The atmospheric degradation reaction of dehydroabietic acid (DHAA) initiated by OH radicals and O3.

Dehydroabietic acid (DHAA) is the major marker compound emitted from the burning of conifer. In this paper, the atmospheric mechanism of DHAA initiated by OH radicals and O3 was studied at the MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. For OH radicals, two types of reactions including OH addition and hydrogen abstraction were investigated. The cycloaddition reactions of O3 were considered. The rate constants over the temperature range of 200-400 K were calculated with the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. At 298 K and under the pressure of 760 Torr, the whole rate constants are 0.89×10(-11) cm(3) molecule(-1) s(-1) and 2.29×10(-20) cm(3) molecule(-1) s(-1) for DHAA+OH and DHAA+O3, respectively. This study can be regarded as an attempt to investigate the OH-initiated and O3-initiated photochemical reaction mechanisms of DHAA in the atmosphere.