Risk Of Groundwater Pollution Research Articles

Impact of Sandy Soil Amendment with Dairy Slurry Treated through pH Adjustment on Nutrient and Coliform Leaching

Livestock farming produces high volumes of animal slurry that can be sanitized using low-cost treatments by pH adjustment, reducing pathogen contamination, and promoting slurry valorization as a safe fertilizer. This work aims to evaluate the impact of sandy soil amendment with dairy slurry treated by pH adjustment on the potential release of nutrients and coliforms into groundwater. A laboratory soil column leaching experiment was conducted and the surface application of six treatments was tested: raw dairy slurry, dairy slurry acidified with H2SO4, dairy slurry alkalinized with KOH, alkalinized/neutralized dairy slurry, mineral fertilizer, and a control. The fertilizer application rate was 0.08 g N kg−1 dry soil. Leachates were analyzed for pH, electrical conductivity, N-NH4+ and N-NO3−, macro- and micronutrients, and fecal coliforms. Results showed that amendment with dairy slurry led to significantly lower nitrate leaching potential than mineral fertilizer (maximum 16.1 vs. 50.4%). The use of hygienized slurry by alkalinization decreased the potential leaching of coliforms relative to raw slurry. However, incomplete sanitization by acidification strongly promoted coliform leaching and the risk of groundwater contamination. It can be concluded that the use of alkalinized dairy slurry is a safer solution than raw slurry with regard to the risk of groundwater pollution.

Estimation of Global Water Quality in Four Municipal Wastewater Treatment Plants over Time Based on Statistical Methods

Wastewater from urban and industrial sources can be treated and reused for crop irrigation, which can certainly help to protect aquifers from overexploitation and potential environmental risks of groundwater pollution. In fact, water reuse can also have negative effects on the environment, such as increased salinity, pollution phenomena or soil degradation, among others. Consequently, reuse of wastewater requires rigorous treatment and a very detailed analysis of different parameters, in compliance with established quality limitation standards. Therefore, this study was carried out to develop a prediction of temporal changes in water quality by introducing a wastewater quality index (WWQI) for four regional wastewater treatment plants (WWTPs) in Murcia, Southeast Spain, where a significant number of physicochemical and biological parameters are obtained in time series over the period 2019–2021. For this purpose, multivariate statistical analyses have been adopted to predict the performance of WWQI. By robust PCA of the sixteen physicochemical variables of the raw and treated wastewater, five main principal components (PCs) were extracted, which explain between 21.39% and 36.79% of the data variability. From the loadings of the PCs, the relationships between the original parameters are analyzed. The accuracy of the developed models in terms of fit to the training dataset ranged from 74.3% to 97.9%, with p-values < 0.05. The techniques incorporated in this study provided a comprehensive evaluation framework for monitoring wastewater treatment.

Status quo and change characteristics of groundwater resources pollution in the Hami region based on sustainable development strategies

AbstractWater shortage is a universal resource problem worldwide, especially in arid and semi-arid regions. The Hami Basin is one of the most water-scarce areas in China, with low average annual precipitation and high evaporation. In order to effectively monitor groundwater problems, this paper proposes a study on the status and change characteristics of groundwater resource pollution in the Hami area based on sustainable development strategies, aiming to study the changes in groundwater in the Hami area and propose corresponding measures to reduce pollution and save water resources. The method of this article is to introduce the groundwater quality evaluation method, analyze the environmental carrying capacity and then study the evolution process of the groundwater environment in the Hami area. The function of the method is to assess the ecological risk of groundwater and the risk of groundwater pollution, and to analyze the changes in the carrying capacity of the local environmental system. This paper uses groundwater detection experiments to detect the current status of groundwater resource pollution and the characteristics of groundwater changes in the Hami area, and establish a groundwater numerical model in the Hami area.

