Download or read book Monitoring and Modeling the Fate and Transport of Nitrate in the Vadose Zone Beneath a Suwannee River Basin Vegetable Farm written by Michael Albert and published by . This book was released on 2002 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Projet relatif la noblesse au militaire et l tablissement de deux places pour les statues questre et p destre de Louis XV written by and published by . This book was released on 1750 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spring Meeting written by American Geophysical Union. Meeting and published by . This book was released on 2002 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sources and Chronology of Nitrate Contamination in Spring Waters Suwannee River Basin Florida written by Brian G. Katz and published by . This book was released on 1999 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Predicting Fate and Transport of Contaminants in the Vadose Zone Using a Soil Screening Model written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soil Screening Levels (SSLs) are threshold concentrations below which there is no concern for the migration of residual soil contaminants to the aquifer above maximum contaminant levels (MCLs). At sites where contaminant concentrations exceed SSLs, further study maybe warranted under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). SSLs are based upon simplified fate and transport assumptions, but the guidance allows the flexibility to develop a detailed modeling approach that accounts for complex site variables such as degradation and thickness of the vadose zone. The distinct advantage of the detailed modeling is that individual sites may calculate a less restrictive, but still protective SSL. A Multi-Layer Vadose Zone Contaminant Migration Model [VZCOMML(C)] was developed at the Savannah River Site to allay the higher costs of detailed modeling and achieve a higher clean-up level. The software model is faster, simpler, and less expensive to us e than other commercially available codes.

Download or read book Modeling Transport of Nitrate Through the Unsaturated Zone written by S.M. Gupte and published by . This book was released on 1990 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Assessing the Role of Geology for Nitrate Fate and Transport in Groundwater Beneath Riparian Buffers written by Timothy Ryan Wineland and published by . This book was released on 2002 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Riparian buffers have been shown to remove nitrate from groundwater, but the processes controlling removal are not well documented. Previous research at the Risdal Farm in the Bear Creek watershed in central Iowa suggests that geology influences groundwater velocity, residence time, denitrification rate, and ultimately how well the buffer functions. The research area for this study is the entire Bear Creek watershed, a 7,656 ha watershed with> 85 percent row crops. A multi-electrode electrical resistivity imaging system was used to characterize the extent and distribution of alluvial materials beneath buffers. Seven locations were selected for further groundwater investigations based on resistivity data and buffer maturity. A method for the construction, installation and monitoring of multilevel piezometers was developed for collection of hydrogeologic data in shallow alluvial sediments. Hydraulic gradient and hydraulic conductivity data from piezometers were used to assess controlling factors on nitrate removal in buffers. Buffers at the JRS, LSW, and TE sites both consistently removed over 95 percent of nitrate. The RRS and LSE sites often had little effect on nitrate removal, but occasionally achieved much higher removal rates. Nitrate removal was favored in locations with available dissolved organic carbon and low groundwater velocities (long residence time). Lack of dissolved oxygen in these locations suggests denitrifcation as the removal mechanism. Based on data from the 6 sites, the water quality benefits of buffers are most dependent on geology, groundwater residence time and geochemical environment and least dependent on the age of the buffer.

Download or read book Nitrate Transport in the Unsaturated Zone Below Agricultural Fields written by Suzanna L. Moore and published by . This book was released on 2005 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of a Nitrate Fate and Transport Model to the Abbotsford Sumas Aquifer Whatcom County Washington written by Margo A. Burton and published by . This book was released on 2007 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Assessment of Vadose Zone Solute Transport Under a Potato Field by a 19 Month Time lapse Cross hole Resistivity Imaging Survey written by Shuang Wang and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrate is a necessary nutrient for crops, however high concentrations of nitrate in surface water and groundwater can negatively affect aquatic ecosystems and human health. 3D cross-hole Electrical Resistivity Imaging (ERI) has been used to investigate the percolation of a conductive tracer (KCl) through a 17 m thick vadose zone as a proxy for the transport of nitrate under natural recharge conditions. Post-tracer surveys indicate that tracer movement has slowed significantly by early May, 2015 (about one month after tracer application), at the end of snow melt. The shallow conductivity anomaly produced by the tracer diminished significantly over the winter and spring of 2016, but showed little evidence of bulk matrix flow below approximately 6 m depth (top of the bedrock). It is speculated that fractures in the bedrock, too thin to be resolved by the ERI survey, conveyed tracer downward. After 18.5 months, there is no ERI evidence of tracer migrating through the matrix below approximately 6 m.

