Integrated Aquifer Vulnerability Assessment of Nitrate Contamination in Central Indiana PDF Download

Author: Won Seok Jang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Istvan Bogardi
Publisher: Springer Science & Business Media
ISBN: 3642760406
Category : Technology & Engineering
Languages : en
Pages : 438

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The nitrate content of drinking water is rising at an alarming rate in several regions of NATO countries and elsewhere in the world. The increase is due to lack of proper sewage treatment, and primarily to excess fertilizer application. Also, eutrophication in several coastal areas is triggered by high nitrate concentrations. The main purpose of this book is to integrate scientific knowledge related to exposure assessment, health consequences and control of nitrate contamination in water. The motivation is related to the magnitude, the possible adverse health effects, and the high cost of control ling nitrate contamination. Future research tasks are defined by an interaction among hydro logists, toxicologists and environmental engineers in an integrated framework for nitrate risk management. The target readership of this book is a mix of university colleagues, practitioners from both the private and public sectors and advanced graduate students working with the hydrological, health science or environmental engineering aspects of nitrate contamination. The main conclusions include: 1. For risk assessment purposes, knowledge and sufficiently accurate models are available to predict nitrate load and its fate in water under changes in land use. 2. Once agricultural exposure controls are implemented, the response times in ground water may be so long as to make controls unrealistic. 3. It is still unknown whether agricultural best management practice is a compromise between nitrate risk reduction and agricultural revenue. 4. The current drinking water guidelines of 10 mg/L NOrN need not be changed.

Author: Bernadette Boyle
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Groundwater is an integral piece of California's groundwater resources. One of the most common contaminants present in groundwater is nitrate. Nitrate contamination is often a result of agricultural land use activities on the ground surface. The study area for this analysis is the Salinas Valley Groundwater Basin, an agriculturally dominated basin in coastal California. The Salinas Valley Basin is both one of the most agriculturally productive areas of the state, as well as one of the most nitrate-contaminated basins in the state. The purpose of this research was to develop a groundwater vulnerability map for nitrate pollution in the Salinas Valley. A groundwater vulnerability assessment was carried out using a modified DRASTIC model. DRASTIC is a U.S. EPA rank-sum model for assessing groundwater vulnerability that incorporates depth to water, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity. In order to modify the DRASTIC model to assess nitrate contamination specifically, a land use parameter was incorporated into the model. The results of this assessment found 2.9% of the Basin has very low vulnerability, 50.6% has low vulnerability, 42.9% has moderate vulnerability, and 3.6% has high vulnerability. The results of the groundwater vulnerability assessment could not be validated using measured nitrate concentrations in the Basin. Four possible reasons for the poor fit of this assessment have been identified: (1) the temporal variability of select DRASTIC parameters, (2) the inability of the land use parameter to accurately represent nitrate vulnerability, (3) the high spatial variable of nitrate contamination in the Basin, and (4) the static weights assigned to parameters by the DRASTIC model.

Author: Riyana Ayub
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Denver Harper
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 24