Groundwater Risk Assessment Based on DRASTIC and Special Vulnerability of Solidified/Stabilized Heavy-Metal-Contaminated Sites

Solidification/stabilization technology is commonly used in the remediation of heavy-metal-contaminated sites, which reduces the leaching capacity of heavy metals, but the total amount of heavy metals in the soil is not reduced, there is still a risk of heavy metal re-release and contamination of groundwater, and the risk of groundwater contamination of solidified/stabilized heavy-metal-contaminated sites needs to be assessed. Through the analysis of the system structure of solidified/stabilized heavy-metal-contaminated sites, combined with the integration method of pollution sources—the vadose zone-aquifer, based on the DRASTIC model and the special vulnerability of the solidification/stabilization site, a groundwater pollution risk assessment index system including 4 influencing factors such as site hazard, pollutant hazard, aquifer vulnerability, and natural conditions and a total of 18 evaluation indexes was constructed. Each evaluation index was graded and assigned a scoring value combined with the Analytic Hierarchy Process (AHP) to calculate index weights. The comprehensive weights of site hazard, contaminant stability, aquifer vulnerability, and natural conditions were 0.1894, 0.3508, 0.3508, and 0.1090, respectively. The isometric method was used to classify the pollution risk into five risk levels (very low risk [0, 2), low risk [2, 4), medium risk [4, 6), high risk [6, 8), and very high risk [8, 10]), and a groundwater comprehensive index pollution risk assessment model was established. The model was applied to the actual site. The results showed that under the scenario of direct landfill of remediated soil, the comprehensive indexes of groundwater pollution risk for As and Cd were 4.55 and 4.58, respectively, both of which were medium risk. When the surrounding protective measures were supplemented, the comprehensive indexes of groundwater pollution risk for As and Cd were 3.98 and 4.02, respectively. Cd remained as medium risk and As as low risk. In both scenarios, the combined groundwater contamination risk index of Cd was greater than that of As because the contaminant stability of As was higher than that of Cd. The average percentage of aquifer vulnerability score reached 45.50%, which was higher than the weight of site inherent vulnerability of 35.08%, indicating that the original site hydrogeological conditions are fragile, groundwater is vulnerable to contamination, and the in situ landfill solidification/stabilization of soil is at risk. In order to further reduce the risk, the topographic slope was increased, thereby increasing the surface drainage capacity, which reduced the combined groundwater contamination risk index for As and Cd to 3.94 and 3.90, both of which were low risk. This study provides a new method for assessing the risk of groundwater contamination at solidified/stabilized heavy-metal-contaminated sites. It also has reference significance for selecting solidification/stabilization remediation parameters

Exogenous-organic-matter-driven mobilization of groundwater arsenic

The potential release capacity of arsenic (As) from sediment was evaluated under a high level of exogenous organic matter (EOM) with both bioreactive and chemically reactive organic matters (OMs). The OMs were characterized by FI, HIX, BIX, and SUVA254 fluorescence indices showing the biological activities were kept at a high level during the experimental period. At the genus level, Fe/Mn/As-reducing bacteria (Geobacter, Pseudomonas, Bacillus, and Clostridium) and bacteria (Paenibacillus, Acidovorax, Delftia, and Sphingomonas) that can participate in metabolic transformation using EOM were identified. The reducing condition occurs which promoted As, Fe, and Mn releases at very high concentrations of OM. However, As release increased during the first 15–20 days, followed by a decline contributed by secondary iron precipitation. The degree of As release may be limited by the reactivity of Fe (hydro)oxides. The EOM infiltration enhances As and Mn releases in aqueous conditions causing the risk of groundwater pollution, which could occur in specific sites such as landfills, petrochemical sites, and managed aquifer recharge projects.