Download or read book Understanding Nitrate Accumulation in the Shallow Vadose Zone of Spanish Springs Valley Nevada written by Ronald Tyler Parratt and published by . This book was released on 2010 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies indicate that elevated nitrate accumulation has been occurring within the arid southwest, and this research focuses on investigating the occurrence of elevated soil nitrate in the mesic regions of northern Nevada, possible mechanics of nitrate accumulation and finally, remediation potential. Soil profiles in the Spanish Springs Valley, Nevada have indicated high concentration of nitrate 2-3 meters below the soil surface. The main vegetation of the area is sagebrush (Artemesia tridentata) and rabbitbrush (Chrysothamnus nauseosus) with groundwater depths varying from very deep (~ 28-30 m) to very shallow (~3 m). This research investigated the interaction of vegetative nitrate uptake, soil organic carbon, soil nitrate, and root growth with the elevated soil nitrate at these locations, as well as a possible nitrate accumulation mitigation technique, and the modeling of nitrate migration and microbial uptake within these locations. Soil and vegetative samples were collected from 4 different locations (three sites with deep groundwater and one with shallow groundwater), and previous data collected from monitor well installations were examined and analyzed. Laboratory experiments involving the migration and uptake of nitrate within carbon-augmented soil columns were conducted, and the modeling of these processes using Hydrus 1D was completed. The analyses indicate that the higher C:N in conjunction with shallow groundwater supports a higher root density with greater denitrification potential, precise irrigation of soil containing elevated nitrate layers can mitigate the transport of nitrate through microbial uptake, and Hydrus 1D modeling can, with accurate soil hydraulic properties, model the migration and uptake of nitrate within the soil columns. Also indicated from this research is the absence of distinction between sites in relation to the sagebrush (Artemesia tridentata) and rabbitbrush (Chrysothamnus nauseosus) plant leaf nitrate concentrations, as well as the capacity for microbial uptake from un-augmented soil. Conclusions indicate that nitrate levels in soil are directly influenced by groundwater levels which also appear to directly influence the C:N in the soil and the potential denitrification, and that soil within the Spanish springs Valley area contains sufficient carbon to promote the microbial uptake of almost half the nitrate contained within these elevated nitrate horizons when leaching may be initiated.

