title: Abiotic degradation of methyl parathion by manganese dioxide: Kinetics and transformation pathway.
abstract: Methyl parathion, a widely used insecticide around the world, has aroused gradually extensive concern of researchers due to its degradation product such as methyl paraoxon, with higher toxicity for mammals and more recalcitrant. Given the ubiquity of manganese dioxide (MnO2) in soils and aquatic sediments, the abiotic degradation of methyl parathion by α-MnO2 was investigated in batch experiments. It was found that methyl parathion was decomposed up to 90% by α-MnO2 in 30 h and the removal efficiency of methyl parathion depended strongly on the loading of α-MnO2 and pH value in the solution where the reactions followed pseudo-first-order model well. The coexisting metal ions (such as Ca(2+), Mg(2+) and Mn(2+)) weakened markedly the degradation of methyl parathion by α-MnO2. However, the effect of dissolved organic matter (HA-Na) on reaction rates presented two sides: to improve hydrolysis rate but deteriorate oxidation rate of methyl parathion. Based on the degradation products identified by gas chromatography-mass spectrometer (GC/MS) and liquid chromatography high-resolution mass spectrometer (LC/HRMS), both hydrolysis and oxidation processes were proposed to be two predominant reaction mechanisms contributing to methyl parathion degradation by α-MnO2. This study provided meaningful information to elucidate the abiotic dissipation of methyl parathion by manganese oxide minerals in the environment.
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: Yuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Yinwen
authors.initials: Y
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Sisi
authors.initials: S
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Songhu
authors.initials: S
authors.lastname: Yuan
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Zhenli
authors.initials: Z
authors.lastname: Zhu
mesh_terms: D000818:Animals; D004785:Environmental Pollutants / Q000032:analysis* / Q000737:chemistry; D052918:Environmental Restoration and Remediation; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007306:Insecticides / Q000032:analysis* / Q000737:chemistry; D007700:Kinetics; D017895:Manganese Compounds / Q000737:chemistry*; D008743:Methyl Parathion / Q000032:analysis* / Q000737:chemistry; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*
chemical_list: D004785:Environmental Pollutants; D007306:Insecticides; D017895:Manganese Compounds; D010087:Oxides; D008743:Methyl Parathion; C016552:manganese dioxide
keywords: Abiotic degradation; Manganese dioxide; Methyl parathion; Transformation pathway