[Characteristics and Sources of Water Soluble Inorganic Ions in Fine Particulate Matter During Winter in Xuzhou]

Abstract

A total of 32 daily PM_2.5 samples were collected from December 2016 to February 2017 in the urban area of Xuzhou city. Water-soluble inorganic ions (WSⅡs), including F^-, Cl^-, NO₃^-, SO₄^2-, Na⁺, Mg²⁺, NH₄⁺, K⁺ and Ca²⁺, were determined by ion chromatography. The average mass concentration of PM_2.5 was (164.8±77.3) μg·m^-3 and the average total mass concentration of the nine ions was (67.5±36.1) μg·m^-3, the contribution of the WSⅡs to the PM_2.5 was more than 40.9%. The order of the concentrations of individual ions was NO₃^- > SO₄^2- > NH₄⁺ > Cl^- > Ca²⁺ > K⁺ > Na⁺ > Mg²⁺ > F^-. NH₄⁺, NO₃^-, and SO₄^2- (SNA) were the major components of the water-soluble ions in the PM_2.5 measurement. The average mass concentration of WSⅡs in clean air, mild haze, and severe haze was (12.8±8.8), (59.0±22.8) and (86.3±36.0) μg·m^-3, respectively. The contribution of SNA to WSⅡs was 86.4%, 82.8%, and 78.9%, respectively. The correlation between each component of SNA with each other was significant. NH₄⁺, NO₃^-, and SO₄^2- were in the form of (NH₄)₂SO₄ and NH₄NO₃. Secondary formation, biomass burning, fossil fuel combustion, and dust were the major sources of the water-soluble ions in PM_2.5.

Keywords: PM2.5; Xuzhou; haze; source; water soluble inorganic ions.