2010年民勤沙地近地面沙尘气溶胶浓度特征

为了更好地研究沙尘气溶胶起沙和输送特征，2010年4—5月，在民勤周边沙地利用EZ LIDAR ALS300&ALS450型激光雷达和 GRIMM 180型颗粒物采样器进行了大气气溶胶的外场连续观测，取得了晴天、浮尘、扬沙和沙尘暴天气条件下沙尘气溶胶总后向散射垂直剖面图和PM₁₀、PM_2.5、PM_1.0质量浓度采样资料，其中包含“0424”特强沙尘暴过程资料。结果表明：春季民勤近地层大气中沙尘气溶胶浓度较高，且随气象要素的变化很大；在整个观测期内，PM₁₀、PM_2.5、PM_1.0的平均质量浓度分别为202.3、57.4 μg/m³、16.7 μg/m³。在不同天气条件下，PM₁₀、PM_2.5、PM_1.0质量浓度的变化有很好的相关性，但变化趋势有所不同。在沙尘暴天气条件下，PM₁₀的日平均质量浓度高达2469.1μg/m³，是背景天气条件下PM10日平均质量浓度的100多倍，是浮尘天气条件下PM10日平均质量浓度的8倍，是扬沙天气条件下PM₁₀日平均质量浓度的2倍。PM_2.5在沙尘暴天气下日平均质量浓度为460.3 μg/m³，是背景天气条件下PM_2.5日平均质量浓度的45倍，是浮尘天气条件下PM_2.5日平均质量浓度的6倍，是扬沙天气条件下PM_2.5日平均质量浓度的1.4倍。PM_1.0在沙尘暴天气条件下的日平均浓度为92.7 μg/m³，是背景天气条件下PM_1.0日平均浓度的13倍，是浮尘天气条件下PM_1.0日平均浓度的7倍，是扬沙天气条件下PM_1.0日平均浓度的1.3倍。可见，风速增大时沙尘粒子浓度的增加对粒子粒径是有选择的，小粒子比重随沙尘浓度增加而相对减小，大粒子比重随沙尘浓度增加而相对增多；通过对“0424”特强沙尘暴过程的研究表明，一次沙尘暴过程往往包括沙尘暴、扬沙和浮尘天气中的两种类型；通过对激光雷达数据分析发现，在强沙尘暴发生过程当中，民勤沙地发生了非常严重的风蚀起沙现象。

Concentration characteristics of sand dust aerosol in atmospheric boundary layer in 2010 at Minqin, Gansu Province

In order to study transportation and outbreak mechanism of sand dust particles, the aerosol particles were continuously sampled from April to May in 2010 at Minqin of Gansu Province using a laser radar (EZ LIDAR ALS300&;ALS450 type) and a particulate sampler instrument (GRIMM 180). The altitude-orbit cross section of total backscattering of sand dust aerosol and mass concentrations of PM₁₀, PM_2.5 and PM_1.0 were analyzed under clear, floating dust, blowing dust and sandstorm weather conditions, including the extremely strong sandstorm process occurring on 24 April (0424). The results show that the concentrations of sand dust aerosol are high in spring near the ground surface layer in the study area. The concentration changes largely with variation of some meteorological elements. Mean mass concentrations of PM₁₀, PM_2.5 and PM_1.0 are 202.3μg/m³, 57.4 μg/m³ and 16.7 μg/m³ respectively during the observational period. The correlation among PM₁₀, PM_2.5 and PM_1.0 is significant under the different weather conditions, while variation trends of these variables are different. The mean daily mass concentration of PM₁₀ reaches 2469.1μg/m³ under sandstorm weather, and this is about 100 times higher than that under normal weather condition, 8 times higher than under floating dust condition and 2 times higher than under blowing sand condition. The concentration of PM_2.5 is 460.3 μg/m³ under sandstorm weather, and it is about 45 times higher than that under normal weather condition, 6 times higher than under floating dust weather and 1.4 times higher than under blowing dust weather. That of PM_1.0 is 92.7μg/m³ under sandstorm weather, which is 13 times higher than under normal weather condition, 7 times higher than under floating dust weather and 1.3 times higher than under blowing dust weather. It is seen that the dust particle concentration increases with the increase of wind speed, but small particle proportion decreases and large particle proportion increases with the increase of dust concentration. Analysis of the “0424” strong sandstorm process reveals that a sandstorm process usually includes two types of sandstorm,blowing dust and floating dust. The analysis of lidar data indicates that the serious dust wind erosion occurs at Minqin during the sandstorm.