Heterogeneous Oxidation Of Secondary Organic Tracers In PM2.5 By Ozone

Secondary Organic aerosols?SOA?are important part of PM2.5 in China.It has important contribution to the pollution of heavy haze.It is vital to find out the main precursor of SOA's contributions to atmosphere for controlling the pollution of heavy haze.At present,Tracer-based method has been widely used in analyzing the contribution of the precursors to SOA.However,multiphase oxidation of trace organic constituents inside of complex atmospheric particles is not well understood.It has significance to correcting Tracer-based method by clearing the heterogeneous oxidation of tracers.This study has chosen 2-ME which is a tracer of isoprene SOA,and DHOPA which is a tracer of toluene SOA,as well as the Analogue of 2-ME which is AME.Determining the uptake coefficient of ozone on the surface of the particles of pure AME and DHOPA,which are 2.11×10^-88 and 7.75×10^-8,The Second-order reaction rate constants of AME and DHOPA are 1.66×10^-19cm³·molecule^-1·s^-1and6.09×10^-19cm³·molecule^-1·s^-11 by in situ FTIR.Experiments were carried out in a smog chamber to investigate the oxidation of pure AME and DHOPA exposed to gas phase ozone under different conditions.When pure AME and DHOPA are exposed to 160?±10?ppb of O₃ with the condition of 71.3?±5?%of RH and room temperature,Pure AME has an atmospheric life time of 8.5 days,and the relative rate constants are 5.90×10^-1919 cm³·molecule^-1·s^-1,Pure DHOPA has an minimal atmospheric lifetime of 6.4 days,the relative rate constants are 7.67×10^-19cm³·molecule^-1·s^-1.The oxidation of 2-ME in toluene SOA and DHOPA in isoprene SOA exposed to gas phase ozone,we have made clear that the isoprene and toluene SOA have a hindrance to the ozonation of 2-ME and DHOPA.Where the relative rate constants are 1.12×10^-19and 2.04×10^-19cm³·molecule^-1·s^-1.According to the experimental results of this study that has been found the oxidation of AME and DHOPA.Simulating the decay of 2-ME and DHOPA aerosols whose heterogeneous oxidation with ozone under typical summertime conditions of shenzhen.After 30 days,about 40%to 90%of th e 2-ME and 55%to 95%of DHOPA will be oxidized,if the residence time of 2-ME and DHOPA are five days.The contribution of isoprene and toluene to the secondary source might be underestimated 10%to 40%and 15%to 50%,respectively.