Arsenic Concentrations In Groundwater Research Articles

Potential health risk assessment related to arsenic pollution and hydrogeochemistry of groundwaters in Akşehir and surroundings (Konya/Turkey)

Abstract Groundwater is an important water resource used for drinking, domestic and agricultural activities in Akşehir and surroundings. However, intensive agricultural and human activities in the region adversely affect groundwater quality. In this study, 31 water samples were collected from wells. According to the Piper diagram, groundwater in the study area was in the Ca–Mg–HCO3 and Ca–HCO3 water facies. As a result, it is not appropriate to use groundwater as drinking water in the study area in terms of trace elements and pollutant analysis results of water samples compared to limit values determined by WHO and ITHASY drinking water guidelines. The arsenic concentration in groundwater was studied in detail. The origin and concentration of arsenic in groundwater is associated with agricultural activities and pesticides in the region. Accordingly, a health risk assessment was carried out for the use of groundwater in the study area as drinking water. The results for all samples analyzed indicate that the groundwater concerned was not suitable for drinking purposes because of arsenic concentrations which exceeded maximum acceptable levels.

Analysis of Arsenic Content in Groundwater over the Years of Coastal Belt at Purba Medinipur in West Bengal

Analysis of Arsenic Content in Groundwater over the Years of Coastal Belt at Purba Medinipur in West Bengal

Spatio-temporal groundwater arsenic distribution in Central Mexico: implications in accumulation of arsenic in barley (Hordeum vulgare L.) agrosystem.

In the present work, a spatio-temporal study of arsenic (As) concentration in groundwater and its impact in barley uptake is presented. The impact of As on barley is studied through the determination of its bioaccumulation in the soil-plant system, As uptake, as well as a correlation between As concentration in water and its temperature in the groundwater. For the groundwater, spatial and temporal variability of As concentration in central Mexico was determined through a geostatistical analysis using ordinary kriging. The results show that the variability of As in the ground water is correlated with its temperature (R2 > 0.83). The As accumulation in the structures of plant follows the order root > leaf > ear in concentration. The bioaccumulation factor BAFT suggests that As is mobilized to the aerial parts of the barely for both As concentrations used in the irrigation water. However, for As concentration lower than 25 μg L-1, the BAFT is lower than 0.57, suggesting that the amount of As in root is the same as that contained in the aerial parts; whereas, for higher As concentrations (from 170 to 250 μg L-1), the BAFT is around 0.92, indicating that the As is mainly contained in root. The spatial distribution of As concentration trend in groundwaters along the time is the same, which means high As concentration areas remain in the same groundwaters and these areas are presenting the highest water temperature. These results shall contribute to understand the bioaccumulation of As in barley and the As spatial variability in central Mexico.

Arsenic in US correctional facility drinking water, 2006-2011

Background: Very little is known about the quality of drinking water in US correctional facilities (e.g. detention centers, prisons, jails, etc.), which disproportionately detain people of color. The current Environmental Protection Agency’s maximum contaminant level (MCL) for arsenic in public drinking water is 10 µg/L. We estimated drinking water arsenic concentrations in US correctional facilities to determine if incarcerated persons remain at risk for chronic, elevated water arsenic exposure relative to the non-incarcerated US population.Methods: We obtained 230,158 arsenic monitoring records for 37,098 community water systems (CWSs) from the Environmental Protection Agency’s Third Six Year Review of Contaminant Occurrence dataset (covering 2006-2011). We compared six-year average arsenic concentrations in all CWSs versus CWSs exclusively serving correctional facilities. We separately evaluated the Southwestern US (where groundwater arsenic concentrations are relatively high) versus non-Southwestern US.Results: Average six-year water arsenic concentrations were higher for CWSs exclusively serving correctional facilities in the Southwest (6.41 µg/L, 95% CI 3.48, 9.34) compared to all other Southwestern CWSs (3.11 µg/L, 95% CI 2.97, 3.24) and to other CWSs across the rest of the US (1.39 µg/L, 95% CI 1.35, 1.42). Compared to other US CWSs and to other Southwestern CWSs, correctional facility CWSs in the Southwest were more likely to report six-year arsenic averages exceeding 10 µg/L (1.6%, 5.8%, and 26.1% of systems, respectively).Conclusions: CWSs exclusively serving correctional facilities in the Southwestern US reported average water arsenic concentrations twice as high as those reported by all other CWSs in the Southwest, and more than a quarter reported six-year averages exceeding the EPA’s regulatory MCL. Strict enforcement of the EPA’s drinking water regulations and a comprehensive review of other drinking water contaminants in CWSs serving correctional facilities is necessary to protect the health and human rights of all incarcerated persons in the US.

