To better characterize the tropical aerosols in Indianregion, PM samples collected from Chennai, India (13.04° N;80.17° E) were analyzed for carbonaceous and water-solubleionic components. Concentration ranges of elemental carbon (EC) and organiccarbon (OC) were 2.4–14 μg m (ave. 6.5 μg m) and3.2–15.6 μg m (ave. 9.1 μg m) in winter sampleswhereas they were 1.1–2.5 μg m (ave. 1.6 μg m) and4.1–17.6 μg m (ave. 9.7 μg m) in summer samples,respectively. Concentration of secondary organic carbon (SOC) retrieved fromEC-tracer method was 4.6±2.8 μg m in winter and4.3±2.8 μg m in summer. OC accounted for 38.5±14 % ( = 49)of combined concentrations of carbonaceous and ionic components inPM. We also found that OC concentrations are generally higher thanthose of SO (8.8±2.5 μg m and4.1±2.7 μg m in winter and summer, respectively), which was the mostabundant ionic species (57 %) followed by NH (15 %)>NO>Cl>K>Na>Ca>MSA>Mg.The mass fractions of EC, organic matter (OM) andionic species varied seasonally, following the air mass trajectories andcorresponding source strength. Based on mass concentration ratios ofselected components and relations of EC and OC to marker species, we foundthat biofuel/biomass burning is a major source of atmospheric aerosols inSouth and Southeast Asia. The high concentrations of SOC and WSOC/OC ratios(ave. 0.45; = 49) as well as good correlations between SOC and WSOCsuggest that the secondary production of organic aerosols during long-rangeatmospheric transport is also significant in this region. This studyprovides the baseline data of carbonaceous aerosols for southern part of theIndian subcontinent.
展开▼
