Photochemical oxidation of di-n-butyl phthalate in atmospheric hydrometeors by hydroxyl radicals from nitrous acid
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The photochemical oxidation of di-n-butyl phthalate (DBP) by •OH radicals from nitrous acid (HONO) in atmospheric hydrometeors was explored by two techniques, steady-state irradiation, and laser flash photolysis (LFP). The effects of atmospheric liquid parameters on DBP transformation were systematically evaluated, showing that DBP does not react with HONO directly and •OH-initiated reactions are crucial steps for consumption and transformation of DBP. Two reaction channels are operative: •OH addition and hydrogen atom abstraction. The overall rate constant for the reaction of DBP with •OH is 5.7 × 109 M−1 s−1, and its specific rate constant for addition is 3.7 × 109 M−1 s−1 determined by using laser flash photolysis technique. Comparing the individual reaction rate constant for aromatic ring addition with the total rate constant, the majority of the •OH radicals (about 65%) attack the aromatic ring. The major transformation products were identified by GC-MS, and the trends of their yields derived from both ring addition and H-abstraction with time are discussed. These results provide important insights into the photochemical transformation of DBP in atmospheric hydrometeors and contribute to atmospheric aerosol chemistry.
KeywordsDi-butyl phthalate Nitrous acid Hydroxyl radicals Kinetics Mechanisms Atmospheric hydrometeors
Financial support was provided by the National Natural Science Foundation of China (NSFC) (21876038) and the Key University Science Research Project of Anhui Provincial Education Department of China (KJ2017ZD46).
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