Air temperature spikes increase bacteria presence in drinking water wells downstream of hog lagoons

>44 million United States residents depend on private drinking water wells that are federally unregulated. Maintaining a clean groundwater supply for populations without access to public water systems is essential to supporting public health and falls to state regulators and private well owners. Yet, monitoring practices do not reflect the fact that groundwater pollution risk varies seasonally and with proximity to nearby surface-contaminated sites. Examination of nearly 50,000 well water samples across North Carolina, ranked second nationally in domestic well dependence and swine production, from 2013 to 2018 reveals a uniform sampling schedule but a variable risk of bacterial contamination within each calendar year. We document a threshold of 32.2 °C (90 °F) where total coliform bacteria and Escherichia coli (E. coli) detection in private well water spikes near swine lagoons but is absent from “upstream” wells and otherwise unexplained by a variety of other known contamination sites. Closing the gap between perceived and actual risks of drinking water contamination has potential to improve public health. State regulations and federal guidelines should consider coordinating domestic well sampling with seasonally and spatially fluctuating risks of groundwater contamination. Findings from this study are generalizable, having implications for other parts of the world with water sources that have the potential to get contaminated by nearby surface sources of human and animal waste, such as manure applications and leaching septic systems.

Quantifying the contribution of ecological water replenishment on aquifer recovery using a refined groundwater model.

Due to its independent control and directly easy operation, ecological water replenishment (EWR) has been an important measure for restoring river ecosystems. However, the positive and negative contribution of the EWR activities to aquifer system are not fully understood under the combined influences of climate change and human activities across time scales. A refined groundwater flow model integrating an open channel flow at daily time scales is developed in a part of Northern China Plain to reproduce the dynamic process of groundwater level changes. After model calibration with groundwater level and runoff data, the changes of simulated groundwater level and river runoff have the Nash-Sutcliffe efficiency coefficient of 0.98 and 0.60, respectively. Results clearly demonstrate that the impulse response of aquifer recovery to runoff in three centralized EWRs. By using with and without EWR method, the simulated maximum contribution of EWR near river to aquifer recovery may be over 70 %. Scenario analysis method considering different precipitation, groundwater exploitation reduction and EWR activities are applied to evaluate the total quantities of aquifer recovery. The prediction of nine-year EWR activities under multiple scenarios shows that the increased groundwater level generally varies from 4.08 to 8.57 m, and the contribution of EWR accounts for 7.88 %-36.59 %. It is also noticed that 14 out of the 18 informal landfill sites will face potential groundwater pollution risks, indicating the negative influences of long-term EWR activities. This study can provide a method for quantifying the influences and contribution of EWR on aquifer recovery and can be referred to as a guideline for EWR evaluation with similar hydrogeological conditions.

Groundwater chemistry, pollution and health risk assessment for nitrogen compounds. A case study in a suburban region of Romania

As groundwater is used as a source of drinking water, monitoring its quality is essential due to possible adverse effects on human health. Nitrogen compounds (nitrates, nitrites, ammonia) within certain concentration limits are natural components of the nitrogen cycle. Due to anthropogenic activities, high concentrations of nitrogen compounds are released into groundwater. The aim of this study was to evaluate the chemistry of groundwater in a suburban area in northeastern Romania, the sources of pollution with nitrogen compounds (nitrates, nitrites, ammonium), and the non-carcinogenic risk to human health associated with consumption in different groups age (women, men, and children) in the investigated region. The results showed that the concentration of nitrogen compounds varies from 5.12 to 98.3 mg/L for nitrates, from 0.008 to 85.2 mg/L for ammonium, and from 0.001 to 1.12 mg/L for nitrites. The maximum admissible concentrations have been exceeding 25%, 40% and respectively 10% of the total analyzed samples Bivariate graphs and Principal Component Analysis (PCA) were used to identify potential sources of nitrate, nitrites, and ammonium pollution of groundwater in the study area. The non-carcinogenic risk assessment for water consumption showed a hazard index (HItotal) for nitrogen compounds in groundwater in the investigated region, which ranged from 0.037 to 2.856 for men, between 0.054 and 3.427 for women, respectively between 0.080 and 6.145, for children. Spatial distribution maps using the Inverse Distance Weighting technique presented the geographical areas with the probability of groundwater contamination with nitrate, nitrite, and ammonium and the areas that pose a risk to human health by consuming groundwater in the study area for the three groups: men, women and children.

