Assessment of background levels and pollution sources for arsenic and fluoride in the phreatic and confined groundwater of Xi'an city, Shaanxi, China

Implications of atrazine concentrations in drinking water from Ijebu-North, Southwest Nigeria on the hypothalamic-pituitary-adrenal axis

There is an increasing overdependence and use of atrazine herbicide for the control of pre-and post-emergence broad leaf weeds on maize farms in rural agricultural communities in Nigeria. We carried out a survey of atrazine residue in 69 hand-dug wells (HDW), 40 boreholes (BH) and 4 streams from all the 6 communities (Awa, Mamu, Ijebu-Igbo, Ago-Iwoye, Oru and Ilaporu) in Ijebu North Local Government Area, Southwest Nigeria. The effect of the highest concentration of atrazine detected in the water from each of the communities on the hypothalamic-pituitary-adrenal (HPA) axis of albino rats was investigated. Varying concentrations of atrazine were detected in the HDW, BH and stream waters sampled. The highest concentration of atrazine recorded in the water from the communities ranged from 0.01 to 0.08 mg/L. Although there were no significant differences (p > 0.05) in serum levels of corticosterone, aldosterone and ROS of rats exposed to 0.01, 0.03 and 0.04 mg/L concentrations of atrazine compared to control, a significant increase (p < 0.05) was observed at 0.08 mg/L. Catalase activity increased significantly (p < 0.05) only at 0.03 and 0.04 mg/L of atrazine exposure. Butyrylcholinesterase activity, lipid peroxidation and serum ACTH of rats exposed to all the atrazine concentrations were not significantly different (p > 0.05) compared to control. Atrazine at environmentally relevant concentrations of 0.01, 0.03 and 0.04 mg/L detected in the water may not affect the HPA axis, attention should be given to 0.08 mg/L, which increases the serum corticosterone and aldosterone of the exposed rats.

Assessment of landcover impacts on the groundwater quality using hydrogeochemical and geospatial techniques

Groundwater quality is influenced by urbanization and land use land cover (LULC) changes. This study investigated their impact on groundwater quality in Quetta City, Pakistan, from 2015 to 2021. About 58 groundwater samples from monitoring wells were analyzed using hydrogeochemical and statistical methods. The water quality index (WQI), Wilcox, USSL, and various agricultural indices were employed to assess water quality trends. LULC analysis and NDVI using Sentinel-2 imagery revealed increased urban and agricultural areas and decreased barren land. Rapid urbanization was evident, with the buildup class expanding by 7.50% during this period. NDVI findings emphasized monitoring vegetation health and water quality for environmental assessments. The groundwater in Quetta was primarily classified as Cl-Ca·Mg, Cl-Ca, and Cl-Na according to the Piper diagram, with water-rock interactions and rock weathering evident. Most groundwater samples were suitable for irrigation according to the Wilcox and USSL diagrams. The WQI demonstrated overall safety for human consumption, but declining WQI values in northern parts due to urbanization are concerning. The results also revealed a moderate positive relationship between landcover classes and WQI values. It can be concluded that urbanization and excessive use of pesticides contributed to declining agricultural land quality. The spatial overlay of agricultural indices with landcover class suggested that barren land was most suitable, followed by build-up and agriculture were suitable for drinking and agriculture purposes. Moreover, agricultural indices moderately declined due to excessive fertilizers and pesticides in the agriculture landcover class. Thus, effective water resource management is crucial to address challenges. This comprehensive study serves as a baseline for future research and recommends larger-scale studies to implement efficient management strategies, urbanization planning, and safe irrigation and drinking water practices to prevent groundwater pollution.

