2014年5月武汉市输入型沙尘污染案例分析

结合地面颗粒质量浓度、金属元素含量、垂直消光系数和地面气象观测资料、后轨迹模型及天气分析图, 分析2014年5月25-26日湖北武汉市监测的沙尘天气过程。结果表明, 这次沙尘暴源起新疆南部塔卡拉玛干沙漠和内蒙巴丹吉林和腾格尔沙漠, 随着冷空气向东向南传输, 兰州和银川PM₁₀小时浓度分别超过2000 μg/m³ 和1000 μg/m³, 武汉PM₁₀小时浓度超过500 μg/m³, 沙尘在传输过程中逐渐减弱。沙尘期间武汉市以粗颗粒污染为主, PM₁₀浓度陡升, PM_2.5占PM₁₀ 的含量下降到约35%。沙漠粉尘示踪元素Ca, V, Ba和Fe 浓度增加4 倍以上, 所占的总量百分比也增加一倍以上, As, Se, Cr, Cu, Zn 和Pb 等当地的人为污染源排放的金属元素浓度约为先前的1/5~2/5, 所占总量百分比下降明显。激光雷达观测到两次明显的沙尘沉降过程, 在近地面层(500 m 左右)存在均匀的消光系数大值区(最大0.086 km^-1)。以此例说明结合气象和环境的多种观测手段综合分析输入型空气污染的方法。

Case Study of Wuhan Dust Pollution in May 2014

The dust event on May 25–26, 2014 in Wuhan Hubei province was studied by integrating multiplex information including mass concentration, metal element contents of atmospheric particle, vertical particle extinction, backward trajectory, surface meteorological parameters and synoptic analysis. The results show that the dust came from the sandstorm occurred in southern Xinjiang Taklamakan desert and Inner Mongolia Badan Jaran desert and Teng Ko Erh desert and then transported to east and south of China with cold air blowing. The PM₁₀ mass concentration decried along the trajectory, with hourly average exceeding 2000 μg/m³, 1000 μg/m³ and 500 μg/m³ in Lanzhou, Yinchuan and Wuhan respectively. During the dust event, coarse particle was dominant, PM₁₀ concentration increasing rapidly, and proportion of PM_2.5 to PM₁₀ decreased to about 35%. The concentrations of dust trace element Ca, V, Ba and Fe increased by about 4 times, percentages of the total element concentration doubled and the concentrations of As, Se, Cr, Cu, Zn and Pb from local anthropogenic sources were 1/5–2/5 of previous levels, percentages of the total element concentration decreasing significantly. Two evident dust deposition processes were recorded by Lidar, and the maximum area of extinction appeared near surface around 500 m with the max value at 0.086 km^-1. This paper pilots the analysis method of transporting air pollution using combination of meteorological and environmental measurements.