中文摘要：

于2013年冬季在天津大气边界层观测站利用Andersen撞击式采样器采集了26 d的颗粒物样品,并进行化学组分分析,同步观测颗粒物吸收系数、数浓度、能见度及其他气象要素.对比分析了污染日和清洁日颗粒物质量浓度及其化学组成的粒径分布特征,在此基础上,利用Mie模型计算外混、内混、＂核-壳＂3种混合态假设下颗粒物的消光系数、散射系数和吸收系数.与实测吸收系数的比较可知,颗粒物的混合态可能更加接近＂核-壳＂态.＂核-壳＂态假设下颗粒物平均消光系数模拟值为（517.44±308.42）Mm-1,其中污染日平均值为（668.39±307.30）Mm-1,清洁日为（275.91±37.90）Mm-1,相对湿度对颗粒物的消光系数有显著影响.污染日颗粒物中OM（有机质）、（NH4）2SO4、NH4NO3、EC和其他物质对消光系数的贡献率分别为30.4%、25.5%、17.7%、8.1%和18.3%,清洁日分别为49.8%、11.0%、7.2%、10.6%和21.4%.PM0.4～1.1、PM〉1.1～2.1、PM〉2.1～10的消光系数贡献率分别为69.6%±6.7%、13.9%±3.3%和16.5%±6.4%.污染日高浓度的细粒子是导致能见度下降的主要原因,其中亚微米颗粒物对消光占据主导地位,（NH4）2SO4、NH4NO3、OM是主要的消光化学组分.

英文摘要：

Size-resolved samples were collected by an Andersen cascade impactor for 26 days at the atmospheric boundary layer observation station in Tianjin during winter 2013. The concentrations of organic carbon,elemental carbon and water-soluble ions in PM were measured. Additionally,absorbing coefficients,particle number size distribution,visibilities and meteorological parameters were also determined to better understand and compare the characteristics of particles and their components in polluted and clear days. Moreover,the Mie model was applied to simulate the aerosol optical properties under dry and wet conditions when elemental carbon was under different situations,including external mixture,internal mixture and ＂core-shell ＂ mixture. By comparing the measured absorbing coefficients with the modeled ones（ i. e.,in external mixture,internal mixture and ＂core-shell ＂mixture）,it was founded that the ambient particles seem to be more similar to core-shell mixtures. The result showed that the average extinction coefficient for＂core-shell＂mixture at 550 nm was（ 517. 44 ± 308. 42） Mm- 1over the whole period,and（ 668. 39 ± 307. 30） Mm- 1on polluted days and（ 275. 91 ±37. 90） Mm- 1on clear days. The relative humidity significantly affected light extinction. The contributions of OM,（ NH4）2SO4,NH4NO3,EC and others to light extinction were 30. 4%,25. 5%,17. 7%,8. 1% and 18. 3% on polluted days,and 49. 8%,11. 0%,7. 2%,10. 6% and 21. 4% on clear days. The contributions of PM0. 4-1. 1,PM 1. 1-2. 1,PM 2. 1-10 to light extinction were 69. 6% ±6. 7%,13. 9% ± 3. 3% and 16. 5% ± 6. 4%,respectively. The results showed that high levels of fine particles were the main cause of visibility impairment. Submicron particles contributed much more to light extinction,and（ NH4）2SO4,NH4NO3,and OM were the main components causing light extinction.