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Surface soil samples were collected at the top and bottom of the Dashiwei karst tiankeng (large karst sinkholes) and measured for the presence of polynuclear aromatic hydrocarbons (PAHs). Comparisons were made on the distribution of PAHs at the top and bottom of the sinkhole, and their probable sources were inferred. The average sum of the 16 U.S. Environmental Protection Agency (USEPA) PAHs measured was 74.48 ng/g. At the top, the sum of PAHs (∑PAHs) ranged from 23.43 to 88.94 ng/g, with an average concentration of 57.76 ng/g, and at the bottom, they ranged from 43.51 to 190.47 ng/g, with an average concentration of 87.88 ng/g. Among the 16 USEPA PAHs detected, phenanthrene had the highest concentration, with an average soil concentration of 16.11 ng/g, and the lowest PAH, with an average soil concentration of 0.55 ng/g, was dibenzo[a,h]anthracene. Results suggest that the higher concentrations at the bottom were caused by lower sunlight penetration and evaporation. The probable source of most of the PAHs detected was inferred to be from petrogenic sources based on ratios of low molecular weight to heavy molecular weight (LMW/HMW), anthracene to anthracene + phenanthrene (AN/AN+PH), benzo[a]anthracene to chrysene (BaA/CH), and other petrogenic source ratio indicators.
I. Theodore Oramah is currently a research assistant at the Key Laboratory Biogeology and Environmental Geology of the Ministry of Education, China University of Geosciences, Wuhan, China. He received his B.Tech. degree in geology from Federal University of Technology, Minna, Nigeria (2004) and his M.Sc. degree in environmental science from China University of Geosciences, Wuhan, China (2007). In September 2007, he published an article in the Journal of Environmental Geochemistry & Health entitled “Distribution of polycyclic aromatic hydrocarbons in Datou Karst Tiankeng of South China.”