大气网格化治理是否改善了西安市空气质量？

Has Grid Management Improved the Air Quality of Xi’an City?

摘要: 自西安市大气网格化治理于2014年深入实践以来，西安市空气质量得到显著改善，但冬季依然存在极端天气现象，雾霾污染依旧非常严峻。直观上难以判断大气网格化治理机制对于空气质量改善是否有效，其治理效果甚至受到外界质疑。为分析该问题，运用2013至2017年的日度时间序列数据与工具变量回归进行实证分析。结果表明：无论从整体空气质量角度还是从污染物异质性(SO2、O3)角度分析，该环境规制政策效果十分显著。研究进一步发现，西安市不同时期空气污染物存在结构性差异，夏季以SO2污染为主，网格化治理通过遏制SO2排放而显著改善空气质量；冬季则以NOx污染为主，网格化对此治理效果并不显著，无法进一步改善空气质量。综合考虑，网格化治理能够发挥预期治理成效，只是进入冬季后，能源消费季节性变化导致污染物结构性变化，进而弱化网格化冬季治霾效果，但西安市大气网格化治理依然能够为汾渭平原雾霾协同治理提供决策依据，奠定实践基础。

Abstract: Since the implementation of grid management in Xi’an City, the air quality has been improved ob-viously, but there were still some extreme weather issues that were not addressed totally. Thus, we cannot directly draw the conclusion of whether grid management can improve air quality; even it can be easily criticized by society. This paper uses time series data from 2013 to 2017 and in-strument variables to take empirical research. The results manifest that whatever in the perspec-tive of AQI or different air pollutants (SO2, O3), the effect of this environmental regulation policy is very remarkable. Research further found that air pollutants of Xi’an have structural differences in different seasons. In summer, pollutants are SO2 mainly, and grid management can improve AQI obviously by controlling emission of SO2; but during winter, pollutants are NOx mainly, so grid management can not improve AQI. To sum up, the mechanism of grid management is effective; merely, structural change of energy consumption leads to that of pollutants in winter, so it weakens the governance effect of grid management. But grid management of Xi’an can provide the basis of collaborative governance about haze pollution for these areas.