Seasonal variations and sources of mass and chemical composition for PM₁₀ aerosol in Hangzhou, China

Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM₁₀ mass, 22 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Cd, Ba, and Pb), 5 major ions (F^-, Cl^-, NO₃^-, SO₄^2-, and NH₄⁺), and organic and elemental carbon (OC and EC), showing that PM₁₀ mass ranged from 46.7 to 270.8 μg/m³, with an annual average of 119.2 μg/m³. Na, Al, Si, S, K, Ca, and Fe were the most abundant elements in PM₁₀, most of S being in the form of SO₄^2-. SO₄^2-, NO₃^-, and NH₄⁺ were the major ions, which contributed to about 20% of the PM₁₀ mass. The mean seasonal concentrations for SO₄^2-, averaged over all sites, were found to be 18.0, 18.5, 24.7, and 21.4 μg/m³, for spring, summer, autumn, and winter, respectively, while the corresponding loadings for NO₃^- were 7.2, 4.7, 7.1, and 11.2 μg/m³, and for NH₄⁺ were 6.0, 5.9, 8.2, and 9.3 μg/m³, in the form mostly of NH₄NO₃ in spring, autumn, and winter, and mostly of (NH₄)₂SO₄ in summer. The low NO₃^-/SO₄^2- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM₁₀ were found to be 21.4, and 4.1 μg/m³, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM₁₀ for the four seasons, as is characteristic for cities in South China.