Secondary Organic Aerosols Formed from Photooxidation of Biogenic Volatile Organic Compounds in Forests

Photooxidation products of biogenic volatile organic compounds were characterized and measured in PM2.5 (particulate matter with an aerodynamic diameter les2.5 mum aerosol samples from forests. Aerosol sampling was conducted at four sites centred in and around major research stations located in four different regions of China: Xiaoxing´an Ling (boreal), Dongping national forest park (temperate), Dinghu mountain (subtropical) and Wuzhi mountain nature reserve (tropical) during summer periods when the meteorological conditions are believed to be favorable for photochemical processes. Thirty samples were collected; particular matter (PM), organic carbon, elemental carbon, organic compounds, inorganic ions, and trace gases were measured. Results indicate that the average concentrations of isoprene and alpha-pinene oxidation products, sugars and sugar alcohols vary systematically along gradients of ecological succession, except malic acid which may have both biogenic and anthropogenic origins. The maximum contributions of organic components, isoprene and alpha-pinene oxidation products, sugars, sugar alcohols, and inorganic ions, SO42-, NO3-, C2O42-, to the PM was 28%.