Assessment of hexachlorcyclohexane biodegradation in contaminated soil by compound-specific stable isotope analysis

摘要

Compound-specific isotope analysis (CSIA) was firstly applied to explore the biodegradation of hexachlorcyclohexane (HCH) isomers in contaminated soil. Concentrations and compound-specific carbon isotope ratio profiles of HCH in different specific ex-situ pilot-scale contaminated soil mesocosms were determined. The addition of nutrients and Sphingobium spp. significantly enhanced the degradation of HCH in contaminated soils within 90 days. Isomer specific biodegradation of HCHs was observed with alpha- and gamma-HCH being more degradable than beta and delta-HCH. Stable carbon isotope fractionation of HCH was observed and the delta C-13 values shifted from -28.8 +/- 0.3 parts per thousand to -24.8 +/- 0.7 parts per thousand upon 87.3% removal, -27.9 +/- 0.2 parts per thousand to -25.9 +/- 0.5 parts per thousand upon 72.8% removal, -29.4 +/- 0.3 parts per thousand to -19.9 +/- 0.6 parts per thousand upon 95.8% removal, and -27.8 +/- 0.5 parts per thousand to 23.6 +/- 0.7 parts per thousand after 96.9% removal for alpha, beta, gamma, and delta-HCH, respectively. Furthermore, the enrichment factor epsilon for alpha, beta, gamma, and delta-HCH biodegradation in soil was obtained for the first time as -2.0 parts per thousand, -1.5 parts per thousand, -3.2 parts per thousand, and -1.4 parts per thousand, which could play a critical role in assessing in situ biodegradation of HCH isomers in field site soil. Results from ex-situ pilot-scale experiments clearly demonstrated that CSIA could be a promising tool to qualitatively and quantitatively evaluate in situ biodegradation of HCH in contaminated field site. (C) 2019 Elsevier Ltd. All rights reserved.