Risk Of Groundwater Pollution Research Articles

Prediction and evaluation of groundwater characteristics using the radial basic model in Semi-arid region, India

ABSTRACT Accuracy in groundwater quality monitoring plays a vital and decisive role in environment eco-system, human health and agriculture practices. The present study aims to identify the relationship between the water quality parameters and sources of contamination using radial basic function (RBF) networks. The primary focus of the study is to understand the prioritisation of ionic concentration in terms of groundwater quality. Additionally, the multivariate statistical analysis of groundwater for 30 sample locations was carried out in the present study. Piper and Gibbs plot divulged that, rock-water interaction, ion exchange process, weathering of host rocks are the primary process that influences the groundwater quality in the study area. The principal component analysis (PCA) of groundwater confirmed that two phenomena such as geogenic and anthropogenic activities govern the chemical composition of groundwater. These major phenomena are validated by Hierarchical Cluster Analysis (HCA) and K-mean cluster analysis. The RBF network reveals that anion (R2 = 0.95) plays a vital role in the quality of groundwater than cations (R2 = 0.901). The major sources of contamination observed in the study area are weathering of host rocks, ion exchange process, excess utilisation of synthetic fertilisers. The leachate of dumping yards and agriculture field are might be the source of higher concentration of anions in the groundwater chemistry, and it leads to an increase the value of pH in groundwater. The integrated approach of the present study suggests that remedial measure to be followed to avoid the contamination of groundwater in the study area. The research findings may provide useful information to the decision-maker regarding the groundwater pollution risk management mainly in arid and semi-arid regions.

Evaluating Potential for Groundwater Contamination from Surface Spills Associated with Unconventional Oil and Gas Production: Methodology and Application to the South Platte Alluvial Aquifer

Surface spills occur frequently during unconventional oil and gas production operations and have the potential to impact groundwater quality. A screening-level analysis using contaminant fate and transport simulations was performed to: (1) evaluate whether hypothetical (yet realistic) spills of aqueous produced fluids pose risks to groundwater quality in the South Platte Aquifer, (2) identify the key hydrologic and transport factors that determine these risks, and (3) develop a screening-level methodology that could be applied for other sites and pollutants. This assessment considered a range of representative hydrologic conditions and transport behavior for benzene, a regulated pollutant in production fluids. Realistic spill volumes and areas were determined using publicly available data collected by Colorado’s regulatory agency. Risk of groundwater pollution was based on predicted benzene concentrations at the groundwater table. Results suggest that the risk of groundwater contamination from benzene in a produced water spill was relatively low in the South Platte Aquifer. Spill size was the dominant factor influencing whether a contaminant reached the water table. Only statistically larger spills (volume per surface area ≥12.0 cm) posed a clear risk. Storm events following a spill were generally required to transport typical (median)-sized spills (0.38 cm volume per surface area) to the water table; typical spills only posed risk if a 500 or 100 year storm (followed by little degradation or sorption) occurred right after the spill. This methodology could be applied to evaluate spills occurring over other aquifers.

Effect of the biogenic precipitation of calcium carbonate on bacterial transport in sand columns

Prediction of bacteria transport to riparian shallow groundwater is very important to prevent the pollution of water resources by coliform bacteria. The objective of this study was to investigate the effectiveness of microbially induced calcium carbonate precipitation (MICCP) in reducing bacteria (Escherichia coli and Pseudomonas fluorescens) transport. To perform the MICCP process, air-dried sterile sand was poured into polyvinyl chloride (PVC) cylinders (4.8 × 14.92 cm) and incubated for 3 days in the presence of Sporosarcina pasteurii (~108 Cell g−1sand), urea and CaCl2 (1.5 M). A pulse (0.1 pore volume (PV)) of bacteria suspension (108 CFU mL−1) was added on top of the sand columns (MICCP treated and control) and leaching experiments were followed at steady-state, saturated flow condition. Culturable bacteria were determined in the leachate and the sand extracts (resident bacteria) by colony count method. The MICCP treatment reduced saturated hydraulic conductivity (Ks) value 3.9 times compared to the control and thereby reduced bacteria leaching. Bioprecipitated calcium carbonate in MICCP columns increased bacteria straining compared to control columns especially in surface layer (0-3 cm). MICCP process increased filtration coefficient (λf), and relative adsorption index (SR), and decreased maximum depth of bacteria transport (Zmax). The average (Cav) and cumulative cell density (Ccum) of both bacteria passed from the MICCP column decreased around 3.9-fold compared to the control. Overall, the MICCP process has potential in bacteria filtration in the porous media reducing the risk of groundwater pollution.

