Permalink : http://hdl.handle.net/2115/45167

Polar organic tracers of isoprene, α/β-pinene and β-caryophyllene photooxidation in tropical Indian aerosols (PM10) collected at Chennai were measured using gas chromatography/mass spectrometry. All the biogenic secondary organic aerosol (SOA) tracers showed diurnal variations with higher concentrations at daytime, which is in agreement with the fact that they are photochemical oxidation products of biogenic volatile organic compounds (VOCs). Total concentration ranges of the organic tracers were 18.3-107 ng m^[-3] in summer versus 2.69-66.9 ng m^[-3] in winter. Most of the SOA tracers showed higher concentrations in summer than in winter, while β-caryophyllinic acid, a tracer for β-caryophyllene, showed no seasonal differences. A good correlation (R2＝0.67) was found between the concentrations of 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA). In addition, both 3-hydroxyglutaric acid and MBTCA were strongly correlated with malic acid, indicating a similar formation pathway of these compounds in the tropical region. This study also suggests that isoprene and α/β-pinene oxidation products contribute almost equally to organic carbon (OC) in tropical India.