rates were measured at different depths and locations. A high resolution laser scanner provided details of the surface change due to erosion during the experiments. This technique allowed us to quantify the spatial distribution of eroded soil and to understand better if sediment transport is 1D or rather 2D over the flumes. The one-dimensional Hairsine-Rose (H-R) erosion model was used to fit the integrated data and to provide estimates of the parameters. The ability of the 1D H-R model to predict the measured sediment concentrations in the presence of stones in the soil matrix

  11. Erosive gastritis

    International Nuclear Information System (INIS)

    Mohammed, S.H.; Conrad, C.; Kjoergaad, J.

    1982-01-01

    Erosive gastritis is a well-defined radiologic and endoscopic entity. It is one of the common causes of upper gastrointestinal bleeding, yet it is seldom diagnosed and often confused with a number of other diseases. This communication re-emphasizes the characteristic endoscopic and radiologic features of erosive gastritis and its differential diagnosis. Two representative cases are reported. (orig.)

  12. Erosive gastritis

    Energy Technology Data Exchange (ETDEWEB)

    Mohammed, S.H.; Conrad, C.; Kjoergaad, J.

    1982-08-01

    Erosive gastritis is a well-defined radiologic and endoscopic entity. It is one of the common causes of upper gastrointestinal bleeding, yet it is seldom diagnosed and often confused with a number of other diseases. This communication re-emphasizes the characteristic endoscopic and radiologic features of erosive gastritis and its differential diagnosis. Two representative cases are reported.

  13. American lobsters (Homarus americanus not surviving during air transport: evaluation of microbial spoilage

    Directory of Open Access Journals (Sweden)

    Erica Tirloni

    2016-05-01

    Full Text Available Eighteen American lobsters (Homarus americanus, dead during air transport, were analysed in order to evaluate the microbial population of meat, gills and gut: no specific studies have ever been conducted so far on the microbiological quality of American lobsters’ meats in terms of spoilage microbiota. The meat samples showed very limited total viable counts, in almost all the cases below the level of 6 Log CFU/g, while higher loads were found, as expected, in gut and gills, the most probable source of contamination. These data could justify the possibility to commercialise these notsurviving subjects, without quality concerns for the consumers. Most of the isolates resulted to be clustered with type strains of Pseudoalteromonas spp. (43.1% and Photobacterium spp. (24.1%, and in particular to species related to the natural marine environment. The distribution of the genera showed a marked inhomogeneity among the samples. The majority of the isolates identified resulted to possess proteolytic (69.3% and lipolytic ability (75.5%, suggesting their potential spoilage ability. The maintanance of good hygienical practices, especially during the production of ready-to-eat lobsters-based products, and a proper storage could limit the possible replication of these microorganisms.

  14. American Lobsters (Homarus Americanus) not Surviving During Air Transport: Evaluation of Microbial Spoilage.

    Science.gov (United States)

    Tirloni, Erica; Stella, Simone; Gennari, Mario; Colombo, Fabio; Bernardi, Cristian

    2016-04-19

    Eighteen American lobsters ( Homarus americanus ), dead during air transport, were analysed in order to evaluate the microbial population of meat, gills and gut: no specific studies have ever been conducted so far on the microbiological quality of American lobsters' meats in terms of spoilage microbiota. The meat samples showed very limited total viable counts, in almost all the cases below the level of 6 Log CFU/g, while higher loads were found, as expected, in gut and gills, the most probable source of contamination. These data could justify the possibility to commercialise these not-surviving subjects, without quality concerns for the consumers. Most of the isolates resulted to be clustered with type strains of Pseudoalteromonas spp. (43.1%) and Photobacterium spp. (24.1%), and in particular to species related to the natural marine environment. The distribution of the genera showed a marked inhomogeneity among the samples. The majority of the isolates identified resulted to possess proteolytic (69.3%) and lipolytic ability (75.5%), suggesting their potential spoilage ability. The maintanance of good hygienical practices, especially during the production of ready-to-eat lobsters-based products, and a proper storage could limit the possible replication of these microorganisms.

  15. Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model

    International Nuclear Information System (INIS)

    Fang, Yilin; Scheibe, Timothy D.; Mahadevan, Radhakrishnan; Garg, Srinath; Long, Philip E.; Lovley, Derek R.

    2011-01-01

    The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species, multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The

  16. Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model.

    Science.gov (United States)

    Fang, Yilin; Scheibe, Timothy D; Mahadevan, Radhakrishnan; Garg, Srinath; Long, Philip E; Lovley, Derek R

    2011-03-25

    The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The

  17. Direct coupling of a genome-scale microbial in silico model and a groundwater reactive transport model

    Science.gov (United States)

    Fang, Yilin; Scheibe, Timothy D.; Mahadevan, Radhakrishnan; Garg, Srinath; Long, Philip E.; Lovley, Derek R.

    2011-03-01

    The activity of microorganisms often plays an important role in dynamic natural attenuation or engineered bioremediation of subsurface contaminants, such as chlorinated solvents, metals, and radionuclides. To evaluate and/or design bioremediated systems, quantitative reactive transport models are needed. State-of-the-art reactive transport models often ignore the microbial effects or simulate the microbial effects with static growth yield and constant reaction rate parameters over simulated conditions, while in reality microorganisms can dynamically modify their functionality (such as utilization of alternative respiratory pathways) in response to spatial and temporal variations in environmental conditions. Constraint-based genome-scale microbial in silico models, using genomic data and multiple-pathway reaction networks, have been shown to be able to simulate transient metabolism of some well studied microorganisms and identify growth rate, substrate uptake rates, and byproduct rates under different growth conditions. These rates can be identified and used to replace specific microbially-mediated reaction rates in a reactive transport model using local geochemical conditions as constraints. We previously demonstrated the potential utility of integrating a constraint-based microbial metabolism model with a reactive transport simulator as applied to bioremediation of uranium in groundwater. However, that work relied on an indirect coupling approach that was effective for initial demonstration but may not be extensible to more complex problems that are of significant interest (e.g., communities of microbial species and multiple constraining variables). Here, we extend that work by presenting and demonstrating a method of directly integrating a reactive transport model (FORTRAN code) with constraint-based in silico models solved with IBM ILOG CPLEX linear optimizer base system (C library). The models were integrated with BABEL, a language interoperability tool. The

  18. Soil erosion and suspended sediment transport in an agricultural watershed of Brie. Use of radioactive and magnetic tracers

    International Nuclear Information System (INIS)

    Sogon, St.

    1999-01-01

    The degradation of the water quality of rivers by the particulates and the associated pollutants coming from the erosion of agricultural soils is analyzed in the framework of the Piren-Seine program. The area under study is the catchment basin of the Grand Morin river in the Brie plateau (SE of the Paris basin, France). The 137 Cs (T1/2 = 30 years), mainly produced during the atmospheric nuclear tests (1952-1963) is rapidly and strongly fixed to the soil particulates and can be used as a tracer of their migration. These fallout are considered as uniform at the catchment basin scale but those coming from the Tchernobyl accident disturb this labelling. The image obtained from the implementation of the method (reference activity: 3170 Bq/m 2 in January 1, 1996, with 792 Bq/m 2 coming from Tchernobyl) on a 11.2 Ha field (Hardy field, 160 carrots) shows a badly structured 137 Cs redistribution. The mosaic of erosion and accumulation areas shows that the relays represent a major element of the erosion dynamics. No particular element of the landscape can explain the redistribution of the particulates, but the upward part has a more complex functioning with respect to the downward part which has more inclined slopes (>5%). The measurement of the particulates migration on the southern slope (3.5 Ha) of the field allows to calculate a sedimentary status (net erosion ratio: 4 kg/m 2 /year; sedimentary supply ratio: 40%). The study of the suspended matter exported by a buried drainage network (specific of the agriculture of the Brie region) shows strong 137 Cs, 7 Be (T1/2 = 53 days) and 210 Pb (T1/2 = 22 years) activities characteristic of a direct and fast transfer of the thin clay fraction (0.5-0.1 μm) coming from the ploughed layer. In the upstream part of the Vannetin river, the activity of the suspended matter remains identical to the one of the drainage network showing their influence. On the other hand, in the mid-stream part, the sources of suspended matter are

  19. Transport of microbial tracers in clean and organically contaminated silica sand in laboratory columns compared with their transport in the field

    International Nuclear Information System (INIS)

    Weaver, Louise; Sinton, Lester W.; Pang, Liping; Dann, Rod; Close, Murray

    2013-01-01

    Waste disposal on land and the consequent transport of bacterial and viral pathogens in soils and aquifers are of major concern worldwide. Pathogen transport can be enhanced in the presence of organic matter due to occupation of attachment sites in the aquifer materials thus preventing pathogen attachment leading to their faster transport for longer distances. Laboratory column studies were carried out to investigate the effect of organic matter, in the form of dissolved organic carbon (DOC), on the transport of Escherichia coli and MS2 phage in saturated clean silica sand. Transport rates of these microbial tracers were also studied in a contaminated field site. Laboratory column studies showed that low concentrations (0.17 mg L −1 ) of DOC had little effect on E. coli J6-2 removal and slightly reduced the attachment of MS2 phage. After progressive conditioning of the column with DOC (1.7 mg L −1 and 17 mg L −1 ), neither E. coli J6-2 nor MS2 phage showed any attachment and recovery rates increased dramatically (up to 100%). The results suggest that DOC can affect the transport rates of microbial contaminants. For E. coli J6-2 the predominant effect appeared to be an increase in the secondary energy minimum leading to an increase in E. coli attachment initially. However, after 17 mg L −1 DOC conditioning of the silica sand no attachment of E. coli was observed as the DOC took up attachment sites in the porous media. MS2 phage appeared to be affected predominantly by out-competition of binding sites in the clean silica sand and a steady reduction in attachment was observed as the DOC conditioning increased. Field study showed a high removal of both E. coli and MS2 phage, although E. coli was removed at a lower rate than MS2 phage. In the field it is likely that a combination of effects are seen as the aquifer material will be heterogeneous in its surface nanoscale properties, demonstrated by the differing removal of E. coli and MS2 phage compared to the

  20. Redox zone II. Coupled modeling of groundwater flow, solute transport, chemical reactions and microbial processes in the Aespoe island

    Energy Technology Data Exchange (ETDEWEB)

    Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang [Univ. Da Coruna (Spain)

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility

  1. Redox zone II. Coupled modeling of groundwater flow, solute transport, chemical reactions and microbial processes in the Aespoe island

    International Nuclear Information System (INIS)

    Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility

  2. Coupled modeling of groundwater flow solute transport, chemical reactions and microbial processes in the 'SP' island

    Energy Technology Data Exchange (ETDEWEB)

    Samper, Javier; Molinero, Jorg; Changbing, Yang; Zhang, Guoxiang

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus

  3. Final Report Coupling in silico microbial models with reactive transport models to predict the fate of contaminants in the subsurface.

    Energy Technology Data Exchange (ETDEWEB)

    Lovley, Derek R.

    2012-10-31

    This project successfully accomplished its goal of coupling genome-scale metabolic models with hydrological and geochemical models to predict the activity of subsurface microorganisms during uranium bioremediation. Furthermore, it was demonstrated how this modeling approach can be used to develop new strategies to optimize bioremediation. The approach of coupling genome-scale metabolic models with reactive transport modeling is now well enough established that it has been adopted by other DOE investigators studying uranium bioremediation. Furthermore, the basic principles developed during our studies will be applicable to much broader investigations of microbial activities, not only for other types of bioremediation, but microbial metabolism in diversity of environments. This approach has the potential to make an important contribution to predicting the impact of environmental perturbations on the cycling of carbon and other biogeochemical cycles.

  4. STRUCTURE AND FUNCTION OF SUBSURFACE MICROBIAL COMMUNITIES AFFECTING RADIONUCLIDE TRANSPORT AND BIOIMMOBILIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Joel E. Kostka; Lee Kerkhof; Kuk-Jeong Chin; Martin Keller; Joseph W. Stucki

    2011-06-15

    are new to science all show high sequence identity to sequences retrieved from ORFRC subsurface. (2) Based on physiological and phylogenetic characterization, two new species of subsurface bacteria were described: the metal-reducer Geobacter daltonii, and the denitrifier Rhodanobacter denitrificans. (3) Strains isolated from the ORFRC show that Rhodanobacter species are well adapted to the contaminated subsurface. Strains 2APBS1 and 116-2 grow at high salt (3% NaCl), low pH (3.5) and tolerate high concentrations of nitrate (400mM) and nitrite (100mM). Strain 2APBS1 was demonstrated to grow at in situ acidic pHs down to 2.5. (4) R. denitrificans strain 2APBS1 is the first described Rhodanobacter species shown to denitrify. Nitrate is almost entirely converted to N2O, which may account for the large accumulation of N2O in the ORFRC subsurface. (5) G. daltonii, isolated from uranium- and hydrocarbon-contaminated subsurface sediments of the ORFRC, is the first organism from the subsurface clade of the genus Geobacter that is capable of growth on aromatic hydrocarbons. (6) High quality draft genome sequences and a complete eco-physiological description are completed for R. denitrificans strain 2APBS1 and G. daltonii strain FRC-32. (7) Given their demonstrated relevance to DOE remediation efforts and the availability of detailed genotypic/phenotypic characterization, Rhodanobacter denitrificans strain 2APBS1 and Geobacter daltonii strain FRC-32 represent ideal model organisms to provide a predictive understanding of subsurface microbial activity through metabolic modeling. Tasks II and III-Diversity and distribution of active anaerobes and Mechanisms linking electron transport and the fate of radionuclides: (1) Our study showed that members of genus Rhodanobacter and Geobacter are abundant and active in the uranium and nitrate contaminated subsurface. In the contaminant source zone of the Oak Ridge site, Rhodanobacter spp. are the predominant, active organisms detected

  5. Evaluation of the Universal Viral Transport system for long-term storage of virus specimens for microbial forensics.

    Science.gov (United States)

    Hosokawa-Muto, Junji; Fujinami, Yoshihito; Mizuno, Natsuko

    2015-08-01

    Forensic microbial specimens, including bacteria and viruses, are collected at biocrime and bioterrorism scenes. Although it is preferable that the pathogens in these samples are alive and kept in a steady state, the samples may be stored for prolonged periods before analysis. Therefore, it is important to understand the effects of storage conditions on the pathogens contained within such samples. To evaluate the capacity to preserve viable virus and the viral genome, influenza virus was added to the transport medium of the Universal Viral Transport system and stored for over 3 months at various temperatures, after which virus titrations and quantitative analysis of the influenza hemagglutinin gene were performed. Although viable viruses became undetectable 29 days after the medium was stored at room temperature, viruses in the medium stored at 4°C were viable even after 99 days. A quantitative PCR analysis indicated that the hemagglutinin gene was maintained for 99 days at both 4°C and room temperature. Therefore, long-term storage at 4°C has little effect on viable virus and viral genes, so the Universal Viral Transport system can be useful for microbial forensics. This study provides important information for the handling of forensic virus specimens. Copyright © 2015 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  6. Quantifying accelerated soil erosion through ecological site-based assessments of wind and water erosion

    Science.gov (United States)

    This work explores how organising soil erosion assessments using established groupings of similar soils (ecological sites) can inform systems for managing accelerated soil erosion. We evaluated aeolian sediment transport and fluvial erosion rates for five ecological sites in southern New Mexico, USA...

  7. Transport of microbial tracers in clean and organically contaminated silica sand in laboratory columns compared with their transport in the field

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, Louise, E-mail: louise.weaver@esr.cri.nz; Sinton, Lester W.; Pang, Liping; Dann, Rod; Close, Murray

    2013-01-15

    Waste disposal on land and the consequent transport of bacterial and viral pathogens in soils and aquifers are of major concern worldwide. Pathogen transport can be enhanced in the presence of organic matter due to occupation of attachment sites in the aquifer materials thus preventing pathogen attachment leading to their faster transport for longer distances. Laboratory column studies were carried out to investigate the effect of organic matter, in the form of dissolved organic carbon (DOC), on the transport of Escherichia coli and MS2 phage in saturated clean silica sand. Transport rates of these microbial tracers were also studied in a contaminated field site. Laboratory column studies showed that low concentrations (0.17 mg L{sup −1}) of DOC had little effect on E. coli J6-2 removal and slightly reduced the attachment of MS2 phage. After progressive conditioning of the column with DOC (1.7 mg L{sup −1} and 17 mg L{sup −1}), neither E. coli J6-2 nor MS2 phage showed any attachment and recovery rates increased dramatically (up to 100%). The results suggest that DOC can affect the transport rates of microbial contaminants. For E. coli J6-2 the predominant effect appeared to be an increase in the secondary energy minimum leading to an increase in E. coli attachment initially. However, after 17 mg L{sup −1} DOC conditioning of the silica sand no attachment of E. coli was observed as the DOC took up attachment sites in the porous media. MS2 phage appeared to be affected predominantly by out-competition of binding sites in the clean silica sand and a steady reduction in attachment was observed as the DOC conditioning increased. Field study showed a high removal of both E. coli and MS2 phage, although E. coli was removed at a lower rate than MS2 phage. In the field it is likely that a combination of effects are seen as the aquifer material will be heterogeneous in its surface nanoscale properties, demonstrated by the differing removal of E. coli and MS2 phage

  8. The importance of OH − transport through anion exchange membrane in microbial electrolysis cells

    KAUST Repository

    Ye, Yaoli; Logan, Bruce

    2018-01-01

    In two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact

  9. Description of the microbial ecology evaluation device, flight equipment, and ground transporter

    Science.gov (United States)

    Chassay, C. E.; Taylor, G. R.

    1973-01-01

    Exposure of test systems in space required the fabrication of specialized hardware termed a Microbial Ecology Evaluation Device that had individual test chambers and a complex optical filter system. The characteristics of this device and the manner in which it was deployed in space are described.

  10. A generic transport-reactive model for simulating microbially influenced mineral precipitation in porous medium

    NARCIS (Netherlands)

    Zhou, J.; Van Turnhout, A.G.; Heimovaara, T.J.; Afanasyev, M.

    2015-01-01

    The spatial and temporal distribution of precipitated minerals is one of the key factors governing various processes in the sub-surface environment, including microbially influenced corrosion (MIC) (Huang, 2002), bio-cementation (van Paassen et al., 2010) and sediment diagenesis (Paraska et al.,

  11. The influence of rill density on soil erosion against USLE-soil erosion methode

    OpenAIRE

    Rizalihadi, A.M.; Faimah, B.E.; Nazia, C.L.

    2013-01-01

    Land and water is one of the major natural resource which has an important role for human life. Exploitation of land in catchment areas that not correspond to its carrying capacity will cause damage. One of the effect is increassing the soil erosion. Continuous erosion will also lead to increased sediment transport in rivers that disrupt the ship navigation on estuary due sediment accumulation. At present, soil erosion is estimated using USLE method, which is only limited to the erosion in th...

  12. Radiochemically-Supported Microbial Communities: A Potential Mechanism for Biocolloid Production of Importance to Actinide Transport

    Energy Technology Data Exchange (ETDEWEB)

    Moser, Duane P. [Desert Research Inst., Nevada University, Reno, NV (United States); Hamilton-Brehm, Scott D. [Desert Research Inst., Nevada University, Reno, NV (United States); Fisher, Jenny C. [Desert Research Inst., Nevada University, Reno, NV (United States); Bruckner, James C. [Desert Research Inst., Nevada University, Reno, NV (United States); Kruger, Brittany [Desert Research Inst., Nevada University, Reno, NV (United States); Sackett, Joshua [Desert Research Inst., Nevada University, Reno, NV (United States); Russell, Charles E. [Desert Research Inst., Nevada University, Reno, NV (United States); Onstott, Tullis C. [Princeton Univ., NJ (United States); Czerwinski, Ken [Univ. of Nevada, Las Vegas, NV (United States); Zavarin, Mavrik [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Campbell, James H. [Northwest Missouri State Univ., Maryville, MO (United States)

    2014-06-01

    Due to the legacy of Cold War nuclear weapons testing, the Nevada National Security Site (NNSS, formerly known as the Nevada Test Site (NTS)) contains millions of Curies of radioactive contamination. Presented here is a summary of the results of the first comprehensive study of subsurface microbial communities of radioactive and nonradioactive aquifers at this site. To achieve the objectives of this project, cooperative actions between the Desert Research Institute (DRI), the Nevada Field Office of the National Nuclear Security Administration (NNSA), the Underground Test Area Activity (UGTA), and contractors such as Navarro-Interra (NI), were required. Ultimately, fluids from 17 boreholes and two water-filled tunnels were sampled (sometimes on multiple occasions and from multiple depths) from the NNSS, the adjacent Nevada Test and Training Range (NTTR), and a reference hole in the Amargosa Valley near Death Valley. The sites sampled ranged from highly-radioactive nuclear device test cavities to uncontaminated perched and regional aquifers. Specific areas sampled included recharge, intermediate, and discharge zones of a 100,000-km2 internally-draining province, known as the Death Valley Regional Flow System (DVRFS), which encompasses the entirety of the NNSS/NTTR and surrounding areas. Specific geological features sampled included: West Pahute and Ranier Mesas (recharge zone), Yucca and Frenchman Flats (transitional zone), and the Western edge of the Amargosa Valley near Death Valley (discharge zone). The original overarching question underlying the proposal supporting this work was stated as: Can radiochemically-produced substrates support indigenous microbial communities and subsequently stimulate biocolloid formation that can affect radionuclides in NNSS subsurface nuclear test/detonation sites? Radioactive and non-radioactive groundwater samples were thus characterized for physical parameters, aqueous geochemistry, and microbial communities using both DNA- and

  13. Bentonite erosion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2009-12-15

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  14. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

    2009-12-01

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  15. Modeling radiocesium transport from a river catchment based on a physically-based distributed hydrological and sediment erosion model.

    Science.gov (United States)

    Kinouchi, Tsuyoshi; Yoshimura, Kazuya; Omata, Teppei

    2015-01-01

    The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in March 2011 resulted in the deposition of large quantities of radionuclides, such as (134)Cs and (137)Cs, over parts of eastern Japan. Since then high levels of radioactive contamination have been detected in large areas, including forests, agricultural land, and residential areas. Due to the strong adsorption capability of radiocesium to soil particles, radiocesium migrates with eroded sediments, follows the surface flow paths, and is delivered to more populated downstream regions and eventually to the Pacific Ocean. It is therefore important to understand the transport of contaminated sediments in the hydrological system and to predict changes in the spatial distribution of radiocesium concentrations by taking the land-surface processes related to sediment migration into consideration. In this study, we developed a distributed model to simulate the transport of water and contaminated sediment in a watershed hydrological system, and applied this model to a partially forested mountain catchment located in an area highly contaminated by the radioactive fallout. Observed discharge, sediment concentration, and cesium concentration measured from June 2011 until December 2012 were used for calibration of model parameters. The simulated discharge and sediment concentration both agreed well with observed values, while the cesium concentration was underestimated in the initial period following the accident. This result suggests that the leaching of radiocesium from the forest canopy, which was not considered in the model, played a significant role in its transport from the catchment. Based on the simulation results, we quantified the long-term fate of radiocesium over the study area and estimated that the effective half-life of (137)Cs deposited in the study area will be approximately 22 y due to the export of contaminated sediment by land-surface processes, and the amount of (137)Cs remaining in the

  16. Erhversbetinget erosion?

    DEFF Research Database (Denmark)

    Dige, Irene; Gjørup, Hans; Nyvad, Bente

    2012-01-01

    Baggrund – I forbindelse med dental erosion er en grundig udredning af patienten vigtig, således at årsagen til erosionernes opståen findes, og der kan iværksættes adækvat forebyggende indsats. En sådan udredning er ikke mindst vigtig, når arbejdsmiljøet mistænkes. Patienttilfælde – En 30-årig...... arbejdsskade, men ikke anerkendt, da erosioner ikke er optaget på Arbejdsskadestyrelsens liste over erhvervssygdomme. En systematisk registrering af lignende tilfælde kunne imidlertid på sigt ændre retspraksis for fremtidige patienter med arbejdsbetinget erosion....... patient, der arbejder som pladesmed, blev henvist til Landsdels- og Videnscenter, Århus Sygehus, med henblik på udredning af patientens kraftige slid. Patienten udviste ikke-alderssvarende tandslid af emalje og dentin svarende til erosion forårsaget af syredampe i arbejdsmiljøet, muligvis forstærket af...

  17. Categorization of erosion control matting for slope applications.

    Science.gov (United States)

    2013-12-25

    Erosion control is an important aspect of any Georgia Department of Transportation (GDOT) construction project, with the extreme negative impacts of high sediment loads in natural waterways having been well documented. Selection of a proper erosion c...

  18. Microbially Induced Calcite Precipitation (MICP) - A Technology for Managing Flow and Transport in Porous and Fractured Media

    Science.gov (United States)

    Phillips, A. J.; Hiebert, R.; Kirksey, J.; Lauchnor, E. G.; Rothman, A.; Spangler, L.; Esposito, R.; Gerlach, R.; Cunningham, A. B.

    2014-12-01

    Certain microorganisms e.g., Sporosarcina pasteurii contribute enzymes that catalyze reactions which in the presence of calcium, can create saturation conditions favorable for calcium carbonate precipitation (microbially-induced calcium carbonate precipitation (MICP)). MICP can be used for a number of engineering applications including securing geologic storage of CO2 or other fluids by sealing fractures, improving wellbore integrity, and stabilizing fractured and unstable porous media. MICP treatment has the advantage of the use of small microorganisms, ~2μm, suggesting applicability to treatment of small aperture fractures not accessible to traditional treatments, for example the use of fine cement. The promotion of MICP in the subsurface is a complex reactive transport problem coupling microbial, abiotic (geochemical), geomechanical and hydrodynamic processes. In the laboratory, MICP has been demonstrated to cement together heavily fractured shale and reduce the permeability of fractures in shale and sandstone cores up to five orders of magnitude under both ambient and subsurface relevant pressure conditions (Figure 1). Most recently, a MICP fracture treatment field study was performed at a well at the Southern Company Gorgas Steam Generation Plant (Alabama) (Figure 1). The Fayetteville Sandstone at approximately 1120' below ground surface was hydraulically fractured prior to MICP treatment. After 4 days of injection of 24 calcium pulses and 6 microbial inoculations, injectivity of brine into the formation was significantly reduced. The experiment also resulted in a reduction in pressure decay which is a measure of improved wellbore integrity. These promising results suggest the potential for MICP treatment to seal fractured pathways at the field scale to improve the long-term security of geologically-stored carbon dioxide or prevent leakage of shale gas or hydraulic fracturing fluids into functional overlying aquifers, reducing environmental impacts.

  19. Microbial mediation of radionuclide transport -significance for the nuclear fuel waste management program

    International Nuclear Information System (INIS)

    Champ, D.R.

    1984-08-01

    The role that microbially catalyzed processes may play in determining, or altering, radionuclide migration is an unresolved question in the Nuclear Fuel Waste Management Program. This report documents the results of a review of the available information on the existence and biochemical capabilities of micro-organisms and the potential for their involvement in processes affecting the migration of radionuclides of interest. The potential was judged sufficient to warrant conducting experiments to assess their role. The outline of an experimental program to address the role of micro-organisms is presented

  20. Radiochemically-supported microbial communities. A potential mechanism for biocolloid production of importance to actinide transport

    Energy Technology Data Exchange (ETDEWEB)

    Moser, Duane P. [Desert Research Institute, Las Vegas, NV (United States); Hamilton-Brehm, Scott D. [Desert Research Institute, Las Vegas, NV (United States); Fisher, Jenny C. [Univ. of Wisconsin, Milwaukee, WI (United States); Bruckner, James C. [Desert Research Institute, Las Vegas, NV (United States); Kruger, Brittany [Desert Research Institute, Las Vegas, NV (United States); Sackett, Joshua [Desert Research Institute, Las Vegas, NV (United States); Russell, Charles E. [Desert Research Institute, Las Vegas, NV (United States); Onstott, Tullis C. [Princeton Univ., NJ (United States); Czerwinski, Ken [Univ. of Nevada, Las Vegas, NV (United States); Zavarin, Mavrik [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Campbell, James H. [Northwest Missouri State Univ., Maryville, MO (United States)

    2015-03-20

    The work described here revealed the presence of diverse microbial communities located across 19 subsurface sites at the NNSS/NTTR and nearby locations. Overall, the diversity of microorganisms was high for subsurface habitats and variable between sites. As of this writing, preparations are being made to combine the Illumina sequences and 16S rRNA clone libraries with other non-NNSS/NTTR well sites of Southern Nevada Regional Flow System for a publication manuscript describing our very broad landscape scale survey of subsurface microbial diversity. Isolates DRI-13 and DRI-14 remain to be fully characterized and named in accordance with the conventions established by Bergey's Manual of Systematic Bacteriology. In preparation to be published, these microorganisms will be submitted to the American Type Culture Collection (ATCC) and the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (DSMZ).It is anticipated that the data resulting from this study in combination with other data sets that will allow us to produce a number of publications that will be impactful to the subsurface microbiology community.

  1. Interrill soil erosion processes on steep slopes

    Science.gov (United States)

    To date interrill erosion processes and regimes are not fully understood. The objectives are to 1) identify the erosion regimes and limiting processes between detachment and transport on steep slopes, 2) characterize the interactive effects between rainfall intensity and flow depth on sediment trans...

  2. Wind erosion modelling in a Sahelian environment

    NARCIS (Netherlands)

    Faye-Visser, S.M.; Sterk, G.; Karssenberg, D.

    2005-01-01

    In the Sahel field observations of wind-blown mass transport often show considerable spatial variation related to the spatial variation of the wind erosion controlling parameters, e.g. soil crust and vegetation cover. A model, used to predict spatial variation in wind erosion and deposition is a

  3. The comparison of various approach to evaluation erosion risks and design control erosion measures

    Science.gov (United States)

    Kapicka, Jiri

    2015-04-01

    In the present is in the Czech Republic one methodology how to compute and compare erosion risks. This methodology contain also method to design erosion control measures. The base of this methodology is Universal Soil Loss Equation (USLE) and their result long-term average annual rate of erosion (G). This methodology is used for landscape planners. Data and statistics from database of erosion events in the Czech Republic shows that many troubles and damages are from local episodes of erosion events. An extent of these events and theirs impact are conditional to local precipitation events, current plant phase and soil conditions. These erosion events can do troubles and damages on agriculture land, municipally property and hydro components and even in a location is from point of view long-term average annual rate of erosion in good conditions. Other way how to compute and compare erosion risks is episodes approach. In this paper is presented the compare of various approach to compute erosion risks. The comparison was computed to locality from database of erosion events on agricultural land in the Czech Republic where have been records two erosion events. The study area is a simple agriculture land without any barriers that can have high influence to water flow and soil sediment transport. The computation of erosion risks (for all methodology) was based on laboratory analysis of soil samples which was sampled on study area. Results of the methodology USLE, MUSLE and results from mathematical model Erosion 3D have been compared. Variances of the results in space distribution of the places with highest soil erosion where compared and discussed. Other part presents variances of design control erosion measures where their design was done on based different methodology. The results shows variance of computed erosion risks which was done by different methodology. These variances can start discussion about different approach how compute and evaluate erosion risks in areas

  4. Modelling sewer sediment deposition, erosion, and transport processes to predict acute influent and reduce combined sewer overflows and CO(2) emissions.

    Science.gov (United States)

    Mouri, Goro; Oki, Taikan

    2010-01-01

    Understanding of solids deposition, erosion, and transport processes in sewer systems has improved considerably in the past decade. This has provided guidance for controlling sewer solids and associated acute pollutants to protect the environment and improve the operation of wastewater systems. Although measures to decrease combined sewer overflow (CSO) events have reduced the amount of discharged pollution, overflows continue to occur during rainy weather in combined sewer systems. The solution lies in the amount of water allotted to various processes in an effluent treatment system, in impact evaluation of water quality and prediction technology, and in stressing the importance of developing a control technology. Extremely contaminated inflow has been a serious research subject, especially in connection with the influence of rainy weather on nitrogen and organic matter removal efficiency in wastewater treatment plants (WWTP). An intensive investigation of an extremely polluted inflow load to WWTP during rainy weather was conducted in the city of Matsuyama, the region used for the present research on total suspended solid (TSS) concentration. Since the inflow during rainy weather can be as much as 400 times that in dry weather, almost all sewers are unsettled and overflowing when a rain event is more than moderate. Another concern is the energy consumed by wastewater treatment; this problem has become important from the viewpoint of reducing CO(2) emissions and overall costs. Therefore, while establishing a prediction technology for the inflow water quality characteristics of a sewage disposal plant is an important priority, the development of a management/control method for an effluent treatment system that minimises energy consumption and CO(2) emissions due to water disposal is also a pressing research topic with regards to the quality of treated water. The procedure to improve water quality must make use of not only water quality and biotic criteria, but also

  5. Sensitivity of Deep Soil Organic Carbon Age to Sorption, Transport and Microbial Interactions - Insights from a Calibrated Process Model

    Science.gov (United States)

    Ahrens, B.; Schrumpf, M.; Reichstein, M.

    2013-12-01

    Subsoil soil organic carbon (SOC) is characterized by conventional radiocarbon ages on the order of centuries to millennia. Most vertically explicit SOC turnover models represent this persistence of deep SOC by one pool that has millennial turnover times. This approach lumps different stabilizing mechanisms such as chemical recalcitrance, sorptive stabilization and energy limitation into a single rate constant. As an alternative, we present a continuous, vertically explicit SOC decomposition model that allows for stabilization via sorption and microbial interactions (COMISSION model). We compare the COMISSION model with the SOC profile of a Haplic Podzol under a Norway spruce forest. In the COMISSION model two pools receive aboveground litter input and vertically distributed root litter input. The readily leachable and soluble fraction of litter input enters a dissolved organic carbon pool (DOC), while the rest enters the residue pool which represents polymeric, non-soluble SOC. The residue pool is depolymerized with extracellular enzymes produced by a microbial pool to enter the DOC pool which represents SOC potentially available for assimilation by microbes. The adsorption/desorption of DOC from/to mineral surfaces controls the availability of carbon in the DOC pool for assimilatory uptake by microbes. The sorption of DOC is modeled with dynamic Langmuir equations. The desorbed part of the DOC pool not only constitutes the substrate for the microbial pool, but is also transported via advection. Interactions of microbes with the residue and DOC pool are modeled with Michaelis-Menten kinetics - this not only allows representing ';priming', but also the retardation of decomposition via energy limitation in the deep soil where substrate is scarce. Further, soil organic matter is recycled within the soil profile through microbial processing - dead microbes either enter the DOC or the residue pool, and thereby also contribute to longer residence times with soil depth

  6. Metal Transport, Heavy Metal Speciation and Microbial Fixation Through Fluvial Subenvironments, Lower Coeur D'Alene River Valley, Idaho

    Science.gov (United States)

    Hooper, R. L.; Mahoney, J. B.

    2001-12-01

    The lower Coeur d'Alene River Valley of northern Idaho is the site of extensive lead and zinc contamination resulting from both direct riverine tailings disposal and flood remobilization of contaminated sediments derived from the Coeur d'Alene mining district upstream. Variations in the hydrologic regime, redox conditions, porosity/permeability, organic content and microbial activity results in complicated metal transport pathways. Documentation of these pathways is a prerequisite to effective remediation, and requires accurate analysis of lateral and vertical variations. An analytical approach combining sequential extraction, electron microscopy, and microanalysis provides a comprehensive assessment of particulate speciation in this complex hydrologic system. Rigorously controlled sample preparation and a new sequential extraction protocol provide unprecedented insight into the role of metal sequestration in fluvial subenvironments. Four subenvironments were investigated: bedload, overbank (levee), marsh, and lacustrine. Periodic floods remobilize primary ore minerals and secondary minerals from upstream tailings (primarily oxyhydroxides, sulfides and carbonates). The bedload in the lower valley is a reducing environment and acts as a sink for detrital carbonates and sulfides moving downstream. In addition, authigenic/biogenic Fe, Pb and Zn sulfides and phosphates are common in bedload sediments near the sediment/water interface. Flood redistribution of oxide, sulfide and carbonate phases results in periodic contaminant recharge generating a complex system of metal dissolution, mobilization, migration and precipitation. In levee environments, authigenic sulfides from flood scouring are quickly oxidized resulting in development of oxide coated grain surfaces. Stability of detrital minerals on the levee is variable depending on sediment permeability, grain size and mineralogy resulting in a complex stratigraphy of oxide zones mottled with zones dominated by detrital

  7. Long distance electron transport in marine sediments: Microbial and geochemical implications

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Larsen, Steffen; Pfeffer, Christian

    and promotes the formation of Mg-calcite and iron oxides in the oxic zone. Oxygen seems to be the major electron acceptor, and more than 40% of the oxygen consumption in sediments can be driven by long distance electron transfer from distant electron donors. The major e-donor is sulfide, which is oxidized......Anaerobic oxidation of organic matter in marine sediment is traditionally considered to be coupled to oxygen reduction via a cascade of redox processes and transport of intermittent electron donors and acceptors. Electric currents have been found to shortcut this cascade and directly couple...... oxidation of sulphide centimeters down in marine sediment to the reduction of oxygen at the very surface1 . This electric coupling of spatially separated redox half-reactions seems to be mediated by centimeter long filamentous Desulfubulbus affiliated bacteria with morphological and ultra...

  8. Rainfall Erosivity in Europe

    DEFF Research Database (Denmark)

    Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale

    2015-01-01

    Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the Rfactor in the USLE model and its revised version, RUSLE. At national...... and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based...

  9. Sediment transport dynamics in the Central Himalaya: assessing during monsoon the erosion processes signature in the daily suspended load of the Narayani river

    Science.gov (United States)

    Morin, Guillaume; Lavé, Jérôme; Lanord, Christian France; Prassad Gajurel, Ananta

    2017-04-01

    The evolution of mountainous landscapes is the result of competition between tectonic and erosional processes. In response to the creation of topography by tectonics, fluvial, glacial, and hillslope denudation processes erode topography, leading to rock exhumation and sediment redistribution. When trying to better document the links between climate, tectonic, or lithologic controls in mountain range evolution, a detailed understanding of the influence of each erosion process in a given environment is fundamental. At the scale of a whole mountain range, a systematic survey and monitoring of all the geomorphologic processes at work can rapidly become difficult. An alternative approach can be provided by studying the characteristics and temporal evolution of the sediments exported out of the range. In central Himalaya, the Narayani watershed presents contrasted lithologic, geochemical or isotopic signatures of the outcropping rocks as well as of the erosional processes: this particular setting allows conducting such type of approach by partly untangling the myopic vision of the spatial integration at the watershed scale. Based on the acquisition and analysis of a new dataset on the daily suspended load concentration and geochemical characteristics at the mountain outlet of one of the largest Himalayan rivers (drainage area = 30000 km2) bring several important results on Himalayan erosion, and on climatic and process controls. 1. Based on discrete depth sampling and on daily surface sampling of suspended load associated to flow characterization through ADCP measurements, we were first able to integrate sediment flux across a river cross-section and over time. We estimate for 2010 year an equivalent erosion rate of 1.8 +0.35/-0.2 mm/yr, and over the last 15 years, using past sediment load records from the DHM of Nepal, an equivalent erosion rate of 1.6 +0.3/-0.2 mm/yr. These rates are also in close agreement with the longer term ( 500 yrs) denudation rates of 1.7 mm

  10. Numerical modelling of biophysicochemical effects on multispecies reactive transport in porous media involving Pseudomonas putida for potential microbial enhanced oil recovery application.

    Science.gov (United States)

    Sivasankar, P; Rajesh Kanna, A; Suresh Kumar, G; Gummadi, Sathyanarayana N

    2016-07-01

    pH and resident time of injected slug plays a critical role in characterizing the reservoir for potential microbial enhanced oil recovery (MEOR) application. To investigate MEOR processes, a multispecies (microbes-nutrients) reactive transport model in porous media was developed by coupling kinetic and transport model. The present work differs from earlier works by explicitly determining parametric values required for kinetic model by experimental investigations using Pseudomonas putida at different pH conditions and subsequently performing sensitivity analysis of pH, resident time and water saturation on concentrations of microbes, nutrients and biosurfactant within reservoir. The results suggest that nutrient utilization and biosurfactant production are found to be maximum at pH 8 and 7.5 respectively. It is also found that the sucrose and biosurfactant concentrations are highly sensitive to pH rather than reservoir microbial concentration, while at larger resident time and water saturation, the microbial and nutrient concentrations were lesser due to enhanced dispersion. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Mapping erosion from space

    NARCIS (Netherlands)

    Vrieling, A.

    2007-01-01

    Soil erosion by water is the most important land degradation problem worldwide. Spatial information on erosion is required for defining effective soil and water conservation strategies. Satellite remote sensing can provide relevant input to regional erosion assessment. This thesis comprises a review

  12. Erosion-corrosion

    International Nuclear Information System (INIS)

    Aghili, B.

    1999-05-01

    A literature study on erosion-corrosion of pipings in the nuclear industry was performed. Occurred incidents are reviewed, and the mechanism driving the erosion-corrosion is described. Factors that influence the effect in negative or positive direction are treated, as well as programs for control and inspection. Finally, examples of failures from databases on erosion-corrosion are given in an attachment

  13. Assessing storm erosion hazards

    NARCIS (Netherlands)

    Ranasinghe, Ranasinghe W M R J B; Callaghan, D.; Ciavola, Paolo; Coco, Giovanni

    2017-01-01

    The storm erosion hazard on coasts is usually expressed as an erosion volume and/or associated episodic coastline retreat. The accurate assessment of present-day and future storm erosion volumes is a key task for coastal zone managers, planners and engineers. There are four main approaches that can

  14. STWIR, a microorganism transport with infiltration and runoff add-on module for the KINEROS2 runoff and erosion model: documentation and user manual

    Science.gov (United States)

    Runoff from manured fields is often considered to be the source of microorganisms in the surface water used for irrigation, recreation, and household needs. Concerns about microbial safety of this water resulted in development of predictive models for estimating the concentrations and total numbers ...

  15. Managing dental erosion.

    Science.gov (United States)

    Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

    2012-01-01

    The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

  16. Microbial air quality in mass transport buses and work-related illness among bus drivers of Bangkok Mass Transit Authority.

    Science.gov (United States)

    Luksamijarulkul, Pipat; Sundhiyodhin, Viboonsri; Luksamijarulkul, Soavalug; Kaewboonchoo, Orawan

    2004-06-01

    The air quality in mass transport buses, especially air-conditioned buses may affect bus drivers who work full time. Bus numbers 16, 63, 67 and 166 of the Seventh Bus Zone of Bangkok Mass Transit Authority were randomly selected to investigate for microbial air quality. Nine air-conditioned buses and 2-4 open-air buses for each number of the bus (36 air-conditioned buses and 12 open-air buses) were included. Five points of in-bus air samples in each studied bus were collected by using the Millipore A ir Tester Totally, 180 and 60 air samples collected from air-conditioned buses and open-air buses were cultured for bacterial and fungal counts. The bus drivers who drove the studied buses were interviewed towards histories of work-related illness while working. The results revealed that the mean +/- SD of bacterial counts in the studied open-air buses ranged from 358.50 +/- 146.66 CFU/m3 to 506 +/- 137.62 CFU/m3; bus number 16 had the highest level. As well as the mean +/- SD of fungal counts which ranged from 93.33 +/- 44.83 CFU/m3 to 302 +/- 294.65 CFU/m3; bus number 166 had the highest level. Whereas, the mean +/- SD of bacterial counts in the studied air-conditioned buses ranged from 115.24 +/- 136.01 CFU/m3 to 244.69 +/- 234.85 CFU/m3; bus numbers 16 and 67 had the highest level. As well as the mean +/- SD of fungal counts which rangedfrom 18.84 +/- 39.42 CFU/m3 to 96.13 +/- 234.76 CFU/m3; bus number 166 had the highest level. When 180 and 60 studied air samples were analyzed in detail, it was found that 33.33% of the air samples from open-air buses and 6.11% of air samples from air-conditioned buses had a high level of bacterial counts (> 500 CFU/m3) while 6.67% of air samples from open-air buses and 2.78% of air samples from air-conditioned buses had a high level of fungal counts (> 500 CFU/m3). Data from the history of work-related illnesses among the studied bus drivers showed that 91.67% of open-air bus drivers and 57.28% of air-conditioned bus drivers had

  17. Accumulation and transport of microbial-size particles in a pressure protected model burn unit: CFD simulations and experimental evidence

    Directory of Open Access Journals (Sweden)

    Mimoun Maurice

    2011-03-01

    Full Text Available Abstract Background Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD. Methods The study was carried out in 4 steps: i patient room design, ii CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii construction of a prototype room and subsequent experimental studies to characterize its performance iv qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF open-source software Code_Saturne® (http://www.code-saturne.org was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. Results We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to

  18. Erosion and stability of a mine soil

    International Nuclear Information System (INIS)

    Wu, T.H.; Stadler, A.T.; Low, C.

    1996-01-01

    Mine soils developed from mine spoils commonly have a wide range of particle size. The slopes of old spoil piles usually are marked by gullies due to years of uncontrolled erosion. These characteristics raise questions about applicability of available theories and models for estimating runoff and erosion. An investigation was made to determine whether available erosion models can work for mine soils and can account for gully erosion. The investigation at an abandoned surface mine consisted of measurement of soil and sediment properties, measurement of runoff and erosion, observations of armor by rock fragments on gully floor, and calculations with available theories of sediment transport and slope stability. The results at this site suggest that (1) predictions with the ANSWERS model have about the same accuracy as those made for agricultural lands; (2) armor provided by rock fragments are temporary as they are periodically removed by debris flows; (3) detachment by rainfall impact is the primary cause of erosion on short steep slopes; and (4) a simplified method can be used for estimating erosion on such slopes

  19. Short review of runoff and erosion physically based models

    Directory of Open Access Journals (Sweden)

    Gabrić Ognjen

    2015-01-01

    Full Text Available Processes of runoff and erosion are one of the main research subjects in hydrological science. Based on the field and laboratory measurements, and analogous with development of computational techniques, runoff and erosion models based on equations which describe the physics of the process are also developed. Several models of runoff and erosion which describes entire process of genesis and sediment transport on the catchment are described and compared.

  20. Protection from erosion following wildfire

    Science.gov (United States)

    Peter R. Robichaud; William J. Elliot

    2006-01-01

    Erosion in the first year after a wildfire can be up to three orders of magnitude greater than the erosion from undisturbed forests. To mitigate potential postfire erosion, various erosion control treatments are applied on highly erodible areas with downstream resources in need of protection. Because postfire erosion rates generally decline by an order of magnitude for...

  1. Saliva and dental erosion

    Directory of Open Access Journals (Sweden)

    Marília Afonso Rabelo Buzalaf

    2012-10-01

    Full Text Available Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results: Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions: Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  2. Saliva and dental erosion.

    Science.gov (United States)

    Buzalaf, Marília Afonso Rabelo; Hannas, Angélicas Reis; Kato, Melissa Thiemi

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. This review discusses the role of salivary factors on the development of dental erosion. A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  3. Erosion corrosion in wet steam

    International Nuclear Information System (INIS)

    Tavast, J.

    1988-03-01

    The effect of different remedies against erosion corrosion in wet steam has been studied in Barsebaeck 1. Accessible steam systems were inspected in 1984, 1985 and 1986. The effect of hydrogen peroxide injection of the transport of corrosion products in the condensate and feed water systems has also been followed through chemical analyses. The most important results of the project are: - Low alloy chromium steels with a chromium content of 1-2% have shown excellent resistance to erosion corrosion in wet steam. - A thermally sprayed coating has shown good resistance to erosion corrosion in wet steam. In a few areas with restricted accessibility minor attacks have been found. A thermally sprayed aluminium oxide coating has given poor results. - Large areas in the moisture separator/reheater and in steam extraction no. 3 have been passivated by injection of 20 ppb hydrogen peroxide to the high pressure steam. In other inspected systems no significant effect was found. Measurements of the wall thickness in steam extraction no. 3 showed a reduced rate of attack. - The injection of 20 ppb hydrogen peroxide has not resulted in any significant reduction of the iron level result is contrary to that of earlier tests. An increase to 40 ppb resulted in a slight decrease of the iron level. - None of the feared disadvantages with hydrogen peroxide injection has been observed. The chromium and cobalt levels did not increase during the injection. Neither did the lifetime of the precoat condensate filters decrease. (author)

  4. Challenges in soil erosion research and prediction model development

    Science.gov (United States)

    Quantification of soil erosion has been traditionally considered as a surface hydrologic process with equations for soil detachment and sediment transport derived from the mechanics and hydraulics of the rainfall and surface flow. Under the current erosion modeling framework, the soil has a constant...

  5. Parameterization of erodibility in the Rangeland Hydrology and Erosion Model

    Science.gov (United States)

    The magnitude of erosion from a hillslope is governed by the availability of sediment and connectivity of runoff and erosion processes. For undisturbed rangelands, sediment is primarily detached and transported by rainsplash and sheetflow (splash-sheet) processes in isolated bare batches, but sedime...

  6. Non-Fluvial Controls of Erosion, Sediment Transport and Fluvial Morphology in a mid-Atlantic Piedmont Watershed, White Clay Creek, Pennsylvania, U.S.A.

    Science.gov (United States)

    McCarthy, K.; Affinito, R. A.; Pizzuto, J. E.; Stotts, S.; Henry, T.; Krauthauser, M.; O'Neal, M. A.

    2017-12-01

    Quantifying contemporary sediment budgets is essential for restoration and ecosystem management of mid-Atlantic watersheds, but relevant processes and controls are poorly understood. In the 153 km2 White Clay Creek watershed in southeastern Pennsylvania, longitudinal profiles reflect migration of knickpoints though bedrock over Quaternary timescales. In bank exposures along stream valleys, saprolite, bedrock, and matrix-supported cobbly and bouldery diamicton (likely colluvial) commonly underlie finer-grained clay, silt, sand, and gravel deposits of valley floor depositional environments. Overbank sedimentation rates were quantified by measuring the thickness of sediment deposited over the roots of floodplain trees. The sampled trees range in age from 25-270 years with median sediment accumulation rates of approximately 2 mm/yr (range 0-10 mm/yr). Rates of bank retreat (measured from historical aerial imagery or root-exposure dendrochronology) vary from 6-36 cm/yr, with median rates of 10 cm/yr. While bank erosion rates are subject to a variety of controls, including channel curvature, the density of riparian trees, and freeze-thaw processes, the strongest influence appears to be the grain size and thickness of bouldery diamicton exposed along the toes of retreating banks. Cobbles and boulders supplied by eroding diamicton also mantle the bed of the channel, such that 33- 80% of the bed material remains immobile at bankfull stage. A conceptual model of fluvial processes and sediment budgets for these channels must account for the watershed's history of changing climate, tectonics, and land use, requiring mapping of bedrock, colluvium, former mill dam sediments, and other non-alluvial deposits and controls. Efforts to apply hydraulic geometry principles (requiring a precise adjustment to contemporary hydraulic and sediment regime) or to treat these channels as traditional "threshold" rivers are unlikely to be successful.

