Preliminary study on natural attenuation of BTEX monitoring in an organic pollution control site

Benzene series compounds (BTEX) are widely utilized in the chemical industries, and their high mobility and diffusion potential in groundwater pose a significant threat to the groundwater environment. Monitored natural attenuation (MNA) remediation technology is highly recommended for groundwater remediation due to its cost-effectiveness and low environmental impact. Currently, the application of MNA technology to remediate organically contaminated sites in China is still in its nascent stages, with few documented engineering cases. In this study, BTEX in the groundwater of a decommissioned organic chemical plant site was taken as the target pollutant. Continuous field monitoring was conducted following a significant reduction in pollutant concentration from a previous groundwater extraction engineering. This revealed the natural attenuation law of BTEX. The results revealed severe BTEX contamination in the study area, with concentrations ranging from 0.004 to 129.114 mg·L−1 and an average concentration of 2.635 mg·L−1. The concentration of BTEX showed a fluctuation decreasing trend with time. Further analysis indicated a significant negative correlation between BTEX concentrations and oxidation-reduction potential (ORP). Additionally, the presence of abundant sulfate-reducing bacteria in the groundwater suggests that BTEX biodegradation occurred. The attenuation rate of BTEX ranged from 0.0032 d−1 to 0.0067 d−1, and the half-life is 148—286 d. This study provides theoretical support for the subsequent MNA remediation of the site.