Chromium Transport and Fate in Vadose Zone: Effects of Simulated Acid Rain and Colloidal Types.

Chromium (Cr) can enter groundwater through rainfall infiltration and significantly affects human health. However, the mechanisms by which soil colloids affect chromium transport are not well investigated. In this study, column experiments were conducted to simulate the chromium (Cr) transport mechanism in two typical soils (humic acid + cinnamon soil and montmorillonite + silt) in the vadose zone of a contaminated site and the effects of acid rain infiltration conditions. The results showed that Mt colloids have less influence on Cr. The fixation of Cr by colloid mainly occurs in the cinnamon soil layer containing HA colloid. The adsorption efficiency of Cr was increased by 12.8% with the addition of HA. In the HA-Cr system, the introduction of SO42- inhibited the adsorption of Cr, reducing the adsorption efficiency from 31.4% to 24.4%. The addition of Mt reduced the adsorption efficiency of Cr by 15%. In the Mt-Cr system, the introduction of SO42- had a promoting effect on Cr adsorption, with the adsorption efficiency increasing from 4.4% to 5.1%. Cr release was inhibited by 63.88% when HA colloid was present, but the inhibition owing to changes in acidity was only 14.47%. Mt colloid promotes Cr transport and increases the leaching rate by 2.64% compared to the absence of Mt. However, the effect of acidity change was not significant. Intermittent acid rain will pose a higher risk of pollutant release. Among the influencing factors, the type of colloid had the most significant influence on the efficiency of Cr leaching. This study guides the quantitative assessment of groundwater pollution risk caused by Cr in the vadose zone.

Multivariate and spatio-temporal groundwater pollution risk assessment: A new long-time serial groundwater environmental impact assessment system

Groundwater pollution risk assessment is an important part of environmental assessment. Although it has been developed for many years, there has not yet been a multi-dimensional method that takes into account long time series and spatial factors. We proposed a new method combines the advantages of remote sensing cloud computing, long-term groundwater modeling simulation and GIS technology to solve it efficiently. A coastal industrial park in Hainan was used as the study area. The depth of groundwater level, rainfall, topography and geomorphology, soil moisture, pollution source, pollution toxicity and other more than 10 parameters were used as the indexes. A comprehensive model with remote sensing cloud computing, DRASTIC model and Modflow + MT3DMS was established to assess the pollution risk from 2014 to 2021. The multi-year results indicated that the risk assessment of groundwater pollution was usually on the vertical coastal direction, and the risk increased from far away to near coast. With the discharge of pollutants in the industrial park, the pollution risk in the area 5 km away from the centre increased year by year until it became stable in 2019, and the risk in the centre of the park reached 1 level, covered an area of up to 145400 square metres, accounted for 0.012% of the whole study area. The assessment results in 2020 and 2021 fluctuate slightly compared with those in 2019. Therefore, in terms of groundwater resource protection and resource management, it is necessary to focus on the detection of pollution in the coastal zone and the pollution within 5 km of the centre to strictly control pollution discharge. In this study, the comprehensive assessment includes surface indicators, subsurface indicators, and pollutant indicators. Finally, we achieve a multivariate, spatial and long time series groundwater pollution risk assessment system, which is a new groundwater environmental impact assessment (GEIA) system.

A groundwater risk assessment for irrigation purpose based on salinity indicators: applied to southeastern Tunisia.