  7. Distribution of erosion and deposition on the JET belt limiters

    International Nuclear Information System (INIS)

    McCracken, G.M.; Goodall, D.H.J.; Behrisch, R.; Roth, J.; Coad, J.P.; Harbour, P.; Kock, L. de; Pick, M.A.; Stangeby, P.C.

    1989-01-01

    The distribution of erosion and deposition of limiter material is of importance both for extrapolating to the next generation of fusion machines and for understanding impurity transport in the boundary layers of present day tokamaks. Erosion patterns have previously been reported for the JET discrete graphite limiters used up to 1986. We have now made measurements on the belt limiters used in 1987-88. These measurements show that although the pattern of net erosion is qualitatively similar to the earlier results the new maximum erosion (∼40μm) is reduced by about a factor 5, consistent with the larger limiter surface area. (author) 7 refs., 2 figs

  8. Divertor erosion in DIII-D

    International Nuclear Information System (INIS)

    Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P.; Wong, C.P.C.; Buzhinskij, O.I.; Opimach, I.V.

    1998-08-01

    Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point (OSP) of two divertor plasma conditions: attached (T e > 40 eV) ELMing plasmas, and detached (T e 2 . In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and redeposition of the carbon is well understood. In the attached cases, physical sputtering (with enhancement from self-sputtering and oblique incidence) is dominant, and the effective sputtering yield, Y, is greater than 10%. In ELM-free discharges, the total OSP net erosion rate is equal to the rate of carbon accumulation in the core plasma. For the detached divertor cases, the cold incident plasma eliminates physical sputtering. Attempts to measure chemically eroded hydrocarbon molecules spectroscopically indicate an upper limit of Y ≤ 0.1% for the chemical sputtering yield. Net erosion is suppressed at the outer strike-point, which becomes a region of net redeposition (∼ 4 cm/exposure-year). The private flux wall is measured to be a region of net redeposition with dense, high neutral pressure, attached divertor plasmas. Leading edges intercepting parallel heat flux (∼ 50 MW/m 2 ) have very high net erosion rates at the OSP of an attached plasma (∼ 10 microm/s > 1,000x erosion rate of aligned surfaces). Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor

  9. Divertor erosion in DIII-D

    International Nuclear Information System (INIS)

    Whyte, D.G.; Bastasz, R.; Wampler, W.R.; Brooks, J.N.; West, W.P.; Wong, C.P.C.

    1998-05-01

    Net erosion rates of carbon target plates have been measured in situ for the DIII-D lower divertor. The principal method of obtaining this data is the DiMES sample probe. Recent experiments have focused on erosion at the outer strike-point of two divertor plasma conditions: (1) attached (Te > 40 eV) ELMing plasmas and (2) detached (Te 10 cm/year, even with incident heat flux 2 . In this case, measurements and modeling agree for both gross and net carbon erosion, showing the near-surface transport and redeposition of the carbon is well understood and that effective sputtering yields are > 10%. In ELM-free discharges, this erosion rate can account for the rate of carbon accumulation in the core plasma. Divertor plasma detachment eliminates physical sputtering, while spectroscopically measured chemical erosion yields are also found to be low (Y(C/D + ) ≤ 2.0 x 10 -3 ). This leads to suppression of net erosion at the outer strike-point, which becomes a region of net redeposition (∼ 4 cm/year). The private flux wall is measured to be a region of net redeposition with dense, high neutral pressure, attached divertor plasmas. Leading edges intercepting parallel heat flux (∼ 50 MW/m 2 ) have very high net erosion rates (∼ 10 microm/s) at the OSP of an attached plasma. Leading edge erosion, and subsequent carbon redeposition, caused by tile gaps can account for half of the deuterium codeposition in the DIII-D divertor

  10. Combined Study of Titanium Dioxide Nanoparticle Transport and Toxicity on Microbial Nitrifying Communities under Single and Repeated Exposures in Soil Columns.

    Science.gov (United States)

    Simonin, Marie; Martins, Jean M F; Uzu, Gaëlle; Vince, Erwann; Richaume, Agnès

    2016-10-04

    Soils are exposed to nanoparticles (NPs) as a result of their increasing use in many commercial products. Adverse effects of NPs on soil microorganisms have been reported in several ecotoxicological studies using microcosms. Although repeated exposures are more likely to occur in soils, most of these previous studies were performed as a single exposure to NPs. Contrary to single contamination, the study of multiple NP contaminations in soils requires the use of specialized setups. Using a soil column experiment, we compared the influence of single and repeated exposures (one, two, or three exposures that resulted in the same final concentration applied) on the transport of titanium dioxide (TiO 2 ) NPs through soil and the effect of these different exposure scenarios on the abundance and activity of soil nitrifying microbial communities after a 2 month incubation. The transport of TiO 2 NPs was very limited under both single and repeated exposures and was highest for the lowest concentration injected during the first application. Significant decreases in nitrification activity and ammonia-oxidizing archaea and bacteria populations were observed only for the repeated exposure scenario (three TiO 2 NP contaminations). These results suggest that, under repeated exposures, the transport of TiO 2 NPs to deep soil layers and groundwater is limited and that a chronic contamination is more harmful for the soil microbiological functioning than a single exposure.

  11. Assessment of Soil Erosion Methods for Sludge Recovery, Savannah River Site

    National Research Council Canada - National Science Library

    Smith, Lawson

    1997-01-01

    ...) from selected storage tanks at the Savannah River Site (SRS) was assessed conceptually. Soil erosion methods are defined as the processes of soil detachment, entrainment, transport, and deposition...

  12. Measurement of erosion: Is it possible?

    NARCIS (Netherlands)

    Stroosnijder, L.

    2005-01-01

    Reasons for erosion measurements are: (1) to determine the environmental impact of erosion and conservation practices, (2) scientific erosion research; (3) development and evaluation of erosion control technology; (4) development of erosion prediction technology and (5) allocation of conservation

  13. Numerical modelling of concentrated leak erosion during Hole Erosion Tests

    OpenAIRE

    Mercier, F.; Bonelli, S.; Golay, F.; Anselmet, F.; Philippe, P.; Borghi, R.

    2015-01-01

    This study focuses on the numerical modelling of concentrated leak erosion of a cohesive soil by a turbulent flow in axisymmetrical geometry, with application to the Hole Erosion Test (HET). The numerical model is based on adaptive remeshing of the water/soil interface to ensure accurate description of the mechanical phenomena occurring near the soil/water interface. The erosion law governing the interface motion is based on two erosion parameters: the critical shear stress and the erosion co...

  14. Changes in micro-relief during different water erosive stages of purple soil under simulated rainfall.

    Science.gov (United States)

    Luo, Jian; Zheng, Zicheng; Li, Tingxuan; He, Shuqin

    2018-02-22

    This study investigated the variation characteristics of micro-topography during successive erosive stages of water erosion: splash erosion (SpE), sheet erosion (ShE), and rill erosion (RE). Micro-topography was quantified using surface elevation change, soil roughness (SR) and multifractal model. Results showed that the area of soil surface elevation decay increased gradually with the development of water erosion. With rainfall, the combined effects of the detachment by raindrop impact and the transport of runoff decreased SR, whereas rill erosion contributed to increase SR. With the increase in slope gradient, soil erosion area gradually decreased at the splash erosion stage. By contrast, soil erosion area initially decreased and then increased at the sheet and rill erosion stages. The width of the D q spectra (ΔD) values increased at the splash erosion stage and then decreased at the sheet and rill erosion stages on the 10° slope, opposite to that on the 15° slope. The ΔD values decreased with the evolution of water erosive stages on the 20° slope. The slope had an enhancing effect on the evolution of water erosion. In this study, we clarified the essence of micro-topography and laid a theoretical foundation for further understanding diverse hydrological processes.

  15. Rainfall erosivity in Europe.

    Science.gov (United States)

    Panagos, Panos; Ballabio, Cristiano; Borrelli, Pasquale; Meusburger, Katrin; Klik, Andreas; Rousseva, Svetla; Tadić, Melita Perčec; Michaelides, Silas; Hrabalíková, Michaela; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Beguería, Santiago; Alewell, Christine

    2015-04-01

    Rainfall is one the main drivers of soil erosion. The erosive force of rainfall is expressed as rainfall erosivity. Rainfall erosivity considers the rainfall amount and intensity, and is most commonly expressed as the R-factor in the USLE model and its revised version, RUSLE. At national and continental levels, the scarce availability of data obliges soil erosion modellers to estimate this factor based on rainfall data with only low temporal resolution (daily, monthly, annual averages). The purpose of this study is to assess rainfall erosivity in Europe in the form of the RUSLE R-factor, based on the best available datasets. Data have been collected from 1541 precipitation stations in all European Union (EU) Member States and Switzerland, with temporal resolutions of 5 to 60 min. The R-factor values calculated from precipitation data of different temporal resolutions were normalised to R-factor values with temporal resolutions of 30 min using linear regression functions. Precipitation time series ranged from a minimum of 5 years to a maximum of 40 years. The average time series per precipitation station is around 17.1 years, the most datasets including the first decade of the 21st century. Gaussian Process Regression (GPR) has been used to interpolate the R-factor station values to a European rainfall erosivity map at 1 km resolution. The covariates used for the R-factor interpolation were climatic data (total precipitation, seasonal precipitation, precipitation of driest/wettest months, average temperature), elevation and latitude/longitude. The mean R-factor for the EU plus Switzerland is 722 MJ mm ha(-1) h(-1) yr(-1), with the highest values (>1000 MJ mm ha(-1) h(-1) yr(-1)) in the Mediterranean and alpine regions and the lowest (<500 MJ mm ha(-1) h(-1) yr(-1)) in the Nordic countries. The erosivity density (erosivity normalised to annual precipitation amounts) was also the highest in Mediterranean regions which implies high risk for erosive events and floods

  16. Characterization of the ZAT1p zinc transporter from Arabidopsis thaliana in microbial model organisms and reconstituted proteoliposomes.

    Science.gov (United States)

    Bloss, Tanja; Clemens, Stephan; Nies, Dietrich H

    2002-03-01

    The ZAT1p zinc transporter from Arabidopsis thaliana (L.) Heynh. is a member of the cation diffusion facilitator (CDF) protein family. When heterologously expressed in Escherichia coli, ZAT1p bound zinc in a metal blot. Binding of zinc occurred mainly to the hydrophilic amino acid region from H182 to H232. A ZAT1p/ZAT1p*Delta(M1-I25) protein mixture was purified and reconstituted into proteoliposomes. Uptake of zinc into the proteoliposomes did not require a proton gradient across the liposomal membrane. ZAT1p did not transport cobalt, and transported cadmium at only 1% of the zinc transport rate. ZAT1p functioned as an uptake system for 65Zn2+ in two strains of the Gram-negative bacterium Ralstonia metallidurans, which were different in their content of zinc-efflux systems. The ZAT1 gene did not rescue increased zinc sensitivity of a Delta ZRC1single-mutant strain or of a Delta ZRC1 Delta COT1 double-mutant strain of Saccharomyces cerevisiae, but ZAT1 complemented this phenotype in a Delta SpZRC1 mutant strain of Schizosaccharomyces pombe.

  17. Effect of mass and charge transport speed and direction in porous anodes on microbial electrolysis cell performance

    NARCIS (Netherlands)

    Sleutels, T.H.J.A.; Hamelers, H.V.M.; Buisman, C.J.N.

    2011-01-01

    The use of porous electrodes like graphite felt as anode material has the potential of achieving high volumetric current densities. High volumetric current densities, however, may also lead to mass transport limitations within these porous materials. Therefore, in this study we investigated the mass

  18. Improved performance of porous bio-anodes in microbial electrolysis cells by enhancing mass and charge transport

    NARCIS (Netherlands)

    Sleutels, T.H.J.A.; Lodder, R.; Hamelers, H.V.M.; Buisman, C.J.N.

    2009-01-01

    To create an efficient MEC high current densities and high coulombic efficiencies are required. The aim of this study was to increase cur-rent densities and coulombic efficiencies by influencing mass and charge transport in porous electrodes by: (i) introduction of a forced flow through the anode to

  19. Coastal Erosion Control Methods

    Science.gov (United States)

    Greene, V.

    2016-12-01

    Coastal erosion is bad because the ecosystem there will be washed away and the animals could drown or be displaced and have to adapt to a new ecosystem that they are not prepared for. I'm interested in this problem because if there aren't beaches when I grow up I won't be able to do the things I would really like to do. I would like to be a marine biologist. Secondly, I don't want to see beach houses washed away. I would like to see people live in harmony with their environment. So, to study ways in which to preserve beaches I will make and use models that test different erosion controls. Two different ideas for erosion control I tested are using seaweed or a rock berm. I think the rock berm will work better than the model of seaweed because the seaweed is under water and the waves can carry the sand over the seaweed, and the rock berm will work better because the rocks will help break the waves up before they reach the shore and the waves can not carry the sand over the rocks that are above the water. To investigate this I got a container to use to model the Gulf of Mexico coastline. I performed several test runs using sand and water in the container to mimic the beach and waves from the Gulf of Mexico hitting the shoreline. I did three trials for the control (no erosion control), seaweed and a rock berm. Rock berms are a border of a raised area of rock. The model for seaweed that I used was plastic shopping bags cut into strips and glued to the bottom of my container to mimic seaweed. My results were that the control had the most erosion which ranged from 2.75 - 3 inches over 3 trials. The seaweed was a little better than the control but was very variable and ranged from 1.5 - 3 inches over 3 trials. The rock berm worked the best out of all at controlling erosion with erosion ranging from 1.5 - 2 inches. My hypothesis was correct because the rock berm did best to control erosion compared to the control which had no erosion control and the model with seaweed.

  20. Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

    Science.gov (United States)

    Rengers, Francis K.; Tucker, G.E.; Moody, J.A.; Ebel, Brian

    2016-01-01

    Erosion following a wildfire is much greater than background erosion in forests because of wildfire-induced changes to soil erodibility and water infiltration. While many previous studies have documented post-wildfire erosion with point and small plot-scale measurements, the spatial distribution of post-fire erosion patterns at the watershed scale remains largely unexplored. In this study lidar surveys were collected periodically in a small, first-order drainage basin over a period of 2 years following a wildfire. The study site was relatively steep with slopes ranging from 17° to > 30°. During the study period, several different types of rain storms occurred on the site including low-intensity frontal storms (2.4 mm h−1) and high-intensity convective thunderstorms (79 mm h−1). These storms were the dominant drivers of erosion. Erosion resulting from dry ravel and debris flows was notably absent at the site. Successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys. The results show an evolution in geomorphic response, such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre-fire site morphology. Hillslope and channel roughness increased over time, and the watershed armored as coarse cobbles and boulders were exposed. The erosional response was spatially nonuniform; shallow erosion from hillslopes (87% of the study area) contributed 3 times more sediment volume than erosion from convergent areas (13% of the study area). However, the total normalized erosion depth (volume/area) was highest in convergent areas. From a detailed understanding of the spatial locations of erosion, we made inferences regarding the processes driving erosion. It appears that hillslope erosion is controlled by rain splash (for detachment) and overland flow (for transport and quasi-channelized erosion), with the sites of highest erosion corresponding to locations

  1. Can control of soil erosion mitigate water pollution by sediments?

    Science.gov (United States)

    Rickson, R J

    2014-01-15

    The detrimental impact of sediment and associated pollutants on water quality is widely acknowledged, with many watercourses in the UK failing to meet the standard of 'good ecological status'. Catchment sediment budgets show that hill slope erosion processes can be significant sources of waterborne sediment, with rates of erosion likely to increase given predicted future weather patterns. However, linking on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion rates in the UK and the dynamic nature of the source-pathway-receptor continuum over space and time. Even so, soil erosion control measures are designed to reduce sediment production (source) and mobilisation/transport (pathway) on hill slopes, with consequent mitigation of pollution incidents in watercourses (receptors). The purpose of this paper is to review the scientific evidence of the effectiveness of erosion control measures used in the UK to reduce sediment loads of hill slope origin in watercourses. Although over 73 soil erosion mitigation measures have been identified from the literature, empirical data on erosion control effectiveness are limited. Baseline comparisons for the 18 measures where data do exist reveal erosion control effectiveness is highly variable over time and between study locations. Given the limitations of the evidence base in terms of geographical coverage and duration of monitoring, performance of the different measures cannot be extrapolated to other areas. This uncertainty in effectiveness has implications for implementing erosion/sediment risk reduction policies, where quantified targets are stipulated, as is the case in the EU Freshwater Fish and draft Soil Framework Directives. Also, demonstrating technical effectiveness of erosion control measures alone will not encourage uptake by land managers: quantifying the costs and benefits of adopting erosion mitigation is equally important, but these are uncertain and difficult to

  2. Considering a Threshold Energy in Reactive Transport Modeling of Microbially Mediated Redox Reactions in an Arsenic-Affected Aquifer

    Directory of Open Access Journals (Sweden)

    Marco Rotiroti

    2018-01-01

    Full Text Available The reductive dissolution of Fe-oxide driven by organic matter oxidation is the primary mechanism accepted for As mobilization in several alluvial aquifers. These processes are often mediated by microorganisms that require a minimum Gibbs energy available to conduct the reaction in order to sustain their life functions. Implementing this threshold energy in reactive transport modeling is rarely used in the existing literature. This work presents a 1D reactive transport modeling of As mobilization by the reductive dissolution of Fe-oxide and subsequent immobilization by co-precipitation in iron sulfides considering a threshold energy for the following terminal electron accepting processes: (a Fe-oxide reduction, (b sulfate reduction, and (c methanogenesis. The model is then extended by implementing a threshold energy on both reaction directions for the redox reaction pairs Fe(III reduction/Fe(II oxidation and methanogenesis/methane oxidation. The optimal threshold energy fitted in 4.50, 3.76, and 1.60 kJ/mol e− for sulfate reduction, Fe(III reduction/Fe(II oxidation, and methanogenesis/methane oxidation, respectively. The use of models implementing bidirectional threshold energy is needed when a redox reaction pair can be transported between domains with different redox potentials. This may often occur in 2D or 3D simulations.

  3. Erosive Lichen Planus.

    Science.gov (United States)

    Mauskar, Melissa

    2017-09-01

    Lichen planus is an inflammatory mucocutaneous condition with a myriad of clinical manifestations. There are 3 forms of lichen planus that effect the vulva: papulosquamous, hypertrophic, and erosive. Erosive lichen planus can progress to vulvar scaring, vaginal stenosis, and squamous cell carcinoma; these long-term sequelae cause sexual distress, depression, and decreased quality of life for patients. Diagnosis is often delayed because of patient embarrassment or clinician misdiagnosis. Early recognition and treatment is essential to decreasing the morbidity of this condition. Multimodal treatment, along with a multidisciplinary approach, will improve outcomes and further clinical advances in studying this condition. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Quantitative microbial risk assessment for spray irrigation of dairy manure based on an empirical fate and transport model

    Science.gov (United States)

    Burch, Tucker R; Spencer, Susan K.; Stokdyk, Joel; Kieke, Burney A; Larson, Rebecca A; Firnstahl, Aaron; Rule, Ana M; Borchardt, Mark A.

    2017-01-01

    BACKGROUND: Spray irrigation for land-applying livestock manure is increasing in the United States as farms become larger and economies of scale make manure irrigation affordable. Human health risks from exposure to zoonotic pathogens aerosolized during manure irrigation are not well understood. OBJECTIVES: We aimed to a) estimate human health risks due to aerosolized zoonotic pathogens downwind of spray-irrigated dairy manure; and b) determine which factors (e.g., distance, weather conditions) have the greatest influence on risk estimates. METHODS: We sampled downwind air concentrations of manure-borne fecal indicators and zoonotic pathogens during 21 full-scale dairy manure irri- gation events at three farms. We fit these data to hierarchical empirical models and used model outputs in a quantitative microbial risk assessment (QMRA) to estimate risk [probability of acute gastrointestinal illness (AGI)] for individuals exposed to spray-irrigated dairy manure containing Campylobacter jejuni, enterohemorrhagic Escherichia coli (EHEC), or Salmonella spp. RESULTS: Median risk estimates from Monte Carlo simulations ranged from 10−5 to 10−2 and decreased with distance from the source. Risk estimates for Salmonella or EHEC-related AGI were most sensitive to the assumed level of pathogen prevalence in dairy manure, while risk estimates for C. jejuni were not sensitive to any single variable. Airborne microbe concentrations were negatively associated with distance and positively associated with wind speed, both of which were retained in models as a significant predictor more often than relative humidity, solar irradiation, or temperature. CONCLUSIONS: Our model-based estimates suggest that reducing pathogen prevalence and concentration in source manure would reduce the risk of AGI from exposure to manure irrigation, and that increasing the distance from irrigated manure (i.e., setbacks) and limiting irrigation to times of low wind speed may also reduce risk.

  5. Transportation

    National Research Council Canada - National Science Library

    Adams, James; Carr, Ron; Chebl, Maroun; Coleman, Robert; Costantini, William; Cox, Robert; Dial, William; Jenkins, Robert; McGovern, James; Mueller, Peter

    2006-01-01

    ...., trains, ships, etc.) and maximizing intermodal efficiency. A healthy balance must be achieved between the flow of international commerce and security requirements regardless of transportation mode...

  6. Bentonite erosion - Laboratory studies

    International Nuclear Information System (INIS)

    Jansson, Mats

    2010-01-01

    Document available in extended abstract form only. Bentonite clay is proposed as buffer material in the KBS-3 concept of storing spent nuclear fuel. Since the clay is plastic it will protect the canisters containing the spent fuel from movements in the rock. Furthermore, the clay will expand when taking up water, become very compact and hence limit the transport of solutes to and from the canister to only diffusion. The chemical stability of the bentonite barrier is of vital importance. If much material would be lost the barrier will lose its functions. As a side effect, lots of colloids will be released which may facilitate radionuclide transport in case of a breach in the canister. There are scenarios where during an ice age fresh melt water may penetrate down to repository depths with relatively high flow rates and not mix with older waters of high salinity. Under such conditions bentonite colloids will be more stable and there is a possibility that the bentonite buffer would start to disperse and bentonite colloids be carried away by the passing water. This work is a part of a larger project called Bentonite Erosion, initiated and supported by SKB. In this work several minor experiments have been performed in order to investigate the influence of for instance di-valent cations, gravity, etc. on the dispersion behaviour of bentonite and/or montmorillonite. A bigger experiment where the real situation was simulated using an artificial fracture was conducted. Two Plexiglas slabs were placed on top of each other, separated by plastic spacers. Bentonite was placed in a container in contact with a fracture. The bentonite was water saturated before deionized water was pumped through the fracture. The evolution of the bentonite profile in the fracture was followed visually. The eluate was collected in five different slots at the outlet side and analyzed for colloid concentration employing Photon Correlation Spectroscopy (PCS) and a Single Particle Counter (SPC). Some

  7. Workshop on Copper Corrosion and Buffer Erosion. Stockholm 15-17 September 2010

    International Nuclear Information System (INIS)

    Robinson, Peter; Bath, Adrian

    2011-02-01

    The workshop was convened to inform and advise SSM about the coupled processes of buffer erosion and enhanced canister corrosion that have been proposed as a potentially detrimental scenario in the long-term evolution of the engineered barrier system of a deep geological repository. It was an extension of the deliberations of SSM's BRITE advisory group on EBS issues and on SKB's approaches to the issues in the forthcoming SR-Site safety case. The workshop was planned to assist and advise SSM in its preparations for review of SKB.s license application and SR-Site submission. The potential for buffer erosion due to a future influx of dilute groundwater that induces bentonite to behave as a sol has been indicated by experiments carried out for SKB. It is generally considered that the most likely source and timing of such groundwater conditions will be the glacial stage of the normal evolution of the repository system, i.e. many tens of thousands of years into the future at least. The workshop considered, however, that potential causes of buffer erosion in the early post-closure period should also be considered. The main significance of buffer erosion for a safety case is that it would potentially lead to higher rates of corrosion of the copper canister. There are various physicochemical mechanisms that could be implicated in enhanced corrosion but basically they would involve (a) the failure of a diffusion controlled constraint on corrodant transport to and product transport away from the copper surface, and (b) the viability of microbially-mediated reactions producing higher concentrations of corrodants at or near to the copper surface. The general issues relating to corrosion had already been the theme for a previous workshop in 2005 (see Report SKI 2006:11), the outcomes of which formed the background for this workshop. Additional background was provided by SKB's interim safety case, SR-Can, and the regulatory authorities. responses to preliminary consideration of

  8. Workshop on Copper Corrosion and Buffer Erosion. Stockholm 15-17 September 2010

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Peter (Quintessa (United Kingdom)); Bath, Adrian (Intellisci Ltd (United Kingdom))

    2011-02-15

    The workshop was convened to inform and advise SSM about the coupled processes of buffer erosion and enhanced canister corrosion that have been proposed as a potentially detrimental scenario in the long-term evolution of the engineered barrier system of a deep geological repository. It was an extension of the deliberations of SSM's BRITE advisory group on EBS issues and on SKB's approaches to the issues in the forthcoming SR-Site safety case. The workshop was planned to assist and advise SSM in its preparations for review of SKB.s license application and SR-Site submission. The potential for buffer erosion due to a future influx of dilute groundwater that induces bentonite to behave as a sol has been indicated by experiments carried out for SKB. It is generally considered that the most likely source and timing of such groundwater conditions will be the glacial stage of the normal evolution of the repository system, i.e. many tens of thousands of years into the future at least. The workshop considered, however, that potential causes of buffer erosion in the early post-closure period should also be considered. The main significance of buffer erosion for a safety case is that it would potentially lead to higher rates of corrosion of the copper canister. There are various physicochemical mechanisms that could be implicated in enhanced corrosion but basically they would involve (a) the failure of a diffusion controlled constraint on corrodant transport to and product transport away from the copper surface, and (b) the viability of microbially-mediated reactions producing higher concentrations of corrodants at or near to the copper surface. The general issues relating to corrosion had already been the theme for a previous workshop in 2005 (see Report SKI 2006:11), the outcomes of which formed the background for this workshop. Additional background was provided by SKB's interim safety case, SR-Can, and the regulatory authorities. responses to preliminary

  9. Mesh erosion after abdominal sacrocolpopexy.

    Science.gov (United States)

    Kohli, N; Walsh, P M; Roat, T W; Karram, M M

    1998-12-01

    To report our experience with erosion of permanent suture or mesh material after abdominal sacrocolpopexy. A retrospective chart review was performed to identify patients who underwent sacrocolpopexy by the same surgeon over 8 years. Demographic data, operative notes, hospital records, and office charts were reviewed after sacrocolpopexy. Patients with erosion of either suture or mesh were treated initially with conservative therapy followed by surgical intervention as required. Fifty-seven patients underwent sacrocolpopexy using synthetic mesh during the study period. The mean (range) postoperative follow-up was 19.9 (1.3-50) months. Seven patients (12%) had erosions after abdominal sacrocolpopexy with two suture erosions and five mesh erosions. Patients with suture erosion were asymptomatic compared with patients with mesh erosion, who presented with vaginal bleeding or discharge. The mean (+/-standard deviation) time to erosion was 14.0+/-7.7 (range 4-24) months. Both patients with suture erosion were treated conservatively with estrogen cream. All five patients with mesh erosion required transvaginal removal of the mesh. Mesh erosion can follow abdominal sacrocolpopexy over a long time, and usually presents as vaginal bleeding or discharge. Although patients with suture erosion can be managed successfully with conservative treatment, patients with mesh erosion require surgical intervention. Transvaginal removal of the mesh with vaginal advancement appears to be an effective treatment in patients failing conservative management.

  10. Erosion of buffer caused by groundwater leakages

    International Nuclear Information System (INIS)

    Autio, J.; Hanana, K.; Punkkinen, O.; Koskinen, K.; Olin, M.

    2010-01-01

    Document available in extended abstract form only. In the Finnish HLW disposal concept the most important properties of the bentonite clay being considered for these isolation purposes are its thermal behaviour, low hydraulic conductivity, diffusion limited transport, rheology, plasticity, sufficient swelling potential, and exchange capacity. All of these properties depend critically on bentonite density; therefore, any potential mass loss or redistribution events must be well characterized. One such event or process is the erosion of bentonite by flowing groundwater and the groundwater flowing in newly formed channels, in special. Mechanical erosion during the operational phase, due to high groundwater pressure gradients in open excavations, has been identified as a critical issue in TKS-2006 and SR-Can. This work addresses the mechanical erosion of bentonite by fluid shear. In order for buffer erosion to occur three processes must take place: detachment, entrainment, and transport. These processes are followed by the settling of the material and redistribution of buffer mass. Erosion begins with the detachment of a particle from surrounding material, which requires the application of shear forces greater than the attractive force between the particle and parent structure. Entrainment is the process by which the eroding medium lifts the detached particle into the flow. The most important aspect in entrainment is transfer of fluid's inertial forces via surface friction to particles' inertial forces, which, in turn, must overcome the frictional resistance between the particle and its surroundings. Factors influencing frictional resistance include gravity, particle mass, saturation degree of parent structure, composition of water present in parent structure, particle size, and surface roughness. Recent erosion tests, whereby water flow was directed over compacted bentonite blocks or through a system of bentonite pellets, have indicated that bentonite erodes

  11. Erosion of dust aggregates

    NARCIS (Netherlands)

    Seizinger, A.; Krijt, S.; Kley, W.

    2013-01-01

    Aims: The aim of this work is to gain a deeper insight into how much different aggregate types are affected by erosion. Especially, it is important to study the influence of the velocity of the impacting projectiles. We also want to provide models for dust growth in protoplanetary disks with simple

  12. Hydrology and soil erosion

    Science.gov (United States)

    Leonard J. Lane; Mary R. Kidwell

    2003-01-01

    We review research on surface water hydrology and soil erosion at the Santa Rita Experimental Range (SRER). Almost all of the research was associated with eight small experimental watersheds established from 1974 to 1975 and operated until the present. Analysis of climatic features of the SRER supports extending research findings from the SRER to broad areas of the...

  13. Erosion scenarios for Wellenberg

    International Nuclear Information System (INIS)

    Klemenz, W.

    1993-09-01

    The proposed Wellenberg site for a radioactive waste repository is located between Altzellen in the Engelberger valley and the Oberrickenbach valley, in a thick Valanginian marl series. The marl is generally overlaid with unconsolidated rocks but reaches to the surface in some places. In contrast to the situation in the Oberbauenstock region this marl complex is not protected by an overlying erosion resistant series and exhibits a marked relief. The question therefore arises with respect to the Wellenberg site, to what extent will the marl (i.e. the repository host rock formation) be removed by erosion processes during the 100,000 years interval under consideration and what overburden will remain at the end of this period. This report presents the results of an investigation of the longterm behaviour of the proposed site in respect of those processes of erosion and deposition which can lead to changes in the terrain surface and its location relative to the repository. A wide range of possible scenarios encompassing different developments of climatic conditions during the 100,000 year period of interest, was investigated. In addition to the continuation of the present climate and the occurrence of a new ice age on the scale of the Wuerm glaciation the consequences of altered climatic conditions on erosion removal of the repository overburden were considered. Within the 100,000 year period of interest none of the scenarios considered leads to the exposure of the repository. (author) figs., tabs, refs

  14. Dune erosion above revetments

    NARCIS (Netherlands)

    Van Thiel de Vries, J.S.M.

    2012-01-01

    In a situation with a narrow dune, the dune base can be protected with a revetment to reduce dune erosion during extreme events. To quantify the effects of a revetment on storm impact, the functionality of the numerical storm impact model XBeach (Roelvink et al., 2009) is extended to account for the

  15. Transportation

    International Nuclear Information System (INIS)

    Anon.

    1998-01-01

    Here is the decree of the thirtieth of July 1998 relative to road transportation, to trade and brokerage of wastes. It requires to firms which carry out a road transportation as well as to traders and to brokers of wastes to declare their operations to the prefect. The declaration has to be renewed every five years. (O.M.)

  16. Gaining insights into interrill soil erosion processes using rare earth element tracers

    Science.gov (United States)

    Increasing interest in developing process-based erosion models requires better understanding of the relationships among soil detachment, transportation, and deposition. The objectives are to 1) identify the limiting process between soil detachment and sediment transport for interrill erosion, 2) und...

  17. Instrumentation and methods evaluations for shallow land burial of waste materials: water erosion

    International Nuclear Information System (INIS)

    Hostetler, D.D.; Murphy, E.M.; Childs, S.W.

    1981-08-01

    The erosion of geologic materials by water at shallow-land hazardous waste disposal sites can compromise waste containment. Erosion of protective soil from these sites may enhance waste transport to the biosphere through water, air, and biologic pathways. The purpose of this study was to review current methods of evaluating soil erosion and to recommend methods for use at shallow-land, hazardous waste burial sites. The basic principles of erosion control are: minimize raindrop impact on the soil surface; minimize runoff quantity; minimize runoff velocity; and maximize the soil's resistance to erosion. Generally soil erosion can be controlled when these principles are successfully applied at waste disposal sites. However, these erosion control practices may jeopardize waste containment. Typical erosion control practices may enhance waste transport by increasing subsurface moisture movement and biologic uptake of hazardous wastes. A two part monitoring program is recommended for US Department of Energy (DOE) hazardous waste disposal sites. The monitoring programs and associated measurement methods are designed to provide baseline data permitting analysis and prediction of long term erosion hazards at disposal sites. These two monitoring programs are: (1) site reconnaissance and tracking; and (2) site instrumentation. Some potential waste transport problems arising from erosion control practices are identified. This report summarizes current literature regarding water erosion prediction and control

  18. How does slope form affect erosion in CATFLOW-SED?

    Science.gov (United States)

    Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

    2016-04-01

    Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

  19. Monitoring Riverbank Erosion in Mountain Catchments Using Terrestrial Laser Scanning

    Directory of Open Access Journals (Sweden)

    Laura Longoni

    2016-03-01

    Full Text Available Sediment yield is a key factor in river basins management due to the various and adverse consequences that erosion and sediment transport in rivers may have on the environment. Although various contributions can be found in the literature about sediment yield modeling and bank erosion monitoring, the link between weather conditions, river flow rate and bank erosion remains scarcely known. Thus, a basin scale assessment of sediment yield due to riverbank erosion is an objective hard to be reached. In order to enhance the current knowledge in this field, a monitoring method based on high resolution 3D model reconstruction of riverbanks, surveyed by multi-temporal terrestrial laser scanning, was applied to four banks in Val Tartano, Northern Italy. Six data acquisitions over one year were taken, with the aim to better understand the erosion processes and their triggering factors by means of more frequent observations compared to usual annual campaigns. The objective of the research is to address three key questions concerning bank erosion: “how” erosion happens, “when” during the year and “how much” sediment is eroded. The method proved to be effective and able to measure both eroded and deposited volume in the surveyed area. Finally an attempt to extrapolate basin scale volume for bank erosion is presented.

  20. Calibration and verification of numerical runoff and erosion model

    Directory of Open Access Journals (Sweden)

    Gabrić Ognjen

    2015-01-01

    Full Text Available Based on the field and laboratory measurements, and analogous with development of computational techniques, runoff and erosion models based on equations which describe the physics of the process are also developed. Based on the KINEROS2 model, this paper presents basic modelling principles of runoff and erosion processes based on the St. Venant's equations. Alternative equations for friction calculation, calculation of source and deposition elements and transport capacity are also shown. Numerical models based on original and alternative equations are calibrated and verified on laboratory scale model. According to the results, friction calculation based on the analytic solution of laminar flow must be included in all runoff and erosion models.

  1. A method to detect soil carbon degradation during soil erosion

    OpenAIRE

    F. Conen; M. Schaub; C. Alewell

    2009-01-01

    Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable c...

  2. Transportation

    National Research Council Canada - National Science Library

    Allshouse, Michael; Armstrong, Frederick Henry; Burns, Stephen; Courts, Michael; Denn, Douglas; Fortunato, Paul; Gettings, Daniel; Hansen, David; Hoffman, D. W; Jones, Robert

    2007-01-01

    .... The ability of the global transportation industry to rapidly move passengers and products from one corner of the globe to another continues to amaze even those wise to the dynamics of such operations...

  3. Development of an Integrated Water and Wind Erosion Model

    Science.gov (United States)

    Flanagan, D. C.; Ascough, J. C.; Wagner, L. E.; Geter, W. F.

    2006-12-01

    Prediction technologies for soil erosion by the forces of wind or water have largely been developed independently from one another, especially within the United States. Much of this has been due to the initial creation of equations and models which were empirical in nature (i.e., Universal Soil Loss Equation, Wind Erosion Equation) and based upon separate water erosion or wind erosion plot and field measurements. Additionally, institutional organizations in place typically divided research efforts and funding to unique wind or water erosion research and modeling projects. However, during the past 20 years computer technologies and erosion modeling have progressed to the point where it is now possible to merge physical process-based computer simulation models into an integrated water and wind erosion prediction system. In a physically- based model, many of the processes which must be simulated for wind and water erosion computations are the same, e.g., climate, water balance, runoff, plant growth, etc. Model components which specifically deal with the wind or water detachment, transport and deposition processes are those that must differ, as well as any necessary parameterization of input variables (e.g., adjusted soil erodibilities, critical shear stresses, etc.) for those components. This presentation describes current efforts towards development of a combined wind and water erosion model, based in part upon technologies present in the Water Erosion Prediction Project (WEPP) and the Wind Erosion Prediction System (WEPS) models. Initial efforts during the past two years have resulted in modular modeling components that allow for prediction of infiltration, surface runoff, and water erosion at a hillslope scale within an Object Modeling System. Additional components currently in development include wind detachment at a single field point, continuous water balance, and unified plant growth. Challenges in this project are many, and include adequate field

  4. Spatial bedrock erosion distribution in a natural gorge

    Science.gov (United States)

    Beer, A. R.; Turowski, J. M.; Kirchner, J. W.

    2015-12-01

    Quantitative analysis of morphological evolution both in terrestrial and planetary landscapes is of increasing interest in the geosciences. In mountainous regions, bedrock channel formation as a consequence of the interaction of uplift and erosion processes is fundamental for the entire surface evolution. Hence, the accurate description of bedrock channel development is important for landscape modelling. To verify existing concepts developed in the lab and to analyse how in situ channel erosion rates depend on the interrelations of discharge, sediment transport and topography, there is a need of highly resolved topographic field data. We analyse bedrock erosion over two years in a bedrock gorge downstream of the Gorner glacier above the town of Zermatt, Switzerland. At the study site, the Gornera stream cuts through a roche moutonnée in serpentine rock of 25m length, 5m width and 8m depth. We surveyed bedrock erosion rates using repeat terrestrial laser scanning (TLS) with an average point spacing of 5mm. Bedrock erosion rates in direction of the individual surface normals were studied directly on the scanned point clouds applying the M3C2 algorithm (Lague et al., 2013, ISPRS). The surveyed erosion patterns were compared to a simple stream erosivity visualisation obtained from painted bedrock sections at the study location. Spatially distributed erosion rates on bedrock surfaces based on millions of scan points allow deduction of millimeter-scale mean annual values of lateral erosion, incision and downstream erosion on protruding streambed surfaces. The erosion rate on a specific surface point is shown to depend on the position of this surface point in the channel's cross section, its height above the streambed and its spatial orientation to the streamflow. Abrasion by impacting bedload was likely the spatially dominant erosion process, as confirmed by the observed patterns along the painted bedrock sections. However, a single plucking event accounted for the half

  5. Erosion control works and the intensity of soil erosion in the upper part of the river Toplica drainage basin

    International Nuclear Information System (INIS)

    Kostadinov, S; Dragovic, N; Zlatic, M; Todosijevic, M

    2008-01-01

    Aiming at the protection of the future storage 'Selova' against erosion and sediment, and also to protect the settlements and roads in the drainage basin against torrential floods, erosion control works in the upper part of the river Toplica basin, upstream of the storage 'Selova', started in 1947. The works included building-technical works (check dams) and biological works (afforestation and grassing of bare lands and other erosion risk areas). Within the period 1947-2006, the following erosion control works were executed: afforestation of bare lands on the slopes 2,257.00 ha, grassing of bare lands 1,520.00 ha, and altogether 54 dams were constructed in the river Toplica tributaries. This caused the decrease of sediment transport in the main flow of the river Toplica. This paper, based on the field research conducted in two time periods: 1988 and in the period 2004-2007, presents the state of erosion in the basin before erosion control works; type and scope of erosion control works and their effect on the intensity of erosion in the river Toplica basin upstream of the future storage 'Selova'.

  6. Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion

    Directory of Open Access Journals (Sweden)

    I. P. Semiletov

    2011-09-01

    Full Text Available The Lena River integrates biogeochemical signals from its vast drainage basin, and the integrated signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon (OC into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered to be quasi-steady-state processes. An increase in Lena discharge exerts opposite effects on total organic (TOC and total inorganic (TCO2 carbon: TOC concentration increases, while TCO2 concentration decreases. Significant inter-annual variability in mean values of TCO2, TOC, and their sum (total carbon, TC has been found. This variability is determined by changes in land hydrology which cause differences in the Lena River discharge. There is a negative correlation in the Lena River between TC in September and its mean discharge in August; a time shift of about one month is required for water to travel from Yakutsk to the Laptev Sea. Total carbon entering the sea with the Lena discharge is estimated to be almost 10 Tg C yr−1. The annual Lena River discharge of particulate organic carbon (POC can be as high as 0.38 Tg (moderate to high estimate. If we instead accept Lisytsin's (1994 statement that 85–95 % of total particulate matter (PM (and POC precipitates on the marginal "filter", then only about 0.03–0.04 Tg of Lena River POC reaches the Laptev Sea. The Lena's POC export would then be two orders of magnitude less than the annual input of eroded terrestrial carbon onto the shelf of the Laptev and East Siberian seas, which is estimated to be about 4 Tg. Observations support the hypothesis of a dominant role for coastal erosion (Semiletov, 1999a, b in East Siberian Arctic Shelf (ESAS sedimentation and the dynamics of the carbon/carbonate system. The Lena River is characterized by relatively high concentrations of the primary greenhouse gases, dissolved carbon dioxide (CO2 and methane (CH

  7. Erosion prediction for alpine slopes: a symbiosis of remote sensing and a physical based erosion model

    Science.gov (United States)

    Kaiser, Andreas; Neugirg, Fabian; Haas, Florian; Schindewolf, Marcus; Schmidt, Jürgen

    2014-05-01

    As rainfall simulations represent an established tool for quantifying soil detachment on cultivated area in lowlands and low mountain ranges, they are rarely used on steep slopes high mountain ranges. Still this terrain represents productive sediment sources of high morphodynamic. A quantitative differentiation between gravitationally and fluvially relocated material reveals a major challenge in understanding erosion on steep slopes: does solifluction as a result of melting in spring or heavy convective rainstorms during summer cause the essential erosion processes? This paper aims to answer this question by separating gravitational mass movement (solifluction, landslides, mudflow and needle ice) and runoff-induced detachment. First simulated rainstorm experiments are used to assess the sediment production on bare soil on a strongly inclined plot (1 m², 42°) in the northern limestone Alps. Throughout precipitation experiments runoff and related suspended sediments were quantified. In order to enlarge slope length virtually to around 20 m a runoff feeding device is additionally implemented. Soil physical parameters were derived from on-site sampling. The generated data is introduced to the physically based and catchment-scaled erosion model EROSION 3D to upscale plot size to small watershed conditions. Thus infiltration, runoff, detachment, transport and finally deposition can be predicted for single rainstorm events and storm sequences. Secondly, in order to separate gravitational mass movements and water erosion, a LiDAR and structure-from-motion based monitoring approach is carried out to produce high-resolution digital elevation models. A time series analysis of detachment and deposition from different points in time is implemented. Absolute volume losses are then compared to sediment losses calculated by the erosion model as the latter only generates data that is connected to water induced hillside erosion. This methodology will be applied in other watersheds

  8. Rainfall erosivity map for Ghana

    International Nuclear Information System (INIS)

    Oduro Afriyie, K.

    1995-10-01

    Monthly rainfall data, spanning over a period of more than thirty years, were used to compute rainfall erosivity indices for various stations in Ghana, using the Fournier index, c, defined as p 2 /P, where p is the rainfall amount in the wettest month and P is the annual rainfall amount. Values of the rainfall erosivity indices ranged from 24.5 mm at Sunyani in the mid-portion of Ghana to 180.9 mm at Axim in the south western coastal portion. The indices were used to construct a rainfall erosivity map for the country. The map revealed that Ghana may be broadly divided into five major erosion risk zones. The middle sector of Ghana is generally in the low erosion risk zone; the northern sector is in the moderate to severe erosion risk zone, while the coastal sector is in the severe to extreme severe erosion risk zone. (author). 11 refs, 1 fig., 1 tab

  9. Development and evaluation of the microbial fate and transport module for the Agricultural Policy/Environmental eXtender (APEX) model

    Science.gov (United States)

    Microbial contamination of waters in agricultural watershed is the critical public health issue. The watershed-scale model has been proven to be one of the candidate tools for predicting microbial water quality and evaluating management practices. The Agricultural Policy/Environmental eXtender (APEX...

  10. Erosion-corrosion synergistics in the low erosion regime

    International Nuclear Information System (INIS)

    Corey, R.G.; Sethi, V.K.

    1986-01-01

    Many engineering alloys display good high temperature corrosion resistance. However, when they are used in corrosive environments where they are subjected to erosion also, the corrosion resistance has been adversely affected. The phenomenon known as erosion-corrosion is complex and requires detailed investigation of how the erosion and corrosion kinetics interact and compete. At the Kentucky Center for Energy Research Laboratory, an erosion-corrosion tester was used to perform erosion-oxidation tests on 2 1/4 Cr-1 Mo steel at 500-600 0 C using alumina abrasive at low velocities. The erosion-oxidation rate data and morphology of exposed surfaces are consistent with oxide chipping and fracturing being the mode of material loss

  11. Coupling a continuous watershed-scale microbial fate and transport model with a stochastic dose-response model to estimate risk of illness in an urban watershed.

    Science.gov (United States)

    Liao, Hehuan; Krometis, Leigh-Anne H; Kline, Karen

    2016-05-01

    Within the United States, elevated levels of fecal indicator bacteria (FIB) remain the leading cause of surface water-quality impairments requiring formal remediation plans under the federal Clean Water Act's Total Maximum Daily Load (TMDL) program. The sufficiency of compliance with numerical FIB criteria as the targeted endpoint of TMDL remediation plans may be questionable given poor correlations between FIB and pathogenic microorganisms and varying degrees of risk associated with exposure to different fecal pollution sources (e.g. human vs animal). The present study linked a watershed-scale FIB fate and transport model with a dose-response model to continuously predict human health risks via quantitative microbial risk assessment (QMRA), for comparison to regulatory benchmarks. This process permitted comparison of risks associated with different fecal pollution sources in an impaired urban watershed in order to identify remediation priorities. Results indicate that total human illness risks were consistently higher than the regulatory benchmark of 36 illnesses/1000 people for the study watershed, even when the predicted FIB levels were in compliance with the Escherichia coli geometric mean standard of 126CFU/100mL. Sanitary sewer overflows were associated with the greatest risk of illness. This is of particular concern, given increasing indications that sewer leakage is ubiquitous in urban areas, yet not typically fully accounted for during TMDL development. Uncertainty analysis suggested the accuracy of risk estimates would be improved by more detailed knowledge of site-specific pathogen presence and densities. While previous applications of the QMRA process to impaired waterways have mostly focused on single storm events or hypothetical situations, the continuous modeling framework presented in this study could be integrated into long-term water quality management planning, especially the United States' TMDL program, providing greater clarity to watershed

  12. Wind erosion on Deliblato (the largest European continental sandy terrain) studied using 210Pbex and 137Cs measurements

    International Nuclear Information System (INIS)

    Krmar, M.; Hansman, J.; Todorovic, N.; Mihailovic, A.; Vucinic-Vasic, M.; Savic, R.

    2015-01-01

    The objective of this paper is to estimate the difference in wind erosion between two extreme situations: sandy soil permanently covered by grass and the nearby frequently ploughed area highly susceptible to wind erosion. The spatial pattern of soil erosion rate was investigated using 137 Cs and 210 Pb ex tracing technique. The spatial pattern of erosion rate obtained within the studied area reveal influence of topography as well as direction of prevailing winds on mobilization and transport of the soil particles. (author)

  13. A terminological matter: paragenesis, antigravitative erosion or antigravitational erosion ?

    Directory of Open Access Journals (Sweden)

    Pasini G.

    2009-07-01

    Full Text Available In the speleological literature three terms are utilized to designate the “ascending erosion”: paragenesis (= paragénésis, coined in1968, antigravitative erosion (= erosione antigravitativa, coined in 1966 and antigravitational erosion (wrong English translation ofthe Italian term erosione antigravitativa, utilized later on. The term paragenesis should be abandoned because of the priority of theterm erosione antigravitativa - on the ground of the “law of priority” – and because of its ambiguous etimology. On the other hand,the term antigravitational erosion should be forsaken in favour of the term antigravitative erosion, given the meaning that the termsgravitation and gravity have in Physics. Therefore, to designate the phenomenon of the “ascending erosion” there would be nothingleft but the term antigravitative erosion.The antigravitative erosion process and its recognizability are illustrated.Examples of caves with evident antigravitative erosion phenomena, developed in different karstifiable rocks and in several partsof the world, are given.It is recalled that the antigravitative erosion is a phenomenon well-known since 1942 and widely proven and supported, and that it isrelatively easy – in many cases - to recognize the antigravitative origin of karstic passages.It is stressed that the antigravitative erosion is an important phenomenon, exclusive of the karstic caves and unique in nature.

  14. Anthropogenic Increase Of Soil Erosion In The Gangetic Plain Revealed By Geochemical Budget Of Erosion

    Science.gov (United States)

    Galy, V.; France-Lanord, C.; Galy, A.; Gaillardet, J.

