Risk and Cost Assessment of Nitrate Contamination in Domestic Wells

This study combines empirical predictive and economics models to estimate the cost of remediation for domestic wells exceeding suggested treatment thresholds for nitrates. A multiple logistic regression model predicted the probability of well contamination by nitrate, and a life cycle costing methodology was used to estimate costs of nitrate contamination in groundwater in two areas of Nebraska. In south-central Nebraska, 37% of wells were estimated to be at risk of exceeding a threshold of 7.5 mg/L as N, and 17% were at risk of exceeding 10 mg/L as N, the legal limit for human consumption in the United States. In an area in northeastern Nebraska, 82% of wells were at risk of exceeding the 10 mg/L as N legal threshold. Reverse osmosis Point-of-Use (POU) treatment was the option with the lowest costs for a household (3–4 individuals), with an average of $4–$164 total regional cost per household per year depending on the threshold for treatment. Ion exchange and distillation were the next most cost-effective options. At the community level (~10,000 individuals), a reverse osmosis Point-of-Entry (POE) treatment system was the most expensive option for a community due to high initial costs and ongoing operation and maintenance costs, whereas the biological denitrification system was least expensive due to economies of scale. This study demonstrates integrated modeling methods to assess water treatment costs over time associated with groundwater nitrate contamination, including quantification of at-risk wells, and identifies suitable options for treatment systems for rural households and communities based on their cost

Irrigation Water Quality—A Contemporary Perspective

In the race to enhance agricultural productivity, irrigation will become more dependent on poorly characterized and virtually unmonitored sources of water. Increased use of irrigation water has led to impaired water and soil quality in many areas. Historically, soil salinization and reduced crop productivity have been the primary focus of irrigation water quality. Recently, there is increasing evidence for the occurrence of geogenic contaminants in water. The appearance of trace elements and an increase in the use of wastewater has highlighted the vulnerability and complexities of the composition of irrigation water and its role in ensuring proper crop growth, and long-term food quality. Analytical capabilities of measuring vanishingly small concentrations of biologically-active organic contaminants, including steroid hormones, plasticizers, pharmaceuticals, and personal care products, in a variety of irrigation water sources provide the means to evaluate uptake and occurrence in crops but do not resolve questions related to food safety or human health effects. Natural and synthetic nanoparticles are now known to occur in many water sources, potentially altering plant growth and food standard. The rapidly changing quality of irrigation water urgently needs closer attention to understand and predict long-term effects on soils and food crops in an increasingly fresh-water stressed world

A Detailed Assessment of Groundwater Quality in the Kabul Basin, Afghanistan, and Suitability for Future Development

Abstract: Kabul is one of the most populated cities in Afghanistan and providing resources to support this population in an arid climate presents a serious environmental challenge. The current study evaluated the quality of local Kabul Basin groundwater to determine its suitability water for drinking and irrigation purposes now and into the future. This aim was aided through groundwater parameter assessment as well as determination ofWater Quality Index (WQI) developed from 15 observation points near the city. The results of our physicochemical analysis illustrate that groundwater in the majority of areas of the Kabul Basin is not generally suitable for human consumption, and in some cases the concentrations of many contaminants are higher than accepted health standards or water quality benchmarks. The aquifer underlies an arid landscape, and because of this 85% of the samples tested are very hard while just over 13% are classified as hard. Groundwater in the Kabul Basin is typically high in calcium and magnesium and overall classified as a calcium bicarbonate water type. Overall, more than 60% of the analyzed samples had concentrations higher than the World Health Organization (WHO) standard of total dissolved solids (TDS), 10% in total hardness (TH), about 30% in turbidity and more than 90% in magnesium. The results show that based on WQI, without treatment, roughly 5% of groundwater in the studied area is unsuitable for human consumption, while 13.3% is very poor and 40% is poor quality water. Approximately 40% of the assessed groundwater has good quality and could be used as drinking water for future development. Groundwater in some areas shows evidence of pollution and high dissolved solids content, rendering these sources unsuitable for either drinking or irrigation purposes

A Detailed Assessment of Groundwater Quality in the Kabul Basin, Afghanistan, and Suitability for Future Development