Arsenic in Private Well Water and Birth Outcomes in the United States

Background/Aim: Prenatal exposure to drinking water with arsenic concentrations >50 μg/L has been associated with adverse birth outcomes. However, evidence is sparse at concentrations ≤50 μg/L. As a collaborative effort by public health experts and geologists, we used machine learning techniques to characterize arsenic concentrations in private wells, which are unregulated for contamination, and evaluated associations with birth outcomes throughout the conterminous U.S. Methods: Groundwater arsenic concentrations from ~20,000 private wells were used to develop several machine learning models, including random forest classification (RFC). Probabilistic model predictions, along with private well usage data, were linked by county to all certificates of live birth from 2016 (n=3.4 million). Mixed-effects models were fit to term birthweight and gestational age, adjusting for potential confounders and incorporating random intercepts for spatial clustering. As a sensitivity analysis to account for uncertainty in machine learning predictions, mother-infant pairs were randomly assigned to discrete private well arsenic categories (≤5, >5 to ≤10, or >10 µg/L) based on residential county. This process was repeated 10 times with estimates combined using Rubin’s rules. Results: We generally observed non-significant inverse associations with term birthweight. For instance, in sensitivity analyses of RFC predictions, we found that relative to mothers expected to have private well arsenic concentrations ≤5 μg/L, mothers assigned concentrations >5-≤10 μg/L gave birth to infants that weighed 1.6 (95% CI: -9.9, 6.6) grams less whereas those assigned to >10 μg/L gave birth to infants that weighed 2.4 (95% CI: -9.9, 5.1) grams less. Associations with gestational age were null. Conclusion: In this large nation-wide study, we did not detect a significant association of the modeled spatial distribution of arsenic in private wells with adverse birth outcomes. Measurement error stemming from a lack of individual-level information on primary water source and consumption levels likely obscured the true associations.

The groundwater monitoring system in Tuscany according to the EU Directive 2000/60 and the groundwater As contamination in the Versilia coastal plain

The EU Water Framework Directive 2000/60/EC commits European Union Member States to achieve good qualitative and quantitative status for all water bodies. Its application requires periodic monitoring of selected water bodies. Concerning groundwater bodies, the Tuscany Region selected monitoring wells for periodic sampling and performing chemical analyses. Results of these analyses are used to assess the qualitative status according to the EU Directive. In some cases, this groundwater monitoring can highlight some water pollution, hence activating more detailed investigations. In this work, we present the case of high arsenic concentrations in groundwater, reaching about 1000 μg/L, from domestic wells located in southern Versilia (Tuscany, Italy), close by the Baccatoio stream which receives acidic waters from a former mining site. Initially, the arsenic has been related to acid mine drainage from the nearby sites in the Baccatoio Valley. As-rich pyrite weathering was supposed to be the primary source for As in groundwater despite the Baccatoio stream is As-free. Although the evaluation of the amount of pyrite in sediments needs further investigations, alternative hypothesis were formulated. The highest As concentration is often accompained by high amounts of iron and ammonium ions reflecting reducing environments. This suggests the occurrence of secondary As-sources such as ferric oxyhydroxide and organic matter, likely in peat layers, undergoing reductive dissolution. The aim of this work is to carry out a preliminary assessment of the origin of the As contamination in groundwater of the Versilia coastal plain.

