Weather Condition Dominates Regional PM_2.5 Pollutions in the Eastern Coastal Provinces of China during Winter

摘要

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 (PM_(2.5)) concentrations during December 2013 to February 2014 of 55 cities located in the ECPs, we investigated the spatial and temporal variabilities of PM_(2.5) 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 PM_(2.5) 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 PM_(2.5) 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 PM_(2.5) concentrations, indicating that regional PM_(2.5) pollution was dominated by weather conditions in the ECPs. This study gives insight into the PM_(2.5) pollution in the ECPs of China during winter, which would be helpful to predict and control the PM_(2.5) pollution for this area in the future.