西宁市大气污染来源和输送季节特征

在2016~2018年西宁市大气污染物PM₁₀和PM_2.5季节污染特征分析的基础上，利用HYSPLIT模式和GDAS资料计算了逐日72 h气流后向轨迹，通过聚类分析确定气流输送路径及其对日均PM₁₀和PM_2.5质量浓度的影响，运用TrajStat软件提供的潜在源贡献因子分析法（PSCF）和浓度权重轨迹分析法（CWT），探讨不同季节影响西宁市PM₁₀和PM_2.5质量浓度的潜在源区分布及贡献.结果表明，输送来源位置多分布在西宁的西-北方向和东-北方向，周边及邻近区域垂直高度较低.输送路径主要受西风、偏西风、西北、西南和偏东气流的影响.距离短、高度低和移速慢的气流轨迹出现概率最高，是最主要的输送路径，该路径在春夏秋三季来源于青海，冬季则源自新疆，省内输送占主导地位，且不同输送轨迹对PM₁₀和PM_2.5浓度影响不同.污染气流主要来自青海省内源、新疆外源及新疆以西的境外源，源地多沙漠和戈壁等脆弱地带分布.潜在源区范围及贡献大小有明显季节差异，冬季范围广且贡献最大，春秋次之，夏季最小.最主要潜在源区位于青海北部、中部和东部地区、新疆南部、中部和东部，其周边地区为中等贡献潜在源区.

Seasonal Characteristics of Air Pollutant Sources and Transport Pathways in Xining City

Based on the analysis of seasonal characteristics of PM₁₀ and PM_2.5 particle mass concentrations in Xining from 2016 to 2018, the daily 72 hour backward trajectories were calculated using the hybrid single-particle Lagrangian integrated trajectory (HYSPLIT) model and global data assimilation system (GDAS) data. The main transport pathways of PM₁₀ and PM_2.5 were identified and their characteristics were analyzed by clustering analysis for four seasons. The potential source regions and their contributions were defined using the potential source contribution function (PSCF) model and the concentration-weighted trajectory (CWT) method provided by TrajStat software. Results indicated that the sources were mostly distributed in the north-west and north-east regions and heights were low in the surrounding and adjacent areas of Xining. The transport pathways were mainly affected by airflows from the west, northwest, southwest, and east in Xining city. The trajectories with the highest probability of occurrence were characterized by short distance, low height, and slow-moving speed, originated from Qinghai in spring, summer and autumn, but from Xinjiang in winter, and was dominated by intra-provincial transportation. Different transport trajectories had different effects on PM₁₀ and PM_2.5 concentrations. Polluted airflows mainly originated from internal sources in Qinghai, external sources in Xinjiang, and foreign sources in the west of Xinjiang, with all the source regions located in deserts or Gobi areas. Obviously seasonal differences existed in the distribution and contribution of the potential source areas, with the widest and largest contribution in winter, followed by spring and autumn, and the smallest in summer. The most important potential source regions were located in northern, central, and eastern Qinghai, and southern, central, and eastern Xinjiang, while the surroundings were potential source regions for medium contribution.