Geochemical characteristics of arsenic in groundwater during riverbank filtration: a case study of Liao River, Northeast China

Abstract Affected by groundwater exploitation in the riverside, the infiltration of river water to recharge groundwater will cause changes in the groundwater environment, which has an important impact on the geochemical behavior of arsenic in groundwater. In this study, the groundwater environment zones in the process of river water infiltration were divided, and the arsenic content in groundwater in the study area had a good correlation with the environment zones. In the weak oxidation environment zone and the weak reductive environment zone, as the distance from the riverbank increased, the arsenic content gradually increased. In the reduction environment zone, there was a decreasing trend in arsenic content in groundwater. The arsenic content in groundwater varied significantly with the seasons, and its dynamic characteristics were closely related to the water level. The arsenic content in groundwater decreased with the rise in groundwater level, and it responded obviously to the change of water level in the shallows. Overall, arsenic entered the groundwater from the solid phase through adsorption and desorption of exchangeable arsenic and exchangeable iron, and reductive dissolution of iron or manganese oxides bound iron in the medium during riverbank filtration.

Co-relation of Arsenic contamination with water table fluctuations and groundwater flow dynamics: A case study in a part of Bengal basin

ABSTRACT Temporal and seasonal variations of groundwater arsenic concentration are very significant for the exploration of its mobilisation mechanisms and to frame the policies of viable usage of arsenic-contaminated groundwater. Much less is known about the temporal and seasonal pattern of variation of arsenic contamination in shallow groundwater from the present study area (Karimpur blocks, Nadia district, West Bengal, India). So, to extend the understanding, the present study encompasses the steady monitoring of 15 wells of shallow depth from the study area for the period of 2014–2016. It has been observed that geochemical components were varying extensively during the period and the same trends follow for both Fe and As. During the period, the groundwater levels oscillated seasonally which promotes the reductive dissolution of Fe-oxides and/or oxy-hydroxides (As bearing minerals) which is aided by less dispersion of atmospheric oxygen into the shallow aquifers maintaining the reducing environment in the aquifers. The supply of dissolved organic matter into shallow aquifers was also evident by variation of Cl− ion concentration which may help to enhance arsenic mobilisation into shallow groundwater. Moreover, groundwater recharge from both regional rivers and perennial sources influences the evolution of anoxic conditions in the areas with low aquifers permeability consisting mainly of clayey and/or silty intercalations. Likewise, irrigation practices have been augmented to understand its role in arsenic mobilisation.

Geostatistical model of the spatial distribution of arsenic in groundwaters in Gujarat State, India

Geogenic arsenic contamination in groundwaters poses a severe health risk to hundreds of millions of people globally. Notwithstanding the particular risks to exposed populations in the Indian sub-continent, at the time of writing, there was a paucity of geostatistically based models of the spatial distribution of groundwater hazard in India. In this study, we used logistic regression models of secondary groundwater arsenic data with research-informed secondary soil, climate and topographic variables as principal predictors generate hazard and risk maps of groundwater arsenic at a resolution of 1 km across Gujarat State. By combining models based on different arsenic concentrations, we have generated a pseudo-contour map of groundwater arsenic concentrations, which indicates greater arsenic hazard (> 10 μg/L) in the northwest, northeast and south-east parts of Kachchh District as well as northwest and southwest Banas Kantha District. The total number of people living in areas in Gujarat with groundwater arsenic concentration exceeding 10 μg/L is estimated to be around 122,000, of which we estimate approximately 49,000 people consume groundwater exceeding 10 µg/L. Using simple previously published dose–response relationships, this is estimated to have given rise to 700 (prevalence) cases of skin cancer and around 10 cases of premature avoidable mortality/annum from internal (lung, liver, bladder) cancers—that latter value is on the order of just 0.001% of internal cancers in Gujarat, reflecting the relative low groundwater arsenic hazard in Gujarat State.

As3MT and GST Polymorphisms Influencing Arsenic Metabolism in Human Exposure to Drinking Groundwater.

