Polar organic tracers in PM 2.5 aerosols from forests in eastern China

Photooxidation products of biogenic volatile organic compounds, mainly isoprene and monoterpenes, are significant sources of atmospheric particulate matter in forested regions. The objectives of this study were to examine time series and diel variations of polar organic tracers for the photooxidation of isoprene and α-pinene to investigate whether they are linked with meteorological parameters or trace gases, and to determine their carbon contributions. In addition, the biogenic secondary organic carbon contributions from isoprene were estimated. PM 2.5 (particulate matter with an aerodynamic diameter 2.5 samples were collected; eighteen organic compounds, organic carbon (OC), elemental carbon and trace gases were measured. Results indicate that the concentration trends of the secondary organic compounds reflected those of the trace gases and meteorological parameters. Very good correlations between the sum concentrations of isoprene oxidation products and atmospheric SO 2 , O 3 , NO 2 , NO x , as well as CO 2 , at the Changbai site were found. The secondary OC due to isoprene was relatively high in tropical Hainan (0.27 μgC/m 3 ) where isoprene-emitting broadleaf species are dominant, but was comparable in boreal Changbai (0.32 μgC/m 3 ) where coniferous species are prevalent. The contribution of malic acid, which may have both biogenic and anthropogenic sources, to the OC mass was comparable at the four sites.