Groundwater resources are increasingly under demand to support human activities and economic development. This naturally clean resource is threatened by human and natural pollutions. Protecting groundwater has become a challenge for both urban and rural communities. This work aims to develop a simple and effective approach to assess the risk of aquifer pollution and the delineation of risk zones. To do so, an aquifer risk index (ARI) was presented as an overall indicator of the risk of groundwater pollution. The ARI is calculated using the groundwater vulnerability index (GVI) and the normalized water quality index (WQI). The multi-linear regression (MLR) model was used to assign weights to each parameter. This model has been applied and validated in the Koutine area of southern Tunisia. The results revealed that the groundwater in the study area is characterized by low and moderate risk. Fifty-six percent (56%) of the total study area presents a low risk. The remaining 44% of the study area is classified as medium risk, primarily in the Wadi and Lowland plains. ARI considers the intrinsic characteristics of the aquifer and groundwater quality when assessing the risk of pollution. The approach developed for assessing groundwater risks is simple to implement, realistic, and efficient. AVI is a parametric approach that uses aquifer data without losing information. This method can assist academics and groundwater resource managers in delineating risk areas to protect groundwater resources from pollution.

Appraisal of groundwater pollution risk by combining the fuzzy AHP and DRASTIC method in the Burdur Saline Lake Basin, SW Turkey.

To ensure sustainable groundwater management, water resources must be protected in terms of quantity and quality. In this context, it is important to reveal the potential of existing groundwater resources to be affected by environmental and/or geogenic pollutants. In the present study, groundwater vulnerability assessment was performed using DRASTIC model by fuzzy AHP and GIS integration for Burdur Saline Lake basin, SW Turkey. In addition, validation and sensitivity analyses were performed in the study. Weight and rating values assigned for DRASTIC parameters and sub-parameters were determined by fuzzy AHP method, and these values were used in GIS analyses. In the validation analysis of the obtained groundwater vulnerability map, NO3 ion was considered since the agricultural activities are intense in the study area. In addition, sensitivity analyses were performed to determine the most effective parameter. According to the obtained results, 26.43% of the study area was determined as the highly vulnerable areas, while 11.44 and 62.13% were moderate vulnerable and low vulnerable, respectively. Impact of the vadose zone, depth to water table, and net recharge parameters were determined as more effective than other parameters. The nitrate concentrations of the groundwater in the region confirm the vulnerability map obtained by the study. Therefore, it is recommended to take realistic and urgent protection measures aimed at sustainable use of groundwater in highly vulnerable areas.

RISK ASSESSMENT OF NITRAT CONTAMINATED IN GROUNDWATER IN GIAO THUY DISTRICT, NAMDINH PROVINCE, VIETNAM

Environmental pollution due to agricultural production activities, and the use of fertilizers and pesticides is a matter of great concern due to its harmful effects on the soil environment, water environment, and ecosystems. In this study, the risk of nitrate contamination in shallow groundwater related to agricultural land was evaluated using DRATIC and IPNOA models with 66 soil samples and 132 groundwater samples. The results showed that hazard was found at very low with HI values ranging from 3.5-6.06. The RI of nitrate-contaminated groundwater from agricultural activities is in the range of 539 - 1058. The assessment results show that the vulnerability index has a significant impact on the RI index, and areas with a high vulnerability index have a higher risk of groundwater pollution. The NO3- concentration seems to be stable, ranging from 0.02 to 0.11 mg/l, and all meet with the QCVN 09:2018/BNTMT for groundwater quality. No clear correlation between vulnerability factor and risk factor with NO3- concentration in groundwater.

Discussion on Groundwater Pollution Control and Risk Prevention

Discussion on Groundwater Pollution Control and Risk Prevention

Groundwater pollution risk assessment using a calculated contamination index and geostatistical analysis: Jerba Island case study (southeast of Tunisia)

Groundwater pollution risk assessment using a calculated contamination index and geostatistical analysis: Jerba Island case study (southeast of Tunisia)

Glyphosate and AMPA have low mobility through different soil profiles of the prosecco wine production area: A monitoring study in north-eastern Italy

