Search

Special attention has been paid in recent years to the social and environmental implications of municipal solid waste. There are potential social and environmental issues associated with storing any waste in landfill. Soil, groundwater, and surface water contamination are issues related to landfill and the migration of contaminants by leaching to adjacent areas. The current research attempts to simulate the penetration of landfill contaminants through groundwater leaching, using PART modeling approaches. Multiple social factors, taken from five years of data from 20 counties and cities in Taiwan were used as predictors of groundwater arsenic content. The results indicate that the proposed model attains a precision rate of 87%. The findings suggest that county and city demographics and the volume of waste removed are two major factors in determining the arsenic content of groundwater. The proposed predictive model can be adopted by agencies as an effective early warning tool for groundwater arsenic levels. [ABSTRACT FROM AUTHOR]

Arsenic, a known carcinogen, naturally occurs in the groundwater in large parts of West Bengal, a state in eastern India. Communities that depend on groundwater face twice the lifetime mortality risk for cancers, cardiovascular diseases, and developmental disorders. This study, focused on arsenic-affected communities in the state of West Bengal, offers an initial exploration of how local stakeholders construct groundwater arsenic as a health problem. Arsenic remediation interventions involve a host of international, regional, and local stakeholders (public health departments, government engineers, community health workers, consultants, hydrologists, etc.). How an environmental health problem is constructed has implications for who is considered responsible, what causes it, and pertinently, how/whether affected communities participate in addressing the problem. Drawing from a culture-centered approach, this fieldwork-based study offers three distinct yet related problem construction discourses, viz. social/political, technical and personal, in how the problem of arsenic is construed locally, and how such discourses are related to a particular conceptualization of community participation in environmental health. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arsenic content in shallow groundwater of the Yellow River alluvial fan plain exceeds the standard. A comprehensive understanding of the arsenic enrichment mode driven by the nitrogen cycle of shallow groundwater in the northern Henan Plain is essential for the sustainable use of groundwater resources and the health of residents. The main area of the North Henan plain is the Yellow River alluvial fan plain. The sedimentary environment in the northern Henan plain is complex, and is influenced by the Yellow River breach, diversion and oscillation, as well as alluvial diluvial in the mountainous area around the basin. The distribution, migration and release mechanism of As, NH+4 and NO-3 are quite different under different sedimentary environment conditions. The joint enrichment mechanism of the three is still unclear, which is worth further study. OBJECTIVES: To investigate the effect of nitrogen cycling on arsenic migration and enrichment in groundwater in the Northern Henan Plain. METHODS: 513 shallow groundwater samples were collected from the northern Henan Plain. Atomic fluorescence spectroscopy was used to determine the arsenic content, atomic absorption spectroscopy and ion chromatography, and other methods for major and trace element analysis. The correlation between nitrate, ammonia nitrogen and arsenic was investigated, and the influence of nitrogen cycle on the migration and enrichment of arsenic in groundwater was studied. RESULTS: The over-standard rate of arsenic concentration in shallow groundwater in the study area was 17.3%. The occurrence and transformation modes of nitrogen under different depositional environmental conditions were important driving factors for arsenic enrichment. A large amount of NO-3 was produced by nitrification in the groundwater of the alluvial fan in the piedmont alluvial fan, which had the average concentration of 9.3 mg/L and was the highest in the district. At the same time, the concentration of arsenic was the lowest in the district, with the average of 1.3μg/L. The good negative correlation between NO-3 and As concentration indicated that nitrification produced a large amount of NO-3, which was not conducive to the dissolution of arsenic-containing iron oxide. The depressions in front of the alluvial fan and the Yellow River crater fan with higher NH+4 content were the gathering places of high-arsenic groundwater. The average concentration of arsenic in groundwater from these two areas was 49.7μg/L and 18.9μg/L, respectively, and the exceeding rate reached 87.5% and 71.4%. The good positive correlation between arsenic content and NH+4 in groundwater indicated that the process of denitrification and dissimilative reduction of nitric acid to ammonium (DNRA) consumed NO-3 in groundwater and generated a large amount of NH+4, which promoted the reduction and dissolution of iron oxides that adsorbed arsenic, forming an environment rich in arsenic. CONCLUSIONS: The nitrogen cycle plays an important role in the migration and enrichment of arsenic. The migration and enrichment mode of arsenic driven by the nitrogen cycle provides a scientific basis for the treatment and supervision of groundwater with high arsenic content. [ABSTRACT FROM AUTHOR]

BACKGROUND: Arsenic pollution is a senous problem in shallow groundwater in the Hetao Basin, and has seriously affected the health of residents. The research on the distribution of high arsenic shallow groundwater in the Hetao Basin is limited by the sampling time and sample number. OBJECTIVES: To obtain a comprehensive understanding of the risk distribution characteristics and important influencing factors of high arsenic groundwater in different seasons in the region. METHODS: Based on 506 shallow groundwater samples and 9 surface environmental parameters as prediction variables, a random forest model was established to evaluate the importance of prediction variables and the impact of important variables on high arsenic groundwater. Taking the climate factors as the dynamic prediction variables, the probability distribution of high arsenic groundwater in different seasons was identified and thematic maps of risk areas were made. RESULTS: The results showed that the arsenic content of 506 groundwater samples ranged from 0. 05 to 916.7 µg/L with an overshoot rate ( > 10 µg/L) of 50% . Groundwater arsenic risk areas were mainly distributed in the depositional center of the Hetao Basin, but the area of groundwater arsenic risk areas decreased by 1907km² in winter, accounting for 14.14% of the total area. Precipitation and drought index, influence of drainage and irrigation channels, potential evapotranspiration and temperature were the most important indexes affecting the high arsenic groundwater in this area. CONCLUSIONS: In the Hetao Basin, climate variables ( precipitation and drought index) are significantly correlated with arsenic accumulation in the aquifer, which controls the seasonal variation of groundwater with high arsenic content in the depositional center of the Hetao Basin. [ABSTRACT FROM AUTHOR]

BACKGROUND: A typical irrigation area of the downstream Yellow River ( Henan) is an important agricultural planting area in the northern Henan Plain. The shallow water quality in this area is generally poor, which is often used for crop irrigation or livestock drinking, posing a risk to human health. Therefore, the study on the variation characteristics and mechanism of arsenic and fluorine content in groundwater in this area will help to improve the level of understanding of pollution in this area. OBJECTIVES: To investigate the spatial variation characteristics and mechanism of arsemc and fluorine concentration. METHODS: Based on 327 groups of shallow groundwater samples collected in 2010 and 2020 in the irrigated area, the distribution of arsenic and fluorine in the groundwater of the irrigated area was analyzed, and compared to the evolution characteristics of arsenic and fluorine in the shallow groundwater of the irrigated area in the last ten years. RESULTS: In 2020, the number of samples with high arsenic concentration (> 10 µg/L) and high fluorine concentration (> 1mg/L) in shallow groundwater accounted for 26.1% and 26.06%, respectively. The high - arsenic groundwater was distributed in the sedimentary environments with interbedding structure of sediment, such as the Taihang Mountain depression and the Yellow River alluvial plain, with strong reducibility, poor groundwater runoff and strong cation exchange, resulting in high concentration of Ca2+ in the environment. Arsenic concentration increased in 31.8% of water samples and decreased in 36.7% of water samples in the last ten years. The increase of arsenic content was caused by the dissolution and release of manganese oxide due to the enhanced reducibility of groundwater. The variation of water level caused by agricultural irrigation and water replacement in different areas during the last ten years was a potential factor of arsenic concentration change. The high - fluorine groundwater was mainly distributed along the Yellow River in Xinxiang and Puyang, Henan Province. The concentration of fluorine ion was affected by the dissolution of calcareous minerals such as fluorite in the sediments, which made the high - fluorine groundwater appear in the low - calcium environment. In the last ten years, the study area with decreased fluorine ion concentration accounted for 60.2%, whereas areas with increased fluorine ion concentration accounted for 32.1% . The overall change trend was good, but the fluorine ion concentration m the high fluorine area continued to increase. Changes in fluorine concentration were also affected by changes m Ca2+, with further increases ( decreases) as Ca2+ concentration decreased ( increased). Elevated fluorine m groundwater was distributed along the Yellow River, affected greatly by the Yellow River water supply. So, the groundwater flow condition was good and the cation exchange was weakened, reducing the Ca2+ content. At this time, the arsenic content in the groundwater was less affected by the environment, so the study area with fluorine increase showed an inverse relationship between arsenic and fluorine in terms of regional distribution and evolution. CONCLUSIONS: This study will provide support for rational utilization of groundwater in the study area. [ABSTRACT FROM AUTHOR]

Human biomarkers were used to evaluate the lead (Pb) and arsenic (As) exposure of local people who lived in an agricultural area with intense agrochemical usage and who consumed groundwater. Although the heavy metals/metalloids in the groundwater were at low concentrations, they could cause adverse effects due to a high daily water intake rate over the long term. Biomarkers (hair, fingernails and urine) were collected from 100 subjects along with the local shallow groundwater and tap water, which is the treated deep groundwater, and investigated for the concentrations of As and Pb. Shallow groundwater had an average pH of 5.21 ± 1.90, ranging from 3.77 to 8.34, with average concentrations of As and Pb of 1.311 µg/L and 6.882 µg/L, respectively. Tap water had an average pH of 5.24 ± 1.63, ranging from 3.86 to 8.89, with the average concentrations of As and Pb of 0.77 µg/L and 0.004 µg/L, respectively. The levels of both As and Pb in the hair, fingernails and urine of shallow groundwater-consuming residents were greater than those in the hair, fingernails and urine of tap water-consuming residents. Interestingly, the As level in urine showed a linear relationship with the As concentration in groundwater (R2 = 0.91). The average water consumption rate was approximately two-fold higher than the standard; thus, its consumption posed a health risk even at the low As and Pb levels in the groundwater. The hazard index (HI) ranged from 0.01 to 16.34 (average of 1.20 ± 2.50), which was higher than the acceptable level. Finally, the concomitant factors for As and Pb in the urine, hair and nails from both binary logistic regression and odds ratio (OR) analysis indicated that groundwater consumption was the major concomitant risk factor. This study suggested that direct consumption of this groundwater should be avoided and that the groundwater should be treated, especially before consumption. In conclusion, urine is suggested to be a biomarker of daily exposure to As and Pb, while for long-term exposure to these metals, fingernails are suggested as a better biomarker than hair. [ABSTRACT FROM AUTHOR]

