两湖盆地襄阳地区PM_(2.5)重污染过程区域传输的观测和模拟分析

Observation and simulation analysis of regional PM_(2.5) transport in heavy air pollution process in Xiangyang Area over the Twain-Hu Basin

两湖盆地位于华中地区,横跨湖北、湖南两省,海拔高度低于200 m.襄阳为华中地区两湖盆地的“风口”,PM_(2.5)污染严重.为认识襄阳地区大气环境变化特征,对其2016年1月的大气污染过程进行研究分析,研究气象条件对PM_(2.5)浓度的影响.结果表明:冷空气南下入侵对两湖盆地襄阳地区产生PM_(2.5)重污染有重要驱动作用.强风是驱动大气污染物区域传输的主要因素,受东亚冬季风影响,上风方的PM_(2.5)跨区域传输到下风方两湖盆地,导致襄阳地区的PM_(2.5)污染水平上升.基于FLEXPART-WRF模式,定量估算了2016年1月襄阳地区4次PM_(2.5)重污染过程的区域传输贡献,估算发现4次大气重污染过程的外源贡献率均高于50.0%,最高达80.3%,体现了大气污染物区域传输对两湖盆地大气重污染事件的主导作用.两湖盆地襄阳地区PM_(2.5)污染主要潜在源来自东北路径,以华北平原为主.

The Twain-Hu basin(THB)is located in Central China,covering the lowland(mainly less than 200 m a.s.l.)acorss Hubei and Hunan provinces.Xiangyang is the"tuyere"in the northwestern mouth of THB in Central China with serious PM_(2.5)pollution.In order to understand the variations of atmospheric environment in Xiangyang,the PM_(2.5)pollution processes in January 2016 were analyzed to explore the effects of meteorological conditions on PM_(2.5)concentrations.The results showed that the southward cold air mass droven regional transport of PM_(2.5)from upwind regions to the THB.Strong wind is the main factor in driving the regional transport of air pollutants.Governed by the East Asian winter monsoon,PM_(2.5)emitted from the upstream regions was transported to the downwind areas(Xiangyang),leading to the rising PM_(2.5)concentrations in Xiangyang.Based on the FLEXPART-WRF model,we quantitatively estimated the contribution of regional PM_(2.5)transport to four heavy PM_(2.5)pollution processes over Xiangyang in January 2016.The contribution rates of four heavy PM_(2.5)pollution events all exceeded 50.0%,with maximum contribution of 80.3%,indicating the leading role of regional PM_(2.5)transport in worsening air quality of the THB.The main sources of PM_(2.5)pollutant in Xianguyang,the THB were from the northeasterly direction,mainly the North China Plain.