Spatial and temporal variation of PM2.5 and atmospheric PCDD/FS in Northern Taiwan during winter monsoon and local pollution episodes

Abstract

Winter monsoonal air masses traveling from Inner Mongolia to downwind nations can transport cold temperature and air pollutants. This study investigated the effects of the long-range transport (LRT) of air pollutants by northeastern monsoons and local pollution (LP) episodes on atmospheric PM2.5, polychlorinated dibenzo-p-dioxin (PCDD), and polychlorinated dibenzofuran (PCDF) concentrations in northern Taiwan during the winters of 2014 and 2015. Air samples were collected in rural (Rural Site 1 was mountainous; Rural Site 2 was coastal) and urban (Urban Site 1 was urban; Urban Site 2 was suburban) areas in northern Taiwan as well as at a background site (Lulin Mountain) in central Taiwan. Atmospheric PCDD/F concentrations measured at different sites ranged from 11.0 ± 2.70 to 39.7 ± 22.7 fg international toxicity equivalency quantity (I-TEQ) m–3 in 2014 and 7.99 ± 5.58 to 17.5 ± 12.3 fg I-TEQ m–3 in 2015. During LRT and LP, the proportion of PCDFs was higher than that of PCDDs. Rural Site 1 (122 pg I-TEQ g–1) and Urban Site 2 (82.4 pg I-TEQ g–1) had the highest PCDD/F content in PM2.5 during LRT and LP, respectively. The proportion of PCDD increased when neither event occurred. Principal component analysis revealed relationships between the component variance of PCDD/Fs and the sampling site altitude. The results of potential source contribution function (PSCF) suggested that the cold-air masses reaching Taiwan via LRT were most likely arriving from northern China, with pollutants collected along their routes. Wind speed and direction and geographical factors affected the accumulation of air pollutants in the atmosphere during LP.