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Author: Myriam Maria Stoewer
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Zusammenfassung: Groundwater is an important source of drinking water, but its quality is threatened by contamination with nitrate. In order to prevent groundwater contamination, knowledge about potential nitrate sources, their pathways and time lag between sources and drinking water wells is required. Still, i) simple methods to quantify nitrate fluxes are missing, ii) the applicability of stable isotopes of nitrate in nitrate source identification in grassland systems remains unknown, and iii) there is a lack of physically based modeling approaches focusing on the spatially resolved estimation of groundwater vulnerability to nitrate contamination. Thus, the objectives of the thesis are to i) quantify nitrate leaching in soils, ii) identify major sources of nitrate in aquifers, and iii) determine the intrinsic and nitrate specific aquifer vulnerability. The objectives were realized in a pre-alpine area with oligotrophic aquifers used for drinking water supply. Different isotopic and environmental tracers were used to understand the local hydrogeology and the fate of nitrate and related dynamic transformation processes. At farmed grassland sites, analysis of nitrate concentration in soil water below the root zone using suction cups was combined with groundwater recharge rates estimated from vertical deuterium profiles in soil to calculate nitrate fluxes. Stable isotopes of nitrate were analyzed in surface water, soil water and groundwater and compared with the distinct isotope composition of nitrate in potential sources. Local tritium concentrations were used in combination with a lumped-parameter model to calculate the mean residence times (MRTt) and MRTt distributions of local groundwater wells. The intrinsic and nitrate specific vulnerability of groundwater was spatially assessed (GIS) based on the approximation of the total mean residence time (MRT) and the residence time distribution as well as consulting data on nitrate leaching.Measured nitrate concentration below the root zone varies between 0 and 90 mg NO3- L-1. Estimated groundwater recharge rates cover a range of 430 to 926 mm yr-1. Nitrate leaching (0.2 to 41 kg NO3-N ha-1 yr-1) at grassland sites is highest in spring and fall. At farmed sites, nitrate leaching is positively related to fertilizer input rather than land use category (organic, conventional). Nitrate isotope values indicate that nitrate derive from ammonium nitrification of multiple sources, such as atmospheric deposition, mineral fertilizer, organic fertilizer and soil organic matter. The results suggest that local nitrate input is buffered in the upper soil, due to incorporation into soil organic matter, and released by subsequent mineralization and nitrification. Due to observed oxic conditions present in groundwater, the natural attenuation potential regarding nitrate (denitrification) is low. Modeled MRTt varies between 5 and 21 years, indicating that investigated groundwater wells are less vulnerable to short-term impacts. Though, such moderate to high MRT itself do not protect groundwater against contamination with nitrate. The observed MRT varies between smaller than 5 and 51 years. In comparison, the distribution curves generated from both modeling approaches show that the GIS approach neglects fast flow paths lower than five years. The results of the specific vulnerability assessment characterize the observation area as less vulnerable to groundwater contamination with nitrate. This is achieved by not exceeding the drinking water threshold due to the absence of land use, inducing high loads of nitrate leaching. Nevertheless, any increase in fertilizer application could change the nitrate level in groundwater due to oxic conditions and the underestimation of fast flow paths. Finally it is shown that time lags associated with land use are a perfect tool and need to be considered for management strategies. Consequently, areas attributed to low MRT are vulnerable to short-term contaminations but provide the chance to react fast in terms of groundwater protection management. On the contrary, areas attributed to high MRT might favor the natural attenuation and dilution of nitrate, but once nitrate has entered the groundwater, remediation strategies struggle with the time lag which results in long-term impacts on groundwater quality.The study shows that the combination of methods dealing with different scales results in a comprehensive assessment of groundwater vulnerability regarding nitrate leaching. Pre-alpine oligotrophic aquifers mainly covered with grassland require the need to reduce nitrogen input in groundwater catchments in order to protect water quality. This applies for areas vulnerable to short-term impacts as well as areas vulnerable to long-term impacts. In future, investigations examining the applicability of nitrogen in soil organic matter into fertilizer management are required in order to distinguish between organic fertilizer and sewage. In addition, nitrate source identification in such catchments should be combined with sophisticated tracers in order to distinguish between organic fertilizer and sewage effluent. Furthermore, the spatial assessment of groundwater vulnerability to nitrate contamination emphasizes the need to include the impact of hydrological dynamics as well as temporal and spatial variability in terms of land use

Author: David N. Sam
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 162

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This study assesses the level of nitrate contamination of the aquifer system in Hartford County. A GIS model that was developed by the United States Environmental Protection Agency was used to map the spatial distribution of vulnerability of the aquifer systems in Hartford County to potential nitrate contamination. Accordingly the study sought to assess the degree of vulnerability of the shallow aquifer systems in Hartford County to potential nitrate contamination. It was also carried out to find out the extent to which aquifers in the region have been impacted by nitrate leaching. In the study, soil and land-use data about the region were collected from the Connecticut Department Energy and Environmental Protection (DEEP). Other data, such as distance to waste sewage service location, net recharge, aquifer media, slope, hydraulic and the impact of the vadose zone was compiled from a database maintained by the USGS. A table containing the attributes of all seven hydrogeological factors was constructed and a goedatabase file was created for the data. The Drastic technique for groundwater mapping was adopted within ArcGIS to evaluate pollution potential of aquifers in the study area. After generating seven factors, numerical weights ranging from 1-10 based on each factor's relative impact on pollution was assigned. The factor with the most significant parameter for water quality was assigned a weight of 1 while the least significant factor was assigned a weight of 10. After this a vulnerability index was computed as the weighted sum of the seven factor maps. The final map shows very high degree of vulnerability of among bedrocks within Hartford County. Thus, about 80% of groundwater in the study area was found to be highly vulnerable to nitrate contamination. It is estimated that a significant amount of nitrate could be present in every 50gallons of water that is pumped from wells in most areas in the study area. Wells located in the low contaminated areas had a low possibility of nitrate contamination. The study addressed the problem of using a computer-based technology to show nitrate leaching into aquifers within the study area. The final map could be used in a public awareness campaign to educate the general public, especially communities in the study area about groundwater contamination in the region. The study recommends that groundwater in the region should be closely monitored for nitrate pollution. This is particularly true for individuals who live solely on well water in rural parts of the Hartford County. To do this, the study recommends the utilization of non-nitrate based fertilizers on farmlands along the Connecticut River. Sewage treatment centers in the region could also be consolidated to help reduce the exposure to sewage treatment in the region.