Hydrogeochemical characterization and natural background level determination of selected inorganic substances in groundwater from a semi-confined aquifer in Midwestern Burkina Faso, West Africa

Hydrogeochemical processes that govern selected inorganic substances distribution in a semi-confined aquifer were characterized using traditional hydrogeochemical approaches and natural background levels (NBLs). Saturation indices and bivariate plots were used to investigate the effects of water-rock interactions on natural evolution of the groundwater chemistry, whereas Q-mode hierarchical cluster analysis and one-way analysis of variance classified the groundwater samples into three distinct groups. To highlight the groundwater status, NBLs and threshold values (TVs) of the substances were calculated using pre-selection method. Piper's diagram showed that the Ca-Mg-HCO₃ water type was the only hydrochemical facies of the groundwaters. Although all samples, except a borewell with a high NO₃^- concentration, had major ion and transition metal concentrations within the World Health Organization's recommended guideline values for drinking water, Cl^-, NO₃^- and PO₄^3- exhibited scattered distribution patterns, reflecting their nonpoint anthropogenic sources in the groundwater system. The bivariate and saturation indices revealed that silicate weathering and possible gypsum and anhydrite dissolution contributed to the groundwater chemistry. In contrast, NH₄⁺, Fe_T and Mn abundance appeared to be influenced by redox conditions. Strong positive spatial correlations between pH, Fe_T, Mn and Zn suggested that mobility of these metals was controlled by pH. The relative high F^- concentrations in lowland areas may imply the impact of evaporation on this ion's abundance. Contrary to TVs of HCO₃^-, those of Cl^-, NO₃^-, SO₄^2-, F^- and NH₄⁺ were below the guideline values, confirming the influence of chemical weathering on the groundwater chemistry. Based on the present findings, further studies that take into account more inorganic substances are required for NBLs and TVs determination in the area, thereby setting up a robust sustainable management plan for the regional groundwater resources.

Chemical and mineralogical variability of sediment in a Quaternary aquifer from Huaihe River Basin, China: Implications for groundwater arsenic source and its mobilization

Arsenic (As) is a conspicuous contaminant, and exposure to this element through contaminated drinking groundwater poses a significant challenge to public health. Geogenic groundwater arsenic is associated with sedimentary setting. This work concentrates on the investigation of lithology, elemental abundance and mineralogical compositions about the arsenic profile and its effect to the groundwater from Huaihe River Basin, China. There are 90 sediment samples from the borehole at the field monitoring sites were collected and analyzed. The results reveal that sedimentary concentrations of As, Fe, Mn, S, Al, N, organic carbon and mineralogical compositions vary across the Quaternary aquifer. Arsenic abundance of sediments is 10.63 ± 0.56 mg/kg, and peak As concentrations occur between 59.0 m and 64.8 m in fine particle sediments. The specific higher As concentrations in sedimentary aquifer are concordant with arsenic-rich groundwater around the investigated borehole. Fe, Mn, and Al depth profiles follow similar tendency to those of As. Sedimentary As concentrations are significantly correlated to Fe, Al, and Mn concentrations, but are not correlated to organic carbon and S concentrations. Arsenic probably exists in the form of non-crystalline colloids, and Fe, Al minerals are potential host minerals for arsenic. Under alkaline conditions, groundwater arsenic is released and enriched within the Quaternary aquifer by reductive dissolution of As-hosting Fe and Al minerals.

Human Health Risk Assessment Is Associated with the Consumption of Metal-Contaminated Groundwater around the Marituba Landfill, Amazonia, Brazil

Groundwater is present in its purest form beneath the earth's surface. However, metal contamination is potentially a problem faced by many countries. For this reason, the present study aims to make an assessment of the risks associated with groundwater consumption around the Marituba landfill in an Amazon region. The present study was characterized as transversal with the use of primary data. The sampling occurred in a stratified random way, performed in two radii of action being the 1st radius of 2.5 km away from the landfill and the 2nd radius of 3.5 km away from the landfill to the neighborhoods. A total of 184 points were collected. In all communities the average daily dose (ADD) was higher than the reference oral dose (Rfd), for the metals As, Pb and Mn the risk quotient (HQ) was greater than 1 (one) in all neighborhoods, the concentration of Mn in the least exposed neighborhood was greater than 10 µg.L^-1, even at a distance of 3.5 km from the landfill. The average concentrations for As and Pb did not exceed the recommended, however, they were more significant for the Beira Rio neighborhood, respectively 1.47 µg.L^-1 and 1.9 µg.L^-1. And the average concentration for Cu was more significant for the Uriboca neighborhood 18.20 µg.L^-1, but within the recommended. The average of the general concentration of Heavy Metals Pollution Index (HPI) of the water consumed was 80.03, indicating that the water consumed by the population is contaminated by metals.

