Dry deposition of polycyclic aromatic hydrocarbons and its influence on surface soil contamination in Tianjin, China.

ISCLT3 dispersion model was applied to calculate the flux of dry deposition of polycyclic aromatic hydrocarbons (PAHs) in Tianjin, China based on a high resolution emission inventory. Field observations of dry deposition at 22 sampling sites were used for model validation. The mean deposition flux densities (and standard deviation) of 15 PAHs were 4.62 +/- 2.99 microg m(-2) d(-1) and 2.75 +/- 1.78 microg m(-2) d(-1) in the heating and the non-heating seasons, respectively, with a time-weighted annual mean of 3.37 +/- 1.81 microg m(-2) d(-1) (based on the durations of the heating and non-heating seasons). High fluxes occurred in the urbanized areas as well as near two coke and gasification facilities. It was revealed that PAH concentrations in surface soil were correlated significantly with both dry deposition and soil organic matter content. Accordingly, a linear regression model was developed for predicting surface soil PAH concentration based on deposition flux density and soil organic matter content.