Delineating sources of groundwater recharge in an arsenic-affected Holocene aquifer in Cambodia using stable isotope-based mixing models

Richards, L. A., Magnone, D., Boyce, A. J. , Casanueva-Marenco, M. J., van Dongen, B. E., Ballentine, C. J. and Polya, D. A. (2018) Delineating sources of groundwater recharge in an arsenic-affected Holocene aquifer in Cambodia using stable isotope-based mixing models. Journal of Hydrology, 557, pp. 321-334. (doi: 10.1016/j.jhydrol.2017.12.012)

Abstract

Chronic exposure to arsenic (As) through the consumption of contaminated groundwaters is a major threat to public health in South and Southeast Asia. The source of As-affected groundwaters is important to the fundamental understanding of the controls on As mobilization and subsequent transport throughout shallow aquifers. Using the stable isotopes of hydrogen and oxygen, the source of groundwater and the interactions between various water bodies were investigated in Cambodia’s Kandal Province, an area which is heavily affected by As and typical of many circum-Himalayan shallow aquifers. Two-point mixing models based on δD and δ18O allowed the relative extent of evaporation of groundwater sources to be estimated and allowed various water bodies to be broadly distinguished within the aquifer system. Model limitations are discussed, including the spatial and temporal variation in end member compositions. The conservative tracer Cl/Br is used to further discriminate between groundwater bodies. The stable isotopic signatures of groundwaters containing high As and/or high dissolved organic carbon plot both near the local meteoric water line and near more evaporative lines. The varying degrees of evaporation of high As groundwater sources are indicative of differing recharge contributions (and thus indirectly inferred associated organic matter contributions). The presence of high As groundwaters with recharge derived from both local precipitation and relatively evaporated surface water sources, such as ponds or flooded wetlands, are consistent with (but do not provide direct evidence for) models of a potential dual role of surface-derived and sedimentary organic matter in As mobilization.

• Item Type: Articles
• Additional Information: This research was funded by a NERC Standard Research Grant (NE/J023833/1) to DP, BvD and CB, a NERC PhD studentship (NE/L501591/1) to DM and a Leverhulme Trust Early Career Fellowship (ECF2015-657) to LR. Stable isotope analysis was supported by a NERC Isotope Geosciences Facilities award (IP-1505-1114).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boyce, Professor Adrian
• Authors: Richards, L. A., Magnone, D., Boyce, A. J., Casanueva-Marenco, M. J., van Dongen, B. E., Ballentine, C. J., and Polya, D. A.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of Hydrology
• Publisher: Elsevier
• ISSN: 0022-1694
• ISSN (Online): 1879-2707
• Published Online: 06 December 2017
• Copyright Holders: Copyright © 2017 Elsevier B.V.
• First Published: First published in Journal of Hydrology 557:321-334
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher