title: Gas-phase degradation of the herbicide ethalfluralin under atmospheric conditions.
abstract: The gas-phase degradation of ethalfluralin, N-ethyl-α,α,α-trifluoro-N-(2-methylallyl)-2,6-dinitro-p-toluidine, a widely used herbicide, was investigated under atmospheric conditions at the large outdoor European simulation chamber (EUPHORE) in Valencia, Spain. The photolysis of ethalfluralin was investigated under solar radiation and the mean photolysis rate coefficient was determined: J(ethalfluralin)=(1.3±0.2)×10(-3) s(-1) (JNO2=8×10(-3) s(-1)). The rate coefficients for the reactions of hydroxyl radicals and ozone with ethalfluralin in the dark were also measured under atmospheric conditions using the relative rate and the absolute rate technique, respectively. The rate coefficients values for the reactions of kOH(ethalfluralin)=(3.5±0.9)×10(-11)cm(3)molecule(-1)s(-1), and kO3(ethalfluralin)=(1.6±0.4)×10(-17) cm(3) molecule(-1) s(-1) were determined at 300±5 K and atmospheric pressure. The results show that removal of ethalfluralin from the atmosphere by reactions with OH radicals (τ ~ 4 h) or ozone (τ ~ 25 h) is slow compared to loss by photolysis. The available kinetic data suggest that the gas-phase tropospheric degradation of ethalfluralin will be controlled mainly by photolysis and provide an estimate for the tropospheric lifetime of approximately 12 min. The atmospheric implications of using ethalfluralin as a herbicide are discussed.
authors.affiliation: Instituto Universitario UMH-CEAM, C/Charles R. Darwin, 14, Parque Tecnológico, 46980 Paterna, Valencia, Spain. Electronic address: amalia@ceam.es.
authors.forename: Amalia
authors.initials: A
authors.lastname: Muñoz
authors.forename: Teresa
authors.initials: T
authors.lastname: Vera
authors.forename: Milagros
authors.initials: M
authors.lastname: Ródenas
authors.forename: Esther
authors.initials: E
authors.lastname: Borrás
authors.forename: Abdelwahid
authors.initials: A
authors.lastname: Mellouki
authors.forename: Jack
authors.initials: J
authors.lastname: Treacy
authors.forename: Howard
authors.initials: H
authors.lastname: Sidebottom
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D001274:Atmospheric Pressure; D002980:Climate; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D010126:Ozone / Q000737:chemistry; D010782:Photolysis; D013030:Spain; D014274:Trifluralin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry
chemical_list: D006540:Herbicides; D017665:Hydroxyl Radical; C027392:ethafluralin; D010126:Ozone; D014274:Trifluralin
keywords: EUPHORE; Ethalfluralin; Herbicides; Photooxidation; Tropospheric lifetime