Chemical Characteristics of Water Soluble Components of Fine Particulate Matter, PM 2.5 , at Delhi, India

Abstract

Aerosol samples in the size range up to 2.5µm were collected from January to December, 2005 at New Delhi, India, as a pilot experiment and analysed for organic (Oxalate and Formate) and inorganic (Sulfate, Ammonium, Nitrate, Potassium, Chloride, Sodium, Calcium and Magnesium) chemical components. Initial results show that the annual mean PM2.5 concentration was 98.7µg/m 3 , which varied between 38 to 285µg/m 3 . The water soluble inorganic fraction constituted only 9% of PM2.5 with SO4 2- , NH4 + and NO3 - being the dominant ions followed by potassium. Annual cycle shows higher concentration of PM2.5 during winter season (October to January) and the lowest during monsoon. It is attributed to the enhanced production of aerosols and prevailing meteorological conditions. The PM2.5/PM10 ratio (0.86) coupled with the Hy SPLIT air-mass back trajectories indicated that PM2.5 was dominated by fine particles, when the winds passed through the eastern azimuth, where many industries and major thermal power plants are located.