Seasonal variation and source apportionment of PM 2.5 -bound trace elements at a coastal area in southwestern Taiwan

Abstract

The aim of this study is to investigate the seasonal variations and source apportionment on atmospheric fine particulate matter (PM_2.5) mass and associated trace element concentrations at a coastal area, in Chiayi County of southwestern Taiwan. Particle measurements were conducted in 2015. Twenty-three trace elements in PM_2.5 were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Multiple approaches of the enrichment factor (EF) analysis and positive matrix fraction (PMF) model were used to identify potential sources of PM_2.5-bound trace elements. Daily mean concentration of PM_2.5 in cold season (25.41 μg m⁻³) was higher than that in hot season (13.10 μg m⁻³). The trace elements contributed 11.02 and 10.74% in total PM_2.5 mass concentrations in cold season and hot season, respectively. The results of EF analysis confirmed that Sb, Mo, and Cd were the top three anthropogenic trace elements in the PM_2.5; furthermore, carcinogenic elements (Cr, Ni, and As) and other trace elements (Na, K, V, Cu, Zn, Sr, Sn, Ba, and Pb) were attributable to anthropogenic emissions in both cold and hot seasons; however, highly enriched Li and Mn were observed only in cold season. The PMF model identified four main sources: iron and steel industry, soil and road dust, coal combustion, and traffic-related emission. Each of these sources has an annual mean contribution of 8.2, 27.5, 11.2, and 53.1%, respectively, to PM_2.5. The relative dominance of each identified source varies with changing seasons. The highest contributions occurred in cold season for iron and steel industry (66.2%), in hot season for traffic-related emission (58.4%), soil and road dust (22.0%), and coal combustion (2.8%). These findings revealed that the PM_2.5 mass concentration, PM_2.5-bound trace element concentrations, and their contributions were various by seasons.