Naturally occurring arsenic in groundwater affects millions of people worldwide. We created a global prediction map of groundwater arsenic exceeding 10 micrograms per liter using a random forest machine-learning model based on 11 geospatial environmental parameters and more than 50,000 aggregated data points of measured groundwater arsenic concentration. Our global prediction map includes known arsenic-affected areas and previously undocumented areas of concern. By combining the global arsenic prediction model with household groundwater-usage statistics, we estimate that 94 million to 220 million people are potentially exposed to high arsenic concentrations in groundwater, the vast majority (94%) being in Asia. Because groundwater is increasingly used to support growing populations and buffer against water scarcity due to changing climate, this work is important to raise awareness, identify areas for safe wells, and help prioritize testing. [ABSTRACT FROM AUTHOR]

Groundwater through hand-operated tubewell (a type of water well) tapping is the main source of drinking water in Bangladesh. This study investigated iron and manganese concentration in groundwater across Jashore district–one of the worst arsenic contaminated area in Bangladesh. One working tubewell that had been tested previously for arsenic and marked safe (green) was selected from each unions of the district. Results revealed that approximately 73% and 87% of groundwater samples exceeded the limits for iron and manganese in Bangladesh drinking water, respectively. Additionally, spatial distribution of iron and manganese indicate that only 5% of the total surface area of groundwater is covered by safe level of iron and manganese. Human health risk due to ingestion of iron and manganese through drinking water was evaluated using hazard quotients (HQ) for adults and children. The result of the health risk assessment revealed that the non-carcinogenic health risks due to ingestion of iron (HQ up to 1.446 for adults and 0.590 for children) and manganese (HQ up to 2.459 for adults and 1.004 for children) contaminated groundwater are much higher among adults than children. On the basis of occurrences, spatial distribution and health risk assessment results, the area can be categorized as a high-risk zone for iron and manganese-related problems and needs special attention in order to protect public health of local residents. [ABSTRACT FROM AUTHOR]

The influence of aquifer sediments provenance and geochemical processes on groundwater solute chemistry, including the fate of groundwater arsenic (As) in aquifers for three distinct tectono-morphic zones (north-western, northern, and southern [NW, N, and S] in the basin of Himalayan Mega Rivers, i.e., Brahmaputra river basin (BRB), and adjoining the Himalayas and Indo-Burmese ranges, have been delineated. The presence of fluvial re-worked quartz, feldspar, and mica along with orogeny-sourced ferromagnesian minerals contained aquifers sediments in the NW and N regions are hypothesized to be derived from the Himalayan system. The S-aquifers mineralogy differs from northern aquifers by a higher proportion of Fe/Mg aluminosilicates, phyllosilicates/clay minerals, derived from the Indo-Burmese ranges. The dissolved As distribution is highly variable among the different alluvial aquifers. The S-region is highly enriched in groundwater As (bdl to 5.53 μM or 415 μg/L, mean 1.77 μM) compared to NW and N regions (bdl to 1.8 μM or 134 μg/L, mean 0.28 μM [60% As-contaminated samples]; bdl to 2.45 μM or 184 μg/L, mean 0.68 μM [65% As-contaminated samples] respectively). More than 92% of groundwater samples in the S-region are enriched with As (>50 μg/L), which draws a distinct difference from the NW and N regions of BRB aquifers. Reaction-path models suggest intense chemical weathering of S-aquifer matrix due to the higher equilibrium (more stable) of secondary mineral phases with the solution (groundwater), as compared to NW and N regions. The present study proposes a model for the geological control and effect of weathering/water–sediment reaction on As-fate and mobilization mechanism in the groundwater system of the barely studied Brahmaputra river basin aquifers. Image 1 • Water-sediment interaction dominates groundwater evolution. • A model of arsenic (As) influx and mobilization in study area is proposed. • Geology is hypothesized to be a major influencing factor for hydrogeochemistry • Tectonics influence the sediment provenance for groundwater arsenic content. [ABSTRACT FROM AUTHOR]

Abstract Low-arsenic (As) groundwater from Pleistocene aquifers is vulnerable to future geogenic and allogenic arsenic pollution in South and Southeast Asia, threatening the millions who use it as a "safe source" of drinking and irrigation water. The abundance and chemical reactivity of iron and manganese oxides within these aquifer sediments control the occurrence and mobility of arsenic. In the present study, sediment samples varying in As, Fe, and Mn content were obtained from a Pleistocene aquifer in the Kandal Province of Cambodia. Laboratory and spectroscopic characterization of the sediment combined with groundwater analyses revealed that the availability and abundance of sedimentary As varied across a Pleistocene aquifer from the pore to field scales. Concentrations of sediment As (0.47–7 μg/g) correlated more strongly with Fe (R2 > 0.66) than with Mn (R2 > 0.35) concentrations in sediment well cuttings and tended to peak between 10 and 15 m. Chemical extractions and X-ray adsorption spectroscopy indicated the majority of As was strongly adsorbed to aquifer sediments or coprecipitated in oxides in the form of As(V) but that As(III) could be found in sediment microenvironments across the aquifer. Groundwater chemistry and Mn mineralogy indicated that the Pleistocene aquifer was suboxic, with average dissolved oxygen of 1.9 mg/L (±0.9 mg/L), redox potential of 0.155 V (±0.097 V), and abundant Mn(III/IV) oxide minerals. According to our results, allogenic As transport and geogenic As release will likely be dictated by localized geochemical processes that vary over a range of scales. Collectively, the specific Fe and Mn mineralogy and content within aquifers will ultimately govern As pollution potential, so understanding their multi-scale distributions and variability is essential for better predicting future risks to well-water quality in currently low-As aquifers. [ABSTRACT FROM AUTHOR]

High arsenic groundwater contamination causes serious health risks in many developing countries, particularly in India and Bangladesh. The arsenic fluxes in aquifers are primarily controlled by bacterial populations through biogeochemical cycle. In this present study, two gram-positive rod-shaped bacteria were isolated from shallow aquifers of Bhojpur district in Bihar during the early winter season, able to withstand arsenite (As3+) concentration upto 70 mM and 1000 mM of arsenate (As5+) concentration. They showed high resistance to heavy metals up to 30 mM and utilized some complex sugars along with different carbon sources. Growth at wide range of temperature, pH and salinity were observed. Both these isolates showed high efficiency in converting As3+ into less toxic concentrations of As5+ respectively from arsenic enriched culture media. Along with superior arsenic transformation and arsenic resistance abilities, the isolates showed a wide variety of metabolic capacity in terms of utilizing a variety of carbon sources under aerobic conditions, respectively. This study reports the potential As3+-oxidizing bacteria that can play an important role in subsurface arsenic transformation that will aid in designing future bioremediation strategy for the arsenic affected areas. [ABSTRACT FROM AUTHOR]

Inorganic arsenic species determination is important to measure health hazards and to interpret in the best possible way clinical signs within populations drinking exposed water. This study was performed on groundwater samples from northern Burkina Faso using a portable electroanalytical apparatus in order to assess the proportion of As (III) versus As (V) when analyzed on site and during conservation. Two different treatment methods of water samples were performed and analyzed for their ability to maintain the initial As species content. The samples conserved with HCl and EDTA in white non opaque bottles were subsequently analyzed at days 7 and 21 post sampling. The investigations showed that arsenic (V) species were the most predominant form in the twenty-one studied samples. In general, regardless of their treatment, arsenic (III) species were spontaneously converted into the arsenic (V) during conservation. The arsenic (III) form, however, was kept for three samples until day 7 and for two of them until day 21. [ABSTRACT FROM AUTHOR]

In this work, feasibility of electrocoagulation (EC) process with Al and Fe scrap anodes for treatment of groundwater contaminated with arsenic (As) was examined as a cheaper treatment alternative for affected remote communities. EC experiments were carried out in a batch packed-bed EC reactor and the effect of applied current (0.010–0.100 A), type of scrap electrode (Fe and Al), packed-bed density (0.1–0.4 kg/m³ for Fe and 0.02–0.08 kg/m³ for Al) and EC time were investigated. Optimum operating conditions to obtain maximum contaminant level (MCL) of 10 μg /L for total As (>93% removal) in groundwater samples were determined as 8 min and 0.05 A for Fe scrap anodes. Whereas for Al scrap anode, 30 min and 0.10 A were the optimums. The operating cost, energy and electrode consumptions at these optimums were calculated as 0.017 US $/m³, 0.070 kW h/m³ and 0.052 kg/m³ for Fe anodes and 0.181 US $/m³, 0.876 kW h/m³ and 0.067 kg/m³ for AL anodes respectively. The As removal slightly decreased with decrease in anode bed density. Moreover, Fe scrap anodes exhibited better As removal than the Al scrap anodes at all tested conditions. The scanning electron microscopy (SEM) of the electro-coagulated sludge revealed irregular and porous particles with amorphous structure. The Fourier-transform infrared spectroscopy (FTIR) showed bonding between Fe(III) - As(V), and As—O bond, confirming As removal by co-precipitation and adsorption, respectively in the EC process. [ABSTRACT FROM AUTHOR]