    2007-12-01

    Tectonic and climatic factors are the key natural variables controlling the erosion through complex interactions. Nonetheless, over the last few hundred years, human activity also exerts a dominant control in response to extensive land use. The geochemical budget of erosion allows the balance between the different erosion processes to be quantified. The chemical composition of river sediment results from the chemical composition of the source rock modified by (1) weathering reactions occurring during erosion and (2) physical segregation during transport. If erosion is at steady state, the difference between the chemical composition of source rocks and that of river sediments must therefore be counterbalanced by the dissolved flux. However, climatic variations or anthropic impact can induce changes in the erosion distribution in a given basin resulting in non steady state erosion. Using a mass balance approach, the comparison of detailed geochemical data on river sediments with the current flux of dissolved elements allows the steady state hypothesis to be tested. In this study, we present a geochemical budget of weathering for the Ganga basin, one of the most densely populated basin in the world, based on detailed sampling of Himalayan rivers and of the Ganga in the delta. Sampling includes depth profile in the river, to assess the variability generated by transport processes. Himalayan river sediments are described by the dilution of an aluminous component (micas + clays + feldspars) by quartz. Ganga sediments on the other hand correspond to the mixing of bedload, similar to coarse Himalayan sediments, with an aluminous component highly depleted in alkaline elements. Compared with the dissolved flux, the depletion of alkaline elements in Ganga sediments shows that the alkaline weathering budget is imbalanced. This imbalance results from an overabundance of fine soil material in the Ganga sediment relative to other less weathered material directly derived from

  15. Transportation

    Science.gov (United States)

    2007-01-01

    Faculty ii INDUSTRY TRAVEL Domestic Assistant Deputy Under Secretary of Defense (Transportation Policy), Washington, DC Department of...developed between the railroad and trucking industries. Railroads: Today’s seven Class I freight railroad systems move 42% of the nation’s intercity ...has been successfully employed in London to reduce congestion and observed by this industry study during its travels . It is currently being

  16. Erosion in extruder flow

    Science.gov (United States)

    Kaufman, Miron; Fodor, Petru S.

    A detailed analysis of the fluid flow in Tadmor's unwound channel model of the single screw extruder is performed by combining numerical and analytical methods. Using the analytical solution for the longitudinal velocity field (in the limit of zero Reynolds number) allows us to devote all the computational resources solely for a detailed numerical solution of the transversal velocity field. This high resolution 3D model of the fluid flow in a single-screw extruder allows us to identify the position and extent of Moffatt eddies that impede mixing. We further consider the erosion of particles (e.g. carbon-black agglomerates) advected by the polymeric flow. We assume a particle to be made of primary fragments bound together. In the erosion process a primary fragment breaks out of a given particle. Particles are advected by the laminar flow and they disperse because of the shear stresses imparted by the fluid. The time evolution of the numbers of particles of different sizes is described by the Bateman coupled differential equations used to model radioactivity. Using the particle size distribution we compute an entropic fragmentation index which varies from 0 for a monodisperse system to 1 for an extreme poly-disperse system.

  17. ESTIMATION OF THE WANDA GLACIER (SOUTH SHETLANDS) SEDIMENT EROSION RATE USING NUMERICAL MODELLING

    OpenAIRE

    Kátia Kellem Rosa; Rosemary Vieira; Jefferson Cardia Simões

    2013-01-01

    Glacial sediment yield results from glacial erosion and is influenced by several factors including glacial retreat rate, ice flow velocity and thermal regime. This paper estimates the contemporary subglacial erosion rate and sediment yield of Wanda Glacier (King George Island, South Shetlands). This work also examines basal sediment evacuation mechanisms by runoff and glacial erosion processes during the subglacial transport. This is small temperate glacier that has seen retreating for the l...

  18. Modeling Megacusps and Dune Erosion

    Science.gov (United States)

    Orzech, M.; Reniers, A. J.; Thornton, E. B.

    2009-12-01

    Megacusps are large, concave, erosional features of beaches, of O(200m) alongshore wavelength, which sometimes occur when rip channel bathymetry is present. It is commonly hypothesized that erosion of the dune and back beach will be greater at the alongshore locations of the megacusp embayments, principally because the beach width is narrower there and larger waves can more easily reach the dune toe (e.g., Short, J. Geol., 1979, Thornton, et al., Mar. Geol., 2007). At present, available field data in southern Monterey Bay provide some support for this hypothesis, but not enough to fully confirm or refute it. This analysis utilizes XBeach, a 2DH nearshore sediment transport model, to test the above hypothesis under a range of wave conditions over several idealized rip-megacusp bathymetries backed by dunes. Model results suggest that while specific wave conditions may result in erosional hot spots at megacusp embayments, other factors such as tides, wave direction, and surf zone bathymetry can often play an equal or stronger role.

  19. Rill erosion rates in burned forests

    Science.gov (United States)

    Joseph W. Wagenbrenner; Peter R. Robichaud

    2011-01-01

    Introduction Wildfires often produce large increases in runoff and erosion rates (e.g., Moody and Martin, 2009), and land managers need to predict the frequency and magnitude of postfire erosion to determine the needs for hazard response and possible erosion mitigation to reduce the impacts of increased erosion on public safety and valued resources. The Water Erosion...

  20. A "1"3"7Cs erosion model with moving boundary

    International Nuclear Information System (INIS)

    Yin, Chuan; Ji, Hongbing

    2015-01-01

    A novel quantitative model of the relationship between diffused concentration changes and erosion rates using assessment of soil losses was developed. It derived from the analysis of surface soil "1"3"7Cs flux variation under persistent erosion effect and based on the principle of geochemistry kinetics moving boundary. The new moving boundary model improves the basic simplified transport model (Zhang et al., 2008), and mainly applies to uniform rainfall areas which show a long-time soil erosion. The simulation results for this kind of erosion show under a long-time soil erosion, the influence of "1"3"7Cs concentration will decrease exponentially with increasing depth. Using the new model fit to the measured "1"3"7Cs depth distribution data in Zunyi site, Guizhou Province, China which has typical uniform rainfall provided a good fit with R"2 = 0.92. To compare the soil erosion rates calculated by the simple transport model and the new model, we take the Kaixian reference profile as example. The soil losses estimated by the previous simplified transport model are greater than those estimated by the new moving boundary model, which is consistent with our expectations. - Highlights: • The diffused moving boundary principle analysing "1"3"7Cs flux variation. • The new erosion model applies to uniform rainfall areas. • The erosion effect on "1"3"7Cs will decrease exponentially with increasing depth. • The new model provides two methods of calculating erosion rate.

  1. Coupling a continuous watershed-scale microbial fate and transport model with a stochastic dose-response model to estimate risk of illness in an urban watershed

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Hehuan, E-mail: hehuan86@vt.edu [Department of Biological Systems Engineering, Virginia Tech, 155 Ag Quad Lane, Blacksburg, VA 24061 (United States); Krometis, Leigh-Anne H. [Department of Biological Systems Engineering, Virginia Tech, 155 Ag Quad Lane, Blacksburg, VA 24061 (United States); Kline, Karen [Department of Biological Systems Engineering, Virginia Tech, 155 Ag Quad Lane, Blacksburg, VA 24061 (United States); Center for Watershed Studies, Virginia Tech, 155 Ag Quad Lane, Blacksburg, VA 24061 (United States)

    2016-05-01

    Within the United States, elevated levels of fecal indicator bacteria (FIB) remain the leading cause of surface water-quality impairments requiring formal remediation plans under the federal Clean Water Act's Total Maximum Daily Load (TMDL) program. The sufficiency of compliance with numerical FIB criteria as the targeted endpoint of TMDL remediation plans may be questionable given poor correlations between FIB and pathogenic microorganisms and varying degrees of risk associated with exposure to different fecal pollution sources (e.g. human vs animal). The present study linked a watershed-scale FIB fate and transport model with a dose-response model to continuously predict human health risks via quantitative microbial risk assessment (QMRA), for comparison to regulatory benchmarks. This process permitted comparison of risks associated with different fecal pollution sources in an impaired urban watershed in order to identify remediation priorities. Results indicate that total human illness risks were consistently higher than the regulatory benchmark of 36 illnesses/1000 people for the study watershed, even when the predicted FIB levels were in compliance with the Escherichia coli geometric mean standard of 126 CFU/100 mL. Sanitary sewer overflows were associated with the greatest risk of illness. This is of particular concern, given increasing indications that sewer leakage is ubiquitous in urban areas, yet not typically fully accounted for during TMDL development. Uncertainty analysis suggested the accuracy of risk estimates would be improved by more detailed knowledge of site-specific pathogen presence and densities. While previous applications of the QMRA process to impaired waterways have mostly focused on single storm events or hypothetical situations, the continuous modeling framework presented in this study could be integrated into long-term water quality management planning, especially the United States' TMDL program, providing greater clarity to

  2. Coupling a continuous watershed-scale microbial fate and transport model with a stochastic dose-response model to estimate risk of illness in an urban watershed

    International Nuclear Information System (INIS)

    Liao, Hehuan; Krometis, Leigh-Anne H.; Kline, Karen

    2016-01-01

    Within the United States, elevated levels of fecal indicator bacteria (FIB) remain the leading cause of surface water-quality impairments requiring formal remediation plans under the federal Clean Water Act's Total Maximum Daily Load (TMDL) program. The sufficiency of compliance with numerical FIB criteria as the targeted endpoint of TMDL remediation plans may be questionable given poor correlations between FIB and pathogenic microorganisms and varying degrees of risk associated with exposure to different fecal pollution sources (e.g. human vs animal). The present study linked a watershed-scale FIB fate and transport model with a dose-response model to continuously predict human health risks via quantitative microbial risk assessment (QMRA), for comparison to regulatory benchmarks. This process permitted comparison of risks associated with different fecal pollution sources in an impaired urban watershed in order to identify remediation priorities. Results indicate that total human illness risks were consistently higher than the regulatory benchmark of 36 illnesses/1000 people for the study watershed, even when the predicted FIB levels were in compliance with the Escherichia coli geometric mean standard of 126 CFU/100 mL. Sanitary sewer overflows were associated with the greatest risk of illness. This is of particular concern, given increasing indications that sewer leakage is ubiquitous in urban areas, yet not typically fully accounted for during TMDL development. Uncertainty analysis suggested the accuracy of risk estimates would be improved by more detailed knowledge of site-specific pathogen presence and densities. While previous applications of the QMRA process to impaired waterways have mostly focused on single storm events or hypothetical situations, the continuous modeling framework presented in this study could be integrated into long-term water quality management planning, especially the United States' TMDL program, providing greater clarity to watershed

  3. The erosive potential of lollipops

    NARCIS (Netherlands)

    Brand, H.S.; Gambon, D.L.; Paap, A.; Bulthuis, M.S.; Veerman, E.C.I.; Nieuw Amerongen, A.V.

    2009-01-01

    Aim: To determine the erosive potential of several commercially available lollipops and the protective effect of saliva. Methods: The erosive potential of lollipops was determined in vitro by measuring the pH and neutralisable acidity. Subsequently, 10 healthy volunteers tested different types of

  4. Wind erosion processes and control

    Science.gov (United States)

    Wind erosion continues to threaten the sustainability of our nations' soil, air, and water resources. To effectively apply conservation systems to prevent wind driven soil loss, an understanding of the fundamental processes of wind erosion is necessary so that land managers can better recognize the ...

  5. Erosion--corrosion

    International Nuclear Information System (INIS)

    Vyas, B.

    1978-01-01

    The deterioration of materials by corrosion or erosion by itself presents a formidable problem and for this reason investigators have studied these two phenomena independently. In fact, there are very few systematic studies on E-C and the majority of references mention it only in passing. In most real systems, however, the two destructive processes take place simultaneously, hence the purpose of this review is to present the various interactions between the chemical and mechanical agents leading to accelerated degradation of the material. The papers cited in the review are those that lead to a better understanding of the process involved in the accelerated rate of material loss under E-C conditions

  6. Wind erosion in the Sahelian zone of Niger : processes, models, and control techniques

    NARCIS (Netherlands)

    Sterk, G.

    1997-01-01

    In the Sahelian zone of Niger, severe wind erosion occurs mainly in the first half of the rainy season (May - July), when violent winds preceding thunderstorms result in intense sediment transport. Quantification of this wind erosion is difficult due to a high degree of temporal and spatial

  7. Using REE tracers to measure sheet erosion changing to rill erosion

    International Nuclear Information System (INIS)

    Liu Puling; Xue Yazhou; Song Wei; Wang Mingyi; Ju Tongjun

    2004-01-01

    Rare Earth Elements (REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different rare earth elements of different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amounts increase with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4-5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amounts. The new REE tracer method should be useful to future studying of erosion processes on slope lands. (authors)

  8. Modeling soil erosion in a watershed

    OpenAIRE

    Lanuza, R.

    1999-01-01

    Most erosion models have been developed based on a plot scale and have limited application to a watershed due to the differences in aerial scale. In order to address this limitation, a GIS-assisted methodology for modeling soil erosion was developed using PCRaster to predict the rate of soil erosion at watershed level; identify the location of erosion prone areas; and analyze the impact of landuse changes on soil erosion. The general methodology of desktop modeling or soil erosion at watershe...

  9. understanding the mechanism of soil erosion from outdoor model

    African Journals Online (AJOL)

    Dr Obe

    to agricultural and transportation progress. This phenomenon arises from the lack of proper control of storm water on the highway fight of way and tributary slopes. It is therefore a prerequisite in erosion control designs to secure accurate hydrological and soil data for the affected regions. The extent of the degradation of.

  10. Modelling Soil Erosion in the Densu River Basin Using RUSLE and GIS Tools.

    Science.gov (United States)

    Ashiagbori, G; Forkuo, E K; Laari, P; Aabeyir, R

    2014-07-01

    Soil erosion involves detachment and transport of soil particles from top soil layers, degrading soil quality and reducing the productivity of affected lands. Soil eroded from the upland catchment causes depletion of fertile agricultural land and the resulting sediment deposited at the river networks creates river morphological change and reservoir sedimentation problems. However, land managers and policy makers are more interested in the spatial distribution of soil erosion risk than in absolute values of soil erosion loss. The aim of this paper is to model the spatial distribution of soil erosion in Densu River Basin of Ghana using RUSLE and GIS tools and to use the model to explore the relationship between erosion susceptibility, slope and land use/land cover (LULC) in the Basin. The rainfall map, digital elevation model, soil type map, and land cover map, were input data in the soil erosion model developed. This model was then categorized into four different erosion risk classes. The developed soil erosion map was then overlaid with the slope and LULC maps of the study area to explore their effects on erosion susceptibility of the soil in the Densu River Basin. The Model, predicted 88% of the basin as low erosion risk and 6% as moderate erosion risk, 3% as high erosion risk and 3% as severe risk. The high and severe erosion areas were distributed mainly within the areas of high slope gradient and also sections of the moderate forest LULC class. Also, the areas within the moderate forest LULC class found to have high erosion risk, had an intersecting high erodibility soil group.

  11. Microbial biosensors

    International Nuclear Information System (INIS)

    Le Yu; Chen, Wilfred; Mulchandani, Ashok

    2006-01-01

    A microbial biosensor is an analytical device that couples microorganisms with a transducer to enable rapid, accurate and sensitive detection of target analytes in fields as diverse as medicine, environmental monitoring, defense, food processing and safety. The earlier microbial biosensors used the respiratory and metabolic functions of the microorganisms to detect a substance that is either a substrate or an inhibitor of these processes. Recently, genetically engineered microorganisms based on fusing of the lux, gfp or lacZ gene reporters to an inducible gene promoter have been widely applied to assay toxicity and bioavailability. This paper reviews the recent trends in the development and application of microbial biosensors. Current advances and prospective future direction in developing microbial biosensor have also been discussed

  12. Gastric Mucosal Erosions - Radiologic evaluation -

    International Nuclear Information System (INIS)

    Kim, Seung Hyup

    1985-01-01

    70 cases of gastric mucosal erosions were diagnosed by double contrast upper gastrointestinal examinations and endoscopic findings. Analyzing the radiologic findings of these 70 cases of gastric mucosal erosions, the following results were obtained. 1. Among the total 70 cases, 65 cases were typical varioliform erosions showing central depressions and surrounding mucosal elevations. Remaining 5 cases were erosions of acute phase having multiple irregular depressions without surrounding elevations. 2. The gastric antrum was involved alone or in part in all cases. Duodenal bulb was involved with gastric antrum in 4 cases. 3. The majority of the cases had multiple erosions. There were only 2 cases of single erosion. 4. In 65 cases of varioliform erosions; 1) The diameter of the surrounding elevations varied from 3 to 20 mm with the majority (47 cases) between 6 and 10 mm. 2) In general, the surrounding elevations with sharp margin on double contrast films were also clearly demonstrated on compression films but those with faint margin were not. 3) The size of the central barium collections varied from pinpoint to 10 mm with the majority under 5 mm. The shape of the central barium collections in majority of the cases were round with a few cases of linear, triangular or star-shape. 5. In 5 cases of acute phase erosions; 1) All the 5 cases were females. 2) On double contrast radiography, all the cases showed multiple irregular depressed lesions without surrounding elevations. 3) 1 case had the history of hematemesis. 4) In 1 case, there was marked radiological improvement on follow-up study of 2 months interval. 6. In 23 cases, there were coexistent diseases with gastric mucosal erosions. These were 13 cases of duodenal bulb ulcers,7 cases of benign gastric ulcers and 3 others

  13. Current status of mechanical erosion studies of bentonite buffer

    International Nuclear Information System (INIS)

    Sane, P.; Olin, M.; Koskinen, K.

    2013-08-01

    The performance of the bentonite buffer in KBS-3-type nuclear waste repository concept relies to a great extent on the buffer surrounding the canister having sufficient dry density. Loss of buffer material caused by erosion remains as the most significant process reducing the density of the buffer. The mechanical erosion, or pre-saturation erosion, is the process where flowing groundwater transports buffer material away from the deposition hole towards the deposition tunnel. This process reduces the overall buffer density and potentially creates localized regions of low density. In the worst case the process is assumed to last as long as the free volume between the pellets in the pellets filled regions is filled with groundwater. With fixed environmental and material parameters a set of experiments was performed, testing the erosive properties of different buffer and backfill materials (MX-80 and Friedland Clay) in different groundwater conditions. The method used was a pinhole erosion test using two sizescales; 100 mm and 400 mm of cell length. The purpose of the pinhole tests was to test the scenario where piping channel is formed in the buffer and water flows through a single channel. The erosion data was produced with two methods, firstly the time-related erosion rates measured in-situ during the measurement and secondly the overall mass loss in the sample cell measured after dismantling of the test. It was observed that erosion in piping channels decreases rapidly (∼24 h) and irreversibly to a level that is an order of magnitude lower than the peak values. (orig.)

  14. Buffer erosion in dilute groundwater

    International Nuclear Information System (INIS)

    Schatz, T.; Kanerva, N.; Martikainen, J.; Sane, P.; Olin, M.; Seppaelae, A.; Koskinen, K.

    2013-08-01

    One scenario of interest for repository safety assessment involves the loss of bentonite buffer material in contact with dilute groundwater flowing through a transmissive fracture interface. In order to examine the extrusion/erosion behavior of bentonite buffer material under such circumstances, a series of experiments were performed in a flow-through, 1 mm aperture, artificial fracture system. These experiments covered a range of solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity conditions. No erosion was observed for sodium montmorillonite against solution compositions from 0.5 g/L to 10 g/L NaCl. No erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Erosion was observed for both sodium montmorillonite and 50/50 calcium/sodium montmorillonite against solution compositions ≤ 0.25 g/L NaCl. The calculated erosion rates for the tests with the highest levels of measured erosion, i.e., the tests run under the most dilute conditions (ionic strength (IS) < ∼1 mM), were well-correlated to flow velocity, whereas the calculated erosion rates for the tests with lower levels of measured erosion, i.e., the tests run under somewhat less dilute conditions (∼1 mM < IS < ∼4 mM), were not similarly correlated indicating that material and solution composition can significantly affect erosion rates. In every experiment, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture effectively forming an extended diffusive barrier around the intersecting fracture/buffer interface. Additionally, a model which was developed previously to predict the rate of erosion of bentonite buffer material in low ionic strength water in rock fracture environments was applied to three different cases: sodium montmorillonite expansion in a vertical tube, a

  15. Controlling Salmonella infection in weanling pigs through water delivery of direct-fed microbials or organic acids: Part II. Effects on intestinal histology and active nutrient transport

    Science.gov (United States)

    The objective of this study was to evaluate the effects of water-delivered direct-fed microbials (DFM) or organic acids on intestinal morphology and active nutrient absorption in weanling pigs following deliberate Salmonella infection. Pigs (n = 88) were weaned at 19 ± 2 d of age and assigned to one...

  16. Spatial Interpolation of Rainfall Erosivity Using Artificial Neural Networks for Southern Brazil Conditions

    Directory of Open Access Journals (Sweden)

    Michel Castro Moreira

    Full Text Available ABSTRACT Water erosion is the process of disaggregation and transport of sediments, and rainfall erosivity is a numerical value that expresses the erosive capacity of rain. The scarcity of information on rainfall erosivity makes it difficult or impossible to use to estimate losses occasioned by the erosive process. The objective of this study was to develop Artificial Neural Networks (ANNs for spatial interpolation of the monthly and annual values of rainfall erosivity at any location in the state of Rio Grande do Sul, and a software that enables the use of these networks in a simple and fast manner. This experiment used 103 rainfall stations in Rio Grande do Sul and their surrounding area to generate synthetic rainfall series on the software ClimaBR 2.0. Rainfall erosivity was determined by summing the values of the EI30 and KE >25 indexes, considering two methodologies for obtaining the kinetic energy of rainfall. With these values of rainfall erosivity and latitude, longitude, and altitude of the stations, the ANNs were trained and tested for spatializations of rainfall erosivity. To facilitate the use of the ANNs, a computer program was generated, called netErosividade RS, which makes feasible the use of ANNs to estimate the values of rainfall erosivity for any location in the state of Rio Grande do Sul.

  17. Predicting the temporal relationship between soil cesium-137 and erosion rate

    International Nuclear Information System (INIS)

    Kachanoski, R.G.; De Jong, E.

    1984-01-01

    A model was developed that predicts the amount of 137 Cs remaining in soil as a function of time and erosion rate. The model accounts for atmospheric deposition, radioactive decay, tillage dilution, and erosion transport of 137 Cs, as well as seasonal differences in 137 Cs deposition and erosion rates. The model was used to estimate minimum resolution of erosion estimates based on detection limits and accuracy of 137 Cs measurement by gamma spectroscopy, as a function of time and erosion rate. The analysis showed that under Saskatchewan conditions, changes in 137 Cs at a given site can be used to estimate erosion rates between 0.5 and 10 kg m -2 yr -1 with reasonable precision, provided the sampling interval is at least 15 yr. The relationship of fraction of 137 Cs lost vs. erosion as predicted by the model was compared with other methods being used. The model was used to estimate erosion from selected Saskatchewan soils where 137 Cs levels were measured in 1966 and again in 1981. Erosion rates calculated with the model varied from 1 kg m -2 yr -1 for a sandy loam soil in continuous forage to 19 kg m -2 yr -1 for a similar soil in a crop-fallow rotation. Erosion estimates using the model were higher than those calculated by assuming that soil loss was directly proportional to 137 Cs loss, especially when 137 Cs loss was high

  18. Soil Erosion as a stochastic process

    Science.gov (United States)

    Casper, Markus C.

    2015-04-01

    corrected experimentally. To overcome this disadvantage of our actual models, soil erosion models are needed that are able to use stochastic directly variables and parameter distributions. There are only some minor approaches in this direction. The most advanced is the model "STOSEM" proposed by Sidorchuk in 2005. In this model, only a small part of the soil erosion processes is described, the aggregate detachment and the aggregate transport by flowing water. The concept is highly simplified, for example, many parameters are temporally invariant. Nevertheless, the main problem is that our existing measurements and experiments are not geared to provide stochastic parameters (e.g. as probability density functions); in the best case they deliver a statistical validation of the mean values. Again, we get effective parameters, spatially and temporally averaged. There is an urgent need for laboratory and field experiments on overland flow structure, raindrop effects and erosion rate, which deliver information on spatial and temporal structure of soil and surface properties and processes.

  19. Stability of organic matter in soils of the Belgian Loess Belt upon erosion and deposition

    NARCIS (Netherlands)

    Wang, X.; Cammeraat, L.H.; Wang, Z.; Zhou, J.; Govers, G.; Kalbitz, K.

    2013-01-01

    Soil erosion has significant impacts on terrestrial carbon (C) dynamics. It removes C-rich topsoil and deposits it in lower areas, which might result in its stabilization against microbial decay. Subsequently, C-poor deeper horizons will be exposed, which also affects C stabilization. We analysed

  20. ESTIMATION OF THE WANDA GLACIER (SOUTH SHETLANDS SEDIMENT EROSION RATE USING NUMERICAL MODELLING

    Directory of Open Access Journals (Sweden)

    Kátia Kellem Rosa

    2013-09-01

    Full Text Available Glacial sediment yield results from glacial erosion and is influenced by several factors including glacial retreat rate, ice flow velocity and thermal regime. This paper estimates the contemporary subglacial erosion rate and sediment yield of Wanda Glacier (King George Island, South Shetlands. This work also examines basal sediment evacuation mechanisms by runoff and glacial erosion processes during the subglacial transport. This is small temperate glacier that has seen retreating for the last decades. In this work, we examine basal sediment evacuation mechanisms by runoff and analyze glacial erosion processes occurring during subglacial transport. The glacial erosion rate at Wanda Glacier, estimated using a numerical model that consider sediment evacuated to outlet streams, ice flow velocity, ice thickness and glacier area, is 1.1 ton m yr-1.

  1. Coastal erosion problem, modelling and protection

    Science.gov (United States)

    Yılmaz, Nihal; Balas, Lale; İnan, Asu

    2015-09-01

    Göksu Delta, located in the south of Silifke County of Mersin on the coastal plain formed by Göksu River, is one of the Specially Protected Areas in Turkey. Along the coastal area of the Delta, coastline changes at significant rates are observed, concentrating especially at four regions; headland of İncekum, coast of Paradeniz Lagoon, river mouth of Göksu and coast of Altınkum. The coast of Paradeniz Lagoon is suffering significantly from erosion and the consequent coastal retreating problem. Therefore, the narrow barrier beach which separates Paradeniz Lagoon from the Mediterranean Sea is getting narrower, creating a risk of uniting with the sea, thus causing the disappearance of the Lagoon. The aim of this study was to understand the coastal transport processes along the coastal area of Göksu Delta to determine the coastal sediment transport rates, and accordingly, to propose solutions to prevent the loss of coastal lands in the Delta. To this end, field measurements of currents and sediment grain sizes were carried out, and wind climate, wave climate, circulation patterns and longshore sediment transport rates were numerically modeled by HYDROTAM-3D, which is a three dimensional hydrodynamic transport model. Finally, considering its special importance as an environmentally protected region, some coastal structures of gabions were proposed as solutions against the coastal erosion problems of the Delta. The effects of proposed structures on future coastline changes were also modeled, and the coastlines predicted for the year 2017 are presented and discussed in the paper.

  2. Erosive tooth wear in children

    NARCIS (Netherlands)

    Carvalho, T.S.; Lussi, A.; Jaeggi, T.; Gambon, D.L.; Lussi, A.; Ganss, C.

    2014-01-01

    Erosive tooth wear in children is a common condition. Besides the anatomical differences between deciduous and permanent teeth, additional histological differences may influence their susceptibility to dissolution. Considering laboratory studies alone, it is not clear whether deciduous teeth are

  3. Erosion-resistant composite material

    Science.gov (United States)

    Finch, C.B.; Tennery, V.J.; Curlee, R.M.

    A highly erosion-resistant composite material is formed of chemical vapor-deposited titanium diboride on a sintered titanium diboride-nickel substrate. This material may be suitable for use in cutting tools, coal liquefaction systems, etc.

  4. Soil Erosion and Agricultural Sustainability

    Science.gov (United States)

    Montgomery, D. R.

    2009-04-01

    Data drawn from a global compilation of studies support the long articulated contention that erosion rates from conventionally plowed agricultural fields greatly exceed rates of soil production, erosion under native vegetation, and long-term geological erosion. Whereas data compiled from around the world show that soil erosion under conventional agriculture exceeds both rates of soil production and geological erosion rates by up to several orders of magnitude, similar global distributions of soil production and geological erosion rates suggest an approximate balance. Net soil erosion rates in conventionally plowed fields on the order of 1 mm/yr can erode typical hillslope soil profiles over centuries to millennia, time-scales comparable to the longevity of major civilizations. Well-documented episodes of soil loss associated with agricultural activities date back to the introduction of erosive agricultural methods in regions around the world, and stratigraphic records of accelerated anthropogenic soil erosion have been recovered from lake, fluvial, and colluvial stratigraphy, as well as truncation of soil stratigraphy (such as truncated A horizons). A broad convergence in the results from studies based on various approaches employed to study ancient soil loss and rates of downstream sedimentation implies that widespread soil loss has accompanied human agricultural intensification in examples drawn from around the world. While a broad range of factors, including climate variability and society-specific social and economic contexts — such as wars or colonial relationships — all naturally influence the longevity of human societies, the ongoing loss of topsoil inferred from studies of soil erosion rates in conventional agricultural systems has obvious long-term implications for agricultural sustainability. Consequently, modern agriculture — and therefore global society — faces a fundamental question over the upcoming centuries. Can an agricultural system

  5. Comprehensive model for disruption erosion in a reactor environment

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1995-01-01

    A comprehensive disruption erosion model which takes into account the interplay of major physical processes during plasma-material interaction has been developed. The model integrates with sufficient detail and in a self-consistent way, material thermal evolution response, plasma-vapor interaction physics, vapor hydrodynamics and radiation transport in order to realistically simulate the effects of a plasma disruption on plasma-facing components. Candidate materials such as beryllium and carbon have been analyzed. The dependence of the net erosion rate on disruption physics and various parameters was analyzed and is discussed. ((orig.))

  6. Surface erosion issues and analysis for dissipative divertors

    International Nuclear Information System (INIS)

    Brooks, J.N.; Ruzic, D.N.; Hayden, D.B.; Turkot, R.B. Jr.

    1994-05-01

    Erosion/redeposition is examined for the sidewall of a dissipative divertor using coupled impurity transport, charge exchange, and sputtering codes, applied to a plasma solution for the ITER design. A key issue for this regime is possible runaway self-sputtering, due to the effect of a low boundary density and nearly parallel field geometry on redeposition parameters. Net erosion rates, assuming finite self-sputtering, vary with wall location, boundary conditions, and plasma solution, and are roughly of the following order: 200--2000 angstrom/s for beryllium, 10--100 angstrom/s for vanadium, and 0.3--3 angstrom/s for tungsten

  7. Erosion properties of unipolar arcs

    International Nuclear Information System (INIS)

    Chekalin, Eh.K.

    1982-01-01

    Processes modelling the formation of unipolar arcs on the elements of the first wall in limiters of the vacuum chamber and on active elements of tokamak divertor, are experimentally investigated. Erosion, processes that take place at two types of non-stationary cathode spots are considered. Experimental data prove the possibility of reducing erosion intensity by coating the surface of electrodes by oxide films, reduction of the temperature of electrode and discharge current

  8. Effect of stone coverage on soil erosion

    Science.gov (United States)

    Jomaa, S.; Barry, D. A.; Heng, B. P.; Brovelli, A.; Sander, G. C.; Parlange, J.

    2010-12-01

    Soil surface coverage has a significant impact on water infiltration, runoff and soil erosion yields. In particular, surface stones protect the soils from raindrop detachment, they retard the overland flow therefore decreasing its sediment transport capacity, and they prevent surface sealing. Several physical and environmental factors control to what extent stones on the soil surface modify the erosion rates and the related hydrological response. Among the most important factors are the moisture content of the topsoil, stone size, emplacement, coverage density and soil texture. Owing to the different inter-related processes, there is ambiguity concerning the quantitative effect of stones, and process-based understanding is limited. Experiments were performed (i) to quantify how stone features affect sediment yields, (ii) to understand the local effect of isolated surface stones, that is, the changes of the soil particle size distribution in the vicinity of a stone and (iii) to determine how stones attenuate the development of surface sealing and in turn how this affects the local infiltration rate. A series of experiments using the EPFL 6-m × 2-m erosion flume were conducted at different rainfall intensities (28 and 74 mm h-1) and stone coverage (20 and 40%). The total sediment concentration, the concentration of the individual size classes and the flow discharge were measured. In order to analyze the measurements, the Hairsine and Rose (HR) erosion model was adapted to account for the shielding effect of the stone cover. This was done by suitably adjusting the parameters based on the area not covered by stones. It was found that the modified HR model predictions agreed well with the measured sediment concentrations especially for the long time behavior. Changes in the bulk density of the topsoil due to raindrop-induced compaction with and without stone protection revealed that the stones protect the upper soil surface against the structural seals resulting in

  9. The fate of SOC during the processes of water erosion and subsequent deposition: a field study.

    Science.gov (United States)

    van Hemelryck, H.; Govers, G.; van Oost, K.; Merckx, R.

    2009-04-01

    Globally soils are the largest terrestrial pool of carbon (C). A relatively small increase or decrease in soil carbon content due to changes in land use or management practices could therefore result in a significant net exchange of C between the soil C reservoir and the atmosphere. As such, the geomorphic processes of water and tillage erosion have been identified to significantly impact on this large pool of soil organic carbon (SOC). Soil erosion, transport and deposition not only result in redistribution of sediments and associated carbon within a landscape, but also affect the exchange of C between the pedosphere and the atmosphere. The direction and magnitude of an erosion-induced change in the global C balance is however a topic of much debate as opposing processes interact: i) At eroding sites a net uptake of C could be the result of reduced respiration rates and continued inputs of newly produced carbon. ii) Colluvial deposition of eroded sediment and SOC leads to the burial of the original topsoil and this may constrain the decomposition of its containing SOC. iii) Eroded sediment could be transported to distal depositional environments or fluvial systems where it will either be conserved or become rapidly mineralized. iv) Increased emission of CO2 due to erosion may result from the disruptive energy of erosive forces causing the breakdown of aggregates and exposing previously protected SOC to microbial decomposition. The above-mentioned processes show a large spatial and temporal variability and assessing their impact requires an integrated modeling approach. However uncertainties about the basic processes that accompany SOC displacement are still large. This study focuses on one of these large information gaps: the fate of eroded and subsequently deposited SOC. A preceding experimental study (Van Hemelryck et al., 2008) was used to identify controlling factors (erosional intensity, changes in soil structure,…). However this experimental research

  10. Comparison of fluid geochemistry and microbiology of multiple organic-rich reservoirs in the Illinois Basin, USA: Evidence for controls on methanogenesis and microbial transport

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, M.E.; McIntosh, J.C.; Bates, B.L.; Kirk, M.F.; Martini, A.M. [University of Arizona, Tucson, AZ (United States)

    2011-04-01

    The Illinois Basin, USA, is an ideal location to investigate hydrogeochemical factors controlling methanogenesis as microbial methane accumulations occur: (1) in three organic-rich reservoirs of different geologic ages and organic matter types - Upper Devonian New Albany Shale (up to 900 m depth), Pennsylvanian coals (up to 600 m depth), and Quaternary glacial sediments (shallow aquifers); (2) across steep salinity gradients; and (3) with variable concentrations of SO{sub 4}{sup 2-}. For all three organic-rich reservoirs aqueous geochemical conditions are favorable for microbial methanogenesis, with near neutral pH, SO{sub 4}{sup 2-} concentrations {gt}2 mM, and Cl{sup -} concentrations {lt}3 M. Also, carbon isotopic fractionation of CH{sub 4}, CO{sub 2}, and DIC is consistent with microbial methanogenesis, and increased carbon isotopic fractionation with average reservoir depth corresponds to a decrease of groundwater flushing rates with average depth of reservoir. Plots of stable isotopes of water and Cl{sup -} show mixing between a brine endmember and freshwater, suggesting that meteoric groundwater recharge has affected all microbial methanogenic systems. Additionally, similar methanogenic communities are present in all three reservoirs with comparable cell counts (8.69E3-2.58E6 cells/mL). TRFLP results show low numbers of archaea species with only two dominant groups of base pairs in coals, shale, and limestone aquifers. These results compare favorably with other methanogen-containing deep subsurface environments. The matching of variations between methanogenic TRFLP data and conservative tracers suggests that deep circulation of meteoric waters influenced archaeal communities in the Illinois Basin.

  11. Periodic sediment shift in migrating ripples influences benthic microbial activity

    Science.gov (United States)

    Zlatanović, Sanja; Fabian, Jenny; Mendoza-Lera, Clara; Woodward, K. Benjamin; Premke, Katrin; Mutz, Michael

    2017-06-01

    Migrating bedforms have high levels of particulate organic matter and high rates of pore water exchange, causing them to be proposed as hot spots of carbon turnover in rivers. Yet, the shifting of sediments and associated mechanical disturbance within migrating bedforms, such as ripples, may stress and abrade microbial communities, reducing their activity. In a microcosm experiment, we replicated the mechanical disturbances caused by the periodic sediment shift within ripples under oligotrophic conditions. We assessed the effects on fungal and bacterial biomass ratio (F:B), microbial community respiration (CR), and bacterial production (BCP) and compared with stable undisturbed sediments. Interactions between periodic mechanical disturbance and sediment-associated particulate organic matter (POM) were tested by enriching sediments collected from migrating ripples with different qualities of POM (fish feces, leaf litter fragments and no addition treatments). F:B and BCP were affected by an interaction between mechanical disturbance and POM quality. Fish feces enriched sediments showed increased F:B and BCP compared to sediments with lower POM quality and responded with a decrease of F:B and BCP to sediment disturbance. In the other POM treatments F:B and BCP were not affected by disturbance. Microbial respiration was however reduced by mechanical disturbance to similar low activity levels regardless of POM qualities added, whereas fish feces enriched sediment showed short temporary boost of CR. With the worldwide proliferation of migrating sand ripples due to massive catchment erosion, suppressed mineralization of POM will increasingly affect stream metabolism, downstream transport of POM and carbon cycling from reach to catchment scale.

  12. In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

    Science.gov (United States)

    Polzin, Kurt; Korman, Valentin

    2009-01-01

    One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster s operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. There are many different sensors and techniques that have been employed to quantify discharge channel erosion in Hall thrusters. Snapshots of the wear pattern can be obtained at regular shutdown intervals using laser profilometry. Many non-intrusive techniques of varying complexity and sensitivity have been employed to detect the time-varying presence of erosion products in the thruster plume. These include the use quartz crystal microbalances, emission spectroscopy, laser induced flourescence, and cavity ring-down spectroscopy. While these techniques can provide a very accurate picture of the level of eroded material in the thruster plume, it is more difficult to use them to determine the location from which the material was eroded. Furthermore, none of the methods cited provide a true in-situ measure of erosion at the channel surface while

  13. Modelling soil carbon fate under erosion process in vineyard

    Science.gov (United States)

    Novara, Agata; Scalenghe, Riccardo; Minacapilli, Mario; Maltese, Antonino; Capodici, Fulvio; Borgogno Mondino, Enrico; Gristina, Luciano

    2017-04-01

    Soil erosion processes in vineyards beyond water runoff and sediment transport have a strong effect on soil organic carbon loss (SOC) and redistribution along the slope. The variation of SOC across the landscape determines a difference in soil fertility and vine productivity. The aim of this research was to study erosion of a Mediterranean vineyard, develop an approach to estimate the SOC loss, correlate the vines vigor with sediment and carbon erosion. The study was carried out in a Sicilian (Italy) vineyard, planted in 2011. Along the slope, six pedons were studied by digging 6 pits up to 60cm depth. Soil was sampled in each pedon every 10cm and SOC was analyzed. Soil erosion, detachment and deposition areas were measured by pole height method. The vigor of vegetation was expressed in term of NDVI (Normalized difference Vegetation Index) derived from a satellite image (RapidEye) acquired at berry pre-veraison stage (July) and characterized by 5 spectral bands in the shortwave region, including a band in the red wavelength (R, 630-685 nm) and in the near infrared (NIR, 760-850 nm) . Results showed that soil erosion, sediments redistribution and SOC across the hill was strongly affected by topographic features, slope and curvature. The erosion rate was 46Mg ha-1 y-1 during the first 6 years since planting. The SOC redistribution was strongly correlated with the detachment or deposition area as highlighted by pole height measurements. The approach developed to estimate the SOC loss showed that during the whole study period the off-farm SOC amounts to 1.6Mg C ha-1. As highlighted by NDVI results, the plant vigor is strong correlated with SOC content and therefore, developing an accurate NDVI approach could be useful to detect the vineyard areas characterized by low fertility due to erosion process.

  14. Water erosion and climate change in a small alpine catchment

    Science.gov (United States)

    Berteni, Francesca; Grossi, Giovanna

    2017-04-01

    WATER EROSION AND CLIMATE CHANGE IN A SMALL ALPINE CATCHMENT Francesca Berteni, Giovanna Grossi A change in the mean and variability of some variables of the climate system is expected to affect the sediment yield of mountainous areas in several ways: for example through soil temperature and precipitation peak intensity change, permafrost thawing, snow- and ice-melt time shifting. Water erosion, sediment transport and yield and the effects of climate change on these physical phenomena are the focus of this work. The study area is a small mountainous basin, the Guerna creek watershed, located in the Central Southern Alps. The sensitivity of sediment yield estimates to a change of condition of the climate system may be investigated through the application of different models, each characterized by its own features and limits. In this preliminary analysis two different empirical mathematical models are considered: RUSLE (Revised Universal Soil Loss Equation; Renard et al., 1991) and EPM (Erosion Potential Method; Gavrilovic, 1988). These models are implemented in a Geographical Information System (GIS) supporting the management of the territorial database used to estimate relevant geomorphological parameters and to create different thematic maps. From one side the geographical and geomorphological information is required (land use, slope and hydrogeological instability, resistance to erosion, lithological characterization and granulometric composition). On the other side the knowledge of the weather-climate parameters (precipitation and temperature data) is fundamental as well to evaluate the intensity and variability of the erosive processes and estimate the sediment yield at the basin outlet. Therefore different climate change scenarios were considered in order to tentatively assess the impact on the water erosion and sediment yield at the small basin scale. Keywords: water erosion, sediment yield, climate change, empirical mathematical models, EPM, RUSLE, GIS

  15. Auto consolidated cohesive sediments erosion

    International Nuclear Information System (INIS)

    Ternat, F.

    2007-02-01

    Pollutants and suspended matters of a river can accumulate into the sedimentary column. Once deposited, they are submitted to self-weight consolidation processes, ageing and burying, leading to an increase of their erosion resistance. Pollutant fluxes can be related to sedimentary fluxes, determined by threshold laws. In this work, an erosion threshold model is suggested by introducing a cohesion force into the usual force balance. A model of cohesion is developed on the basis of interactions between argillaceous cohesive particles (clays), particularly the Van der Waals force, whose parameterization is ensured by means of granulometry and porosity. Artificial erosion experiments were performed in a recirculating erosion flume with natural cored sediments where critical shear stress measurements were performed. Other analyses provided granulometry and porosity. The results obtained constitute a good database for the literature. The model is then applied to the experimental conditions and gives good agreement with measurements. An example of the accounting for self-weight consolidation processes is finally suggested, before finishing on a Mohr like diagram dedicated to soft cohesive sediment erosion. (author)

  16. Microbial glycoproteomics

    DEFF Research Database (Denmark)

    Halim, Adnan; Anonsen, Jan Haug

    2017-01-01

    Mass spectrometry-based "-omics" technologies are important tools for global and detailed mapping of post-translational modifications. Protein glycosylation is an abundant and important post translational modification widespread throughout all domains of life. Characterization of glycoproteins...... and research in this area is rapidly accelerating. Here, we review recent developments in glycoproteomic technologies with a special focus on microbial protein glycosylation....

  17. AERO: A Decision Support Tool for Wind Erosion Assessment in Rangelands and Croplands

    Science.gov (United States)

    Galloza, M.; Webb, N.; Herrick, J.

    2015-12-01

    Wind erosion is a key driver of global land degradation, with on- and off-site impacts on agricultural production, air quality, ecosystem services and climate. Measuring rates of wind erosion and dust emission across land use and land cover types is important for quantifying the impacts and identifying and testing practical management options. This process can be assisted by the application of predictive models, which can be a powerful tool for land management agencies. The Aeolian EROsion (AERO) model, a wind erosion and dust emission model interface provides access by non-expert land managers to a sophisticated wind erosion decision-support tool. AERO incorporates land surface processes and sediment transport equations from existing wind erosion models and was designed for application with available national long-term monitoring datasets (e.g. USDI BLM Assessment, Inventory and Monitoring, USDA NRCS Natural Resources Inventory) and monitoring protocols. Ongoing AERO model calibration and validation are supported by geographically diverse data on wind erosion rates and land surface conditions collected by the new National Wind Erosion Research Network. Here we present the new AERO interface, describe parameterization of the underpinning wind erosion model, and provide a summary of the model applications across agricultural lands and rangelands in the United States.

  18. Bentonite erosion. Laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats (Div. of Nuclear Chemistry, Royal Inst. of Technology, Stockholm (Sweden), School of Chemical Science and Engineering)

    2009-11-15

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain

  19. Microbial Energy Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, Merry [American Society for Microbiology (ASM), Washington, DC (United States); Wall, Judy D. [Univ. of Missouri, Columbia, MO (United States)

    2006-10-01

    natural gas from the subsurface. The participants discussed--key microbial conversion paths; overarching research issues; current funding models and microbial energy research; education, training, interdisciplinary cooperation and communication. Their recommendations are--Cellulose and lignocellulose are the preferred substrates for producing liquid transportation fuels, of which ethanol is the most commonly considered example. Generating fuels from these materials is still difficult and costly. A number of challenges need to be met in order to make the conversion of cellulose and lignocellulose to transportation fuels more cost-competitive. The design of hydrogen-producing bioreactors must be improved in order to more effectively manage hydrogen removal, oxygen exclusion, and, in the case of photobioreactors, to capture light energy more efficiently. Methane production may be optimized by fine-tuning methanogenic microbial communities. The ability to transfer electrons to an anode in a microbial fuel cell is probably very broadly distributed in the bacterial world. The scientific community needs a larger inventory of cultivated microorganisms from which to draw for energy conversion development. New and unusual organisms for manufacturing fuels and for use in fuel cells can be discovered using bioprospecting techniques. Particular emphasis should be placed on finding microbes, microbial communities, and enzymes that can enhance the conversion of lignocellulosic biomass to usable sugars. Many of the microbial processes critical to energy conversion are carried out by complex communities of organisms, and there is a need to better understand the community interactions that make these transformations possible. Better understanding of microbial community structure, robustness, networks, homeostasis, and cell-to-cell signaling is also needed. A better understanding of the basic enzymology of microorganisms is needed in order to move forward more quickly with microbial energy

  20. An assessment for the erosion rate of DEMO first wall

    Science.gov (United States)

    Tokar, M. Z.

    2018-01-01

    In a fusion reactor a significant fraction of plasma particles lost from the confined volume will reach the vessel wall. The recombination of these charged species, electrons and ions of hydrogen isotopes, is a source of neutral molecules and atoms, recycling back into the plasma. Here they participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically oriented velocities are generated. A significant fraction of these hot neutrals will hit the wall, leading, as well as the outflowing fuel and impurity ions, to its erosion, limiting the reactor operation time. The rate of the wall erosion in DEMO is assessed by applying a one-dimensional model which takes into account the transport of charged and neutral species across the flux surfaces in the main part of the scrape-off layer, beyond the X-point vicinity and divertor, and by considering the shift of the centers of flux surfaces, their elongation and triangularity. Atoms generated by c-x of recycling neutrals are modeled kinetically to define firmly their energy spectrum, being of particular importance for the erosion assessment. It is demonstrated the erosion rate of the DEMO wall armor of tungsten will have a pronounced ballooning character with a significant maximum of 0.3 mm per full power year at the low field side, decreasing with an increase in the anomalous perpendicular transport in the ‘far’ SOL or the plasma density at the separatrix.

  1. Soil erosion in Slovene Istria

    Directory of Open Access Journals (Sweden)

    Matjaž Mikoš

    2009-12-01

    Full Text Available From the end of nineties of the 20th century, intense hydrologic and geomorphologic research is taking place in the Slovene Istria. As a part of this research also studies on soil erosion were undertaken in the period from 2005 to 2008. The field measurements were under taken onclosed 1m2 large erosion plots under three different land uses (on bare soils in an olive grove, on an overgrown meadow, in a forest, placed south of the Marezige village in the Rokava River basin.We show weekly measurements of surface erosion (interrill erosion for the period of 13 months (the end of March 2005 – the end of April 2006, as well as monthly and seasonal averages together with selected linear statistical correlations between soil erosion and weather parameters.From May 2005 to April 2006 the interrill erosion on bare soils in an olive grove with an inclination of 5.5° amounted to 9013 g/m2 (90 t/ha that corresponds to surface lowering rate of 8.5 mm/yr; on an overgrown meadow with an inclination of 9.4° it amounted to 168 g/m2 (1,68 t/ha that corresponds to surface lowering rate of 0.16 mm//yr; and in a forest with an inclination of 7.8° it amounted to 391 g/m2 (3,91 t/ha and in a forest with an inclination of 21.4° it amounted to 415 g/m2 (4,15 t/ha, respectively, that corresponds to surface lowering rate of 0.4 mm/yr.

  2. EFFECTS OF SLOPE SHAPES ON SOIL EROSION

    Directory of Open Access Journals (Sweden)

    Hüseyin ŞENSOY, Şahin PALTA

    2009-01-01

    Full Text Available Water is one of the most important erosive forces. A great number of factors also play a role in erosion process and slope characteristic is also one of them. The steepness and length of the slope are important factors for runoff and soil erosion. Another slope factor that has an effect on erosion is the shape of the slope. Generally, different erosion and runoff characteristics exist in different slopes which can be classified as uniform, concave, convex and complex shape. In this study, the effects of slope shape on erosion are stated and emphasized by taking similar researches into consideration.

  3. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  4. Modeling runoff and microbial overland transport with KINEROS2/STWIR model: Accuracy and uncertainty as affected by source of infiltration parameters

    Science.gov (United States)

    Infiltration is important to modeling the overland transport of microorganisms in environmental waters. In watershed- and hillslope scale-models, infiltration is commonly described by simple equations relating infiltration rate to soil saturated conductivity and by empirical para...

  5. Microbial xanthophylls.

    Science.gov (United States)

    Bhosale, Prakash; Bernstein, Paul S

    2005-09-01

    Xanthophylls are oxygenated carotenoids abundant in the human food supply. Lutein, zeaxanthin, and cryptoxanthin are major xanthophyll carotenoids in human plasma. The consumption of these xanthophylls is directly associated with reduction in the risk of cancers, cardiovascular disease, age-related macular degeneration, and cataract formation. Canthaxanthin and astaxanthin also have considerable importance in aquaculture for salmonid and crustacean pigmentation, and are of commercial interest for the pharmaceutical and food industries. Chemical synthesis is a major source for the heavy demand of xanthophylls in the consumer market; however, microbial producers also have potential as commercial sources. In this review, we discuss the biosynthesis, commercial utility, and major microbial sources of xanthophylls. We also present a critical review of current research and technologies involved in promoting microbes as potential commercial sources for mass production.

