Characteristics of hopanoid hydrocarbons in ambient PM10 and motor vehicle emissions and coal ash in Taiyuan, China

Abstract

Hopanoid hydrocarbon content in ambient particulate matter (PM) of less than or equal to 10 μm aerodynamic diameter (PM10) was sampled at seven sites representative of different functional districts, and measured by gas chromatography-mass spectrometry. 17α(H),21β(H)-hopane (C30αβ) and 17α(H),21β(H)-30-norhopane (C29αβ) were dominant in all samples. Hopanes in motor vehicle emissions from various fuel-type engines (gasoline, diesel and natural gas) and coal ash were qualitatively measured, and the amount of C30αβ was about two to three times greater than that of C29αβ. Distinct seasonal variations (winter/summer differences) were observed at higher concentrations (45.54-108.29 ng/m(3)) of total hopanes in winter and lower (2.59-28.26 ng/m(3)) in summer. There were also clear spatial variations of hopanes in Taiyuan, with samples with greater hopane concentrations in downtown areas, but less in summer. The spatial distribution reversed in winter. Distributions and relative abundances of selected hopanes from PM10 and source emissions indicated that in summer, vehicle exhaust was the dominant fossil fuel combustion source (C30αβ was >C29αβ), and that the contribution of coal combustion was slightly greater at suburban sites. However, the contribution of coal combustion sources increased significantly at all sites in winter, especially in suburban areas, where C29αβ exceeded C30αβ. Hopanoid indexes revealed a classification of vehicle exhaust and coal combustion emissions in PM10. The results imply that during rapid urbanization, it is crucial to strengthen the construction of infrastructure such as central heating in new city districts and to increase the use of natural gas instead of residential coal burning.