Abstract Contamination of groundwater with toxic arsenic (As) has become an emerging health and environmental problem around the world, which has seen significant attention amongst the scientists for development of new sorbents to remediate As-contaminated water. Here, we explored the arsenate (As(V)) and arsenite (As(III)) sorption to natural water melon rind (WMR), xanthated WMR and citric acid-modified WMR in aqueous solutions, and determined potential of the most potent sorbent for As removal in groundwater. Xanthated WMR (X-WMR) showed relatively higher As(V) and As(III) removal than the citric acid modified WMR (CA-WMR) and natural WMR. The maximum As(III) (99%) and As(V) (98%) removal was obtained at pH 8.2 and 4.6, respectively, by X-WMR at 4 mg L−1 initial As(V) and As(III) concentrations and sorbent dose of 1 g L−1. Langmuir isotherm model best fitted (R 2 of up to 0.96) the data both for As(III) and As(V) sorption to X-WMR. Sorption kinetics of As(V) and As(III) was well described (R 2 of up to 0.99) by the pseudo second-order model on surface of the X-WMR. Thermodynamic investigations revealed that As(V) and As(III) sorption was endothermic and spontaneous. The FTIR spectroscopy depicted the presence of different surface function groups (OH, COOH, S-bearing (C=S, S=O and S–S)) which were involved in As(V) and As(III) sequestration on the sorbents examined here. Significantly, X-WMR showed (up to 49%) greater As(III) and As(V) sorption than that of natural WMR. Our results demonstrated that X-WMR efficiently removed 94%–100% (n = 16) of As from As-contaminated drinking well water which possessed detectable concentrations of some anions (e.g., SO 4 , CO 3 , HCO 3). This study highlights that the X-WMR has potential to remove As, notably As(III), from solutions and drinking water, and might be utilized as a reactive medium for the treatment of As-contaminated water. Graphical abstract Unlabelled Image Highlights • Water melon rind (WMR) was tested for arsenic removal potential from water. • Xanthated WMR removed up to 99% of As(III)/As(V) in solutions. • Langmuir and pseudo second-order models provided the best fits for As(III) and As(V). • FTIR spectra showed arsenic sequestration with surface functional groups of sorbents. • Xanthated WMR successfully removed 94–100% arsenic from drinking well water. [ABSTRACT FROM AUTHOR]

Abstract The role of post harvesting procedures for producing parboiled rice grain using arsenic (As) contaminated groundwater in rural Bengal was investigated. Considerable high concentrations of As (mean: 186 μg/kg) were found in about 82% of parboiled rice grain samples compared to raw or non-parboiled rice grain samples (66 μg/kg in 75% samples) obtained from Deganga, a highly As affected zone located in West Bengal, India. This observation instigated to study the additional entry of As at various stages of parboiling. A maximum increase of 205% of As content in parboiled rice grain was observed. Significant increase in parboiled whole grain As concentration was dependent upon the large difference between As concentrations of the water and the raw whole grain used for parboiling. Arsenic concentrations of water samples collected at raw, half boiled and full boiled stages of parboiling increased, irrespective of their initial concentration due to reduction in final volume during parboiling process. Principle component analysis shows a positive correlation of As concentration of rice grain to that in the groundwater being used in post harvesting procedure. Moreover, partitioning studies of As in whole grain indicated higher accumulation of As content in individual rice grain than that in their respective husks implying higher risk of exposure on ingestion of these contaminated rice grains. It is therefore, suggested to employ novel methods such as rain water harvesting or surface water channelling to make As free water available for parboiling process to curtail the entry of additional As in parboiled rice. Graphical abstract Image 1 Highlights • Parboiled rice and its by-products accumulate arsenic (As) more than raw rice. • Parboiling with As contaminated water contributes As to parboiled rice grain. • Arsenic content in rice grain is comparatively higher than the outer husk. • Use of As free water during parboiling is vital to minimise additional As exposure. [ABSTRACT FROM AUTHOR]

Abstract As widely known, in several countries in South East Asia, arsenic concentrations in ground water extracted from Quaternary alluvial sediments frequently exceed the World Health Organization (WHO) drinking water guideline of 10 μg/L. The broadly accepted hypothesis states that reductive dissolution of Fe-bearing minerals releases As-oxyanions contained within these minerals. According to the results presented in this article, As and Fe concentrations in ground water in the lowlands (Terai) of Nepal are highly variable as a function of location and there is a de-coupling of As and Fe concentrations resulting in a loss of correlation between these two elements. The mean concentrations of As and of Fe in 35 wells were slightly higher in the post-monsoon than in the pre-monsoon season. Even though As is mainly associated with iron(hydr)oxides, a substantial portion of As and Fe can be retained by clay minerals (including micas). During pre-monsoon (dry season) clayey sediments are chemically weathered losing Na and K thus remaining relatively enriched in less mobile elements such as Fe and Al. As long as reducing conditions persist, As remains relatively mobile. This article includes a detailed discussion referring to the very weak correlation or decoupling between aqueous As and Fe in the ground water and addresses possible consequences for water treatment. It sheds light on the original reservoir of arsenic being incorporated and released from clay minerals as well as from iron(hydr)oxides. Highlights • Climatic variations influence arsenic and iron concentrations in contaminated ground water. • The concentration of arsenic in ground water is decoupled from iron. • Concentrations of As correlate positively with Li, B, Na, and Mo, and negatively with Ca and Mn. • In addition to Fe(hyr)oxides, clay minerals are carriers of arsenic. [ABSTRACT FROM AUTHOR]

High arsenic (As) groundwater has been found in Pliocene confined aquifers at depths from 100 to 300 m of the Guide basin, but little is known on the main hydrogeochemical processes leading to its elevated concentrations. Ninety-seven water samples and fifty-three sediment samples were collected for chemical and/or isotopic analysis. Concentrations of As in groundwater of confined aquifer range from 9.9 to 377 μg/L (average 109 μg/L), which generally show a sharply increasing trend along with NH 4 + , HCO 3 − , CO 3 2− and TOC along the inferred flow path, while NO 3 − , SO 4 2− /Cl − and redox potential (Eh) have decreasing trends. Results of sequential extraction show that As bound to amorphous and crystalline Fe oxide minerals are the main As forms, accounting for around 50% of total As in sediments. Reductive dissolution of As-bearing Fe(III) oxide minerals under reducing conditions in confined aquifers lead to the mobilization of As in groundwater. In addition, alkaline environment and high concentrations of HCO 3 − and CO 3 2− may make contributions to As enrichment in groundwater. High As groundwater in confined aquifer continuously flows out on the ground surface through tens of artesian wells, which may potentially contaminate low As groundwater in unconfined aquifer. Thus, further investigation is needed to evaluate long-term variations of water chemistry of low As groundwater and assess vulnerability of unconfined aquifer to As contamination. [ABSTRACT FROM AUTHOR]

To understand occurrence, distribution and source of arsenic, 175 groundwater samples from coastal aquifers of the Puducherry region were collected and analyzed for major ions and trace metals. The concentration of As in groundwater of study area ranges from not detectable — 28.88 μg/L during the post-monsoon and not detectable — 36.88 μg/L in the pre-monsoon. The desirable limit for As in groundwater is 10 μg/L as per World Health Organization and Bureau of Indian standard. About 13.64 and 11.50% of groundwater samples shows arsenic concentration higher than recommended limit. Hydrochemical facies which dominate during pre and post monsoon are Na-K-Cl-SO 4 , Ca-Cl and Ca-Mg-Cl-SO 4 type and Na-K-Cl-SO 4 , mixedCa-Na-HCO 3 , Ca-HCO 3 and mixed Ca-Mg-Cl type respectively. The Gibbs diagram suggested that rock-water interaction is major process controlling hydrochemistry of groundwater. From the Pourbaix diagram, it is inferred that H3AsO3 is the principal As species in groundwater. The PHREEQC modelling indicates supersaturation of ferric oxides and hydroxide mineral phases in aquifer system which on reductive dissolution releases arsenic into groundwater. Statistical analysis (Spearman Correlation and Principal Component Analysis) showed that reductive dissolution of As-bearing minerals and Fe-oxyhydroxides in the presence of organic matter is the major process contributing arsenic into groundwater. The relationship between As, K + and HCO − 3 indicates agricultural and competitive exchange process which is an additional contributor of arsenic in groundwater. The sources which act as a sink and responsible for the release of As into the groundwater are marine sediments enriched in As and Fe-bearing minerals and organic matter. [ABSTRACT FROM AUTHOR]

Groundwater arsenic contamination is a common environmental problem that threatens the health of over 100 million people globally. Apparent seasonal fluctuations in groundwater arsenic concentrations have been reported in various locations worldwide, including the Jianghan Plain, central China. This phenomenon has been attributed to shifts in redox conditions induced by seasonal incursions of surface water. However, it is not clear what processes during the incursion lead to changes in the redox conditions and what is the source of the organic carbon driving these processes. Therefore, we conducted a long-term investigation of stable carbon isotopic compositions in surface water and groundwater, as well as long-term monitoring of hydraulic gradients and geochemical compositions at the Jianghan Plain. Results indicated that a series of biogeochemical processes occurred during surface water incursion, including aerobic microbial respiration, nitrate and sulfate reduction. Groundwater arsenic was removed by adsorption on iron oxyhydroxides produced during oxidation of ferrous iron, resulting in dramatic decreases in arsenic concentrations during surface water recharge seasons. These processes were likely driven by organic carbon vertically transported from surface water and released from the surficial aquitard above 15 m. Groundwater pumping may accelerate the vertical infiltration of oxidizing recharge water and drive exogenous organic carbon to depth. Findings of this study advance the understandings of the mechanisms that cause temporal variations in groundwater As and the importance of exogenous organic carbon that may influence the temporal behavior of arsenic in groundwater. [ABSTRACT FROM AUTHOR]

