Estimating anaerobic reductive dechlorination of chlorinated compounds in groundwater by indigenous microorganisms

Tetrachloroethylene (PCE) and trichloroethylene (TCE), critical pollutants to human health and groundwater ecosystems, are managed by groundwater quality standards (GQS) in South Korea. However, there are no GQSs for their by-products, such as cis-dichloroethylene (DCE) and vinyl chloride (VC) produced through the dechlorination process of PCE and TCE. Therefore, in this study, we monitored PCE, TCE, cis-DCE, and VC in 111 national groundwater wells for three years (2016 to 2018) to evaluate their distributions, a biological dechlorination possibility, and human risk assessment. The detection frequency of them was 30.2% for PCE, 45.1% for TCE, 43.9% for cis-DCE and 13.4% for VC. The four chlorinated compounds were commonly detected in 21 out of 111 wells. In the results of statistical analysis with 21 wells data, DO and ORP also had a negative correlation with four organic chlorinated compounds, while EC and sulfate has a positive correlation with the compounds. This indicates that the 21 wells were relatively met with suitable environments for a biological dechlorination reaction compared to the other wells. Finally, cis-DCE had a non-carcinogenic risk of 10(-1) and the carcinogenic risk of VC was 10' or higher. Through this study, the distribution status of the four chlorinated compounds in groundwater in South Korea and the necessity of preparing plans to manage cis-DCE and VC were confirmed.

Automated summary

This study monitored the distribution of several chlorinated compounds in groundwater in South Korea, including PCE, TCE, cis-DCE, and VC. Statistical analysis revealed correlations between these compounds and dissolved oxygen, oxidation-reduction potential, electrical conductivity, and sulfate concentration in certain wells, indicating suitable conditions for biological dechlorination. Furthermore, the study evaluated the non-carcinogenic and carcinogenic risks of cis-DCE and VC, with cis-DCE posing a non-carcinogenic risk and VC having a high carcinogenic risk.