Large-scale arsenic mobilization from legacy sources in anoxic aquifers: Multiple methods and multi-decadal perspectives.

Autor: Cao F; Department of Physical Geography, Bolin Center for Climate Research, Stockholm University, SE-106 91 Stockholm, Sweden. Electronic address: feifei.cao@natgeo.su.se., Kleja DB; Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), Box 7014, SE-750 07 Uppsala, Sweden; Swedish Geotechnical Institute (SGI), SE-581 93 Linköping, Sweden., Tiberg C; Swedish Geotechnical Institute (SGI), SE-581 93 Linköping, Sweden., Jarsjö J; Department of Physical Geography, Bolin Center for Climate Research, Stockholm University, SE-106 91 Stockholm, Sweden.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2023 Sep 20; Vol. 892, pp. 164565. Date of Electronic Publication: 2023 Jun 02.
DOI: 10.1016/j.scitotenv.2023.164565
Abstrakt: While geogenic arsenic (As) contamination of aquifers have been intensively investigated across the world, the mobilization and transport of As from anthropogenic sources have received less scientific attention, despite emerging evidence of poor performance of widely used risk assessment models. In this study we hypothesize that such poor model performance is largely due to insufficient attention to heterogeneous subsurface properties, including the hydraulic conductivity K and the solid-liquid partition (K d ), as well as neglect of laboratory-to-field scaling effects. Our multi-method investigation includes i) inverse transport modelling, ii) in-situ measurements of As concentrations in paired samples of soil and groundwater, and iii) batch equilibrium experiments combined with (iv) geochemical modelling. As case study we use a unique 20-year series of spatially distributed monitoring data, capturing an expanding As plume in a Chromated Copper Arsenate (CCA)-contaminated anoxic aquifer in southern Sweden. The in-situ results showed a high variability in local K d values of As (1 to 107 L kg -1 ), implying that over-reliance of data from only one or few locations can lead to interpretations that are inconsistent with field-scale As transport. However, the geometric mean of the local K d values (14.4 L kg -1 ) showed high consistency with the independently estimated field-scale "effective K d " derived from inverse transport modelling (13.6 L kg -1 ). This provides empirical evidence for the relevance of using geometric averaging when estimating large-scale "effective K d " values from local measurements within highly heterogenous, isotropic aquifers. Overall, the considered As plume is prolonged by about 0.7 m year -1 , now starting to extend beyond the borders of the industrial source area, a problem likely shared with many of the world's As-polluted sites. In this context, geochemical modelling assessments, as presented here, provided a unique understanding of the processes governing As retention, including local variability in, e.g., Fe/Al-(hydr)oxides contents, redox potential and pH.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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