Hydrogeochemical Processes and Potential Exposure Risk of Arsenic-Rich Groundwater from Huaihe River Plain, China

Arsenic poses a danger to environmental health, and arsenic-rich groundwater is a key exposure risk for humans. The distribution, migration, and enrichment of arsenic in groundwater is an important environmental and public health problem. Currently, the Huaihe River Basin is identified as a region of arsenic-rich groundwater in China. This study aims to assess arsenic-rich groundwater potential pollution risk, analyze the hydrogeochemical processes, and trace the ion source based on an analysis of groundwater hydrogeochemical data. The results show that arsenic is the main inorganic chemical substances affecting the water quality in the study area, which presents a high exposure risk for public health. The arsenic concentration of groundwater was f 5.75 ± 5.42 μg/L, and 23% of the considered samples exceeded the drinking water standards of the World Health Organization. The groundwater in the study area underwent evaporation, halite dissolution, and ion exchange processes. The total alkalinity (HCO3−) of the arsenic-rich groundwater mainly ranged between 400–700 mg/L, and the chemical type was mainly of HCO3-Na. In an alkaline environment, the oxidative dissolution and reductive dissolution of arsenic bearing minerals might be the formation mechanism of arsenic-rich groundwater.

Arsenic-contaminated groundwater and its potential health risk: A case study in Long An and Tien Giang provinces of the Mekong Delta, Vietnam

The occurrence of arsenic (As) in groundwater (drilled well water) that were used for drinking, cooking, and personal hygiene and its risks to human health in Long An and Tien Giang provinces (Mekong delta, Vietnam) were evaluated in this study. The average As concentrations were 15.92 ± 11.4 μg/L (n = 24, Long An) and 4.95 ± 4.7 μg/L (n = 24, Tien Giang). The average concentrations of As in Long An had not reached the WHO and QCVN 01: 2009/BYT healthy drinking water standard (10 μg/L). When used as a source of water for drinking and daily activities, arsenic-contaminated groundwater may have a direct impact on human health. The risk assessment from groundwater established by the US Environmental Protection Agency (USEPA) was conducted. The risk assessment showed that the average cancer risk (CR) values were 8.68 × 10^-4 (adults) and 2.39 × 10^-3 (children) for Long An, and 2.70 × 10^-4 (adults) and 7.43 × 10^-4 (children) for Tien Giang. These results were significantly higher than the CR (1 × 10^-4) proposed by the USEPA. The adverse health effect was therefore specifically warned by the use of arsenic-contaminated groundwater. This research offers valuable knowledge for efficient water management approaches to guarantee local communities' health protection.

Source analysis and health risk assessment of groundwater pollution based on multivariate statistical techniques in Kashgar Delta Area, Xinjiang, China

In this study, 63 groundwater samples were collected in the Kashgar Delta Area in Xinjiang in 2016, and then, the samples were tested and the test results were analyzed. Multivariate statistical techniques were used to determine the sources of pollution, and the USEPA (United States Environmental Protection Agency) model was used to assess the long-term health risk of groundwater to adults and children in the study area. The concentrations of groundwater chemical Na⁺, Cl^-, SO₄^2-, NH₄⁺-N, TDS, F^-, I^-, As, Fe, Mn, Pb, Hg, pH, TH, and COD_Mn, which exceed the permissible level in the study based on groundwater quality index and possibly pose a potential threat to the health of the residents in the area, which are mainly influenced by geological conditions. The source of the pollutants is the dissolution of minerals in the aquifer medium, which is greatly affected by the high-salinity groundwater environment, pH conditions, redox conditions, and evaporation and concentration effect. The values of the noncarcinogenic health risk index HQ_n follow the descending order of Cl^- > F^- > As > Fe > Mn > Pb > Hg > NH₄⁺-N; There are eight nonarcinogens and one carcinogen in groundwater of which Cl^- is the dominant noncarcinogenic factor, while As is the main carcinogenic pollutant in the study area. The health risk ratio results show that Cl^- and As are the main pollutants that pose the greatest threat to both adults' and children's health, and they should be considered as the primary indicators for health risk management and control.

