The impact of synoptic circulation on air quality and pollution-related human health in the Yangtze River Delta region

摘要

PM_(2.5) and O_3 pollution are of concern for the Yangtze River Delta (YRD) region due to their adverse impact on human health. In conjunction with a complex distribution of emission sources, the synoptic circulation conditions control the temporal and spatial variability of air pollution levels and hence the pollution-related health burdens. In this study, a long-term synoptic circulation catalogue is developed by applying the automated Lamb weather type method to the ECMWF mean sea level pressure reanalysis for the YRD region during 2013-2016. Ten typical circulation types are examined in relation to the transport pathways and diffusion conditions, and then multi-site surface observations of PM_(2.5) and O_3 are composited for different circulation conditions. The results show that each circulation type is characterized with distinct air mass origin, diffusion condition and air quality level. The anticyclonic type (Type A) corresponds to the highest regional PM_(2.5) concentration (68.5 ug/m~3) due to the subsidence flow and long-range transport, while the westerly types (Types SW, W and NW) correspond to the higher regional maximum daily 8-h running average O_3 (MDA8 O_3) concentration (> 100 µg/ m~3) due to favorable local meteorological conditions. Regional transport causes an east-high and west-low PM_(2.5) distribution in westerly types but a west-high and east-low PM_(2.5) distribution in easterly types (Types SE, E and NE). In contrast, nearly all the types show an east-high and west-low O_3 distribution, suggesting the predominated impacts of precursor emissions. By using established exposure-response functions, the health impact assessment (HIA) shows that Type W poses the greatest public health risk with mean daily excess mortality of 77.3 (95% CI: 61.9,92.6) deaths and O_3 pollution accounts for approximately 70% of this health burden.