Concentration, exchange and source identification of polycyclic aromatic hydrocarbons in soil, air and tree bark from the Middle-Lower Yangtze Plain, China

Polycyclic aromatic hydrocarbons (PAHs) were detected in tree bark, soil and air samples of the plain along the Yangtze River (Anhui section) which belongs to the Middle-Lower Yangtze Plain. Sigma(15)PAHs in tree bark, soil and air (collected using PUF based passive samplers) ranged from 27 to 1300 ng g (-1) dw, 140-5300 ng g(-1) dw, and 29-210 ngm(-3), respectively. The proportions of 3- and 4-ring PAHs were significantly higher in air and tree bark samples, whereas 5- and 6-ring PAHs were significantly higher in soils. Distribution of PAHs in barks of slow-growing wood (camphor tree) was similar with that in PUFs, and variation of PAHs in tree barks from same species was less than that from different species. Furthermore, all the 4-, 5- and 6-ring PAHs are not in equilibrium between air and bark. Air-soil exchange of 3- and 4-ring PAHs was dominated by net volatilization, while 5- and 6-ring PAHs were mostly reach the equilibrium. For the source identification of air-borne PAHs, diagnostic ratios of PAHs with molecular mass of 202 and 276 may be more appropriate as these ratios are more conservative. Through comprehensive analysis using diagnostic ratios and principal component analysis, combustion of petroleum, coal and biomass were the major sources of PAHs in the environmental compartments of the study area.