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Impact of local recharge on arsenic concentrations in shallow aquifers inferred from the electromagnetic conductivity of soils in Araihazar, Bangladesh

Aziz, Z; Van Geen, A; Stute, M; Versteeg, R; Horneman, A; Zheng, Y; Goodbred, S; ... Ahmed, KM; + view all (2008) Impact of local recharge on arsenic concentrations in shallow aquifers inferred from the electromagnetic conductivity of soils in Araihazar, Bangladesh. Water Resources Research , 44 (7) , Article W07416. 10.1029/2007WR006000. Green open access

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Abstract

The high-degree of spatial variability of dissolved As levels in shallow aquifers of the Bengal Basin has been well documented but the underlying mechanisms remain poorly understood. We compare here As concentrations measured in groundwater pumped from 4700 wells <22 m (75 ft) deep across a 25 km2 area of Bangladesh with variations in the nature of surface soils inferred from 18,500 measurements of frequency domain electromagnetic induction. A set of 14 hand auger cores recovered from the same area indicate that a combination of grain size and the conductivity of soil water dominate the electromagnetic signal. The relationship between pairs of individual EM conductivity and dissolved As measurements within a distance of 50 m is significant but highly scattered (r2 = 0.12; n = 614). Concentrations of As tend to be lower in shallow aquifers underlying sandy soils and higher below finer-grained and high conductivity soils. Variations in EM conductivity account for nearly half the variance of the rate of increase of As concentration with depth, however, when the data are averaged over a distance of 50 m (r2 = 0.50; n = 145). The association is interpreted as an indication that groundwater recharge through permeable sandy soils prevents As concentrations from rising in shallow reducing groundwater.

Type: Article
Title: Impact of local recharge on arsenic concentrations in shallow aquifers inferred from the electromagnetic conductivity of soils in Araihazar, Bangladesh
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2007WR006000
Publisher version: http://dx.doi.org/10.1029/2007WR006000
Language: English
Additional information: Copyright 2008 by the American Geophysical Union
Keywords: Arsenic, Shallow aquifers, Spatial variability
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Inst for Risk and Disaster Reduction
URI: https://discovery.ucl.ac.uk/id/eprint/1349210
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