中文摘要：

分别于冬季和夏季采集了北京、天津和秦皇岛3个城市，遵化、沧县、涞源和张北4个县城以及两处人为活动较少的背景地区降尘样品，分析了降尘量及降尘中多环芳烃含量，据此计算了各样点多环芳烃干沉降通量．结果表明，所研究城市夏季和冬季多环芳烃平均沉降通量分别为（6．3±7．4）μg·m^-2·d^-1和（16．4±14．9）μg·m^-2·d^-1，县城为（2．2±0．9）μg·m^-2·d^-1和（16．3±3．8）μg·m^-2·d^-1，对照点明显低于城镇，两季多环芳烃沉降通量分别为（1．0±0．3）μg·m^-2·d^-1和（I．6±0．7）μg·m^-2·d^-1．两季节获得的所有样点多环芳烃干沉降通量与降尘量显著相关，若分季节统计，相关性更加明显，且冬季降尘中多环芳烃含量显著高于夏季．由此可见，对多数样点而言，导致其多环芳烃干沉降通量差别的首要因素是降尘量，其次为季节差异．仅个别数据（夏季秦皇岛）表现出不同．降尘中多环芳烃成分谱具有明显的季节差异，城市与县城冬季降尘中菲的相对含量显著高于夏季．不同类型样点间差别较小，表现出区域性趋同现象，同种类型样点之间的多环芳烃成分谱则非常一致．

英文摘要：

Dry deposition samples were collected from a number of sites in Northern China, which can be categorized into cities （Beijing, Tianjin and Qinhuangdao） , towns （Zunhua, Cangxian, Laiyuan and Zhangbei） and controls. The samples were collected in both winter and summer seasons. Polycyclic aromatic hydrocarbons （PAHs） in the deposition samples in summer and winter were analyzed to calculate the dry deposition fluxes of PAHs at these sites. The measured dry deposition fluxes were （6.3 ±7.4）μg·m^-2·d^-1 and （16.4±14.9）μg·m^-2·d^-1 for the cities, （2.2 ±0.9）μg·m^-2·d^-1 and （ 16.3 ± 3.8 ）μg·m^-2·d^-1 for the towns and （ 1.0± 0.3 ）μg·m^-2·d^-1 and （ 1.6 ± 0.7 ） μg·m^-2·d^-1 for the control sites, respectively. The PAHs fluxes of deposition were significantly correlated to particle flux and the relationship was seasonally dependent, with a higher mass concentration of PAHs in winter than in summer. There was only a single outlier which did not follow such a deposition-seasonality pattern. The composition profiles of PAHs also showed seasonality with significantly higher relative abundance of phenanthrene in winter than that in summer. There was similarity in the composition profile among site categories indicating a regional convergence due to dispersion and long-range transport.