Characterization of chemical species in PM 2.5 and PM 10 aerosols in Hong Kong

Abstract

Aerosol samples for PM 10 and PM 2.5 were collected in wintertime from November 2000 to February 2001 at three different sampling locations in Hong Kong. PM 10 and PM 2.5 were collected by high-volume (hi-vol.) samplers and the concentrations of major elements, ions, organic and elemental carbons were quantified. The ratios of PM 2.5/PM 10 were 0.61 and 0.78 at the PolyU campus and Kwun Tong (KT), respectively. These results indicated that the concentrations of PM 2.5 contribute the majority of the PM 10 fraction. The concentrations of anthropogenic species (e.g. Pb and Cu) in PM 10 and PM 2.5measured at urban areas were generally higher than at an urban background site (Hok Tsui, HT). The major fractions of sulfate at three monitoring sites are non-sea-salts (nss) sulfates. Although HT is located in coastal areas, the contribution of sea salts to sulfate in fine particles was small, indicating a substantial anthropogenic origin. The OC/EC ratios were less than 2 in PolyU and KT monitoring stations for PM 10 and PM 2.5. However, the OC/EC ratios were over 3 at HT for both PM 10 and PM 2.5. This indicates the presence of secondary organic aerosols. Correlations between OC and EC as well as OC and sulfate in HT during both seasons were used to prove that atmospheric transport and transformation of anthropogenic organic species from northeastern area was the dominant source in winter. The chemical composition of the samples was reconstructed from the observed elemental composition. The contribution of the seven components, namely crustal matter, sea salt, ammonium, sulfate, nitrate, elemental carbon and organic matter accounted for 77–84% of the PM 10 and PM 2.5 mass in the urban area (PolyU and KT) and 74% for Hok Tsui (HT). Sulfate, organic matter and elemental carbon are the major constituents in particles especially in PM 2.5 collected at PolyU and KT. The major constituents of PM 10 in HT are sea salt and sulfate.