Appraisal of vulnerable zones of non-cancer-causing health risks associated with exposure of nitrate and fluoride in groundwater from a rural part of India

The present investigation carried out from a rural part of Nalgonda district, Telangana, India was to know the general groundwater quality and also to measure the vulnerable zones of non-cancer-causing health risks with respect to infants, children, and adults due to the consumption of nitrate and fluoride contaminated groundwater. Groundwater samples were collected from the study area and analyzed for the major physicochemical parameters. Nitrate and fluoride contents ranged from 2 to 700 mg/L and 0.3 to 4.7 mg/L, in which 59.09% and 31.82% of the groundwater samples exceed the safe drinking water limits of 45 mg/L and 1.5 mg/L, which spread over an area of 77.59% and 25.41%, respectively. Domestic wastes, septic tank spillages, animal wastes, and nitrate composts are the prime sources of nitrate, while the fluoride-bearing minerals and phosphate fertilizers are the main sources of fluoride in the aquifer regime. Individual non-cancer-causing health index obviously suggested the nitrate as the higher health risk than fluoride. The total non-cancer-causing health index was observed to be more than the acceptable limit of 1.0 in 95.5% of the total groundwater samples concerning infants, children, and adults. The vulnerable intensity of this index appeared to be higher in infants than in children and adults due to the differences in their body weights. The spatial coverage area of very health risk is more in infants (37.45%) than that of children (36.78%) and adults (30.34%). Thus, the present study suggested suitable measures for the improvement of groundwater quality and consequently the health conditions of the locals.

Assessment of the water quality of groundwater in Bohai Rim and the controlling factors-a case study of northern Shandong Peninsula, north China

This study collected 184 groundwater (GW) samples from 92 wells during the dry and wet seasons, respectively to understand the hydrochemical characteristics, water quality, and risk of GW nitrate (NO₃^-) to human health in northern Shandong Peninsula (NSP), China. The results showed that GW in the NSP is weakly alkaline and classified as hard fresh water. The mean concentration of NO₃^- in GW exceeded 100 mg·L^-1, total hardness exceeded 450 mg·L^-1, and total dissolved solids (TDS) was less than 1000 mg·L^-1. A Piper diagram showed that the water chemistry of GW in the NSP was mainly of the SO₄·Cl-Ca·Mg type. A Gibbs diagram and ion ratio analysis indicated that the weathering of silicate rocks and agricultural production were the dominant factors affecting the hydrochemical characteristics of GW in the NSP, with cation exchange, dissolution of salt rock, and weathering of carbonate rock also making contributions. Na⁺ and Cl^- in GW are significantly affected by seawater aerosols in coastal areas. During the wet season, the hydrodynamic conditions of the aquifer are improved, agricultural activities are strengthened, and GW becomes generally homogenized. The water quality index classified the GW quality of the NSP as mainly of medium quality. There was a relatively consistent spatial distribution of water quality during different periods. Water samples of poor water quality were mainly distributed in the lower reaches of the Huangshui River. In addition, total hardness and NO₃^- concentrations were the main variables affecting the quality of GW in the NSP. The assessment of the risk NO₃^- in GW in the NSP to human health through the ingestion of drinking water demonstrated a significant risk (infants > children > adults). These results indicate the need for local management measures to reduce the potential health risks of GW quality in the NSP.

