Chemical characterization of water-soluble components of PM₁₀ and PM_2.5 atmospheric aerosols in five locations of Nanjing, China

A comprehensive survey for atmospheric pollution was carried out from February to December 2001 in Nanjing city in order to better control the problem. As part of the work, the current study mainly aims at the chemical characterization of water-soluble species of PM₁₀ and PM_2.5 atmospheric aerosols, together with their spatial variations. Much heavier particle loadings is observed in Nanjing city, which is more than 4-6 times of NAAQS of the USA, especially fine particles. During the sampling time, 63-77% of PM₁₀ mass is in the PM_2.5 fraction. Water-soluble fractions of PM₁₀ and PM_2.5 are acidic, and the acidity of PM_2.5 is stronger than that of PM₁₀. Water-soluble organic carbon, accounting for about 10% of particle mass, is the most significant component of the water-soluble fraction and shows no clear spatial variations. NO₃^-, SO₄^2-, NH_x (ammonia and ammonium), Ca²⁺, K⁺ and Na⁺ are also abundant in PM₁₀ and PM_2.5 aerosols. Among the detected water-soluble inorganic chemicals SO₄^2- presented the first highest level of concentration in PM₁₀ (16.70-23.51μg/m³, 3.3-10.9% of the PM₁₀ mass) and in PM_2.5 (13.19-20.24μg/m³, 3.8-11.2% of the PM_2.5 mass), NO₃^- and NH_x are the second highest level of chemicals followed by Ca²⁺, K⁺ and Na⁺. Nearly all those water-soluble inorganic components displayed the higher level of concentrations in the traffic center (SY) and the downtown area (FZ), and presented the lower level of concentrations in the scenery district and the residential area. The total mass of water-soluble fraction, including inorganic species and organic chemicals, also presented the higher concentrations (78.97-108.68μg/m³, 15.7-42.9% of particle mass) at both sites of SY and FZ.