Molecular and eco-physiological characterization of arsenic (As)-transforming and hydrocarbon-utilizing Achromobacter type strain KAs 3-5T has been investigated in order to gain an insight into As-geomicrobiology in the contaminated groundwater. The bacterium is isolated from As-rich groundwater of West Bengal, India. Comparative 16S rRNA gene sequence phylogenetic analysis confirmed that the strain KAs 3-5T is closely related to Achromobacter mucicolens LMG 26685T (99.17%) and Achromobacter animicus LMG 26690T (99.17%), thus affiliated to the genus Achromobacter. Strain KAs 3-5T is nonflagellated, mesophilic, facultative anaerobe, having a broad metabolic repertoire of using various sugars, sugar-/fatty acids, hydrocarbons as principal carbon substrates, and O2, NO3−, NO2−, and Fe3+ as terminal electron acceptors. Growth with hydrocarbons led to cellular aggregation and adherence of the cells to the hydrocarbon particles confirmed through electron microscopic observations. The strain KAs 3-5T showed high As resistance (MIC of 5 mM for As3+, 25 mM for As5+) and reductive transformation of As5+ under aerobic conditions while utilizing both sugars and hydrocarbons. Molecular taxonomy specified a high genomic GC content (65.5 mol %), ubiquinone 8 (UQ-8) as respiratory quinone, spermidine as predominant polyamine in the bacterium. The differential presence of C12:0, C14:0 2-OH, C18:1 ω7c, and C 14:0 iso 3-OH/ C16:1 iso fatty acids, phosphatidylglycerol (PG), phosphatidylcholine (PC), two unknown phospholipid (PL1, PL2) as polar lipids, low DNA-DNA relatedness (33.0-41.0%) with the Achromobacter members, and unique metabolic capacities clearly indicated the distinct genomic and physiological properties of strain KAs 3-5T among known species of the genus Achromobacter. These findings lead to improve our understanding on metabolic flexibility of bacteria residing in As-contaminated groundwater and As-bacteria interactions within oligotrophic aquifer system. [ABSTRACT FROM AUTHOR]

Abstract: Arsenic in groundwater is a serious problem in New England, particularly for domestic well owners drawing water from bedrock aquifers. The overlying glacial aquifer generally has waters with low arsenic concentrations but is less used because of frequent loss of well water during dry periods and the vulnerability to surface‐sourced bacterial contamination. An alternative, novel design for shallow wells in glacial aquifers is intended to draw water primarily from unconsolidated glacial deposits, while being resistant to drought conditions and surface contamination. Its use could greatly reduce exposure to arsenic through drinking water for domestic use. Hypothetical numerical models were used to investigate the potential hydraulic performance of the new well design in reducing arsenic exposure. The aquifer system was divided into two parts, an upper section representing the glacial sediments and a lower section representing the bedrock. The location of the well, recharge conditions, and hydraulic properties were systematically varied in a series of simulations and the potential for arsenic contamination was quantified by analyzing groundwater flow paths to the well. The greatest risk of arsenic contamination occurred when the hydraulic conductivity of the bedrock aquifer was high, or where there was upward flow from the bedrock aquifer because of the position of the well in the flow system. [ABSTRACT FROM AUTHOR]

Pyrite (FeS 2 ) is the most common sulfide mineral in the Earth's crust, and it commonly contains minor amounts of arsenic. Here we show that authigenic pyrite can remove arsenic from contaminated groundwater and this can be used as a new and relatively inexpensive remediation process. Laboratory batch experiments presented show that fine-grain natural pyrite is an effective sorber of dissolved arsenic. Arsenic sorption onto pyrite is shown to increase with increasing pH, particularly at pH > 5 and at elevated dissolved arsenic concentration. We also present results from a field experiment at an arsenic-contaminated industrial site, which demonstrates the results of stimulation of natural sulfate-reducing bacteria in groundwater by injection of a labile organic carbon source, iron, and sulfate. Within a week, bacterial sulfate reduction triggered the formation of biogenic pyrite nanoparticles, which sequestered arsenic by adsorption and co-precipitation. Microscopic and X-ray diffraction analyses confirmed that pyrite was the only iron-sulfide formed, and that no arsenic-only sulfide phase precipitated (e.g. orpiment or realgar). Pyrite occurs as either 1–10 μm euhedral crystals or similar-sized framboids both of which contain 500–4000 mg/kg arsenic. As a result, dissolved arsenic decreased from its initial concentration of 0.3–0.5 mg/L to below the regulatory clean-up standard for the site of 0.05 mg/L in a matter of weeks. In addition to the potential of this technique to remediate anthropogenic arsenic contamination, it is possible that it can be modified to inexpensively treat individual small drinking-water wells contaminated by natural sources of arsenic in many developing nations. [ABSTRACT FROM AUTHOR]

Arsenic concentrations above 10 μg L −1 were previously found in 89% of ground water sources in six villages of Pakistan. The present study has ascertained the health risks associated with exposure to total arsenic (tAs) and its species in most frequently consumed foods. Inorganic arsenic (iAs) concentrations were found to be 92.5 ± 41.88 μg kg −1 , 79.21 ± 76.42 μg kg −1 , and 116.38 ± 51.38 μg kg −1 for raw rice, cooked rice and wheat respectively. The mean tAs concentrations were 47.47 ± 30.72 μg kg −1 , 71.65 ± 74.7 μg kg −1 , 105 ± 61.47 μg kg −1 . Wheat is therefore demonstrated to be a significant source of arsenic exposure. Dimethylarsinic acid was the main organic species detected in rice, whilst monomethylarsonic acid was only found at trace levels. Total daily intake of iAs exceeded the provisional tolerable daily intake of 2.1 μg kg −1 day −1 body weight in 74% of study participants due to concurrent intake from water (94%), wheat (5%) and raw rice (1%). A significant association between tAs in cooked rice and cooking water resulted in tAs intake 43% higher in cooked rice compared to raw rice. The study suggests that arsenic intake from food, particularly from wheat consumption, holds particular significance where iAs is relatively low in water. Chronic health risks were found to be significantly higher from wheat intake than rice, whilst the risk in terms of acute effects was below the USEPA's limit of 1.0. Children were at significantly higher health risk than adults due to iAs exposure from rice and/or wheat. The dietary exposure of participants to tAs was attributable to staple food intake with ground water iAs <10 μg L −1 , however the preliminary advisory level (200 μg kg −1 ) was achievable with rice consumption of ≤200 g day −1 and compliance with ≤10 μg L −1 iAs in drinking water. Although the daily iAs intake from food was lower than total water intake, the potential health risk from exposure to arsenic and its species still exists and requires exposure control measures. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Groundwater arsenic contamination has become a serious global concern due to its adverse effects on human health. Arsenic-induced reactive oxygen species trigger oxidative stress inside mitochondria, which initiate a cascade of events including altered mitochondrial (mt) membrane potential, uncoupling of electron transport chain, and mtDNA damage. A case-control study was conducted to examine the association between arsenic exposure and differences in mtDNA methylation and to assess the downstream consequences. We recruited 221 arsenic-exposed individuals, including 106 individuals with skin lesions (WSL) and 115 subjects without any skin lesions (WOSL) from the Murshidabad district, West Bengal, India. The unexposed group included 101 individuals from the arsenic unexposed area in East Midnapore. We analyzed the status of mtDNA methylation in D-loop region and ND6 gene by methylation-specific PCR. Gene expression was studied by quantitative real-time PCR. Significant hypomethylation in both D-loop and ND6 was observed with a consequent increase in their target gene expression and higher mtDNA copy number in arsenic-exposed populations compared to controls. Further mechanistic insights regarding mitochondrial epigenetic alteration in arsenic exposure will be of critical importance for the prevention of adverse health effects. [ABSTRACT FROM AUTHOR]

Groundwater monitoring relies on the acquisition of ‘representative’ groundwater samples, which should reflect the ambient water quality at a given location. However, drilling of a monitoring well for sample acquisition has the potential to perturb groundwater conditions to a point that may prove to be detrimental to the monitoring objective. Following installation of 20 monitoring wells in close geographic proximity in central Florida, opposing concentration trends for As and Mo were observed. In the first year after well installation As and Mo concentrations increased in some wells by a factor of 2, while in others As and Mo concentrations decreased by a factor of up to 100. Given this relatively short period of time, a natural change in groundwater composition of such magnitude is not expected, leaving well installation itself as the likely cause for the observed concentration changes. Hence, initial concentrations were identified as ‘false negatives’ if concentrations increased with time or as ‘false positives’ if concentrations decreased. False negatives were observed if concentrations were already high, i.e., the As or Mo were present at the time of drilling. False positives were observed if concentrations were relatively lower, i.e., As or Mo were present at low concentrations of approximately 1 to 2 μg/L before drilling, but then released from the aquifer matrix as a result of drilling. Generally, As and Mo were present in the aquifer matrix in either pyrite or organic matter, both of which are susceptible to dissolution if redox conditions change due to the addition of oxygen. Thus, introduction of an oxidant into an anoxic aquifer through use of an oxygen saturated drilling fluid served as the conceptual model for the trends where concentrations decreased with time. Mixing between drilling fluid and groundwater (i.e., dilution) was used as the conceptual model for scenarios where increasing trends were observed. Conceptual models were successfully tested through formulation and application of data-driven reactive transport models, using the USGS code MODFLOW in conjunction with the reactive multicomponent transport code PHT3D. [ABSTRACT FROM AUTHOR]

