Vertical geochemical variations and arsenic mobilization in the shallow alluvial aquifers of the Chapai-Nawabganj District, northwestern Bangladesh: implication of siderite precipitation

Reza, A. H. M. Selim and Jean, Jiin-Shuh and Bundschuh, Jochen and Liu, Chia-Chuan and Yang, Huai-Jen and Lee, Chi-Yu (2013) Vertical geochemical variations and arsenic mobilization in the shallow alluvial aquifers of the Chapai-Nawabganj District, northwestern Bangladesh: implication of siderite precipitation. Environmental Earth Sciences, 68 (5). pp. 1255-1270. ISSN 1866-6280

Abstract

Core sediments from three disturbed boreholes JOR, GHAT, and RAJ) and two undisturbed boreholes (DW1 and DW2) were collected in the study area of the Chapai-Nawabganj district of northwestern Bangladesh for geochemical analyses. In the study area, groundwater samples from fourteen As-contained private wells and five nested piezometers at both the DW1 and DW2 boreholes were also collected and analyzed. The groundwater arsenic concentrations in the uppermost aquifer (10–40 m of depth) range from 3 to 315 lg/L (mean 47.73 ± 73.41 lg/L), while the arsenic content in sediments range from 2 to 14 mg/kg (mean 4.36 ± 3.34 mg/kg). An environmental scanning electron microscope (ESEM) with an energy dispersive X-ray spectrometer was used to investigate the presence of major and trace elements in the sediments.
Groundwaters in the study area are generally the Ca–HCO3
type with high concentrations of As, but low levels of Fe,
Mn, NO3 - and SO4 -2. The concentrations of As, Fe, Mn
decrease with depth in the groundwater, showing vertical
geochemical variations in the study area. Statistical analysis clearly shows that As is closely associated with Fe and Mn in the sediments of the JOR core (r = 0.87, p\0.05
for Fe and r = 0.78, p\0.05 for Mn) and GHAT core (r = 0.95, p\0.05 for Fe and r = 0.93, p\0.05 for Mn), while As is not correlated with Fe and Mn in groundwater.
The comparatively low Fe and Mn concentrations in some
groundwater and the ESEM image revealed that siderite
precipitated as a secondary mineral on the surface of the
sediment particles. The correlations along with results of
sequential extraction experiments indicated that reductive
dissolution of FeOOH and MnOOH represents a mechanism for releasing arsenic into the groundwater.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2012 Springer-Verlag. Published online: 7 August 2012. Published version deposited in accordance with the copyright policy of the publisher.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - No Department
Date Deposited: 28 Nov 2013 01:35
Last Modified: 23 Oct 2014 23:52
Uncontrolled Keywords: northwestern Bangladesh; arsenic mobilization; siderite precipitation; alluvial aquifers; geochemical variations
Fields of Research : 04 Earth Sciences > 0402 Geochemistry > 040202 Inorganic Geochemistry
04 Earth Sciences > 0403 Geology > 040310 Sedimentology
09 Engineering > 0905 Civil Engineering > 090509 Water Resources Engineering
Socio-Economic Objective: D Environment > 96 Environment > 9609 Land and Water Management > 960905 Farmland, Arable Cropland and Permanent Cropland Water Management
Identification Number or DOI: 10.1007/s12665-012-1825-6
URI: http://eprints.usq.edu.au/id/eprint/22335

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