title: Nucleophilic substitution as a mechanism of atrazine sequestration in soil.
abstract: Formation of nonextractable residue was widely observed as a sink of atrazine (ATZ) in soil. However, the mechanisms by which ATZ binds to soil organic matter remain unclear. In this study, we demonstrated that neucleophilic substitution could serve an important pathway causing ATZ sequestration. The carbon bonded to the chlorine in ATZ molecule is partially positively charged due to the strong electronegativity of chlorine and is susceptible to the attack of nucleophiles such as aniline. Since aromatic amines are relatively rare in natural soils, amino acids/peptides were hypothesized to act as the main nucleophiles in real environment. However, substantially ATZ transformation was only observed in the presence of those species containing thiol functionality. Thus, we speculated that it was the thiol group in amino acids/peptides acting as the nucleophile. Nitrogen in amino acids was in fact not an active nucleophile toward ATZ. In addition to the sulfur-containing amino acids, other thiol compounds, and sulfide were also proved to be reactive to ATZ. Thus, the sequestration potential of ATZ probably correlates to the availability of thiol compounds in soil.
authors.affiliation: Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China. Electronic address: jhlu@njau.edu.cn.
authors.forename: Junhe
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Environmental Science and Engineering, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Shao
authors.affiliation: Nanjing Institute of Environmental Science, Ministry of Environmental Protection of PRC, Nanjing 210042, China.
authors.forename: Deyang
authors.initials: D
authors.lastname: Kong
mesh_terms: D000588:Amines / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D001280:Atrazine / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D004785:Environmental Pollutants / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry*; D013058:Mass Spectrometry; D009584:Nitrogen / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry*; D055601:Organic Chemistry Phenomena; D010455:Peptides / Q000737:chemistry; D012987:Soil; D012989:Soil Pollutants / Q000032:analysis*; D013455:Sulfur / Q000737:chemistry
chemical_list: D000588:Amines; D000596:Amino Acids; D004785:Environmental Pollutants; D006540:Herbicides; D009930:Organic Chemicals; D010455:Peptides; D012987:Soil; D012989:Soil Pollutants; D013455:Sulfur; D002244:Carbon; D009584:Nitrogen; D001280:Atrazine
keywords: Atrazine; Bound residue; Nucleophic substitution; Sequestration