Chemical composition and source apportionment of PM _2.5 in urban areas of Xiangtan, central south China

Xiangtan, South China, is characterized by year-round high relative humidity and very low wind speeds. To assess levels of PM 2.5, daily samples were collected from 2016 to 2017 at two urban sites. The mass concentrations of PM 2.5 were in the range of 30⁻217 µg/m³, with the highest concentrations in winter and the lowest in spring. Major water-soluble ions (WSIIs) and total carbon (TC) accounted for 58⁻59% and 21⁻24% of the PM 2.5 mass, respectively. Secondary inorganic ions (SO₄ 2-, NO₃ -, and NH₄⁺) dominated the WSIIs and accounted for 73% and 74% at the two sites. The concentrations of K, Fe, Al, Sb, Ca, Zn, Mg, Pb, Ba, As, and Mn in the PM 2.5 at the two sites were higher than 40 ng/m³, and decreased in the order of winter > autumn > spring. Enrichment factor analysis indicates that Co, Cu, Zn, As, Se, Cd, Sb, Tl, and Pb mainly originates from anthropogenic sources. Source apportionment analysis showed that secondary inorganic aerosols, vehicle exhaust, coal combustion and secondary aerosols, fugitive dust, industrial emissions, steel industry are the major sources of PM 2.5, contributing 25⁻27%, 21⁻22%, 19⁻21%, 16⁻18%, 6⁻9%, and 8⁻9% to PM 2.5 mass.