The urinary arsenic metabolites may vary among individuals and the genetic factors have been reported to explain part of the variation. We assessed the influence of polymorphic variants of Arsenic-3-methyl-transferase and Glutathione-S-transferase on urinary arsenic metabolites. Twenty-two groundwater wells for human consumption from municipalities of Colombia were analyzed for assessed the exposure by lifetime average daily dose (LADD) (µg/kg bw/day). Surveys on 151 participants aged between 18 and 81 years old were applied to collect demographic information and other factors. In addition, genetic polymorphisms (GSTO2-rs156697, GSTP1-rs1695, As3MT-rs3740400, GSTT1 and GSTM1) were evaluated by real time and/or conventional PCR. Arsenic metabolites: AsIII, AsV, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were measured using HPLC-HG-AFS. The influence of polymorphic variants, LADD and other factors were tested using multivariate analyses. The median of total arsenic concentration in groundwater was of 33.3 μg/L and the median of LADD for the high exposure dose was 0.33 µg/kg bw/day. Univariate analyses among arsenic metabolites and genetic polymorphisms showed MMA concentrations higher in heterozygous and/or homozygous genotypes of As3MT compared to the wild-type genotype. Besides, DMA concentrations were lower in heterozygous and/or homozygous genotypes of GSTP1 compared to the wild-type genotype. Both DMA and MMA concentrations were higher in GSTM1-null genotypes compared to the active genotype. Multivariate analyses showed statistically significant association among interactions gene-gene and gene-covariates to modify the MMA and DMA excretion. Interactions between polymorphic variants As3MT*GSTM1 and GSTO2*GSTP1 could be potential modifiers of urinary excretion of arsenic and covariates as age, LADD, and alcohol consumption contribute to largely vary the arsenic individual metabolic capacity in exposed people.

Health risk assessment of co-occurrence of toxic fluoride and arsenic in groundwater of Dharmanagar region, North Tripura (India)

The present study assessed the co-occurrence of fluoride and arsenic in groundwater of Dharmanagar region (Tripura, India). Co-occurrence of the two toxicants was observed in 59% of the analyzed groundwater samples (n = 71), out of which concentrations of both the toxicants exceeded the World Health Organization drinking water standards in 30% samples. Significant positive correlation (r = 0.6) was observed between groundwater fluoride (<0.005–4.8 mg/l) and arsenic (<0.003–0.044 mg/l) contents. The range of cumulative estimated daily intakes (EDI) in the studied population was: 0.07–0.1 and 0.13–0.18 mg/kg-day for the Central Tendency Exposure (CTE) and the Reasonable Maximum Exposure (RME) scenarios, respectively. The EDI (fluoride) for the children of the study area was already found to reach the ‘Tolerable Upper Intake Level’ (UL) value (0.1 mg/kg-day), and the children are thus at high risk from developing dental fluorosis. Irrespective of the CTE or RME scenario, the hazard index of fluoride (HIFluoride = 1.2–3) and that of arsenic (HIArsenic = 1.5–5) were always found to be unsafe (HI > 1) in the studied population. The estimated Cumulative Noncancerous Lifetime Hazard Index for simultaneous fluoride and arsenic exposures was calculated to be prominently high (10 and 22 for the CTE and RME scenarios, respectively). The average urinary fluoride and arsenic contents of the studied population was observed to be correlated (r = 0.46 and 0.69) with the groundwater fluoride and arsenic concentrations, respectively. The observed content of urinary fluoride (mean = 3.1 ± 1.2 mg/l) of the studied population was determined to be 65–163% of their total fluoride intakes (1.9–7.2 mg/day). The obtained results are highly alarming and thus for reducing threats to human health, the government should immediately take necessary action for supplying safe drinking water for the residents.

Arsenic in US correctional facility drinking water, 2006–2011

BackgroundLittle is known about the quality of drinking water in US correctional facilities (e.g. detention centers, prisons, jails, etc.). Our objective was to determine if incarcerated persons are at risk for chronic, elevated arsenic exposure relative to the non-incarcerated US population, particularly in the Southwestern US where public water and groundwater arsenic concentrations are high compared to the rest of the US. MethodsWe analyzed 230,158 arsenic monitoring records from 37,086 community water systems (CWSs) from the Environmental Protection Agency's (EPA) Third Six Year Review of Contaminant Occurrence dataset (covering 2006–2011). We compared six-year average arsenic concentrations and the odds of exceeding the EPA's 10 μg/L maximum contaminant level (MCL) for CWSs exclusively serving correctional facilities versus all other CWSs in the Southwestern US, where groundwater arsenic concentrations are high. ResultsAverage six-year water arsenic concentrations were higher for Southwestern correctional facility CWSs (6.41 μg/L, 95% CI 3.48, 9.34) compared to all other Southwestern CWSs (3.11 μg/L, 95% CI 2.97, 3.24) and to other CWSs across the rest of the US (1.39 μg/L, 95% CI 1.35, 1.42). In the Southwest, 26.1% (N = 6) of correctional facility CWSs versus 5.8% (509) of other CWSs reported six-year arsenic averages exceeding 10 μg/L, corresponding to an odds ratio of 5.70 (95% confidence interval 2.24, 14.52). Correctional facility CWSs in the Southwest were also more likely to report six-year averages exceeding 5 μg/L (the MCL for New Jersey and New Hampshire, N = 8, odds ratio 2.77, 95% CI 1.17, 6.54). DiscussionPersons incarcerated in the Southwestern US were at disproportionate risk of elevated drinking water arsenic exposure and related disease from 2006 to 2011. Strict enforcement of EPA regulations and additional technical and financial support for CWSs serving correctional facilities in the Southwest is necessary to protect the health and human rights of incarcerated persons.