  6. Forest soil erosion prediction as influenced by wildfire and roads

    Science.gov (United States)

    Cao, L.; Brooks, E. S.; Elliot, W.

    2017-12-01

    Following a wildfire, the risk of erosion is greatly increased. Forest road networks may change the underlying topography and alter natural flow paths. Flow accumulation and energy can be redistributed by roads and alter soil erosion processes. A LiDAR (Light Detection and Ranging) DEM makes it possible to quantify road topography, and estimate how roads influence surface runoff and sediment transport in a fire-disturbed watershed. With GIS technology and a soil erosion model, this study was carried out to evaluate the effect of roads on erosion and sediment yield following the Emerald Fire southwest of Lake Tahoe. The GeoWEPP model was used to estimate onsite erosion and offsite sediment delivery from each hillslope polygon and channel segment before and after fire disturbance in part of the burned area. The GeoWEPP flow path method was used to estimate the post-fire erosion rate of each GIS pixel. A 2-m resolution LiDAR DEM was used as the terrain layer. The Emerald Fire greatly increased onsite soil loss and sediment yields within the fire boundary. Following the fire, 78.71% of the burned area had predicted sediment yields greater than 4 Mg/ha/yr, compared to the preburn condition when 65.3% of the study area was estimated to generate a sediment yield less than 0.25 Mg/ha/yr. Roads had a remarkable influence on the flow path simulation and sub-catchments delineation, affecting sediment transport process spatially. Road segments acted as barriers that intercepted overland runoff and reduced downslope flow energy accumulation, therefore reducing onsite soil loss downslope of the road. Roads also changed the boundary of sub-catchment and defined new hydrological units. Road segments can transport sediment from one sub-catchment to another. This in turn leads to the redistribution of sediment and alters sediment yield for some sub-catchments. Culverts and road drain systems are of vital importance in rerouting runoff and sediment. Conservation structures can be

  7. Contribution of raindrop impact to the change of soil physical properties and water erosion under semi-arid rainfalls

    NARCIS (Netherlands)

    Vaezi, Ali Reza; Ahmadi, Morvarid; Cerda Bolinches, Artemio

    2017-01-01

    Soil erosion by water is a three-phase process that consists of detachment of soil particles from the soil mass, transportation of detached particles either by raindrop impact or surface water flow, and sedimentation. Detachment by raindrops is a key component of the soil erosion process. However,

  8. Estacionalidad de la erosión y el transporte eólico de partículas en el desierto costero de Atacama, Chile (23°S Seasonality of erosion and eolian particle transport in the coastal Atacama Desert, Chile (23°S

    Directory of Open Access Journals (Sweden)

    Valentina Flores-Aqueveque

    2009-07-01

    characterized by the occurrence of strong south- and southwesterly winds. The arid climate, fíat geomorphology and the characteristics of the superficial sediments on Pampa Mejillones, located in northern Chile (ca. 23°S, favor the study of eolian erosion and transport processes in this coastal desert. In situ measurements of the horizontal particle flux (G and winds in the área, together with sedimentological analyses of the uppermost part of the pampa sediments, allowed determination of the significant parameters in the eolian erosión and particle transport process and its seasonality. A local surface roughness parameter (z0 of about 10-3 m was calculated, which is a typical value of desert plains. Seasonally, values of G up to 2,100 g cm-1 month-1 were observed, associated with friction velocities (u* between 0,4 and 0,5 m s-1 during the spring of 2000. Similar results were obtained for the years 1999 and 2001. The sedimentology (granulometry and surface texture and mineralogy of the surface and captured material in the dust traps show that the transported fraction is characterized mainly by quartz and feldspars, with grain-size modes between 75 and 1,000 um, similar to those observed in nearby soils and south (upwind of the capture area. The results obtained and preliminary correlation of measured winds at the different meteorological stations on the Mejillones Península, indicate a direct relationship between the horizontal particle flux towards Mejillones Bay and the regional south-southwest winds, especially during spring and summer, simultaneous with the intensification of winds favoring coastal upwelling in the area.

  9. Estimating erosion in a riverine watershed: Bayou Liberty-Tchefuncta River in Louisiana.

    Science.gov (United States)

    Martin, August; Gunter, James T; Regens, James L

    2003-01-01

    GOAL, SCOPE, BACKGROUND: Sheet erosion from agricultural, forest and urban lands may increase stream sediment loads as well as transport other pollutants that adversely affect water quality, reduce agricultural and forest production, and increase infrastructure maintenance costs. This study uses spatial analysis techniques and a numerical modeling approach to predict areas with the greatest sheet erosion potential given different soils disturbance scenarios. A Geographic Information System (GIS) and the Universal Soil Loss Equation (USLE) were used to estimate sheet erosion from 0.64 ha parcels of land within the watershed. The Soil Survey of St. Tammany Parish, Louisiana was digitized, required soil attributes entered into the GIS database, and slope factors determined for each 80 x 80 meter parcel in the watershed. The GIS/USLE model used series-specific erosion K factors, a rainfall factor of 89, and a GIS database of scenario-driven cropping and erosion control practice factors to estimate potential soil loss due to sheet erosion. A general trend of increased potential sheet erosion occurred for all land use categories (urban, agriculture/grasslands, forests) as soil disturbance increases from cropping, logging and construction activities. Modeling indicated that rapidly growing urban areas have the greatest potential for sheet erosion. Evergreen and mixed forests (production forest) had lower sheet erosion potentials; with deciduous forests (mostly riparian) having the least sheet erosion potential. Erosion estimates from construction activities may be overestimated because of the value chosen for the erosion control practice factor. This study illustrates the ease with which GIS can be integrated with the Universal Soil Loss Equation to identify areas with high sheet erosion potential for large scale management and policy decision making. The GIS/USLE modeling approach used in this study offers a quick and inexpensive tool for estimating sheet erosion within

  10. Elevated temperature erosive wear of metallic materials

    International Nuclear Information System (INIS)

    Roy, Manish

    2006-01-01

    Solid particle erosion of metals and alloys at elevated temperature is governed by the nature of the interaction between erosion and oxidation, which, in turn, is determined by the thickness, pliability, morphology, adhesion characteristics and toughness of the oxide scale. The main objective of this paper is to critically review the present state of understanding of the elevated temperature erosion behaviour of metals and alloys. First of all, the erosion testing at elevated temperature is reviewed. This is followed by discussion of the essential features of elevated temperature erosion with special emphasis on microscopic observation, giving details of the erosion-oxidation (E-O) interaction mechanisms. The E-O interaction has been elaborated in the subsequent section. The E-O interaction includes E-O maps, analysis of transition criteria from one erosion mechanism to another mechanism and quantification of enhanced oxidation kinetics during erosion. Finally, the relevant areas for future studies are indicated. (topical review)

  11. Understanding Soil Erosion in Irrigated Agriculture

    OpenAIRE

    O' Schwankl, Lawrence J

    2006-01-01

    A soil's physical and chemical properties determine whether it is vulnerable to erosion, which can reduce soil quality and cause other problems besides. Learn the basics of identifying what type of erosion is affecting your land and what's causing it.

  12. Impurity injection into tokamak plasmas by erosion probes

    International Nuclear Information System (INIS)

    Hildebrandt, D.; Bakos, J.S.; Buerger, G.; Paszti, F.; Petravich, G.

    1987-08-01

    Exposing special erosion probes into the edge plasma of MT-1 the impurities Li and Ti were released and contaminated the plasma. By the use of collector probes the torodial transport of these impurities were investigated. The results indicate a preferential impurity flow into codirection of the plasma current. However, the asymmetric component of this flow is much larger than expected from the toroidal drift correlated to the plasma current. (author)

  13. Impacts of shoreline erosion on coastal ecosystems in Songkhla Province

    Directory of Open Access Journals (Sweden)

    Nipaporn Chusrinuan

    2009-07-01

    Full Text Available Songkhla Province is located on the eastern coast of the southern Thai Peninsula, bordering the Gulf of Thailand for approximately 107 km. Most of the basin’s foreshores have been extensively developed for housing, tourism and shrimp farming. The beaches are under deteriorating impacts, often causing sediment transport which leads to an unnaturally high erosion rate. This natural phenomenon is considered to be a critical problem in the coastal areas affected by the hazard of coastal infrastructure and reduced beach esthetics for recreation. In this study, shoreline changes were compared between 1975 and 2006 using aerial photographs and Landsat imageries using Geographic Information System (GIS. The results revealed that 18.5 km2 of the coastal areas were altered during the period. Of this, 17.3 km2 suffered erosion and 1.2 km2were subjected to accretion. The most significant changes occurred between 1975-2006. Shoreline erosion was found at Ban Paktrae, Ranot District, with an average erosion rate of 5.3 m/year, while accretion occurred at Laem Samila, MuangSongkhla District with an average accretion rate of 2.04 m/year. The occurrences of shoreline erosion have contributed to the degradation of coastal soil and water quality, destruction of beach and mangrove forests, loss of human settlements and livelihood.These processes have led to deterioration of the quality of life of the residents. Prevention and mitigation measures to lessen economic and social impacts due to shoreline erosion are discussed.

  14. Erosion of the first wall of Tokamaks

    International Nuclear Information System (INIS)

    Guseva, M.I.; Ionova, E.S.; Martynenko, Yu.V.

    1980-01-01

    An estimate of the rate of erosion of the wall due to sputtering and blistering requires knowledge of the fluxes and energies of the particles which go from the plasma to the wall, of the sputtering coefficients S, and of the erosion coefficients S* for blistering. The overall erosion coefficient is equal to the sum of the sputtering coefficient and the erosion coefficient for blistering. Here the T-20 Tokamak is examined as an example of a large-scale Tokamak. 18 refs

  15. Soil Erosion. LC Science Tracer Bullet.

    Science.gov (United States)

    Buydos, John F., Comp.

    Soil erosion is the detachment and movement of topsoil or soil material from the upper part of the soil profile. It may occur in the form of rill, gully, sheet, or wind erosion. Agents of erosion may be water, wind, glacial ice, agricultural implements, machinery, and animals. Soil conservation measures require a thorough understanding of the…

  16. Natural and anthropogenic rates of soil erosion

    Science.gov (United States)

    Regions of land that are brought into crop production from native vegetation typically undergo a period of soil erosion instability, and long term erosion rates are greater than for natural lands as long as the land continues being used for crop production. Average rates of soil erosion under natur...

  17. Soil erosion in humid regions: a review

    Science.gov (United States)

    Daniel J. Holz; Karl W.J. Williard; Pamela J. Edwards; Jon E. Schoonover

    2015-01-01

    Soil erosion has significant implications for land productivity and surface water quality, as sediment is the leading water pollutant worldwide. Here, erosion processes are defined. The dominant factors influencing soil erosion in humid areas are reviewed, with an emphasis on the roles of precipitation, soil moisture, soil porosity, slope steepness and length,...

  18. The control of divertor carbon erosion/redeposition in the DIII-D tokamak

    International Nuclear Information System (INIS)

    Whyte, D.G.; West, W.P.; Wong, C.P.C.

    2001-01-01

    The DIII-D tokamak has demonstrated an operational scenario where the graphite-covered divertor is free of net erosion. Reduction of divertor carbon erosion is accomplished using a low temperature (detached) divertor plasma that eliminates physical sputtering. Likewise, the carbon source rate arising from chemical erosion is found to be very low in the detached divertor. Near strikepoint regions, the rate of carbon deposition is ∼3 cm/burn-year, with a corresponding hydrogenic codeposition rate >1kg/m 2 /burn-year; rates both problematic for steady-state fusion reactors. The carbon net deposition rate in the divertor is consistent with carbon arriving from the core plasma region. Carbon influx from the main wall is measured to be relatively large in the high-density detached regime and is of sufficient magnitude to account for the deposition rate in the divertor. Divertor redeposition is therefore determined by non-divertor erosion and transport. Despite the success in reducing divertor erosion on DIII-D with detachment, no significant reduction is found in the core plasma carbon density, illustrating the importance of non-divertor erosion and the complex coupling between erosion/redeposition and impurity plasma transport. (author)

  19. Erosion of atmospherically deposited radionuclides as affected by soil disaggregation mechanisms

    International Nuclear Information System (INIS)

    Claval, D.; Garcia-Sanchez, L.; Real, J.; Rouxel, R.; Mauger, S.; Sellier, L.

    2004-01-01

    The interactions of soil disaggregation with radionuclide erosion were studied under controlled conditions in the laboratory on samples from a loamy silty-sandy soil. The fate of 134 Cs and 85 Sr was monitored on soil aggregates and on small plots, with time resolution ranging from minutes to hours after contamination. Analytical experiments reproducing disaggregation mechanisms on aggregates showed that disaggregation controls both erosion and sorption. Compared to differential swelling, air explosion mobilized the most by producing finer particles and increasing five-fold sorption. For all the mechanisms studied, a significant part of the contamination was still unsorbed on the aggregates after an hour. Global experiments on contaminated sloping plots submitted to artificial rainfalls showed radionuclide erosion fluctuations and their origin. Wet radionuclide deposition increased short-term erosion by 50% compared to dry deposition. A developed soil crust when contaminated decreased radionuclide erosion by a factor 2 compared to other initial soil states. These erosion fluctuations were more significant for 134 Cs than 85 Sr, known to have better affinity to soil matrix. These findings confirm the role of disaggregation on radionuclide erosion. Our data support a conceptual model of radionuclide erosion at the small plot scale in two steps: (1) radionuclide non-equilibrium sorption on mobile particles, resulting from simultaneous sorption and disaggregation during wet deposition and (2) later radionuclide transport by runoff with suspended matter

  20. Forces acting on particles in a Pelton bucket and similarity considerations for erosion

    Science.gov (United States)

    Rai, A. K.; Kumar, A.; Staubli, T.

    2016-11-01

    High sediment transport rates cause severe erosion issues in hydropower plants leading to interruptions in power generation, decrease in efficiency and shutdown for repair and maintenance. For Pelton turbines operating at high head, the issue of erosion is severe, especially in components like buckets, nozzle rings and needles. Goal of the study is to develop erosion focussed guidelines for both designing as well as operating hydropower plants with Pelton runners. In this study, the flow of sediment inside a Pelton bucket with respect to forces acting on solid particles is analysed with an analytical approach by considering different dynamic forces originating from the rotation of the turbine, the curvature of the buckets, and the Coriolis effect. Further, the path of sediment particles and its effect on erosion phenomena are analysed based on the process of separation of different sized sediment particles from streamlines. The data relating to head, power, discharge, number of jet and efficiency of 250 hydropower plants installed all over the world were analysed in this study to find the major factors related to erosion in Pelton turbine bucket. From analysis of different force ratios, it is found that an increase of D/B, i.e. the ratio of pitch circle diameter and bucket width, and/or decrease of specific speed (nq) enhances erosion. As the erosion process depends significantly on nondimensional parameters D/B and nq, these are considered as similarity measures for scaling of the erosion process in the Pelton buckets of various sizes.

  1. Susceptibility of coarse-textured soils to soil erosion by water in the tropics

    International Nuclear Information System (INIS)

    Salako, F.K.

    2004-01-01

    The application of soil physics for the evaluation of factors of soil erosion in the tropics received considerable attention in the last four decades. In Nigeria, physical characteristics of rainfall such as drop size and drop-size distribution, rainfall intensity at short intervals and kinetic energy of rainfall were evaluated using different methods. Thus, compound erosivity indices were evaluated which showed a similar trend in annual rainfall erosivity with annual rainfall amounts. Attempts have also been made to use geostatistical tools and fractal theory to describe temporal variability in rainfall erosivity. High erosivity aggravates the vulnerability of coarse-textured soils to erosion. These soils, high in sand content were poorly aggregated and structurally weak. Thus, they were easily detached and transported by runoff. Long-term data are needed to describe factors of soil erosion in the tropics but quite often, equipment are not available or poorly maintained where available such that useful data are not collected. A greater cooperation of pure physicists, soil physicists and engineers in the developing nations is needed to improve or design equipment and methods for the characterization of factors of soil erosion in the tropics. (author)

  2. Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets.

    Science.gov (United States)

    Khamanga, Sandile M; Walker, Roderick B

    2006-01-01

    Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

  3. Long-term modeling of soil C erosion and sequestration at the small watershed scale

    Energy Technology Data Exchange (ETDEWEB)

    Izaurralde, R.C.; Thomson, A.M. [The Joint Global Change Research Institute, 8400 Baltimore Avenue, Suite 201, College Park, MD 20740-2496 (United States); Williams, J.R. [Blacklands Research Center, Texas A and M University, 808 East Blacklands Road, Temple, TX 76502 (United States); Post, W.M. [Oak Ridge National Laboratory, Building 1509, Bethel Valley Road, PO Box 2008 MS6335, Oak Ridge, TN 537831-6335 (United States); McGill, W.B. [College of Science and Management, University of Northern British Columbia, 3333 University Way, Prince George, BC V2N 4Z9 (Canada); Owens, L.B. [North Appalachian Experimental Watershed, USDA-Agricultural Research Station, 28850 SR 621, Coshocton, OH 43812-0488 (United States); Lal, R. [School of Natural Resources Food, Agricultural and Environmental Sciences, The Ohio State University, 422B Kottman Hall, 2021 Coffey Road, Columbus, OH 43210 (United States)

    2007-01-15

    The soil C balance is determined by the difference between inputs (e.g., plant litter, organic amendments, depositional C) and outputs (e.g., soil respiration, dissolved organic C leaching, and eroded C). There is a need to improve our understanding of whether soil erosion is a sink or a source of atmospheric CO2. The objective of this paper is to discover the long-term influence of soil erosion on the C cycle of managed watersheds near Coshocton, OH. We hypothesize that the amount of eroded C that is deposited in or out of a watershed compares in magnitude to the soil C changes induced via microbial respiration. We applied the erosion productivity impact calculator (EPIC) model to evaluate the role of erosion-deposition processes on the C balance of three small watersheds ({approx}1 ha). Experimental records from the USDA North Appalachian Experimental Watershed facility north of Coshocton, OH were used in the study. Soils are predominantly silt loam and have developed from loess-like deposits over residual bedrock. Management practices in the three watersheds have changed over time. Currently, watershed 118 (W118) is under a corn (Zea mays L.)-soybean (Glycine max [L.] Merr.) no till rotation, W128 is under conventional till continuous corn, and W188 is under no till continuous corn. Simulations of a comprehensive set of ecosystem processes including plant growth, runoff, and water erosion were used to quantify sediment C yields. A simulated sediment C yield of 43 {+-} 22 kg C ha{sup -1} year{sup -1} compared favorably against the observed 31 {+-} 12 kg C ha{sup -1} year{sup -1} in W118. EPIC overestimated the soil C stock in the top 30-cm soil depth in W118 by 21% of the measured value (36.8 Mg C ha{sup -1}). Simulations of soil C stocks in the other two watersheds (42.3 Mg C ha{sup -1} in W128 and 50.4 Mg C ha{sup -1} in W188) were off by <1 Mg C ha{sup -1}. Simulated eroded C re-deposited inside (30-212 kg C ha{sup -1} year{sup -1}) or outside (73{sup -1}79 kg

  4. Long-term modeling of soil C erosion and sequestration at the small watershed scale

    International Nuclear Information System (INIS)

    Izaurralde, R.C.; Thomson, A.M.; Williams, J.R.; Post, W.M.; McGill, W.B.; Owens, L.B.; Lal, R.

    2007-01-01

    The soil C balance is determined by the difference between inputs (e.g., plant litter, organic amendments, depositional C) and outputs (e.g., soil respiration, dissolved organic C leaching, and eroded C). There is a need to improve our understanding of whether soil erosion is a sink or a source of atmospheric CO2. The objective of this paper is to discover the long-term influence of soil erosion on the C cycle of managed watersheds near Coshocton, OH. We hypothesize that the amount of eroded C that is deposited in or out of a watershed compares in magnitude to the soil C changes induced via microbial respiration. We applied the erosion productivity impact calculator (EPIC) model to evaluate the role of erosion-deposition processes on the C balance of three small watersheds (∼1 ha). Experimental records from the USDA North Appalachian Experimental Watershed facility north of Coshocton, OH were used in the study. Soils are predominantly silt loam and have developed from loess-like deposits over residual bedrock. Management practices in the three watersheds have changed over time. Currently, watershed 118 (W118) is under a corn (Zea mays L.)-soybean (Glycine max [L.] Merr.) no till rotation, W128 is under conventional till continuous corn, and W188 is under no till continuous corn. Simulations of a comprehensive set of ecosystem processes including plant growth, runoff, and water erosion were used to quantify sediment C yields. A simulated sediment C yield of 43 ± 22 kg C ha -1 year -1 compared favorably against the observed 31 ± 12 kg C ha -1 year -1 in W118. EPIC overestimated the soil C stock in the top 30-cm soil depth in W118 by 21% of the measured value (36.8 Mg C ha -1 ). Simulations of soil C stocks in the other two watersheds (42.3 Mg C ha -1 in W128 and 50.4 Mg C ha -1 in W188) were off by -1 . Simulated eroded C re-deposited inside (30-212 kg C ha -1 year -1 ) or outside (73 -1 79 kg C ha -1 year -1 ) watershed boundaries compared in magnitude to a

  5. Modeling the fluid/soil interface erosion in the Hole Erosion Test

    Directory of Open Access Journals (Sweden)

    Kissi B.

    2012-07-01

    Full Text Available Soil erosion is a complex phenomenon which yields at its final stage to insidious fluid leakages under the hydraulic infrastructures known as piping and which are the main cause of their rupture. The Hole Erosion Test is commonly used to quantify the rate of piping erosion. In this work, The Hole Erosion Test is modelled by using Fluent software package. The aim is to predict the erosion rate of soil during the hole erosion test. The renormalization group theory – based k–ε turbulence model equations are used. This modelling makes it possible describing the effect of the clay concentration in flowing water on erosion. Unlike the usual one dimensional models, the proposed modelling shows that erosion is not uniform erosion along the hole length. In particular, the concentration of clay is found to increase noticeably the erosion rate.

  6. The Arctic Coastal Erosion Problem

    Energy Technology Data Exchange (ETDEWEB)

    Frederick, Jennifer M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Thomas, Matthew Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bull, Diana L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jones, Craig A. [Integral Consulting Inc., San Francisco, CA (United States); Roberts, Jesse D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-09-01

    Permafrost-dominated coastlines in the Arctic are rapidly disappearing. Arctic coastal erosion rates in the United States have doubled since the middle of the twentieth century and appear to be accelerating. Positive erosion trends have been observed for highly-variable geomorphic conditions across the entire Arctic, suggesting a major (human-timescale) shift in coastal landscape evolution. Unfortunately, irreversible coastal land loss in this region poses a threat to native, industrial, scientific, and military communities. The Arctic coastline is vast, spanning more than 100,000 km across eight nations, ten percent of which is overseen by the United States. Much of area is inaccessible by all-season roads. People and infrastructure, therefore, are commonly located near the coast. The impact of the Arctic coastal erosion problem is widespread. Homes are being lost. Residents are being dispersed and their villages relocated. Shoreline fuel storage and delivery systems are at greater risk. The U.S. Department of Energy (DOE) and Sandia National Laboratories (SNL) operate research facilities along some of the most rapidly eroding sections of coast in the world. The U.S. Department of Defense (DOD) is struggling to fortify coastal radar sites, operated to ensure national sovereignty in the air, against the erosion problem. Rapid alterations to the Arctic coastline are facilitated by oceanographic and geomorphic perturbations associated with climate change. Sea ice extent is declining, sea level is rising, sea water temperature is increasing, and permafrost state is changing. The polar orientation of the Arctic exacerbates the magnitude and rate of the environmental forcings that facilitate coastal land area loss. The fundamental mechanics of these processes are understood; their non-linear combination poses an extreme hazard. Tools to accurately predict Arctic coastal erosion do not exist. To obtain an accurate predictive model, a coupling of the influences of

  7. Microbial effects

    International Nuclear Information System (INIS)

    Sharpe, V.J.

    1985-10-01

    The long term safety and integrity of radioactive waste disposal sites proposed for use by Ontario Hydro may be affected by the release of radioactive gases. Microbes mediate the primary pathways of waste degradation and hence an assessment of their potential to produce gaseous end products from the breakdown of low level waste was performed. Due to a number of unknown variables, assumptions were made regarding environmental and waste conditions that controlled microbial activity; however, it was concluded that 14 C and 3 H would be produced, albeit over a long time scale of about 1500 years for 14 C in the worst case situation

  8. Carbon redistribution by erosion processes in an intensively disturbed catchment

    Science.gov (United States)

    Boix-Fayos, Carolina; Martínez-Mena, María; Pérez Cutillas, Pedro; de Vente, Joris; Barberá, Gonzalo G.; Mosch, Wouter; Navarro Cano, Jose Antonio; Gaspar, Leticia; Navas, Ana

    2016-04-01

    Understanding how organic carbon moves with sediments along the fluvial system is crucial to close catchment scale carbon budgets. Especially challenging is the analysis of organic carbon dynamics during fluvial transport in heterogeneous, fragile and disturbed environments with ephemeral and intense hydrological pulses, typical of Mediterranean conditions. This paper explores the catchment scale organic carbon redistribution by lateral flows in extreme Mediterranean environmental conditions from a geomorphological perspective. The study area is a catchment (Cárcavo) in SE Spain with a semiarid climate, erodible lithologies, shallow soils, and highly disturbed by agricultural terraces, land levelling, reforestations and construction of check-dams. To increase understanding of erosion induced catchment scale organic carbon redistribution, we studied the subcatchments of 8 check-dams distributed along the catchment main channel in detail. We determined 137Cs, physicochemical characteristics and organic carbon pools of soils and sediments deposited behind each check-dam, performed spatial analysis of properties of the catchment and buffer areas around check-dams, and carried out geomorphological analysis of the slope-channel connections. Soils showed very low Total Organic Carbon (TOC) values oscillating between 15.2 and 4.4 g Kg-1 for forest and agricultural soils, respectively. Sediments mobilized by erosion were poor in TOC compared to the eroded (forest) soils (6.6±0.7 g Kg-1), and the redistribution of organic carbon through the catchment, especially of the Mineral Associated Organic Carbon (MAC) pool, showed the same pattern as clay particles and 137Cs. The TOC erosion rates (0.031±0.03 Mg ha-1 y-1) were comparable to others reported for subhumid Mediterranean catchments and to those modelled worldwide for pasture land. Those lateral fluxes were equivalent to 10.4 % of the TOC stock from the topsoil at the moment of the check-dam construction and

  9. Preventing erosion at pipeline crossings of watercourses

    International Nuclear Information System (INIS)

    Sawatsky, L.; Arnold, G.

    1997-01-01

    Watercourses are naturally vulnerable to erosion but the risk is particularly acute after sub-soil and armour materials have been disturbed by trenching and backfilling during construction. Various types of erosion (river scour, river bed, river channel bed and river bank ) and the progressive removal of pipeline cover resulting from erosion were discussed. Methods of estimating the risk of progressive erosion, river avulsions and beaver dam scour, and methods of mitigating erosion at pipeline crossings such as deep burial, proper siting, conventional armouring, and a combination of bank toe protection, and upper bank vegetation cover, were described

  10. Soil Erosion Threatens Food Production

    Directory of Open Access Journals (Sweden)

    Michael Burgess

    2013-08-01

    Full Text Available Since humans worldwide obtain more than 99.7% of their food (calories from the land and less than 0.3% from the oceans and aquatic ecosystems, preserving cropland and maintaining soil fertility should be of the highest importance to human welfare. Soil erosion is one of the most serious threats facing world food production. Each year about 10 million ha of cropland are lost due to soil erosion, thus reducing the cropland available for world food production. The loss of cropland is a serious problem because the World Health Organization and the Food and Agricultural Organization report that two-thirds of the world population is malnourished. Overall, soil is being lost from agricultural areas 10 to 40 times faster than the rate of soil formation imperiling humanity’s food security.

  11. On inhibition of dental erosion.

    Science.gov (United States)

    Rölla, Gunnar; Jonski, Grazyna; Saxegaard, Erik

    2013-11-01

    To examine the erosion-inhibiting effect of different concentrations of hydrofluoric acid. Thirty-six human molars were individually treated with 10 ml of 0.1 M citric acid for 30 min (Etch 1), acid was collected and stored until analysis. The teeth were randomly divided into six groups and then individually treated with 10 ml of one of six dilutions (from 0.1-1%) of hydrofluoric acid. The teeth were then again treated with citric acid (Etch 2). The individual acid samples from Etch 1 and 2 were analyzed for calcium by flame atomic absorption spectroscopy and difference in calcium loss was calculated. The highest erosion inhibiting effect was obtained in groups with the highest concentrations of hydrofluoric acid, where the pH was lowest, below pKa of 3.17, thus the hydrofluoric acids being mainly in an undissociated state. Diluted hydrofluoric acid is present in aqueous solution of SnF2 and TiF4 (which are known to inhibit dental erosion): SnF2 + 3H2O = Sn(OH)2 + 2HF + H2O and TiF4 + 5H2O = Ti(OH)4 + 4HF + H2O. It is also known that pure, diluted hydrofluoric acid can inhibit dental erosion. Teeth treated with hydrofluoric acid are covered by a layer of CaF2-like mineral. This mineral is acid resistant at pH acid resistant mineral, initiated by tooth enamel treatment with hydrofluoric acid. Hydrofluoric acid is different in having fluoride as a conjugated base, which provides this acid with unique properties.

  12. Erosive forms in rivers systems

    International Nuclear Information System (INIS)

    Una Alvarez, E. de; Vidal Romani, J. R.; Rodriguez Martinez-Conde, R.

    2009-01-01

    The purpose of this work is to analyze the geomorphological meaning of the concepts of stability/change and to study its influence on a fluvial erosion system. Different cases of fluvial potholes in Galicia (NW of the Iberian Peninsula) are considered. The work conclusions refer to the nature of the process and its morphological evolution in order to advance towards later contributions with respect of this type of systems. (Author) 14 refs.

  13. Comparison of erosion and erosion control works in Macedonia, Serbia and Bulgaria

    Directory of Open Access Journals (Sweden)

    Ivan Blinkov

    2013-12-01

    Natural conditions in the Balkan countries contribute to the appearance of various erosion forms and the intensity of the erosion processes. Over the history of these countries, people who settled this region used the available natural resources to fill their needs (tree cutting, incorrect plugging, overgrazing, which contributed to soil erosion. Organized erosion control works in the Balkans started in the beginning of the 20th century (1905 in Bulgaria. The highest intensity of erosion control works were carried out during the period 1945 – 1990. Various erosion control works were launched. Bulgaria had a large anti-erosion afforestation, almost 1 million ha. Bulgaria's ecological river restoration approach has been in use for almost 50 years. Serbia contributed significant erosion and torrent control works on hilly agricultural areas. Specific screen barrages and afforestation on extremely dry areas are characteristic in Macedonia. A common characteristic for all countries is a high decrease in erosion control works in the last 20 years.

  14. The influence of basal-ice debris on patterns and rates of glacial erosion

    Science.gov (United States)

    Ugelvig, Sofie V.; Egholm, David L.

    2018-05-01

    Glaciers have played a key role for shaping much of Earth's high topography during the cold periods of the Late Cenozoic. However, despite of their distinct influence on landscapes, the mechanisms of glacial erosion, and the properties that determine their rate of operation, are still poorly understood. Theoretical models of subglacial erosion generally highlight the influence of basal sliding in setting the pace of erosion, but they also point to a strong influence of other subglacial properties, such as effective bed pressure and basal-ice debris concentration. The latter properties are, however, not easily measured in existing glaciers, and hence their influence cannot readily be confirmed by observations. In order to better connect theoretical models for erosion to measurable properties in glaciers, we used computational landscape evolution experiments to study the expected influence of basal-ice debris concentration for subglacial abrasion at the scale of glaciers. The computational experiments couple the two erosion processes of quarrying and abrasion, and furthermore integrate the flow of ice and transport of debris within the ice, thus allowing for the study of dynamic feedbacks between subglacial erosion and systematic glacier-scale variations in basal-ice debris concentration. The experiments explored several physics-based models for glacial erosion, in combination with different models for basal sliding to elucidate the relationship between sliding speed, erosion rate and basal-ice debris concentration. The results demonstrate how differences in debris concentration can explain large variations in measured rates. The experiments also provide a simple explanation for the observed dependence of glacier-averaged rate of erosion on glacier size: that large glacier uplands feed more debris into their lower-elevation parts, thereby strengthening their erosive power.

  15. Techniques for assessing water resource potentials in the developing countries: with emphasis on streamflow, erosion and sediment transport, water movement in unsaturated soils, ground water, and remote sensing in hydrologic applications

    Science.gov (United States)

    Taylor, George C.

    1971-01-01

    . Nuclear methodology in hydrologic applications is generally more complex than the conventional and hence requires a high level of technical expertise for effective use. Application of nuclear techniques to hydrologic problems in the developing countries is likely to be marginal for some years to come, owing to the higher costs involved and expertise required. Nuclear techniques, however, would seem to have particular promise in studies of water movement in unsaturated soils and of erosion and sedimentation where conventional techniques are inadequate, inefficient and in some cases costly. Remote sensing offers great promise for synoptic evaluations of water resources and hydrologic processes, including the transient phenomena of the hydrologic cycle. Remote sensing is not, however, a panacea for deficiencies in hydrologic data programs in the developing countries. Rather it is a means for extending and augmenting on-the-ground observations ans surveys (ground truth) to evaluated water resources and hydrologic processes on a regionall or even continental scale. With respect to economic growth goals in developing countries, there are few identifiable gaps in existing hydrologic instrumentation and methodology insofar as appraisal, development and management of available water resources are concerned. What is needed is acceleration of institutional development and professional motivation toward more effective use of existing and proven methodology. Moreover, much sophisticated methodology can be applied effectively in the developing countries only when adequate levels of indigenous scientific skills have been reached and supportive institutional frameworks are evolved to viability.

  16. Soil Production and Erosion Rates and Processes in Mountainous Landscapes

    Science.gov (United States)

    Heimsath, A. M.; DiBiase, R. A.; Whipple, K. X.

    2012-12-01

    We focus here on high-relief, steeply sloped landscapes from the Nepal Himalaya to the San Gabriels of California that are typically thought to be at a critical threshold of soil cover. Observations reveal that, instead, there are significant areas mantled with soil that fit the conceptual framework of a physically mobile layer derived from the underlying parent material with some locally-derived organic content. The extent and persistence of such soils depends on the long-term balance between soil production and erosion despite the perceived discrepancy between high erosion and low soil production rates. We present cosmogenic Be-10-derived soil production and erosion rates that show that soil production increases with catchment-averaged erosion, suggesting a feedback that enhances soil-cover persistence, even in threshold landscapes. Soil production rates do decline systematically with increasing soil thickness, but hint at the potential for separate soil production functions for different erosional regimes. We also show that a process transistion to landslide-dominated erosion results in thinner, patchier soils and rockier topography, but find that there is no sudden transition to bedrock landscapes. Our landslide modeling is combined with a detailed quantification of bedrock exposure for these steep, mountainous landscapes. We also draw an important conclusion connecting the physical processes producing and transporting soil and the chemical processes weathering the parent material by measuring parent material strength across three different field settings. We observe that parent material strength increases with overlying soil thickness and, therefore, the weathered extent of the saprolite. Soil production rates, thus, decrease with increasing parent material competence. These observation highlight the importance of quantifying hillslope hydrologic processes where such multi-facted measurements are made.

  17. On the role of "internal variability" on soil erosion assessment

    Science.gov (United States)

    Kim, Jongho; Ivanov, Valeriy; Fatichi, Simone

    2017-04-01

    Empirical data demonstrate that soil loss is highly non-unique with respect to meteorological or even runoff forcing and its frequency distributions exhibit heavy tails. However, all current erosion assessments do not describe the large associated uncertainties of temporal erosion variability and make unjustified assumptions by relying on central tendencies. Thus, the predictive skill of prognostic models and reliability of national-scale assessments have been repeatedly questioned. In this study, we attempt to reveal that the high variability in soil losses can be attributed to two sources: (1) 'external variability' referring to the uncertainties originating at macro-scale, such as climate, topography, and land use, which has been extensively studied; (2) 'geomorphic internal variability' referring to the micro-scale variations of pedologic properties (e.g., surface erodibility in soils with multi-sized particles), hydrologic properties (e.g., soil structure and degree of saturation), and hydraulic properties (e.g., surface roughness and surface topography). Using data and a physical hydraulic, hydrologic, and erosion and sediment transport model, we show that the geomorphic internal variability summarized by spatio-temporal variability in surface erodibility properties is a considerable source of uncertainty in erosion estimates and represents an overlooked but vital element of geomorphic response. The conclusion is that predictive frameworks of soil erosion should embed stochastic components together with deterministic assessments, if they do not want to largely underestimate uncertainty. Acknowledgement: This study was supported by the Basic Science Research Program of the National Research Foundation of Korea funded by the Ministry of Education (2016R1D1A1B03931886).

  18. Using albedo to reform wind erosion modelling, mapping and monitoring

    Science.gov (United States)

    Chappell, Adrian; Webb, Nicholas P.

    2016-12-01

    Wind erosion and dust emission models are used to assess the impacts of dust on radiative forcing in the atmosphere, cloud formation, nutrient fertilisation and human health. The models are underpinned by a two-dimensional geometric property (lateral cover; L) used to characterise the three-dimensional aerodynamic roughness (sheltered area or wakes) of the Earth's surface and calibrate the momentum it extracts from the wind. We reveal a fundamental weakness in L and demonstrate that values are an order of magnitude too small and significant aerodynamic interactions between roughness elements and their sheltered areas have been omitted, particularly under sparse surface roughness. We describe a solution which develops published work to establish a relation between sheltered area and the proportion of shadow over a given area; the inverse of direct beam directional hemispherical reflectance (black sky albedo; BSA). We show direct relations between shadow and wind tunnel measurements and thereby provide direct calibrations of key aerodynamic properties. Estimation of the aerodynamic parameters from albedo enables wind erosion assessments over areas, across platforms from the field to airborne and readily available satellite data. Our new approach demonstrated redundancy in existing wind erosion models and thereby reduced model complexity and improved fidelity. We found that the use of albedo enabled an adequate description of aerodynamic sheltering to characterise fluid dynamics and predict sediment transport without the use of a drag partition scheme (Rt) or threshold friction velocity (u∗t). We applied the calibrations to produce global maps of aerodynamic properties which showed very similar spatial patterns to each other and confirmed the redundancy in the traditional parameters of wind erosion modelling. We evaluated temporal patterns of predicted horizontal mass flux at locations across Australia which revealed variation between land cover types that would not

  19. Deposition and erosion in local shadow regions of TEXTOR-94

    International Nuclear Information System (INIS)

    Wienhold, P.; Mayer, M.; Kirschner, A.; Rubel, M.; Hildebrandt, D.; Schneider, W.

    2001-01-01

    Carbon erosion and deposition were investigated on the surface of a flat target covered with an a-C:H film and exposed for 197 s in the SOL of TEXTOR-94. The target was declined by 20 with respect to the toroidal direction and partly protected by an aluminum (3 mm) plate which created an 8 mm wide local shadow. Thickness changes were measured by colorimetry after each plasma discharge. Carbon is eroded from surface areas near the plasma edge (LCFS +1 cm) and transported into the local shadow regions. Accumulation rates up to ∼7 nm/s were found. The erosion in the local shadow regions (about -0.1 nm/s) is due to charge exchange neutrals. The observations are confirmed by ion beam analyses and by preliminary calculations with the B2-EIRENE and ERO-TEXTOR code. (orig.)

  20. Is Snow Gliding a Major Soil Erosion Agent in Steep Alpine Areas?

    International Nuclear Information System (INIS)

    Meusburger, K.; Walter, A.; Alewell, C.; Leitinger, G.; Mabit, L.; Mueller, M.H.

    2015-01-01

    Snow cover is a key hydrological characteristic of mountain areas. Nevertheless, a majority of studies focused on quantifying rates of soil erosion and sediment transport in steep mountain areas has largely neglected the role of snow cover on soil erosion rates (Stanchi et al., 2014). Soil erosion studies have focused almost exclusively on the snow-free periods even though it is well known that wet avalanches can yield enormous erosive forces (Freppaz et al., 2010; Korup and Rixen, 2014). This raises the question whether annual snow cover and particularly the slow movement of snow packages over the soil surface, termed ‘‘snow gliding’’, contribute significantly to the total soil loss in these areas. Three different approaches to estimate soil erosion rates were used to address this question. These include (1) the anthropogenic soil tracer 137 Cs, (2) the Revised Universal Soil Loss Equation (RUSLE), and (3) direct sediment yield measurements of snow glide deposits. The fallout radionuclide 137 Cs integrates total soil loss due to all erosion agents involved, the RUSLE model is suitable to estimate soil loss by water erosion and the sediment yield measurements yield represents a direct estimate of soil removal by snow gliding. Moreover, cumulative snow glide distance was measured for 14 sites and modelled for the surrounding area with the Spatial Snow Glide Model (Leitinger et al., 2008)

  1. Cavitation erosion - scale effect and model investigations

    Science.gov (United States)

    Geiger, F.; Rutschmann, P.

    2015-12-01

    The experimental works presented in here contribute to the clarification of erosive effects of hydrodynamic cavitation. Comprehensive cavitation erosion test series were conducted for transient cloud cavitation in the shear layer of prismatic bodies. The erosion pattern and erosion rates were determined with a mineral based volume loss technique and with a metal based pit count system competitively. The results clarified the underlying scale effects and revealed a strong non-linear material dependency, which indicated significantly different damage processes for both material types. Furthermore, the size and dynamics of the cavitation clouds have been assessed by optical detection. The fluctuations of the cloud sizes showed a maximum value for those cavitation numbers related to maximum erosive aggressiveness. The finding suggests the suitability of a model approach which relates the erosion process to cavitation cloud dynamics. An enhanced experimental setup is projected to further clarify these issues.

  2. Mapping monthly rainfall erosivity in Europe

    DEFF Research Database (Denmark)

    Ballabio, C; Meusburger, K; Klik, A

    2017-01-01

    to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive...... and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part...... selected among various statistical models to perform the spatial interpolation due to its excellent performance, ability to model non-linearity and interpretability. The monthly prediction is an order more difficult than the annual one as it is limited by the number of covariates and, for consistency...

  3. Erosion and sedimentation caused by watercourse regulation

    International Nuclear Information System (INIS)

    Dahl, T.E.; Godtland, K.

    1995-01-01

    This report describes the observations made by SINTEF NHL in 1993 - 1994 on the development of erosion in three regulated lakes in Norway: Devdesjavri, Store Maalvatn and Gjevilvatnet. Surveys, profile levelling, water sample analyses, aerial photography etc were all used. Erosion was dramatic in all three magazines the first year of regulation and then slowed down. It has since remained relatively stable. However, there is a risk of further strong erosion connected with flooding tributaries, notably at low water such as usually occurs in spring. This is true in particular of the main river discharging into Devdesjavri, which is subject to landslides, wave and river erosion. In addition, ground water erosion may occur if the magazine is drained too fast. The report is lavishly illustrated with colour pictures of the effects of erosion. 21 refs., 15 figs., 13 tabs

  4. Varioliform erosions in the stomach and duodenum

    Energy Technology Data Exchange (ETDEWEB)

    Lotz, W.; Schulz, D.; Munkel, G.

    1984-04-01

    One thousand five hundred and eighty-three patients who were x-rayed for dyspepsia showed varioliform erosions in 15.3%. Men had an incidence of 9.8%, almost twice as common as in women (5.5%). Mucosal polyps, usually of the hyperplastic type, occurred in 2.4%. 15% of patients with gastric ulcers and 16% of patients with duodenal ulcers had varioliform erosions. On the other hand, amongst patients with erosions, 11% had gastric ulcers and 8.3% duodenal ulcers. The definitions of erosion which have been given in the literature are partly contradictory, and are discussed. Varioliform erosions, also known as complete erosions, may be acute or chronic. They are the third most common cause of bleeding from the upper gastrointestinal tract. With modern radiological methods of examining the stomach, they are no longer a rare finding. 5 figs.

  5. Varioliform erosions in the stomach and duodenum

    International Nuclear Information System (INIS)

    Lotz, W.; Schulz, D.; Munkel, G.

    1984-01-01

    One thousand five hundred and eighty-three patients who were x-rayed for dyspepsia showed varioliform erosions in 15.3%. Men had an incidence of 9.8%, almost twice as common as in women (5.5%). Mucosal polyps, usually of the hyperplastic type, occurred in 2.4%. 15% of patients with gastric ulcers and 16% of patients with duodenal ulcers had varioliform erosions. On the other hand, amongst patients with erosions, 11% had gastric ulcers and 8.3% duodenal ulcers. The definitions of erosion which have been given in the literature are partly contradictory, and are discussed. Varioliform erosions, also known as complete erosions, may be acute or chronic. They are the third most common cause of bleeding from the upper gastrointestinal tract. With modern radiological methods of examining the stomach, they are no longer a rare finding. (orig.) [de

  6. Assessment and management of dental erosion.

    Science.gov (United States)

    Wang, Xiaojie; Lussi, Adrian

    2010-07-01

    Studies have shown a growing trend toward increasing prevalence of dental erosion, associated with the declining prevalence of caries disease in industrialized countries. Erosion is an irreversible chemical process that results in tooth substance loss and leaves teeth susceptible to damage as a result of wear over the course of an individual's lifetime. Therefore, early diagnosis and adequate prevention are essential to minimize the risk of tooth erosion. Clinical appearance is the most important sign to be used to diagnose erosion. The Basic Erosive Wear Examination (BEWE) is a simple method to fulfill this task. The determination of a variety of risk and protective factors (patient-dependent and nutrition-dependent factors) as well as their interplay are necessary to initiate preventive measures tailored to the individual. When tooth loss caused by erosive wear reaches a certain level, oral rehabilitation becomes necessary. Copyright 2010 Elsevier Inc. All rights reserved.

  7. DENTAL EROSION IN PRIMARY DENTITION- A REVIEW

    Directory of Open Access Journals (Sweden)

    Rafi Shaik

    2017-06-01

    Full Text Available BACKGROUND The pattern of oral diseases has been influenced by ever changing human lifestyle. Tooth wear especially dental erosion has drawn increasing attention as risk factor for tooth damage or loss in recent years. It is a common condition in primary dentition compared to permanent dentition due to thinner and less mineralised enamel. However, it is more worrying, when this condition is being found in an alarming proportion among children. The presence of dental erosion in children is likely to be associated with a number of general health and dietary factors, but it is also aggravated by the relatively more rapid progression of erosion in the deciduous teeth. An understanding of the aetiologies and risk factors for erosion is important for early recognition of dental erosion to prevent serious irreversible damage to the dentition. This paper discusses the erosion in children with regard to its epidemiology, prevalence, clinical features, measurement and prevention.

  8. Lifespan of mountain ranges scaled by feedbacks between landsliding and erosion by rivers.

    Science.gov (United States)

    Egholm, David L; Knudsen, Mads F; Sandiford, Mike

    2013-06-27

    An important challenge in geomorphology is the reconciliation of the high fluvial incision rates observed in tectonically active mountain ranges with the long-term preservation of significant mountain-range relief in ancient, tectonically inactive orogenic belts. River bedrock erosion and sediment transport are widely recognized to be the principal controls on the lifespan of mountain ranges. But the factors controlling the rate of erosion and the reasons why they seem to vary significantly as a function of tectonic activity remain controversial. Here we use computational simulations to show that the key to understanding variations in the rate of erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides. Whereas fluvial incision steepens surrounding hillslopes and increases landslide frequency, landsliding affects fluvial erosion rates in two fundamentally distinct ways. On the one hand, large landslides overwhelm the river transport capacity and cause upstream build up of sediment that protects the river bed from further erosion. On the other hand, in delivering abrasive agents to the streams, landslides help accelerate fluvial erosion. Our models illustrate how this coupling has fundamentally different implications for rates of fluvial incision in active and inactive mountain ranges. The coupling therefore provides a plausible physical explanation for the preservation of significant mountain-range relief in old orogenic belts, up to several hundred million years after tectonic activity has effectively ceased.

  9. Charge-exchange wall physical erosion rates for a proposed INTOR/FED limiter

    International Nuclear Information System (INIS)

    Heifetz, D.; Schmidt, J.; Ulrickson, M.; Post, D.

    1983-01-01

    We have analyzed power deposition and physical erosion rates on the first wall and limiter due to charge-exchange neutrals in a proposed pump limiter design for the INTOR/FED tokamak. Plasma conditions were modeled using the one-dimensional plasma transport code baldur. Neutral transport was modeled using a two-dimensional, multispecies Monte Carlo algorithm. No chemical erosion or wall redeposition processes were included. Two possible plasma discharges with different edge densities and temperatures were modeled, a regime with T/sub e/ approx.300 eV and napprox.5 x 10 12 cm - 3 , and a hotter, less dense edge regime produced with pellet fueling. We found that the erosion of the stainless steel vacuum vessel wall was highly localized in each case to the two points just beyond the limiter tips, and to the point directly across from the neutralizer plate, with peak erosion rates approx.2 cm/yr, assuming a 40% duty cycle. The erosion of a carbon limiter, neglecting redeposition and chemical erosion, varied in the two cases from 1.6--4 cm/yr, for the same duty cycle. The hotter, less dense discharge produced less sputtering. However achieving truly tolerable physical sputtering rates may require a very low edge temperature, plasma

  10. Spatio-temporal variability in accretion and erosion of coastal foredunes in the Netherlands: regional climate and local topography.

    Science.gov (United States)

    Keijsers, Joep G S; Poortinga, Ate; Riksen, Michel J P M; Maroulis, Jerry

    2014-01-01

    Depending on the amount of aeolian sediment input and dune erosion, dune size and morphology change over time. Since coastal foredunes play an important role in the Dutch coastal defence, it is important to have good insight in the main factors that control these changes. In this paper the temporal variations in foredune erosion and accretion were studied in relation to proxies for aeolian transport potential and storminess using yearly elevation measurements from 1965 to 2012 for six sections of the Dutch coast. Longshore differences in the relative impacts of erosion and accretion were examined in relation to local beach width. The results show that temporal variability in foredune accretion and erosion is highest in narrow beach sections. Here, dune erosion alternates with accretion, with variability displaying strong correlations with yearly values of storminess (maximum sea levels). In wider beach sections, dune erosion is less frequent, with lower temporal variability and stronger correlations with time series of transport potential. In erosion dominated years, eroded volumes decrease from narrow to wider beaches. When accretion dominates, dune-volume changes are relatively constant alongshore. Dune erosion is therefore suggested to control spatial variability in dune-volume changes. On a scale of decades, the volume of foredunes tends to increase more on wider beaches. However, where widths exceed 200 to 300 m, this trend is no longer observed.