Contamination of the environment by glyphosate (GLP) and its metabolite aminomethylphosphonic acid (AMPA) is still of major concern worldwide due to specific interactions among these molecules and soil and water. Two monitoring sites were established in the Prosecco wine production area (Conegliano and Valdobbiadene) in northeastern Italy, which has been included in UNESCO’s World Heritage List since 2019. The study aims to increase the knowledge about GLP dynamics in this area where it has been intensively used by farmers and the potential risk for groundwater pollution is still debated. Each site was equipped with two soil-water monitoring stations consisting of multisensor soil probes and suction cups at three soil depths (10, 30, and 70 cm). Soil and water were sampled for 10 and 6 months, respectively, and analyzed for GLP and AMPA concentrations, for a total of 242 samples to describe their vertical movement and dissipation dynamics. Soil properties, in particular, the different forms of Fe and Al oxide contents, and Freundlich adsorption coefficients were quantified along the soil profile. First attempts showed that glyphosate dissipation time was 36 ± 8 days in Conegliano and Valdobbiadene soils and fully completed in both after 6 months. In contrast, AMPA dissipation dynamic —first described by an original equation—was longer than that of GLP and fully dissipated after almost 300 days. GLP showed a strong binding affinity with clay and Fe and Al chelated to soil organic matter, which likely acted as cation bridges and in turn led to low GLP mobility. GLP and AMPA were mostly detected after heavy rainfall events at 70 cm depth, likely bypassing the porous matrix of the intermediate layers.

Response relationship of environmental factors caused by toluene concentration during leaching of capillary zone.

Due to the leaching of capillary water, the petroleum pollutants initially trapped in vadose zone may migrate to lower aquifer, thus increasing the risk of groundwater pollution. In order to explore the effect of capillary leaching on toluene-contaminated soil and the relationship between toluene concentration (TC) and environmental factors (EFs) during the leaching process, the sterilized and non-sterilized soil column experiments were designed. The EFs were used to estimate TC. The results showed that the difference between leaching and volatilization rates directly determined the changing trend of toluene concentration in capillary water. The toluene concentration in the medium always showed decreasing trend due to leaching. The indigenous microbial community structure of the non-sterilized soil column was analyzed by 16S rRNA sequencing. It was found that indigenous microorganisms could degrade toluene after 33.0 days of acclimatation. The microbial population was dominated by bacteria, among them the Ellin6055 strain and Pseudomonas, Pseudoxanthomonas, Cupriavidus, Bdellovibrio, Sphingobium, Phenylobacterium, Ramlibacter, Bradyrhizobium, Shinella genera. The Pseudomonas was the most crucial bacterial genus that degraded toluene. Indigenous microbial degradation was the fundamental reason for strong response relationship. Furthermore, we suggested a relationship of function between environmental factors (pH, DO, ORP) and time (t) for toluene attenuation: C0+ln(eAtαBγCβ)=CToluene, (α, β, γ represent the pH, DO, and ORP in leaching capillary water, respectively; A, B, and C represent undetermined coefficients), and the fitting coefficient R2>0.950. This relationship can only characterize the attenuation process of capillary zone leaching on toluene. However, it may still be utilized to give a theoretical foundation for understanding the dynamic of pollutant concentration change processes under specific environmental factors.

Effect of cationic, anionic and non-ionic surfactants on transport of microplastics: Role of adhesion of surfactants on the polyethylene surface