Design of mass burial sites for safe and dignified disposal of pandemic fatalities

The huge number of fatalities due to the coronavirus disease 2019 pandemic has imposed an unprecedented pressure on existing burial facilities. Thus, mass burial is being used in different parts of the world to cope with this unusual situation. As a dead body might be contagious for at least hours, if not days, there is a need to manage/design/construct the mass burial considering the safe handling of coffins and other environmental, social, economical and ethical/dignity aspects. However, the guidelines of the World Health Organization do not thoroughly address the potential risk associated with groundwater pollution due to mass burial construction. Hence, the present study discusses the potential risk of groundwater pollution in mass burial sites and sheds light on the factors that control the survival/retention of bacteria and viruses in porous media. Furthermore, using the available knowledge on designing/monitoring of municipal/industrial waste disposal sites, a cost-effective and simple construction method of mass burial is proposed to mitigate its potential environmental impact.

Study of Groundwater Vulnerability to Contamination in Part of the Klaten District Area, Central Java-Indonesia

Water demands and risks of groundwater pollution in the Klaten District consistently increase as the human population grows over the years. This study aimed to examine the intrinsic and specific groundwater vulnerability levels (low, moderate, high) and analyze the spatial distribution and degree of contribution of the parameters to the vulnerability in some parts of the district area. The data included depth to the water table (measured directly at selected wells), rainfall records in 2009–2019, land-use maps (RBI), 30m DEM (SRTM), geological maps and geoelectric data. Groundwater vulnerability was analyzed with the Susceptibility Index by overlaying five parameters, which according to the results varied across the district: shallow to deep groundwater, aquifers that were composed of sandstone, sand and gravels and rock materials in between, topography of <2%and 2–6% and diverse land-use types from agricultural fields to built-up lands. Most of the research area had moderate intrinsic and specific vulnerability (43.93% and 50.53%), followed by high (38.24% and 46.43%) and low (17.83% and 3.04%). Also, depth to the water table and land use are the most influencing parameters. The results of this study are expected to provide a reference for the government to consider factoring in priority areas based on groundwater vulnerability levels in formulating the district’s spatial plan.

Groundwater pollution risk in the region of Bouira (north center of Algeria): origin and consequences on health

Groundwater is often the preferred source for human consumption, irrigation and industry. In Algeria, many people count on well water for their drinking water supply and irrigation of agricultural lands; especially in rural areas, which is a strategic reserve of which quality must be assured. Groundwater protection requires the detection of origins of pollution and its consequences on the ecological system. The region of Bouirahas seen water-borne diseases occurrence caused by groundwater pollution, which has led us to look for the origin of this problem. It is considered like a high-risk area because it has recorded a large number of Toxi-food collective, Viral Hepatitis A, typhoid fever and Choléra cases in 2018. The study carried out based on the potential risks to human health and the GIS for a period of eight years (from 2008 to 2015), has allowed us to the elaboration of water-borne disease mapping of the whole region and to find that the most affected municipalitie sare: Bouira, Sour El Ghozlene, Lakhdaria and Ain Bessem .The correlation between these diseases and the irrigated perimeters by wadis is very strong in this municipalities.