Data on arsenic contamination in groundwater of Rafsanjan plain, Iran.

This data article focuses on the arsenic in the groundwater of Rafsanjan plain in Kerman Province of Iran where the groundwater is being extensively used for drinking and irrigation of pistachio gardens. The measured arsenic concentrations range from 4 to 278 μg/L (with an average of 59 μg/L). About 85.3% of water samples have arsenic concentrations above 10 μg/L provided by the World Health Organization, WHO, guideline value. This data article provides also map showing the concentration of arsenic in groundwater of Rafsanjan area based on the situation of the sampling points in Rafsanjan region.

Molecular Evidence of Arsenic Mobility Linked to Biodegradable Organic Matter.

Molecular characteristics of natural organic matter (NOM) and their potential connections to arsenic enrichment processes remain poorly understood. Here, we examine dissolved organic matter (DOM) in groundwater and water-soluble organic matter (WSOM) in aquifer sediments being depth-matched with groundwater samples from a typical arid-semiarid basin (Hetao Basin, China) hosting high arsenic groundwater. We used Fourier transform ion cyclotron resonance mass spectrometry to determine molecular characteristics of DOM and WSOM and evaluate potential roles of biodegradable compounds in microbially mediated arsenic mobility at the molecular level. High-arsenic groundwater DOM was generally enriched in recalcitrant molecules (including lignins and aromatic structures). Although potential contribution of recalcitrant compounds to arsenic enrichment cannot be ruled out, preferential degradation of the labile molecules coupled with reduction of Fe(III) (oxyhydr)oxides seemed to dominate arsenic mobilization. Both the number and the intensity of biodegradable compounds (including aliphatic/proteins and carbohydrates) were higher in WSOM than those in DOM in depth-matched high-arsenic groundwater (arsenic >0.67 μmol/L or 50 μg/L). Groundwater arsenic concentration generally increased with the increase in the number and the intensity of unique biodegradable compounds (especially N-containing compounds) in WSOM at matched depths. Anoxic incubations of sediments and deionized water show that more arsenic and Fe(II) were released from aquifer sediments with greater numbers and intensities of consumed biodegradable compounds in WSOM (especially N-containing compounds), with a higher proportion of microbially derived compounds produced. These observations indicate that the biodegradation of aliphatic/proteins and carbohydrates (especially CHON formulas) in WSOM fueling the reductive dissolution of Fe(III) (oxyhydr)oxides predominantly promotes arsenic release from aquifer solids. Our unique data present a better understanding of arsenic mobilization shaped by microbial degradation of labile organic compounds in anoxic aquifers at the molecular level.

Microbial sulfate reduction facilitates seasonal variation of arsenic concentration in groundwater of Jianghan Plain, Central China

