Hydrologic Control on Arsenic Cycling at the Groundwater–Surface Water Interface of a Tidal Channel

Historical industrial activities have resulted in soil contamination at sites globally. Many of these sites are located along coastlines, making them vulnerable to hydrologic and biogeochemical alterations due to climate change and sea-level rise. However, the impact of hydrologic dynamics on contaminant mobility in tidal environments has not been well studied. Here, we collected data from pressure transducers in wells, multi-level redox sensors, and porewater samplers at an As-contaminated site adjacent to a freshwater tidal channel. Results indicate that sharp redox gradients exist and that redox conditions vary on tidal to seasonal timescales due to sub-daily water level fluctuations in the channel and seasonal groundwater–surface water interactions. The As and Fe2+ concentrations decreased during seasonal periods of net discharge to the channel. The seasonal changes were greater than tidal variations in both Eh and As concentrations, indicating that impacts of the seasonal mechanism are stronger than those of sub-daily water table fluctuations. A conceptual model describing tidal and seasonal hydro-biogeochemical coupling is presented. These findings have broad implications for understanding the impacts of sea-level rise on the mobility of natural and anthropogenic coastal solutes.
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science and Technology, copyright © 2022 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.est.2c05930. This article will be embargoed until 01/10/2024. The Supporting Information is available free of charge at https://doi.org/10.1021/acs.est.2c05930 Remediation activities (Text S1); validation of redox probes (Text S2); XANES spectroscopy analysis (Text S3); river water chemistry (Text S4); XANES data (Table S1); As concentration fluctuation due to tides (Table S2); observed monthly trends in the water table and soil Eh (Table S3); yearly As concentration trend (Figure S1); profiles of sediment, As, and soil Eh (Figure S2); image of iron precipitation (Figure S3); thermal imagery of groundwater seepage (Figure S4); tidal fluctuation and variation of hydrochemical parameters (Figure S5); As concentration correlating with Fe2+ concentration (Figure S6); tidal fluctuation and variation of DO, DOC, NO3, and NH4 (Figure S7); hydrochemical parameters at the seasonal scales (Figure S8); and seasonal hydrologic fluctuation and soil Eh (Figure S9) (PDF)
arsenic, redox, hydrogeochemistry, groundwater−surface water interaction, tide, industrial contamination, climate action
Yu, Xuan, Joshua J. LeMonte, Junxia Li, Jason W. Stuckey, Donald L. Sparks, John G. Cargill, Christopher J. Russoniello, and Holly A. Michael. “Hydrologic Control on Arsenic Cycling at the Groundwater–Surface Water Interface of a Tidal Channel.” Environmental Science & Technology 57, no. 1 (January 10, 2023): 222–30. https://doi.org/10.1021/acs.est.2c05930.