• Anionic, cationic, and nonionic surfactants all promote PE transport. • The greater adhesion of surfactants on the PE surface cause stronger PE transport. • Adhesion of surfactant on PE is related to the minimum single molecule adsorption area. In view of the amphiphilicity of surfactants, which can improve the hydrophilicity of polyethylene (PE) microplastics and increase the mobility of PE microplastics, the research on the transport behavior of PE microplastics under the coexistence of surfactants is still lacking and necessary. In this work, column experiments were carried out on the suspensions made of 15 surfactants mixed and dispersed with PE microplastics to explore the promoting effect of various surfactants on the transport of PE in saturated porous media. The dynamic contact angle of surfactant on PE surface and the surface tension and zeta potential of PE / surfactant dispersion system were measured. The interaction energy between PE / surfactant and medium, the adhesion of surfactant on PE surface were calculated respectively according to DLVO theory and Young's equation. The experimental results showed that different surfactants promoted the transportation of PE in the column to different degrees. The promotion degree of cationic, anionic and nonionic surfactants on PE transport from large to small were BG > PQ28 > CTAB > BLB > TLB, SDS > SLDED > DSS > SL > SDBS, POES > T40 > T80 > X100 > TX20, respectively. The recovery of PE in the column ranged from 17% to 99.93% under the surfactants. The calculation results of the adhesion of surfactant on PE surface also showed the same law. The minimum single molecule adsorption area (A sL ) of surfactant on PE surface was negatively correlated with the recovery of PE in the column under the same type of surfactant. The high adhesion of surfactant on PE surface was caused by the small adsorption area of single molecule, which finally made PE obtain higher stability and penetration. These findings provide new insights and methods for the fate and transport of microplastic and surfactant coexisting systems in soil and the prediction of their potential risk of groundwater pollution.

Agricultural practices regulate the seasonality of groundwater-river nitrogen exchanges

Soil System Budgets (SSB) of nutrients are generally performed annually over arable land to infer their use efficiency and water pollution risk in highly exploited agricultural watersheds. They are seldom partitioned into seasonal budgets and matched with seasonal nutrient transport in adjacent river reaches. We calculated seasonal soil nitrogen (N) budgets in a Mincio River sub-basin (Italy), and we analyzed the dissolved inorganic N net export in the river reach draining such sub-basin. Our results show seasonal differences of SSB with N excess in winter and even more in spring, equilibrium among sources and sinks during autumn and N deficit during summer. Seasonal inorganic N loads transported by the river were not correlated with SSB as they peaked in late summer and were at their minimum in early spring. Fertilization uncoupled to significant uptake supports N excess in winter and spring, whereas crop uptake uncoupled to N inputs supports summer N deficit. Nitrification cannot explain nitrate accumulation in the river reach, suggesting alternative dynamics driving the local hydrology. Flood irrigation results in large soil nitrate solubilization, transport and in upward migration of the groundwater piezometric head during spring and summer periods. River water is likely replaced by nitrate-rich groundwater when the groundwater recharge exceeds a certain threshold coinciding with late summer. Irrigation is then interrupted and the piezometric head, together with nitrate exchange, decreases. This work suggests that a deep understanding of N dynamics in agricultural watersheds with flooding irrigation on permeable soils needs the reconstruction of the vertical pathways of nitrate and of river-groundwater interactions. Moreover, the partitioning of annual into seasonal N budgets and their combination with irrigation practices allows the identification of hot moments in N cycling. Agricultural practices minimizing nitrate excess, its mobility and the risk of surface and groundwater pollution are suggested for this area.

Groundwater Contamination Risk Assessment Based on Groundwater Vulnerability and Pollution Loading: A Case Study of Typical Karst Areas in China

Groundwater contamination risk assessment is an important basis to support the protection of the groundwater ecological environment. In this research, the groundwater contamination risk in typical karst areas in China was evaluated by PLEIK model (P: protective cover; L: land use; E: epikarst development; I: infiltration conditions; K: karst development) and classification and discrimination methods were used to assess groundwater vulnerability and pollution source load; the water quality index method was used to assess the status of groundwater contamination in the research area. The results show that groundwater vulnerability values in the research area range from 3.04 to 7.79, and most areas have low groundwater vulnerability. Groundwater pollution loading indexes, in the region of the pollution sources, gathered numerical up-water quality status evaluation that shows that most of the regional groundwater quality in the research area has good groundwater at present. The groundwater contamination risk assessment results show that the groundwater pollution risk is mainly at a very low level in most areas of the study area, but the groundwater pollution risk is higher in the areas where the pollution sources gather. The result reveals that the regional groundwater contamination risk level for regional groundwater ecological environment protection provides a theoretical basis for policy making.