Investigating Fluorescent Organic-Matter Composition as a Key Predictor for Arsenic Mobility in Groundwater Aquifers

Abstract

Dissolved organic matter (DOM) is linked to the heterogeneous distribution of elevated arsenic (As) in groundwater used for drinking and irrigation purposes, but the relationship between DOM characteristics and arsenic mobility has yet to be fully understood. Here, DOM from groundwater sampled in the Bengal Basin region was characterized using both conventional bulk emission-excitation (EEM) spectroscopy and high-performance size exclusion chromatography coupled to spectroscopy (HPSEC-EEM). Notably, application of the novel HPSEC-EEM approach permitted the total fluorescence of individual samples to be independently resolved into its underlying components. This allowed the external validation of the bulk-sample fluorescence decomposition and offered insight into the molecular size distribution of fluorescent DOM. Molecular size distributions were similar for the UVA fluorescent (C 310 , C 340) as well as the three visible fluorescent (C 390 , C 440 C 500) components. There was a greater visible fluorescence in shallow aquifer samples (10-33 m) with high As (SH, up to 418µg/L) than in samples from the same depth with lower As (up to 40µg/L). This indicated a link between DOM quality and As mobility within the shallow aquifer. The deep aquifer samples (170-200 m) revealed DOM characteristics similar to SH samples but had low As concentrations (<4µg/L), signifying that the deep aquifer is potentially vulnerable to As contamination. These findings pave the way for a more comprehensive assessment of the susceptibility of drinking water aquifers, thereby supporting the management of groundwater resources.

Iron oxide xerogels for improved water quality monitoring of arsenic(iii) in resource-limited environmentsviasolid-phase extraction, preservation, storage, transportation, and analysis of trace contaminants (SEPSTAT)

“…50,51 Alternatively, species conversion could be implemented during adsorption by incorporating additional materials capable of facilitating arsenic oxidation or reduction, such as manganese oxides 28 or zerovalent iron, 52 respectively, into iron oxide xerogel-based sorbents. Additional areas for future work include investigation of adsorption and recovery kinetics in order to fully develop protocols for use during water monitoring; 14 investigation of adsorption and recovery for sample matrices incorporating organic matter; 27,[53][54][55] development of compact devices for adsorption, transportation, and recovery; 14 and stakeholder engagement in order to better understand use cases and design priorities for implementation of the SEPSTAT paradigm. 56…”

Model-Based Interpretation of Groundwater Arsenic Mobility during in Situ Reductive Transformation of Ferrihydrite

“…The duration of the lag phase preceding the reductive microbial dissolution of ferrihydrite (i.e., t i, ferri ) was found to vary among the wells (Table SI6). This difference could suggest spatial heterogeneity of this reaction in the field (20,80). Interestingly, the observed lag phase increases along the selected flow line (i.e.…”

Effects of pH on arsenic mineralogy and stability in Poldice Valley, Cornwall, United Kingdom

“…Arsenic is similar to many chalcophile elements in that it is commonly released by sulphide oxidation. Arsenic is modified by various biogeochemical processes, and attenuated by adsorption and co-precipitation with Fe-minerals, clays, and organic matter (Wen, et al, 2020;Schittich, et al, 2018;Bauer & Blodau, 2006;Redman, Macalady, & Ahmann, 2002;Kalbitz & Wennrich, 1998;Wang & Mulligan, 2006;Pallier, Feuillade-Cathalifaud, Serpaud, & Bollinger, 2010;Dobran & Zagury, 2006). It is a non-metal/metalloid and is a member of the Group VB elements (P, As, Sb, Bi)…”