Urbanization-related changes in soil PAHs and potential health risks of emission sources in a township in Southern Jiangsu, China.

Urbanization, which is characterized by population aggregation, industrial development, and increased traffic load, may change local polycyclic aromatic hydrocarbons (PAH) emissions and their associated health risks. To investigate these changes, we collected soil samples in 2009 and 2014 in a rapidly developing small town in Southern Jiangsu (China) and measured the concentrations of 16 PAHs via gas chromatography-mass spectrometry. Although the total PAHs decreased from 4586.6 to 640.6ng/g, the concentrations of the high-molecular-weight PAHs benzo(b)fluoranthene and benzo(a)pyrene increased due to changes in the PAH sources. Source apportionment by positive matrix factorization indicated that the two sources responsible for the highest soil PAH contributions changed from biomass combustion (42%) and coal combustion (32%) in 2009 to coal, biomass and natural gas combustion (35%) and diesel combustion (33%) in 2014. However, the two sources with the highest associated health risks were diesel and gasoline combustion in both years. The incremental lifetime cancer risk for residents exposed to PAHs in the soil via incidental ingestion and dermal contact decreased from 1.75×10-6 to 1.60×10-6. The ban on open burning of straw and the substitution of coal with natural gas offset the PAH health risks due to increased urbanization.