Sulfur and oxygen isotope tracing in zero valent iron based In situ remediation system for metal contaminants

摘要

In the present study, controlled laboratory column experiments were conducted to understand the bio-geochemical changes during the microbial sulfate reduction. Sulfur and oxygen isotopes of sulfate were followed during sulfate reduction in zero valent iron incubated flow through columns at a constant temperature of 20 ± 1 ℃ for 90 d. Sulfur isotope signatures show considerable variation during biological sulfate reduction in our columns in comparison to abiotic columns where no changes were observed. The magnitude of the enrichment in δ~(34)S values ranged from 9.4‰ to 10.3‰. compared to initial value of 23‰, having total fractionation SS between biotic and abiotic columns as much as 6.1‰. Sulfur isotope fractionation was directly proportional to the sulfate reduction rates in the columns. Oxygen isotopes in this experiment seem less sensitive to microbial activities and more likely to be influenced by isotopic exchange with ambient water. A linear relationship is observed between δ~(34)S and δ~(18)O in biotic conditions and we also highlight a good relationship between S3AS and sulfate reduction rate in biotic columns.