title: The abiotic degradation of methyl parathion in anoxic sulfur-containing system mediated by natural organic matter.
abstract: Although the kinetics and transformation of methyl parathion have been investigated extensively, its abiotic degradation mechanism in anoxic sulfur-containing groundwater system is still not clear. In this work, the abiotic degradation of methyl parathion in anoxic sulfur-containing system mediated by natural organic matter (NOM) was investigated in batch experiments. It was found that the removal of methyl parathion (up to 80.7%) was greatly improved in sulfide containing NOM compared to those in sulfide alone (with 15.5%) and in NOM alone (almost negligible). Various sulfur species presented significant differences in behaviors methyl parathion degradation, but followed by the pseudo-first-order model well. No facilitated degradation of methyl parathion was observed in sulfite (SO32-) or thiosulfate (S2O32-) containing NOM such as anthraquinone. Although elemental sulfur (S0) and cysteine could further improve the degradation rate of methyl parahtion, their impacts was very limited. The removal efficiency of methyl parathion in anoxic sulfur-containing system were related remarkably with NOM concentration and solution pH. Based on the transformation products identified by gas chromatography-mass spectrometer (GC/MS) and liquid chromatography high resolution mass spectrometer (LC/HRMS), both the nitro group reduction and hydrolysis (SN@C) processes by sulfide (HS-) were further proved to be two predominant reaction mechanisms for the abiotic degradation of methyl parathion in anoxic sulfur-containing system. The results of this study help to understand the natural attenuation of methyl parathion under anoxic sulfide-containing groundwater system mediated by NOM.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Liao
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China. Electronic address: caixiangzhang@yahoo.com.
authors.forename: Caixiang
authors.initials: C
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Mi
authors.initials: M
authors.lastname: Tang
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D006812:Humic Substances / Q000032:analysis*; D006868:Hydrolysis; D007700:Kinetics; D008743:Methyl Parathion / Q000032:analysis*; D008962:Models, Theoretical; D012996:Solutions; D013440:Sulfides / Q000737:chemistry; D013447:Sulfites / Q000737:chemistry; D013457:Sulfur Compounds / Q000737:chemistry*; D013885:Thiosulfates / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006812:Humic Substances; D012996:Solutions; D013440:Sulfides; D013447:Sulfites; D013457:Sulfur Compounds; D013885:Thiosulfates; D014874:Water Pollutants, Chemical; D008743:Methyl Parathion
keywords: Methyl parathion; NOM; Reduced sulfur species; Transformation pathway