Hydrogeochemistry and health hazards of fluoride-enriched groundwater in the Tarim Basin, China

Fluoride (F^-) enrichment reduces the availability of groundwater resources in the arid region, and it is thus important to investigate the hydrogeochemistry and health hazards of fluoride-enriched groundwater. Seventy-two groundwater samples (20 unconfined samples from the piedmont plain, 22 unconfined samples and 30 shallow confined samples from the alluvial plain) were collected in the Tarim Basin of China to illustrate the geochemical processes driving the F^- enrichment and the incidence of dental fluorosis. The patterns of average ions contents in groundwater are Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and SO₄^2- > Cl^- > HCO₃^- > NO₃^- > F^-. The highest F^- concentration (average 2.16 mg/L) is observed in unconfined groundwater in the alluvial plain, while the lowest (average 0.63 mg/L) is recorded in unconfined groundwater in the piedmont plain. Approximately 5.0% of unconfined groundwater in the piedmont plain, 90.9% of unconfined groundwater and 33.3% of shallow confined groundwater in the alluvial plain contain F^- concentrations exceeding 1.0 mg/L (Chinese drinking water standard). Mineral dissolution, cation exchange, and evaporation play a significant role in the formation of solutes in groundwater. High-F^- groundwater is mostly associated with SO₄·Cl-Na·Ca, SO₄·Cl-Na·Mg, and SO₄·Cl-Na types water. Thermodynamic simulations reveal that the dissolution of F-bearing minerals (e.g., fluorite) significantly controls the F^- contents in groundwater. High concentrations of F^- are closely related to high HCO₃^-, high Na⁺, high salinity, cation exchange, and evaporation. This demonstrates that high F^- concentrations are caused by the increase in fluorite solubility due to high ionic strength, Ca²⁺ consumption and the desorption of F^- from solid surfaces under alkaline conditions. Mixing with the upper unconfined groundwater plays a vital role in the enrichment of F^- in shallow confined groundwater in the alluvial plain. The health risk assessment based on Dean's classification indicates that the percentage prevalence of fluorosis for boys aged 6 to 18 is 15.5% for Yecheng (YC), 18.4% for Zepu (ZP), 33.3% for Shache (SC), 29.8% for Maigaiti (MG), and 44.9% for Bachu (BC), while that for girls of the same age is 14.3% for YC, 24.3% for ZP, 42.2% for SC, 41.4% for MG, and 45.3% for BC. For male and female adults aged between 19 and 68, the percentage prevalence of fluorosis is: YC (11.5%, 12.0%), ZP (18.3%, 20.0%), SC (35.4%, 35.0%), MG (32.5%, 39.7%), and BC (42.4%, 44.3%). It is obvious that younger generation, especially girls, suffers from more severe dental fluorosis. This study has implications for the effective management of high-F^- groundwater in arid regions.

Evaluation of Groundwater Using an Integrated Approach of Entropy Weight and Stochastic Simulation: A Case Study in East Region of Beijing

Groundwater is an important source of water in Beijing. Hydrochemical composition and water quality are the key factors to determine the availability of groundwater. Therefore, an improved integrated weight water quality index approach (IWQI) combining the entropy weight method and the stochastic simulation method is proposed. Through systematic investigation of groundwater chemical composition in different periods, using a hydrogeochemical diagram, multivariate statistics and spatial interpolation analysis, the spatial evolution characteristics and genetic mechanism of groundwater chemistry are discussed. The results show that the groundwater in the study area is weakly alkaline and low mineralized water. The south part of the study area showed higher concentrations of total dissolved solids, total hardness and NO3--N in the dry season and wet season, and the main hydrochemical types are HCO3--Ca and HCO3--Ca-Mg. The natural source mechanism of the groundwater chemical components in Chaoyang District includes rock weathering, dissolution and cation exchange, while the human-made sources are mainly residents and industrial activities. Improved IWQI evaluation results indicate that water quality decreases from southwest to northeast along groundwater flow path. The water quality index (WQI) method cannot reflect the trend of groundwater. Sensitivity analysis indicated that the improved IWQI method could describe the overall water quality reliably, accurately and stably.

