灰霾污染和清洁过程中污染物垂直结构特征

针对无锡地区2013年11月6—13日经历的灰霾污染和清洁过程,采用地基遥感激光雷达对空气中的气溶胶颗粒物垂直分布进行垂直探测,发现污染时段气溶胶颗粒物主要积聚在1.8 km以下,消光系数的日均值统计表明,从近地面至高空1.5 km,颗粒物产生的峰值消光系数稳定在0.2 km~(-1);而清洁时段,由于垂直扩散条件改善,颗粒物随高度增加明显减少,1.5 km处的消光系数不足0.05 km~(-1)。同时发现污染时段中,近地面PM_(10)、PM_(2.5)、碳黑(BC)的平均浓度分别是清洁时段的2.48、2.76、3.66倍;大气氧化剂(O3和NO_x的总和)平均值水平是清洁时段的1.73倍。气象条件分析发现,锋面的移动使大气水平、垂直对流运动加剧,污染物得以迅速扩散,空气质量转好,这也是此次污染清除的主要原因。

The Vertical Characteristics of Pollutants during Haze and Clear Stages

For a haze-to-clear process in Wuxi city from Nov. 6^th to 13^th 2013, the vertical aerosol distribution characteristics has been explored by particulate remote sensing LiDAR. The results showed that aerosol mainly stayed within 1.8 km, and daily-averaged extinction coefficient was always 0.2 km^-1 from ground level to 1.5 km during haze episodes. But the aerosol was reduced along with altitude increasing in clear stage. The daily averaged extinction coefficient was below 0.05 km^-1 at 1.5 km. The concentrations of PM₁₀, PM_2.5 and black carbon (BC) at ground during haze days have been proved 2.48 times, 2.76 times and 3.66 times as much as those in the clear stage. The mean concentration of oxidants in the air, O₃+NO_x, was 1.73 times compared with that in the clear stage. It was a strong evidence of the urban atmospheric complex pollution. The analysis of meteorological conditions has showed that the rapid movement of cold-front from North to South gave rise to good diffusion situation in horizontal and vertical direction. It was the significant factor leading to the "Good" air quality stage.