Reaction zone evolution and remediation efficacy evaluation of in-situ biogeochemical transformation of emulsified vegetable oil-FeSO4 enhanced tetrachloroethylene-contaminated aquifers

Abstract

Enhanced in-situ biogeochemical transformation (ISBGT) has been proven effective in promoting the abiotic β-elimination of chlorinated solvents. However, the mechanisms underlying reaction zone evolution, remediation efficiency, and long-term permeability changes during the remediation process remain poorly understood. This study employed emulsified vegetable oil (EVO) and FeSO₄ as amendments to establish an in-situ reaction zone in a simulated column system. The reaction zone evolution was systematically analyzed, and the remediation efficiency and permeability variations in a PCE-contaminated aquifer were assessed. The results showed that after a single injection of EVO-FeSO₄, the reaction zone evolved through three distinct stages, including emulsified oil decomposition, microbial reduction, and β-elimination. The formation and aging mechanisms of the sulfur-iron mineral biogeobattery were also clarified. During the 300-day experimental period, the system achieved a PCE removal efficiency of 93.3%, with abiotic degradation processes contributing 96.36% of the total removal. This study provides important insights for the further development and practical application of ISBGT technology.