Download or read book Quantification of the Long Term Effects from Nutrient Reductions on Groundwater Nitrate Concentrations in an Agricultural Setting written by Jason Cole and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Vision Towards Developing a Spatially And Temporally Robust Data Driven Modeling Framework To Predict Continuous Stream Nitrate Concentration At Data Scarce Locations written by Gourab Saha and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stream nitrate concentration provides critical insights into nutrient dynamics and can help improve the effectiveness of sustainable ecosystem management decisions. Conventional stream nitrate monitoring is conducted through lab analysis using in-situ water samples, typically at coarse temporal resolution. In the United States, federal agencies and a few state and local agencies started collecting high-frequency (5-60 min intervals) nitrate data using optical sensors in the last decade. These sensor-based high-frequency stream nitrate concentrations at multiple stream locations in a region provide valuable information on the dynamics of nitrate transport, including the timing, magnitude, and sources of nitrate loading in the environmental system. This study hypothesized that the nitrate dynamics information available in a region's high-frequency stream nitrate monitoring sites could be used to estimate spatially and temporally continuous nitrate concentration at other low-frequency monitoring locations. Deep learning (DL) models could use to extract the complex nutrient dynamics from the high-frequency sites and transferred the information to low-frequency monitoring sites. The primary goal of this study was to develop a spatially and temporally robust data-driven modeling framework to predict continuous stream nitrate concentration at data-limited sites in a region using high-frequency nitrate data and biophysical attributes of the region. The objectives of this study are to (1) develop a deep learning (DL)-based modeling approach to generate continuous daily stream nitrate concentration for nitrate data-sparse watersheds and compare the performance of the developed modeling approach with other statistical models; (2) analyze the deep learning approach-based modeling framework to understand the critical environmental drivers of predicting daily nitrate concentrations, and; (3) explore the potential of extending the developed modeling framework to stream discharge unavailable locations for making the framework more spatially robust. This study used a DL model called Long Short-Term Memory (LSTM) to estimate continuous daily stream nitrate. The DL model received climate, land use, fertilization, topography, and soil characteristics data as inputs during the model development. The DL model was trained comprehensively by using four hyperparameters (batch size, hidden layer size, time window, and epoch) and isolating the best combination of hyperparameters based on five performance metrics, including RMSE, bias, correlation, NSE, and KGE. The hypothesis was tested with Iowa, USA, as a case study region because the state had more high-frequency nitrate monitoring sites with long-term data. In the first objective, a DL model-based stream nitrate estimation framework was trained and tested for thirty-four (34) high-frequency and eight (8) low-frequency nitrate monitoring sites. DL model demonstrated median test-period Nash-Sutcliffe efficiency (NSE) = 0.75 to estimate continuous daily stream nitrate concentration, which is unprecedented performance. Twenty-one sites (50% of all nitrate monitoring sites) and thirty-four sites (76%) demonstrated NSE greater than 0.75 and 0.50, respectively. The concentration (c) - discharge (Q) relationship analysis showed that the study watersheds had four dominant nitrate transport patterns from landscapes to streams with increasing discharge, including (i) flushing, (ii) flushing during low Q (Q median Q, Q50) and chemostatic during high Q (Q Q50), (iii) flushing during low Q and dilution during high Q and (iv) chemodynamic. The flushing pattern was identified as the most dominant c-Q relationship pattern. The developed DL modeling framework's performance was compared with other widely used statistical models, including Weighted Regressions on Time, Discharge, and Season (WRTDS) and Load Estimator (LOADEST), for the case study region. The study assumed that each basin had only one high-frequency monitoring site within the region. In this study, high-frequency nitrate data from each site were randomly subsampled to biweekly data and used as a pseudo-low-frequency site to train the DL model. These sites' remaining daily nitrate data were used for the developed DL model's performance evaluation. DL and WRTDS models performed similarly in most low-frequency nitrate monitoring sites. However, the developed DL model performed better at a few low-frequency nitrate monitoring sites. The DL and WRTDS models' performance in continuous nitrate estimation was better than the LOADEST model. Though the developed DL model performed exceptionally well in many sites, the performance was low for a few nitrate monitoring sites. The second objective identified the critical environmental drivers that impacted the data-driven modeling approach in estimating continuous stream nitrate concentrations. DL models were developed to predict daily stream nitrate concentrations at locations lacking continuous data. The sensitivity of daily varying environmental variables, including high-frequency nitrate and stream discharge and day length (representing seasonality) data, was identified in estimating continuous nitrate concentrations. The similarity between the sensitive variables was determined using Dynamic Time Warping (DTW) method to assess the contribution of biophysical similarity on the DL model performance. The DL model learned and transferred nitrate dynamics to sites within a radius of 300 km of a high-frequency nitrate monitoring site. The dominant annual c-Q relationship plots inferred that the DL model potentially learned nitrate dynamics from the data of a high-frequency nitrate monitoring site and predicted continuous nitrate concentrations accurately at low-frequency nitrate sites. DTW analysis indicated a similarity in nitrate concentration, stream discharge, and day length between a low-frequency and a high-frequency nitrate monitoring site, contributing to the accurate daily stream nitrate prediction. The third objective aimed to expand the data-driven modeling framework to those stream locations where stream discharge information is unavailable and make the framework more spatially robust. This study evaluated the potential of precipitation or simulated stream discharge data to be used as a surrogate of observed stream discharge data for the data-driven model development. Five cases were developed based on the DL modeling framework using the combination of precipitation, observed, and simulated stream discharge values to identify the most significant variable for estimating stream nitrate concentrations. The DL model, developed with observed stream discharge as a crucial environmental characteristic, demonstrated the best performance. The DL model performed similarly with simulated stream discharge as the critical variable, indicating that simulated discharge can be a potential surrogate. The cross-correlation analysis showed that precipitation, stream discharge, and temperature influence the winter periods' nitrate dynamics. For the other three seasons (e.g., Summer, Fall, and Spring) except winter, stream discharge was the most significant environmental for stream nitrate variabilities. This comprehensive study offers crucial insights into developing a spatially and temporally robust data-driven modeling framework for continuous stream nitrate estimation. The study results will help understand nitrate dynamics at data-limited locations, isolate the period for water withdrawal, optimize the new nitrate sensors installing locations, and design appropriate conservation practices to restrict landscape nitrate transport.

Download or read book A Preliminary Assessment of Sources of Nitrate in Springwaters Suwannee River Basin Florida written by and published by . This book was released on 1998 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A cooperative study between the Suwannee River Water Management District (SRWMD) and the U.S. Geological Survey (USGS) is evaluating sources of nitrate in water from selected springs and zones in the Upper Floridan aquifer in the Suwannee River Basin. A multi-tracer approach, which consists of the analysis of water samples for naturally occurring chemical and isotopic indicators, is being used to better understand sources and chronology of nitrate contamination in the middle Suwannee River region. In July and August 1997, water samples were collected and analyzed from six springs and two wells for major ions, nutrients, and dissolved organic carbon. These water samples also were analyzed for environmental isotopes [18O/16O, D/H, 13C/12C, 15N/14N] to determine sources of water and nitrate. Chlorofluorocarbons (CFCs; CCl3F CCl2F2, and C2Cl3,F3) and tritium (3H) were analyzed to assess the apparent ages (residence time) of springwaters and water from the Upper Floridan aquifer. Delta 15N-N03 values in water from the six springs range from 3.94 per mil (Little River Springs) to 8.39 per mil (Lafayette Blue Spring). The range of values indicates that nitrate in the sampled springwaters most likely originates from a mixture of inorganic (fertilizers) and organic (animal wastes) sources, although the higher delta 15N-N03 value for Lafayette Blue Spring indicates that an organic source of nitrogen is likely at this site. Water samples from the two wells sampled in Lafayette County have high delta 15N-NO3, values of 10.98 and 12.1 per mil, indicating the likelihood of an organic source of nitrate. These two wells are located near dairy and poultry farms, where leachate from animal wastes may contribute nitrate to ground water. Based on analysis of CFCs in ground water, the mean residence time of water in springs ranges from about 12 to 25 years. CFC-modeled recharge dates for water samples from the two shallow zones in the Upper Floridan aquifer range from 1985 to 1989.

