title: Abiotic reduction of trifluralin and pendimethalin by sulfides in black-carbon-amended coastal sediments.
abstract: Dinitroaniline herbicides such as trifluralin and pendimethalin are persistent bioaccumulative toxins to aquatic organisms. Thus, in-situ remediation of contaminated sediments is desired. This study investigated whether black carbons (BCs), including apple wood charcoal (BC1), rice straw biochar (BC2), and activated carbon (BC3), could facilitate abiotic reduction of trifluralin and pendimethalin by sulfides of environmentally-relevant concentrations in anoxic coastal sediments. The reduction rates of trifluralin and pendimethalin increased substantially with increasing BC dosages in the sediments. This enhancing effect was dependent on BC type with the greatest for BC3 followed by BC1 and BC2, which well correlated with their specific surface area. The pseudo-first order reduction rate constants (kobs) for BC3-amended sediment (2%) were 13- and 14 times the rate constants in the BC-free sediment. The reduction rates increased with increasing temperature from 8 to 25°C in the BC-amended sediment, following the Arrhenius relationship. Finally, through molecular modeling by density functional theory and reaction species identification from mass spectra, molecular pathways of trifluralin and pendimethalin reduction were elucidated. In contrary to the separate sequential reduction of each nitro group to amine group, both nitro groups, first reduced to nitroso, then eventually to amine groups.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China. Electronic address: xhliu@bnu.edu.cn.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Liu
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: Shuhua
authors.initials: S
authors.lastname: Xia
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
authors.forename: Baocui
authors.initials: B
authors.lastname: Liang
authors.affiliation: Department of Plant, Soil and Microbial Sciences and Environmental Science and Policy Program, Michigan State University, East Lansing, MI 48824, United States. Electronic address: weizhang@msu.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D002606:Charcoal / Q000737:chemistry*; D019015:Geologic Sediments; D006540:Herbicides / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013440:Sulfides / Q000737:chemistry*; D013696:Temperature; D014274:Trifluralin / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D006540:Herbicides; D013440:Sulfides; D014874:Water Pollutants, Chemical; C540010:biochar; D002606:Charcoal; D014274:Trifluralin; C030856:pendimethalin
keywords: Abiotic reduction; Black carbon; Density functional theory; Dinitroaniline herbicides; Sediment