高湿背景下重庆地区PM2.5的吸湿特性及其光学效应研究

作为“一带一路”和长江经济带的西部中心枢纽，川渝地区的大气霾污染治理面临瓶颈，制约区域经济发展及其对外开放的国际影响力，并危及三峡库区脆弱的生态气候。颗粒物的吸湿增长会改变其光学和辐射特性，影响PM2.5的二次生成与转化，特别在高湿环境中作用显著。因特殊的地形与高湿气候，川渝的PM2.5吸湿特性与时空分布、霾污染影响机制或独具特点，但目前川渝欠缺PM2.5吸湿特性尤其是高湿下的研究。故本项目拟基于国际先进的颗粒物加湿测量技术，在重庆开展RH≥85%高湿下PM2.5粒径与光学吸湿特性的高时间分辨率季节性测量实验，系统获取重庆地区霾颗粒吸湿及光学特性的总体变化规律；推算颗粒物液态水含量，探讨吸湿与化学特性的联系，表征不同组分的吸湿贡献及光学影响；针对性提出一套川渝适用的吸湿性分类参数化方案，以提高气候效应评估的准确性。研究结果将增进对大气复合污染变化机制的理解，为大气污染综合防治提供科学参考。

As the central hub of both ‘the Belt and Road Initiative’ and ‘Yangtze River Economic Belt’ in western China, Sichuan-Chongqing area is stuck in regulating the atmospheric haze pollution, restricting the regional economic development and the cities’ international influences in opening-up, and endangering the sensitive ecological climate of Three Gorges Reservoir Area. The hygroscopic growth of aerosol particles can change the optical and radiative properties, and affect the secondary formation and transformation of PM2.5, in particular for high relative humidity (RH) conditions. Due to the unique topography and high RH environment, the hygroscopic properties of PM2.5 with their spatiotemporal variation, as well as the influence mechanisms of atmospheric haze pollution in Sichuan-Chongqing area, could differ significantly from other Chinese megacities. Nevertheless, investigations on the hygroscopic properties of PM2.5 especially for high RH conditions in Sichuan-Chongqing area are quite limited. In this sense, this project plans to conduct high-time-resolution seasonal observations of aerosol size- and optical-hygroscopic properties at high RH conditions (e.g., RH≥85%) with the advanced aerosol hygroscopic growth measurement techniques in Chongqing, aiming to obtain the general variation of hygroscopic properties and optical characteristics of haze particles in Chongqing. Based on the hygroscopic measurements, the relating aerosol liquid water content will be estimated. In addition, the relationship between aerosol hygroscopic properties and corresponding chemical characteristics will be discussed, and the contributions of different chemical constituents to the bulk hygroscopicity and related optical properties will be quantified. Further, a case-dependent parameterization of aerosol hygroscopicity will be proposed for Sichuan-Chongqing area, which could be applied in climate models thus enhancing the evaluation accuracy of aerosol climate forcing. Results from this project will also facilitate understanding in the formation and evolution of coupled atmospheric pollution, thereby providing useful scientific references for the comprehensive treatment of air pollution.