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Two-stage chromium isotope fractionation during microbial Cr(VI) reduction
被引:49
|作者:
Chen, Guojun
[1
]
Han, Juncheng
[2
]
Mu, Yang
[2
]
Yu, Huimin
[1
]
Qin, Liping
[1
,3
]
机构:
[1] Univ Sci & Technol China, Sch Earth & Space Sci, CAS Key Lab Crust Mantle Mat & Environm, Hefei 230026, Anhui, Peoples R China
[2] Univ Sci & Technol China, Dept Chem, CAS Key Lab Urban Pollutant Convers, Hefei 230026, Anhui, Peoples R China
[3] Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing, Peoples R China
来源:
基金:
中国国家自然科学基金;
关键词:
Microbial Cr(VI) reduction;
Chromium isotope fractionation;
The values of epsilon;
Bioavailability;
Mass-transfer limitations;
SHEWANELLA-ONEIDENSIS MR-1;
MASS-DEPENDENT FRACTIONATION;
HEXAVALENT CHROMIUM;
BIOAVAILABILITY RESTRICTIONS;
BACTERIAL REDUCTION;
SULFATE REDUCTION;
IRON;
DEGRADATION;
CHROMATE;
TEMPERATURE;
D O I:
10.1016/j.watres.2018.09.034
中图分类号:
X [环境科学、安全科学];
学科分类号:
08 ;
0830 ;
摘要:
Chromium isotope fractionation analysis is a promising approach for the assessment of microbial Cr(VI) reduction in groundwater. Understanding the mechanisms and other parameters that control Cr isotope fractionation factors (between the product Cr(III) and reactant Cr (VI)) in microbial Cr(VI) reduction is critical to this application. To date, such studies are very limited. Here, the influence of critical factors on observed Cr isotope fractionation during Cr(VI) reduction by Shewanella oneidensis MR-1 under various conditions was investigated. The Cr(VI) concentration and Cr isotope ratio measurements were conducted on unreacted Cr(VI) remaining in solution to determine Cr isotope fractionation factors. The changes in ambient environmental conditions (e.g., pH, temperature) have limited influence on Cr isotope fractionation factors. However, as a result of Cr(VI) consumption as the experiments proceed, the change in bioavailability of Cr(VI) has a significant impact on Cr isotope fractionation factors. For example, in temperature-controlled experiments, Cr isotope fractionation showed two-stage behavior: during Stage I, the values of epsilon were -2.81 +/- 0.19 parts per thousand and -2.60 +/- 0.14 parts per thousand at 18 degrees C and 34 degrees C, respectively; during Stage II, as Cr(VI) reduction progressed, Cr isotope fractionation was significantly masked, and the e values decreased to -0.98 +/- 0.49 parts per thousand and 1.01 +/- 0.11 parts per thousand at 18 degrees C and 34 degrees C, respectively. Similar two stage isotope fractionation behaviors were observed in pH-controlled experiments (pH = 6.0 and 7.2) and in experiments with and without the addition of a competing electron acceptor (nitrate). Masking of isotope fractionation in Stage II indicated restrictions on the bioavailability of Cr(VI) and mass-transfer limitations. This study provides an explanation for the variation in Cr isotope fractionation factors during microbial Cr(VI) reduction in the environment, furthering the viability of Cr isotope ratio analysis as an approach in understanding Cr biogeochemical cycling. (C) 2018 Elsevier Ltd. All rights reserved.
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页码:10 / 18
页数:9
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