Download or read book A Comprehensive Analysis of Contaminant Transport in the Vadose Zone Beneath Tank SX 109 written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coupled Geochemical and Hydrological Processes Governing the Fate and Transport of Radionuclides and Toxic Metals Beneath the Hanford Tank Farms written by Scott E. Fendorf and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project addresses the goals of the Environmental Management Sciences Program (EMSP) that seeks innovative basic research to benefit cleanup technologies and decision-making strategies for contaminated environments. Our proposal specifically addresses Hanford research needs in subsurface science by contributing to the objectives of the Tank Farm Vadose Characterization Project and the 200 Area Remedial Action Project (http://www.bhi-erc.com/projects/vadose/sandt/stdocs/subneeds.pdf) which are components of the Hanford Site Groundwater/Vadose Zone Integration Project (Integration Project). The work described in this proposal will advance the technological and scientific needs associated with the long-term management of the enormous inground inventories of 235/238U, 99Tc, 60Co, and Cr(VI) present at the Hanford site. We believe that scientifically defensible predictions of contaminant transport and strategies for remediation must be based upon a field-relevant understanding of coupled hydrological and geochemical processes that control subsurface contaminant fate and transport. This research project investigates the migration of 235/238U, 99Tc, 60Co, and Cr(VI) in undisturbed sediments from the Hanford site using realistic experimental protocols designed to delineate complex hydrological and geochemical processes controlling contaminant movement. The work complements and builds upon our current EMSP project 70219, which is scheduled to end this year, and our Hanford S&T project with PNNL (John Zachara as PI) that focuses on 90Sr transport beneath the BX tanks. The specific research goals of the following proposal are: (1) to provide an improved understanding of how preferential vertical and lateral flow, and the formation of immobile water influence the transport of radionuclides and toxic metals in heterogeneous, laminated sediments; (2) to quantify the rates and mechanisms of radionuclide and toxic metal interaction with the solid phase under various hydrologic conditions; and (3) provide new insights into how physical and mineralogical heterogeneities (e.g. stratification, pore regime connectivity, mineral composition along flowpaths) influence contaminant retardation and the degree of geochemical nonequilibrium during transport.

Download or read book The Impact of Land Use on Nitrate N Movement and Storage in the Vadose Zone of the Hastings WHPA written by Craig J. Adams and published by . This book was released on 2018 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nebraska has one of the largest agricultural economies in the United States and relies heavily on irrigation and fertilizer application to maintain crop yields. Over-irrigation and continuous application of nitrogen (N) in many areas has led to accumulation of nitrate-N in soils and sediments throughout the state's vadose zone. Because nitrate-N is both persistent and mobile, groundwater concentrations in many areas of Nebraska and other agriculturally intensive states are increasing. Nitrate-N contamination of public and private drinking water supplies that utilize groundwater are of particular concern. Vadose zone sampling is an important method for rapidly assessing the effect of changing land use on potential groundwater contamination. In the current project, the occurrence and movement of nitrate-N was investigated using deep vadose zone soil cores collected from urban and irrigated farmland in the Hastings, NE Well Head Protection Area (WHPA) and compared to a previous study done at the same locations (R. Spalding & Toavs, 2011). Sampling previously collected sites allows for direct comparisons of current and historical nitrate-N profiles, potential movement, and can provide a method for evaluating effects of changing land use at the surface. Cumulative nitrate-N in the top 65 ft for urban irrigated lawns, pivot irrigated farmland, and gravity irrigated farmland had an average of 320, 540, and 700 total lbs-N/acre respectively. In farmland where irrigation changed from gravity to pivot application there was an average reduction of 170 lbs-N/acre in the top 55 ft of the profile over a five-year time span. This observation supports the use of sprinkler irrigation for more uniform water application, reducing potential leaching at the head and tail rows of gravity irrigated fields. While future studies are still needed, the importance of vadose zone monitoring in evaluating and protecting groundwater is beneficial in determining connections between surface activities and the underlying groundwater..