  11. PROBLEMS OF SOIL PROTECTION FROM EROSION

    OpenAIRE

    M. Voloshuk; Natalia Kiriak

    2007-01-01

    In this article the problems of soil protection from erosion in Moldova are considered. The history (evolution) of erosive processes is generalized, the first items of information on presence washed off soils are marked. Purposeful study of soil erosion, development of measures of struggle with it were begun in Moldova at the end of 40 years. In connection with transition to new economic methods of conducting economy (farmers, rent, privatization of land) before pedologist, the experts of des...

  12. [Responses of accumulation-loss patterns for soil organic carbon and its fractions to tillage and water erosion in black soil area].

    Science.gov (United States)

    Zhao, Peng Zhi; Chen, Xiang Wei; Wang, En Heng

    2017-11-01

    Tillage and water erosion have been recognized as the main factors causing degradation in soil organic carbon (SOC) pools of black soil. To further explore the response of SOC and its fractions to different driving forces of erosion (tillage and water), geostatistical methods were used to analyze spatial patterns of SOC and its three fractions at a typical sloping farmland based on tillage and water erosion rates calculated by local models. The results showed that tillage erosion and deposition rates changed according to the slope positions, decreasing in the order: upper-slope > lower-slope > middle-slope > toe-slope and toe-slope > lower-slope > middle-slope > upper-slope, respectively; while the order of water erosion rates decreased in the order: lower-slope > toe-slope > middle-slope > upper-slope. Tillage and water erosion cooperatively triggered intense soil loss in the lower-slope areas with steep slope gradient. Tillage erosion could affect C cycling through the whole slope at different levels, although the rate of tillage erosion (0.02-7.02 t·hm -2 ·a -1 ) was far less than that of water erosion (5.96-101.17 t·hm -2 ·a -1 ) in black soil area. However, water erosion only played a major role in controlling C dynamics in the runoff-concentrated lower slope area. Affected by water erosion and tillage erosion-deposition disturbance, the concentrations of SOC, particulate organic carbon and dissolved organic carbon in depositional areas were higher than in erosional areas, however, microbial biomass carbon showed an opposite trend. Tillage erosion dominated SOC dynamic by depleting particulate organic carbon.

  13. Distributed Modeling of soil erosion and deposition affected by buffer strips

    DEFF Research Database (Denmark)

    Khademalrasoul, Ataalah; Heckrath, Goswin Johann; Iversen, Bo Vangsø

    bodies. Buffer zones can be efficient in terms of retaining sediment and phosphorus transported by water erosion. This study aimed at parameterizing a spatial distributed erosion model to evaluate the effect of different buffer zone properties and dimension. It was our hypothesis that the placement...... was surveyed during the runoff season. In addition, organic carbon and phosphorous contents as well as bulk density were determined in soils of eroding and depositional sites. General buffer zone properties were recorded. Here we present results from scenario analyses comparing measured sediment deposition......Soil degradation and environmental impacts due to water erosion are a growing concern globally. Large parts of Denmark are covered by gently rolling moraine landscape with moderately to locally highly erodible soils where water erosion causes off-site problems in the form of eutrophication of water...

  14. Erosion products in disruption simulation experiments

    International Nuclear Information System (INIS)

    Safronov, V.; Arkhipov, N.; Bakhtin, V.; Barsuk, V.; Kurkin, S.; Mironova, E.; Toporkov, D.; Vasenin, S.; Zhitlukhin, A.; Arkhipov, I.; Werle, H.; Wuerz, H.

    1998-01-01

    Erosion of divertor materials under tokamak disruption event presents a serious problem of ITER technology. Erosion restricts the divertor lifetime and leads to production of redeposited layers of the material retaining large amount of tritium, which is a major safety issue for future fusion reactor. Since ITER disruptive heat loads are not achievable in existing tokamaks, material erosion is studied in special simulation experiments. Till now the simulation experiments have focused mainly on investigation of shielding effect and measurement of erosion rate. In the present work the properties of eroded and redeposited graphite are studied under condition typical for hard ITER disruption. (author)

  15. Reduction of surface erosion in fusion reactors

    International Nuclear Information System (INIS)

    Rossing, T.D.; Das, S.K.; Kaminsky, M.

    1976-01-01

    Some of the major processes leading to surface erosion in fusion reactors are reviewed briefly, including blistering by implanted gas, sputtering by ions, atoms, and neutrons, and vaporization by local heating. Surface erosion affects the structural integrity and limits the lifetime of reactor components exposed to plasma radiation. In addition, some of the processes leading to surface erosion also cause the release of plasma contaminants. Methods proposed to reduce surface erosion have included control of surface temperature, selection of materials with a favorable microstructure, chemical and mechanical treatment of surfaces, and employment of protective surface coatings, wall liners, and divertors. The advantages and disadvantages of some of these methods are discussed

  16. Erosive lichen planus: a therapeutic challenge.

    Science.gov (United States)

    Romero, Williams; Giesen, Laura; Navajas-Galimany, Lucas; Gonzalez, Sergio

    2016-01-01

    Erosive lichen planus is an uncommon variant of lichen planus. Chronic erosions of the soles, accompanied by intense and disabling pain, are some of its most characteristic manifestations. We present the case of a woman who developed oral and plantar erosive lichen planus associated with lichen planus pigmentosus and ungueal lichen planus that were diagnosed after several years. The patient failed to respond to multiple therapies requiring longstanding medication but remained refractory. Knowledge of the treatment options for erosive lichen planus is insufficient. Further research is required to clarify their effectiveness, ideally adopting an evidence-based methodology.

  17. Robotic weld overlay coatings for erosion control

    Science.gov (United States)

    The erosion of materials by the impact of solid particles has received increasing attention during the past twenty years. Recently, research has been initiated with the event of advanced coal conversion processes in which erosion plays an important role. The resulting damage, termed Solid Particle Erosion (SPE), is of concern primarily because of the significantly increased operating costs which result in material failures. Reduced power plant efficiency due to solid particle erosion of boiler tubes and waterfalls has led to various methods to combat SPE. One method is to apply coatings to the components subjected to erosive environments. Protective weld overlay coatings are particularly advantageous in terms of coating quality. The weld overlay coatings are essentially immune to spallation due to a strong metallurgical bond with the substrate material. By using powder mixtures, multiple alloys can be mixed in order to achieve the best performance in an erosive environment. However, a review of the literature revealed a lack of information on weld overlay coating performance in erosive environments which makes the selection of weld overlay alloys a difficult task. The objective of this project is to determine the effects of weld overlay coating composition and microstructure on erosion resistance. These results will lead to a better understanding of erosion mitigation in CFB's.

  18. Diagnostic pitfalls in newborns and babies with blisters and erosions.

    Science.gov (United States)

    Nischler, Elke; Klausegger, Alfred; Hüttner, Clemens; Pohla-Gubo, Gabriele; Diem, Anja; Bauer, Johann W; Hintner, Helmut

    2009-01-01

    Establishing the correct diagnosis in newborns presenting with blisters and erosions is not always a straightforward process. Many different disease entities including acquired (i.e., infectious, immunobullous, traumatic) and inherited disorders have to be taken into consideration. Similarities in clinical appearance, colonization and/or superinfections of preexisting skin lesions, as well as the absence of late changes in the neonate often pose significant diagnostic challenges. In this paper we discuss by giving examples the process of making an accurate diagnosis of blistering skin diseases in the neonatal period on the basis of a diagnostic algorithm. In addition, we provide an overview of the rational use and the limitations of laboratory procedures such as microbial testing, routine light microscopy, immunofluorescence antigen mapping, transmission electron microscopy, and molecular genetic analysis.

  19. Diagnostic Pitfalls in Newborns and Babies with Blisters and Erosions

    Directory of Open Access Journals (Sweden)

    Elke Nischler

    2009-01-01

    Full Text Available Establishing the correct diagnosis in newborns presenting with blisters and erosions is not always a straightforward process. Many different disease entities including acquired (i.e., infectious, immunobullous, traumatic and inherited disorders have to be taken into consideration. Similarities in clinical appearance, colonization and/or superinfections of preexisting skin lesions, as well as the absence of late changes in the neonate often pose significant diagnostic challenges. In this paper we discuss by giving examples the process of making an accurate diagnosis of blistering skin diseases in the neonatal period on the basis of a diagnostic algorithm. In addition, we provide an overview of the rational use and the limitations of laboratory procedures such as microbial testing, routine light microscopy, immunofluorescence antigen mapping, transmission electron microscopy, and molecular genetic analysis.

  20. Farmers' identification of erosion indicators and related erosion damage in the Central Highlands of Kenya

    NARCIS (Netherlands)

    Sterk, G.; Okoba, B.O.

    2006-01-01

    Most soil and water conservation planning approaches rely on empirical assessment methods and hardly consider farmers' knowledge of soil erosion processes. Farmers' knowledge of on-site erosion indicators could be useful in assessing the site-specific erosion risk before planning any conservation

  1. Quantifying the erosion effect on current carbon budget of European agricultural soils at high spatial resolution.

    Science.gov (United States)

    Lugato, Emanuele; Paustian, Keith; Panagos, Panos; Jones, Arwyn; Borrelli, Pasquale

    2016-05-01

    The idea of offsetting anthropogenic CO2 emissions by increasing global soil organic carbon (SOC), as recently proposed by French authorities ahead of COP21 in the 'four per mil' initiative, is notable. However, a high uncertainty still exits on land C balance components. In particular, the role of erosion in the global C cycle is not totally disentangled, leading to disagreement whether this process induces lands to be a source or sink of CO2. To investigate this issue, we coupled soil erosion into a biogeochemistry model, running at 1 km(2) resolution across the agricultural soils of the European Union (EU). Based on data-driven assumptions, the simulation took into account also soil deposition within grid cells and the potential C export to riverine systems, in a way to be conservative in a mass balance. We estimated that 143 of 187 Mha have C erosion rates 0.45 Mg C ha(-1) yr(-1). In comparison with a baseline without erosion, the model suggested an erosion-induced sink of atmospheric C consistent with previous empirical-based studies. Integrating all C fluxes for the EU agricultural soils, we estimated a net C loss or gain of -2.28 and +0.79 Tg yr(-1) of CO2 eq, respectively, depending on the value for the short-term enhancement of soil C mineralization due to soil disruption and displacement/transport with erosion. We concluded that erosion fluxes were in the same order of current carbon gains from improved management. Even if erosion could potentially induce a sink for atmospheric CO2, strong agricultural policies are needed to prevent or reduce soil erosion, in order to maintain soil health and productivity. © 2015 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

  2. Uncertainties in assessing tillage erosion - How appropriate are our measuring techniques?

    Science.gov (United States)

    Fiener, P.; Wilken, F.; Aldana-Jague, E.; Deumlich, D.; Gómez, J. A.; Guzmán, G.; Hardy, R. A.; Quinton, J. N.; Sommer, M.; Van Oost, K.; Wexler, R.

    2018-03-01

    Tillage erosion on arable land is a very important process leading to a net downslope movement of soil and soil constitutes. Tillage erosion rates are commonly in the same order of magnitude as water erosion rates and can be even higher, especially under highly mechanized agricultural soil management. Despite its prevalence and magnitude, tillage erosion is still understudied compared to water erosion. The goal of this study was to bring together experts using different techniques to determine tillage erosion and use the different results to discuss and quantify uncertainties associated with tillage erosion measurements. The study was performed in northeastern Germany on a 10 m by 50 m plot with a mean slope of 8%. Tillage erosion was determined after two sequences of seven tillage operations. Two different micro-tracers (magnetic iron oxide mixed with soil and fluorescent sand) and one macro-tracer (passive radio-frequency identification transponders (RFIDs), size: 4 × 22 mm) were used to directly determine soil fluxes. Moreover, tillage induced changes in topography were measured for the entire plot with two different terrestrial laser scanners and an unmanned aerial system for structure from motion topography analysis. Based on these elevation differences, corresponding soil fluxes were calculated. The mean translocation distance of all techniques was 0.57 m per tillage pass, with a relatively wide range of mean soil translocation distances ranging from 0.39 to 0.72 m per pass. A benchmark technique could not be identified as all used techniques have individual error sources, which could not be quantified. However, the translocation distances of the macro-tracers used were consistently smaller than the translocation distances of the micro-tracers (mean difference = - 26 ± 12%), which questions the widely used assumption of non-selective soil transport via tillage operations. This study points out that tillage erosion measurements, carried out under almost

  3. Response of Muddy Sediments and Benthic Diatom-based Biofilms to Repeated Erosion Events

    Science.gov (United States)

    Valentine, K.; Mariotti, G.; Fagherazzi, S.

    2016-02-01

    Benthic biofilms, microbes aggregated within a matrix of Extracellular Polymeric Substances (EPS), are commonly found in shallow coastal areas and intertidal environments. Biofilms have the potential to stabilize sediments, hence reducing erosion and possibly mitigating land loss. The purpose of this study is to determine how repeated flow events that rework the bed affect biofilm growth and its ability to stabilize cohesive sediments. Natural mud devoid of grazers was used to create placed beds in four annular flumes; biofilms were allowed to grow on the sediment surface. Each flume was eroded at different time intervals (1 or 12 days) to allow for varied levels of biofilm growth and adjustment following erosion. In addition, experiments with abiotic mud were performed by adding bleach to the tank. Each erosion test consisted of step-wise increases in flow that were used to measured erodibility. In the experiments where the bed was eroded every day both the abiotic and biotic flumes exhibited a decrease in erodibility with time, likely due to consolidation, but the decrease in erodibility was greater in the flume with a biofilm. Specifically the presence of biofilm reduced bed erosion at low shear stresses ( 0.1 Pa). We attribute this progressive decrease in erodibility to the accumulation of EPS over time: even though the biofilm was eroded during each erosion event, the EPS was retained within the flume, mixed with the eroded sediment and eventually settled. Less frequent erosion allowed the growth of a stronger biofilm that decreased bed erosion at higher shear stresses ( 0.4 Pa). We conclude that the time between destructive flow events influences the ability of biofilms to stabilize sediments. This influence will likely be affected by biofilm growth conditions such as light, temperature, nutrients, salinity, and the microbial community.

  4. Monthly Rainfall Erosivity Assessment for Switzerland

    Science.gov (United States)

    Schmidt, Simon; Meusburger, Katrin; Alewell, Christine

    2016-04-01

    Water erosion is crucially controlled by rainfall erosivity, which is quantified out of the kinetic energy of raindrop impact and associated surface runoff. Rainfall erosivity is often expressed as the R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). Just like precipitation, the rainfall erosivity of Switzerland has a characteristic seasonal dynamic throughout the year. This inter-annual variability is to be assessed by a monthly and seasonal modelling approach. We used a network of 86 precipitation gauging stations with a 10-minute temporal resolution to calculate long-term average monthly R-factors. Stepwise regression and Monte Carlo Cross Validation (MCCV) was used to select spatial covariates to explain the spatial pattern of R-factor for each month across Switzerland. The regionalized monthly R-factor is mapped by its individual regression equation and the ordinary kriging interpolation of its residuals (Regression-Kriging). As covariates, a variety of precipitation indicator data has been included like snow height, a combination of hourly gauging measurements and radar observations (CombiPrecip), mean monthly alpine precipitation (EURO4M-APGD) and monthly precipitation sums (Rhires). Topographic parameters were also significant explanatory variables for single months. The comparison of all 12 monthly rainfall erosivity maps showed seasonality with highest rainfall erosivity in summer (June, July, and August) and lowest rainfall erosivity in winter months. Besides the inter-annual temporal regime, a seasonal spatial variability was detectable. Spatial maps of monthly rainfall erosivity are presented for the first time for Switzerland. The assessment of the spatial and temporal dynamic behaviour of the R-factor is valuable for the identification of more susceptible seasons and regions as well as for the application of selective erosion control measures. A combination with monthly vegetation

  5. Microbial micropatches within microbial hotspots

    Science.gov (United States)

    Smith, Renee J.; Tobe, Shanan S.; Paterson, James S.; Seymour, Justin R.; Oliver, Rod L.; Mitchell, James G.

    2018-01-01

    The spatial distributions of organism abundance and diversity are often heterogeneous. This includes the sub-centimetre distributions of microbes, which have ‘hotspots’ of high abundance, and ‘coldspots’ of low abundance. Previously we showed that 300 μl abundance hotspots, coldspots and background regions were distinct at all taxonomic levels. Here we build on these results by showing taxonomic micropatches within these 300 μl microscale hotspots, coldspots and background regions at the 1 μl scale. This heterogeneity among 1 μl subsamples was driven by heightened abundance of specific genera. The micropatches were most pronounced within hotspots. Micropatches were dominated by Pseudomonas, Bacteroides, Parasporobacterium and Lachnospiraceae incertae sedis, with Pseudomonas and Bacteroides being responsible for a shift in the most dominant genera in individual hotspot subsamples, representing up to 80.6% and 47.3% average abundance, respectively. The presence of these micropatches implies the ability these groups have to create, establish themselves in, or exploit heterogeneous microenvironments. These genera are often particle-associated, from which we infer that these micropatches are evidence for sub-millimetre aggregates and the aquatic polymer matrix. These findings support the emerging paradigm that the microscale distributions of planktonic microbes are numerically and taxonomically heterogeneous at scales of millimetres and less. We show that microscale microbial hotspots have internal structure within which specific local nutrient exchanges and cellular interactions might occur. PMID:29787564

  6. Rainfall erosivity in Brazil: A Review

    Science.gov (United States)

    In this paper, we review the erosivity studies conducted in Brazil to verify the quality and representativeness of the results generated and to provide a greater understanding of the rainfall erosivity (R-factor) in Brazil. We searched the ISI Web of Science, Scopus, SciELO, and Google Scholar datab...

  7. Soil erosion dynamics response to landscape pattern

    NARCIS (Netherlands)

    Ouyang, W.; Skidmore, A.K.; Hao, F.; Wang, T.

    2010-01-01

    Simulating soil erosion variation with a temporal land use database reveals long-term fluctuations in landscape patterns, as well as priority needs for soil erosion conservation. The application of a multi-year land use database in support of a Soil Water Assessment Tool (SWAT) led to an accurate

  8. Reduction of soil erosion on forest roads

    Science.gov (United States)

    Edward R. Burroughs; John G. King

    1989-01-01

    Presents the expected reduction in surface erosion from selected treatments applied to forest road traveledways, cutslopes, fillslopes, and ditches. Estimated erosion reduction is expressed as functions of ground cover, slope gradient, and soil properties whenever possible. A procedure is provided to select rock riprap size for protection of the road ditch.

  9. Forest road erosion control using multiobjective optimization

    Science.gov (United States)

    Matthew Thompson; John Sessions; Kevin Boston; Arne Skaugset; David Tomberlin

    2010-01-01

    Forest roads are associated with accelerated erosion and can be a major source of sediment delivery to streams, which can degrade aquatic habitat. Controlling road-related erosion therefore remains an important issue for forest stewardship. Managers are faced with the task to develop efficient road management strategies to achieve conflicting environmental and economic...

  10. Past, Present, Future Erosion at Locke Island

    Energy Technology Data Exchange (ETDEWEB)

    Bjornstad, Bruce N.

    2006-08-08

    This report describes and documents the erosion that has occurred along the northeast side of Locke Island over the last 10 to 20 years. The principal cause of this erosion is the massive Locke Island landslide complex opposite the Columbia River along the White Bluffs, which constricts the flow of the river and deflects the river's thalweg southward against the island.

  11. Tools for Ephemeral Gully Erosion Process Research

    Science.gov (United States)

    Techniques to quantify ephemeral gully erosion have been identified by USDA Natural Resources Conservation Service (NRCS) as one of gaps in current erosion assessment tools. One reason that may have contributed to this technology gap is the difficulty to quantify changes in channel geometry to asses...

  12. Developing empirical relationship between interrill erosion, rainfall ...

    African Journals Online (AJOL)

    In order to develop an empirical relationship for interrill erosion based on rainfall intensity, slope steepness and soil types, an interrill erosion experiment was conducted using laboratory rainfall simulator on three soil types (Vertisols, Cambisols and Leptosols) for the highlands of North Shewa Zone of Oromia Region.

  13. Rethinking erosion on Java: a reaction

    NARCIS (Netherlands)

    Graaff, de J.; Wiersum, K.F.

    1992-01-01

    In a recent article (Diemont et al., 1991) about erosion on Java, it has been postulated that low inputs, not surface erosion, is the main cause of low productivity of upland food crops on this island. In this article it is argued that this hypothesis is too simple. An analysis of empirical field

  14. The erosive potential of candy sprays

    NARCIS (Netherlands)

    Gambon, D.L.; Brand, H.S.; Nieuw Amerongen, A.V.

    2009-01-01

    Objective To determine the erosive potential of seven different commercially available candy sprays in vitro and in vivo. Material and methods The erosive potential was determined in vitro by measuring the pH and neutralisable acidity. The salivary pH and flow rate were measured in healthy

  15. Dental erosion: prevalence, incidence, and distribution

    NARCIS (Netherlands)

    Jager, D.H.J.; Amaechi, B.T.

    2015-01-01

    Dental erosion is one of the most common dental diseases and it is a growing problem. Numerous epidemiological studies have investigated the prevalence of dental erosion. For these studies different cross sections of the population are investigated. Large differences were found between countries,

  16. Backward erosion piping : Initiation and progression

    NARCIS (Netherlands)

    Van Beek, V.M.

    2015-01-01

    Backward erosion piping is an internal erosion mechanism during which shallow pipes are formed in the direction opposite to the flow underneath water-retaining structures as a result of the gradual removal of sandy material by the action of water. It is an important failure mechanism in both dikes

  17. Numerical modelling of the erosion and deposition of sand inside a filter layer

    DEFF Research Database (Denmark)

    Jacobsen, Niels Gjøl; van Gent, Marcel R. A.; Fredsøe, Jørgen

    2017-01-01

    This paper treats the numerical modelling of the behaviour of a sand core covered by rocks and exposed to waves. The associated displacement of the rock is also studied. A design that allows for erosion and deposition of the sand core beneath a rock layer in a coastal structure requires an accurate...... prediction method to assure that the amount of erosion remains within acceptable limits. This work presents a numerical model that is capable of describing the erosion and deposition patterns inside of an open filter of rock on top of sand. The hydraulic loading is that of incident irregular waves...... and the open filters are surface piercing. Due to the few experimental data sets on sediment transport inside of rock layers, a sediment transport formulation has been proposed based on a matching between the numerical model and experimental data on the profile deformation inside an open filter. The rock layer...

  18. Regionalization of monthly rainfall erosivity patternsin Switzerland

    Science.gov (United States)

    Schmidt, Simon; Alewell, Christine; Panagos, Panos; Meusburger, Katrin

    2016-10-01

    One major controlling factor of water erosion is rainfall erosivity, which is quantified as the product of total storm energy and a maximum 30 min intensity (I30). Rainfall erosivity is often expressed as R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). As rainfall erosivity is closely correlated with rainfall amount and intensity, the rainfall erosivity of Switzerland can be expected to have a regional characteristic and seasonal dynamic throughout the year. This intra-annual variability was mapped by a monthly modeling approach to assess simultaneously spatial and monthly patterns of rainfall erosivity. So far only national seasonal means and regional annual means exist for Switzerland. We used a network of 87 precipitation gauging stations with a 10 min temporal resolution to calculate long-term monthly mean R-factors. Stepwise generalized linear regression (GLM) and leave-one-out cross-validation (LOOCV) were used to select spatial covariates which explain the spatial and temporal patterns of the R-factor for each month across Switzerland. The monthly R-factor is mapped by summarizing the predicted R-factor of the regression equation and the corresponding residues of the regression, which are interpolated by ordinary kriging (regression-kriging). As spatial covariates, a variety of precipitation indicator data has been included such as snow depths, a combination product of hourly precipitation measurements and radar observations (CombiPrecip), daily Alpine precipitation (EURO4M-APGD), and monthly precipitation sums (RhiresM). Topographic parameters (elevation, slope) were also significant explanatory variables for single months. The comparison of the 12 monthly rainfall erosivity maps showed a distinct seasonality with the highest rainfall erosivity in summer (June, July, and August) influenced by intense rainfall events. Winter months have the lowest rainfall erosivity. A proportion of 62 % of

  19. Erosion testing of hard materials and coatings

    Energy Technology Data Exchange (ETDEWEB)

    Hawk, Jeffrey A.

    2005-04-29

    Erosion is the process by which unconstrained particles, usually hard, impact a surface, creating damage that leads to material removal and component failure. These particles are usually very small and entrained in fluid of some type, typically air. The damage that occurs as a result of erosion depends on the size of the particles, their physical characteristics, the velocity of the particle/fluid stream, and their angle of impact on the surface of interest. This talk will discuss the basics of jet erosion testing of hard materials, composites and coatings. The standard test methods will be discussed as well as alternative approaches to determining the erosion rate of materials. The damage that occurs will be characterized in genera1 terms, and examples will be presented for the erosion behavior of hard materials and coatings (both thick and thin).

  20. Modelling rainfall erosion resulting from climate change

    Science.gov (United States)

    Kinnell, Peter

    2016-04-01

    It is well known that soil erosion leads to agricultural productivity decline and contributes to water quality decline. The current widely used models for determining soil erosion for management purposes in agriculture focus on long term (~20 years) average annual soil loss and are not well suited to determining variations that occur over short timespans and as a result of climate change. Soil loss resulting from rainfall erosion is directly dependent on the product of runoff and sediment concentration both of which are likely to be influenced by climate change. This presentation demonstrates the capacity of models like the USLE, USLE-M and WEPP to predict variations in runoff and erosion associated with rainfall events eroding bare fallow plots in the USA with a view to modelling rainfall erosion in areas subject to climate change.

  1. Erosion Pressure on the Danish Coasts

    DEFF Research Database (Denmark)

    Sørensen, Carlo Sass; Sørensen, Per; Kroon, Aart

    Coastlines around the world are receding due to coastal erosion.With rising sea levels and a potential climatic deterioration due to climate change, erosion rates are likely to increase at many locations in the future.Together with the current preference of people to settle near or directly...... by the ocean, coastal erosion issues become increasingly more important to the human values at risk. Along many Danish coastlines, hard structures already act as coastal protection in the form of groins, breakwaters, revetments etc. These eroding coasts however still lack sand and where the public, in general......, neglects the need for sand replenishment i.e. in the form of repeated sand nourishments. Here we present a conceptual model and method for dividing coastal erosion into acute and chronic erosion pressure, respectively. We focus on the model use for management and climate change adaptation purposes...

  2. Dietary assessment and counseling for dental erosion.

    Science.gov (United States)

    Marshall, Teresa A

    2018-02-01

    Dental erosion occurs after exposure to intrinsic or extrinsic acids. Exposure to intrinsic gastrointestinal acids is associated with anorexia nervosa, bulimia nervosa, rumination syndrome, or gastroesophageal reflux. Extrinsic dietary acids from foods or beverages also can cause erosion, particularly when exposure is prolonged by holding or swishing behaviors. Clinicians should screen patients exhibiting dental erosion for anorexia nervosa, bulimia nervosa, rumination syndrome, and gastroesophageal reflux disease. Clinicians should screen patients without a medical explanation for their erosion for exposure to acidic foods and beverages, particularly for habits that prolong exposure. Identification of intrinsic and extrinsic acid exposures and recommendations to minimize exposures are important to prevent erosion and maintain oral health. Copyright © 2018 American Dental Association. Published by Elsevier Inc. All rights reserved.

  3. Medication-related dental erosion: a review.

    Science.gov (United States)

    Thomas, Manuel S; Vivekananda Pai, A R; Yadav, Amit

    2015-10-01

    Dental erosion has become a major problem that affects the long-term health of the dentition. Among the various potential causes for erosive tooth wear, the different drugs prescribed for patients may be overlooked. Several therapeutic medications can directly or indirectly be associated with dental erosion. It is the responsibility of oral health providers to make both patients and colleagues aware of drugs that may contribute to this condition. Therefore, the purpose of this discussion is to provide an overview of the various therapeutic medications that can be related to tooth erosion. The authors also include precautionary measures-summarized as The 9 Rs-to avoid or at least reduce medication-induced erosion.

  4. Communicating and Visualizing Erosion-associated Risks to Infrastructure

    Science.gov (United States)

    Hewett, Caspar; Simpson, Carolyn; Wainwright, John

    2016-04-01

    Soil erosion is a major problem worldwide, affecting agriculture, the natural environment and urban areas through its impact on flood risk, water quality, loss of nutrient-rich upper soil layers, eutrophication of water bodies, sedimentation of waterways and sediment-related damage to roads, buildings and infrastructure such as water, gas and electricity supply networks. This study focuses on risks to infrastructure associated with erosion and the interventions needed to reduce those risks. Deciding on what interventions to make means understanding better which parts of the landscape are most susceptible to erosion and which measures are most effective in reducing it. Effective ways of communicating mitigation strategies to stakeholders such as farmers, land managers and policy-makers are then essential if interventions are to be implemented. Drawing on the Decision-Support Matrix (DSM) approach which combines a set of hydrological principles with Participatory Action Research (PAR), a decision-support tool for Communicating and Visualizing Erosion-Associated Risks to Infrastructure (CAVERTI) was developed. The participatory component was developed with the Wear Rivers Trust, focusing on a case-study area in the North East of England. The CAVERTI tool brings together process understanding gained from modelling with knowledge and experience of a variety of stakeholders to address directly the problem of sediment transport. Development of the tool was a collaborative venture, ensuring that the problems and solutions presented are easily recognised by practitioners and decision-makers. This recognition, and ease of access via a web-based interface, in turn help to ensure that the tools get used. The web-based tool developed helps to assess, manage and improve understanding of risk from a multi-stakeholder perspective and proposes solutions to problems. We argue that visualization and communication tools co-developed by researchers and stakeholders are the best means

  5. Soil erosion processes on sloping land using REE tracer

    International Nuclear Information System (INIS)

    Shen Zhenzhou; Liu Puling; Yang Mingyi; Lian Zhenlong; Ju Tongjun; Yao Wenyi; Li Mian

    2007-01-01

    Sheet erosion is the main performance in the slope soil erosion process at the primary stage of natural rainfall. For three times of rainfall during experiment, the ratios of sheet erosion to total erosion account for 71%, 48% and 49% respectively, which showed that the sloping erosion was still at the primary stage from sheet erosion to rill erosion. With the rainfall going, the rill erosion amount increase. It showed that soil erosion was changing from sheet erosion to rill erosion. The sources of sediment from different sections of the plot were analyzed, and the results indicated that whatever the sheet erosion changed, the ratio erosion of upper part of surface soil was always lower than 10%. Sheet erosion came mainly from the lower section of surface soil. With the ratios to the amount of total rill erosion changes, the rill erosion amount of each section regularly changes too. The general conclusion is that when the rainfall ends, relative erosion of different slope element to the foot of slope is: 1 meter away accounts for 16%, 2-4 meters away is 6% and 5-9 meters away is 3%. The ratio of rill erosion amount of these three slope element is 5:2:1, which shows the rill erosion amount are mainly from the slope element of 4 meters from the foot of slope. (authors)

  6. A Workflow to Model Microbial Loadings in Watersheds

    Science.gov (United States)

    Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated wit...

  7. A Workflow to Model Microbial Loadings in Watersheds (proceedings)

    Science.gov (United States)

    Many watershed models simulate overland and instream microbial fate and transport, but few actually provide loading rates on land surfaces and point sources to the water body network. This paper describes the underlying general equations for microbial loading rates associated wit...

  8. Reductive immobilization of U(VI) in Fe(III) oxide-reducing subsurface sediments: Analysis of coupled microbial-geochemical processes in experimental reactive transport systems. Final Scientific/Technical Report-EMSP 73914

    International Nuclear Information System (INIS)

    Eric E. Roden Matilde M. Urrutia Mark O. Barnett Clifford R. Lange

    2005-01-01

    The purpose of this research was to provide information to DOE on microbiological and geochemical processes underlying the potential use of dissimilatory metal-reducing bacteria (DMRB) to create subsurface redox barriers for immobilization of uranium and other redox-sensitive metal/radionuclide contaminants that were released to the environment in large quantities during Cold War nuclear weapons manufacturing operations. Several fundamental scientific questions were addressed in order to understand and predict how such treatment procedures would function under in situ conditions in the subsurface. These questions revolved the coupled microbial-geochemical phenomena which are likely to occur within a redox barrier treatment zone, and on the dynamic interactions between hydrologic flux and biogeochemical process rates. First, we assembled a robust conceptual understanding and numerical framework for modeling the kinetics of microbial Fe(III) oxide reduction and associated DMRB growth in sediments. Development of this framework is a critical prerequisite for predicting the potential effectiveness of DMRB-promoted subsurface bioremediation, since Fe(III) oxides are expected to be the primary source of electron-accepting capacity for growth and maintenance of DMRB in subsurface environments. We also defined in detail the kinetics of microbial (enzymatic) versus abiotic, ferrous iron-promoted reduction of U(VI) in the presence and absence of synthetic and natural Fe(III) oxide materials. The results of these studies suggest that (i) the efficiency of dissolved U(VI) scavenging may be influenced by the kinetics of enzymatic U(VI) reduction in systems with relative short fluid residence times; (2) association of U(VI) with diverse surface sites in natural soils and sediments has the potential to limit the rate and extent of microbial U(VI) reduction, and in turn modulate the effectiveness of in situ U(VI) bioremediation; and (3) abiotic, ferrous iron (Fe(II)) drive n U

  9. Microbial Enzymatic Degradation of Biodegradable Plastics.

    Science.gov (United States)

    Roohi; Bano, Kulsoom; Kuddus, Mohammed; Zaheer, Mohammed R; Zia, Qamar; Khan, Mohammed F; Ashraf, Ghulam Md; Gupta, Anamika; Aliev, Gjumrakch

    2017-01-01

    The renewable feedstock derived biodegradable plastics are important in various industries such as packaging, agricultural, paper coating, garbage bags and biomedical implants. The increasing water and waste pollution due to the available decomposition methods of plastic degradation have led to the emergence of biodegradable plastics and biological degradation with microbial (bacteria and fungi) extracellular enzymes. The microbes utilize biodegradable polymers as the substrate under starvation and in unavailability of microbial nutrients. Microbial enzymatic degradation is suitable from bioremediation point of view as no waste accumulation occurs. It is important to understand the microbial interaction and mechanism involved in the enzymatic degradation of biodegradable plastics under the influence of several environmental factors such as applied pH, thermo-stability, substrate molecular weight and/or complexity. To study the surface erosion of polymer film is another approach for hydrolytic degradation characteristion. The degradation of biopolymer is associated with the production of low molecular weight monomer and generation of carbon dioxide, methane and water molecule. This review reported the degradation study of various existing biodegradable plastics along with the potent degrading microbes (bacteria and fungi). Patents available on plastic biodegradation with biotechnological significance is also summarized in this paper. This paper assesses that new disposal technique should be adopted for the degradation of polymers and further research is required for the economical production of biodegradable plastics along with their enzymatic degradation. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  10. Erosion resistance comparison of alternative surface treatments

    Science.gov (United States)

    Česánek, Z.; Schubert, J.; Houdková, Š.

    2017-05-01

    Erosion is a process characterized by the particle separation and the damage of component functional surfaces. Thermal spraying technology HP/HVOF (High Pressure / High Velocity Oxygen Fuel) is commonly used for protection of component surfaces against erosive wear. Alloy as well as cermet based coatings meet the requirements for high erosion resistance. Wear resistance is in many cases the determining property of required component functioning. The application suitability of coating materials is particularly influenced by different hardness. This paper therefore presents an erosion resistance comparison of alloy and cermet based coatings. The coatings were applied on steel substrates and were subjected to the erosive test using the device for evaluation of material erosion resistance working on the principle of centrifugal erodent flow. Abrasive sand Al2O3 with grain size 212-250 μm was selected as an erosive material. For this purpose, the specimens were prepared by thermal spraying technology HP/HVOF using commercially available powders Stellite 6, NiCrBSi, Cr3C2-25%NiCr, Cr3C2-25%CoNiCrAlY, Hastelloy C-276 and experimental coating TiMoCN-29% Ni. Erosion resistance of evaluated coatings was compared with erosive resistance of 1.4923 high alloyed steel without nitridation and in nitrided state and further with surface treatment using technology PVD. According to the evaluation, the resulting erosive resistance depends not only on the selected erodent and surface protection, but also on the erodent impact angle.

  11. Dynamic Analysis of Soil Erosion in Songhua River Watershed

    Science.gov (United States)

    Zhang, Yujuan; Li, Xiuhai; Wang, Qiang; Liu, Jiang; Liang, Xin; Li, Dan; Ni, Chundi; Liu, Yan

    2018-01-01

    In this paper, based on RS and GIS technology and Revised Universal Soil Loss Equation (RUSLE), the soil erosion dynamic changes during the two periods of 1990 and 2010 in Bin County was analyzed by using the Landsat TM data of the two periods, so as to reveal the soil erosion spatial distribution pattern and spatial and temporal dynamic evolution rule in the region. The results showed that: the overall patterns of soil erosion were basically the same in both periods, mainly featuring slight erosion and mild erosion, with the area proportions of 80.68% and 74.71% respectively. The slight and extremely intensive erosion changing rates showed a narrowing trend; mild, moderate and intensive erosion was increasing, with a trend of increased soil erosion; mild and intensive erosion were developing towards moderate erosion and moderate and extremely intensive erosion were progressing towards intensive erosion.

  12. Soil erosion and sediment yield and their relationships with vegetation cover in upper stream of the Yellow River.

    Science.gov (United States)

    Ouyang, Wei; Hao, Fanghua; Skidmore, Andrew K; Toxopeus, A G

    2010-12-15

    Soil erosion is a significant concern when considering regional environmental protection, especially in the Yellow River Basin in China. This study evaluated the temporal-spatial interaction of land cover status with soil erosion characteristics in the Longliu Catchment of China, using the Soil and Water Assessment Tool (SWAT) model. SWAT is a physical hydrological model which uses the RUSLE equation as a sediment algorithm. Considering the spatial and temporal scale of the relationship between soil erosion and sediment yield, simulations were undertaken at monthly and annual temporal scales and basin and sub-basin spatial scales. The corresponding temporal and spatial Normalized Difference Vegetation Index (NDVI) information was summarized from MODIS data, which can integrate regional land cover and climatic features. The SWAT simulation revealed that the annual soil erosion and sediment yield showed similar spatial distribution patterns, but the monthly variation fluctuated significantly. The monthly basin soil erosion varied from almost no erosion load to 3.92 t/ha and the maximum monthly sediment yield was 47,540 tones. The inter-annual simulation focused on the spatial difference and relationship with the corresponding vegetation NDVI value for every sub-basin. It is concluded that, for this continental monsoon climate basin, the higher NDVI vegetation zones prevented sediment transport, but at the same time they also contributed considerable soil erosion. The monthly basin soil erosion and sediment yield both correlated with NDVI, and the determination coefficients of their exponential correlation model were 0.446 and 0.426, respectively. The relationships between soil erosion and sediment yield with vegetation NDVI indicated that the vegetation status has a significant impact on sediment formation and transport. The findings can be used to develop soil erosion conservation programs for the study area. Copyright © 2010 Elsevier B.V. All rights reserved.

  13. Predicted erosion and sediment delivery of fallout plutonium

    International Nuclear Information System (INIS)

    Foster, G.R.; Hakonson, T.E.

    1984-01-01

    Plutonium (Pu) from fallout after atmospheric explosion of nuclear weapons in the 1950s and 1960s is being redistributed over the landscape by soil erosion and carried on sediment by streams to oceans. Erosion rates computed with the Universal Soil Loss Equation for about 200,000 sample points on nonfederal land across the US were used to estimate Pu removal rates by soil erosion by water, Pu delivery in several major rivers, and concentration of Pu on the transported sediment. Estimates of average annual Pu delivery on sediment ranged from 0.002% of the initial fallout Pu inventory for the Savannah River basin to 0.08% for the Mississippi River basin. If the deposition of Pu had been uniformly 37 Bq/m 2 , the estimated Pu activity on suspended sediment ranged from about 0.26 Bq/kg of sediment for the Savannah River basin to 0.52 Bq/kg for the Columbia and Rio Grande river basins. After 1000 yr, about 9 to 48% of the initial Pu inventory will remain in US soils that are eroding. Much of the Pu on eroded sediment will travel only a short distance from its origin before its host sediment particles are deposited and permanently located, at least for a few hundred years. As much as 90% of the initially deposited Pu will remain, redistributed over the landscape by erosion and deposition. Although the delivery rate of Pu by rivers will not decrease greatly in the next 100 yr, a significant decrease will likely occur by 1000 yr

  14. Synthesis study of an erosion hot spot, Ocean Beach, California

    Science.gov (United States)

    Barnard, Patrick L.; Hansen, Jeff E.; Erikson, Li H.

    2012-01-01

    A synthesis of multiple coastal morphodynamic research efforts is presented to identify the processes responsible for persistent erosion along a 1-km segment of 7-km-long Ocean Beach in San Francisco, California. The beach is situated adjacent to a major tidal inlet and in the shadow of the ebb-tidal delta at the mouth of San Francisco Bay. Ocean Beach is exposed to a high-energy wave climate and significant alongshore variability in forcing introduced by varying nearshore bathymetry, tidal forcing, and beach morphology (e.g., beach variably backed by seawall, dunes, and bluffs). In addition, significant regional anthropogenic factors have influenced sediment supply and tidal current strength. A variety of techniques were employed to investigate the erosion at Ocean Beach, including historical shoreline and bathymetric analysis, monthly beach topographic surveys, nearshore and regional bathymetric surveys, beach and nearshore grain size analysis, two surf-zone hydrodynamic experiments, four sets of nearshore wave and current experiments, and several numerical modeling approaches. Here, we synthesize the results of 7 years of data collection to lay out the causes of persistent erosion, demonstrating the effectiveness of integrating an array of data sets covering a huge range of spatial scales. The key findings are as follows: anthropogenic influences have reduced sediment supply from San Francisco Bay, leading to pervasive contraction (i.e., both volume and area loss) of the ebb-tidal delta, which in turn reduced the regional grain size and modified wave focusing patterns along Ocean Beach, altering nearshore circulation and sediment transport patterns. In addition, scour associated with an exposed sewage outfall pipe causes a local depression in wave heights, significantly modifying nearshore circulation patterns that have been shown through modeling to be key drivers of persistent erosion in that area.

  15. Microbial activity at Yucca Mountain

    International Nuclear Information System (INIS)

    Horn, J.M.; Meike, A.

    1995-01-01

    The U.S. Department of Energy is engaged in a suitability study for a potential geological repository at Yucca Mountain, Nevada, for the containment and storage of commercially generated spent fuel and defense high-level nuclear waste. There is growing recognition of the role that biotic factors could play in this repository, either directly through microbially induced corrosion (MIC), or indirectly by altering the chemical environment or contributing to the transport of radionuclides. As a first step toward describing and predicting these processes, a workshop was held on April 10-12, 1995, in Lafayette, California. The immediate aims of the workshop were: (1) To identify microbially related processes relevant to the design of a radioactive waste repository under conditions similar to those at Yucca Mountain. (2) To determine parameters that are critical to the evaluation of a disturbed subterranean environment. (3) To define the most effective means of investigating the factors thus identified

  16. Microbial activity at Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Horn, J.M.; Meike, A.

    1995-09-25

    The U.S. Department of Energy is engaged in a suitability study for a potential geological repository at Yucca Mountain, Nevada, for the containment and storage of commercially generated spent fuel and defense high-level nuclear waste. There is growing recognition of the role that biotic factors could play in this repository, either directly through microbially induced corrosion (MIC), or indirectly by altering the chemical environment or contributing to the transport of radionuclides. As a first step toward describing and predicting these processes, a workshop was held on April 10-12, 1995, in Lafayette, California. The immediate aims of the workshop were: (1) To identify microbially related processes relevant to the design of a radioactive waste repository under conditions similar to those at Yucca Mountain. (2) To determine parameters that are critical to the evaluation of a disturbed subterranean environment. (3) To define the most effective means of investigating the factors thus identified.

  17. Mapping monthly rainfall erosivity in Europe.

    Science.gov (United States)

    Ballabio, Cristiano; Borrelli, Pasquale; Spinoni, Jonathan; Meusburger, Katrin; Michaelides, Silas; Beguería, Santiago; Klik, Andreas; Petan, Sašo; Janeček, Miloslav; Olsen, Preben; Aalto, Juha; Lakatos, Mónika; Rymszewicz, Anna; Dumitrescu, Alexandru; Tadić, Melita Perčec; Diodato, Nazzareno; Kostalova, Julia; Rousseva, Svetla; Banasik, Kazimierz; Alewell, Christine; Panagos, Panos

    2017-02-01

    Rainfall erosivity as a dynamic factor of soil loss by water erosion is modelled intra-annually for the first time at European scale. The development of Rainfall Erosivity Database at European Scale (REDES) and its 2015 update with the extension to monthly component allowed to develop monthly and seasonal R-factor maps and assess rainfall erosivity both spatially and temporally. During winter months, significant rainfall erosivity is present only in part of the Mediterranean countries. A sudden increase of erosivity occurs in major part of European Union (except Mediterranean basin, western part of Britain and Ireland) in May and the highest values are registered during summer months. Starting from September, R-factor has a decreasing trend. The mean rainfall erosivity in summer is almost 4 times higher (315MJmmha -1 h -1 ) compared to winter (87MJmmha -1 h -1 ). The Cubist model has been selected among various statistical models to perform the spatial interpolation due to its excellent performance, ability to model non-linearity and interpretability. The monthly prediction is an order more difficult than the annual one as it is limited by the number of covariates and, for consistency, the sum of all months has to be close to annual erosivity. The performance of the Cubist models proved to be generally high, resulting in R 2 values between 0.40 and 0.64 in cross-validation. The obtained months show an increasing trend of erosivity occurring from winter to summer starting from western to Eastern Europe. The maps also show a clear delineation of areas with different erosivity seasonal patterns, whose spatial outline was evidenced by cluster analysis. The monthly erosivity maps can be used to develop composite indicators that map both intra-annual variability and concentration of erosive events. Consequently, spatio-temporal mapping of rainfall erosivity permits to identify the months and the areas with highest risk of soil loss where conservation measures should be

  18. Control of eolic erosion in a coal Port, by means of re-vegetation of arid areas and operational procedures

    International Nuclear Information System (INIS)

    Velasquez Pilar

    1992-01-01

    To the phenomenon of haulage of floor particles for the wind is known as erosion by deflation, and one in the ways of eolic erosion existent, although many authors constitutes they refer to her as eolic erosion. The eolic erosion includes the movement processes, transport, separation and deposition, it can present in any area that presents the following conditions: 1) Soil dry and loose until certain finely divided degree, 2) flat surface with little or any vegetable cover, 3) quite extensive land 4) sufficiently strong wind to transport the earth particles. It is considered that to begin the movement of particles 0.1 mm of diameter winds they are needed to 30 cm of height of 4,4m/s (FAO, 1961). All these conditions are presented in Port Bolivar in more or smaller measure. In port Bolivar two main groups of areas have been identified in process of material movement

  19. A review of concentrated flow erosion processes on rangelands: fundamental understanding and knowledge gaps

    Science.gov (United States)

    Concentrated flow erosion processes are distinguished from splash and sheetflow processes in their enhanced ability to mobilize and transport large amounts of soil, water and dissolved elements. On rangelands, soil, nutrients and water are scarce and only narrow margins of resource losses are tolera...

  20. Soil aggregation and the stabilization of organic carbon as affected by erosion and deposition

    NARCIS (Netherlands)

    Wang, X.; Cammeraat, E.L.H.; Cerli, C.; Kalbitz, K.

    2014-01-01

    The importance of soil aggregation in determining the dynamics of soil organic carbon (SOC) during erosion, transportation and deposition is poorly understood. Particularly, we do not know how aggregation contributes to the often-observed accumulation of SOC at depositional sites. Our objective was

  1. How does soil erosion influence the terrestrial carbon cycle and the impacts of land use and land cover change?

    Science.gov (United States)

    Naipal, V.; Wang, Y.; Ciais, P.; Guenet, B.; Lauerwald, R.

    2017-12-01

    The onset of agriculture has accelerated soil erosion rates significantly, mobilizing vast quantities of soil organic carbon (SOC) globally. Studies show that at timescales of decennia to millennia this mobilized SOC can significantly alter previously estimated carbon emissions from land use and land cover change (LULCC). However, a full understanding of the impact of soil erosion on land-atmosphere carbon exchange is still missing. The aim of our study is to better constrain the terrestrial carbon fluxes by developing methods, which are compatible with earth system models (ESMs), and explicitly represent the links between soil erosion and carbon dynamics. For this we use an emulator that represents the carbon cycle of ORCHIDEE, which is the land component of the IPSL ESM, in combination with an adjusted version of the Revised Universal Soil Loss Equation (RUSLE) model. We applied this modeling framework at the global scale to evaluate how soil erosion influenced the terrestrial carbon cycle in the presence of elevated CO2, regional climate change and land use change. Here, we focus on the effects of soil detachment by erosion only and do not consider sediment transport and deposition. We found that including soil erosion in the SOC dynamics-scheme resulted in two times more SOC being lost during the historical period (1850-2005 AD). LULCC is the main contributor to this SOC loss, whose impact on the SOC stocks is significantly amplified by erosion. Regionally, the influence of soil erosion varies significantly, depending on the magnitude of the perturbations to the carbon cycle and the effects of LULCC and climate change on soil erosion rates. We conclude that it is necessary to include soil erosion in assessments of LULCC, and to explicitly consider the effects of elevated CO2 and climate change on the carbon cycle and on soil erosion, for better quantification of past, present, and future LULCC carbon emissions.

  2. Numerical analysis of tungsten erosion and deposition processes under a DEMO divertor plasma

    Directory of Open Access Journals (Sweden)

    Yuki Homma

    2017-08-01

    Full Text Available Erosion reduction of tungsten (W divertor target is one of the most important research subjects for the DEMO fusion reactor design, because the divertor target has to sustain large fluence of incident particles, composed mainly of fuel ions and seeded impurities, during year-long operation period. Rate of net erosion and deposition on outer divertor target has been studied by using the integrated SOL/divertor plasma code SONIC and the kinetic full-orbit impurity transport code IMPGYRO. Two background plasmas have been used: one is lower density ni and higher temperature case and the other is higher ni and lower temperature case. Net erosion has been seen in the lower ni case. But in the higher ni case, the net erosion has been almost suppressed due to increased return rate and reduced self-sputtering yield. Following two factors are important to understand the net erosion formation: (i ratio of the 1st ionization length of sputtered W atom to the Larmor gyro radius of W+ ion, (ii balance between the friction force and the thermal force exerted on W ions. DEMO divertor design should take into account these factors to prevent target erosion.

