长治市沙尘天气污染特征及传输路径解析

以2018年3次沙尘天气为研究对象，分析了PM_2.5和PM₁₀浓度、水溶性离子组分、气象条件和气溶胶光学特征，研究了长治市沙尘天气的典型污染特征和传输路径.结果表明：长治市2018年共8d为受沙尘天气影响日，其中4月份最多（5d），这与春季大气环流调整，冷暖空气活动频繁有关.沙尘污染发生前一般受西方或西北方冷空气影响，大气层结不稳定，大气环流转为经向环流，平均风速达4m/s以上；沙尘污染过程中PM_2.5/PM₁₀均低于0.3，环境空气中粗颗粒物占比较大，水溶性离子总浓度在PM_2.5中占比下降，Ca²⁺浓度为沙尘污染发生前的4倍以上.冬季沙尘为近地面扩散传输，春夏季沙尘为高空沉降传输，影响范围大，区域传输贡献明显.长治市沙尘重要潜在源区为蒙古国、哈萨克斯坦中部和新疆中北部的荒漠地区，传输路径主要为西北路径和正北路径，其中西北路径为哈萨克斯坦—新疆中北部—内蒙古西部—长治以及新疆中北部—内蒙古西部—长治两条路径，正北路径为蒙古国—内蒙古中部—山西北部—长治.

Analysis of dust weather pollution characteristics and transmission paths in Changzhi,China

Three dust pollution processes in Changzhi were investigated. Typical pollution characteristics and transmission paths of dust weather in Changzhi were studied through analyzing the PM_2.5 and PM₁₀ concentrations, water-soluble ion components, meteorological conditions and aerosol optical characteristics. There were 8 days of dust weather in Changzhi in 2018. April was the most serious polluted month with 5days of dust weather and this was related to the adjustment of atmospheric circulation in spring and the frequent activities of warm and cold air. Before the occurrence of dust weather, atmosphere in Changzhi was affected by the cold air from west or northwest. The atmospheric stratification was unstable and the atmospheric circulation turned into meridional circulation, with an average wind speed of more than 4m/s. During the dust pollution process, the ratio of PM_2.5/PM₁₀ was lower than 0.3. The coarse particles made up a large part in the ambient air. The proportion of total water-soluble ions in PM_2.5 was decreased, and the concentration of Ca²⁺ was 4times higher than that before dust pollution. The dust was transported near the ground in winter, while transported at high altitude in spring and summer. The important potential sources of dust in Changzhi city were desert areas in Mongolia, central Kazakhstan and central and northern Xinjiang. The transmission paths were generally northwest path and northern path. There were two routes in the northwest path:Kazakhstan-north central Xinjiang-west Inner Mongolia-Changzhi and north central Xinjiang-west Inner Mongolia-Changzhi. The northern route was Mongolia-central Inner Mongolia-northern Shanxi-Changzhi.