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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., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Over 60% of herbicides are capable of disrupting the endocrine and/or reproductive systems of animals. These herbicides may be released into the atmosphere in both gas and particulate phases, but most of their degradation processes in the atmosphere are not well known. In this study, the heterogeneous reactions of suspended isopropalin, trifluralin, and alachlor particles with NO₃ radicals were investigated using an online vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer. The reaction products for the three herbicides were determined by the assistance of the gas chromatography-mass spectrometer analysis. Mono-dealkylated derivatives were detected as the main reaction products of isopropalin and trifluralin. In addition, an α-amino alcohol product was detected for isopropalin. The carbonylation derivative and the nitro-substituted derivative were the main reaction products observed for alachlor. The reaction mechanism of NO₃ radical-induced N-dealkylation for isopropalin was clarified by density functional theory calculations. It began with the H-abstraction from the N-propyl group, followed by the formation of the α-peroxypropyl radical, α-propyloxy radical, and α-amino alcohol, as well as by the collapse of the α-amino alcohol. The oxidation mechanism for trifluralin is similar to that of isopropalin, whereas the mechanism for alachlor involves carbonylation and nitro-substitution. These results provided insights on the chemical transformation of these herbicides in the atmosphere. The data generated from this study can be used as fundamental information for future studies on their toxic effects to the environment., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The ozonation of trifluralin coated on azelaic acid particles is investigated with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer. The suspended trifluralin particles with the mean diameter of 270nm react with approximately 100ppm ozone in an aerosol reaction chamber under ambient pressure and room temperature (1atm, 298K). The time-of-flight mass spectra of the trifluralin particles and the solid state ozonides are obtained. The assignments of the mass spectra reveal that the major primary ozonides of trifluralin particles are 2,6-dinitro-N-propyl-N-propanoyl-4-(trifluoromethyl) benzamine and 2,6-dinitro-N-(propan-2(and 3)-ol)-N-propyl-4-(trifluoromethyl) benzamine. The major secondary ozonides of trifluralin 2-ethyl-7-nitro-5-(trifluoromethyl) benzimidazole-3-oxide, 2,6-dinitro-N-propyl-4-(trifluoromethyl) benzenamine and 2,6-dinitro-N-(formyl)-N-propyl-4-(trifluoromethyl) benzamine are observed. The primary ozonides are directly resulted from the oxidation of N-propyl groups. The pathways of the primary ozonation are proposed in the paper.

A multi-pesticide (MP) method was developed and single-laboratory validated for the quality control of commercial pesticide products containing alachlor, chlorpyrifos methyl, fenthion and trifluralin as active ingredients (a.i.). A capillary gas chromatographic system with flame ionization detection (FID) and a programmable temperature vaporising split injector was used. The performance characteristics (specificity, linearity, precision and repeatability) of the method satisfied international acceptability criteria.