title: Dechlorination of chloroacetanilide herbicides by plant growth regulator sodium bisulfite.
abstract: Chloroacetanilide herbicides are frequently detected in groundwater and surface waters, and pose high risks to aquatic biota. In this study, sodium bisulfite (NaHSO(3)), a plant growth regulator used in China, was used to remove three chloroacetanilide herbicides including alachlor, acetochlor and S-metolachlor. These herbicides were rapidly dechlorinated by NaHSO(3) in neutral conditions. The dechlorination was accelerated with increasing pH, temperature and NaHSO(3) concentrations. Kinetic analysis and mass spectrum identification revealed that the reaction followed S(N)2 nucleophilic substitution, in which the chlorine was replaced by the reactive specie sulfite. Alachlor and its isomer acetochlor had similar reaction rates, whereas they were more readily transformed than S-metolachlor that had larger steric hindrance and weaker electrophilicity. The transformation products were chloroacetanilide ethane sulfonic acids (ESAs), which were also encountered as major metabolites of these herbicides in natural environment via common metabolic pathways and were less toxic to green algae compared to the parent herbicides. These results indicate that NaHSO(3) can accelerate transformation of chloroacetanilide herbicides to the less toxic transformation products by nucleophilic substitution and dechlorination in aquatic environment. NaHSO(3) can be potentially used for the removal of chloroacetanilide herbicides from wastewater effluent, spill sites and accidental discharge.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering, Department of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China. htbian@yahoo.cn
authors.forename: Haitao
authors.initials: H
authors.lastname: Bian
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
authors.forename: Xiyun
authors.initials: X
authors.lastname: Cai
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Liping
authors.initials: L
authors.lastname: Huang
authors.forename: Xianliang
authors.initials: X
authors.lastname: Qiao
authors.forename: Ce
authors.initials: C
authors.lastname: Hao
mesh_terms: D000081:Acetamides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D000476:Alkanesulfonates / Q000737:chemistry / Q000633:toxicity; D001673:Biodegradation, Environmental / Q000187:drug effects; D006207:Half-Life; D054879:Halogenation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007700:Kinetics; D013058:Mass Spectrometry; D010937:Plant Growth Regulators / Q000378:metabolism*; D044444:Scenedesmus / Q000187:drug effects; D012996:Solutions; D013447:Sulfites / Q000378:metabolism*; D013696:Temperature; D014052:Toluidines / Q000737:chemistry / Q000633:toxicity; D023382:Toxicity Tests, Acute
chemical_list: D000081:Acetamides; D000476:Alkanesulfonates; D010937:Plant Growth Regulators; D012996:Solutions; D013447:Sulfites; D014052:Toluidines; C000188:alachlor; C002634:ethane sulfonate; C078188:2-chloro-N-(ethoxymethyl)-N-(2-methyl-6-(trifluoromethyl)phenyl)acetamide; C043377:acetochlor; C009279:sodium bisulfite; C051786:metolachlor