  3. Process-based coastal erosion modeling for Drew Point (North Slope, Alaska)

    Science.gov (United States)

    Ravens, Thomas M.; Jones, Benjamin M.; Zhang, Jinlin; Arp, Christopher D.; Schmutz, Joel A.

    2012-01-01

    A predictive, coastal erosion/shoreline change model has been developed for a small coastal segment near Drew Point, Beaufort Sea, Alaska. This coastal setting has experienced a dramatic increase in erosion since the early 2000’s. The bluffs at this site are 3-4 m tall and consist of ice-wedge bounded blocks of fine-grained sediments cemented by ice-rich permafrost and capped with a thin organic layer. The bluffs are typically fronted by a narrow (∼ 5  m wide) beach or none at all. During a storm surge, the sea contacts the base of the bluff and a niche is formed through thermal and mechanical erosion. The niche grows both vertically and laterally and eventually undermines the bluff, leading to block failure or collapse. The fallen block is then eroded both thermally and mechanically by waves and currents, which must occur before a new niche forming episode may begin. The erosion model explicitly accounts for and integrates a number of these processes including: (1) storm surge generation resulting from wind and atmospheric forcing, (2) erosional niche growth resulting from wave-induced turbulent heat transfer and sediment transport (using the Kobayashi niche erosion model), and (3) thermal and mechanical erosion of the fallen block. The model was calibrated with historic shoreline change data for one time period (1979-2002), and validated with a later time period (2002-2007).

  4. High-Z material erosion and its control in DIII-D carbon divertor

    Directory of Open Access Journals (Sweden)

    R. Ding

    2017-08-01

    Full Text Available As High-Z materials will likely be used as plasma-facing components (PFCs in future fusion devices, the erosion of high-Z materials is a key issue for high-power, long pulse operation. High-Z material erosion and redeposition have been studied using tungsten and molybdenum coated samples exposed in well-diagnosed DIII-D divertor plasma discharges. By coupling dedicated experiments and modelling using the 3D Monte Carlo code ERO, the roles of sheath potential and background carbon impurities in determining high-Z material erosion are identified. Different methods suggested by modelling have been investigated to control high-Z material erosion in DIII-D experiments. The erosion of Mo and W is found to be strongly suppressed by local injection of methane and deuterium gases. The 13C deposition resulting from local 13CH4 injection also provides information on radial transport due to E ×B drifts and cross field diffusion. Finally, D2 gas puffing is found to cause local plasma perturbation, suppressing W erosion because of the lower effective sputtering yield of W at lower plasma temperature and for higher carbon concentration in the mixed surface layer.

  5. Bioengineering Technology to Control River Soil Erosion using Vetiver (Vetiveria Zizaniodes)

    Science.gov (United States)

    Sriwati, M.; Pallu, S.; Selintung, M.; Lopa, R.

    2018-04-01

    Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock or dissolved material from one location on the earth’s crust, and then transport it away to another location. Bioengineering is an attempt to maximise the use of vegetation components along riverbanks to cope with landslides and erosion of river cliffs and another riverbank damage. This study aims to analyze the bioengineering of Vetiver as a surface layer for soil erosion control using slope of 100, 200, and 300. This study is conducted with 3 variations of rain intensity (I), at 103 mm/hour, 107 mm/hour, and 130 mm/hour by using rainfall simulator tool. In addition, the USLE (Universal Soil Loss Equation) method is used in order to measure the rate of soil erosion. In this study, there are few USLE model parameters were used such as rainfall erosivity factor, soil erodibility factor, length-loss slope and stepness factor, cover management factor, and support practise factor. The results demonstrated that average of reduction of erosion rate using Vetiver, under 3 various rainfalls, namely rainfall intensity 103 mm/hr had reduced 84.971%, rainfall intensity 107 mm/hr had reduced 86.583 %, rainfall intensity 130 mm/hr had reduced 65.851%.

  6. Assessing Vulnerability of Lake Erie Landscapes to Soil Erosion: Modelled and Measured Approaches

    Science.gov (United States)

    Joosse, P.; Laamrani, A.; Feisthauer, N.; Li, S.

    2017-12-01

    Loss of soil from agricultural landscapes to Lake Erie via water erosion is a key transport mechanism for phosphorus bound to soil particles. Agriculture is the dominant land use in the Canadian side of the Lake Erie basin with approximately 75% of the 2.3 million hectares under crop or livestock production. The variable geography and diversity of agricultural production systems and management practices makes estimating risk of soil erosion from agricultural landscapes in the Canadian Lake Erie basin challenging. Risk of soil erosion depends on a combination of factors including the extent to which soil remains bare, which differs with crop type and management. Two different approaches of estimating the vulnerability of landscapes to soil erosion will be compared among Soil Landscapes of Canada in the Lake Erie basin: a modelling approach incorporating farm census and soil survey data, represented by the 2011 Agriculture and Agri-Food Canada Agri-Environmental Indicator for Soil Erosion Risk; and, a measured approach using remotely sensed data that quantifies the magnitude of bare and covered soil across the basin. Results from both approaches will be compared by scaling the national level (1:1 million) Soil Erosion Risk Indicator and the remotely sensed data (30x30 m resolution) to the quaternary watershed level.

  7. An extreme wind erosion event of the fresh Eyjafjallajökull 2010 volcanic ash.

    Science.gov (United States)

    Arnalds, Olafur; Thorarinsdottir, Elin Fjola; Thorsson, Johann; Waldhauserova, Pavla Dagsson; Agustsdottir, Anna Maria

    2013-01-01

    Volcanic eruptions can generate widespread deposits of ash that are subsequently subjected to erosive forces which causes detrimental effects on ecosystems. We measured wind erosion of the freshly deposited Eyjafjallajökull ash at a field site the first summer after the 2010 eruption. Over 30 wind erosion events occurred (June-October) at wind speeds > 10 m s(-1) in each storm with gusts up to 38.7 m s(-1). Surface transport over one m wide transect (surface to 150 cm height) reached > 11,800 kg m(-1) during the most intense storm event with a rate of 1,440 kg m(-1) hr(-1) for about 6½ hrs. This storm is among the most extreme wind erosion events recorded on Earth. The Eyjafjallajökull wind erosion storms caused dust emissions extending several hundred km from the volcano affecting both air quality and ecosystems showing how wind erosion of freshly deposited ash prolongs impacts of volcanic eruptions.

  8. 11 Soil Microbial Biomass

    African Journals Online (AJOL)

    186–198. Insam H. (1990). Are the soil microbial biomass and basal respiration governed by the climatic regime? Soil. Biol. Biochem. 22: 525–532. Insam H. D. and Domsch K. H. (1989). Influence of microclimate on soil microbial biomass. Soil Biol. Biochem. 21: 211–21. Jenkinson D. S. (1988). Determination of microbial.

  9. Molecular microbial ecology manual

    NARCIS (Netherlands)

    Kowalchuk, G.A.; Bruijn, de F.J.; Head, I.M.; Akkermans, A.D.L.

    2004-01-01

    The field of microbial ecology has been revolutionized in the past two decades by the introduction of molecular methods into the toolbox of the microbial ecologist. This molecular arsenal has helped to unveil the enormity of microbial diversity across the breadth of the earth's ecosystems, and has

  10. Microbial Rechargeable Battery

    NARCIS (Netherlands)

    Molenaar, Sam D.; Mol, Annemerel R.; Sleutels, Tom H.J.A.; Heijne, Ter Annemiek; Buisman, Cees J.N.

    2016-01-01

    Bioelectrochemical systems hold potential for both conversion of electricity into chemicals through microbial electrosynthesis (MES) and the provision of electrical power by oxidation of organics using microbial fuel cells (MFCs). This study provides a proof of concept for a microbial

  11. Childhood microbial keratitis

    Directory of Open Access Journals (Sweden)

    Abdullah G Al Otaibi

    2012-01-01

    Conclusion: Children with suspected microbial keratitis require comprehensive evaluation and management. Early recognition, identifying the predisposing factors and etiological microbial organisms, and instituting appropriate treatment measures have a crucial role in outcome. Ocular trauma was the leading cause of childhood microbial keratitis in our study.

  12. Lithosphere erosion atop mantle plumes

    Science.gov (United States)

    Agrusta, R.; Arcay, D.; Tommasi, A.

    2012-12-01

    Mantle plumes are traditionally proposed to play an important role in lithosphere erosion. Seismic images beneath Hawaii and Cape Verde show a lithosphere-asthenosphere-boundary (LAB) up to 50 km shallower than the surroundings. However, numerical models show that unless the plate is stationary the thermo-mechanical erosion of the lithosphere does not exceed 30 km. We use 2D petrological-thermo-mechanical numerical models based on a finite-difference method on a staggered grid and marker in cell method to study the role of partial melting on the plume-lithosphere interaction. A homogeneous peridotite composition with a Newtonian temperature- and pressure-dependent viscosity is used to simulate both the plate and the convective mantle. A constant velocity, ranging from 5 to 12.5 cm/yr, is imposed at the top of the plate. Plumes are created by imposing a thermal anomaly of 150 to 350 K on a 50 km wide domain at the base of the model (700 km depth); the plate right above the thermal anomaly is 40 Myr old. Partial melting is modeled using batch-melting solidus and liquidus in anhydrous conditions. We model the progressive depletion of peridotite and its effect on partial melting by assuming that the melting degree only strictly increases through time. Melt is accumulated until a porosity threshold is reached and the melt in excess is then extracted. The rheology of the partially molten peridotite is determined using viscous constitutive relationship based on a contiguity model, which enables to take into account the effects of grain-scale melt distribution. Above a threshold of 1%, melt is instantaneously extracted. The density varies as a function of partial melting degree and extraction. Besides, we analyze the kinematics of the plume as it impacts a moving plate, the dynamics of time-dependent small-scale convection (SSC) instabilities developing in the low-viscosity layer formed by spreading of hot plume material at the lithosphere base, and the resulting thermal

  13. X-ray diagnosis of erosive gastritis

    International Nuclear Information System (INIS)

    Taskov, A.; Krastin, A.

    1993-01-01

    A series of 602 patients are studied according to a standard protocol including double contrast examination, taking films with dosed compression and complete filling (accordingly 3+3+1 radiographs). A barium suspension at concentration 200.0 BaSO 4 in 100 ml water is used as a positive contrast medium, and effervescent powder or pills - as a negative contrast. Erosive gastritis is diagnosed in 48 patients (7.9%) of which 38 present complete erosions (79.2%), 6 (12.6%) - incomplete, and 4 (8.3%) - mixed erosions. In 35 cases (72.9%) erosions are differentiated in double-contrast films, while in 21 (43.8%) - in those with compression. The advantage of the double contrast technique consists in visualization of erosions of the body of the stomach and discovering of incomplete erosions. In 483 patients a comparative assessment is done of the X-ray and endoscopic findings. There are recorded 5 false-positive and 25 false-negative radiological results. The sensitivity of the X-ray study in terms of erosive gastritis amounts to 59.7%. 15 refs., 4 figs. (orig.)

  14. Soft drinks and in vitro dental erosion.

    Science.gov (United States)

    Gravelle, Brent L; Hagen Ii, Ted W; Mayhew, Susan L; Crumpton, Brooks; Sanders, Tyler; Horne, Victoria

    2015-01-01

    The purpose of this investigation was to determine to what extent the in vitro exposure of healthy teeth to various commonly consumed carbonated soft drinks may precipitate dental erosion. Forty-two healthy, extracted, previously unerupted human molars were weighed prior to, during, and after suspension in various sugared and diet or zero-calorie carbonated beverages for 20 days; the specimens were stored at room temperature while being stirred at 275 rpm. The percentage decrease in tooth weight from before to after exposure represented the weight loss due to enamel erosion; values in the experimental groups varied from 3.22% to 44.52% after 20 days' exposure. Data were subjected to analysis of variance and post hoc Scheffe testing at a level of α = 0.05. Nonsugared drinks (diet and zero-calorie) as a whole were more erosive than sugared beverages. A significant positive correlation was found between the amount of titratable acid and percentage of tooth erosion, while a significant negative correlation was revealed between the beverage pH and percentage of tooth erosion. No significant correlations were found between calcium or phosphate ion concentrations and the amount of erosion. It appears that enamel erosion is dependent on not only the beverage flow rate, pH, and amount of titratable acid, but also whether the soft drink is of the diet or zero-calorie variety, which reflects the type of artificial sweetener present.

  15. Development and evaluation of the bacterial fate and transport module for the Agricultural Policy/Environmental eXtender (APEX) model.

    Science.gov (United States)

    Hong, Eun-Mi; Park, Yongeun; Muirhead, Richard; Jeong, Jaehak; Pachepsky, Yakov A

    2018-02-15

    The Agricultural Policy/Environmental eXtender (APEX) is a watershed-scale water quality model that includes detailed representation of agricultural management. The objective of this work was to develop a process-based model for simulating the fate and transport of manure-borne bacteria on land and in streams with the APEX model. The bacteria model utilizes manure erosion rates to estimate the amount of edge-of-field bacteria export. Bacteria survival in manure is simulated as a two-stage process separately for each manure application event. In-stream microbial fate and transport processes include bacteria release from streambeds due to sediment resuspension during high flow events, active release from the streambed sediment during low flow periods, bacteria settling with sediment, and survival. Default parameter values were selected from published databases and evaluated based on field observations. The APEX model with the newly developed microbial fate and transport module was applied to simulate fate and transport of the fecal indicator bacterium Escherichia coli in the Toenepi watershed, New Zealand that was monitored for seven years. The stream network of the watershed ran through grazing lands with daily bovine waste deposition. Results show that the APEX with the bacteria module reproduced well the monitored pattern of E. coli concentrations at the watershed outlet. The APEX with the microbial fate and transport module will be utilized for predicting microbial quality of water as affected by various agricultural practices, evaluating monitoring protocols, and supporting the selection of management practices based on regulations that rely on fecal indicator bacteria concentrations. Published by Elsevier B.V.

  16. Estimating surface soil erosion losses and mapping erosion risk for Yusufeli micro-catchment (Artvin

    Directory of Open Access Journals (Sweden)

    Mustafa Tüfekçioğlu

    2016-10-01

    Full Text Available Sheet erosion, one of the most important types of water erosion, takes place on the top soil as tiny soil layer movement that affects lake and stream ecosystem. This type of erosion is very important because the productive soil layer on the top soil can be lost in a very short period of time. The goal of this study was to quantify the amount of surface (sheet and rill soil erosion, and to identify areas under high erosion risk within the study area at Yusufeli province in Artvin by using RUSLE erosion methodology. As a result of the study it was found that the average annual potential soil loss by surface erosion was 3.6 ton ha-1yr-1. Additionally, the maps produced and conclusions reached by the study revealed that the areas of high erosion risk were identified spatially and measures to control erosion on some of these high risk areas can be possible with appropriate erosion control techniques.

  17. Erosion by rain in the western Congo

    International Nuclear Information System (INIS)

    Ploey, J. de

    1967-01-01

    Vast expanses of the western part of central and southern Africa are covered with uniform, sandy formations of the Kalahari type. The topography of these areas and their present morphological characteristics are mainly the result of erosion by rain. Information on the hydrology of the surface waters in these areas is fairly limited and is insufficient to permit any conclusions regarding the way in which erosion by rain takes place. To obtain a better understanding of these phenomena, the author devised a series of experiments based on the use of 46 Sc-labelled radioactive sand. These experiments began at the beginning of the 1964/65 rainy season and are continuing. The experimental plot corresponds to convex and rectilinear portions of a hillside with a slope varying between 0 and 12 degrees. The vegetation consists of grassy savannah of substeppe appearance and secondary forests. Series of labelled samples were placed successively on the surface of the experimental plot and the erosive effect of rain was determined by measuring the residual concentrations after rainfall. Some samples were placed below a shield so as to eliminate the effects of splash and reveal the part played by runoff. Radiographic films were used to study the dispersion of labelled particles in the surrounding area. This radiographic method made it possible to determine the scale of erosion by splash for different rainfall conditions. The erosion diagrams obtained from these experiments show the correlations that exist between the intensity and duration of the rainfall and the erosion of the soil. Examination of the erosion diagrams and the shielded samples and analysis of the radiographs showed that erosion by rain on Kalahari ground covered with substeppe savannah is caused mainly by splash erosion and by dispersed, intermittent runoff. Sheet wash plays no part if the slope is less than 12 degrees. (author) [fr

  18. Quantifying and modeling soil erosion and sediment export from construction sites in southern California

    Science.gov (United States)

    Wernet, A. K.; Beighley, R. E.

    2006-12-01

    Soil erosion is a power process that continuously alters the Earth's landscape. Human activities, such as construction and agricultural practices, and natural events, such as forest fires and landslides, disturb the landscape and intensify erosion processes leading to sudden increases in runoff sediment concentrations and degraded stream water quality. Understanding soil erosion and sediment transport processes is of great importance to researchers and practicing engineers, who routinely use models to predict soil erosion and sediment movement for varied land use and climate change scenarios. However, existing erosion models are limited in their applicability to constructions sites which have highly variable soil conditions (density, moisture, surface roughness, and best management practices) that change often in both space and time. The goal of this research is to improve the understanding, predictive capabilities and integration of treatment methodologies for controlling soil erosion and sediment export from construction sites. This research combines modeling with field monitoring and laboratory experiments to quantify: (a) spatial and temporal distribution of soil conditions on construction sites, (b) soil erosion due to event rainfall, and (c) potential offsite discharge of sediment with and without treatment practices. Field sites in southern California were selected to monitor the effects of common construction activities (ex., cut/fill, grading, foundations, roads) on soil conditions and sediment discharge. Laboratory experiments were performed in the Soil Erosion Research Laboratory (SERL), part of the Civil and Environmental Engineering department at San Diego State University, to quantify the impact of individual factors leading to sediment export. SERL experiments utilize a 3-m by 10-m tilting soil bed with soil depths up to 1 m, slopes ranging from 0 to 50 percent, and rainfall rates up to 150 mm/hr (6 in/hr). Preliminary modeling, field and laboratory

  19. Long-Term Analysis for Harvest Erosion Caused by Sugar Beet Production in Turkey

    Directory of Open Access Journals (Sweden)

    Selen DEVİREN SAYGIN

    2018-02-01

    Full Text Available The sustainability of soil resources is under significant threat due to the accelerated anthropogenic pressures at the historical expansion of human population. In this context, soil erosion is defined as a limiting factor for human interests in terms of ecosystem services. As an erosion type, harvest erosion occurs by harvesting of the taproot and tuberous root plants such as sugar beet (Beta vulgaris L., potato (Solanum tuberosum L., carrot (Daucus carota L. and chicory (Cichorium intybus L., has begun to take attention in recent years. The objective of this study was to estimate soil loss due to harvest erosion and to economically analyze the transport of plant nutrients between 1999 and 2016 from sugar beet growing areas in Turkey. For this aim, the compiled data of 25 different sugar factories throughout Turkey were obtained from Türkşeker and soil loss estimations were performed and economically analyzed. According to the results, average soil loss rate was calculated as 3.41 Mg ha-1y-1 for the studied period (1999-2016. That means annually an average of 716983 Mg soil removed from the Türkşeker sugar beet production areas. This result indicated that harvest erosion represents only 0.9% of soil lost by water erosion in Turkey. But, if tolerable soil loss value considered as “1 Mg ha-1 y-1”, calculated soil loss values are above this critical value for all the factories. In addition, economic assessments of soil losses showed that costs are to be more than US $10 000 annually on the 60% of the factories due to removal of plant nutrients with harvest process. And, annually US $419 433 investment must be made to recover all these losses. Conclusively, harvest erosion as an ignored erosion type must be emphasized to the economic sustainability of natural resources in fragile ecosystems such as our country.

  20. Microbial adhesion in flow displacement systems

    NARCIS (Netherlands)

    Busscher, HJ; van der Mei, HC

    Flow displacement systems are superior to many other (static) systems for studying microbial adhesion to surfaces because mass transport and prevailing shear conditions can be adequately controlled and notoriously ill-defined slight rinsing steps to remove so-called "loosely adhering organisms" can

  1. Mechanistic model for microbial growth on hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Mallee, F M; Blanch, H W

    1977-12-01

    Based on available information describing the transport and consumption of insoluble alkanes, a mechanistic model is proposed for microbial growth on hydrocarbons. The model describes the atypical growth kinetics observed, and has implications in the design of large scale equipment for single cell protein (SCP) manufacture from hydrocarbons. The model presents a framework for comparison of the previously published experimental kinetic data.

  2. [Gastric band erosion: Alternative management].

    Science.gov (United States)

    Echaverry-Navarrete, Denis José; Maldonado-Vázquez, Angélica; Cortes-Romano, Pablo; Cabrera-Jardines, Ricardo; Mondragón-Pinzón, Erwin Eduardo; Castillo-González, Federico Armando

    2015-01-01

    Obesity is a public health problem, for which the prevalence has increased worldwide at an alarming rate, affecting 1.7 billion people in the world. To describe the technique employed in incomplete penetration of gastric band where endoscopic management and/or primary closure is not feasible. Laparoscopic removal of gastric band was performed in five patients with incomplete penetrance using Foley catheterization in the perforation site that could lead to the development of a gastro-cutaneous fistula. The cases presented include a leak that required surgical lavage with satisfactory outcome, and one patient developed stenosis 3 years after surgical management, which was resolved endoscopically. In all cases, the penetration site closed spontaneously. Gastric band erosion has been reported in 3.4% of cases. The reason for inserting a catheter is to create a controlled gastro-cutaneous fistula, allowing spontaneous closure. Various techniques have been described: the totally endoscopic, hybrid techniques (endoscopic/laparoscopic) and completely laparoscopic. A technique is described here that is useful and successful in cases where the above-described treatments are not viable. Copyright © 2015. Published by Masson Doyma México S.A.

  3. Significant differences in late Quaternary bedrock erosion and transport

    DEFF Research Database (Denmark)

    Andrews, John; Bjørk, Anders Anker; Eberl, Dennis

    2015-01-01

    in 10 cores from the two margins. On the East Greenland Shelf (EGS), late Quaternary samples have an average quartz weight per cent of 6.22.3 versus 12.83.9 from the West Greenland Shelf (WGS), and 12.024.8 versus 1.9 2.3wt% for pyroxene. K-means clustering indicated only 9% of the samples did not fit...

  4. Compressor Impeller Erosion Resistant Surface Treatment

    National Research Council Canada - National Science Library

    Riley, Michael

    2000-01-01

    ...). Coatings based on tungsten carbide tantalum carbide. titanium carbide all with a cobalt matrix were evaluated for high velocity particle erosion in conventional wear test studies as well as wind tunnel testing...

  5. Puerto Rico Relative Vulnerability to Erosion

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Physical factors, such as the slope of the land, the texture of the soil, and the precipitation regime influence erosion in an area. Parts of Puerto Rico are very...

  6. Paradiaphyseal calcific tendinitis with cortical bone erosion.

    Science.gov (United States)

    Fritz, P; Bardin, T; Laredo, J D; Ziza, J M; D'Anglejan, G; Lansaman, J; Bucki, B; Forest, M; Kuntz, D

    1994-05-01

    To determine the clinical, radiologic, and histologic features of calcific tendinitis with cortical bone erosion. The records of 6 patients with paradiaphyseal calcific tendinitis and adjacent bone cortex erosion were reviewed. Calcific tendinitis involved the linea aspera in 4 patients, the bicipital groove in 1 patient, and the deltoid insertion in another. Calcium deposits were associated with cortical bone erosions, revealed on plain radiographs in 4 patients and computed tomography scans in 2. Bone scans were performed in 2 patients and showed local hyperfixation of the isotope. In 4 patients, suspicion of a neoplasm led to a biopsy. Calcium deposits appeared to be surrounded by a foreign body reaction with numerous giant cells. Apatite crystals were identified by transmission electron microscopy and elemental analysis in 1 surgical sample. Paradiaphyseal calcific tendinitis with cortical bone erosion is an uncommon presentation of apatite deposition disease.

  7. Emission Facilities - Erosion & Sediment Control Facilities

    Data.gov (United States)

    NSGIC Education | GIS Inventory — An Erosion and Sediment Control Facility is a DEP primary facility type related to the Water Pollution Control program. The following sub-facility types related to...

  8. Understanding and Predicting Gun Barrel Erosion

    National Research Council Canada - National Science Library

    Johnston, Ian A

    2005-01-01

    The Australian Defence Force will soon have to contend with gun barrel erosion issues arising from the use of new low-vulnerability gun propellants, the acquisition of new ammunition and gun systems...

  9. Puerto Rico Relative Erosion Potential (REP) - 2000

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The relative erosion potential is an indicator of sediment and pollution runoff from land based on slope, soil type, land cover (circa 2000) and (maximum monthly)...

  10. Puerto Rico Relative Erosion Potential (REP) - 1990

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The relative erosion potential is an indicator of sediment and pollution runoff from land based on slope, soil type, land cover (circa 1990) and (maximum monthly)...

  11. Definition of tolerable soil erosion values

    Directory of Open Access Journals (Sweden)

    G. Sparovek

    1997-09-01

    Full Text Available Although the criteria for defining erosion tolerance are well established, the limits generally used are not consistent with natural, economical and technological conditions. Rates greater than soil formation can be accepted only until a minimum of soil depth is reached, provided that they are not associated with environmental hazard or productivity losses. A sequence of equations is presented to calculate erosion tolerance rates through time. The selection of equation parameters permits the definition of erosion tolerance rates in agreement with environmental, social and technical needs. The soil depth change that is related to irreversible soil degradation can be calculated. The definition of soil erosion tolerance according to these equations can be used as a guideline for sustainable land use planning and is compatible with expert systems.

  12. PROBLEMS OF SOIL PROTECTION FROM EROSION

    Directory of Open Access Journals (Sweden)

    M. Voloshuk

    2007-10-01

    Full Text Available In this article the problems of soil protection from erosion in Moldova are considered. The history (evolution of erosive processes is generalized, the first items of information on presence washed off soils are marked. Purposeful study of soil erosion, development of measures of struggle with it were begun in Moldova at the end of 40 years. In connection with transition to new economic methods of conducting economy (farmers, rent, privatization of land before pedologist, the experts of design organizations put forward the new requirements to study of erosive processes, development of soil protection, ecologo-adaptive systems of landscape agriculture. The tasks for improvement of a soil cover, restoration of fertility soil and their protection are put forward which are necessary for deciding in a near future.

  13. Rain Erosion/Measurement Impact Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The FARM Rain Erosion/Impact Measurement Lab develops solutions for deficiencies in the ability of materials, coatings and designs to withstand a severe operational...

  14. Soil erosion assessment - Mind the gap

    Science.gov (United States)

    Kim, Jongho; Ivanov, Valeriy Y.; Fatichi, Simone

    2016-12-01

    Accurate assessment of erosion rates remains an elusive problem because soil loss is strongly nonunique with respect to the main drivers. In addressing the mechanistic causes of erosion responses, we discriminate between macroscale effects of external factors - long studied and referred to as "geomorphic external variability", and microscale effects, introduced as "geomorphic internal variability." The latter source of erosion variations represents the knowledge gap, an overlooked but vital element of geomorphic response, significantly impacting the low predictability skill of deterministic models at field-catchment scales. This is corroborated with experiments using a comprehensive physical model that dynamically updates the soil mass and particle composition. As complete knowledge of microscale conditions for arbitrary location and time is infeasible, we propose that new predictive frameworks of soil erosion should embed stochastic components in deterministic assessments of external and internal types of geomorphic variability.

  15. MALIGNANT TRANSFORMATION OF EROSIVE ORAL LICHEN PLANUS

    Directory of Open Access Journals (Sweden)

    Siti Chumaeroh

    2006-04-01

    Full Text Available Lichen planus is a relatively common inflammatory disorder which may have cutaneous and or mucosal manifestation. The malignant potential of oral lichen planus is still debatable. Some authors are sceptical about the premalignant nature of the disease, while other investigators have reported that malignant transformations occur in 1-10% of the cases. The aim of this study is to report a case of erosive lichen plans which shows malignant transformation of histopathologic examination. A man of 39 years old visited the Dental Department or Kajradi's Hospital with pain symptoms of the palate, buccal and gingival mucosa on both sides for 6 months. The physical examination shows the white lesion with striae configuration and pain, red erosive area inside the palate extends to the buccal mucosa and the gingival mucosa. The suspect diagnosis is erosive lichen planus, but the histopathologic examination shows epidermoid carcinoma. It is concluded that erosive oral lichen planus has the potential to transform into epidermoid carcinoma.

  16. Dental erosion: understanding this pervasive condition.

    Science.gov (United States)

    Almeida e Silva, Júnio S; Baratieri, Luiz Narciso; Araujo, Edson; Widmer, Nicolas

    2011-08-01

    Dental erosion is a contemporary disease, mostly because of the change of the eating patterns that currently exist in society. It is a "silent" and multifactorial disease, and is highly influenced by habits and lifestyles. The prevalence of dental erosion has considerably increased, with this condition currently standing as a great challenge for the clinician, regarding the diagnosis, identification of the etiological factors, prevention, and execution of an adequate treatment. This article presents a dental erosion review and a case report of a restorative treatment of dental erosion lesions using a combination of bonded ceramic overlays to reestablish vertical dimension and composite resin to restore the worn palatal and incisal surfaces of the anterior upper teeth. Adequate function and esthetics can be achieved with this approach. © 2011 Wiley Periodicals, Inc.

  17. Numerical and experimental investigations on cavitation erosion

    Science.gov (United States)

    Fortes Patella, R.; Archer, A.; Flageul, C.

    2012-11-01

    A method is proposed to predict cavitation damage from cavitating flow simulations. For this purpose, a numerical process coupling cavitating flow simulations and erosion models was developed and applied to a two-dimensional (2D) hydrofoil tested at TUD (Darmstadt University of Technology, Germany) [1] and to a NACA 65012 tested at LMH-EPFL (Lausanne Polytechnic School) [2]. Cavitation erosion tests (pitting tests) were carried out and a 3D laser profilometry was used to analyze surfaces damaged by cavitation [3]. The method allows evaluating the pit characteristics, and mainly the volume damage rates. The paper describes the developed erosion model, the technique of cavitation damage measurement and presents some comparisons between experimental results and numerical damage predictions. The extent of cavitation erosion was correctly estimated in both hydrofoil geometries. The simulated qualitative influence of flow velocity, sigma value and gas content on cavitation damage agreed well with experimental observations.

  18. ERO modeling and sensitivity analysis of locally enhanced beryllium erosion by magnetically connected antennas

    Science.gov (United States)

    Lasa, A.; Borodin, D.; Canik, J. M.; Klepper, C. C.; Groth, M.; Kirschner, A.; Airila, M. I.; Borodkina, I.; Ding, R.; Contributors, JET

    2018-01-01

    Experiments at JET showed locally enhanced, asymmetric beryllium (Be) erosion at outer wall limiters when magnetically connected ICRH antennas were in operation. A first modeling effort using the 3D erosion and scrape-off layer impurity transport modeling code ERO reproduced qualitatively the experimental outcome. However, local plasma parameters—in particular when 3D distributions are of interest—can be difficult to determine from available diagnostics and so erosion / impurity transport modeling input relies on output from other codes and simplified models, increasing uncertainties in the outcome. In the present contribution, we introduce and evaluate the impact of improved models and parameters with largest uncertainties of processes that impact impurity production and transport across the scrape-off layer, when simulated in ERO: (i) the magnetic geometry has been revised, for affecting the separatrix position (located 50-60 mm away from limiter surface) and thus the background plasma profiles; (ii) connection lengths between components, which lead to shadowing of ion fluxes, are also affected by the magnetic configuration; (iii) anomalous transport of ionized impurities, defined by the perpendicular diffusion coefficient, has been revisited; (iv) erosion yields that account for energy and angular distributions of background plasma ions under the present enhanced sheath potential and oblique magnetic field, have been introduced; (v) the effect of additional erosion sources, such as charge-exchange neutral fluxes, which are dominant in recessed areas like antennas, has been evaluated; (vi) chemically assisted release of Be in molecular form has been included. Sensitivity analysis highlights a qualitative effect (i.e. change in emission patterns) of magnetic shadowing, anomalous diffusion, and inclusion of neutral fluxes and molecular release of Be. The separatrix location, and energy and angular distribution of background plasma fluxes impact erosion

  19. Application of an agricultural water balance and erosion model in environmental science: a user perspective

    International Nuclear Information System (INIS)

    Hakonson, T.E.; Foster, G.R.; Lane, L.J.; Nyhan, J.W.

    1984-01-01

    Studies have shown that the hydrologic erosion of soil is a major factor in the translational movement of environmental plutonium deposited on the ground surface and, as a consequence of rain splash of soil, also greatly influences transport of plutonium to plants including vegetable crops. This paper discusses the use of CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems), in developing environmental research programs at Los Alamos and in designing and monitoring the performance of shallow land burial (SLB) sites for low-level radioactive waste (LLW). Discussion is also presented on research needs and ongoing studies involving Los Alamos to supply some of those needs. 37 references, 7 figures, 3 tables

  20. Bank erosion processes in waterways

    NARCIS (Netherlands)

    Duro, G.; Uijttewaal, W.S.J.; Kleinhans, M; Crosato, A.

    2017-01-01

    Waterways serve for several functions besides  transporting goods and people. The ecological  importance of navigable rivers has taken much  attention during recent decades bringing efforts  to improve these natural corridors for fauna and  flora (Boeters et al.,

  1. Soil erosion - a local and national problem

    Science.gov (United States)

    C.G. Bates; O.R. Zeasman

    1930-01-01

    The erosion of soils through the action of rain water and that from melting snow is almost universal in its occurrence. The gradual erosion and levelling of any country is inevitable, being a process which has gone on as long as there has been free water on the face of the earth. Nevertheless, this process is an extremely slow one where the landscape is naturally well...

  2. Natural and anthropogenic rates of soil erosion

    Directory of Open Access Journals (Sweden)

    Mark A. Nearing

    2017-06-01

    Full Text Available Regions of land that are brought into crop production from native vegetation typically undergo a period of soil erosion instability, and long term erosion rates are greater than for natural lands as long as the land continues being used for crop production. Average rates of soil erosion under natural, non-cropped conditions have been documented to be less than 2 Mg ha−1 yr−1. On-site rates of erosion of lands under cultivation over large cropland areas, such as in the United States, have been documented to be on the order of 6 Mg ha−1 yr−1 or more. In northeastern China, lands that were brought into production during the last century are thought to have average rates of erosion over this large area of as much as 15 Mg ha−1 yr−1 or more. Broadly applied soil conservation practices, and in particular conservation tillage and no-till cropping, have been found to be effective in reducing rates of erosion, as was seen in the United States when the average rates of erosion on cropped lands decreased from on the order of 9 Mg ha−1 yr−1 to 6 or 7 Mg ha−1 yr−1 between 1982 and 2002, coincident with the widespread adoption of new conservation tillage and residue management practices. Taking cropped lands out of production and restoring them to perennial plant cover, as was done in areas of the United States under the Conservation Reserve Program, is thought to reduce average erosion rates to approximately 1 Mg ha−1 yr−1 or less on those lands.

  3. Determining Wind Erosion in the Great Plains

    OpenAIRE

    Elwin G. Smith; Burton C. English

    1982-01-01

    Wind erosion is defined as the movement of soil particles resulting from strong turbulent winds. The movement of soil particles can be categorized as suspension, saltation, or surface creep. Fine soil particles can be suspended in the atmosphere and carried for great distances. Particles too large to be suspended move in a jumping action along the soil surface, known as saltation. Heavier particles have a rolling movement along the surface and this type of erosion is surface creep.

  4. Airphoto analysis of erosion control practices

    Science.gov (United States)

    Morgan, K. M.; Morris-Jones, D. R.; Lee, G. B.; Kiefer, R. W.

    1980-01-01

    The Universal Soil Loss Equation (USLE) is a widely accepted tool for erosion prediction and conservation planning. In this study, airphoto analysis of color and color infrared 70 mm photography at a scale of 1:60,000 was used to determine the erosion control practice factor in the USLE. Information about contour tillage, contour strip cropping, and grass waterways was obtained from aerial photography for Pheasant Branch Creek watershed in Dane County, Wisconsin.

  5. WIND EROSION INTENSITY DETERMINATION USING SOIL PARTICLE CATCHER DEVICES

    Directory of Open Access Journals (Sweden)

    Lenka Lackóová

    2013-12-01

    Full Text Available To analyze wind erosion events in the real terrain conditions, we proposed to construct a prototype of soil particle catcher devices to trap soil particles. With these devices we are able to measure the intensity of wind erosion at six different heights above the soil surface in one location or at three different heights in two places. It is possible to use them for six different places at the same time as well. We performed field measurements to determine the amount of soil particles transported by the wind between 26th – 31st March 2012. Each measuring took 60 minutes. After this time the soil particle catchers were emptied and further measurements carried out. At the beginning we selected two places for measurement (soil HPJ 16 and 37 at two heights, one above the other. Then we used two measuring systems 40 m apart at two sites (D2 and D4 and the soil captured at two heights (0, 1. The maximum weight of soil particles trapped in measuring system D2 at height (0 was 1242.7 g at a wind speed of 9.6 ms-1. At measurement height (1 the maximum weight was 72.7 g trapped at the same average hourly rate, but during different measurement events. The measuring system at D4 trapped the highest amount of soil at a wind speed of 8.9 ms-1 (1141.7 g at height (0 and at a speed of 9.3 ms-1 (22.3 g at height (1. During the measurements with the two basic measuring systems D4 and D2, we measured the wind erosion intensity together with soil particle catchers D1 and D3. D3 was placed between devices D4 and D2, D1 was 20 m ahead D2. Soil particle catchers were placed on the soil surface at height position (0. We measured increasing soil erosion downwind on four locations spaced at 20 m. The results show that with there is an increasing quantity of particles collected as the erosive surface length increases, due to the so-called snowball effect. We analyzed selected trapped soil samples in order to determine the size of the soil particles and their proportion

  6. Erosion problems in Alexandroupolis coastline, North-Eastern Greece

    Science.gov (United States)

    Xeidakis, G. S.; Delimani, P.; Skias, S.

    2007-12-01

    This paper deals with the coastal erosion processes and the related problems around the city of Alexandroupolis, NE Aegean Sea, N. Greece. The area is very fast developing, as the city is an important port and a summer resort center in SE Balkans, and will become soon a transportation and energy center, as well. The coastline under study exhibits an east west orientation and has a length of more than 50 km. The spatial distribution and the characteristics of the changes in the shoreline were studied by comparing old and new air photographs and topographic maps, as well as through repeated series of field observations and local measurements regarding the erosion process. From these studies it was concluded that the greater stretch of the western part of the coast, under consideration, is of moderate to high relief, with a considerable participation of coastal cliffs. It consists of conglomerates of varying granulometry and consistency and is under moderate to severe erosion process. The erosion phenomena in the western part of the coast may be attributed, primarily, to strong S, SW winds, blowing in the area and to trapping of sediments by Alexandroupolis’ port breakwaters; the port stops or/and diverts the sediments to the open sea; and to the east to west longshore sea current, prevailing in the area. The eastern stretch of the coast is a plain area, formed by sandy silty sediments; being a part of the river Evros’ Delta, it is under deposition and accretes seawards. The majority of the coasts under consideration are classified as coasts of high wave energy potential. Hard structures, as shore protection measures, have been constructed in some places, but they were proved, in rather short time-period, ineffective and suffered extensive failures. Thus, it is argued that for a long-term cost-effective tackling of the various erosion problems on any stretch, priority must be given to soft engineering measures; although, certain hard measures, carefully selected

  7. Susceptibility of bovine dental enamel with initial erosion lesion to new erosive challenges.

    Directory of Open Access Journals (Sweden)

    Gabriela Cristina de Oliveira

    Full Text Available This in vitro study evaluated the impact of initial erosion on the susceptibility of enamel to further erosive challenge. Thirty bovine enamel blocks were selected by surface hardness and randomized into two groups (n = 15: GC- group composed by enamel blocks without erosion lesion and GT- group composed by enamel blocks with initial erosion lesion. The baseline profile of each block was determined using the profilometer. The initial erosion was produced by immersing the blocks into HCl 0.01 M, pH 2.3 for 30 seconds, under stirring. The erosive cycling consisted of blocks immersion in hydrochloric acid (0.01 M, pH 2.3 for 2 minutes, followed by immersion in artificial saliva for 120 minutes. This procedure was repeated 4 times a day for 5 days, and the blocks were kept in artificial saliva overnight. After erosive cycling, final profile measurement was performed. Profilometry measured the enamel loss by the superposition of initial and final profiles. Data were analyzed by t-test (p<0.05. The result showed no statistically significant difference between groups (GS = 14.60±2.86 and GE = .14.69±2.21 μm. The presence of initial erosion on bovine dental enamel does not enhance its susceptibility to new erosive challenges.

  8. Low cost sic coated erosion resistant graphite

    International Nuclear Information System (INIS)

    Zafar, M.F.; Nicholls, J.R.

    2007-01-01

    The development of materials with unique and improved properties using low cost processes is essential to increase performance and reduce cost of the solid rocket motors. Specifically advancements are needed for boost phase nozzle. As these motors operate at very high pressure and temperatures, the nozzle must survive high thermal stresses with minimal erosion to maintain performance. Currently three material choices are being exploited; which are refractory metals, graphite and carbon-carbon composites. Of these three materials graphite is the most attractive choice because of its low cost, light weight, and easy forming. However graphite is prone to erosion, both chemical and mechanical, which may affect the ballistic conditions and mechanical properties of the nozzle. To minimize this erosion high density graphite is usually preferred; which is again very expensive. Another technique used to minimize the erosion is Pyrolytic Graphite (PG) coating inside the nozzle. However PG coating is prone to cracking and spallation along with very cumbersome deposition process. Another possible methodology to avoid this erosion is to convert the inside surface of the rocket nozzle to Silicon Carbide (SiC), which is very erosion resistant and have much better thermal stability compared to graphite and even PG. Due to its functionally gradient nature such a layer will be very adherent and resistant to spallation. The current research is focused on synthesizing, characterizing and oxidation testing of such a converted SiC layer on commercial grade graphite. (author)

  9. Erosion of Earthen Levees by Wave Action

    Science.gov (United States)

    Ozeren, Y.; Wren, D. G.; Reba, M. L.

    2016-02-01

    Earthen levees of aquaculture and irrigation reservoirs in the United States often experience significant erosion due to wind-generated waves. Typically constructed using local soils, unprotected levees are subjected to rapid erosion and retreat due to wind generated waves and surface runoff. Only a limited amount of published work addresses the erosion rates for unprotected levees, and producers who rely on irrigation reservoirs need an economic basis for selecting a protection method for vulnerable levees. This, in turn, means that a relationship between wave energy and erosion of cohesive soils is needed. In this study, laboratory experiments were carried out in order to quantify wave induced levee erosion and retreat. A model erodible bank was packed using a soil consisting of approximately 14% sand, 73% silt, and 13% clay in a 20.6 m long 0.7 m wide and 1.2 m deep wave tank at the USDA-ARS, National Sedimentation Laboratory in Oxford MS. The geometry of the levee face was monitored by digital camera and the waves were measured by means of 6 capacitance wave staffs. Relationships were established between levee erosion, edge and retreat rates, and incident wave energy.

  10. Satellite-based estimation of rainfall erosivity for Africa

    NARCIS (Netherlands)

    Vrieling, A.; Sterk, G.; Jong, S.M. de

    2010-01-01

    Rainfall erosivity is a measure for the erosive force of rainfall. Rainfall kinetic energy determines the erosivity and is in turn greatly dependent on rainfall intensity. Attempts for its large-scale mapping are rare. Most are based on interpolation of erosivity values derived from rain gauge

  11. Soil erosion as a driver of land-use change

    NARCIS (Netherlands)

    Bakker, M.M.; Govers, G.; Kosmas, C.; VanAcker, H.; Oost, van K.; Rounsevell, M.

    2005-01-01

    Although much research has been carried out on the crop productivity response to soil erosion, little is known about the role of soil erosion as a driver of land-use change. Given, however, the some-times large erosion-induced reductions in crop yields, it appears likely that erosion has a strong

  12. Soil organic carbon redistribution by water erosion--the role of CO2 emissions for the carbon budget.

    Science.gov (United States)

    Wang, Xiang; Cammeraat, Erik L H; Romeijn, Paul; Kalbitz, Karsten

    2014-01-01

    A better process understanding of how water erosion influences the redistribution of soil organic carbon (SOC) is sorely needed to unravel the role of soil erosion for the carbon (C) budget from local to global scales. The main objective of this study was to determine SOC redistribution and the complete C budget of a loess soil affected by water erosion. We measured fluxes of SOC, dissolved organic C (DOC) and CO2 in a pseudo-replicated rainfall-simulation experiment. We characterized different C fractions in soils and redistributed sediments using density fractionation and determined C enrichment ratios (CER) in the transported sediments. Erosion, transport and subsequent deposition resulted in significantly higher CER of the sediments exported ranging between 1.3 and 4.0. In the exported sediments, C contents (mg per g soil) of particulate organic C (POC, C not bound to soil minerals) and mineral-associated organic C (MOC) were both significantly higher than those of non-eroded soils indicating that water erosion resulted in losses of C-enriched material both in forms of POC and MOC. The averaged SOC fluxes as particles (4.7 g C m(-2) yr(-1)) were 18 times larger than DOC fluxes. Cumulative emission of soil CO2 slightly decreased at the erosion zone while increased by 56% and 27% at the transport and depositional zone, respectively, in comparison to non-eroded soil. Overall, CO2 emission is the predominant form of C loss contributing to about 90.5% of total erosion-induced C losses in our 4-month experiment, which were equal to 18 g C m(-2). Nevertheless, only 1.5% of the total redistributed C was mineralized to CO2 indicating a large stabilization after deposition. Our study also underlines the importance of C losses by particles and as DOC for understanding the effects of water erosion on the C balance at the interface of terrestrial and aquatic ecosystems.

  13. Soil Organic Carbon Redistribution by Water Erosion – The Role of CO2 Emissions for the Carbon Budget

    Science.gov (United States)

    Wang, Xiang; Cammeraat, Erik L. H.; Romeijn, Paul; Kalbitz, Karsten

    2014-01-01

    A better process understanding of how water erosion influences the redistribution of soil organic carbon (SOC) is sorely needed to unravel the role of soil erosion for the carbon (C) budget from local to global scales. The main objective of this study was to determine SOC redistribution and the complete C budget of a loess soil affected by water erosion. We measured fluxes of SOC, dissolved organic C (DOC) and CO2 in a pseudo-replicated rainfall-simulation experiment. We characterized different C fractions in soils and redistributed sediments using density fractionation and determined C enrichment ratios (CER) in the transported sediments. Erosion, transport and subsequent deposition resulted in significantly higher CER of the sediments exported ranging between 1.3 and 4.0. In the exported sediments, C contents (mg per g soil) of particulate organic C (POC, C not bound to soil minerals) and mineral-associated organic C (MOC) were both significantly higher than those of non-eroded soils indicating that water erosion resulted in losses of C-enriched material both in forms of POC and MOC. The averaged SOC fluxes as particles (4.7 g C m−2 yr−1) were 18 times larger than DOC fluxes. Cumulative emission of soil CO2 slightly decreased at the erosion zone while increased by 56% and 27% at the transport and depositional zone, respectively, in comparison to non-eroded soil. Overall, CO2 emission is the predominant form of C loss contributing to about 90.5% of total erosion-induced C losses in our 4-month experiment, which were equal to 18 g C m−2. Nevertheless, only 1.5% of the total redistributed C was mineralized to CO2 indicating a large stabilization after deposition. Our study also underlines the importance of C losses by particles and as DOC for understanding the effects of water erosion on the C balance at the interface of terrestrial and aquatic ecosystems. PMID:24802350

  14. Chlorine stress mediates microbial surface attachment in drinking water systems.

    Science.gov (United States)

    Liu, Li; Le, Yang; Jin, Juliang; Zhou, Yuliang; Chen, Guowei

    2015-03-01

    Microbial attachment to drinking water pipe surfaces facilitates pathogen survival and deteriorates disinfection performance, directly threatening the safety of drinking water. Notwithstanding that the formation of biofilm has been studied for decades, the underlying mechanisms for the origins of microbial surface attachment in biofilm development in drinking water pipelines remain largely elusive. We combined experimental and mathematical methods to investigate the role of environmental stress-mediated cell motility on microbial surface attachment in chlorination-stressed drinking water distribution systems. Results show that at low levels of disinfectant (0.0-1.0 mg/L), the presence of chlorine promotes initiation of microbial surface attachment, while higher amounts of disinfectant (>1.0 mg/L) inhibit microbial attachment. The proposed mathematical model further demonstrates that chlorination stress (0.0-5.0 mg/L)-mediated microbial cell motility regulates the frequency of cell-wall collision and thereby controls initial microbial surface attachment. The results reveal that transport processes and decay patterns of chlorine in drinking water pipelines regulate microbial cell motility and, thus, control initial surface cell attachment. It provides a mechanistic understanding of microbial attachment shaped by environmental disinfection stress and leads to new insights into microbial safety protocols in water distribution systems.

  15. Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff-erosion model in the Mamuaba catchment, Brazil.

