Journal article
Arsenic mobilization in an alluvial aquifer of the Terai region, Nepal
Journal of Hydrology
2014
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Abstract
<p><h4 id="x-x-absSec_1">Study Region</h4> <p id="x-x-spar0005">A shallow (<50 m) alluvial aquifer in the Terai region of Nepal. <h4 id="x-x-absSec_2">Study Focus</h4> <p id="x-x-spar0010">We examine the hydrogeochemical characteristics of a shallow alluvial aquifer system in the Terai region (Nawalparasi district) to identify possible mechanisms and controls on geogenic As mobilization in groundwater. Groundwater and river water samples from a topo-gradient flow-path and floodplain of a minor river draining the Siwalik forehills were analyzed for physico-chemical parameters. <h4 id="x-x-absSec_3">New Hydrological Insights for the Region</h4> <p id="x-x-spar0015">The aquifer is characterized by Ca-HCO<sub>3</sub> type water and is multi-contaminated, with the WHO guideline values exceeded for As, Mn and F in 80%, 70% and 40% of cases respectively. The middle portion of the floodplain was heavily contaminated with As, predominantly as As(III). The river water displayed some evidence of reductive processes in the hyporheic zone contributing As, Fe and Mn to baseflow and also had elevated fluoride. The generally sub-oxic conditions, dominance of As(III) and Fe<sup>2+</sup> species and positive correlation between As and both NH<sub>3</sub> and UV-absorbance at 254 nm suggests that oxidation of organic matter coupled with microbial mediated reductive processes are important for mobilizing As in the aquifer. The apparent decoupling between As(III)<sub>(aq)</sub> and Fe<sup>2+</sup><sub>(aq)</sub> may be explained by precipitation of siderite, but further work is required to resolve this unambiguously. Along with reductive processes, other geochemical mechanisms including silicate weathering and precipitation/dissolution of carbonate minerals, control the solute and major ion composition of groundwater.</p>
Details
- Title
- Arsenic mobilization in an alluvial aquifer of the Terai region, Nepal
- Creators
- Jasmine Diwakar - Southern Cross UniversityScott G Johnston - Southern Cross UniversityEdward D Burton - Southern Cross UniversitySuresh Das Shrestha - Tribhuvan University
- Publication Details
- Journal of Hydrology
- Identifiers
- 1375; 991012822163702368
- Academic Unit
- Southern Cross GeoScience; Faculty of Science and Engineering; Science
- Resource Type
- Journal article