Polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matters in Nanjing, China: Distributions, sources and meteorological influences

Abstract

A study of 16 polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matters at suburban and urban sites in Nanjing was carried out each season from November 2009 to July 2010. At the suburban and urban sites, the concentrations of total PAHs (T-PAHs) were in the ranges of 30.76–102.26 ng/m3 and 25.92–90.80 ng/m3, respectively. This paper elucidates the distributions, sources of PAHs and meteorological influences: 1) PAHs concentrations at the two sites were close to each other and similarity between PAHs profiles of the two sites indicated they had common sources, which were attributed to the combined effect of regional transport and local emission. 2) At both sites, the profiles displayed obvious seasonal variations, as a result of the seasonality of sources and meteorological influences. The T-PAHs concentrations were in the order of winter > spring > autumn > summer. 3) Source apportionment showed vehicle exhaust (72.93–87.24%) was the greatest contributor in all seasons. The coal combustion and coke production (coal/coke) (10.02–18.63%) were identified in all but summer seasons, because of the low collection efficiency of PAHs markers of coal/coke under high temperature. For autumn, biomass burning (10.58%) was an extra contributor. 4) Regarding meteorological parameters, a negative effect of temperature over PAHs was confirmed, with a correlation coefficient of −0.51 (p < 0.05). Precipitation could remove PAHs to some extent. Both positive and negative correlations between PAHs concentration and wind speed in each season were analyzed in combination with air mass back-trajectories so as to evaluate the effects of regional air transport. The results showed that polluted air from ENE-S and NNW-NE brought in outside sources to the study area and played a major role in the accumulation of fine-particulate PAHs in spring and winter respectively, while clean air from southwest contributed to the dilution in summer.