Biologically induced formation of realgar deposits in soil

0479104 - ÚACH 2018 RIV GB eng J - Článek v odborném periodiku
Drahota, P. - Mikutta, C. - Falteisek, L. - Duchoslav, V. - Klementová, Mariana
Biologically induced formation of realgar deposits in soil.
Geochimica et Cosmochimica Acta. Roč. 218, DEC (2017), s. 237-256. ISSN 0016-7037. E-ISSN 1872-9533
Institucionální podpora: RVO:61388980
Klíčová slova: Arsenic speciation * Microbial communities * Realgar * Sulfur isotopes * Wetland soil * X-ray absorption spectroscopy
Obor OECD: Inorganic and nuclear chemistry
Impakt faktor: 4.690, rok: 2017

The formation of realgar (As4S4) has recently been identified as a prominent As sequestration pathway in the naturally As-enriched wetland soil at the Mokrsko geochemical anomaly (Czech Republic). Here we used bulk soil and pore water analyses, synchrotron X-ray absorption spectroscopy, S isotopes, and DNA extractions to determine the distribution and speciation of As as a function of soil depth and metabolic properties of microbial communities in wetland soil profiles. Total solid-phase analyses showed that As was strongly correlated with organic matter, caused by a considerable As accumulation (up to 21 g kg(-1)) in an organic-rich soil horizon artificially buried in 1980 at a depth of similar to 80 cm. Extended X-ray absorption fine structure spectroscopy revealed that As in the buried organic horizon was predominantly present as realgar occurring as nanocrystallites (50-100 nm) in millimeter-scale deposits associated with particulate organic matter. The realgar was depleted in the S-34 isotope by 9-12.5 parts per thousand relative to the aqueous sulfate supplied to the soil, implying its biologically induced formation. Analysis of the microbial communities by 16S rDNA sequencing showed that realgar deposits formed in strictly anaerobic organic-rich domains dominated by sulfate-reducing and fermenting metabolisms. In contrast, realgar deposits were not observed in similar domains with even small contributions of oxidative metabolisms. No association of realgar with specific microbial species was observed. Our investigation shows that strongly reducing microenvironments associated with buried organic matter are significant biogeochemical traps for As, with an estimated As accumulation rate of 61 g As m(-2) yr(-1). Nevertheless the production of biologically induced realgar in these microenvironments is too slow to lower As groundwater concentrations at our field site (similar to 6790 mg L-1).
Trvalý link: http://hdl.handle.net/11104/0275122