Groundwater contamination by arsenic (As) is a major health/environmental concern due to its high toxicity to humans. Despite substantial research, there is scarce data in many countries regarding spatial distribution and As levels in groundwater, as well as its possible accumulation in humans/animals and associated health hazards. In this study, a total of 124 drinking water, 20 animal milk, 21 human hair, and 14 human nail samples were collected and analyzed for As contents from four tehsils (Bahawalnagar, Chishtian, Haroonabad and Minchinabad) of District Bahawalnagar. Geostatistical analysis and risk assessment models were used to predict the spatial distributions and health hazards of As in drinking water. Arsenic groundwater contents ranged between below detection limit (BDL) to 31.5 μg.L−1 with a mean of 7.6 μg.L−1. About 6 water samples (5%) contained As level > World Health Organization (WHO) limit. All these samples containing As contents > WHO limit were collected from Chishtian tehsil. In the case of milk samples, mean As contents were 75 μg.L−1 with a range of 42–111 μg.L−1. Arsenic was also detected in human hair (mean value of 640 μg kg−1 and range 71–2139 μg kg−1). However, As contents were BDL for all the nail samples. Risk assessment indices (cancer risk and hazard quotient) revealed possible health hazards due to their high values (3.0 and 0.0013, respectively). The principal component analysis (PCA) revealed that the potential sources of As release in the groundwater of study area do not match with those of other water variables. Hence, there is a need to monitor the groundwater quality of the Chishtian tehsil for any potential negative health impacts, as well as the possible sources of As in the groundwater of the study area. [Display omitted] • Arsenic contents analyzed in 124 water, 20 milk, 21 hair, and 14 nail samples. • Arsenic water contents were up to 31.5 μg.L−1 with a mean of 7.6 μg.L−1. • 5% water samples contained As level > WHO limit. • Arsenic was detected in milk (42–111 μg.L−1) and hair (71–2139 μg.L−1) samples. • Cancer risk and hazard quotient indices revealed potential risks in the study area. [ABSTRACT FROM AUTHOR]

High As concentration in groundwater of Datong Basin has emerged as an issue of great concern in the past decade because of its serious impact on the health of many people. The present study is to our knowledge the first attempt model the transport of arsenic in this system using a 1D reactive transport model (PHREEQC). Based on published field data from Shanyin Field Site (Datong Basin), the importance of the (bio)geochemical processes for arsenic mobility is evaluated quantitatively using geochemical models of growing complexity. Arsenic mobility during the surface water and groundwater interactions can be explained by the reductive dissolution of iron oxyhydroxides, sulfate, nitrate and arsenate, and by surface sorption/de-sorption occurring in response to changes in geochemical conditions. Both the Fe(III) surface complexation model and the 1D reactive transport model were employed to depict the arsenic transport in shallow groundwater system during the surface water-groundwater interactions. The surface complexation model results showed that a total of 0.34 mmol and 0.56 mmol arsenic were sorbed onto Fe(III) oxyhydroxides for Well 1-2S and Well 2-2S, respectively, reflecting the important role of surface sorption process on arsenic transport. The 1D model results revealed that redox processes were also critical. The improved calibration of model simulations involving both of these components indicates that the combination of processes is critical to understanding and characterising the transport of arsenic in groundwater during groundwater surface water interaction, especially close to the surface water body. [ABSTRACT FROM AUTHOR]

Exposure to naturally occurring arsenic in groundwater is a public health concern, particularly for households served by unregulated private wells. At present, one of the greatest barriers to exposure reduction is a lack of private well testing due to difficulties in motivating individual private well owners to take protective actions. Policy and regulations requiring testing could make a significant contribution towards universal screening of private well water and arsenic exposure reduction. New Jersey's Private Well Testing Act (PWTA) requires tests for arsenic during real estate transactions; however, the regulations do not require remedial action when maximum contaminant levels (MCLs) are exceeded. A follow-up survey sent to residents of homes where arsenic was measured above the state MCL in PWTA-required tests reveals a range of mitigation behavior among respondents (n = 486), from taking no action to reduce exposure (28%), to reporting both treatment use and appropriate maintenance and monitoring behavior (15%). Although 86% of respondents recall their well was tested during their real estate transaction, only 60% report their test showed an arsenic problem. Treatment systems are used by 63% of households, although half were installed by a previous owner. Among those treating their water (n = 308), 57% report that maintenance is being performed as recommended, although only 31% have tested the treated water within the past year. Perceived susceptibility and perceived barriers are strong predictors of mitigation action. Among those treating for arsenic, perceived severity is associated with recent monitoring, and level of commitment is associated with proper maintenance. Mention of a treatment service agreement is a strong predictor of appropriate monitoring and maintenance behavior, while treatment installed by a previous owner is less likely to be maintained. Though the PWTA requires that wells be tested, this study finds that not all current well owners are aware the test occurred or understood the implications of their arsenic results. Among those that have treatment installed to remove arsenic, poor monitoring and maintenance behaviors threaten to undermine intentions to reduce exposure. Findings suggest that additional effort, resources, and support to ensure home buyers pay attention to, understand, and act on test results at the time they are performed may help improve management of arsenic water problems over the long term and thus the PWTA's public health impact. [ABSTRACT FROM AUTHOR]

In this study, a wave rectified alternating current (RAC) electrocoagulation process was developed for the oxidative sequestration of As(III) via simultaneous generating Fe(II) and O2 in the synthesized anoxic groundwater. The optimal TFe-anode/TMMO-anode:Tpower-off ratio (T is the time-taken in corresponding stage) and reaction period for As(III) sequestration were 1:2:1 and 24 s, respectively. Elevating electric current applied on the alternate iron/MMO anodes (30–50 mA) and solution pH (6.0–9.0) promoted As(III) sequestration, whereas the presence of HCO3– and PO43– deteriorated As(III) sequestration. The intermediate Fe(IV) primarily accounted for the oxidation of As(III) to As(V), which can be readily sequestrated by the freshly generated Fe(III) (oxyhydr)oxides. The energy required for As(III) sequestration in the RAC electrocoagulation process was only 0.11 kW·h m–3, which is much less than those in the traditional DC/AC electrocoagulation processes. Generally, this study offers an energy-efficient strategy to improve access to safe groundwater for millions of people. [ABSTRACT FROM AUTHOR]

High spatial variability of arsenic (As) concentration in geogenic As-contaminated groundwater has been commonly observed worldwide, but the underlying reasons remain not well understood. Selecting a sulfate-containing, As-affected aquifer at the Datong Basin, northern China as the study area and combining hydrogeochemical investigation and sediment extraction with reactive transport modeling, this work elucidated the roles of Fe-S-As interactions in regulating the vertical variation of As concentration in the groundwater. Dissolved As concentration varied between 0.05 and 18 μmol/L, but generally increased in the depth of 20–25 m and then decreased in 25–30 m. The high-As groundwater contained low Fe(II) (<0.007 mmol/L) and up to 15 μmol/L sulfide, in contrary to the S/SE Asian deltas/floodplains where high Fe(II) and As jointly occur in the groundwater devoid of sulfate reduction. The reductive dissolution of As-bearing Fe(III) oxides coupled to the degradation of organic matter with an estimated maximum rate of 0.22 mmol C/L/yr, mainly accounted for the depth-dependent increase of As concentration in the upper part of the shallow aquifer (<25 m deep). However, the decreasing reactivity of Fe(III) oxides together with the increase of pH over depth rendered the majority of electrons being transferred to sulfate reduction. The Fe(II) sulfides formed as a consequence not only helped to restrict the build-up of Fe(II) in the groundwater but also probably co-precipitated As to prompt As decrease in the depth of 25–30 m. Arsenite adsorbed on remaining Fe(III) oxides and newly-formed Fe(II) sulfides is another important pool of As in the aquifer, which varies in response to the extents of Fe(III)-oxide and sulfate reduction and consequently alters As distribution coefficient between the solid and the aqueous phases. This study highlights the importance of coupled geochemical cycling of Fe, S and As for As mobilization and reveals how it regulates As partitioning between groundwater and sediments. [ABSTRACT FROM AUTHOR]

Geochemical investigation was carried out for delineating factors responsible for the mobilization of arsenic (As) from aquifer material into the groundwater. Four sites along Ravi River, ( Samada, Sarai Chimba, Kot Maiga and Chah Fatehwala) , were selected based on the blanket survey. Groundwater-rock interaction and evaporation were the key phenomena controlling groundwater chemistry, as shown by the hydrogeochemical data. Groundwater was predominantly Na-Cl type, with other principle facies being Na-HCO 3 , Na-Ca-HCO 3 and Ca-Mg-Cl. The groundwater As concentration ranged between below detection level (2 μg/L) to 548 μg/L with 59% samples exceeding the World Health Organization (WHO) guidelines for As in drinking water (10 μg/L) and 31% having higher concentrations than the National Environmental Quality Standard (NEQS, 50 μg/L). Moderate to high concentrations of SO 4 −2 averaged at 244 mg/L and moderate NO 3 − concentrations averaged at 8 mg/L, together with alkaline pH (7.3–8.8) and high Eh values (113–402 mV) suggest partial oxidizing nature of the aquifers. The values for δ 18 O and δ 2 H in groundwater varied between −9.14 and −5.51‰, and −56.57 to −39.5‰ respectively, and suggests meteoric origin of the groundwater with some evaporative loss. This effect could be partly responsible for elevated levels of pH and salinity in groundwater. Based on geochemical and isotopic composition of groundwater, desorption of As from metal surfaces under alkaline environment might be the factor causing As enrichment in study area. [ABSTRACT FROM AUTHOR]

