Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier.
We assessed the potential of zerovalent-iron- (Fe(0)) based permeable reactive barrier (PRB) systems for arsenic (As) remediation in the presence or absence of microbial sulfate reduction. We conducted long-term (200 day) flow-through column experiments to investigate the mechanisms of As transformation and mobility in aquifer sediment (in particular, the PRB downstream linkage). Changes in As speciation in the aqueous phase were monitored continuously. Speciation in the solid phase was determined at the end of the experiment using X-ray absorption near-edge structure (XANES) spectroscopy analysis. We identified thio-As species in solution and AsS in solid phase, which suggests that the As(V) was reduced to As(III) and precipitated as AsS under sulfate-reducing conditions and remained as As(V) under abiotic conditions, even with low redox potential and high Fe(II) content (4.5 mM). Our results suggest that the microbial sulfate reduction plays a key role in the mobilization of As from Fe-rich aquifer sediment under anoxic conditions. Furthermore, they illustrate that the upstream-downstream linkage of PRB affects the speciation and mobility of As in downstream aquifer sediment, where up to 47% of total As initially present in the sediment was leached out in the form of mobile thio-As species.
BRGM , French Geological Survey, Laboratory Division and ‡Water Environment and Ecotechnology Division, 3 av. Claude Guillemin, 45060 Orléans cedex 02, France.|CEREGE, CNRS-Aix Marseille University - IRD - Collège de France, UM-34 , 13545 Aix-en-Provence, France.
Naresh
N
Kumar
Norwegian Institute for Water Research-NIVA , Gaustadalléen 21, 0349 Oslo, Norway.|Ecohydrology Group, University of Waterloo , 200 University Avenue, Waterloo, Ontario, N2L 3G1 Canada.
Raoul-Marie
RM
Couture
BRGM , French Geological Survey, Laboratory Division and ‡Water Environment and Ecotechnology Division, 3 av. Claude Guillemin, 45060 Orléans cedex 02, France.
Romain
R
Millot
Fabienne
F
Battaglia-Brunet
CEREGE, CNRS-Aix Marseille University - IRD - Collège de France, UM-34 , 13545 Aix-en-Provence, France.
Jérôme
J
Rose
D001151:Arsenic / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry; D014965:X-Rays
D013431:Sulfates; D007501:Iron; D001151:Arsenic