title: Photochemical transformation of the insensitive munitions compound 2,4-dinitroanisole.
abstract: The insensitive munitions compound 2,4-dinitroanisole (DNAN) is increasingly being used as a replacement for traditional, sensitive munitions compounds (e.g., trinitrotoluene [TNT]), but the environmental fate and photo-transformation of DNAN in natural water systems are currently unknown. In this study, we investigated the photo-transformation rates of DNAN with both ultraviolet (UV) and sunlight irradiation under different environmentally relevant conditions. Sunlight photo-transformation of DNAN in water was found to follow predominantly pseudo-first-order decay kinetics with an average half-life (t(1/2)) of approximately 0.70 d and activation energy (E(a)) of 53 kJ mol(-1). Photo-transformation rates of DNAN were dependent on the wavelength of the light source: irradiation with UV-B light (280-315 nm) resulted in a greater quantum yield of transformation (φ(UV-B)=3.7×10(-4)) than rates obtained with UV-A light (φ(UV-A)=2.9×10(-4) at 316-400 nm) and sunlight (φ(sun)=1.1×10(-4)). Photo-oxidation was the dominant mechanism for DNAN photo-transformation, based on the formation of nitrite (NO(2)(-)) and nitrate (NO(3)(-)) as major N species and 2,4-dinitrophenol as the minor species. Environmental factors (e.g., temperature, pH, and the presence or absence of naturally dissolved organic matter) displayed modest to little effects on the rate of DNAN photo-transformation. These observations indicate that sunlight-induced photo-transformation of DNAN may represent a significant abiotic degradation pathway in surface water, which may have important implications in evaluating the potential impacts and risks of DNAN in the environment.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA. anandharaob@ornl.gov
authors.forename: Balaji
authors.initials: B
authors.lastname: Rao
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Cai
authors.forename: Todd
authors.initials: T
authors.lastname: Anderson
authors.forename: Baohua
authors.initials: B
authors.lastname: Gu
mesh_terms: D000840:Anisoles / Q000737:chemistry*; D053834:Explosive Agents; D006207:Half-Life; D007700:Kinetics; D055668:Photochemical Processes; D014466:Ultraviolet Rays
chemical_list: D000840:Anisoles; D053834:Explosive Agents; C539360:2,4-dinitroanisole