Migration and speciation transformation mechanisms of mercury in undercurrent zones of the Tongguan gold mining area, Shaanxi Loess Plateau and impact on the environment

In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment, the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess, alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province, and the following results were obtained: (1) The source of Hg in subsurface flow zone is mainly caused by mineral processing activities; (2) the subsurface flow zone in the study area is in alkaline environment, and the residual state, iron and manganese oxidation state, strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment; mercury in river alluvial or diluvial strata is mainly concentrated in silt, tailings and clayey silt soil layer, and mercury has certain stability, and the form of mercury in loess is easier to transform than the other two media; (3) under the flooding condition, most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed, and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection; (4) infiltration at the flood level accelerates the migration of pollutants to the ground; (5) the soil in the undercurrent zone is overloaded and has seriously exceeded the standard. Although the groundwater monitoring results are safe this time, relevant enterprises or departments should continue to pay attention to improving the gold extraction process, especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes, and intensify efforts to solve the geological environmental problems of mines left over from history. At present, the occurrence form of mercury in the undercurrent zone is relatively stable, but the water and soil layers have been polluted. The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links. The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.

Groundwater Pollution and Human Health Risks in an Industrialized Region of Southern India: Impacts of the COVID-19 Lockdown and the Monsoon Seasonal Cycles.

Samples of groundwater were collected during a post-monsoon period (January) and a pre-monsoon period (May) in 2020 from 30 locations in the rapidly developing industrial and residential area of the Coimbatore region in southern India. These sampling periods coincided with times before and during the lockdown in industrial activity and reduced agricultural activity that occurred in the region due to the COVID-19 pandemic. This provided a unique opportunity to evaluate the effects of reduced anthropogenic activity on groundwater quality. Approximately 17% of the wells affected by high fluoride concentrations in the post-monsoon period returned to levels suitable for human consumption in samples collected in the pre-monsoon period. This was probably due to ion exchange processes, infiltration of rainwater during the seasonal monsoon that diluted concentrations of ions including geogenic fluoride, as well as a reduction in anthropogenic inputs during the lockdown. The total hazard index for fluoride in the post-monsoon samples calculated for children, adult women, and adult men indicated that 73%, 60%, and 50% of the groundwater samples, respectively, had fluoride levels higher than the permissible limit. In this study, nitrate pollution declined by 33.4% by the pre-monsoon period relative to the post-monsoon period. The chemical facies of groundwater reverted from the Na-HCO3-Cl and Na–Cl to the Ca-HCO3 type in pre-monsoon samples. Various geogenic indicators like molar ratios, inter-ionic relations along with graphical tools demonstrated that plagioclase mineral weathering, carbonate dissolution, reverse ion exchange, and anthropogenic inputs are influencing the groundwater chemistry of this region. These findings were further supported by the saturation index assessed for the post- and pre-monsoon samples. COVID-19 lockdown considerably reduced groundwater pollution by Na+, K+, Cl–, NO3¯, and F– ions due to shutdown of industries and reduced agricultural activities. Further groundwater quality improvement during lockdown period there is evidence that the COVID-19 lockdown by increased HCO3¯ ion concentration. Overall results illustrate the positive benefits to groundwater quality that could occur as a result of measures to control anthropogenic inputs of pollutants.

Research on Prevention and Control of Risk Index of Groundwater Pollution System in Northeast China

The background of this paper is that groundwater pollution risk assessment and zoning is an important basis for regional groundwater resources protection. The research progress and deficiency of Groundwater Hazard Risk Assessment at home and abroad are analyzed. Based on the data of 18 water quality indexes such as ammonia and nitrogen in 18 groundwater monitoring sites in Jinzhou area, the pollution factors and pollution sources were analyzed with the improved Mero comprehensive index. At present, due to the long-term exploitation of shallow groundwater in the west of Liaoning Province, the pollution degree of the groundwater is relatively large, and the cause of the pollution is unknown. The research methods are literature research and case analysis. On the basis of defining the risk of groundwater pollution, the index system of groundwater pollution risk assessment and the index system of groundwater pollution risk assessment are established. The results show that nitrate is the main factor of regional groundwater pollution, and the contribution of variance is 49.30%. Domestic sewage is the main source of regional shallow groundwater pollution. At the same time, an improved Mero composite index was proposed to strengthen the control of domestic sewage and agricultural non-point source pollution in Jinzhou, and to strengthen groundwater recharge, the impact of transgression on groundwater quality in Jinzhou should also be the focus of follow-up studies.