Bacterial sulfate reduction (BSR) plays a vital but complex role in regulating groundwater arsenic concentration. A quarterly hydro-biogeochemical investigation was conducted to clarify how BSR participated in arsenic dynamics in the geogenic As-contaminated alluvial aquifers of the Jianghan Plain, central Yangtze River Basin. Anthropogenic input of sulfate was identified in the transitional season with higher Cl concentrations and Cl/Br molar ratios compared to the monsoon season. Seasonal increase of S(-II) and Fe(II) concentrations in monsoon season suggests the co-occurrence of iron and sulfate reduction. Quantitative analysis of dsrB gene abundance revealed the corresponding variations between dsrB gene abundance (up to 1.2 × 107 copies L−1) and Fe(II) in groundwater. High-throughput sequencing of the dsrB gene identified a considerable proportion of sequences in the sulfate-reducing bacterial community was affiliated with Desulfobulbus (22.7 ± 20.8%) and Desulfocapsa (11.5 ± 11.9%). Moreover, the relative abundance of Desulfocapsa increased with the Fe(II) in the groundwater (R = 0.78, P < 0.01). These results suggest that microbially-mediated sulfate reduction facilitated the abiotic reduction of As-bearing Fe-oxides in the monsoon season after anthropogenic input of sulfate in the transitional season under oscillating redox conditions in the groundwater systems. The present research provides new insights into the critical role of BSR in the seasonal redox cycling of iron and variation of As in the aquifer systems, which are not only applicable in the central Yangtze River basin, but also to other similar As-rich alluvial aquifers worldwide.

The controlling of paleo-riverbed migration on Arsenic mobilization in groundwater in the Red River Delta, Vietnam

In the Red River Delta, the concentrations of Arsenic in groundwater of alluvial dominated systems are very high, exceeding the WHO’s permissible. The correlation between the Arsenic concentrations in groundwater and the age of Holocene sediment as a key controlling groundwater Arsenic concentration in the Red River delta has been investigated. The evolution of sediments in the Holocene is closely related to paleo-riverbed migration in the past. A combination of methods is implemented including remote sensing, multi-electrode profiling (MEP), gamma-logging, drilling, soil sample and groundwater modeling. The resul has identified the shape, sediment compositions and location of the six paleo-riverbed periods. The age of the paleo-riverbed is determined by drilling, soil sampling and optically stimulated luminescence (OSL) in the laboratory. The oldest sediments is 5.9±0.4 ka BP in Phung Thuong near the mountain, the youngest one is from 0.4÷0.6 ka BP in H-transect near the Red River and the rest of the other is around 3.5 ka BP. The modeling results by using MODFLOW and MT3D show that the dynamics of paleo-riverbeds controlling Arsenic mobilization in groundwater in the Red River Delta. When the river moved to another position, the current river position at that time was filled with younger sediments and became paleo-riverbed formation with reducing conditions, Arsenic content which was adsorbed in the previous stage then released into groundwater. Therefore, Arsenic concentration in groundwater of young Holocene sediments is higher than in older ones which elucidates that paleo-riverbed migration controls on Arsenic mobilization in groundwater in the study area.

The controlling of paleo-riverbed migration on Arsenic mobilization in groundwater in the Red River Delta, Vietnam

In the Red River Delta, the concentrations of Arsenic in groundwater of alluvial dominated systems are very high, exceeding the WHO’s permissible. The correlation between the Arsenic concentrations in groundwater and the age of Holocene sediment as a key controlling groundwater Arsenic concentration in the Red River delta has been investigated. The evolution of sediments in the Holocene is closely related to paleo-riverbed migration in the past. A combination of methods is implemented including remote sensing, multi-electrode profiling (MEP), gamma-logging, drilling, soil sample and groundwater modeling. The resul has identified the shape, sediment compositions and location of the six paleo-riverbed periods. The age of the paleo-riverbed is determined by drilling, soil sampling and optically stimulated luminescence (OSL) in the laboratory. The oldest sediments is 5.9±0.4 ka BP in Phung Thuong near the mountain, the youngest one is from 0.4÷0.6 ka BP in H-transect near the Red River and the rest of the other is around 3.5 ka BP. The modeling results by using MODFLOW and MT3D show that the dynamics of paleo-riverbeds controlling Arsenic mobilization in groundwater in the Red River Delta. When the river moved to another position, the current river position at that time was filled with younger sediments and became paleo-riverbed formation with reducing conditions, Arsenic content which was adsorbed in the previous stage then released into groundwater. Therefore, Arsenic concentration in groundwater of young Holocene sediments is higher than in older ones which elucidates that paleo-riverbed migration controls on Arsenic mobilization in groundwater in the study area.

The migration dynamics and the speciation of arsenic in the Hetao area, Inner Mongolia.

