Skip to main content
SLU publication database (SLUpub)

Research article2024Peer reviewedOpen access

Characterisation of dissolved organic matter in two contrasting arsenic-prone sites in Kandal Province, Cambodia

Moore, Oliver C.; Holt, Amy D.; Richards, Laura A.; Mckenna, Amy M.; Spencer, Robert G. M.; Lapworth, Dan J.; Polya, David A.; Lloyd, Jonathan R.; van Dongen, Bart E.

Abstract

Aquifers throughout Asia are impacted by the release of geogenic arsenic (As) into groundwater by microbial reduction of As-bearing Fe(III) (oxy)hydroxide minerals, severely impacting water quality. Groundwater dissolved organic matter (DOM) is likely key to As release, mainly as electron donor or electron shuttles. This study used optical analyses and ultra-high resolution mass spectrometry to examine the sources and composition of groundwater DOM in the As-prone aquifers of Kandal Province, Cambodia, at boreholes with differing host lithology (clay- and sand-dominated). Groundwater and surface water DOM composition were related to As concentrations, to infer the potential role of DOM in promoting As release. Optical and molecular-level analyses indicated an overall dominance of terrestrial-derived DOM in the groundwater samples, with higher freshness index and relative abundance (RA) of aliphatic compounds in clay compared to sand-dominated lithology. Compared to surface water, groundwater DOM had relatively lower O/C ratios and nominal oxidation state of carbon (-0.19 to-0.13 compared to 0.04 for ground and surface water, respectively), with a lower %RA of aliphatic compounds and higher %RA of carboxyl-rich alicyclic molecules, suggesting microbial processing of DOM since percolation into the aquifer. Concentrations of As across both sites were negatively correlated with DOM tryptophan:fulvic-like fluorescence and the %RA of aliphatics, potentially indicating microbial degradation of biolabile DOM in connection with As release, which is consistent with its role as an electron donor source. Together these data support DOM composition as an important control on microbial mediated As release.

Keywords

Dissolved organic matter; Cambodia; Kandal Province; Optical properties; FT-ICR MS; As-cycling

Published in

Organic Geochemistry
2024, volume: 198, article number: 104886
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

SLU Authors

Global goals (SDG)

SDG6 Clean water and sanitation

UKÄ Subject classification

Geochemistry

Publication identifier

  • DOI: https://doi.org/10.1016/j.orggeochem.2024.104886

Permanent link to this page (URI)

https://res.slu.se/id/publ/139430