Modeling the Impact of Fertilizers on Groundwater Quality in Hormat-Golina Sub-basin, Golina-Basin, Ethiopia

Groundwater, in many parts of the world, is under risk as a result of excessive withdrawal, mismanagement and contamination. A number of studies have been carried out in this respect, but most of them have not predicted groundwater quality concerning anthropogenic stress. As opposed to this, in this study, groundwater fluctuation with respect to human pressure was investigated in Hormat-Golina Sub-basin of the Golina-Basin of Ethiopia. Visual MODFLOW Flex 5.1 model was used to simulate groundwater flow in response to different stress periods in the study area. The study showed that the initial concentration values were measured in each nutrient chemical species. The impacts of climate change and human pressure on groundwater have been the greatest threats in those supply wells. Decreased in pumping rate with increased recharge rate has accomplished to restore and protect the groundwater resources which is the best option for groundwater restoration and monitoring. Anthropogenic pressures including the application of fertilizers were a considerable cause of degraded groundwater quality in relation to Nitrate and Phosphate concentration with series of time. The groundwater quality has deteriorating with the applied Urea and DAP fertilizes in the selected wells of Hormat-Golina Sub-basin. Farmers have encouraged using practices that minimize the risk of groundwater pollution by carefully controlling and timing of the use of fertilizers to avoid over application.

Translating the agricultural N surplus hazard into groundwater pollution risk: Implications for effectiveness of mitigation measures in nitrate vulnerable zones

In the Nitrate Vulnerable Zones farmers are required to implement measures to reduce the nitrogen (N) surplus. Nevertheless, in some cases the status of the water bodies show that the effect of these measures remains insufficient despite the global decrease in N surpluses. The present work aims to contribute with a method that produces an appropriate indicator for the N mitigation measures effectiveness for reducing groundwater nitrate pollution. The Global Risk Index (GRI) results from overlaying the agricultural N surplus hazard and aquifer vulnerability. It includes both irrigation activity and precipitation contribution to water recharge calculated at the municipality level. It integrates a range of regional datasets combined with monitored nitrate (NO3−) concentrations in groundwater under a GIS framework. Results show that the pollution status of the Tagus Vulnerable Zone (TVZ) aquifers has been aggravating in spite of the overall reduction in the N surpluses that resulted from the implementation of the Nitrates Directive measures. Twelve years after the TVZ designation, the GRI indicates high and moderate NO3- pollution risk, respectively in 33 % and 66 % of the territory. Scenario analysis indicates the potential of targeted measures for ending high risk areas and reducing moderate risk areas to 13 %. This supports that N mitigation measures must be reformulated and spatially targeted according to site specific hazards and vulnerabilities.

Impacts and social implications of landuse-environment conflicts in a typical Mediterranean watershed

In coastal watersheds, services and landuse favour coastal tourism and urbanization, depriving rural upstream of infrastructure and attention. This unbalanced management leads to an intensification of socioeconomic changes that generate a structural heterogeneity of the landscape and a reduction in the livelihoods of the rural population. The incessant dissociation between the objectives of the stakeholders triggers landuse-environment-economy conflicts which threaten to mutate large-scale development programs. Here, we used multi-assessment techniques in a Mediterranean watershed from Morocco to evaluate the effects of landuse change on water, vegetation, and perception of the rural population towards environmental issues. We combined complementary vegetation indexes (NDVI and EVI) to study long-term landuse change and phenological statistical pixel-based trends. We assessed the exposure of rural households to the risk of groundwater pollution through a water analysis supplemented by the calculation of an Integrated Water Quality Index. Later, we contrasted the findings with the results of a social survey with a representative sample of 401 households from 7 villages. We found that rapid coastal linear urbanization has resulted in a 12-fold increase in construction over the past 35 years, to the detriment of natural spaces and the lack of equipment and means in rural areas upstream. We show that the worst water qualities are linked to the negative impact of anthropogenic activities on immediately accessible water points. We observe that rural households are aware of the existence and gravity of environmental issues but act confusedly because of their low education level which generates a weak capacity to understand cause and effect relationships. We anticipate the pressing need to improve the well-being and education of the population and synergistically correct management plans to target the watershed as a consolidated system. Broadly, stakeholders should restore lost territorial harmony and reallocate landuse according to a sustainable environment-socioeconomic vision.

Multi-criteria decision making and fairness evaluation of water ecological carrying capacity for inter-regional green development.

Determining water ecological carrying capacity (WECC) is of great significance to ensure inter-regional green development. This study presents a comprehensive evaluation framework for WECC assessment in the Yangtze River Economic Zone (YREZ), China. Effects of water resources, socio-economic, and ecological elements on WECC can be evaluated based on multi-criteria decision analysis. Gini and unbalance coefficients are used for measuring the regional fairness between WECC and socio-economic development. Surface water production pressure (SWPP) and groundwater pollution risk (GPR) are further regarded as indicators for expressing water resources constraint on shale gas extraction in the YREZ. Results disclose that the average WECC level decreases from 0.439 in 2000 to 0.4007 in 2016, which is the opposite of the changing trend in the Beijing-Tianjin-Hebei Region. A high WECC level appears in Zhejiang (0.5126) with a good state, but that of Guizhou (0.3983), Anhui (0.3968), Hunan (0.3914), and Chongqing (0.3651) are at the alert state. The obstacle factors of WECC in the eastern YREZ mostly originate from socio-economic and water resource subsystems, while that in the middle and western YREZ mainly arise from water resources and ecological subsystems. Fairness analysis shows a well-matching characteristic between the overall WECC and socio-economic performances due to a majority of their Gini coefficients lower than 0.4, while a poor matching characteristic exists in terms of provincial differences owing to their varied unbalance coefficients, especially in Guizhou, Jiangsu, and Shanghai. Moreover, Chongqing with most of shale gas reserves is characterized by slight SWPP (1.0202) and GPR (0.0188), but the prospect of shale gas development in Sichuan is not optimistic due to its high SWPP (1.0846) and GPR (0.0647). Recycling of flowback and product waters can significantly lighten regional water resources pressure. This presented framework can be applied into many other Chinese cities (e.g., Beijing-Tianjin-Hebei Region) with slight modifications according to their actual situations for supporting water resource managers and government with decision making.

Vertical distribution and affecting factors of Escherichia coli over a 0–400 cm soil profile irrigated with sewage effluents in northern China

