Seasonal variation of ionic species in fine particles at Qingdao, China

Totally nine measurement campaigns for ambient particles and SO2 have been conducted during the period of 19972000 in Qingdao in order to understand the characteristics of the particulate matter in coastal areas of China. The mass fractions Of PM2.5, PM2.5-10 and PM>10 in TSP are 49%, 25% and 26%, respectively. The size distribution of particles mass concentrations in Qingdao shows bi-modal distribution. Mass fraction percentages of water-soluble ions in PM2.5, PM2.5-10 and PM>10 decreased from 62% to 35% and 21%. In fine particles, sulfate, nitrate and ammonium, secondary formed compounds, are major components, totally accounting for 50% Of PM2.5 mass concentration. The ratios of sulfate, chloride, ammonium and potassium in PM2.5 for heating versus non-heating periods are 1.34, 1.80, 1.56 and 1.44, respectively. The ratio of nitrate is 3.02 and this high ratio could be caused by reduced volatilization at lower temperature. Sulfate concentrations are higher than nitrate in PM2.5. The chemical forms of sulfate and nitrate are probably (NH4)(2)SO4 and NH4NO3 and chloride depletion was observed. Backward trajectory analysis reflected possible influence of air pollutant transport to Qingdao local aerosol pollution. (C) 2002 Elsevier Science Ltd. All rights reserved.