长江经济带空气质量的时空分布特征及影响因素

基于2015~2018年空气质量实时监测数据,研究了长江经济带AQI的时空变化特征,从大气污染物排放量和气象因素两方面选取评价指标,利用地理探测器揭示了长江经济带AQI分布的影响因素及其季节变化.结果表明：2015~2018年长江经济带空气质量总体趋于改善,平均超标率由19.8%降至16.2%,除O₃超标率上升外,其余常规监测指标均有不同程度的下降.2017年开始O₃的超标率超过PM₁₀,成为长江经济带仅次于PM_2.5的大气污染物.AQI月变化曲线大体呈U型,具有冬春高、夏秋低的特点.长江经济带空气质量改善主要体现在冬、秋两季,O₃浓度的上升使夏季空气超标率上升,春季变化不大.AQI和空气超标率总体呈东高西低、北高南低的分布特征,其中上海、江苏、安徽中北部和浙江北部污染最严重,湖北中部和成渝地区其次,云南、贵州和四川西部空气质量良好.春夏季AQI的差异主要表现为东西向,秋冬季则主要表现为南北向.污染物排放量因子对长江经济带AQI分布有显著的正向影响,气象因子的影响方向则随季节变化而变化.全年和春、秋、冬3季AQI的分布格局主要由大气污染物排放量决定,夏季气象因子的影响力则更大.

Spatial-temporal distribution of air quality and its influencing factors in the Yangtze River economic belt

In this paper, spatial-temporal features of the air quality index (AQI) in Yangtze River economic belt were studied by the real-time monitoring data on air quality from 2015 to 2018, and emissions of air pollutants and meteorological factors were taken as two evaluating indicators to reveal the factors and their seasonal variation to the distribution of AQI in the target regions by geographical detector. The air quality of Yangtze River economic belt was improving from 2015 to 2018 with an average ratio of days beyond standard decreased to 16.2% from 19.8%, and the rest of monitoring indicators were decreasing more or less except a rising ratio of days beyond standard for O₃. In terms of the ratio of days beyond standard, PM₁₀ was overtook by O₃ and became the second most significant pollutant following PM_2.5 for Yangtze River economic belt since 2017. The monthly variation curve for AQI showed a "U" model, which was higher in winter and spring and lower in summer and autumn. The improving mentioned was particularly witnessed in winter and autumn. And the rising concentration of O₃ then led to a rising ratio of days beyond standard in summer, but a minus variation was seen in spring. AQI and ratio of days beyond standard presented a pattern of being higher in the east and north, and lower in the west and south. And the most polluted area covered Shanghai, Jiangsu, central and northern Anhui, and northern Zhejiang, then followed by central Hubei and Chengdu-Chongqing area, and the air quality was good in Yunnan, Guizhou, and western Sichuan. The variation of AQI in spring and summer was mainly presented when studied on east-west direction while it turned to south-north direction in autumn and winter. Factors to emissions of pollutants had a positive influence on the distribution of AQI in target areas, while there was a seasonal variation when it came to the direction of the influence by meteorological factors. The distribution of AQI in the whole year, spring, autumn and winter was mainly determined by the emission factors of air pollutants, while a more powerful influence was seen by meteorological factors in summer. Factors to emissions of pollutants had a positive influence on the distribution of AQI in target areas, while there was a seasonal variation when it came to the direction of the influence by meteorological factors. Whether for the whole year, spring, autumn or winter, the distribution of AQI was decided by the volume of air pollution pollutant, and a more powerful influence was seen by meteorological factors in summer.