Quantification and evaluation of the spatial distribution and the primary factors that affect Escherichia coli (E. coli) distribution in soils is important to assess soil pollution and potential contamination of groundwater. However, little information is available on distribution of E. coli in deep soil layers. To analyze the spatial distribution and factors affecting E. coli over a 0–400 cm soil profile, soil samples were collected from two land use type in the sewage irrigation fields. The primary factors dominating the spatial distribution of E. coli were quantified by the model of principal component analysis with multiple linear regression (PCA-MLR). The results indicated that the number of E. coli under cropland decreased greatly with soil depth. The average number of E. coli over the 0–400 cm profile under forestland was 49 × 104 colony-forming unit/g (cfu/g), which was significantly higher than that under cropland (20 × 104 cfu/g). For forestland and cropland, the average number of E. coli at depths of 300–400 cm decreased by 85% and 88%, respectively, compared to that at depths of 0–100 cm. The presence of E. coli at the depths of 300–400 cm was at high level (forestland: 3 × 104 cfu/g; cropland: 2 × 104 cfu/g) for the potential risks of shallow groundwater. The PCA-MLR model estimated that the factors of soil organism, soil salt and land type use contributed 28%, 29% and 43%, respectively, to the distribution of E. coli. According to the Monte Carlo simulation, the average number of E. coli over the 0–400 cm profile was 46 ± 17 × 104 cfu/g in the sewage irrigated area, and the interval distribution with a probability of 95% varied between 14 × 104 cfu/g and 78 × 104 cfu/g. The findings of this study are useful for understanding negative effects of sewage irrigation on pathogens in deep soil and are critical to assess the potential risks of groundwater pollution.

Coconut husk biochar amendment enhances nutrient retention by suppressing nitrification in agricultural soil following anaerobic digestate application.

Anaerobic digestate and biochar are by-products of the biogasification and pyrolysis of agricultural wastes. This study tested the hypothesis that combined application of anaerobic pig/cattle manure digestate and coconut husk (CH) biochar can improve soil nutrient conditions, whilst minimizing atmospheric and groundwater pollution risks. Microcosms simulated digestate application to agricultural soil with and without CH biochar. Ammonia volatilization and nutrient leaching were quantified after simulated heavy rainfalls. Archaeal and bacterial community and abundance changes in soils were quantified via next generation sequencing and qPCR of 16S rRNA genes. Nitrifying bacteria were additionally quantified by qPCR of functional genes. It was found that CH biochar retarded nitrate leaching via slower nitrification in digestate-amended soil. CH biochar reduced both nitrifying archaea and bacteria abundance in soil by 71–83 percent in the top 4 cm soil layer and 66–80 percent in the deeper soil layer one month after the digestate application. Methanotroph abundances were similarly reduced in the CH biochar amended soils. These findings demonstrate combined benefits of anaerobic digestate and CH biochar application which are relevant for the development of a more circular rural economy with waste minimization, renewable energy production, nutrient recycling and reduced water pollution from agricultural land.

An Overview of Numerous Techniques for Groundwater Pollution Risk Zone Assessment

An Overview of Numerous Techniques for Groundwater Pollution Risk Zone Assessment

COMPACTION CHARACTERISTICS OF A FINE-GRAINED SOIL POTENTIAL FOR LANDFILL LINER APPLICATION

Increasing population growth and urbanization results in increased demand for waste disposal processes and facilities that can protect public health and the environment. In the Philippines, there is a great demand to construct sanitary landfills (SLF) with only 387 local government units (LGUs) or equivalent to 23.86% compliant to date with Republic Act 9003 which mandates all LGUs to use the sanitary landfill. The compaction characteristics of a locally abundant fine-grained soil at different compaction energy levels were investigated as part of a broader study in the suitability of the soil as a landfill liner material. Compaction is essential in the preparation of a well-compacted soil liner in a sanitary landfill to avoid or minimize the migration of leachate and thereby reduce the risk of groundwater pollution. The physical properties are determined through a series of laboratory tests which covers the grain-size distribution, specific gravity, Atterberg limits, soil classification, XRD and SEM-EDX. Correlations to estimate the compaction characteristics at any rational compaction energy (E) are developed. The maximum dry unit weight values at different compactive efforts were used to determine void ratios which were then utilized to compute for the saturated hydraulic conductivity using numerical model for hydraulic conductivity for the same soil type. The resulting hydraulic conductivity ranges from 2.30 x 10-7 to 1.20 x 10-7 cm/sec well above the required value in the Philippines as per RA 9003 and its IRR for the intended Category I and II SLFs application

The Potential Pollution Risk of Groundwater by a Ceramic Permeable Brick Paving System

