Dataset Information

Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh.

ABSTRACT: Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout the study. Groundwater and gray sediment were collected as diluted slurries between 5 and 38 m in depth, a range over which ambient groundwater As concentrations increased from 20 to 100 microg L(-1). Arsenic was released to groundwater in slurries from 5 and 12 m in depth at a relatively constant rate of 21 +/- 4 (2 sigma) and 23 +/- 6 microg As kg(-1) yr(-1), respectively. Amendment with a modest level of acetate increased the rate of As release only at 12 m (82 +/- 18 mirog kg(-1) yr(-1)). Although the groundwater As concentration was initially highest at 38 m depth, no release of As was observed. These results indicate that the spatial distribution of dissolved As in Bangladesh and local rates of release to groundwater are not necessarily linked. Iron release during the incubations did not occur concurrently with As release, providing further confirmation thatthe two processes are not directly coupled. Small periodic additions of oxygen suppressed the release of As from sediments at all three depths, which supports the notion that anoxia is a prerequisite for accumulation of As in Bangladesh groundwater.

SUBMITTER: Radloff KA

PROVIDER: S-EPMC2577162 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh.

Radloff Kathleen A KA Cheng Zhongqi Z Rahman Mohammad W MW Ahmed Kazi M KM Mailloux Brian J BJ Juhl Andrew R AR Schlosser Peter P Van Geen Alexander A

Environmental science & technology 20070501 10

Elevated As concentrations in shallow groundwater pose a major health threat in Bangladesh and similarly affected countries, yet there is little consensus on the mechanism of As release to groundwater or how it might be influenced by human activities. In this study, the rate of As release was measured directly with incubations lasting 11 months, using sediment and groundwater collected simultaneously in Bangladesh and maintained under anaerobic conditions throughout the study. Groundwater and gr ...[more]

PMID: 17547190

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Project description:BackgroundExposure to inorganic arsenic (As) from drinking water is associated with modest deficits in intellectual function in young children; it is unclear whether deficits occur during adolescence, when key brain functions are more fully developed.ObjectivesWe sought to determine the degree to which As exposure is associated with adolescent intelligence, and the contributory roles of lead, cadmium, manganese and selenium.MethodsWe recruited a cross-section of 726 14-16 year olds (mean age = 14.8 years) whose mothers are participants in the Bangladesh Health Effects of Arsenic Longitudinal Study (HEALS), and whose household well water As levels, which varied widely, were well characterized. Using a culturally modified version of the WISC-IV, we examined raw Full Scale scores, and Verbal Comprehension, Perceptual Reasoning, Working Memory and Processing Speed Indices. Blood levels of As (BAs), Mn, Pb, Cd and Se were assessed at the time of the visit, as was creatinine-adjusted urinary As (UAs/Cr).ResultsLinear regression analyses revealed that BAs was significantly negatively associated with all WISC-IV scores except for Perceptual Reasoning. With UAs/Cr as the exposure variable, we observed significantly negative associations for all WISC-IV scores. Except for Se, blood levels of other metals, were also associated with lower WISC-IV scores. Controlling for covariates, doubling BAs, or UAs/Cr, was associated with a mean decrement (95% CI) of 3.3 (1.1, 5.5), or 3.0 (1.2, 4.5) points, respectively, in raw Full scale scores with a sample mean of 177.6 (SD = 36.8). Confirmatory analyses using Bayesian Kernel Machine Regression, which identifies important mixture members, supported these findings; the primary contributor of the mixture was BAs, followed by BCd.ConclusionsOur data indicate that the adverse consequences of As exposure on neurodevelopment observed in other cross-sectional studies of younger children are also apparent during adolescence. They also implicate Cd as a neurotoxic element that deserves more attention.

Project description:BackgroundConcentrations of arsenic (As) are elevated in a large proportion of wells in Bangladesh but are spatially variable even within a village. This heterogeneity can enable exposed households to switch to a nearby well lower in As in response to blanket (area-wide) well As testing.ObjectivesWe document the evolution of As exposure in Araihazar, Bangladesh following a blanket well testing and education campaign, as well as the installation of a considerable number of low As community wells.MethodsWe use well water and urinary As data collected between 2000 and 2008, along with household interviews extending through 2016, within a 25 km2 area of Araihazar upazila for nearly 12,000 participants enrolled in the Health Effects of Arsenic Longitudinal Study (HEALS). We observe changes in participants' well water and urinary As concentrations following interventions to lower their exposure and use logistic regression to determine the factors associated with participants' decisions to switch primary household wells.ResultsUrinary As for participants drinking from wells with >100 μg/L As at baseline declined from a mean of 226 μg/L at baseline to 173 μg/L two years later, and further declined to 139 μg/L over 8 years. For comparison, urinary As concentrations for participants drinking from wells with ≤10 μg/L As remained close to 50 μg/L throughout. Whereas the interventions only partially reduced exposure, well status with respect to As was predictive of well-switching decisions for at least a decade after the initial testing. Participants with high-As wells were 7 times more likely to switch wells over the first two years and 1.4-1.8 times more likely to switch wells over the ensuing decade.ConclusionsArsenic exposure gradually declined following blanket well testing, an education campaign, and the installation of community wells but remained almost three times higher than for a subgroup of the participants drinking from wells with ≤10 μg/L. In addition, the number of participants with unknown As concentrations in their primary household wells increased substantially over time, indicating the importance of additional well testing as new wells continue to be installed, in addition to other means of reducing As exposure.

Dataset Information

Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh.

Publications

Mobilization of arsenic during one-year incubations of grey aquifer sands from Araihazar, Bangladesh.

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