Hysteretic effects of meteorological conditions and their interactions on particulate matter in Chinese cities.

Particulate matter (PM) has become the main air pollutant in most cities of in China, which greatly threatens the human health. Numerous studies have reported that PM concentrations could be accurately predicted from previous days' meteorological conditions. However, the hysteretic or lagged effects of meteorological factors on PM concentrations are not clear. In this study, the GeoDetector q statistic method was used to quantify the hysteretic influences of meteorological conditions and their interactions on concentrations of PM 2.5 (particles < 2.5 μm in aerodynamic diameter) and PM 10 (particles < 10 μm in aerodynamic diameter) and the ratio of PM 2.5 to PM 10 (PM 2.5 /PM 10) at multiple spatial and temporal scales in China. We found that the temperature, precipitation, and relative humidity had primary impacts on PM 2.5 concentrations, PM 10 concentrations, and the PM 2.5 /PM 10 ratios, respectively, at both national and annual time scales. At the seasonal time scale, precipitation and relative humidity had hysteretic effects on PM concentrations in spring and summer, respectively. Moreover, precipitation and wind speed were dominant hysteretic factors in autumn and winter, respectively. At the regional scale, the dominant hysteretic effects of meteorological factors showed large variations across all regional subdivisions. The interactions between any two meteorological factors had an enhanced hysteretic effect on PM concentrations compared to a single factor. These findings could help us to develop scientific measures to reduce the emissions of air pollution and improve the performance of air pollution prediction models. Image 1 • Hysteretic effects of meteorological factors on particulate matter were identified. • Temperature, rainfall, and humidity are main lagged factors of particulate matter. • Regional and seasonal variations of hysteretic factors were identified in China. • Urgent need to explore mechanisms of lagged effects of meteorological factors on PM. [ABSTRACT FROM AUTHOR]