Abstract
Based on the PM2.5 and PM10 mass concentration data obtained from 51 national air quality monitoring stations and the corresponding rainfall intensity data in automatic meteorological stations in Hubei Province from 1 January 2015 to 31 December 2017, the impact of rainfall intensity on PM mass concentrations under relatively different humidity conditions was analyzed. The results showed that light rain occurred most frequently in the pollution process, with Xiangyang being affected for up to 587 h. PM concentration would not change drastically under the effect of precipitation. Mean rainfall intensity responsible for wet growth of PM10 and PM2.5 was mainly <0.5 mm/h, while that responsible for wet removal of PM2.5 was significantly higher (>1.4 mm/h) than that of PM10 (>1.0 mm/h). Precipitation was more likely to produce a wet removal effect for a greater initial value of PM mass concentration, and on the contrary, a wet growth effect was more likely, with the threshold of PM10 mass concentration being 150 μg/m3 and that of PM2.5 mass concentration being 95 μg/m3. Wet removal played a leading role in lower humidity (∼60%) and greater rainfall intensity, but wet growth played a leading role in higher humidity (∼90%) and lower rainfall intensity. As the precipitation level increased (rainfall ≥1.5 mm·h−1), the wet removal to PM10 mass concentration was enhanced more obviously. The variations of PM2.5 had similar distributions to those of PM10 under the effect of precipitation, but the wet removal effect of precipitation was weakened and the wet growth effect was enhanced.
Highlights
Atmospheric aerosols, the suspended systems of liquid or solid particles in the air, constitute an important part of the atmosphere [1,2,3] and are a key factor affecting environmental and climate change
Pollution weather occurs in one-third of days throughout the year in these two cities. ese two cities are typical representative areas affected by the transmission of an external pollution source and accumulation of a local pollution source. e heavy pollution weather in XY is often accompanied by a strong northerly wind and a weak inversion layer, whereas low wind speed and a multilayer inversion often occur in YC during heavy pollution weather [39, 40]
As heavy precipitation was usually concentrated in local areas, average deviation of occurrence in light rain (LR), moderate rain (MR), and heavy rain (HR) gradually increased, with 14.75%, 26.42%, and 35.01%, respectively. e greater the rainfall intensity was, the larger the difference in occurrence of precipitation was at national air quality monitoring stations in the same area, showing that the research on the separate occurrences of precipitation in different national air quality monitoring stations was reasonable
Summary
Effects of Rainfall on PM2.5 and PM10 in the Middle Reaches of the Yangtze River. Received 7 November 2019; Revised 26 January 2020; Accepted 4 July 2020; Published 21 July 2020. PM concentration would not change drastically under the effect of precipitation. Precipitation was more likely to produce a wet removal effect for a greater initial value of PM mass concentration, and on the contrary, a wet growth effect was more likely, with the threshold of PM10 mass concentration being 150 μg/m3 and that of PM2.5 mass concentration being 95 μg/m3. Wet removal played a leading role in lower humidity (∼60%) and greater rainfall intensity, but wet growth played a leading role in higher humidity (∼90%) and lower rainfall intensity. As the precipitation level increased (rainfall ≥1.5 mm·h−1), the wet removal to PM10 mass concentration was enhanced more obviously. E variations of PM2.5 had similar distributions to those of PM10 under the effect of precipitation, but the wet removal effect of precipitation was weakened and the wet growth effect was enhanced
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