Particulate matter source apportionment based on a back trajectory model during episode days in central Taiwan

摘要

It is important to realize the contribution of air pollutants emission sources to ambient concentrations to establish proper and effective strategies. We applied the Gaussian trajectory transfer-coefficient model (Tsuang, 2003; Tseng et al., 2003) to simulate the particulate matter (PM) concentrations and the source apportionments at Chungming Station in central Taiwan during PM episode days in 2008. The location of the receptor is shown in Figure 1. Two kinds of PM episode days are selected. One PM episode is during Asia dust storm period (2-4 March 2008) and the other PM episode is effected by ill-dispersion synoptic pattern (29 March 2008). The correlation coefficient (R) between the observed and calculated daily PM10 concentrations from 28 February to 5 March 2008 including Asia dust storm is 0.716 (Figure 2). The source apportionments results indicated that the primary sources for PM10 at Chungming Station were subsidence (31%) during dust storm period and upwind boundary concentration (26%) during non-dust storm period (Figure 3). The subsidence played an important role during the Asia dust storm. The subsidence increased 12% PM10 apportionment during dust storm period than that during non-dust storm period. On the other hand, the correlation coefficient (R) between the observed and calculated daily PM10 concentrations from 26 March to 1 April 2008 including one PM episode day is 0.965 (Figure 4). The primary sources for PM10 at Chungming Station were upwind boundary concentration (24%) and point sources (23%) on the PM episode day (Figure 5). The synoptic system was high pressure circulation effected Taiwan which often causes the ambient in relatively stable condition. Not like the PM10 source apportionment during dust storm period, the subsidence was less important and the long range secondary aerosol transport and local emissions seemed to have much influence on the PM10 contribution to a receptor.