TY - JOUR
T1 - Arsenic speciation in arsenic-rich Brazilian soils from gold mining sites under anaerobic incubation
AU - De Mello, Jaime W.V.
AU - Talbott, Jonathan L.
AU - Scott, John
AU - Roy, William R.
AU - Stucki, Joseph W.
N1 - Funding Information:
Acknowledgments. JWVM thanks CAPES (Brazil) for fellowship funding. Laboratory and instrument facilities were funded in part by: the National Science Foundation, Division of Petrology and Geochemistry, Grant No. EAR 01-26308; the Natural and Accelerated Bioremediation Research (NABIR) program, Biological and Environmental Research (BER), U.S. Department of Energy Grant No. DE-FG02-00ER62986); the International Arid Lands Consortium, Grant No.03R-15; the University of Illinois Waste Management and Research Center; and the Illinois State Geological Survey.
PY - 2007/9
Y1 - 2007/9
N2 - Background. Arsenic speciation in environmental samples is essential for studying toxicity, mobility and bio-transformation of As in aquatic and terrestrial environments. Although the inorganic species As(III) and As(V) have been considered dominant in soils and sediments, organisms are able to metabolize inorganic forms of arsenic into organo-arsenic compounds. Arsenosugars and methylated As compounds can be found in terrestrial organisms, but they generally occur only as minor constituents. We investigated the dynamics of arsenic species under anaerobic conditions in soils surrounding gold mining areas from Minas Gerais State, Brazil to elucidate the arsenic biogeochemical cycle and water contamination mechanisms. Methods. Surface soil samples were collected at those sites, namely Paracatu Formation, Banded Iron Formation and Riacho dos Machados Sequence, and incubated in CaCl2 2.5 mmol L-1 suspensions under anaerobic conditions for 1, 28, 56 and 112 days. After that, suspensions were centrifuged and supernatants analyzed for soluble As species by IC-ICPMS and HPLC-ICPMS. Results. Easily exchangeable As was mainly arsenite, except when reducible manganese was present. Arsenate was mainly responsible for the increase in soluble arsenic due to the reductive dissolution of either iron or manganese in samples from the Paracatu Formation and Riacho dos Machados Sequence. On the other hand, organic species of As dominated in samples from the Banded Iron Formation during anaerobic incubation. Discussion. Results are contrary to the expectation that, in anaerobic environments, As release due to the reductive dissolution of Fe is followed by As(V) reduction to As(III). The occurrence of organo-arsenic species was also found to be significant to the dynamics of soluble arsenic, mainly in soils from the Banded Iron Formation (BIF), under our experimental conditions. Conclusions. In general, As(V) and organic As were the dominant species in solution, which is surprising under anaerobic conditions in terrestrial environments. The unexpected occurrence of organic species of As was attributed to enrollment of ternary organic complexes or living organisms such as algae or cyanobacteria. Perspectives. These findings are believed to be useful for remediation strategies in mine-affected regions, as the organic As species are in general considered to be less toxic than inorganic ones and even As(V) is considered less mobile and toxic than As(III).
AB - Background. Arsenic speciation in environmental samples is essential for studying toxicity, mobility and bio-transformation of As in aquatic and terrestrial environments. Although the inorganic species As(III) and As(V) have been considered dominant in soils and sediments, organisms are able to metabolize inorganic forms of arsenic into organo-arsenic compounds. Arsenosugars and methylated As compounds can be found in terrestrial organisms, but they generally occur only as minor constituents. We investigated the dynamics of arsenic species under anaerobic conditions in soils surrounding gold mining areas from Minas Gerais State, Brazil to elucidate the arsenic biogeochemical cycle and water contamination mechanisms. Methods. Surface soil samples were collected at those sites, namely Paracatu Formation, Banded Iron Formation and Riacho dos Machados Sequence, and incubated in CaCl2 2.5 mmol L-1 suspensions under anaerobic conditions for 1, 28, 56 and 112 days. After that, suspensions were centrifuged and supernatants analyzed for soluble As species by IC-ICPMS and HPLC-ICPMS. Results. Easily exchangeable As was mainly arsenite, except when reducible manganese was present. Arsenate was mainly responsible for the increase in soluble arsenic due to the reductive dissolution of either iron or manganese in samples from the Paracatu Formation and Riacho dos Machados Sequence. On the other hand, organic species of As dominated in samples from the Banded Iron Formation during anaerobic incubation. Discussion. Results are contrary to the expectation that, in anaerobic environments, As release due to the reductive dissolution of Fe is followed by As(V) reduction to As(III). The occurrence of organo-arsenic species was also found to be significant to the dynamics of soluble arsenic, mainly in soils from the Banded Iron Formation (BIF), under our experimental conditions. Conclusions. In general, As(V) and organic As were the dominant species in solution, which is surprising under anaerobic conditions in terrestrial environments. The unexpected occurrence of organic species of As was attributed to enrollment of ternary organic complexes or living organisms such as algae or cyanobacteria. Perspectives. These findings are believed to be useful for remediation strategies in mine-affected regions, as the organic As species are in general considered to be less toxic than inorganic ones and even As(V) is considered less mobile and toxic than As(III).
KW - Anaerobic soils
KW - Arsenic speciation
KW - As biogeochemistry
KW - As in aquatic and terrestrial environments
KW - Biomethylation
KW - Brazil
KW - Gold mining sites
KW - Organic As
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U2 - 10.1065/espr2006.08.330
DO - 10.1065/espr2006.08.330
M3 - Article
C2 - 17993222
AN - SCOPUS:35548978593
SN - 0944-1344
VL - 14
SP - 388
EP - 396
JO - Environmental Science and Pollution Research
JF - Environmental Science and Pollution Research
IS - 6
ER -