To investigate the potential pollution risk of permeable brick paving systems in areas with high groundwater levels, a system was constructed by using ceramic permeable bricks as the surface and a Chinese character “well”-shaped frame as the base on the top of a 1.0 m clay layer. The concentrations of total suspended solids (TSS), total phosphorus (TP), ammonia nitrogen (NH4+-N), total nitrogen (TN), chemical oxygen demand (COD), and heavy metals (Zn, Cu, and Pb) at different underground depths were measured, the potential pollution of the groundwater was assessed, and the effectiveness of the fillers inside the frame for improving the quality of the groundwater was discussed. The results showed that NH4+-N and COD concentrations detected at the depth of 0.6 m were higher than that of the national standard for groundwater (GBT14848-2017), these two pollutants had the potential pollution risk. The pollution risk by heavy metals was comparatively low because most of the heavy metals were likely retained in the surface soil by adsorption, complexation, and precipitation, while the pollution risk by TSS and TP was negligible due to the good purification ability in the clay layer. The results suggest that the removal rates of TSS, TP, TN, COD, and heavy metals can be improved by appropriate fillers’ adjustment, such as iron filings, coal slag, or volcanic rocks. This research offers a new perspective on the potential risk of pollution and the governance of groundwater.

Study on the risk assessment and forewarning model of groundwater pollution

In the purview of groundwater pollution, a rational exploitation, utilization, protection, and risk assessment of groundwater has become an important means of groundwater management and pollution prevention. Xiashan Economic Zone of Weifang City which is located in the central region of the Shandong Peninsula, China, has been chosen to investigate the risk assessment of pollution by heavy metals (Pb, Cr, Cd, and Hg) permeating into groundwater periodically through the soil layers or the vadose zone. This study deals with the risk assessment and forewarning model of groundwater pollution by the use of comprehensive risk index method along with GIS overlay analysis and groundwater pollution forewarning system. Soil samples (n = 988) and water samples (n = 327) from groundwater resources of Xiashan Economic Zone and eight major factors, i.e., runoff factor, overburden strata factor, atmospheric precipitation factor, pollutant source type, pollutant generation quantity, pollutant release possibility, water yield from aquifers, and groundwater conservation district, have been thoroughly studied. Based on data analysis and study, groundwater pollution risk assessment zonation map and groundwater forewarning distribution map were established. The results show that the distribution area accounting for 3.07% of the total area is of medium warning with high risk of pollution. Mainly spread on both banks of the river, the serious warning zone is covering 26.80% of the total area for groundwater, and the groundwater is distressed with a risk of moderate pollution. While the tremendous warning area for groundwater pollution is distributed in over 70.13% of the total area, thus, putting in a state of high-risk pollution. The warning degree of groundwater pollution in typical water source areas was identified, and the possible alarming warning instance can be forecast. Based on the warning degree, the governance protection area and key protection area were divided. The corresponding prevention and control measures were put forward after formulating the prevention and control plan of groundwater pollution based on this kind of study.

Modelling the Temporal Dynamics of Groundwater Pollution Risks at the African Scale

Groundwater pollution risk modelling is an important asset to improve groundwater management and protection. In this study, we assess the temporal dynamics of groundwater pollution risk at the continental scale, using the DRASTIC model. The approach was developed using continental-scale data on soil properties, topography, land use, geology, hydrogeology, and climate with a resolution of 15 × 15 km2. We compared continental-scale groundwater pollution risk for the years 1990, 2000, and 2010. The results showed significant inter-annual variations of the spatial distribution of pollution risk. Changes were mainly concentrated in the area of the Nile Delta, around the Lake Victoria, in North Africa, and in coastal West Africa (predominately in Nigeria). We found that the increase in pollution risk was mainly related to the increase in the population density in these regions. The proposed methodology for modelling the temporal dynamics of groundwater pollution risk could support the monitoring of the Sustainable Development Goal 6, which focus in particular on the preservation of the freshwater resources against future threats.