Effects of dissolved organic matter on pentachlorophenol reductive transformation in paddy soils

Abstract

In this study, 19 paddy soils developed from different parent materials were collected from the A (0-20 cm) horizon in Pearl River Delta basin and divided into four groups (i.e., acid sulfate soils, delta deposit, granite, and neritic deposits). Dissolved organic matter (DOM) in soils was extracted and divided into three groups according to its molecular weight, and its electron acceptance capacity (EAC) was detected using electrochemical method. Experiments were conducted in order to elucidate the role of DOM in soils in the reductive transformation of pentachlorophenol (PCP). Kinetic measurements demonstrated that PCP reduction curves fitted the microbial logistic growth equation well, and the PCP reductive transformation rate (k) was highly sensitive to the parent materials of soils. Electrochemical results confirmed that there is a significant positive relationship between the k value of PCP reductive transformation and the EAC of DOM with molecular weights of less than 3,500 and more than 14,000. The results suggest that low-molecular-weight DOM may act as electron donors, while high-molecular-weight DOM may act as electron shuttles in the reductive transformation of PCP in soils.