Characteristics of chemical compositions of atmospheric aerosols in Hong Kong : Spatial and seasonal distributions

Chemical compositional data of respirable suspended particulate (RSP) measured at 11 stations of the Hong Kong Air Quality Monitoring Network between 1990 and 1994 were analyzed for their seasonal and spatial variations. The concentration of atmospheric aerosols was low in Hong Kong compared to some large cities located in East Asia. RSP and most of the chemical species show seasonal variations which reflect the weather conditions: low concentrations in the rainy season of summer and high concentrations for the rest of the year. Carbonaceous aerosols accounted for approximately half of the mass and dominated the seasonal and spatial variations of RSP concentrations. SO₄ ^2-, NH₄ ⁺ and NO₃ ^-, accounting for a quarter of RSP mass, were mainly from long distance transport as their spatial distributions throughout Hong Kong were quite even. Marine aerosols, found throughout Hong Kong, accounted for 5.7% of RSP mass. Their seasonal variations in both the marine aerosols and the SO₄ ²-, NH₄ ⁺ and NO₃ ^- aerosols were controlled by the East Asian monsoons. The equivalent concentration ratio of Cl^-/Na⁺ indicated the presence of the chloride loss reaction and had a minimum ratio in September. Ca, K⁺, A1 and Mn from moving road dusts and construction and reclamation works follow the same seasonal distributions as RSP. Their spatial distributions reflect the presence of a large reclamation project on western Kowloon. The percent mass abundance of C, Zn, Pb, Br^- and Ni observed in the roadside station to monitoring vehicle emission pollution were similar to the values in Phoenix, US MW5050 PM₂₅ vehicle source profile. Cu was predominantly found in industrial and mixed areas where many small scale printed circuit board factories and ship repairing industries were located.