Deriving Natural Background Levels of Arsenic at the Meso-Scale Using Site-Specific Datasets: An Unorthodox Method

Arsenic is found in groundwater above regulatory limits in many countries and its origin is often from natural sources, making the definition of Natural Background Levels (NBLs) crucial. NBL is commonly assessed based on either dedicated small-scale monitoring campaigns or large-scale national/regional groundwater monitoring networks that may not grab local-scale heterogeneities. An alternative method is represented by site-specific monitoring networks in contaminated/polluted sites under remediation. As a main drawback, groundwater quality at these sites is affected by human activities. This paper explores the potential for groundwater data from an assemblage of site-specific datasets of contaminated/polluted sites to define NBLs of arsenic (As) at the meso-scale (order of 1000 km2). Common procedures for the assessment of human influence cannot be applied to this type of dataset due to limited data homogeneity. Thus, an “unorthodox” method is applied involving the definition of a consistent working dataset followed by a statistical identification and critical analysis of the outliers. The study was conducted in a highly anthropized area (Ferrara, N Italy), where As concentrations often exceed national threshold limits in a shallow aquifer. The results show that site-specific datasets, if properly pre-treated, are an effective alternative for the derivation of NBLs when regional monitoring networks fail to catch local-scale variability.

Occurrence of Heavy Metals in Groundwater Along the Lithological Interface of K/T Boundary, Peninsular India: A Special Focus on Source, Geochemical Mobility and Health Risk

Evaluation of the hydrogeochemical processes governing the heavy metal distribution and the associated health risk is important in managing and protecting the health of freshwater resources. This study mainly focused on the health impacts due to the heavy metals pollution in a known Cretaceous-Tertiary (K/T) contact region (Tiruchinopoly, Tamilnadu) of peninsular India, using various pollution indices, statistical, and geochemical analyses. A total of 63 samples were collected from the hard rock aquifers and sedimentary formations during southwest monsoon and analysed for heavy metals, such as Li, Be, Al, Rb, Sr, Cs, Ba, pb, Mn, Fe, Cr, Zn, Ga, Cu, As, Ni, and Co. Ba was the dominant element that ranged from 441 to 42,638 μg/l in hard rock aquifers, whereas Zn was the major element in sedimentary formations, with concentrations that ranged from 44 to 118,281 μg/l. The concentrations of Fe, Ni, Cr, Al, Cr, and Ni fell above the permissible limit in both of the formations. However, the calculated heavy metal evaluation index (HEI), heavy metal pollution index (HPI), and the degree of contamination (C_d) parameters were higher in the sedimentary formation along the contact zone of the K/T boundary. Excessive health risks from consumption of contaminated groundwater were mostly confined to populations in the northern and southwestern regions of the study area. Carcinogenic risk assessment suggests that there are elevated risks of cancer due to prolonged consumption of untreated groundwater. Ba, Sr, and Zn were found to be geochemically highly mobile due to the partitioning between the rock matrix and groundwater, aided by the formation of soluble carbonato-complexes. Factor analysis indicates that the metals are mainly derived from the host rocks and anthropogenic inputs are relatively insignificant. Overall, this study indicated that groundwater in K/T contact zones is vulnerable to contamination because of the favorable geochemical factors. Long-term monitoring of such contact zones is required to avert the potential health hazards associated with consumption of the contaminated groundwater.

Arsenic intoxication: general aspects and chelating agents

Arsenic (As) is widely used in the modern industry, especially in the production of pesticides, herbicides, wood preservatives, and semiconductors. The sources of As such as contaminated water, air, soil, but also food, can cause serious human diseases. The complex mechanism of As toxicity in the human body is associated with the generation of free radicals and the induction of oxidative damage in the cell. One effective strategy in reducing the toxic effects of As is the usage of chelating agents, which provide the formation of inert chelator–metal complexes with their further excretion from the body. This review discusses different aspects of the use of metal chelators, alone or in combination, in the treatment of As poisoning. Consideration is given to the therapeutic effect of thiol chelators such as meso-2,3-dimercaptosuccinic acid, sodium 2,3-dimercapto-1-propanesulfonate, 2,3-dimercaptopropanol, penicillamine, ethylenediaminetetraacetic acid, and other recent agents against As toxicity. The review also considers the possible role of flavonoids, trace elements, and herbal drugs as promising natural chelating and detoxifying agents.