Elevated As concentrations in groundwater of the Huhhot basin (HB), Inner Mongolia, China, and the western Bengal basin (WBB), India, have been known for decades. However, few studies have been performed to comprehend the processes controlling overall groundwater chemistry in the HB. In this study, the controls on solute chemistry in the HB have been interpreted and compared with the well-studied WBB, which has a very different climate, physiography, lithology, and aquifer characteristics than the HB. In general, there are marked differences in solute chemistry between HB and WBB groundwaters. Stable isotopic signatures indicate meteoric recharge in the HB in a colder climate, distant from the source of moisture, in comparison to the warm, humid WBB. The major-ion composition of the moderately reducing HB groundwater is dominated by a mixed-ion (Ca-Na-HCO3-Cl) hydrochemical facies with an evolutionary trend along the regional hydraulic gradient. Molar ratios and thermodynamic calculations show that HB groundwater has not been affected by cation exchange, but is dominated by weathering of feldspars (allitization) and equilibrium with gibbsite and anorthite. Mineral weathering and mobilization of As could occur as recharging water flows through fractured, argillaceous, metamorphic or volcanic rocks in the adjoining mountain-front areas, and deposits solutes near the center of the basin. In contrast, WBB groundwater is Ca-HCO3-dominated, indicative of calcite weathering, with some cation exchange and silicate weathering (monosiallitization).
|Number of pages||17|
|State||Published - Oct 2009|
Bibliographical noteFunding Information:
We acknowledge the Swedish International Development Cooperation Agency (Sida-SAREC) for providing financial support (SWE-2000-182) and the Swedish Research Council (VR-Sida), Strategic Environmental Research Foundation (MISTRA), Geological Society of America and University of Kentucky for research grants on the studies of high As groundwaters in the Huhhot and western Bengal basins. FS acknowledges Sigrun Santesson (International Programmes Office, KTH) and Sida for a Minor Field Studies (MFS) scholarship in support of field studies in PR China during October-November 2003. We thank Ann Fylkner and Monica Löwen (Department of Land and Water Resources Engineering, KTH, Stockholm), Carl-Magnus Mörth (Department of Geology and Geochemistry, Stockholm University), Tricia Coakley and John May (Environmental Research and Training Laboratory, University of Kentucky), and Dr. Chris Eastoe (University of Arizona) for sample analyses. We also appreciate the support rendered by the officials of the Directorate of Public Health Engineering, Government of West Bengal, and the advice of Drs. Bridget Scanlon and John Gates (University of Texas at Austin). We thank Dr. Ashok Ghosh and two anonymous reviewers for their constructive review comments, and Dr. Dave Polya and Dr. Ron Fuge for efficiently handling the review process, which led to an improved manuscript.
ASJC Scopus subject areas
- Environmental Chemistry
- Geochemistry and Petrology