Characteristics and seasonal variations of PM2.5, PM10, and TSP aerosol in Beijing.

OBJECTIVE To investigate the seasonal characteristics and the sources of elements and ions with different sizes in the aerosols in Beijing. METHODS Samples of particulate matters (PM2.5), PM10, and total suspended particle (TSP) aerosols were collected simultaneously in Beijing from July 2001 to April 2003. The aerosol was chemically characterized by measuring 23 elements and 18 water-soluble ions by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ion chromatography (IC), respectively. RESULTS The samples were divided into four categories: spring non-dust, spring dust, summer dust, and winter dust. TSP, PM10, and PM2.5 were most abundant in the spring dust, and the least in summer dust. The average mass ratios of PM > 10, PM2.5-10, and PM2.5 to TSP confirmed that in the spring dust both the large coarse (PM > 10) and fine particles (PM2.5) contributed significantly in summer PM2.5, PM2.5-10, and PM > 10 contributed similar fractions to TSP, and in winter much PM2.5. The seasonal variation characteristics of the elements and ions were used to divide them into four groups: crustal, pollutant, mixed, and secondary. The highest levels of crustal elements, such as Al, Fe, and Ca, were found in the dust season, the highest levels of pollutant elements and ions, such as As, F-, and Cl-, were observed in winter, and the highest levels of secondary ions (SO4(2-), NO3-, and NH4+) were seen both in summer and in winter. The mixed group (Eu, Ni, and Cu) showed the characteristics of both crustal and pollutant elements. The mineral aerosol from outside Beijing contributed more than that from the local part in all the reasons but summer, estimated using a newly developed element tracer technique.