摘要
Thirteen samples of PM2.5-10 (coarse) and PM2.5 (fine) were collected by Universal Air Sampler from February to March,2010 in Kaohsiung for investigating the impact of chemical composition of Asian dust storms (DS) and non-DS (NDS) in southern Taiwan.Based on back trajectories,two dust storm episodes were identified by different transport pathways.The analysis results were used to distinguish the behavior of metallic composition and particle size (coarse and fine particle fraction) between two DS (DSI and DSII) and NDS periods.During two DS episodes,metallic elements of Mn,Co,Al,Ca,Fe and Mg were significantly higher in concentrations of coarse fraction compared with NDS periods.The elemental ratios of DSI/NDS and DSII/NDS were from 3.1 to 3.9 and 9.0 to 28.2,respectively.Higher fraction in fine size particles was observed during NDS periods,while the coarse fraction contributed major mass during two DS episodes.The mass ratios (coarse particle/PM10) for NDS,DSI and DSII were approximately 29%,55% and 72%,respectively.Anthropogenic elements showed higher enrichment factor (EF) values during NDS periods,compared with two DS episodes.This may be ascribed to the excessive impact of crustal elements such as Al carried by two DS episodes.