Aerosol characteristics at a rural station in southern peninsular India during CAIPEEX-IGOC: physical and chemical properties

To understand the boundary layer characteristics and pathways of aerosol–cloud interaction, an Integrated Ground Observational Campaign, concurrent with Cloud Aerosol Interaction and Precipitation Enhancement Experiment, was conducted by the Indian Institute of Tropical Meteorology, Pune, under Ministry of Earth Sciences at Mahabubnagar (a rural environment, which is ~100 km away from an urban city Hyderabad in Andhra Pradesh), during the period of July–November 2011. Collected samples of PM₂.₅and PM₁₀were analyzed for water-soluble ionic species along with organic carbon (OC) and elemental carbon (EC). During study period, the average mass concentrations of PM₂.₅and PM₁₀were about 50(±10) and 69(±14) μg m⁻³, respectively, which are significantly higher than the prescribed Indian National Ambient Air Quality Standards values. The chemical species such as sum of anions and cations from measured chemical constituents were contributed to be 31.27 and 38.49 % in PM₂.₅and 6.35 and 5.65 % to the PM₁₀, whereas carbonaceous species contributed ~17.3 and 20.47 % for OC and ~3.0 and 3.10 % for EC, respectively. The average ratio of PM₂.₅/PM₁₀during study period was ~0.73(±0.2), indicating that the dominance of fine size particles. Carbonaceous analysis results showed that the average concentration of OC was 14 and 8.7 μg m⁻³, while EC was 2.1 and 1.5 μg m⁻³for PM₁₀and PM₂.₅, respectively. The ratios between OC and EC were estimated, which were 6.6 and 5.7 for PM₁₀and PM₂.₅, suggesting the presence of secondary organic aerosol. Total carbonaceous aerosol accounts 23 % of PM₁₀in which the contribution of OC is 20 % and EC is 3 %, while 20 % of PM₂.₅mass in which the contribution of OC is 17 % and EC is 3 %. Out of the total aerosols mass, water-soluble constituents contributed an average of 45 % in PM₁₀and 38 % in PM₂.₅including about 39 % anions and 6 % cations in PM₁₀, while 31 % anions and 7 % cations in PM₂.₅aerosol mass collectively at study site.