PM2.5 Chemical Composition Analysis in Different Functional Subdivisions in Tangshan, China

ABSTRACT

In this study, the 24-h PM_2.5 (i.e., the fine particles with aerodynamic diameter of ≤ 2.5 µm) samples were collected at two different functional subdivisions in the city of Tangshan during the period of July 2012 to April 2013. The months of July, October, January, and April were chosen to represent four different typical seasons. The total PM2.5 mass was measured. PM_2.5 samples were used for the analysis of inorganic elements, ions, Organic Carbon (OC) and Elemental Carbon (EC). PM_2.5 concentration in the industrial subdivision were generally higher than those in the residential subdivision. The annual mean PM_2.5 concentrations were 196 µg m^–3 for the industrial subdivision and 116 µg m^–3 for the residential subdivision. The coefficients of divergence (CD) calculated for spring, summer, autumn and winter were 0.67, 0.35, 0.65, and 0.33, respectively. The Enrichment Factor Method (EFM) was used to help determine the original sources of these inorganic elements. Secondary water-soluble ions (SO₄^2–, NO₃^–, and NH₄⁺) were the major water soluble ions in the PM_2.5 of Tangshan, and they are present in the atmosphere as (NH₄)₂SO₄ and NH₄NO₃. The Sulfur Oxidation Ratio (SOR) and Nitrogen Oxidation Ratio (NOR) show that the precursor conversion ratio was highest in summer. At both subdivisions, winter had the highest monthly average OM concentration while summer had the lowest.