Compositions and source apportionments of atmospheric aerosol during Asian dust storm and local pollution in central Taiwan

Abstract

A study has been carried out on water soluble ions, trace elements, as well as PM(2.5) and PM(2.5-10) elemental and organic carbon samples collected daily from Central Taiwan over a one year period in 2005. A source apportionment study was performed, employing a Gaussian trajectory transfer coefficient model (GTx) to the results from 141 sets of PM(2.5) and PM(2.5-10) samples. Two different types of PM(10) episodes, local pollution (LOP) and Asian dust storm (ADS) were observed in this study. The results revealed that relative high concentrations of secondary aerosols (NO (3) (-) , SO (4) (2-) and NH (4) (+) ) and the elements Cu, Zn, Cd, Pb and As were observed in PM(2.5) during LOP periods. However, sea salt species (Na(+) and Cl(-)) and crustal elements (e.g., Al, Fe, Mg, K, Ca and Ti) of PM(2.5-10) showed a sharp increase during ADS periods. Anthropogenic source metals, Cu, Zn, Cd, Pb and As, as well as coarse nitrate also increased with ADS episodes. Moreover, reconstruction of aerosol compositions revealed that soil of PM(2.5-10) elevated approximately 12-14% in ADS periods than LOP and Clear periods. A significantly high ratio of non-sea salt sulfate to elemental carbon (NSS-SO (4) (2-) /EC) of PM(2.5-10) during ADS periods was associated with higher concentrations of non-sea-salt sulfates from the industrial regions of China. Source apportionment analysis showed that 39% of PM(10), 25% of PM(2.5), 50% of PM(2.5-10), 42% of sulfate and 30% of nitrate were attributable to the long range transport during ADS periods, respectively.