Kabul is one of the most populated cities in Afghanistan and providing resources to support this population in an arid climate presents a serious environmental challenge. The current study evaluated the quality of local Kabul Basin groundwater to determine its suitability water for drinking and irrigation purposes now and into the future. This aim was aided through groundwater parameter assessment as well as determination ofWater Quality Index (WQI) developed from 15 observation points near the city. The results of our physicochemical analysis illustrate that groundwater in the majority of areas of the Kabul Basin is not generally suitable for human consumption, and in some cases the concentrations of many contaminants are higher than accepted health standards or water quality benchmarks. The aquifer underlies an arid landscape, and because of this 85% of the samples tested are very hard while just over 13% are classified as hard. Groundwater in the Kabul Basin is typically high in calcium and magnesium and overall classified as a calcium bicarbonate water type. Overall, more than 60% of the analyzed samples had concentrations higher than the World Health Organization (WHO) standard of total dissolved solids (TDS), 10% in total hardness (TH), about 30% in turbidity and more than 90% in magnesium. The results show that based on WQI, without treatment, roughly 5% of groundwater in the studied area is unsuitable for human consumption, while 13.3% is very poor and 40% is poor quality water. Approximately 40% of the assessed groundwater has good quality and could be used as drinking water for future development. Groundwater in some areas shows evidence of pollution and high dissolved solids content, rendering these sources unsuitable for either drinking or irrigation purposes

Irrigation Water Quality—A Contemporary Perspective

In the race to enhance agricultural productivity, irrigation will become more dependent on poorly characterized and virtually unmonitored sources of water. Increased use of irrigation water has led to impaired water and soil quality in many areas. Historically, soil salinization and reduced crop productivity have been the primary focus of irrigation water quality. Recently, there is increasing evidence for the occurrence of geogenic contaminants in water. The appearance of trace elements and an increase in the use of wastewater has highlighted the vulnerability and complexities of the composition of irrigation water and its role in ensuring proper crop growth, and long-term food quality. Analytical capabilities of measuring vanishingly small concentrations of biologically-active organic contaminants, including steroid hormones, plasticizers, pharmaceuticals, and personal care products, in a variety of irrigation water sources provide the means to evaluate uptake and occurrence in crops but do not resolve questions related to food safety or human health effects. Natural and synthetic nanoparticles are now known to occur in many water sources, potentially altering plant growth and food standard. The rapidly changing quality of irrigation water urgently needs closer attention to understand and predict long-term effects on soils and food crops in an increasingly fresh-water stressed world

Transmission Routes of the Microbiome and Resistome from Manure to Soil and Lettuce

The land application of animal manure can introduce manure microbiome and resistome to croplands where food crops are grown. The objective of this study was to characterize the microbiome and resistome on and in the leaves of lettuce grown in manured soil and identify the main transmission routes of microbes and antibiotic resistance genes (ARGs) from soil to the episphere and endosphere of lettuce. Shotgun metagenomic results show that manure application significantly altered the composition of the microbiome and resistome of surface soil. SourceTracker analyses indicate that manure and original soil were the main source of the microbiome and resistome of the surface soil and rhizosphere soil, respectively. Manure application altered the microbiome and resistome in the episphere of lettuce (ADONIS p \u3c 0.05), and surface soil accounted for ~81% of the microbes and ~62% of the ARGs in episphere. Manure application had limited impacts on the microbiome and resistome in the endosphere (ADONIS p \u3e 0.05). Our results show that manure-borne microbes and ARGs reached the episphere primarily through surface soil and some epiphytic microbes and ARGs further entered the endosphere. Our findings can inform the development of pre- and postharvest practices to minimize the transmission of manure-borne resistome from food crops to consumers

Comparative evaluation of machine learning models for groundwater quality assessment

Contamination from pesticides and nitrate in groundwater is a significant threat to water quality in general and agriculturally intensive regions in particular. Three widely used machine learning models, namely, artificial neural networks (ANN), support vector machines (SVM), and extreme gradient boosting (XGB), were evaluated for their efficacy in predicting contamination levels using sparse data with non-linear relationships. The predictive ability of the models was assessed using a dataset consisting of 303 wells across 12 Midwestern states in the USA. Multiple hydrogeologic, water quality, and land use features were chosen as the independent variables, and classes were based on measured concentration ranges of nitrate and pesticide. This study evaluates the classification performance of the models for two, three, and four class scenarios and compares them with the corresponding regression models. The study also examines the issue of class imbalance and tests the efficacy of three class imbalance mitigation techniques: oversampling, weighting, and oversampling and weighting, for all the scenarios. The models’ performance is reported using multiple metrics, both insensitive to class imbalance (accuracy) and sensitive to class imbalance (F1 score and MCC). Finally, the study assesses the importance of features using game-theoretic Shapley values to rank features consistently and offer model interpretability

