Particle dry deposition of polycyclic aromatic hydrocarbons and its risk assessment in a typical coal-polluted and basin city, northern China

Atmospheric dry deposition is a major pathway of pollutants removal from the atmosphere to the water and soil ecosystem. Polycyclic aromatic hydrocarbons (PAHs) in Taiyuan, China, are one class of the most hazardous air pollutants due to the high emission intensity from coal consumption. To better understand the PAHs removing from the atmosphere, 16 USEPA priority PAHs (except for naphthalene) in the particle dry deposition samples were detected from August 2013 to November 2014 at an urban site in Taiyuan. Dry deposition fluxes of particles were estimated as 157.44-358.17 mg/(m2·d), with the highest value in spring and lowest in autumn. Particle dry deposition fluxes of ∑15-PAHs ranged from 2436.20 to 14,967.36 ng/(m2·d), and was the highest in winter and lowest in summer. Higher PAHs particle dry deposition fluxes were related to higher PAHs emission, lower air temperature, less precipitation as well as wind speed. Overall dry deposition velocities of 15-PAHs were 0.056 ± 0.027 cm/s in winter and 0.42 ± 0.050 cm/s in summer, respectively, and high molecular weight PAHs showed low dry deposition velocities. Positive matrix factorization model's results indicated that coking, vehicle exhaust, coal combustion were the primary PAHs sources in particle dry deposition samples, accounting for 18.64%, 26.54% and 54.82% of total PAHs, respectively. The toxic equivalent concentrations (BaPeq) of ∑15-PAHs in particle dry deposition samples was in the range of 0.69-2.94 μg/g, which might be a good explanation to high soil PAHs concentrations reported in Shanxi province, China. Furthermore, this work could prove the significance of coal combustion, and related pollution control works are needed to conduct to alleviate the PAHs pollution situation.