兰州市沙尘天气污染特征及潜在源区

为了解兰州市沙尘天气期间大气污染特征，选取2016—2017年兰州市国家大气环境监测网络系统21个监测站点逐小时数据，对沙尘天气过程中的污染物特征进行分析。在此基础上，结合地面气象参数，运用HYSPLIT模型聚类计算和激光雷达观测等手段，对颗粒物来源和传输过程进行潜在源区贡献因子（PSCF）和浓度权重轨迹（CWT）分析。结果表明：兰州沙尘天气主要受西北方向、东偏北短距离传输、北部内蒙古路径3类气团影响，其中西北方向气团影响沙尘天气持续时间较长，沙尘过程中消光系数最高，环境空气质量转差显著，其他两类气团影响沙尘天气持续时间较短，有利于污染扩散；沙尘天气发生前期PM₁₀与气态污染物呈现正相关，沙尘天气过程中为负相关，沙尘天气后则再次转为正相关，沙尘天气对气态污染物浓度有降低效果；春季兰州地区颗粒物潜在区分布相对集中，主要来自于兰州西北部河西走廊，PSCF值大于0.7；冬季颗粒物潜在源区分布范围较广，PSCF值集中在0.7~0.9，其中对PM₁₀较大贡献区集中在新疆东南部，贡献值240~320 μg·m^-3。

Air pollution characteristics and potential sources in Lanzhou during dust weather

For understanding the changes of atmospheric pollutants during the dust weather in Lanzhou, The hourly monitoring data of the national atmospheric environment monitoring network system from 2016 to 2017 were selected to analyze the interannual variation trend of particulate matter. Combination with the ground meteorological parameters, using Hysplit model calculation, analysis the process of particulate matter sources and transmission, potential source area. The results show that the dust weather is mainly affected by three types of air masses, namely, The northwest, East by north short range transmission and Northern Inner Mongolia masses. Among them, the northwest air mass has a long duration, the highest extinction coefficient and significant deterioration of ambient air quality. The other two types of air masses affect the dust weather for a short duration, which facilitates the diffusion of pollution Before the occurrence of dust weather, PM₁₀ is positively correlated with gaseous pollutants; during the process of dust weather, PM₁₀ is negatively correlated; after sand dust weather, PM₁₀ becomes positively correlated again. In spring, the potential distribution of particulate matter is relatively concentrated, mainly from the Hexi corridor in the northwest of Lanzhou, and the PSCF value is greater than 0.7. In the winter, the potential source areas are widely distributed, and the PSCF value is mainly concentrated in the range of 0.7-0.9. The large contribution area to PM₁₀ is concentrated in the southeast of Xinjiang, and the contribution value is 240-320 μg·m^-3.