Author: Jamie T. Koch
Publisher:
ISBN:
Category :
Languages : en
Pages : 279

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The increased use of both organic and synthetic fertilizers on agricultural land has lead to rising groundwater nitrate concentrations in some areas of southern Ontario. This has occurred at the Thornton Well Field in Oxford County, likely as a result of impacts from legacy agricultural activities in the area. In an attempt to mitigate the impact on water quality within the well field, the County purchased some of the agricultural land in the vicinity of the well field in 2001 with plans to reduce nutrient loading through the implementation of Beneficial Management Practices (BMPs). Since the initiation of the BMPs, the nitrogen application rates within the study site were reduced by 20 to 100% relative to historical rates. The objectives of this study were to provide a unique, five year data set which can assist in BMP development and provide direction for regional scale agricultural policy; evaluate the nitrate mass flux at numerous locations through the unsaturated zone beneath a BMP-activated agricultural field within a complex moraine environment; develop and compare various methods to upscale point measurements of mass flux to mass loading (t N03-N/yr) at the field and regional scale; evaluate standardized methods of assessing aquifer vulnerability and compare results within the context of non-point source agricultural contaminants at the field and regional scale; and determine whether monitoring water levels and temperature within monitoring wells is able to aid in evaluating vulnerability to surface contaminants.

Author: Anil Shrestha
Publisher:
ISBN: 9781085616966
Category : Geography
Languages : en
Pages : 183

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The Central Valley (CV) Aquifer, California is one of the most productive regions of the United States, where large amount of nitrogen fertilizer has been applied for the last few decades to increase the crop productivity. The application of excessive fertilizer has increased the level of nitrate (NO3-N) in the groundwater to above EPA's maximum contamination level (MCL) of 10 mg/L in several domestic, public and monitoring wells. The concentration of nitrate in the groundwater can vary spatially depending on the local nitrogen sources, aquifer characteristics and geochemical condition of the area. The changing hydrogeological conditions of the valley due to excessive groundwater pumping could further complicate the fate of nitrate in the aquifer. The statistical, index-overlay and process-based methods are commonly used to study the vulnerability of aquifer to nitrate contamination. The main purpose of this dissertation is to understand the spatial distribution of groundwater nitrate contamination in the CV which was achieved by applying a relatively new method called Geodetector. Geodetector analyzes the spatial distribution of groundwater NO3-N based on the spatial variance of groundwater nitrate in stratified geographic area of important explanatory variables such as fertilizer, cropland, permeability, slope, dissolved oxygen, etc. The assumption is that if an environmental factor contributes to a groundwater contamination, the spatial distribution of the groundwater contamination should be similar to that of the environmental factor and this spatial association is measured by the Power of Determinant (PD), which is derived based on local and global variances. This method identifies significant explanatory variables, vulnerable areas, relative significance of variables and interaction between variables to strengthen or weaken the effect. The watersheds in the Central Valley were used as the basic analysis units and the percent of wells with above 5 mg/L NO3-N (PWN>5) were calculated for each watershed for the period of 2002 to 2014 to represent its contamination level. Each explanatory variable was processed to different spatially stratified areas to quantify their spatial correspondence with PWN>5. The results of Geodetector method were compared with those from Principal Component Analysis (PCA) and Geographically Weighted Regression (GWR). Finally, maps of susceptibility to nitrate contamination of the CV were developed based on the groundwater basins using the optimized-DRASTIC index and Geodetector-Frequency Ratio Index (GFR). The quantitatively derived GFR index values resulted in better map as reflected by high PD values and correlation coefficient with observed nitrate contamination pattern. The Geodetector method makes no assumptions about the data and has the ability to process multiple data sets, which can be both categorical and continuous. Therefore, Geodetector is advantageous over PCA and GWR, which often suffer from the multicollinearity of data. The Geodetector method offers water resources managers and policy makers a general framework to assess groundwater contamination vulnerability in any other study areas.

Author: Karthik Kumarasamy
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Groundwater is an important natural resource for numerous human activities, accounting for more than 50% of the total water used in the United States. Groundwater is vulnerable to contamination by several organic and inorganic pollutants such as nitrate, heavy metals, and pesticides. Assessment of groundwater vulnerability aids in the management and protection of limited groundwater resources. The focus of this thesis is to (1) statistically compare two groundwater vulnerability assessment models; modified DRASTIC (Acronym for Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and hydraulic Conductivity of aquifer) and ordinal logistic regression for NO3- contamination of shallow groundwater of the US, (2) analyze any discrepancies in the predictability of each of these models, and (3) discuss the advantage of each of the above-mentioned models with respect to performance, data requirement, and its ability to predict vulnerability. Analysis of NO3- concentration in groundwater allows for a reliable comparison of the two models. The results from the OLR model indicate a better correlation between the observed and average predicted probabilities. A very low R2 value was obtained between the modified DRASTIC and nitrate concentration, indicating poor prediction capabilities and need for high resolution data. Limitation with respect to requirement of more data with respect to prediction is seen in both the methods.