In this study, we tested 123 groundwater wells from five different areas of Punjab, Pakistan for arsenic (As) contamination level and species, as well as delineated hydrogeochemical behaviour of As in aquifers. Results revealed that 75% and 41% of the groundwater wells exceeded the safe As limit of World Health Organisation (WHO, 10 μg L −1 ) and Pakistan-EPA (50 μg L −1 ), respectively. Arsenite (As(III)) and arsenate (As(V)) spanned 0–80% and 20–100% of total As (1.2–206 μg L −1 ), respectively. The mean As content (5.2 μg L −1 ) of shallow wells at 9–40 m depth did not exceed the WHO safe limit, representing a safe aquifer zone for pumping of groundwater compared to deeper wells at 41–90 m (51 μg L −1 ) and >90 m (23 μg L −1 ) depths. Piper-plot elucidated that the aqueous chemistry was dominated with Na-SO 4 , Na-Ca-SO 4 , Na-Mg-SO 4 type saline water. Principal component analysis grouped As concentration with well depth, pH, salinity, Fe and CO 3 , exhibiting that these hydrogeochemical factors could have potential role in controlling As release/sequestration into the aquifers of study area. Geochemical modeling showed positive saturation indices only for iron (Fe) oxide-phases, indicating Fe oxides as the major carriers of As. Overall, this study provides insights to tackle emerging As threat to the communities in Punjab, Pakistan, as well as help develop suitable management/mitigation strategies – based on the baseline knowledge of As levels/species and factors governing As contamination in the study area. [ABSTRACT FROM AUTHOR]

Arsenic (As)-contaminated groundwater is a global concern with potential detrimental effects on the health of hundreds of millions of people worldwide. However, the extent of this problem may be more severe than anticipated, as many wells have not been tested and may contain unsafe-level of As. An optimized statistical regression model was developed to predict the probability of geogenic high As groundwater (As > 10 μg/L) in this study. Easily obtained hydrogeochemical and geological parameters that are significantly related to As geochemical behaviors were selected as explanatory variables in the model. The results indicate that pH, Cl − , HCO 3 − , SO 4 2− , and NO 3 − concentrations, stratigraphic information, and well depth are excellent predictors of As exposure in the Datong Basin, China. Predicted unsafe wells correspond well with the known distribution of high As groundwater in the Datong Basin. The successful application of a data set from Bangladesh also demonstrated the applicability and credibility of this proposed method. [ABSTRACT FROM AUTHOR]

Regularmonitoring of arsenic (As) in groundwater is crucial frompublic health perspectives as millions of people are suffering due to use of contaminated aquifer water for drinking purposes. The routine analyses, especially in developing nations, are mostly done in localised government/non-government laboratories with limited resources, having the target of analysing large number of samples in each run. Thus apart from analytical sensitivity, cost-effectiveness of the method and eco-friendliness of the experimental operation are key surreptitious factors. This demands optimisation of total As measurement methods and finding a method that gives 'optimumbenefit' considering all these factors together. The present study therefore evaluates four common As (total) measurement methods [iodometric-colorimetric method, silver diethyl dithiocarbamate method, molybdenum blue method and hydride generation atomic absorption spectrophotometric (HG-AAS) method] practised in the Bengal Delta Plain, in view of their analytical sensitivity, related environmental hazard and experimental costs. It was found that the HG-AAS method is analytically more sensitive, whereas the iodometric-colorimetricmethod and the molybdenum blue method are better choices in terms of eco-friendliness and cost-effectiveness, respectively. However, when all three factors (analytical reliability, environmental hazard and cost) are considered simultaneously, themolybdenumbluemethodwas found to be placed first in the 'optimum performance rank' list. It was also found that both environmental hazard and cost play a more crucial role than analytical reliability, although this is case specific andwould differ from place to place around the globe. Finally based on the results, we have hypothesised a water testing strategy for developing countries such as India where the molybdenum blue method can be adapted as a screening method and later the HG-AASmethod can be used to precisely identify the groundwater samples with As concentration below the WHO drinking water guideline value of 10 μg/L. [ABSTRACT FROM AUTHOR]

Drinking water contaminated with arsenic poses serious threat to the human health. The present study was aimed for quality assessment of the groundwater of Khairpur Mir's in respect with arsenic and other elemental contamination like Fe, Cu, Co, and Ni. The presence of the trace elements in groundwater from different sources in the study area was measured by using atomic absorption spectroscopy. For arsenic analysis hydride generation technique (MHS-15) was used with detection limit of 0.02 µg l−1. Elevated level of arsenic was observed in most of the samples as compared to recommended value of World Health Organization (WHO) guidelines (10 µg l−1). However, levels of Fe, Cu, Co, and Ni in hand pump (HP) water samples was found in the range of 4-1610 µg l−1, 0-556 µg l−1, 0-230 µg l−1, and 0-700 µg l−1, respectively. Whereas in tube well (TW) water samples the observed values are 5-1620 µg l−1, 0-50 µg l−1, 4-110 µg l−1, and 0-360 µg l−1 for Fe, Cu, Co, and Ni, respectively. Significant difference was observed between TW and HP water samples. It was concluded that the level of arsenic found was very high up to 13 fold more than the WHO recommended limit in study area. While the levels of other elements was noted within the safe limit. [ABSTRACT FROM AUTHOR]

Water from La Pampa, Argentina, was used for washing and cooking rice to examine the in-situ impact of using naturally-contaminated water for food preparation on the elemental dietary intake. Whilst washing with the control tap water (28 μg/L As) reduced the concentration of As in rice by 23%, the use of different well waters (281–1144 μg/L) increased As levels significantly (48–227%) in comparison with the original concentration in the rice (0.056 µg/g). Cooking the rice at a low water-to-rice ratio (2:1) using modern methods increased the levels of As in the cooked samples by 2–3 orders of magnitude for both pre-washed and un-washed rice. Similar trends were observed for vanadium. Although the levels of manganese, iron, copper, zinc and molybdenum in rice were reduced during washing and cooking for most water samples, the molybdenum concentration in the cooked rice doubled (2.2–2.9 µg/g) when using water containing >1 mg/L Mo. [ABSTRACT FROM AUTHOR]

In this study, we examined the sorption of arsenite (As(III)) and arsenate (As(V)) to Japanese oak wood-derived biochar (OW-BC) in aqueous solutions, and determined its efficiency to remove As from As-contaminated well water. Results revealed that, among the four sorption isotherm models, Langmuir model showed the best fit to describe As(III) and As(V) sorption on OW-BC, with slightly greater sorption affinity for As(V) compared to As(III) ( Q L = 3.89 and 3.16 mg g − 1 ; R 2 = 0.91 and 0.85, respectively). Sorption edge experiments indicated that the maximum As removal was 81% and 84% for As(III)- and As(V)-OW-BC systems at pH 7 and 6, respectively, which decreased above these pH values (76–69% and 80–58%). Surface functional groups, notably OH, COOH, C O, CH 3 , were involved in As sequestration by OW-BC, suggesting the surface complexation/precipitation and/or electrostatic interaction of As on OW-BC surface. Arsenic K-edge X-ray absorption near edge structure (XANES) spectroscopy indicated that 36% of the added As(III) was partially oxidized to As(V) in the As(III) sorption experiment, and in As(V) sorption experiment, 48% of As(V) was, albeit incompletely, reduced to As(III) on OW-BC surface. Application of OW-BC to As-contaminated well water (As: 27–144 μg L − 1 ; n = 10) displayed that 92 to 100% of As was depleted despite in the presence of co-occurring competing anions (e.g., SO 4 2 − , CO 3 2 − , PO 4 3 − ). This study shows that OW-BC has a great potential to remove As from solution and drinking (well) water. Overall, the combination of macroscopic sorption data and integrated spectroscopic and microscopic techniques highlight that the fate of As on biochar involves complex redox transformation and association with surface functional moieties in aquatic systems, thereby providing crucial information required for implication of biochar in environmental remediation programs. [ABSTRACT FROM AUTHOR]

