Characterization of PM, PM₁₀ and PM_2.5 mass concentrations at a tropical semiarid station in Anantapur, India

Abstract

The particulate matter (PM), PM₁₀ and PM_2.5 concentrations are estimated from regular measurements of size segregated as well as total mass concentration of near surface composite aerosols, using a ten-channel Quartz Crystal Microbalance (QCM) Cascade Impactor in a tropical semi-arid station, Anantapur, India for the period May 2006 – April 2007. The monthly variations of PM, PM₁₀ and PM_2.5 and season-wise shares of PM₁₀ and PM_2.5 to PM have been computed. The highest contribution of PM 10 to PM has been noticed during local summer season, while the maximum share of PM_2.5 to PM has been noticed during the winter season. The average values of PM, PM₁₀ and PM_2.5 mass concentrations have been found to be 21.21±1.21, 18.7±1.06 and 17.02±1.28 μg m^-3 ,respectively. Seasonally, the concentration has been highest in winter (24.62±3.53, 22.07±2.56, 21.29±2.31) and lowest in monsoon (18.12±1.62, 16.46±1.82, 14.47±1.57) for PM, PM₁₀ and PM_2.5, respectively. The back trajectory cluster analysis revealed that the aerosol loading has been significantly higher in fine mode during periods of continental air mass (winter) but when the winds shift to marine (monsoon), the loading became higher due to major contribution of sea salt aerosols, particularly in the coarse mode. PM₁₀ and PM_2.5 concentrations has been highly correlated with PM and inversely correlated with local wind speed. The results of this analysis underlined the importance of local emission sources, mostly from anthropogenic, which are responsible for the high PM₁₀ and PM_2.5 concentration levels observed during this one year - sampling period.