    Science.gov (United States)

    Marques da Silva, Richarde; Guimarães Santos, Celso Augusto; Carneiro de Lima Silva, Valeriano; Pereira e Silva, Leonardo

    2013-11-01

    This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

  16. Modeling of technical soil-erosion control measures and its impact on soil erosion off-site effects within urban areas

    Science.gov (United States)

    Dostal, Tomas; Devaty, Jan

    2013-04-01

    The paper presents results of surface runoff, soil erosion and sediment transport modeling using Erosion 3D software - physically based mathematical simulation model, event oriented, fully distributed. Various methods to simulate technical soil-erosion conservation measures were tested, using alternative digital elevation models of different precision and resolution. Ditches and baulks were simulated by three different approaches, (i) by change of the land-cover parameters to increase infiltration and decrease flow velocity, (ii) by change of the land-cover parameters to completely infiltrate the surface runoff and (iii) by adjusting the height of the digital elevation model by "burning in" the channels of the ditches. Results show advantages and disadvantages of each approach and conclude suitable methods for combinations of particular digital elevation model and purpose of the simulations. Further on a set of simulations was carried out to model situations before and after technical soil-erosion conservation measures application within a small catchment of 4 km2. These simulations were focused on quantitative and qualitative assessment of technical soil-erosion control measures impact on soil erosion off-site effects within urban areas located downstream of intensively used agricultural fields. The scenarios were built upon a raster digital elevation model with spatial resolution of 3 meters derived from LiDAR 5G vector point elevation data. Use of this high-resolution elevation model allowed simulating the technical soil-erosion control measures by direct terrain elevation adjustment. Also the structures within the settlements were emulated by direct change in the elevation of the terrain model. The buildings were lifted up to simulate complicated flow behavior of the surface runoff within urban areas, using approach of Arévalo (Arévalo, 2011) but focusing on the use of commonly available data without extensive detailed editing. Application of the technical

  17. Watershed erosion modeling using the probability of sediment connectivity in a gently rolling system

    Science.gov (United States)

    Mahoney, David Tyler; Fox, James Forrest; Al Aamery, Nabil

    2018-06-01

    Sediment connectivity has been shown in recent years to explain how the watershed configuration controls sediment transport. However, we find no studies develop a watershed erosion modeling framework based on sediment connectivity, and few, if any, studies have quantified sediment connectivity for gently rolling systems. We develop a new predictive sediment connectivity model that relies on the intersecting probabilities for sediment supply, detachment, transport, and buffers to sediment transport, which is integrated in a watershed erosion model framework. The model predicts sediment flux temporally and spatially across a watershed using field reconnaissance results, a high-resolution digital elevation models, a hydrologic model, and shear-based erosion formulae. Model results validate the capability of the model to predict erosion pathways causing sediment connectivity. More notably, disconnectivity dominates the gently rolling watershed across all morphologic levels of the uplands, including, microtopography from low energy undulating surfaces across the landscape, swales and gullies only active in the highest events, karst sinkholes that disconnect drainage areas, and floodplains that de-couple the hillslopes from the stream corridor. Results show that sediment connectivity is predicted for about 2% or more the watershed's area 37 days of the year, with the remaining days showing very little or no connectivity. Only 12.8 ± 0.7% of the gently rolling watershed shows sediment connectivity on the wettest day of the study year. Results also highlight the importance of urban/suburban sediment pathways in gently rolling watersheds, and dynamic and longitudinal distributions of sediment connectivity might be further investigated in future work. We suggest the method herein provides the modeler with an added tool to account for sediment transport criteria and has the potential to reduce computational costs in watershed erosion modeling.

  18. Modeling erosion and sedimentation coupled with hydrological and overland flow processes at the watershed scale

    Science.gov (United States)

    Kim, Jongho; Ivanov, Valeriy Y.; Katopodes, Nikolaos D.

    2013-09-01

    A novel two-dimensional, physically based model of soil erosion and sediment transport coupled to models of hydrological and overland flow processes has been developed. The Hairsine-Rose formulation of erosion and deposition processes is used to account for size-selective sediment transport and differentiate bed material into original and deposited soil layers. The formulation is integrated within the framework of the hydrologic and hydrodynamic model tRIBS-OFM, Triangulated irregular network-based, Real-time Integrated Basin Simulator-Overland Flow Model. The integrated model explicitly couples the hydrodynamic formulation with the advection-dominated transport equations for sediment of multiple particle sizes. To solve the system of equations including both the Saint-Venant and the Hairsine-Rose equations, the finite volume method is employed based on Roe's approximate Riemann solver on an unstructured grid. The formulation yields space-time dynamics of flow, erosion, and sediment transport at fine scale. The integrated model has been successfully verified with analytical solutions and empirical data for two benchmark cases. Sensitivity tests to grid resolution and the number of used particle sizes have been carried out. The model has been validated at the catchment scale for the Lucky Hills watershed located in southeastern Arizona, USA, using 10 events for which catchment-scale streamflow and sediment yield data were available. Since the model is based on physical laws and explicitly uses multiple types of watershed information, satisfactory results were obtained. The spatial output has been analyzed and the driving role of topography in erosion processes has been discussed. It is expected that the integrated formulation of the model has the promise to reduce uncertainties associated with typical parameterizations of flow and erosion processes. A potential for more credible modeling of earth-surface processes is thus anticipated.

  19. Quantification of short-term erosion rates using the cosmogenic radionuclide 7Be

    International Nuclear Information System (INIS)

    Jha, Abhinand

    2012-12-01

    The fallout radionuclides 137 Cs, 210 Pb ex are used widely for obtaining quantitative information on soil erosion and sediment redistribution rates within agricultural landscapes, over several spatial and temporal scales, and they are frequently seen to represent a valuable complement to conventional soil erosion measurement techniques. However, measurements of these radionuclides provide estimates of medium term (i.e. 40-100 years) soil erosion rates. The shorter-term perspective provided by the 7 Be method has the potential to estimate soil erosion rates associated with individual events or short periods. The 7 Be method has become increasingly relevant in an environment impacted by climate change, changing land use and other human activities. The present work establishes a mathematical model based on the physical processes of molecular diffusion and radioactive decay, to study the vertical behaviour of 7 Be in soils. This model was further used to quantify erosion rates for 12 individual erosional events over a period of two years at our study site in Muencheberg, Germany. The scope of the model was explored analytically as well as numerically for Pulselike fallout initial condition, zero concentration initial condition and exponential distribution initial condition. The model was fitted to more than 15 depth distributions and the resulting model parameter, effective diffusion coefficient D, is evaluated. In general diffusion coefficients estimated were of the order of 10 -12 -10 -13 m 2 s -1 for loamy to sandy soil types. Diffusion coefficients estimated for our study site were about 10 -13 m 2 s -1 . The soil analyses indicate that the diffusion coefficient D is not merely a fitting parameter, but is related to the physico-chemical properties of radionuclide transport in soils. The erosion rates estimated at tilled and no-till plots at our study site were between -2 and 0.3±0.5 kg m -2 -2.0±1.4 kg m -2 respectively. The magnitude of erosion rates estimated

  20. Quantification of short-term erosion rates using the cosmogenic radionuclide {sup 7}Be

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Abhinand

    2012-12-15

    The fallout radionuclides {sup 137}Cs, {sup 210}Pb{sub ex} are used widely for obtaining quantitative information on soil erosion and sediment redistribution rates within agricultural landscapes, over several spatial and temporal scales, and they are frequently seen to represent a valuable complement to conventional soil erosion measurement techniques. However, measurements of these radionuclides provide estimates of medium term (i.e. 40-100 years) soil erosion rates. The shorter-term perspective provided by the {sup 7}Be method has the potential to estimate soil erosion rates associated with individual events or short periods. The {sup 7}Be method has become increasingly relevant in an environment impacted by climate change, changing land use and other human activities. The present work establishes a mathematical model based on the physical processes of molecular diffusion and radioactive decay, to study the vertical behaviour of {sup 7}Be in soils. This model was further used to quantify erosion rates for 12 individual erosional events over a period of two years at our study site in Muencheberg, Germany. The scope of the model was explored analytically as well as numerically for Pulselike fallout initial condition, zero concentration initial condition and exponential distribution initial condition. The model was fitted to more than 15 depth distributions and the resulting model parameter, effective diffusion coefficient D, is evaluated. In general diffusion coefficients estimated were of the order of 10{sup -12}-10{sup -13} m{sup 2} s{sup -1} for loamy to sandy soil types. Diffusion coefficients estimated for our study site were about 10{sup -13} m{sup 2}s{sup -1}. The soil analyses indicate that the diffusion coefficient D is not merely a fitting parameter, but is related to the physico-chemical properties of radionuclide transport in soils. The erosion rates estimated at tilled and no-till plots at our study site were between <0.001-4.7{+-}0.4 kg m{sup -2} and

  1. Restorative Rehabilitation of a Patient with Dental Erosion

    OpenAIRE

    AlShahrani, Mohammed Thamer; Haralur, Satheesh B.; Alqarni, Mohammed

    2017-01-01

    Dental erosion is the chemical dissolution of the tooth structure. Factors like eating disorders and gastrointestinal diseases are recognized as intrinsic factors for dental erosion. Advanced stages of dental erosion extensively damage the tooth morphology, consequently affecting both esthetics and functions. Reports indicate the growing prevalence of erosion, and hence knowledge of restorative rehabilitation of tooth erosion is an integral part of the contemporary dental practice. This clini...

  2. A numerical model investigation of the formation and persistence of an erosion hotspot

    Science.gov (United States)

    Hansen, Jeff E.; Elias, Edwin; List, Jeffrey H.; Barnard, Patrick L.

    2011-01-01

    A Delft3D-SWAN coupled flow and wave model was constructed for the San Francisco Bight with high-resolution at 7 km-long Ocean Beach, a high-energy beach located immediately south of the Golden Gate, the sole entrance to San Francisco Bay. The model was used to investigate tidal and wave-induced flows, basic forcing terms, and potential sediment transport in an area in the southern portion of Ocean Beach that has eroded significantly over the last several decades. The model predicted flow patterns that were favorable for sediment removal from the area and net erosion from the surf-zone. Analysis of the forcing terms driving surf-zone flows revealed that wave refraction over an exposed wastewater outfall pipe between the 12 and 15 m isobaths introduces a perturbation in the wave field that results in erosion-causing flows. Modeled erosion agreed well with five years of topographic survey data from the area.

  3. Erosion resistance of pipe bends with bio-inspired internal surfaces

    Science.gov (United States)

    Zhang, Chengchun; Matar, Omar

    2013-11-01

    Guided by the structure of a shell surface, a bio-inspired surface is proposed to enhance the erosion resistance of pipe bends carrying crude-oil and sand in the turbulent flow regime. A comparison of the erosion rate between a smooth bend and the bio-inspired one is carried out using numerical simulations: large eddy simulations are used to simulate turbulence, and these are coupled to a discrete element method for the solid particles. The results indicate that the bio-inspired surface can control effectively the liquid-solid flow near the wall, and decrease the particle-wall force. This, then, leads to a reduction in the erosion rate brought about by the sand transported by the crude-oil in the pipe bend. The China Scholarship Council is gratefully acknowledged.

  4. 3D flow simulation of liquid lead in the erosion test facility for ADS materials

    International Nuclear Information System (INIS)

    Muscher, Heinrich; Kieser, Martin; Weisenburger, Alfons; Mueller, Georg

    2009-01-01

    Future nuclear reactor concepts, such as GEN IV or ADS use liquid lead for neutron multiplication and coolant purposes. The design concepts assumes that the structural material is in contact with the liquid metal at temperatures up to 600 C and a flow rate of 20 m/s. Therefore a significant effect of liquid metal corrosion/erosion is expected. The paper describes the fluid dynamical simulation of the ADS erosion test facility. Earlier studies on the laminar flow modeling were completed by introduction of transient behavior and extended to 3D-models. The results for liquid lead should be transferable to LBE (lead bismuth eutectic). Further work has to include a mass transport model for modeling of the global isothermal erosion rate of the structural material dependent on time (for liquid lead and LBE).

  5. Erosion risk assessment in the southern Amazon - Data Preprocessing, data base application and process based modelling

    Science.gov (United States)

    Schindewolf, Marcus; Herrmann, Marie-Kristin; Herrmann, Anne-Katrin; Schultze, Nico; Amorim, Ricardo S. S.; Schmidt, Jürgen

    2015-04-01

    The study region along the BR 16 highway belongs to the "Deforestation Arc" at the southern border of the Amazon rainforest. At the same time, it incorporates a land use gradient as colonization started in the 1975-1990 in Central Mato Grosso in 1990 in northern Mato Grosso and most recently in 2004-2005 in southern Pará. Based on present knowledge soil erosion is one of the key driver of soil degradation. Hence, there is a strong need to implement soil erosion control measures in eroding landscapes. Planning and dimensioning of such measures require reliable and detailed information on the temporal and spatial distribution of soil loss, sediment transport and deposition. Soil erosion models are increasingly used, in order to simulate the physical processes involved and to predict the effects of soil erosion control measures. The process based EROSION 3D simulation model is used for surveying soil erosion and deposition on regional catchments. Although EROSION 3D is a widespread, extensively validated model, the application of the model on regional scale remains challenging due to the enormous data requirements and complex data processing operations. In this context the study includes the compilation, validation and generalisation of existing land use and soil data in order to generate a consistent EROSION 3D input datasets. As a part of this process a GIS-linked data base application allows to transfer the original soil and land use data into model specific parameter files. This combined methodology provides different risk assessment maps for certain demands on regional scale. Besides soil loss and sediment transport, sediment pass over points into surface water bodies and particle enrichment can be simulated using the EROSION 3D model. Thus the estimation of particle bound nutrient and pollutant inputs into surface water bodies becomes possible. The study ended up in a user-friendly, timesaving and improved software package for the simulation of soil loss and

  6. Polymers Erosion and Contamination Experiment Being Developed

    Science.gov (United States)

    deGroh, Kim K.; Banks, Bruce A.; Barney-Barton, Elyse A.; Sechkar, Edward; Hunt, Patricia

    1999-01-01

    The Polymers Erosion and Contamination Experiment (PEACE) is currently being developed at the NASA Lewis Research Center by the Electro-Physics Branch in conjunction with students and faculty from Hathaway Brown School in Cleveland. The experiment is a Get Away Special Canister shuttle flight experiment sponsored by the American Chemical Society. The two goals of this experiment are (1) to measure ram atomic oxygen erosion rates of approximately 40 polymers that have potential use in space applications and (2) to validate a method for identifying sources of silicone contamination that occur in the shuttle bay. Equipment to be used in this flight experiment is shown in the schematic diagram. Spacecraft materials subjected to attack by atomic oxygen in the space environment experience significant degradation over the span of a typical mission. Therefore, learning the rates of atomic oxygen erosion of a wide variety of polymers would be of great benefit to future missions. PEACE will use two independent techniques to determine the atomic oxygen erosion rates of polymers. Large (1-in.-diameter) samples will be used for obtaining mass loss. Preflight and postflight dehydrated masses will be obtained, and the mass lost during flight will be determined. Small (0.5-in.-diameter) samples will be protected with isolated particles (such as NaCl crystals) and then exposed to the space environment. After flight, the protective particles will be removed (washed off) and atomic force microscopy (AFM) will be used to measure the erosion depth from protected mesas. Erosion depth measurements are more sensitive than traditional mass measurements and are very useful for materials with low erosion yields or with very low fluence missions.

  7. IN SITU MEASUREMENT OF BEDROCK EROSION

    Directory of Open Access Journals (Sweden)

    D. H. Rieke-Zapp

    2012-07-01

    Full Text Available While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are – if at all available – based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest

  8. In Situ Measurement of Bedrock Erosion

    Science.gov (United States)

    Rieke-Zapp, D. H.; Beer, A.; Turowski, J. M.; Campana, L.

    2012-07-01

    While long term erosion rates of bedrock material may be estimated by dating methods, current day erosion rates are - if at all available - based on rough estimates or on point measurements. Precise quantification of short term erosion rates are required to improve our understanding of short term processes, for input in landscape evolution models, as well as for studying the mechanics and efficiency of different erosion processes in varying geomorphological settings. Typical current day erosion rates in the European Alps range from sub-millimetre to several millimetres per year depending on the dominant erosion processes. The level of surveying accuracy required for recurring sub-millimetre to millimetre measurements in the field is demanding. A novel surveying setup for in-situ measurement of bedrock erosion was tested recently in three different locations in Switzerland. Natural bedrock was investigated in the Gornera gorge close to Zermatt. Further on, bedrock samples were installed in exposed locations in the Erlenbach research watershed close to Einsiedeln, and in the Illgraben debris flow channel, located in the Canton Schwyz and Valais, respectively. A twofold measurement approach was chosen for all locations. For the first setup control points providing an absolute reference frame for recurrent measurements were embedded close to the area of interest. Close range photogrammetry was applied to measure surface changes on the bedrock samples. The precision for surface measurements in the field was 0.1 mm (1 σ) and thus suitable for the application. The equipment needed for the surveys can easily be carried to the field. At one field site a structured light scanner was used along with the photogrammetric setup. Although the current generation of structured light scanners appeared less suitable for field application, data acquisition was much faster and checking the data for completeness in the field was straight forward. The latest generation of compact

  9. Microbial electrosynthetic cells

    Energy Technology Data Exchange (ETDEWEB)

    May, Harold D.; Marshall, Christopher W.; Labelle, Edward V.

    2018-01-30

    Methods are provided for microbial electrosynthesis of H.sub.2 and organic compounds such as methane and acetate. Method of producing mature electrosynthetic microbial populations by continuous culture is also provided. Microbial populations produced in accordance with the embodiments as shown to efficiently synthesize H.sub.2, methane and acetate in the presence of CO.sub.2 and a voltage potential. The production of biodegradable and renewable plastics from electricity and carbon dioxide is also disclosed.

  10. Soil erosion after forest fires in the Valencia region

    Science.gov (United States)

    González-Pelayo, Óscar; Keizer, Jan Jacob; Cerdà, Artemi

    2014-05-01

    24, 289-304. Fernández, C., Vega, J. A., Jiménez, E., Vieira, D. C. S., Merino, A., Ferreiro, A., Fonturbel, T. 2012. Seedingand mulching + seeding effects on post-fire runoff, soil erosion and species diversity in Galicia (NW Spain). Land Degradation & Development, 23: 150- 156. DOI 10.1002/ldr.1064 Gimeno-García, Andreu, V., Rubio, J.L. 2000. Changes in organic matter, nitrogen, phosphorus and cations in soils as a result of fire and water erosion in a Mediterranean landscape. European Journal of Soil Science 51, 201-210. Gimeno-García, E., Andreu, V.,, Rubio, J.L., 2007. Influence of vegetation recovery on water erosion at short and medium-term after experimental fires in a Mediterranean shrubland. Catena 69, 150-160. González-Pelayo, O, Andreu, V., Gimeno-García, E., Campo, J., Rubio, J.L. 2010a. Effects of fire and vegetation cover on hydrological characteristics of a Mediterranean shrubland soil. Hydrological Processes 24, 1504-1513. González-Pelayo, O., Andreu, V., Campo, J., Gimeno-García, E., Rubio, J.L. 2006. Hydrological Properties of Mediterranean Soils Burned with Different Fire Intensities. Catena 68 (2-3), 186-193. González-Pelayo, O., Andreu, V., Campo, J., Gimeno-García, E., Rubio, J.L. 2010b. Rainfall influence on plot-scale runoff and soil loss from repeated burning in a Mediterranean-shrub ecosystem, Valencia, Spain. Geomorphology 118, 444-452. Guénon, R., Vennetier, M., Dupuy, N., Roussos, S., Pailler, A., Gros, R. 2013. Trends in recovery of Mediterranean soil chemical properties and microbial activities after infrequent and frequent wildfires. Land Degradation & Development, 24: 115- 128. DOI 10.1002/ldr.1109 Guerrero, C., Mataix-Solera, J., Navarro-Pedreño, J., García-Orenes, F. Gómez, I. 2001. Different patterns of aggregate stability in burned and restored soils. Arid Land Research and Management 15, 163-171. Llovet, J., Bautista, S., Giovanardi, F., Vallejo, V. R., 1998. Sediment production in burned catchments of eastern

  11. Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

    Science.gov (United States)

    Chojnacki, Matthew; Banks, Maria; Urso, Anna

    2018-01-01

    Aeolian processes have likely been the predominant geomorphic agent for most of Mars’ history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low. PMID:29568719

  12. Wind-Driven Erosion and Exposure Potential at Mars 2020 Rover Candidate-Landing Sites

    Science.gov (United States)

    Chojnacki, Matthew; Banks, Maria; Urso, Anna

    2018-02-01

    Aeolian processes have likely been the predominant geomorphic agent for most of Mars' history and have the potential to produce relatively young exposure ages for geologic units. Thus, identifying local evidence for aeolian erosion is highly relevant to the selection of landing sites for future missions, such as the Mars 2020 Rover mission that aims to explore astrobiologically relevant ancient environments. Here we investigate wind-driven activity at eight Mars 2020 candidate-landing sites to constrain erosion potential at these locations. To demonstrate our methods, we found that contemporary dune-derived abrasion rates were in agreement with rover-derived exhumation rates at Gale crater and could be employed elsewhere. The Holden crater candidate site was interpreted to have low contemporary erosion rates, based on the presence of a thick sand coverage of static ripples. Active ripples at the Eberswalde and southwest Melas sites may account for local erosion and the dearth of small craters. Moderate-flux regional dunes near Mawrth Vallis were deemed unrepresentative of the candidate site, which is interpreted to currently be experiencing low levels of erosion. The Nili Fossae site displayed the most unambiguous evidence for local sand transport and erosion, likely yielding relatively young exposure ages. The downselected Jezero crater and northeast Syrtis sites had high-flux neighboring dunes and exhibited substantial evidence for sediment pathways across their ellipses. Both sites had relatively high estimated abrasion rates, which would yield young exposure ages. The downselected Columbia Hills site lacked evidence for sand movement, and contemporary local erosion rates are estimated to be relatively low.

  13. Erosion of an ancient mountain range, the Great Smoky Mountains, North Carolina and Tennessee

    Science.gov (United States)

    Matmon, A.; Bierman, P.R.; Larsen, J.; Southworth, S.; Pavich, M.; Finkel, R.; Caffee, M.

    2003-01-01

    Analysis of 10Be and 26Al in bedrock (n=10), colluvium (n=5 including grain size splits), and alluvial sediments (n=59 including grain size splits), coupled with field observations and GIS analysis, suggest that erosion rates in the Great Smoky Mountains are controlled by subsurface bedrock erosion and diffusive slope processes. The results indicate rapid alluvial transport, minimal alluvial storage, and suggest that most of the cosmogenic nuclide inventory in sediments is accumulated while they are eroding from bedrock and traveling down hill slopes. Spatially homogeneous erosion rates of 25 - 30 mm Ky-1 are calculated throughout the Great Smoky Mountains using measured concentrations of cosmogenic 10Be and 26Al in quartz separated from alluvial sediment. 10Be and 26Al concentrations in sediments collected from headwater tributaries that have no upstream samples (n=18) are consistent with an average erosion rate of 28 ?? 8 mm Ky-1, similar to that of the outlet rivers (n=16, 24 ?? 6 mm Ky-1), which carry most of the sediment out of the mountain range. Grain-size-specific analysis of 6 alluvial sediment samples shows higher nuclide concentrations in smaller grain sizes than in larger ones. The difference in concentrations arises from the large elevation distribution of the source of the smaller grains compared with the narrow and relatively low source elevation of the large grains. Large sandstone clasts disaggregate into sand-size grains rapidly during weathering and downslope transport; thus, only clasts from the lower parts of slopes reach the streams. 26Al/10Be ratios do not suggest significant burial periods for our samples. However, alluvial samples have lower 26Al/10Be ratios than bedrock and colluvial samples, a trend consistent with a longer integrated cosmic ray exposure history that includes periods of burial during down-slope transport. The results confirm some of the basic ideas embedded in Davis' geographic cycle model, such as the reduction of relief

  14. Studies about behavior of microbial degradation of organic compounds

    International Nuclear Information System (INIS)

    Ohtsuka, Makiko

    2003-02-01

    Some of TRU waste include organic compounds, thus these organic compounds might be nutrients for microbial growth at disposal site. This disposal system might be exposed to high alkali condition by cement compounds as engineering barrier material. In the former experimental studies, it has been supposed that microbial exist under pH = 12 and the microbial activity acclimated to high alkali condition are able to degrade asphalt under anaerobic condition. Microbes are called extremophile that exist in cruel habitat as high alkali or reductive condition. We know less information about the activity of extremophile, though any recent studies reveal them. In this study, the first investigation is metabolic pathway as microbial activity, the second is microbial degradation of aromatic compounds in anaerobic condition, and the third is microbial activity under high alkali. Microbial metabolic pathway consist of two systems that fulfill their function each other. One system is to generate energy for microbial activities and the other is to convert substances for syntheses of organisms' structure materials. As these systems are based on redox reaction between substances, it is made chart of the microbial activity region using pH, Eh, and depth as parameter, There is much report that microbe is able to degrade aromatic compounds under aerobic or molecular O 2 utilizing condition. For degradation of aromatic compounds in anaerobic condition, supplying electron acceptor is required. Co-metabolism and microbial consortia has important role, too. Alcalophile has individual transporting system depending Na + and acidic compounds contained in cell wall. Generating energy is key for survival and growth under high alkali condition. Co-metabolism and microbial consortia are effective for microbial degradation of aromatic compounds under high alkali and reductive condition, and utilizable electron acceptor and degradable organic compounds are required for keeping microbial activity and

  15. Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

    Science.gov (United States)

    E. M. Stacy; S. C. Hart; C. T. Hunsaker; D. W. Johnson; A. A. Berhe

    2015-01-01

    Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual...

  16. Probabilistic soil erosion modeling using the Erosion Risk Management Tool (ERMIT) after wildfires

    Science.gov (United States)

    P. R. Robichaud; W. J. Elliot; J. W. Wagenbrenner

    2011-01-01

    The decision of whether or not to apply post-fire hillslope erosion mitigation treatments, and if so, where these treatments are most needed, is a multi-step process. Land managers must assess the risk of damaging runoff and sediment delivery events occurring on the unrecovered burned hillslope. We developed the Erosion Risk Management Tool (ERMiT) to address this need...

  17. Predicting of soil erosion with regarding to rainfall erosivity and soil erodibility

    Science.gov (United States)

    Suif, Zuliziana; Razak, Mohd Amirun Anis Ab; Ahmad, Nordila

    2018-02-01

    The soil along the hill and slope are wearing away due to erosion and it can take place due to occurrence of weak and heavy rainfall. The aim of this study is to predict the soil erosion degree in Universiti Pertahanan Nasional Malaysia (UPNM) area focused on two major factor which is soil erodibility and rainfall erosivity. Soil erodibility is the possibilities of soil to detach and carried away during rainfall and runoff. The "ROM" scale was used in this study to determine the degree of soil erodibility, namely low, moderate, high, and very high. As for rainfall erosivity, the erosive power caused by rainfall that cause soil loss. A daily rainfall data collected from January to April was analyzed by using ROSE index classification to identify the potential risk of soil erosion. The result shows that the soil erodibilty are moderate at MTD`s hill, high at behind of block Lestari and Landslide MTD hill, and critical at behind the mess cadet. While, the highest rainfall erosivity was recorded in March and April. Overall, this study would benefit the organization greatly in saving cost in landslide protection as relevant authorities can take early measures repairing the most affected area of soil erosion.

  18. Does a more sophisticated storm erosion model improve probabilistic erosion estimates?

    NARCIS (Netherlands)

    Ranasinghe, R.W.M.R.J.B.; Callaghan, D.; Roelvink, D.

    2013-01-01

    The dependency between the accuracy/uncertainty of storm erosion exceedance estimates obtained via a probabilistic model and the level of sophistication of the structural function (storm erosion model) embedded in the probabilistic model is assessed via the application of Callaghan et al.'s (2008)

  19. Susceptibility of bovine dental enamel with initial erosion lesion to new erosive challenges.

    Science.gov (United States)

    Oliveira, Gabriela Cristina de; Tereza, Guida Paola Genovez; Boteon, Ana Paula; Ferrairo, Brunna Mota; Gonçalves, Priscilla Santana Pinto; Silva, Thiago Cruvinel da; Honório, Heitor Marques; Rios, Daniela

    2017-01-01

    This in vitro study evaluated the impact of initial erosion on the susceptibility of enamel to further erosive challenge. Thirty bovine enamel blocks were selected by surface hardness and randomized into two groups (n = 15): GC- group composed by enamel blocks without erosion lesion and GT- group composed by enamel blocks with initial erosion lesion. The baseline profile of each block was determined using the profilometer. The initial erosion was produced by immersing the blocks into HCl 0.01 M, pH 2.3 for 30 seconds, under stirring. The erosive cycling consisted of blocks immersion in hydrochloric acid (0.01 M, pH 2.3) for 2 minutes, followed by immersion in artificial saliva for 120 minutes. This procedure was repeated 4 times a day for 5 days, and the blocks were kept in artificial saliva overnight. After erosive cycling, final profile measurement was performed. Profilometry measured the enamel loss by the superposition of initial and final profiles. Data were analyzed by t-test (perosion on bovine dental enamel does not enhance its susceptibility to new erosive challenges.

  20. Lidar quantification of bank erosion in Blue Earth County, Minnesota.

    Science.gov (United States)

    Kessler, A C; Gupta, S C; Dolliver, H A S; Thoma, D P

    2012-01-01

    Sediment and phosphorus (P) transport from the Minnesota River Basin to Lake Pepin on the upper Mississippi River has garnered much attention in recent years. However, there is lack of data on the extent of sediment and P contributions from riverbanks vis-à-vis uplands and ravines. Using two light detection and ranging (lidar) data sets taken in 2005 and 2009, a study was undertaken to quantify sediment and associated P losses from riverbanks in Blue Earth County, Minnesota. Volume change in river valleys as a result of bank erosion amounted to 1.71 million m over 4 yr. Volume change closely followed the trend: the Blue Earth River > the Minnesota River at the county's northern edge > the Le Sueur River > the Maple River > the Watonwan River > the Big Cobb River > Perch Creek > Little Cobb River. Using fine sediment content (silt + clay) and bulk density of 37 bank samples representing three parent materials, we estimate bank erosion contributions of 48 to 79% of the measured total suspended solids at the mouth of the Blue Earth and the Le Sueur rivers. Corresponding soluble P and total P contributions ranged from 0.13 to 0.20% and 40 to 49%, respectively. Although tall banks (>3 m high) accounted for 33% of the total length and 63% of the total area, they accounted for 75% of the volume change in river valleys. We conclude that multitemporal lidar data sets are useful in estimating bank erosion and associated P contributions over large scales, and for riverbanks that are not readily accessible for conventional surveying equipment. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  1. Estimation of wind erosion from construction of a railway in arid Northwest China

    Directory of Open Access Journals (Sweden)

    Benli Liu

    2017-06-01

    Full Text Available A state-of-the-art wind erosion simulation model, the Wind Erosion Prediction System and the United States Environmental Protection Agency's AP 42 emission factors formula, were combined together to evaluate wind-blown dust emissions from various construction units from a railway construction project in the dry Gobi land in Northwest China. The influence of the climatic factors: temperature, precipitation, wind speed and direction, soil condition, protective measures, and construction disturbance were taken into account. Driven by daily and sub-daily climate data and using specific detailed management files, the process-based WEPS model was able to express the beginning, active, and ending phases of construction, as well as the degree of disturbance for the entire scope of a construction project. The Lanzhou-Xinjiang High-speed Railway was selected as a representative study because of the diversities of different climates, soil, and working schedule conditions that could be analyzed. Wind erosion from different working units included the building of roadbeds, bridges, plants, temporary houses, earth spoil and barrow pit areas, and vehicle transportation were calculated. The total wind erosion emissions, 7406 t, for the first construction area of section LXS-15 with a 14.877 km length was obtained for quantitative analysis. The method used is applicable for evaluating wind erosion from other complex surface disturbance projects.

  2. Dynamic Monte-Carlo modeling of hydrogen retention and chemical erosion from Tore Supra deposits

    International Nuclear Information System (INIS)

    Rai, A.; Schneider, R.; Warrier, M.; Roubin, P.; Martin, C.

    2009-01-01

    A multi-scale model has been developed to study the hydrogen retention [A. Rai, R. Schneider, M. Warrier, J. Nucl. Mater. 374 (2008) 304] and chemical erosion of porous graphite. To model the chemical erosion process due to thermal hydrogen ions, Kueppers cycle [J. Kueppers, Surf. Sci. Rep. 22 (1995) 249; M. Wittmann, J. Kueppers, J. Nucl. Mater. 227 (1996) 186] has been introduced. The model is applied to study hydrogen transport in deposits collected from the leading edge of neutralizers of Tore Supra. The effect of internal structure on chemical erosion is studied. The MD study [E. Salonen et al., J. Nucl. Mater. 290-293 (2001) 144] shows that the experimentally observed decrease of erosion yield at higher fluxes is due to the decrease of carbon collision cross-section at a surface due to shielding by hydrogen atom already present on the surface. Inspired by this study, a simple multi-scale model is developed to describe the flux dependence of chemical erosion. The idea is to use the local chemistry effect from the Kueppers model to calculate the hydrocarbon molecule formation process and then to find the release probability of the produced hydrocarbon based on the purely geometrical constraints. The model represents quite well the trends in experimental data.

  3. The June 2016 Australian East Coast Low: Importance of Wave Direction for Coastal Erosion Assessment

    Directory of Open Access Journals (Sweden)

    Thomas R. Mortlock

    2017-02-01

    Full Text Available In June 2016, an unusual East Coast Low storm affected some 2000 km of the eastern seaboard of Australia bringing heavy rain, strong winds and powerful wave conditions. While wave heights offshore of Sydney were not exceptional, nearshore wave conditions were such that beaches experienced some of the worst erosion in 40 years. Hydrodynamic modelling of wave and current behaviour as well as contemporaneous sand transport shows the east to north-east storm wave direction to be the major determinant of erosion magnitude. This arises because of reduced energy attenuation across the continental shelf and the focussing of wave energy on coastal sections not equilibrated with such wave exposure under the prevailing south-easterly wave climate. Narrabeen–Collaroy, a well-known erosion hot spot on Sydney’s Northern Beaches, is shown to be particularly vulnerable to storms from this direction because the destructive erosion potential is amplified by the influence of the local embayment geometry. We demonstrate the magnified erosion response that occurs when there is bi-directionality between an extreme wave event and preceding modal conditions and the importance of considering wave direction in extreme value analyses.

  4. Estimates of erosion on potato lands on krasnozems at Dorringo, NSW, using the caesium-137 technique

    International Nuclear Information System (INIS)

    Elliott, G.L.; Cole-Clark, B.E.

    1993-01-01

    Caesium-137 measurements have been made on soil samples taken from a grid pattern in a paddock used for three spring potato crops since 1966. Total erosion was estimated from these measurements and found to average 297 t ha -1 , equivalent to 98 t ha -1 per crop (allowing for erosion during the pasture phase). Comparative erosion estimates have been made from the results of single transect sampling in a paddock used for two potato crops and in one under permanent pasture. Results suggest erosion rates of 57 t ha -1 per crop in the former site and 0.09 t ha -1 year -1 in the latter site. An erosion rate of 100 t ha -1 per crop is at least 100 times the probable soil formation rate, implies an economic resource life of a maximum 600 years and involves a cost of lost nutrients of at least $3200 per hectare. These results strongly suggest a need to both develop and adopt land management practices which will substantially reduce both soil detachment and transport. 19 refs., 3 tabs., 8 figs

  5. Modeling of water erosion by seagis model. Case Watershed Dam Siliana

    International Nuclear Information System (INIS)

    Chabaan, Chayma

    2016-01-01

    water erosion is a complicated phenomenon, largely obvious in north Africa, especially in the watershed of Siliana, where natural factors and the aggressiveness of the environment do affect the loss of soil there, which characterized by a form so uneven with attitudes that vary from 700 to 1350 m rigid going from 5 to 10 pour cent and sometimes more. Moreover, it has drained with a thick hydrographic network. Generally, water erosion depends of the importance and the frequent agent factor of this erosion ( rain and streaming), soil type, the topography and the occupation of soil. The usage of mathematic models has to take on consideration of these parameters. The main objective of this work consist in developing put into affect a geomatic approach of stimulation which aims at estimate in time and space, the impact of the climate, and the soil occupation on the water erosion and the transportation of the sediments diversions into sliding of a small watershed. Locally, this approach allows evaluating the parameters of water erosion of SEAGIS model (USLE/RUSLE) to an extent that is identifies and drowing the emergency areas of intervention in the watershed of Siliana.

  6. Erosion and the limits to planetesimal growth

    Science.gov (United States)

    Krijt, S.; Ormel, C. W.; Dominik, C.; Tielens, A. G. G. M.

    2015-02-01

    Context. The coagulation of microscopic dust into planetesimals is the first step towards the formation of planets. The composition, size, and shape of the growing aggregates determine the efficiency of this early growth. In particular, it has been proposed that fluffy ice aggregates can grow very efficiently in protoplanetary disks, suffering less from the bouncing and radial drift barriers. Aims: While the collision velocity between icy aggregates of similar size is thought to stay below the fragmentation threshold, they may nonetheless lose mass from collisions with much smaller projectiles. As a result, erosive collisions have the potential to terminate the growth of pre-planetesimal bodies. We investigate the effect of these erosive collisions on the ability of porous ice aggregates to cross the radial drift barrier. Methods: We develop a Monte Carlo code that calculates the evolution of the masses and porosities of growing aggregates, while resolving the entire mass distribution at all times. The aggregate's porosity is treated independently of its mass, and is determined by collisional compaction, gas compaction, and eventually self-gravity compaction. We include erosive collisions and study the effect of the erosion threshold velocity on aggregate growth. Results: For erosion threshold velocities of 20-40 m s-1, high-velocity collisions with small projectiles prevent the largest aggregates from growing when they start to drift. In these cases, our local simulations result in a steady-state distribution, with most of the dust mass in particles with Stokes numbers close to unity. Only for the highest erosion threshold considered (60 m s-1) do porous aggregates manage to cross the radial drift barrier in the inner 10 AU of MMSN-like disks. Conclusions: Erosive collisions are more effective in limiting the growth than fragmentary collisions between similar-size particles. Conceivably, erosion limits the growth before the radial drift barrier, although the

  7. MISSE PEACE Polymers Atomic Oxygen Erosion Results

    Science.gov (United States)

    deGroh, Kim, K.; Banks, Bruce A.; McCarthy, Catherine E.; Rucker, Rochelle N.; Roberts, Lily M.; Berger, Lauren A.

    2006-01-01

    Forty-one different polymer samples, collectively called the Polymer Erosion and Contamination Experiment (PEACE) Polymers, have been exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for nearly 4 years as part of Materials International Space Station Experiment 2 (MISSE 2). The objective of the PEACE Polymers experiment was to determine the atomic oxygen erosion yield of a wide variety of polymeric materials after long term exposure to the space environment. The polymers range from those commonly used for spacecraft applications, such as Teflon (DuPont) FEP, to more recently developed polymers, such as high temperature polyimide PMR (polymerization of monomer reactants). Additional polymers were included to explore erosion yield dependence upon chemical composition. The MISSE PEACE Polymers experiment was flown in MISSE Passive Experiment Carrier 2 (PEC 2), tray 1, on the exterior of the ISS Quest Airlock and was exposed to atomic oxygen along with solar and charged particle radiation. MISSE 2 was successfully retrieved during a space walk on July 30, 2005, during Discovery s STS-114 Return to Flight mission. Details on the specific polymers flown, flight sample fabrication, pre-flight and post-flight characterization techniques, and atomic oxygen fluence calculations are discussed along with a summary of the atomic oxygen erosion yield results. The MISSE 2 PEACE Polymers experiment is unique because it has the widest variety of polymers flown in LEO for a long duration and provides extremely valuable erosion yield data for spacecraft design purposes.

  8. Mechanisms of erosion of atherosclerotic plaques.

    Science.gov (United States)

    Quillard, Thibaut; Franck, Grégory; Mawson, Thomas; Folco, Eduardo; Libby, Peter

    2017-10-01

    The present review explores the mechanisms of superficial intimal erosion, a common cause of thrombotic complications of atherosclerosis. Human coronary artery atheroma that give rise to thrombosis because of erosion differ diametrically from those associated with fibrous cap rupture. Eroded lesions characteristically contain few inflammatory cells, abundant extracellular matrix, and neutrophil extracellular traps (NETs). Innate immune mechanisms such as engagement of Toll-like receptor 2 (TLR2) on cultured endothelial cells can impair their viability, attachment, and ability to recover a wound. Hyaluronan fragments may serve as endogenous TLR2 ligands. Mouse experiments demonstrate that flow disturbance in arteries with neointimas tailored to resemble features of human eroded plaques disturbs endothelial cell barrier function, impairs endothelial cell viability, recruits neutrophils, and provokes endothelial cells desquamation, NET formation, and thrombosis in a TLR2-dependent manner. Mechanisms of erosion have received much less attention than those that provoke plaque rupture. Intensive statin treatment changes the characteristic of plaques that render them less susceptible to rupture. Thus, erosion may contribute importantly to the current residual burden of risk. Understanding the mechanisms of erosion may inform the development and deployment of novel therapies to combat the remaining atherothrombotic risk in the statin era.

  9. Solid particle erosion of polymers and composites

    Science.gov (United States)

    Friedrich, K.; Almajid, A. A.

    2014-05-01

    After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

  10. Water erosion risk prediction in eucalyptus plantations

    Directory of Open Access Journals (Sweden)

    Mayesse Aparecida da Silva

    2014-04-01

    Full Text Available Eucalyptus plantations are normally found in vulnerable ecosystems such as steep slope, soil with low natural fertility and lands that were degraded by agriculture. The objective of this study was to obtain Universal Soil Loss Equation (USLE factors and use them to estimate water erosion risk in regions with eucalyptus planted. The USLE factors were obtained in field plots under natural rainfall in the Rio Doce Basin, MG, Brazil, and the model applied to assess erosion risk using USLE in a Geographic Information System. The study area showed rainfall-runoff erosivity values from 10,721 to 10,642 MJ mm ha-1 h-1 yr-1. Some soils (Latosols had very low erodibility values (2.0 x 10-4 and 1.0 x 10-4t h MJ-1 mm-1, the topographic factor ranged from 0.03 to 10.57 and crop and management factor values obtained for native forest, eucalyptus and planted pasture were 0.09, 0.12 and 0.22, respectively. Water erosion risk estimates for current land use indicated that the areas where should receive more attention were mainly areas with greater topographic factors and those with Cambisols. Planning of forestry activities in this region should consider implementation of other conservation practices beyond those already used, reducing areas with a greater risk of soil erosion and increasing areas with very low risk.

  11. Evaluation of the serum zinc level in erosive and non-erosive oral lichen planus.

    Science.gov (United States)

    Gholizadeh, N; Mehdipour, M; Najafi, Sh; Bahramian, A; Garjani, Sh; Khoeini Poorfar, H

    2014-06-01

    Lichen planus is a chronic inflammatory immunologic-based disease involving skin and mucosa. This disease is generally divided into two categories: erosive and non-erosive. Many etiologic factors are deliberated regarding the disease; however, the disorders of immune system and the role of cytotoxic T-lymphocytes and monocytes are more highlighted. Zinc is an imperative element for the growth of epithelium and its deficiency induces the cytotoxic activity of T-helper2 cells, which seems to be associated with lichen planus. This study was aimed to evaluate the levels of serum zinc in erosive and non-erosive oral lichen planus (OLP) and to compare it with the healthy control group to find out any feasible inference. A total of 22 patients with erosive oral lichen planus, 22 patients with non erosive OLP and 44 healthy individuals as the control group were recruited in this descriptive-comparative study. All the participants were selected from the referees to the department of oral medicine, school of dentistry, Tabriz University of Medical Sciences. Serum zinc level was examined for all the individuals with liquid-stat kit (Beckman Instruments Inc.; Carlsbad, CA). Data were analyzed by adopting the ANOVA and Tukey tests, using SPSS 16 statistical software. The mean age of patients with erosive and non-erosive LP was 41.7 and 41.3 years, respectively. The mean age of the healthy control group was 34.4 years .The mean serum zinc levels in the erosive and non erosive lichen planus groups and control groups were 8.3 (1.15), 11.15 (0.92) and 15.74 (1.75) μg/dl respectively. The difference was statistically significant (poral lichen planus. This finding may probably indicate the promising role of zinc in development of oral lichen planus.

  12. Factors of the Development of Water Erosion in the Zone of Recreation Activity in the Ol'khon Region

    Science.gov (United States)

    Znamenskaya, T. I.; Vanteeva, J. V.; Solodyankina, S. V.

    2018-02-01

    Specific features of water erosion of thin soils under conditions of nonpercolative water regime and intense recreational loads were studied in the Ol'khon region (Irkutsk oblast). An experiment on the transfer of terrigenous particles under the impact of rainfall simulation was performed. A thorough description of landscape characteristics affecting water erosion development was made. As a result, a multiple regression equation linking the transported matter with the slope steepness, projective cover of vegetation, the degree of vegetation degradation, and the fine sand content in the upper soil horizon was developed; the multiple correlation coefficient R reached 0.86. On this basis, the map of water erosion assessment for the study area was compiled with the use of landscape and topographic maps. The maximum intensity of water erosion is typical of the anthropogenically transformed landscapes on steep slopes with the low vegetative cover on the mountainous noncalcareous steppe soils and on thin loamy sandy surface-gravelly chestnut-like soils.

  13. Hydrologic Drivers of Soil Organic Carbon Erosion and Burial: Insights from a Spatially-explicit Model of a Degraded Landscape at the Calhoun Critical Zone Observatory

    Science.gov (United States)

    Dialynas, Y. G.; Bras, R. L.; Richter, D. D., Jr.

    2017-12-01

    Soil erosion and burial of organic material may constitute a substantial sink of atmospheric CO2. Attempts to quantify impacts of soil erosion on the soil-atmosphere C exchange are limited by difficulties in accounting for the fate of eroded soil organic carbon (SOC), a key factor in estimating of the net effect of erosion on the C cycle. Processes that transport SOC are still inadequately represented in terrestrial carbon (C) cycle models. This study investigates hydrologic controls on SOC redistribution across the landscape focusing on dynamic feedbacks between watershed hydrology, soil erosional processes, and SOC burial. We use tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially-explicit model of SOC dynamics coupled with a physically-based hydro-geomorphic model. tRIBS-ECO systematically accounts for the fate of eroded SOC across the watershed: Rainsplash erosion and sheet erosion redistribute SOC from upland sites to depositional environments, altering depth-dependent soil biogeochemical properties in diverse soil profiles. Eroded organic material is transferred with sediment and can be partially oxidized upon transport, or preserved from decomposition by burial. The model was applied in the Calhoun Critical Zone Observatory (CZO), a site that is recovering from some of the most serious agricultural erosion in North America. Soil biogeochemical characteristics at multiple soil horizons were used to initialize the model and test performance. Remotely sensed soil moisture data (NASA SMAP) were used for model calibration. Results show significant rates of hydrologically-induced burial of SOC at the Calhoun CZO. We find that organic material at upland eroding soil profiles is largely mobilized by rainsplash erosion. Sheet erosion mainly drives C transport in lower elevation clayey soils. While SOC erosion and deposition rates declined with recent reforestation at the study site, the

  14. Microbial enhanced oil recovery and compositions therefor

    Science.gov (United States)

    Bryant, Rebecca S.

    1990-01-01

    A method is provided for microbial enhanced oil recovery, wherein a combination of microorganisms is empirically formulated based on survivability under reservoir conditions and oil recovery efficiency, such that injection of the microbial combination may be made, in the presence of essentially only nutrient solution, directly into an injection well of an oil bearing reservoir having oil present at waterflood residual oil saturation concentration. The microbial combination is capable of displacing residual oil from reservoir rock, which oil may be recovered by waterflooding without causing plugging of the reservoir rock. Further, the microorganisms are capable of being transported through the pores of the reservoir rock between said injection well and associated production wells, during waterflooding, which results in a larger area of the reservoir being covered by the oil-mobilizing microorganisms.

  15. Transport Statistics - Transport - UNECE

    Science.gov (United States)

    Sustainable Energy Statistics Trade Transport Themes UNECE and the SDGs Climate Change Gender Ideas 4 Change UNECE Weekly Videos UNECE Transport Areas of Work Transport Statistics Transport Transport Statistics About us Terms of Reference Meetings and Events Meetings Working Party on Transport Statistics (WP.6

  16. Soil erosion in Iran: Issues and solutions

    Science.gov (United States)

    Hamidreza Sadeghi, Seyed; Cerdà, Artemi

    2015-04-01

    Iran currently faces many soil erosion-related problems (see citations below). These issues are resulted from some inherent characteristic and anthropogenic triggering forces. Nowadays, the latter plays more important rule to accelerate the erosion with further emphasis on soil erosion-prone arid and semi arid regions of the country. This contribution attempts to identify and describe the existing main reasons behind accelerated soil erosion in Iran. Appropriate solutions viz. structural and non-structural approaches will be then advised to combat or minimise the problems. Iran can be used as a pilot research site to understand the soil erosion processes in semiarid, arid and mountainous terrain and our research will review the scientific literature and will give an insight of the soil erosion rates in the main factors of the soil erosion in Iran. Key words: Anthropogenic Erosion, Land Degradation; Sediment Management; Sediment Problems Acknowledgements The research projects GL2008-02879/BTE, LEDDRA 243857 and PREVENTING AND REMEDIATING DEGRADATION OF SOILS IN EUROPE THROUGH LAND CARE (RECARE)FP7-ENV-2013- supported this research. References Aghili Nategh, N., Hemmat, A., & Sadeghi, M. (2014). Assessing confined and semi-confined compression curves of highly calcareous remolded soil amended with farmyard manure. Journal of Terramechanics, 53, 75-82. Arekhi, S., Bolourani, A. D., Shabani, A., Fathizad, H., Ahamdy-Asbchin, S. 2012. Mapping Soil Erosion and Sediment Yield Susceptibility using RUSLE, Remote Sensing and GIS (Case study: Cham Gardalan Watershed, Iran). Advances in Environmental Biology, 6(1), 109-124. Arekhi, S., Shabani, A., Rostamizad, G. 2012. Application of the modified universal soil loss equation (MUSLE) in prediction of sediment yield (Case study: Kengir Watershed, Iran). Arabian Journal of Geosciences, 5(6), 1259-1267.Sadeghi, S. H., Moosavi, V., Karami, A., Behnia, N. 2012. Soil erosion assessment and prioritization of affecting factors at plot

  17. An assessment of disruption erosion in ITER environment

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1994-01-01

    The behavior of divertor materials during a major disruption in ITER is very important for the successful and reliable operation of the reactor. Erosion of material surfaces due to the thermal energy dump can severely limit the lifetime of the plasma facing components therefore degrading reactor economic feasibility. A comprehensive numerical model recently developed is used in this analysis in which all major physical processes taking place during plasma-material interactions are included. Models to account for material thermal evolution, plasma-vapor interaction physics, and models for hydrodynamic radiation transport in the developed vapor cloud are implemented in a self-consistent manner to realistically assess the disruption damage. The extent of the self-protection from the developed vapor cloud in front of the incoming plasma particles is critically important in determining the overall disruption lifetime. The aim of this study is to estimate the divertor lifetime for a range of reactor conditions. Candidate materials such as beryllium and graphite are both considered in this analysis. The dependence of the divertor disruption lifetime on the characteristics of plasma-vapor interaction zone for incident plasma ions and electrons is analyzed and discussed. The effect of uncertainties in reactor disruption conditions on the overall divertor erosion lifetime is also analyzed

  18. Cellular Automata for Modeling the field-scale erosion

    International Nuclear Information System (INIS)

    Diaz Suarez, Jorge; Bagarotti Marin, Angel; Ruiz Perez, Maria Elena

    2008-01-01

    Full text: The Cellular Automaton (CA) is a system used discrete dynamic modeling of many physical systems. Their fundamental properties are the interaction at the local level, homogeneity and parallelism. It has been used as a secondary for the simulation of large systems where the use of equations in partial derivatives is complex and costly from the computational point of view. On the other hand, the high complexity of spatial interaction in the processes involved in the erosion-transport-deposition of sediments at field level, considerably limiting the use of base models physics. The objective of this study is to model the main processes involved in erosion water supply of soils through the use of the CAMELot system, based on an extension of the original paradigm of the CA. The CAMELot system has been used in the simulation of systems of large spatial extent, where the laws of local interaction between automata have a deep physical sense. This system guarantees both the input of the necessary specifications and simulation in parallel, as the visualization and the general management of the system. They are exposed to each of the submodels used in it and the overall dynamics of the system is analyzed. (author)

  19. Erosion protection of uranium tailings impoundments

    International Nuclear Information System (INIS)

    Walters, W.H.; Skaggs, R.L.; Foley, M.G.; Beedlow, P.A.

