Seasonal and Spatial Variation of Solvent Extractable Organic Compounds in Fine Suspended Particulate Matter in Hong Kong

Abstract

The results of a 12-month study of more than 100 solvent extractable organic compounds (SEOC) in particulate matter (PM) less than or equal to 2.5 m (PM 2.5 ) collected at three air monitoring stations located at roadside, urban, and rural sites in Hong Kong are reported. The total yield of SEOC that accounts for ϳ8 -18% of organic carbon (summer/winter differences) were observed with higher concentrations of the total and each class of SEOC in the winter and lower concentrations in the summer. Spatial variations are also obvious, with the roadside samples having the highest concentrations of SEOC and the rural samples having the lowest concentrations in all seasons. Characteristic ratios of petroleum hydrocarbons, such as carbon preference index, unresolved to resolved components, and carbon number with maximum concentration, suggest that PM 2.5 carbon in Hong Kong originates from both biogenic and anthropogenic sources. The proportion of SEOC in PM 2.5 from anthropogenic sources is estimated. INTRODUCTIONRecent concern about the health effects of air pollution has focused on suspended particulate matter or aerosols. Several studies 1-4 reveal links between the concentrations of suspended particulate concentrations and the mortality and morbidity of the exposed population. There has been some evidence that fine PM has greater impact on human health than do the coarser fractions. 5-8 Organic carbon (OC) has been widely reported 9 -11 to be a major component (over 40%) of fine suspended particles. Since the 1990s, studies have been carried out to identify and quantify the individual components of solvent extractable organic compounds (SEOC) in total suspended particulate (TSP), 12-17 PM 10 (particles with aerodynamic diameters less than 10 m), 18 -21 and PM 2.5 (particles with aerodynamic diameters less than 2.5 m). 22 Studies on the SEOC content and molecular markers in aerosols collected in China started in the early 1990s, as reported by Simoneit et al. 12 Fang et al. 13 first reported the content of SEOC in TSP samples collected in Hong Kong during the winter months of 1993. A study of the monthly average SEOC in PM 2.5 collected from the campus of the Hong

Composition and sources of carbonaceous aerosols at three contrasting sites in Hong Kong

“…Urban sites, with large contributions from anthropogenic emissions, generally have CPIs ranging between 1.1 and 2.0, while rural areas with more biogenic influence generally have CPIs above 2.0 [ Simoneit , 1989; Zheng et al , 2000]. The CPIs of n ‐alkanes in the present study ranged from 1.25 to 1.73, similar to the value (ranging from 1.26 to 1.50) reported by the Government Laboratory of HKSAR [ Sin et al , 2005]. The similar low CPI values were also found by Zheng et al [2000], who suggested that most n ‐alkanes in Hong Kong are from petroleum residue.…”

“…The solvent‐extractable organic compound (SEOC) analysis by the Government Laboratory of HKSAR has been detailed by Sin et al [2005]. In brief, internal standards including hexadecane‐ d 34 , eicosane‐ d 42 , tetracosane‐ d 50 , triacontane‐ d 62 , acenaphthalene‐ d 10 , phenanthrene‐ d 10 , chrysene‐ d 12 , and perylene‐ d 12 were spiked to the samples before extraction.…”

“…However, compared to the inorganic species, identification and quantification of organic carbon as well as its major sources are far from well understood because OC is a complex mixture of hundreds of organic compounds emitted from a variety of sources. In general, ∼20% of the fine organic carbon in aerosol is solvent extractable and GC‐resolvable, including alkanes, fatty acids, polycyclic aromatic hydrocarbons, alkanols, and other polar compounds [ Sin et al , 2005; Zheng et al , 2000].…”

“…PM2.5 samples from the same three sampling sites during the same study period were also analyzed for solvent extractable and GC‐resolvable organic compounds by the Government Laboratory of Hong Kong Special Administrative Region (HKSAR) [ Sin et al , 2005]. A direct comparison of organic compound analysis was made between two laboratories.…”

Minimizing Contamination from Plastic Labware in the Quantification of C16 and C18 Fatty Acids in Filter Samples of Atmospheric Particulate Matter and Their Utility in Apportioning Cooking Source Contribution to Urban PM2.5

“…Organic tracer analysis of filter samples often involves extraction using organic solvents such as dichloromethane or methanol and subsequent filtration for purification, removal of filter fiber residue and insoluble particulate matter (e.g., [4,19,20]). In these procedures, disposable plastic labware, such as the syringe, syringe filter discs, and pipette tips, are commonly used due to convenience and as a precautionary measure to avoid sample-to-sample cross contamination.…”