Arsenic contamination of the groundwater in the Hetao area in Inner Mongolia, China, has been a serious problem since the 1980s. In this study, the behavioral mechanics of arsenic in soil in the Hetao area, in relation to arsenic concentrations in groundwater, were studied using elemental speciation analysis. It is for probing the possible mechanisms of correlation and interaction within water and soil of the area, which is little work on it not only in the Hetao area but also worldwide. Associated with our previous work on water in this area, soil samples were collected along transects through areas strongly affected by arsenic poisoning. Sequential extractions were used to determine the speciation in soil of arsenic and other elements (Cd, Cu, Mo, Pb, Sb, Sn, and Zn) which are with similar geochemical behaviors to arsenic in natural systems. The results show that the arsenic concentration in soil is correlated with arsenic concentration in groundwater. This implies that arsenic transformation as a main factor of the resident poisoning of the area could be related with groundwater and soil. These results suggest that arsenic poisoning in the Hetao area is related with water and soil. The tracers moving through water are retained in the shallow stratum including soil and persist in the water affected by the movement of arsenic through the shallow stratum and soil. Graphical abstract.

Temporal dynamics of arsenic uptake and distribution: food and water risks in the Bengal basin

Contaminated food chain is a serious contender for arsenic (As) uptake around the globe. In Nadia, West Bengal, we trace possible means of transfer of As from multiple sources reaching different trophic levels, and associated seasonal variability leading to chronic As uptake. This work considers possible sources-pathways of As transfer through food chain in rural community. Arsenic concentration in groundwater, soil, rice, and vegetable-samples collected detected in different harvest seasons of 2014 and 2016. Arsenic level in shallow groundwater samples ranged from 0.1 to 354 µg/L, with 75% of the sites above the prescribed limit by WHO (10 µg/L) during the boro harvest season. High soil As content (∼20.6 mg/kg), resulted in accumulation of As in food crops. A positive correlation in As conc. with increase over period in all sites indicating gradual As accumulation in topsoil. Unpolished rice samples showed high As content (∼1.75 mg/kg), polishing reduced 80% of As. Among vegetables, the plant family Poaceae with high irrigation requirements and Solanaceae retaining high moisture, have the highest levels of As. Contaminated animal fodder (Poaceae) and turf water for cattle are shown to contaminate milk (0.06 to 0.24 µg/L) and behoves strategies, practices to minimize As exposure.

Seasonal influences on groundwater arsenic concentrations in the irrigated region of the Cambodian Mekong Delta

Similar to many southern and southeast Asian regions, the mobilisation of arsenic (As) from sediments has driven a widespread contamination problem for groundwater resources in the Cambodian Mekong Delta. For the first time, the seasonal changes in As concentrations and potential links to groundwater pumping for irrigation in shallow aquifers of the Cambodian Mekong Delta are investigated. Using environmental tracers (δ18O, δ2H, 3H, major/trace ions and rare earth elements) the natural and pumping-induced changes in hydrogeological processes are identified. Three conceptual models are proposed: Model 1, where there is limited local recharge or low recharge rates (3H mean residence time > 60 years) and groundwater has a large range in As concentrations (0.2 to 393.8 μg/L). In this semi-confined aquifer, only one of the six groundwater sites has As concentrations that increase (by 10.9 μg/L) potentially due to groundwater pumping and resultant mixing with high-As and low (Pr/Sm)NASC groundwater. However, data on groundwater extraction volumes is required to verify the link with irrigation practices. Model 2, where groundwater is recharged by evaporated surface waters (fractionated δ18O and δ2H). There are moderate As concentrations (64.1–106.1 μg/L) but no significant seasonal changes even though the recharging waters have relatively greater organic carbon contents during the dry season (reduced Ce/Ce*anomaly). Finally model 3, where groundwater is significantly recharged by wet season rainfall (~50% from δ18O data). There is a minor increase in As concentrations with recharge (by 6. μg/L). These combined results highlight an aquifer system in the irrigated region of the Cambodian Mekong Delta where As concentrations are largely impacted by natural rather than irrigation processes. Seasonal-scale recharge processes control As processes where the aquifer is not confined by shallow clay layers, and where the aquifer is semi-confined As concentrations largely reflect longer-term natural processes.