能见度与颗粒物质量浓度之间的关系

Relationships Between Atmospheric Visibility and Particle Mass Concentrations

文章利用江苏省常州市和苏州市PM2.5质量浓度、PM10质量浓度、能见度和相对湿度的观测资料,研究了能见度与PM2.5质量浓度、PM10质量浓度之间的关系以及相对湿度的影响。结果表明,能见度随着PM2.5质量浓度的增大而减小,但减小的速度越来越慢,为了定量描述这种现象,文章定义了一个新的敏感性参数。能见度的减小速度存在一个临界点,该临界点把能见度与PM2.5质量浓度之间的关系分为2部分。这2部分的敏感性参数在常州相差27倍,在苏州则相差16倍。由于颗粒物吸湿增长的作用,临界点所对应的能见度和PM2.5质量浓度随着相对湿度的增大而减小,临界点两侧敏感性参数的差异增大。因此,相对湿度大的地区(如沿海地区)能见度的治理面临着更大的挑战,也拥有更好的机遇。此外,与粗粒子相比,细粒子对能见度的影响更显著。

This paper refers to studies on relationship between atmospheric visibility and mass concentrations of PM2.5 and PM10, as well as the impact of relative humidity. The studies focus on cities of Suzhou and Changzhou in Jiangsu Province, and meanwhile the relevant observations information concerning PM2.5 mass concentration, PM10 mass concentration, visibility and relative humidity in Changzhou and Suzhou has been obtained and examined. Results of the studies suggest that visibility decreases with increases of PM2.5 mass concentration; however, it has been found the decrease rate tapers off gradually. To de-scribe this phenomenon, a new sensitivity parameter has been defined. In fact, there is a threshold point in the decrease of vis-ibility, and this threshold point divides the relationship between visibility and PM2.5 mass concentration into two parts. The sensitivity parameter in one part of Changzhou is 27 times that in the other part and the sensitivity parameter in one part of Suzhou is 16 times that in the other part. Owing to the particle hygroscopic growth, threshold visibility and PM2.5 mass con-centration decrease with the increase of relative humidity. Therefore, areas with high relative humidity, e.g. the coastal areas,would face more challenges in pollution control to improve their visibility. In addition, it has been found in the studies that fine particles impair atmospheric visibility more than coarse ones.