Reductive transformation of toxic arsenic (As) species by As reducing bacteria (AsRB) is a key process in As-biogeochemical-cycling within the subsurface aquifer environment. In this study, we have characterized a Gram-stain-negative, non-spore-forming, rod-shaped As reducing bacterium designated KAs 5-3T, isolated from highly As-contaminated groundwater of India. Strain KAs 5-3T displayed high 16S rRNA gene sequence similarity to the members of the genus Pseudoxanthomonas, with P. mexicana AMX 26BT (99.25% similarity), P. japonensis 12-3T (98.9 0%), P. putridarboris WD-12T (98.02%), and P. indica P15T (97.27%) as closest phylogenetic neighbours. DNA-DNA hybridization study unambiguously indicated that strain KAs 5-3T represented a novel species that was separate from reference strains of P. mexicana AMX 26BT (35.7%), P. japonensis 12-3T (35.5%), P. suwonensis 4M1T (35.5%), P. wuyuanensis XC21-2T (35.0%), P. indica P15T (32.5%), P. daejeonensis TR6-08T (32.0%), and P. putridarboris WD12T (22.1%). The DNA G+C content of strain KAs 5-3T was 64.9 mol %. The predominant fatty acids were C15:0 (37.4%), C16:0 iso (12.6%), C17:1 iso ω9c (10.5%), C15:0 anteiso (9.5%), C11:0 iso 3-OH (8.5%), and C16:1 ω7c/ C16:1 ω6c (7.5%). The major polar lipids were diphosphatidylglycerol, phosphatidyldimethylethanolamine, phosphatidylcholine, and two unknown phospholipids (PL1, PL2). Ubiquinone 8 (Q8) was the predominant respiratory quinone and spermidine was the major polyamine of the strain KAs 5-3T. Cells of strain KAs 5-3T showed the ability to use O2, As5+, NO3-, NO2-, and Fe3+ as terminal electron acceptors as well as to reduce As5+ through the cytosolic process under aerobic incubations. Genes encoding arsenate reductase (arsC) for As-detoxification, nitrate- and nitrite reductase (narG and nirS) for denitrification were detected in the strain KAs 5-3T. Based on taxonomic and physiological data, strain KAs 5-3T is described as a new representative member of the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas arseniciresistens sp. nov. is proposed. The type strain is KAs 5-3T (= LMG 29169T = MTCC 12116T = MCC 3121T). [ABSTRACT FROM AUTHOR]

Low-grade siderite tailings are difficult to be utilized. For further exploration on the application of siderite tailings for arsenic removal, a series of theoretic and practical studies were carried out. According to the experiment results and technical specifications, a water supply well using composite filtration materials of siderite and river sands was designed and a pilot run was conducted in Datong basin, China, where the groundwater notably contains high concentrations of arsenic. Particle size of 1–2 mm was selected as the optimum scheme considering the adsorption kinetic parameters and technical specifications. Langmuir isotherm yielded a better fit to experimental data with regard to the siderite with a grain size range of 1–2 mm (R 2 = 0.983), which indicated that the process generally tends to be a monolayer adsorption reaction with a saturation adsorption capacity of 0.5233 mg g −1 . Volume proportion coefficients α = 0.5 was selected as the optimal scheme in view of economic factors. The supply water well using composite filtration materials as a pilot run performed well, with average effluent concentration of 247.57 μg L −1 , and arsenic removal rates of 52%–65%. The mechanism for arsenic removal is likely due to the hydroxyl group of Fe(OH)x/FeOOH which contributed from the hydrolysis of FeCO 3 , and subsequently substituted by aqueous arsenic. Moreover, the groundwater chemical environment contains high sulfide concentrations, which enhances the sorption of arsenic. [ABSTRACT FROM AUTHOR]

A facultative anaerobic iron reducing bacterium IMCUGIR-ZA was isolated from high arsenic (As) groundwater in Hetao Basin of Inner Mongolia and was identified as Klebsiella oxytoca . Strain IMCUGIR-ZA could reduce more than 96.8% of 2.78 mmol L −1 soluble Fe(III)-citrate in 7 days and 0.42 mmol solid iron from ferrihydrite into aqueous phase in 10 days using glucose as an electron donor under strictly anaerobic conditions. Appropriate concentrations of As could improve microbially-mediated iron reduction and release from ferrihydrite. Nearly threefold iron was reduced and released by strain IMCUGIR-ZA from As(V)-doped ferrihydrite (As 100 μmol L −1 ). When the strain was incubated with high arsenic sediments from Hetao Basin of Inner Mongolia under anaerobic conditions, 0.894 mmol L −1 Fe(III) and 12.44 μmol L −1 As were released to aqueous phase in 7 days. The results provided evidence of microbially-mediated mobilization of As in high arsenic groundwater aquifer in Hetao Basin of Inner Mongolia, China. [ABSTRACT FROM AUTHOR]

High arsenic (As) groundwater has been widely found in the Yellow River catchment, which has posed potential risks on health of local residents. However, it is still unknown how fractions and reactivity of Fe-bearing minerals control As mobility in groundwater system. As a typical basin in the catchment, the Hetao basin was selected as the study area to investigate roles of fractions and reactivity of Fe-bearing minerals in groundwater As. Seventy sediment samples and eight groundwater samples were collected in a representative borehole in the basin. Sequential extraction and kinetic experiment were carried out to characterize fractions and reactivity of Fe-bearing minerals, respectively. Results showed that groundwater in shallow zone (between 10 and 36 m depths) had lower ORP values and higher As concentrations (average = 279 μg/L) than deep zone (average = 158 μg/L). In shallow zone, the predominant reactive Fe phase was reducible oxides (Fe ox2 ), while in deep zone it was carbonate associated Fe (Fe carb ). Fe ox2 had the highest amounts of As and As/Fe ratios, followed by Fe carb and easily reducible oxides (Fe ox1 ). Moreover, As/Fe ratios in Fe ox2 had the best correlation with As/Fe ratios in groundwater. The largest partition coefficients were obtained between As in Fe ox2 and groundwater As ( K d-ox2 ). Kinetic experiments showed that sediments having higher reactivity ( k’ ) and heterogeneity ( γ ) had higher As/Fe ratios. Reactivity of sediment samples fell into the range between synthetic lepidocrocite and poorly crystalline goethite. Arsenic partition coefficients between reactive minerals and groundwater ( K d-reac ) showed a positive correlation with ORP values, indicating that reductive dissolution of Fe(III) oxides played the important role in As mobilization. Therefore, reducing conditions, high k’ , γ and Fe ox2 contents in sediments led to high As concentrations in groundwater. [ABSTRACT FROM AUTHOR]

Co-contaminant behavior of arsenic (As) and selenium (Se) in groundwater is examined in this study at a former lead and zinc smelting facility. We collected water quality data, including concentrations of trace metals, major ions, and metalloid speciation, over a 15-year period to document long-term trends and relationships between As, Se, geochemical parameters, and other redox-sensitive trace metals. Concentrations of dissolved As and Se were negatively correlated (Kendall's Tau B correlation coefficient, r = −0.72) and showed a distinctive L-shaped relationship. High-concentration arsenic wells (>5 mg L −1 ) were characterized by intermediate oxidation-reduction conditions (75 < Eh < 275 mV), near-neutral pH (6.1–7.9), low Ca/Na ratios, elevated Fe and Mn concentrations, and high proportions of As(III) relative to total dissolved As. High-concentration Se wells (>500 μg L −1 ) were characterized by more positive Eh (305–500 mV), low Fe concentrations, and high proportions of As(V). Batch micocosm experiments showed that aquifer solids contain mineral surfaces and/or microbial communities capable of removing selenate from groundwater. Electron microprobe and Se K -edge X-ray absorption near-edge spectroscopic analyses demonstrated that Se was predominantly associated with elemental Se in the reduced aquifer solids. Factor analysis revealed three discernible groupings of trace metals. Group I includes U, Se, and nitrate-N, all of which are mobile under oxygenated to moderately oxygenated conditions. Group II includes elements that are mobile under Fe(III)-reducing conditions: Fe, total dissolved As, As(III), and ammonium-N. Group III elements (Mo, Sb, and V) showed mobility across the entire range of redox conditions encountered in site groundwater; As(V) clustered with this group of elements. Geochemical modeling suggests that As and Se species were in a state of disequilibrium with respect to measured parameters indicative of redox conditions, although predicted patterns of redox-controlled mobility and attenuation were confirmed. This analysis is important to better understand groundwater contaminant behavior in response to redox conditions ranging from oxic/suboxic to Fe(III)-reducing, but excluding sulfate-reducing conditions. [ABSTRACT FROM AUTHOR]

The Xikuangshan(XKS) mine, the world’s largest antimony mine, was chosen for a detailed arsenic hydrogeochemical study because of the elevated arsenic in bedrock aquifers used by local residents. Hydrochemical data, δ 34 S values of dissolved SO 4 2− and 87 Sr/ 86 Sr ratios have been analyzed to identify the predominant geochemical processes that control the arsenic mobilization within the aquifers. Groundwater samples can be divided into three major types: low arsenic groundwater (0–50 µg/L), high arsenic groundwater (50–1000 µg/L) and anomalous high arsenic groundwater (>1000 µg/L). Arsenic occurs under oxidizing conditions at the XKS Sb mine as the HAsO 4 2− anion. The Ca/Na ratio correlates significantly with HCO 3 − /Na and Sr/Na ratios, indicating that carbonate dissolution and silicate weathering are the dominant processes controlling groundwater hydrochemistry. The δ 34 S values of the groundwater indicate that dissolved SO 4 2− in groundwater is mainly sourced from the oxidation of sulfide minerals, and elevated As concentrations in groundwater are influenced by the mixing of mine water and surface water. Furthermore, the δ 34 S values are not correlated with dissolved As concentrations and Fe concentrations, suggesting that the reduction dissolution of Fe(III) hydroxides is not the dominant process controlling As mobilization. The 87 Sr/ 86 Sr ratios imply that elevated As concentrations in groundwater are primarily derived from the interaction with the stibnite and silicified limestone. More specifically, the excess-Na ion, the feature of Ca/Na ratio, and the spatial association of elevated As concentrations in groundwater collectively suggest that high and anomalous high arsenic groundwater are associated with smelting slags and, in particular, the arsenic alkali residue. In general, the hydrochemistry analysis, especially the S and Sr isotope evidences elucidate that elevated As concentrations and As mobilization are influenced by several geochemical processes, including: (1) bedrock weathering; (2) oxidation of arsenopyrite and the dominant sulfides in the ores; (3) mixing of mine drainage and surface water; (4) leaching of the arsenic alkali residue; and (5) sorption-desorption from Fe/Mn oxides/hydroxides. [ABSTRACT FROM AUTHOR]

