天津冬季雾霾天气下颗粒物质量浓度分布与光学特性

年1—2月连续在线观测天津ρ(PM_2.5)、ρ(PM₁₀)、大气能见度、σ_sp(气溶胶散射系数)、σ_ap(气溶胶吸收系数)和AOD(大气光学厚度),结合气象资料,分析天津城区雾霾天气下的颗粒物质量浓度分布与光学特性. 结果表明:在为期52d的观测期间,发生雾日8d、轻雾日1d、霾日29d,雾霾日占观测时长的73%；霾日ρ(PM_2.5)/ρ(PM₁₀)为0.65,SSA(单次散射反照率)为0.95,MSE(气溶胶质量散射系数)为3.30m2/g,均高于非雾霾日,表明雾霾日下细粒子的散射作用是大气消光的主要贡献者；雾霾日的σ_sp和σ_ap均高于非雾霾日,随着霾等级增强,σ_sp和σ_ap逐渐增大,重度霾天气的σ_sp和σ_ap与中度霾天气相当,分析高RH可能是造成能见度进一步降低的主要因素；雾霾天气下AOD_500nm和波长指数均显著高于非雾霾天气,表明雾霾天气下气溶胶浓度远高于非雾霾天气,并且细粒子占主导地位. 

PM2.5 Pollution Characteristics and Aerosol Optical Properties during Fog-Haze Episodes in Tianjin

From January to February, 2013, there were some foggy and hazy days accompanied by serious air pollution in northern China. A study on the pollution characteristics of aerosols and their optical properties was conducted during this period in the urban area of Tianjing. Continuous online parameters including aerosol mass concentrations, atmospheric visibility, aerosol scattering and absorption coefficients, and aerosol optical depth (AOD) were obtained to analyze their variations and correlations, combed with simultaneous meteorological conditions. The results show that the weather factors were abnormal during the observation period, with relative humidity higher by 11%, wind speed lower by 0.5m/s, and more precipitation than under normal condition. The numbers of foggy, misty, and hazy days were 8,1, and 29, respectively, accounting for 73% of the total observed days. The average ratio of PM_2.5 PM₁₀ was 0.65; the single scattering albedo (SSA) was 0.95; and the aerosol mass scattering efficiency (MSE) was 3.30m2/g on the hazy days. These values were higher than those on non-foggy-hazy days, indicating that the scattering effects of fine particles were the main contributor to the atmospheric extinction. Both aerosol scattering and absorption coefficients were higher on fog-haze days than on non-fog-haze days; this result indicats that the high RH value had a great influence on visibility, may be even exceeding the influence of aerosol particle concentration on heavy haze days. Indices of AOD_500nm and aerosol wavelength were higher on foggy-hazy days than in non-foggy-hazy conditions, also indicating the predominance of fine particles on foggy-hazy days, when there were higher aerosol capacities.