Shu Xi, Qiao Xue, Tang Ya, Hopke Philip K, Ying Qi, Wang Junfeng, Han Bin, Xu Zhongjun, Xia Zhonglin, Ma Yinhong, Dai Yuan, Leng Jun
Institute of New Energy and Low-Carbon Technology, Sichuan University, No. 24, South Section One, First Ring Road, Chengdu, 610065, Sichuan, China.
Institute of New Energy and Low-Carbon Technology, Sichuan University, No. 24, South Section One, First Ring Road, Chengdu, 610065, Sichuan, China.
J Environ Manage. 2025 Sep;391:126564. doi: 10.1016/j.jenvman.2025.126564. Epub 2025 Jul 14.
Urbanized basins are widely recognized as hotspots of particulate matter (PM) pollution. Characterizing the vertical stratification of PM in these regions is essential to elucidate the influence of regional air pollutant transport, dynamics of planetary boundary layer, and pollution-meteorology feedbacks. Using Mount Emei (500-3100 m a.s.l.) as a natural observation tower, this study investigated the composition and sources of PM, along with the six criteria pollutants (PM, PM, O, SO, CO, and NO) across three atmospheric layers within the Sichuan Basin (SCB). The monitoring sites are located in the planetary boundary layer (M-base: 550 m a.s.l.), the cloud/fog-active layer (M-upper: 2400 m a.s.l.), and the free troposphere (M-summit: 3100 m a.s.l.). The results revealed that PM at M-base exhibited typical urban pollution characteristics, with SNA (i.e., SO, NO, and NH) accounting for ∼60 % of total suspended particles (TSP) mass annually, primarily driven by anthropogenic emissions. Autumn/wintertime PM extremes at M-base resulted from the synergistic effects of increased emissions, stagnant meteorology, and enhanced aqueous-phase reactions under high relative humidity (>80 %). As altitude increased, PM concentrations declined, primarily due to more effective wet scavenging and reduced anthropogenic influence. At M-upper and M-summit, the contributions of SNA reduced to ∼35 % of TSP mass annually, whereas contributions from biomass burning and crustal dust increased. Unlike M-base, PM concentrations at M-summit peaked in spring, primarily due to transboundary influences, particularly the biomass burning in neighbouring countries and dust from Gobi/desert in northwestern China. Overall, the deep-basin topography imposed three regulatory mechanisms on PM pollution, including ground-level PM enhancement through chemical-meteorological interactions, upper-altitude cloud/fog/precipitation and PM interactions, and dominance of transboundary pollutant transport in the upper/free-troposphere. This study provides a mechanistic basis for vertically stratified air quality management in the SCB, as well as other similar terrain regions worldwide.
城市化流域被广泛认为是颗粒物（PM）污染的热点地区。了解这些地区PM的垂直分层对于阐明区域空气污染物传输、行星边界层动力学以及污染-气象反馈的影响至关重要。本研究以峨眉山（海拔500 - 3100米）作为天然观测塔，调查了四川盆地（SCB）内三个大气层中PM的组成和来源，以及六种标准污染物（PM、PM、O、SO、CO和NO）。监测站点位于行星边界层（M-底部：海拔550米）、云/雾活跃层（M-上部：海拔2400米）和自由对流层（M-山顶：海拔3100米）。结果表明，M-底部的PM呈现出典型的城市污染特征，硫氮化合物（即SO、NO和NH）每年占总悬浮颗粒物（TSP）质量的约60%，主要由人为排放驱动。M-底部秋冬季节的PM极值是由排放增加、气象停滞以及高相对湿度（>80%）下增强的水相反应的协同作用导致的。随着海拔升高，PM浓度下降，主要是由于更有效的湿清除作用和人为影响的减少。在M-上部和M-山顶，硫氮化合物的贡献降至每年TSP质量的约35%，而生物质燃烧和地壳尘埃的贡献增加。与M-底部不同，M-山顶的PM浓度在春季达到峰值，主要是由于跨界影响，特别是邻国的生物质燃烧以及中国西北部戈壁/沙漠的沙尘。总体而言，盆地深处的地形对PM污染施加了三种调节机制，包括通过化学-气象相互作用增强地面PM、高空云/雾/降水与PM的相互作用以及上自由对流层中跨界污染物传输的主导作用。本研究为SCB以及全球其他类似地形区域的垂直分层空气质量管理提供了机制基础。
