First Insight into the Mobilization and Sequestration of Arsenic in a Karstic Soil during Redox Changes
Journal
Environmental Science & Technology
Journal Volume
58
Journal Issue
40
Start Page
17850
End Page
17861
ISSN
0013936X
Date Issued
2024-10-08
Author(s)
Jianxu Wang
Sabry M. Shaheen
Ann-Christin Swertz
Chengshuai Liu
Christopher W.N. Anderson
Scott Fendorf
Xinbin Feng
Jörg Rinklebe
Abstract
Karst terrains provide drinking water for about 25% of the people on our planet, particularly in the southwest of China. Pollutants such as arsenic (As) in the soil can infiltrate groundwater through sinkholes and bedrock fractures in karst terrains. Despite this, the underlying mechanisms responsible for As release from karst soils under redox changes remain largely unexplored. Here, we used multiple synchrotron-based spectroscopic analyses to explore As mobilization and sequestration in As-polluted karstic soil under biogeochemical conditions that mimic field-validated redox conditions. We observed that As in the soil exists primarily as As(V), which is mainly associated with Fe(oxyhydr)oxides. The concentration of the dissolved As was high (294 μM) and As(III) was dominant (∼95%) at low Eh (≤−100 mV), indicating the high risk of As leaching under reducing conditions. This As mobilization was attributed to the fact that the dissolution of ferrihydrite and calcite promoted the release and reduction of associated As(V). The concentration of the dissolved As was low (17.0 μM) and As(V) was dominant (∼68%) at high Eh (≥+100 mV), which might be due to the oxidation and/or sequestration of As(III) by the recrystallized ferric phase. Our results showed that the combined effects of the reductive release of As(V) from both ferric and nonferric phases, along with the recrystallization of the ferric phase, govern the redox-induced mobilization and potential leaching of As in soils within karst environments.
Subjects
arsenic mobilization
biogeochemical microcosms
dissimilatory reduction
reducing-oxidation reactions
Publisher
American Chemical Society
Type
journal article