2006年春季沙尘天气下背景地区大气气溶胶光学特性的观测研究

Observational Study of Aerosol Extinction Property during Dust Weather in Background Area

利用2006年3～5月北京上甸子本底站气溶胶细粒子（PM2．5）质量浓度、吸收和散射系数的连续观测资料，对2006年春季上甸子本底站清洁、污染输送及典型沙尘天气下气溶胶的消光特性进行了分析。结果显示：①本底站在春季清洁情况下PM2．5质量浓度、吸收和散射系数的日均值水平分别为：10μg／m^3、7Mm^-1和20Mm^-1左右，单散射反照率分布在0．71～0．78之间；此次观测到的污染输送过程中PM2．5质量浓度、吸收和散射系数平均值分别为：145μg／m^-3、44．5Mm^-1、374．3Mm^-1，单散射反照率分布在0．84～0．94之间；沙尘影响期间，PM2．5质量浓度、吸收和散射系数以及单散射反照率的测量结果分布在248．2～424．1μg／m^3、10．8～44．7Mm^-1、225．4～392．5Mm^-1和0．89～0．96之间。②观测得出，沙尘影响集中的时段细粒子质量浓度、气溶胶散射系数和气溶胶吸收系数都成倍地上升，其中质量浓度和散射系数上升的幅度要高于吸收系数。③3种天气条件的对比结果显示，受沙尘天气影响PM2．5质量浓度明显上升，且逐时波动幅度大；吸收系数远高于清洁天气下的观测结果，但比污染输送过程的测量结果偏低；散射系数同样高于清洁天气下的观测结果，与污染输送情况下的测量结果接近。沙尘天气导致颗粒物浓度明显上升，其对气溶胶粒子散射作用的贡献要大于吸收作用。

Using the continuous data of PM2. 5 mass concentration, aerosol absorbing and scattering coefficients collected during March and May 2006 at the Shangdianzi background station, a primary study of the optical properties of aerosol in sand-dust weather is conducted. The results indicate： （1） In the selected clear days, the value of PM2.5 mass concentration and daily average absorbing and scattering coefficients were about 10 μg/m^3, 7 Mm ^-1, 20 Mm^-1, respectively. The value of single-scattering albedo ranged from 0.71 to 0.78. During the transportation of pollutants from urban area to the background station, the average PM2.5 mass concentration, absorbing and scattering coefficients were 145 μg/m^3, 44.5 Mm^- 1, and 374.3 Mm^-1. The value of single scattering albedo ranged from 0.84 to 0.94. While in sand-dust weather, the value of PM2.5 mass concentration, aerosol absorbing and scattering coefficients, single scattering albedo ranged from 248.2 μg/m^3 to 424.1 μg/m^3 , 10.8 Mm^-1 to 44.7 Mm^-1 , 225.4 Mm^-1 to 393. 9 Mm^-1, and 0. 89 to 0. 96, respectively. （2） Affected by the sand-dust weather, the increasing ranges of aerosol mass concentration and scattering coefficients were much greater than that of absorbing coefficient. （3） Through comparing the results from the three kinds of weather, it is found that the sand-dust weather made the concentration of particles increase up to an abnormally high value and fluctuate greatly in a short time. The absorbing coefficient of aerosol in sand-dust weather was much higher than in clear days but lower than during the pollutant transporting process from urban area to background station. The scattering coefficient of aerosol in sand-dust weather was much higher than in clear days, close to that during the pollution case. The sand-dust weather contributed to the scattering effect more greatly than to the absorbing effect of aerosol.