    1986-09-01

    Pacific Northwest Laboratory (PNL) prepared this report to assist in the design and review of erosion protection works for decommissioned uranium tailings impoundments. The major causes of erosion over the long-term decommissioning period are from rainfall-runoff (overland flow) and stream channel flooding. The method of protection recommended for the impoundment side slopes and site drainage channels is rock riprap. Combinations of vegetation and rock mulch are recommended for the top surface. The design methods were developed from currently available procedures supplemented by field, laboratory, and mathematical model studies performed by PNL. Guidelines for the placement of riprap, inspection, and maintenance are presented. Other subjects discussed are rock selection and testing, slope stability, and overland erosion modeling

  20. Microbial accumulation of uranium

    International Nuclear Information System (INIS)

    Zhang Wei; Dong Faqin; Dai Qunwei

    2005-01-01

    The mechanism of microbial accumulation of uranium and the effects of some factors (including pH, initial uranium concentration, pretreatment of bacteria, and so on) on microbial accumulation of uranium are discussed briefly. The research direction and application prospect are presented. (authors)

  1. MICROBIAL FUEL CELL

    DEFF Research Database (Denmark)

    2008-01-01

    A novel microbial fuel cell construction for the generation of electrical energy. The microbial fuel cell comprises: (i) an anode electrode, (ii) a cathode chamber, said cathode chamber comprising an in let through which an influent enters the cathode chamber, an outlet through which an effluent...

  2. Microbial control of pollution

    Energy Technology Data Exchange (ETDEWEB)

    Fry, J C; Gadd, G M; Herbert, R A; Jones, C W; Watson-Craik, I A [eds.

    1992-01-01

    12 papers are presented on the microbial control of pollution. Topics covered include: bioremediation of oil spills; microbial control of heavy metal pollution; pollution control using microorganisms and magnetic separation; degradation of cyanide and nitriles; nitrogen removal from water and waste; and land reclamation and restoration.

  3. Constraints on Water Reservoir Lifetimes From Catchment-Wide 10Be Erosion Rates—A Case Study From Western Turkey

    Science.gov (United States)

    Heineke, Caroline; Hetzel, Ralf; Akal, Cüneyt; Christl, Marcus

    2017-11-01

    The functionality and retention capacity of water reservoirs is generally impaired by upstream erosion and reservoir sedimentation, making a reliable assessment of erosion indispensable to estimate reservoir lifetimes. Widely used river gauging methods may underestimate sediment yield, because they do not record rare, high-magnitude events and may underestimate bed load transport. Hence, reservoir lifetimes calculated from short-term erosion rates should be regarded as maximum values. We propose that erosion rates from cosmogenic 10Be, which commonly integrate over hundreds to thousands of years, are useful to complement short-term sediment yield estimates and should be employed to estimate minimum reservoir lifetimes. Here we present 10Be erosion rates for the drainage basins of six water reservoirs in Western Turkey, which are located in a tectonically active region with easily erodible bedrock. Our 10Be erosion rates for these catchments are high, ranging from ˜170 to ˜1,040 t/km2/yr. When linked to reservoir volumes, they yield minimum reservoir lifetimes between 25 ± 5 and 1,650 ± 360 years until complete filling, with four reservoirs having minimum lifespans of ≤110 years. In a neighboring region with more resistant bedrock and less tectonic activity, we obtain much lower catchment-wide 10Be erosion rates of ˜33 to ˜95 t/km2/yr, illustrating that differences in lithology and tectonic boundary conditions can cause substantial variations in erosion even at a spatial scale of only ˜50 km. In conclusion, we suggest that both short-term sediment yield estimates and 10Be erosion rates should be employed to predict the lifetimes of reservoirs.

  4. Disc valve for sampling erosive process streams

    Science.gov (United States)

    Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

    1986-01-07

    A four-port disc valve is described for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of [alpha] silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions. 1 fig.

  5. Numerical Modelling and Prediction of Erosion Induced by Hydrodynamic Cavitation

    Science.gov (United States)

    Peters, A.; Lantermann, U.; el Moctar, O.

    2015-12-01

    The present work aims to predict cavitation erosion using a numerical flow solver together with a new developed erosion model. The erosion model is based on the hypothesis that collapses of single cavitation bubbles near solid boundaries form high velocity microjets, which cause sonic impacts with high pressure amplitudes damaging the surface. The erosion model uses information from a numerical Euler-Euler flow simulation to predict erosion sensitive areas and assess the erosion aggressiveness of the flow. The obtained numerical results were compared to experimental results from tests of an axisymmetric nozzle.

  6. Wind and water erosion control on semiarid lands

    International Nuclear Information System (INIS)

    Siddoway, F.H.

    1980-01-01

    Commercial crop production on semiarid lands is difficult because insufficient water is often present to manage the system effectively. Erosion control presents the major management problem. The factors contributing to wind erosion and their interaction have been quantified into a wind erosion equation. The control of wind erosion through agronomic alteration of the various factors is discussed. The quantification and control of water erosion is also discussed with respect to the Universal Soil Loss Equation. Radioisotopes tracers have been used in conjunction with these erosion equations to measure soil losses. (author)

  7. Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

    Energy Technology Data Exchange (ETDEWEB)

    Hu, H.X. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Zheng, Y.G., E-mail: ygzheng@imr.ac.c [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China); Qin, C.P. [State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Science, 62 Wencui Road, Shenyang 110016 (China)

    2010-10-15

    Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90{sup o}, and almost equal to that of the Inconel 600 at impacting angle of 30{sup o}. Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

  8. Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

    International Nuclear Information System (INIS)

    Hu, H.X.; Zheng, Y.G.; Qin, C.P.

    2010-01-01

    Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90 o , and almost equal to that of the Inconel 600 at impacting angle of 30 o . Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

  9. Mapping Soil Erosion Factors and Potential Erosion Risk for the National Park "Central Balkan"

    Science.gov (United States)

    Ilieva, Diliana; Malinov, Ilia

    2014-05-01

    Soil erosion is widely recognised environmental problem. The report aims at presenting the main results from assessment and mapping of the factors of sheet water erosion and the potential erosion risk on the territory of National Park "Central Balkan". For this purpose, the Universal Soil Loss Equation (USLE) was used for predicting soil loss from erosion. The influence of topography (LS-factor) and soil erodibility (K-factor) was assessed using small-scale topographic and soil maps. Rainfall erosivity (R-factor) was calculated from data of rainfalls with amounts exceeding 9.5 mm from 14 hydro-meteorological stations. The values of the erosion factors (R, K and LS) were presented for the areas of forest, sub-alpine and alpine zones. Using the methods of GIS, maps were plotted presenting the area distribution among the classes of the soil erosion factors and the potential risk in the respective zones. The results can be used for making accurate decisions for soil conservation and sustainable land management in the park.

  10. Microbial mat structures in profile: The Neoproterozoic Sonia Sandstone, Rajasthan, India

    Science.gov (United States)

    Samanta, Pradip; Mukhopadhyay, Soumik; Mondal, Anudeb; Sarkar, Subir

    2011-01-01

    Ubiquitous microorganisms, especially cyanobacteria preferably grow on the sediment surface thereby producing microbial mats. In the absence of grazers and bioturbators, microbial mat is a unique feature of the Proterozoic. Most of the papers so far published described a wide variety of bed surface microbial mat structures with rare illustrations from sections perpendicular to bedding. Nonetheless, bed surface exposures are relatively rare in rock records. This limitation of bed surface exposures in rock records suggest that a study of microbial mats in bed-across sections is needed. The 60 m thick coastal marine interval of the Sonia Sandstone Formation is bounded between two terrestrial intervals, a transgressive lag at the base and an unconformity at the top, and has been chosen for exploration of microbial mat structures in bed-across sections. A wide variety of microbial mat-induced structures in bed-across sections are preserved within the coastal interval of the Sonia Sandstone. Though many of these structures are similar in some aspects with bed surface structures, some of those presented here are new. The palaeogeographic range of these microbial structures extends from supralittoral to neritic. Diagenetic alterations of microbial mats produce pyrite and those zones are suitable for the preservation of microbial remains. SEM and EDAX analyses show fossil preservation of filamentous microbial remains that confirm the presence of microbial mats within the coastal interval of the Sonia Sandstone. Effects of proliferation of microbial mats in the siliciclastic depositional setting are numerous. The mat-cover on sediment surfaces hinders reworking and/or erosion of the sediments thereby increases the net sedimentation rate. Successive deposition and preservation of thick microbial mat layer under reducing environments should have a great potential for hydrocarbon production and preservation and therefore these Proterozoic formations could be a target for

  11. Modeling erosion of unsaturated compacted bentonite by groundwater flow; pinhole erosion test case

    International Nuclear Information System (INIS)

    Laurila, T.; Sane, P.; Olin, M.; Koskinen, K.

    2012-01-01

    Document available in extended abstract form only. Erosion of compacted clay material by water flow is a critical factor affecting the performance of radioactive waste confinement. Our emphasis in this work is the buffer of KBS-3V concept, proposed to be compacted MX-80 bentonite. Unsaturated erosion occurs during the saturation phase of the EBS, and the main quantity of interest is the total buffer mass carried away by a groundwater flow that induces erosion by forming piping channels near the buffer/rock interface. The purpose of this work is to provide modeling tools to support erosion experiments. Role of modeling is first to interpret experimental observations in terms of processes, and to estimate robustness of experimental results. Secondly, we seek to scale up results from the laboratory scale, particularly to time scales longer than those experimentally accessible. We have performed modeling and data analysis pertaining to tests of unsaturated clay erosion. Pinhole experiments were used to study this erosion case. The main differences to well-understood pinhole erosion tests are that the material is strongly swelling and that the water flow is not determined by the pressure head but by the total flux. Groundwater flow in the buffer is determined by the flux because pressure losses occur overwhelmingly in the surrounding rock, not in the piping channel. We formulate a simple model that links an effective solid diffusivity -based swelling model to erosion by flow on the solid/liquid interface. The swelling model is similar in concept to that developed at KTH, but simpler. Erosion in the model is caused by laminar flow in the pinhole, and happens in a narrow region at the solid/liquid interface where velocity and solid volume fraction overlap. The erosion model can be mapped to erosion by wall shear, and can thus be considered as extension of that classic erosion model. The main quantity defining the behavior of clay erosion in the model is the ratio of

  12. Erosion potential from Missoula floods in the Pasco Basin, Washington

    International Nuclear Information System (INIS)

    Craig, R.G.; Hanson, J.P.

    1985-12-01

    Localities within the Pasco Basin preserve evidence of Missoula floods. Deposits are 46% sand-sized, 36% gravel-sized, and 18% finer than sand-sized. Mean thickness is 39 meters. High water marks at Wallula Gap require a discharge of approximately 12.5 Mcms. At Sentinel Gap, the slope-area method shows that the high water marks require a discharge of 34.6 Mcms. Since this discharge greatly exceeds any estimated for Missoula floods, there must have been backwater ponding from Wallula Gap. Projecting the slope of the water surface at the upper end of Wallula Gap to the downstream cross section at Gable Mountain leads to a discharge of 9.5 Mcms at Sentinel Gap. The HEC-6 steady state code and four sediment transport equations were applied. Assuming sand-sized particles, DuBoys function estimated 4 to 9 meters of scour. Yang's equation estimated 3 to 4 meters of scour. These are a minimum. A hydrograph synthesized for the boundaries of the Pasco Basin shows the maxima of the flood would occur after 90 h at Sentinel Gap, and at 114 h at Wallula Gap. The 200 areas will remain inundated for four days and six hours. With a quasi-dynamic sediment transport computation, HEC-6 scour estimates range from 0.61 meters to 0.915 meters. This is a minimum amount and erosion is highly variable suggesting reworking of sediment. The Meyer-Peter Meuller equations show less than 1 meter of net scour in the 200 areas. More extensive erosion was achieved during particular time steps of this analysis suggesting that sediment re-working would occur

  13. Erosion potential from Missoula floods in the Pasco Basin, Washington

    Energy Technology Data Exchange (ETDEWEB)

    Craig, R.G.; Hanson, J.P.

    1985-12-01

    Localities within the Pasco Basin preserve evidence of Missoula floods. Deposits are 46% sand-sized, 36% gravel-sized, and 18% finer than sand-sized. Mean thickness is 39 meters. High water marks at Wallula Gap require a discharge of approximately 12.5 Mcms. At Sentinel Gap, the slope-area method shows that the high water marks require a discharge of 34.6 Mcms. Since this discharge greatly exceeds any estimated for Missoula floods, there must have been backwater ponding from Wallula Gap. Projecting the slope of the water surface at the upper end of Wallula Gap to the downstream cross section at Gable Mountain leads to a discharge of 9.5 Mcms at Sentinel Gap. The HEC-6 steady state code and four sediment transport equations were applied. Assuming sand-sized particles, DuBoys function estimated 4 to 9 meters of scour. Yang's equation estimated 3 to 4 meters of scour. These are a minimum. A hydrograph synthesized for the boundaries of the Pasco Basin shows the maxima of the flood would occur after 90 h at Sentinel Gap, and at 114 h at Wallula Gap. The 200 areas will remain inundated for four days and six hours. With a quasi-dynamic sediment transport computation, HEC-6 scour estimates range from 0.61 meters to 0.915 meters. This is a minimum amount and erosion is highly variable suggesting reworking of sediment. The Meyer-Peter Meuller equations show less than 1 meter of net scour in the 200 areas. More extensive erosion was achieved during particular time steps of this analysis suggesting that sediment re-working would occur.

  14. Ash formation, deposition, corrosion, and erosion in conventional boilers

    Energy Technology Data Exchange (ETDEWEB)

    Benson, S.A.; Jones, M.L. [Univ. of North Dakota, Grand Forks, ND (United States)

    1995-12-01

    The inorganic components (ash-forming species) associated with coals significantly affect boiler design, efficiency of operation, and lifetimes of boiler parts. During combustion in conventional pulverized fuel boilers, the inorganic components are transformed into inorganic gases, liquids, and solids. This partitioning depends upon the association of the inorganic components in the coal and combustion conditions. The inorganic components are associated as mineral grains and as organically associated elements, and these associations of inorganic components in the fuel directly influence their fate upon combustion. Combustion conditions, such as temperature and atmosphere, influence the volatility and the interaction of inorganic components during combustion and gas cooling, which influences the state and size composition distribution of the particulate and condensed ash species. The intermediate species are transported with the bulk gas flow through the combustion systems, during which time the gases and entrained ash are cooled. Deposition, corrosion, and erosion occur when the ash intermediate species are transported to the heat-transfer surface, react with the surface, accumulate, sinter, and develop strength. Research over the past decade has significantly advanced understanding of ash formation, deposition, corrosion, and erosion mechanisms. Many of the advances in understanding and predicting ash-related issues can be attributed to advanced analytical methods to determine the inorganic composition of fuels and the resulting ash materials. These new analytical techniques have been the key to elucidation of the mechanisms of ash formation and deposition. This information has been used to develop algorithms and computer models to predict the effects of ash on combustion system performance.

  15. The water erosion processes in the retreat erosive of cliff on soft rocks in the province of Cadiz (Spain)

    International Nuclear Information System (INIS)

    Rendon Aragon, J. J.; Gracia Prieto, F. J.; Rio Rodriguez, L. del

    2009-01-01

    The littoral cliffs on soft materials of the Atlantic Cadiz coast show an important activity of the fresh water erosion processes, sometimes even more significant than the marine erosion processes. The connection of the lower cliffs with sandy beaches favours aeolian sand invasion, which fills previous rills and reduces the water erosion intensity by increasing infiltration. Cliff retreat and rill erosion measurement by using erosion sticks has shown very variables values, most of them higher than the estimated error of the employed methods. This indicates the existence of other factors influencing the distribution of water erosion processes along these cliffs, which have to be studied through different techniques. (Author) 5 refs.

  16. Erosions of the Petrous Temporal Bone

    African Journals Online (AJOL)

    tumours of the parotid gland; tumours of the paranasal sinuses; and tumours of ... showed severe erosion of the anterior and posterior walls and floor of the external .... sphenoid sinus, the pituitary fossa, and the greater and lesser wings of the ...

  17. Natural Erosion of Sandstone as Shape Optimisation.

    Science.gov (United States)

    Ostanin, Igor; Safonov, Alexander; Oseledets, Ivan

    2017-12-11

    Natural arches, pillars and other exotic sandstone formations have always been attracting attention for their unusual shapes and amazing mechanical balance that leave a strong impression of intelligent design rather than the result of a stochastic process. It has been recently demonstrated that these shapes could have been the result of the negative feedback between stress and erosion that originates in fundamental laws of friction between the rock's constituent particles. Here we present a deeper analysis of this idea and bridge it with the approaches utilized in shape and topology optimisation. It appears that the processes of natural erosion, driven by stochastic surface forces and Mohr-Coulomb law of dry friction, can be viewed within the framework of local optimisation for minimum elastic strain energy. Our hypothesis is confirmed by numerical simulations of the erosion using the topological-shape optimisation model. Our work contributes to a better understanding of stochastic erosion and feasible landscape formations that could be found on Earth and beyond.

  18. Alleviating gizzard erosion with Hepasan ® - Provisional ...

    African Journals Online (AJOL)

    Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. DOWNLOAD FULL TEXT Open Access DOWNLOAD FULL TEXT Subscription or Fee Access. Alleviating gizzard erosion with Hepasan® - Provisional Communication. K Boa-Amponsem, A Osei-Somuah. Full Text:.

  19. Identifying conservation hotspots using tillage erosion modeling

    Science.gov (United States)

    Tillage operations redistribute soil within agricultural landscapes due to deviations in the quantity of soil moved during tillage. Tillage erosion is the net loss or accumulation of soil at any spot within an agricultural landscape due to soil being directly moved by tillage; it is a dominant erosi...

  20. Slope stability and erosion control: Ecotechnological solutions

    NARCIS (Netherlands)

    Norris, J.E.; Stokes, A.; Mickovski, S.B.; Cammeraat, E.; van Beek, R.; Nicoll, B.C.; Achim, A.

    2008-01-01

    This book is designed to assist the civil and geotechnical engineer, geomorphologist, forester, landscape architect or ecologist in choosing ecotechnological solutions for slopes that are prone to a variety of mass movements e.g. shallow failure or erosion. Within this book, the 'engineer' is used

  1. Modeling Edge Effects of Tillage Erosion

    Science.gov (United States)

    Tillage erosion has been recognized as an important factor in redistribution of soil over time and in the development of morphological changes within agricultural fields. Field borders, fences, and vegetated strips that interrupt soil fluxes lead to the creation topographic discontinuities or lynche...

  2. Hydrogeological And Geotechnical Investigations Of Gully Erosion ...

    African Journals Online (AJOL)

    Consequently, hydrogeological and geotechnical studies of gully erosion sites were carried out in order to provide information on the genesis and continual expansion of gullies in the area. The results indicate that gullies are located in the upper aquifer of the Benin Formation (Coastal Plain Sands). The estimated hydraulic ...

  3. Is dental erosion really a problem?

    Science.gov (United States)

    Schlueter, N; Jaeggi, T; Lussi, A

    2012-09-01

    Dental erosion is the non-carious dental substance loss induced by direct impact of exogenous or endogenous acids. It results in a loss of dental hard tissue, which can be serious in some groups, such as those with eating disorders, in patients with gastroesophageal reflux disease, and also in persons consuming high amounts of acidic drinks and foodstuffs. For these persons, erosion can impair their well-being, due to changes in appearance and/or loss of function of the teeth, e.g., the occurrence of hypersensitivity of teeth if the dentin is exposed. If erosion reaches an advanced stage, time- and money-consuming therapies may be necessary. The therapy, in turn, poses a challenge for the dentist, particularly if the defects are diagnosed at an advanced stage. While initial and moderate defects can mostly be treated non- or minimally invasively, severe defects often require complex therapeutic strategies, which often entail extensive loss of dental hard tissue due to preparatory measures. A major goal should therefore be to diagnose dental erosion at an early stage, to avoid functional and esthetic impairments as well as pain sensations and to ensure longevity of the dentition.

  4. Coastal erosion and accretion rates in Greece

    Science.gov (United States)

    Foteinis, Spyros; Papadopoulos, Costas; Koutsogiannaki, Irini; Synolakis, Costas

    2010-05-01

    Erosion threatens many coastal regions of Greece. Anthropogenic changes of landforms such as coastal roads built on even narrow beaches, sand mining for construction, poor design of coastal structures that interfere with sediment, and dams without sediment bypasses have significantly reduced beach widths. We present erosion rates for different beaches, some of which are in sensitive ecosystems, otherwise "protected" by local and EU ordinances. By comparing inferences of beach widths in varying intervals from 1933 to 2006, we infer that the construction of dams in Acheloos river in western Greece, built in a faraonic attempt to partially divert its flows to eastern Greece, this is responsible for up to 20m/year erosion rates observed in certain locales in the Acheloos delta. More characteristic erosion rates in the region are ~ 2m/year. By contrast, there appears rapid accretion of up to 4m/year in the beaches around the Nestos delta in northern Greece (Papadopoulos, 2009). In beaches that are not near large river deltas, erosion rates range from 0.5m/year to 1m/year. While we have not done comprehensive comparisons among coastlines with different levels of coastal development, it does appear that rapid coastal development correlates well with erosion rates. The underlying problem is the complete lack of any semblance of coastal zone management in Greece and substandard design of coastal structures, which are often sited without any measurements of waves and currents offshore (Synolakis et al, 2008). Beach maintenance remains an exotic concept for most local authorities, who invariably prefer to build hard coastal structures to "protect" versus nourish, siting lack of experience with nourishment and "environmental" concerns. In certain cases, choices are dictated by costs, the larger the cost the easier the project gets approved by regulatory authorities, hence the preference for concrete or rubble structures. We conclude that, unless urgent salvage measures are

  5. Spatial Patterns of Long-Term Erosion Rates Beneath the Marine West Antarctic Ice Sheet: Insights into the Physics of Continental Scale Glacial Erosion from a Comparison with the Ice-Velocity Field

    Science.gov (United States)

    Howat, I. M.; Tulaczyk, S.; Mac Gregor, K.; Joughin, I.

    2001-12-01

    As part of the effort to build quantitative models of glacial erosion and sedimentation, it is particularly important to construct scaled relations between erosion, transport, and sedimentation rates and appropriate glaciological variables (e.g., ice velocity). Recent acquisition of bed topography and ice velocity data for the marine West Antarctic Ice Sheet (WAIS)[Joughin et al., 1999; Lythe et al., in press] provides an unprecedented opportunity to investigate continental-scale patterns of glacial erosion and their relationship to the ice velocity field. Utilizing this data, we construct a map of estimated long-term erosion rates beneath the WAIS. In order to calculate long-term erosion rates from the available data, we assume that: (1) the ice sheet has been present for ~5 mill. years, (2) the initial topography beneath the WAIS was that of a typical ( ~200 m.b.s.l.) continental shelf, and (3) the present topography is near local isostatic equilibrium (Airy type). The map of long-term erosion rates constructed in this fashion shows an intriguing pattern of relatively high rates (of the order of 0.1 mm/yr) concentrated beneath modern ice stream tributaries (ice velocity ~100 m/yr), but much lower erosion rates (of the order of 0.01 mm/yr) beneath both the modern fast-moving ice streams ( ~400 m/yr.) and the slow-moving parts of the ice sheet ( ~10 m/yr). This lack of clear correlation between the estimated erosion rates and ice velocity is somewhat unexpected given that both observational and theoretical studies have shown that bedrock erosion rates beneath mountain glaciers can often be calculated by multiplying the basal sliding velocity by a constant (typically of the order of ~10^-4)(Humphrey and Raymond, 1993 and Mac Gregor et al., 2000). We obtain an improved match between estimated erosion rates and bed topography by calculating erosion rates using horizontal gradients within the ice velocity field rather than the magnitude of ice velocity, as consistent

  6. Urban Runoff: Model Ordinances for Erosion and Sediment Control

    Science.gov (United States)

    The model ordinance in this section borrows language from the erosion and sediment control ordinance features that might help prevent erosion and sedimentation and protect natural resources more fully.

  7. Molybdenum erosion measurements in Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, W.R. [Sandia National Labs., Albuquerque, NM (United States); LaBombard, B.; Lipshultz, B.; Pappas, D.; Pitcher, C.S. [Massachusetts Inst. of Tech., Cambridge, MA (United States); McCracken, G.M. [JET Joint Undertaking, Abingdon (United Kingdom)

    1998-05-01

    Erosion of molybdenum was measured on a set of 21 tiles after a run campaign of 1,090 shots in the Alcator C-Mod tokamak. The net erosion of molybdenum, was determined from changes in the depth of a thin chromium marker layer measured by Rutherford backscattering. Net Mo erosion was found to be approximately 150 nm near the outer divertor strike point, and much less everywhere else. Gross erosion rates by sputtering were estimated using ion energies and fluxes obtained from Langmuir probe measurements of edge-plasma conditions. Predicted net erosion using calculated gross erosion with prompt redeposition and measured net erosion agree within a factor of 3. Sputtering by boron and molybdenum impurities dominates erosion.

  8. Mapping Soil Erosion in a Quaternary Catchment in Eastern Cape ...

    African Journals Online (AJOL)

    Temp

    2017-04-06

    Apr 6, 2017 ... Keywords: Geographic Information System; Remote Sensing; Soil Erosion; Vegetation Indices ... Soil erosion is considered one of the world's most critical ... the spatial extent of the problem (Le Roux et al., 2007) in other ...

  9. Thermomechanical Erosion Modelling of Baydaratskaya Bay, Russia with COSMOS

    NARCIS (Netherlands)

    Pearson, S.G.; Lubbad, R; Le, T.M.H.; Nairn, Rob

    2016-01-01

    Rapid coastal erosion threatens Arctic coastal infrastructure, including communities and industrial installations. Erosion of permafrost depends on numerous processes, including thermal and mechanical behaviour of frozen and unfrozen soil, nearshore hydrodynamics, atmospheric forcing, and the

  10. Three procedures for estimating erosion from construction areas

    International Nuclear Information System (INIS)

    Abt, S.R.; Ruff, J.F.

    1978-01-01

    Erosion from many mining and construction sites can lead to serious environmental pollution problems. Therefore, erosion management plans must be developed in order that the engineer may implement measures to control or eliminate excessive soil losses. To properly implement a management program, it is necessary to estimate potential soil losses from the time the project begins to beyond project completion. Three methodologies are presented which project the estimated soil losses due to sheet or rill erosion of water and are applicable to mining and construction areas. Furthermore, the three methods described are intended as indicators of the state-of-the-art in water erosion prediction. The procedures herein do not account for gully erosion, snowmelt erosion, wind erosion, freeze-thaw erosion or extensive flooding

  11. Onshore Wind Speed Modulates Microbial Aerosols along an Urban Waterfront

    Directory of Open Access Journals (Sweden)

    M. Elias Dueker

    2017-11-01

    Full Text Available Wind blowing over aquatic and terrestrial surfaces produces aerosols, which include microbial aerosols. We studied the effect of onshore wind speeds on aerosol concentrations as well as total and culturable microbial aerosols (bacterial and viral at an urban waterfront (New York, NY, United States of America. We used two distinct methods to characterize microbial aerosol responses to wind speed: A culture-based exposure-plate method measuring viable bacterial deposition near-shore (CFU accumulation rate; and a culture-independent aerosol sampler-based method measuring total bacterial and viral aerosols (cells m−3 air. While ambient coarse (>2 µm and fine (0.3–2 µm aerosol particle number concentrations (regulated indicators of air quality decreased with increasing onshore wind speeds, total and depositing culturable bacterial aerosols and total viral aerosols increased. Taxonomic identification of the 16S rDNA of bacterial aerosol isolates suggested both terrestrial and aquatic sources. Wind appears to increase microbial aerosol number concentrations in the near-shore environment by onshore transport at low wind speeds (<4 m s−1, and increased local production and transport of new microbial aerosols from adjacent water surfaces at higher wind speeds (>4 m s−1. This study demonstrates a wind-modulated microbial connection between water and air in the coastal urban environment, with implications for public health management and urban microbial ecology.

  12. Water erosion of dystrophic Red Latosols (Oxisols

    Directory of Open Access Journals (Sweden)

    Joaquim Ernesto Bernardes Ayer

    2015-06-01

    Full Text Available In their natural state, Latosols (Oxisols present great stability and resistance to erosion, being the most abundant and used soils for farming and cattle raising activities in southern Minas Gerais State, Brazil. However, along the last one hundred years, they have been submitted to intensive cultivation and managements which favor water erosion. This study aimed to estimate the water erosion rates of dystrophic Red Latosols from the Revised Universal Soil Loss Equation, compared with the soil loss tolerance limits, and assess the impact on water erosion of the managements more common in the region, by alternative conservation management simulation. Soil loss tolerance limits ranged from 8.94 Mg ha-1 year-1 to 9.99 Mg ha-1 year-1, with the study area presenting a susceptibility of soil loss of 23.86 Mg year-1, with an average rate of 8.40 Mg ha-1 year-1, corresponding to 34.80 % of the area with values above the soil loss tolerance limit. The biggest annual losses occur in areas with use and management of eucalyptus grown downhill (30.67 Mg ha-1 year-1 and pasture under continuous occupancy (11.10 Mg ha-1 year-1. However, when the average loss per type of use is considered, the areas more susceptible to water erosion are those with potato and eucalyptus crops, grown downhill, and those in bare soil. Nevertheless, in the simulated conservation management scenario, the average losses would be drastically reduced (8.40 Mg ha-1 year-1 to 2.84 Mg ha-1 year-1 and only 4.00 % of the area with soil loss would remain above the tolerance limits.

  13. The determination of risk areas for muddy floods based on a worst-case erosion modelling

    Science.gov (United States)

    Saathoff, Ulfert; Schindewolf, Marcus; Annika Arévalo, Sarah

    2013-04-01

    Soil erosion and muddy floods are a frequently occurring hazard in the German state of Saxony, because of the topography and the high relief energy together with the high proportion of arable land. Still, the events are rather heterogeneously distributed and we do not know where damage is likely to occur. The goal of this study is to locate hot spots for the risk of muddy floods, with the objective to prevent high economic damage in future. We applied a soil erosion and deposition map of Saxony, calculated with the process based soil erosion model EROSION 3D. This map shows the potential soil erosion and transported sediment for worst case soil conditions and a 10 year rain storm event. Furthermore, a map of the current landuse in the state is used. From the landuse map, we extracted those areas that are especially vulnerable to muddy floods, like residential and industrial areas, infrastructural facilities (e.g. power plants, hospitals) and highways. In combination with the output of the soil erosion model, the amount of sediment, that enters each single landuse entity, is calculated. Based on this data, a state-wide map with classified risks is created. The results are furthermore used to identify the risk of muddy floods for each single municipality in Saxony. The results are evaluated with data of real occurred muddy flood events with documented locations during the period between 2000 and 2010. Additionally, plausibility tests are performed for selected areas (examination of landuse, topography and soil). The results prove to be plausible and most of the documented events can be explained by the modelled risk map. The created map can be used by different institutions like city and traffic planners, to estimate the risk of muddy flood occurrence at specific locations. Furthermore, the risk map can serve insurance companies to evaluate the insurance risk of a building. To make them easily accessible, the risk map will be published online via a web GIS

  14. Littoral transport studies along west coast of India - A reivew

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.; Wagle, B.G.; Sugimori, Y.

    an important role in deciding the areas of coastal erosion and accretion, in shaping and orienting coastal landforms and finally in the evolution of the coast. Hence, in the analysis of coastal erosion-accretion problem, for the development of harbour... and construction of coastal structures, the direction, amount and behaviour of long-term average shore drift is of vital importance. Littoral transport is defined as the movement of sediments in the near shore zone by waves and currents. Littoral transport...

  15. Extrusion and erosion of bentonite buffer material in a flow-through, horizontal, artificial fracture system

    International Nuclear Information System (INIS)

    Schatz, Timothy; Kanerva, Noora; Martikainen, Jari

    2012-01-01

    terms of flow velocity, are plotted in Figure 2. The overall mass loss rates for the tests with the highest levels of observed erosion, i.e., the tests conducted under the most dilute conditions, appear to be well-correlated to flow velocity. On the other hand, for those tests conducted under slightly less dilute conditions, clear attenuation in mass loss relative to the bounding erosion rate was observed. This attenuation can be attributed to solution composition effects independently, as well as in combination with material composition effects. Such effects indicate that the use of a bounding erosion rate to estimate mass loss anywhere below a stability limit will lead to conservative predictions. Another aspect of the extrusion/erosion behavior of bentonite buffer material in intersecting fractures with possible impact on long-term safety considerations is in regard to bentonite extrusion as an additional barrier to radionuclide release. Assuming radionuclides are available, such species would migrate by diffusion through the buffer material and by advective and dispersive transport through intersecting fractures. Therefore, a zone of extruded buffer material in the fractures could provide an additional limit on radionuclide migration [Borrelli and Ahn 2008]. In every test in the artificial fracture systems, both erosive and non-erosive, emplaced buffer material extruded into the fracture and was observed to be impermeable to water flowing in the fracture. In other words the zone of extruded buffer material forms an extended diffusive barrier around the intersecting fracture/buffer interface. (authors)

  16. Tectonic controls of Holocene erosion in a glaciated orogen

    OpenAIRE

    Adams, Byron A.; Ehlers, Todd A.

    2018-01-01

    Recent work has highlighted a strong, worldwide, glacial impact of orogen erosion rates over the last 2 Ma. While it may be assumed that glaciers increased erosion rates when active, the degree to which past glaciations influence Holocene erosion rates through the adjustment of topography is not known. In this study, we investigate the influence of long-term tectonic and post-glacial topographic controls on erosion in a glaciated orogen, the Olympic Mountains, USA. We present 14 new 10Be and ...

  17. Photogrammetric techniques for across-scale soil erosion assessment

    OpenAIRE

    Eltner, Anette

    2016-01-01

    Soil erosion is a complex geomorphological process with varying influences of different impacts at different spatio-temporal scales. To date, measurement of soil erosion is predominantly realisable at specific scales, thereby detecting separate processes, e.g. interrill erosion contrary to rill erosion. It is difficult to survey soil surface changes at larger areal coverage such as field scale with high spatial resolution. Either net changes at the system outlet or remaining traces after the ...

  18. Erosion and corrosion of nuclear power plant materials

    International Nuclear Information System (INIS)

    1994-01-01

    This conference is composed of 23 papers, grouped in 3 sessions which main themes are: analysis of corrosion and erosion damages of nuclear power plant equipment and influence of water chemistry, temperature, irradiations, metallurgical and electrochemical factors, flow assisted cracking, stress cracking; monitoring and control of erosion and corrosion in nuclear power plants; susceptibility of structural materials to erosion and corrosion and ways to improve the resistance of materials, steels, coatings, etc. to erosion, corrosion and cracking

  19. Comparison of CFD simulations with experimental Jet Erosion Tests results

    OpenAIRE

    Mercier, F.; Bonelli, S.; Pinettes, P.; Golay, F.; Anselmet, F.; Philippe, P.

    2014-01-01

    The Jet Erosion Test (JET) is an experimental device increasingly used to quantify the resistance of soils to erosion. This resistance is characterised by two geotechnical parameters: the critical shear stress and the erosion coefficient. The JET interpretation model of Hanson and Cook (2004) provides an estimation of these erosion parameters. But Hanson's model is simplified, semi-empirical and several assumed hypotheses can be discussed. Our aim is to determine the relevance of the JET inte...

  20. Observation and measurement of erosion-corrosion in nuclear plants influence of chemical conditioning

    International Nuclear Information System (INIS)

    Bodmer, M.; Svoboda, R.; Ziffermayer, G.

    1984-01-01

    The erosion-corrosion caused by wet steam leads to considerable damage of certain components of the thermal cycle and, the metallic oxides which are formed are carried by the circulating fluid and form deposits particularly on heat exchangers. This paper describes the measurements and the observations techniques that were used. The experimental data permits to quantify the material resistance as well as the transportation of oxydes during the successive periodes during which a modification of both the conception and the material were introduced. The analysis of trace quantities of Fe, Cr, Ni, CO... permit to determine the attack of various materials as well as the transportation of the respective oxides. The analysis of the circulating fluid and the measurements of the respective quantities of deposits allows to evaluate the calculations of transport, deposit and oxides removal. The erosion-corrosion phenomenon is dependent upon the environment. A modification of the conditioning (higher pH in PWR, use of oxidizing agents in BWR) permits only a limited reduction of erosion-corrosion and may even present some disadvantages [fr

  1. Spatial and Temporal Responses of Soil Erosion to Climate Change Impacts in a Transnational Watershed in Southeast Asia

    Directory of Open Access Journals (Sweden)

    Pham Quy Giang

    2017-03-01

    Full Text Available It has been widely predicted that Southeast Asia is among the regions facing the most severe climate change impacts. Despite this forecast, little research has been published on the potential impacts of climate change on soil erosion in this region. This study focused on the impact of climate change on spatial and temporal patterns of soil erosion in the Laos–Vietnam transnational Upper Ca River Watershed. The Soil and Water Assessment Tool (SWAT coupled with downscaled global climate models (GCMs was employed for simulation. Soil erosion in the watershed was mostly found as “hill-slope erosion”, which occurred seriously in the upstream area where topography is dominated by numerous steep hills with sparse vegetation cover. However, under the impact of climate change, it is very likely that soil erosion rate in the downstream area will increase at a higher rate than in its upstream area due to a greater increase in precipitation. Seasonally, soil erosion is predicted to increase significantly in the warmer and wetter climate of the wet season, when higher erosive power of an increased amount and intensity of rainfall is accompanied by higher sediment transport capacity. The results of this study provide useful information for decision makers to plan where and when soil conservation practice should be focused.

  2. Soil erosion assessment on hillslope of GCE using RUSLE model

    Indian Academy of Sciences (India)

    Md. Rabiul Islam

    2018-05-22

    May 22, 2018 ... A vegetation density available on these plots is measured ... Finally, erosion prediction is computed based on the RUSLE model in ... which is lower compared to the C value from the soil erosion ..... Comparison of rainfall erosivity factor (R) value. ...... Vorovencii I and Muntean D 2012 Evaluation of super-.

  3. Validation of a probabilistic post-fire erosion model

    Science.gov (United States)

    Pete Robichaud; William J. Elliot; Sarah A. Lewis; Mary Ellen Miller

    2016-01-01

    Post-fire increases of runoff and erosion often occur and land managers need tools to be able to project the increased risk. The Erosion Risk Management Tool (ERMiT) uses the Water Erosion Prediction Project (WEPP) model as the underlying processor. ERMiT predicts the probability of a given amount of hillslope sediment delivery from a single rainfall or...

  4. Dental approach to erosive tooth wear in gastroesophageal reflux ...

    African Journals Online (AJOL)

    2014-06-02

    Jun 2, 2014 ... Objective: To summarize the diagnostic protocol and treatment of dental erosion due to GERD. Methods: A Medline ..... reflux in children with cerebral palsy and its relationship to erosion of ... phate (ACP) on root surface hypersensitivity. Operative ... Lussi A. Dental erosion clinical diagnosis and case.

  5. Erosion Modeling Analysis For Modified DWPF SME Tank

    International Nuclear Information System (INIS)

    LEE, SI

    2004-01-01

    In support of an erosion evaluation for the modified cooling coil guide and its supporting structure in the DWPF SME vessel, a computational model was developed to identify potential sites of high erosion using the same methodology established by previous work. The erosion mechanism identified in the previous work was applied to the evaluation of high erosion locations representative of the actual flow process in the modified coil guide of the SME vessel, abrasive erosion which occurs by high wall shear of viscous liquid. The results show that primary locations of the highest erosion due to the abrasive wall erosion are at the leading edge of the guide, external surface of the insert plate, the tank floor next to the insert plate of the coil guide support, and the upstream lead-in plate. The present modeling results show a good comparison between the original and the modified cases in terms of high erosion sites, as well as the degree of erosion and the calculated shear stress. Wall she ar of the tank floor is reduced by about 30 per cent because of the new coil support plate. Calculations for the impeller speed lower than 103 rpm in the SME showed similar erosion patterns but significantly reduced wall shear stresses and reduced overall erosion. Comparisons of the 103 rpm results with SME measurements indicated that no significant erosion of the tank floor in the SME is to be expected. Thus, it is recommended that the agitator speed of SME does not exceed 103 rpm

  6. Assessing soil erosion risk in the Tillabery landscape, Niger ...

    African Journals Online (AJOL)

    The results show that soil erosion output scenarios predict greater soil erosion in the study area from 2070 onwards. They suggest that human disturbance and topographic factors are the main impact factors in the affected areas. Key words: Tillabéry landscape (Niger), sheet and rill erosion modelling, data mining.

  7. Acoustic measurements of soil-pipeflow and internal erosion

    Science.gov (United States)

    Internal erosion of soil pipes can lead to embankment failures, landslides, and gully erosion. Therefore, non-intrusive methods are needed to detect and monitor soil pipeflow and the resulting internal erosion. This paper presents a laboratory study using both active and passive acoustic techniques ...

  8. WinDAM C earthen embankment internal erosion analysis software

    Science.gov (United States)

    Two primary causes of dam failure are overtopping and internal erosion. For the purpose of evaluating dam safety for existing earthen embankment dams and proposed earthen embankment dams, Windows Dam Analysis Modules C (WinDAM C) software will simulate either internal erosion or erosion resulting f...

  9. Development Of Rainfall Erosivity Map For Nigeria | Ogedengbe ...

    African Journals Online (AJOL)

    The indices were used to develop a rainfall erosivity map or Nigeria. The map reveals that Nigeria may be broadly divided into five major erosion risk zones. The south-western part is generally in the low erosion zone, with the exception of the coastal portion of Lagos, Ondo, Edo and Delta states. The south-east and central ...

  10. Multivariate erosion risk assessment of lateritic badlands of Birbhum ...

    Indian Academy of Sciences (India)

    Erosion risk; soil erosion; sediment yield; multivariate analysis; GIS. J. Earth Syst. Sci. 121, No. ... ers are threatened by excessive soil loss by water. To reach that goal the ... nacle erosion, bare soil cover, barren waste land, tunnels and ...

  11. Experiments on Erosion of Mud from the Danish Wadden Sea

    DEFF Research Database (Denmark)

    Johansen, C.; Larsen, Torben; Petersen, O.

    1994-01-01

    Experiments on erosion and consolidation of natural cohesive sediments from the harbour of Esbjerg located in the Danish Watten Sea were conducted using a rotating annular flume. The objective of the paper is to describe the erosion rate of deposited beds and relate the erosion rate...

  12. Pressure and velocity dependence of flow-type cavitation erosion

    CSIR Research Space (South Africa)

    Auret, JG

    1993-12-01

    Full Text Available Previous results on the influence of water pressure and velocity on flow-type cavitations erosion, i.e. an increase in erosion rate with increasing velocity and peaking of erosion rate as a function of pressure, were confirmed by measurements with a...

  13. A longitudinal study of tooth erosion in adolescents.

    NARCIS (Netherlands)

    El Aidi, H.; Bronkhorst, E.M.; Truin, G.J.

    2008-01-01

    Incidence studies on tooth erosion among adolescents are scarce. This longitudinal study aimed at estimating the prevalence, incidence, progression, and distribution of erosion in young adolescents over a 1.5-year period. Erosion at baseline was present in 32.2% of the 622 children (mean age, 11.9

  14. Evolution of microbial pathogens

    National Research Council Canada - National Science Library

    DiRita, Victor J; Seifert, H. Steven

    2006-01-01

    ... A. Hogan vvi ■ CONTENTS 8. Evolution of Pathogens in Soil Rachel Muir and Man-Wah Tan / 131 9. Experimental Models of Symbiotic Host-Microbial Relationships: Understanding the Underpinnings of ...

  15. Microbial hotspots and hot moments in soil

    Science.gov (United States)

    Kuzyakov, Yakov; Blagodatskaya, Evgenia

    2015-04-01

    Soils are the most heterogeneous parts of the biosphere, with an extremely high differentiation of properties and processes within nano- to macroscales. The spatial and temporal heterogeneity of input of labile organics by plants creates microbial hotspots over short periods of time - the hot moments. We define microbial hotspots as small soil volumes with much faster process rates and much more intensive interactions compared to the average soil conditions. Such hotspots are found in the rhizosphere, detritusphere, biopores (including drilosphere) and on aggregate surfaces, but hotspots are frequently of mixed origin. Hot moments are short-term events or sequences of events inducing accelerated process rates as compared to the averaged rates. Thus, hotspots and hot moments are defined by dynamic characteristics, i.e. by process rates. For this hotspot concept we extensively reviewed and examined the localization and size of hotspots, spatial distribution and visualization approaches, transport of labile C to and from hotspots, lifetime and process intensities, with a special focus on process rates and microbial activities. The fraction of active microorganisms in hotspots is 2-20 times higher than in the bulk soil, and their specific activities (i.e. respiration, microbial growth, mineralization potential, enzyme activities, RNA/DNA ratio) may also be much higher. The duration of hot moments in the rhizosphere is limited and is controlled by the length of the input of labile organics. It can last a few hours up to a few days. In the detritusphere, however, the duration of hot moments is regulated by the output - by decomposition rates of litter - and lasts for weeks and months. Hot moments induce succession in microbial communities and intense intra- and interspecific competition affecting C use efficiency, microbial growth and turnover. The faster turnover and lower C use efficiency in hotspots counterbalances the high C inputs, leading to the absence of strong

  16. Synthetic Electric Microbial Biosensors

    Science.gov (United States)

    2017-06-10

    domains and DNA-binding domains into a single protein for deregulation of down stream genes of have been favored [10]. Initially experiments with... Germany DISTRIBUTION A. Approved for public release: distribution unlimited.   Talk title: “Synthetic biology based microbial biosensors for the...toolbox” in Heidelberg, Germany Poster title: “Anaerobic whole cell microbial biosensors” Link: http://phdsymposium.embl.org/#home   September, 2014

  17. The erosion and erosion products of tungsten and carbon based materials bombarded by high energy pulse electron beam

    International Nuclear Information System (INIS)

    Liu Xiang; Zhang Fu; Xu Zengyu; Liu Yong; Yoshida, N.; Noda, N.

    2002-01-01

    In this paper, the erosion behaviors and erosion products of tungsten and some carbon based materials, such as graphite, C/C composite and B 4 C/Cu functionally graded material, were investigated by using a pulse electron beam to simulate the vertical displacement events (VDE) process. The authors will focus on the forms and differences of erosion products among these testing materials, and make clear to their erosion mechanisms

  18. Erosion/redeposition analysis : status of modeling and code validation for semi-detached tokamak edge plasmas

    International Nuclear Information System (INIS)

    Brooks, J. N.

    1999-01-01

    We are analyzing erosion and tritium codeposition for ITER, DIII-D, and other devices with a focus on carbon divertor and metallic wall sputtering, for detached and semi-detached edge plasmas. Carbon chemical-sputtering hydrocarbon-transport is computed in detail using upgraded models for sputtering yields, species, and atomic and molecular processes. For the DIII-D analysis this includes proton impact and dissociative recombination for the full methane and higher hydrocarbon chains. Several mixed material (Si-C doping and Be/C) effects on erosion are examined. A semi-detached reactor plasma regime yields peak net wall erosion rates of ∼1.0 (Be), ∼0.3 (Fe), and ∼0.01 (W) cm/burn-yr, and ∼50 cm/burn-yr for a carbon divertor. Net carbon erosion is dominated by chemical sputtering in the ∼1-3 eV detached plasma zone. Tritium codeposition in divertor-sputtered redeposited carbon is high (∼10-20 g-T/1000 s ). Silicon and beryllium mixing tends to reduce carbon erosion. Initial hydrocarbon transport calculations for the DIII-D DiMES-73 detached plasma experiment show a broad spectrum of redeposited molecules with ∼90% redeposition fraction

  19. Long-term erosion and re-deposition of carbon in the divertor region of JT-60U

    International Nuclear Information System (INIS)

    Gotoh, Y.; Tanabe, T.; Ishimoto, Y.; Masaki, K.; Arai, T.; Kubo, H.; Tsuzuki, K.; Miya, N.

    2006-01-01

    Erosion and redeposition profiles of carbon tiles used in the W-shaped divertor of JT-60U with all carbon plasma facing wall are studied. The inner divertor is mostly covered by carbon redeposited layers, while the outer divertor mostly eroded. In the dome region, the erosion dominates on the inner dome-wing, while redeposited on the outer dome-wing. The redeposited layers on the outer dome-wing show very clear columnar structures indicating local carbon transport form the outer divertor to the outer dome-wing. The weight gain by the redeposition extrapolated to the whole divertor area is 0.55 kg. Since the extrapolated total erosion is about 0.33 kg, the remaining 0.22 kg must be originated from the main chamber erosion. Significant amount of the redeposition is caused locally by multiple processes of erosion, ionization and prompt redeposition toward inboard direction owing to gyration along magnetic filed line. This inboard transport is one of the reasons for small redeposition on the plasma shadowed area of the W shaped divertor of JT-60U with pumping slots placed at the bottoms side

  20. Microbial bioinformatics 2020.

    Science.gov (United States)

    Pallen, Mark J

    2016-09-01

    Microbial bioinformatics in 2020 will remain a vibrant, creative discipline, adding value to the ever-growing flood of new sequence data, while embracing novel technologies and fresh approaches. Databases and search strategies will struggle to cope and manual curation will not be sustainable during the scale-up to the million-microbial-genome era. Microbial taxonomy will have to adapt to a situation in which most microorganisms are discovered and characterised through the analysis of sequences. Genome sequencing will become a routine approach in clinical and research laboratories, with fresh demands for interpretable user-friendly outputs. The "internet of things" will penetrate healthcare systems, so that even a piece of hospital plumbing might have its own IP address that can be integrated with pathogen genome sequences. Microbiome mania will continue, but the tide will turn from molecular barcoding towards metagenomics. Crowd-sourced analyses will collide with cloud computing, but eternal vigilance will be the price of preventing the misinterpretation and overselling of microbial sequence data. Output from hand-held sequencers will be analysed on mobile devices. Open-source training materials will address the need for the development of a skilled labour force. As we boldly go into the third decade of the twenty-first century, microbial sequence space will remain the final frontier! © 2016 The Author. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.