Pesticide occurrence and persistence entering recreational lakes in watersheds of varying land uses

Currently little is known of newer pesticide classes and their occurrence and persistence in recreational lakes. Therefore, the objectives of this study were to (1) assess average pesticide concentrations and loadings entering recreational lakes in three mixed land use watersheds throughout the growing season, (2) evaluate pesticide persistence longitudinally within the lakes, and (3) perform an ecotoxicity assessment. Six sampling campaigns were conducted at three lakes from April through October 2018 to measure the occurrence and persistence during pre, middle, and post growing season. Polar organic chemical integrative samplers (POCIS) were placed in streams near lake inlets and monthly samples were collected for analysis of twelve pesticides. Additional monthly grab water samples were taken at each POCIS location and at the midpoint and outlet of each lake. All pesticide samples were analyzed using liquid chromatography/tandem mass spectrometry (LC/MS/MS) and individual pesticide loading rates were determined. Occurrence and persistence of specific pesticides were significantly different between lakes in varying watershed land uses. Specifically, the recreational lake receiving predominately urban runoff had the highest load of pesticides, likely in the form of biocides, entering the waterbody. Concentrations of imidacloprid exceeded acute and chronic invertebrate levels for 11% and 61% of the sampling periods, respectively, with the recreational lake receiving predominately urban runoff having the most occurrences. Findings from this study are critical for preventing and mitigating potential effects of pesticides, specifically applied as biocides in urban landscapes, from entering and persisting in recreational lakes

The long term effect of agricultural, vadose zone and climatic factors on nitrate contamination in Nebraska\u27s groundwater system

A four-decade dataset (1974–2013) of 107,823 nitrate samples in 25,993 wells from western and eastern parts of Nebraska was used to assess long-term trends of groundwater nitrate concentration and decadal changes in the extent of groundwater nitrate-contaminated areas (NO3-N≥10 mg N/L) over the entire state. Spatial statistics and regressions were used to investigate the relationships between groundwater nitrate concentrations and several potential natural and anthropogenic factors, including soil drainage capacities, vadose zone characteristics, crop production areas, and irrigation systems. The results of this study show that there is no statistically significant trend in groundwater nitrate concentrations in western Nebraska, in contrast with the increasing trend (p \u3c .05) to the east. The spatial extent and nitrate concentrations in contaminated groundwater in center pivot-irrigated areas was less than in gravity-irrigated areas. Areas with a thicker vadose zone and larger saturated thickness of the aquifer have relatively lower nitrate concentrations. The results of a classification and regression tree (CART) model indicate the difference in the influence of physical factors on groundwater nitrate concentrations between western and eastern Nebraska, namely that groundwater nitrate concentrations correspond with vadose zone thickness, effective hydraulic conductivity, and saturated thickness in the west, while in eastern Nebraska, concentrations are correlated with average percent sand in the topsoil (0–150 cm), well depth, and effective hydraulic conductivity

Risk and Cost Assessment of Nitrate Contamination in Domestic Wells

This study combines empirical predictive and economics models to estimate the cost of remediation for domestic wells exceeding suggested treatment thresholds for nitrates. A multiple logistic regression model predicted the probability of well contamination by nitrate, and a life cycle costing methodology was used to estimate costs of nitrate contamination in groundwater in two areas of Nebraska. In south-central Nebraska, 37% of wells were estimated to be at risk of exceeding a threshold of 7.5 mg/L as N, and 17% were at risk of exceeding 10 mg/L as N, the legal limit for human consumption in the United States. In an area in northeastern Nebraska, 82% of wells were at risk of exceeding the 10 mg/L as N legal threshold. Reverse osmosis Point-of-Use (POU) treatment was the option with the lowest costs for a household (3–4 individuals), with an average of $4–$164 total regional cost per household per year depending on the threshold for treatment. Ion exchange and distillation were the next most cost-effective options. At the community level (~10,000 individuals), a reverse osmosis Point-of-Entry (POE) treatment system was the most expensive option for a community due to high initial costs and ongoing operation and maintenance costs, whereas the biological denitrification system was least expensive due to economies of scale. This study demonstrates integrated modeling methods to assess water treatment costs over time associated with groundwater nitrate contamination, including quantification of at-risk wells, and identifies suitable options for treatment systems for rural households and communities based on their cost