Abstract
China has suffered from severe particulate matter (PM) pollution in recent years. Both pollution areas and levels are increasing gradually. The PM pollution episodes not only occur in the traditional developed areas like the Yangtze River Delta (YRD) and the Beijing-Tianjin-Hebei (BTH) region, but also frequently happen in the eastern coastal provinces (ECPs) of China. Based on hourly fine-PM (PM2.5) concentrations during December 2013 to February 2014 of 55 cities located in the ECPs, we investigated the spatial and temporal variabilities of PM2.5 concentration and the corresponding meteorological conditions during winter. The results generally showed that the winter mean concentrations over all ECPs exceeded China’s national standard of 75 µg m–3, and the most polluted areas with mean concentrations exceeding 150 µg m–3 were in the southwest of Hebei and the west of Shandong Province. The PM2.5 concentrations in February were lower than December in most areas, especially in the YRD, but they were higher over the north of Hebei Province. The spatial distributions and monthly variations were strongly related to weather conditions. Overall, severe PM pollution corresponded with stable weather conditions: small Sea Level Pressure gradient, lower Planetary Boundary Layer (PBL) height and weaker winds. Statistics showed that the changes of the mean PM2.5 concentration over the ECP region lagged behind the variations in the PBL height and wind speeds by about 12–18 h, and the variations in weather conditions could explain about 71% (R2) of the overall changes in PM2.5 concentrations, indicating that regional PM2.5 pollution was dominated by weather conditions in the ECPs. This study gives insight into the PM2.5 pollution in the ECPs of China during winter, which would be helpful to predict and control the PM2.5 pollution for this area in the future.
Highlights
China has been suffering from severe particulate matter (PM) pollution in recent years, especially in winter (Chan and Yao, 2008; Liao et al, 2014; Wang et al, 2014d)
Statistics showed that the changes of the mean PM2.5 concentration over the eastern coastal provinces (ECPs) region lagged behind the variations in the Planetary Boundary Layer (PBL) height and wind speeds by about 12–18 h, and the variations in weather conditions could explain about 71% (R2) of the overall changes in PM2.5 concentrations, indicating that regional PM2.5 pollution was dominated by weather conditions in the ECPs
Among the 114 cities, 60% of those with PM2.5 > 75 μg m–3 were located in the ECPs, and for those with PM2.5 > 150 μg m–3, 71% were in the ECPs
Summary
China has been suffering from severe particulate matter (PM) pollution in recent years, especially in winter (Chan and Yao, 2008; Liao et al, 2014; Wang et al, 2014d). These studies identified that stable weather conditions including uniform pressure field, low boundary layer height and weak wind were major reasons for severe air pollution.
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