Less is known about controls of sedimentary structures in groundwater As distributions in sedimentary aquifers, and quantitative description of relationship between sedimentary environment and high As groundwater (according to WHO, As > 10 μg/L) is a challenging issue. Three hundred and eighty-two hydrogeological borehole loggings (well depths of 50–300 m) were collected and four hundred and ninety nine groundwater samples were taken to investigate controls of paleochannels on groundwater arsenic distribution in shallow aquifers of alluvial plain in the Hetao Basin. Results showed that the swing zone, formed by bursting, diversion and swing of ancient Yellow River course since the Late Pleistocene, has an obviously corresponding relationship with spatial variability of groundwater As in the Hetao Basin. “Swing Intensity Index” ( S ), which is firstly defined as the sum of clay-sand ratio ( R ) and the number of clay layers ( N ), can be used as the sedimentary facies symbol to establish the new recognition method for hosting high As groundwater. There is a positive correlation between the swing intensity index ( S ) of paleochannels and groundwater As concentrations. The swing zones of paleochannels with high S values represent hydrogeochemical characteristics of the strong reducing environment, serious evaporation, strong cation exchange, and the low infiltration recharge of surface water, which lead to enrichment of groundwater As in the shallow aquifers. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the feasibility of adsorption of aluminium oxide nanoparticles for arsenite, which is toxic and prevalent arsenic species under anoxic condition in groundwater. Therefore, aluminium oxide nanoparticles were synthesised and characterised by Dynamic Light Scattering, Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray spectrometry, Fourier Transform Infrared Spectroscopy, X-ray Diffraction and Transmission Electron Microscopy. Batch adsorption studies were performed as a function of contact time, initial arsenite concentration, adsorbent dose, temperature, pH and influence of other competing anions. The arsenite adsorption was well explained by Freundlich isotherm model. Langmuir adsorption capacity was found to be 500 μg/g at 298 K. The kinetic data followed pseudo-second-order model with film diffusion step controlling the mechanism. The values of thermodynamic parameter, ΔH° was − 26.09 kJ/mol, while the values of ΔG° were − 3.75, − 2.99, − 2.20 and − 1.49 kJ/mol at 298, 308, 318 and 328 K respectively, suggesting exothermic and spontaneous nature of the process. The change in entropy (ΔS° = − 0.075 kJ/mol) indicated the decrease in entropy of the system, as adsorbate concentration increased on aluminium oxide nanoparticles surface and reduced the mobility of arsenite. The activation energy (Ea) content of the process was found as 5.64 kJ/mol, which confirmed the nature of adsorption as the physical adsorption. The results indicated the potential utility of Al 2 O 3 nanoparticles for arsenite removal from any natural water resources. [ABSTRACT FROM AUTHOR]

Arsenite was effectively immobilized by 2-line ferrihydrite at different pH values (4.0, 5.5 and 7.4) and adsorbent dosages (0.4, 1, and 2 g/L) in the absence of oxygen, showing an initial surface diffusion-controlled period (Stage I, <2 h) and a second mixed intra-particle and surface diffusion-controlled period (Stage II, >2 h). Dissolved δ 56 Fe increased during Stage I and decreased during Stage II, resulting from aging of ferrihydrite and equilibrium isotopic exchange, respectively. The ferrihydrite aging was hampered by both high As concentrations and high pH values close to the pH zpc , due to inhibition of mineral dissolution as a prerequisite for mineral transformation. During Stage I, As was adsorbed by both bidentate binuclear corner-sharing ( 2 C ) and monodentate mononuclear corner-sharing complexes ( 1 V ), while 2 C dominated during Stage II. At stage I, As stability was mainly controlled by As-complexation, by both mineral transformation and As complexation at stage II. It is suggested that adsorbed-As stability can be optimized by regulating As complexation and mineral phases, which are of great significance for remediation of As-contaminated groundwater. [ABSTRACT FROM AUTHOR]

The area east of Varanasi is one of numerous places along the watershed of the Ganges River with groundwater concentrations of arsenic surpassing the maximum value of 10 parts per billion (ppb) recommended by the World Health Organization in drinking water. Here we apply geostatistics and compositional data analysis for the mapping of arsenic and iron to help in understanding the conditions leading to the occurrence of elevated level of arsenic in groundwater. The methodology allows for displaying concentrations of arsenic and iron as maps consistent with the limited information from 95 water wells across an area of approximately 210 km; visualization of the uncertainty associated with the sampling; and summary of the findings in the form of probability maps. For thousands of years, Varanasi has been on the erosional side in a meander of the river that is free of arsenic values above 10 ppb. Maps reveal two anomalies of high arsenic concentrations on the depositional side of the valley, which has started seeing urban development. The methodology using geostatistics combined with compositional data analysis is completely general, so this study could be used as a prototype for hydrochemistry mapping in other areas. [ABSTRACT FROM AUTHOR]

In the southern part of the Cenozoic Duero Basin (Spain), naturally occurring arsenic and uranium in groundwater sometimes occur in concentrations exceeding the limits for potable water. Usually, concentrations of these elements are only slightly above the limit, but this is sufficient to invalidate its use as drinking water. Hydrogeotoxic risk or hydrogeotoxicity (HGT) is defined as the quotient between the observed concentration of an element and the limit set by health regulations (such as by the World Health Organization, WHO). Areas at risk of HGT from a given Potentially Toxic Geogenic Trace Element (PTGTE) are defined a quotient of > 1. Hydrogeotoxicity of arsenic and uranium (HGT As and HGT U ) were calculated for water samples and 34% returned HGT As above 1. For uranium, different HGT indexes were considered against a variety of thresholds for drinking water established by different countries and organizations (10 μg/L, Germany; 15 μg/L, WHO, 2004; 30 μg/L, WHO, 2011/US-EPA, 2011): 48% samples returned HGT U10 > 1; 29% samples, HGT U15 > 1 and 7% had HGT U30 > 1. In the water samples analyzed, the highest arsenic content were usually associated with the highest uranium concentrations. However sometimes these two hydrogeotoxicities do not coincide and the HGT As and HGT U10 distributions show different patterns. Hydrogeotoxicity due to more than one element (HGT As and HGT U10 ) was also considered; 17% samples showed a potentially hydrogeotoxic risk linked to both PTGTEs, leading to the delimitation of these zones as especially vulnerable to a combined hydrogeotoxic hazard. The linear distribution of HGT As seems to be related to the structure of the Cenozoic Duero Basin and to deep water inflows that are enriched in As and U, which are associated with its fissured basement. The HGT U can be partly linked to these deep flows with a significant hydrothermal component, but they are also linked to secondary processes occurring in the sedimentary basin, which could explain the scattered distribution of HGT U in some areas. As well as the HGT values, which are based on total concentrations, bioavailability of arsenic and uranium species was also considered in order to provide a comprehensive assessment of hydrogeotoxic risk over the study area. In all samples with HGT As > 1, arsenic was present as As(V) inorganic form. Likewise, in samples with HGT U10 > 1, uranium appears as U(VI). This hydrogeotoxic anomaly must be related to both the chemical and radiological hazards. [ABSTRACT FROM AUTHOR]

Arsenic exists ubiquitously in both groundwater and surface water and it is extremely harmful to human health. In this study, basic yttrium carbonate (BYC) was successfully synthesized using the one-step precipitation method and for the first time, we report the removal of arsenate [As(V)] from aqueous solution by BYC through fixed-bed column. Effects of various parameters, including BYC dosage, As(V) concentration, flow rate, solution pH, and coexisting anions, on adsorption efficiency were investigated. Results demonstrate that the adsorption rate and capacity of As(V) increased with decreasing BYC dosage and with an increase of As(V) concentration or flow rate. Removal of As(V) was pH dependent and optimum adsorption efficiency was achieved at pH 6. Presence of NO3−, SO42−, and CO32− had a weak influence on removal of As(V); however, PO43− significantly inhibited As(V) adsorption, suggesting that As(V) was specifically adsorbed by BYC. Under acidic and neutral conditions, ligand exchange between As(V) and hydroxyl groups or carbonate on the surface of BYC was mainly responsible for As(V) removal, while the precipitation of As(V) and Y3+ ions released from BYC partially contributed to removal of As(V). Under alkaline conditions, however, no precipitation reaction was observed. Our results reveal the underlying mechanism of As(V) removal by BYC and provide a valuable reference for practical application. [ABSTRACT FROM AUTHOR]

Shallow groundwater containing toxic concentrations of arsenic is the primary source of drinking water for millions of households in rural West Bengal, India. Often, this water also contains unpleasant levels of iron and non-negligible fecal contamination. Alternatives to shallow groundwater are increasingly available, including government-built deep tubewells, water purchased from independent providers, municipal piped water, and household filters. We conducted a survey of 501 households in Murshidabad district in 2014 to explore what influenced the use of available alternatives. Socioeconomic status and the perceived likelihood of gastrointestinal (GI) illness (which was associated with dissatisfaction with iron in groundwater) were the primary determinants of the use of alternatives. Arsenic knowledge was limited. The choice amongst alternatives was influenced by economic, social, and aesthetic factors, but not by health risk perceptions. The use of purchased water was rarely exclusive and was strongly associated with socioeconomic status, suggesting that this form of market-based water provision does not ensure universal access. Demand for purchased water appeared to decrease significantly shortly after free piped water became available at public taps. Our results suggest that arsenic mitigation interventions that also address co-occurring water problems (iron, GI illness) could be more effective than a focus on arsenic alone. [ABSTRACT FROM AUTHOR]