汾渭平原空气质量的时空特征及其与气象因子的关系

Spatiotemporal characteristics of air quality and their relationships with meteorological factors over the Fenwei Plain

汾渭平原是继京津冀和长三角之后环境污染治理的第三大重点区域,为发挥协同作用改善区域大气质量提供更为科学客观的依据,基于2014—2019年汾渭平原11个重点城市的空气质量监测资料和气象数据,利用统计方法分别从空间和时间尺度上揭示了汾渭平原空气质量指数以及主要污染物特征,及其与气象因子的关系.结果表明:11个城市中有7个城市的年均AQI指数100以上,重度以上天数占6%,重污染聚集区主要集中在关中中东部.从时间尺度看,AQI的年际波动明显且在2017年之后略有改善,冬春季特别是1月污染最为严重且呈现出明显的周末效应.首要污染物的季节差异较大,冬季以PM2.5和PM10为主,而夏季则主要以O3为主,春秋季则分别以PM10和PM2.5为主.从气象影响因子看,年尺度上气压、降水、平均气温以及混合层高度除与O3为正相关外与其它污染物均为显著的负相关,且呈现出明显的季节差异.而降水无论年尺度还是季节尺度上均对空气质量有利,特别是中雨量级以上的降水过程对颗粒物和O3污染的改善作用明显.

The Fenwei Plain is the third most important area for environmental pollution control after Beijing,Tianjin,Hebei and the Yangtze River Delta,providing a scientific and objective basis for the synergy of improving regional air quality.Based on the air quality monitoring and meteorological data from 11 cities in the Fenwei Plain,the air quality index(AQI)from 2014—2019 is estimated to reveal the spatiotemporal characteristics of the main air pollutants,as well as their relationships with meteorological factors in the region.The results show that 7 out of 11 cities have an mean annual AQI index of 100 or more,with the severe pollution days accounting for 6%.The heavy pollution areas are mainly concentrated in the central and eastern Guanzhong.From the view of evolution in time,there are obvious interannual fluctuations in AQI and the air quality tends to improve after 2017.The heaviest air pollution occurs in winter and spring,especially in January,and has a significant weekend effect.There is also a clear seasonality in main pollutant variations.In winter,the dominant pollutants are PM2.5 and PM10,O3 in summer,and PM10 and PM2.5 in both spring and autumn.On the effects of meteorological factors,there are significantly negative correlations between pollutants and the mean annual pressure,precipitation,surface air temperature,and mixed layer height,but the positive correlation with O3,and the correlations vary with season.Precipitation is helpful to the improvement of air quality on both seasonal and annual scales,especially the moderate precipitation can significantly improve particulate matter and O3 pollution.