“城市双修”试点对PM2.5和臭氧协同控制的效果评估:以三亚市为例

我国大气环境进入PM_2.5污染依然严峻和臭氧(O₃)污染日益突出的新阶段，“十四五”规划纲要提出要推进PM_2.5和臭氧(O₃)污染协同控制. 在大气污染防治领域，减排长期以来被视作污染防治的唯一出路. 本文借鉴应对气候变化问题所采用的减排与适应的两种治理模式，探索适应模式的污染防治效果. 选取我国首个“生态修复、城市修补”(简称“城市双修”)试点城市——三亚市作为研究对象，以城市月均空气质量作为评价指标，采用准试验法评估试点效果. 以海口市作为三亚市的空间对照，以试点前1.5年作为试点后1.5年的时间对照，采用依次添加气象、固定效应、1阶、2阶时间趋势控制的双倍差异模型，识别“城市双修”试点对三亚市空气污染的防治效果. 结果表明:①“城市双修”试点大幅降低了三亚市的PM和O₃污染，其中，O₃浓度降低约30 μg/m3，PM_2.5、PM₁₀浓度分别降低约7、10 μg/m3，三者降幅分别达47%、39%、28%；②“城市双修”对O₃浓度的影响是持续的，对PM浓度的影响滞后半年；③将“城市双修”试点分别提前6、9、12个月的安慰剂试点均未发现对三亚市空气质量有任何显著影响. 研究显示，“城市双修”试点对三亚市PM_2.5和O₃协同控制具有意外显著的效果；甄别“城市双修”在不同时段所采取的修复细节有助于实现PM_2.5和O₃的精准治理，推广这些修复措施至其他城市有利于缓解我国当前面临的大气环境问题. 

Effect of Urban Double Restoration Pilot Project for Coordinated Control of PM2.5 and O3 Pollution: A Case Study of Sanya,China

China's air environment has entered a new phase of severe PM_2.5 pollution and increasingly worsened O₃ pollution. Thus, the outline of the ‘14th Five-Year Plan’ proposed to promote the coordinated control of PM_2.5 and O₃ pollution. In contrast to the dual governance model of mitigation and adaptation being used in reaction to climate change, China has long regarded emission reduction as the only way to prevent pollution. Exploring the effect of adaptation besides abatement may be an economic approach for current pollution control. In June 2015, China's first Ecological Restoration and Urban Repair (also known as Urban Double Restoration (UDR)) pilot was launched in the city of Sanya, Hainan Province, which provides a natural experiment to examine the effect of adaptation on pollution. Using monthly urban air quality data from 2014-2016 as the measure, and based on geography, climate, and economic dimensions to screen Haikou from other cities in Hainan as a control city for Sanya, a difference-in-differences (DD) method has been built after performing the parallel trend test. Using the pre-pilot period as a temporal control for the post-pilot period, the DD specifications gradually controlling for atmospheric factors, fixed effects, a linear time trend, and a quadratic time trend identify the causal impact of the UDR pilot on air quality in Sanya. The results show that: (1) The UDR pilot significantly reduced Sanya's PM and O₃ pollution. The O₃ concentration was reduced by 30 μg/m3, PM_2.5 concentration was reduced by 7 μg/m3, and PM₁₀ concentration was reduced by 10 μg/m3, which was equivalent to a 47%, 39% and 28% reduction. (2) The UDR's effect on the reduction of O₃ concentration was persistent, and the effect on the reductions of PM was postponed for half a year. (3) The placebos that moved the URD pilot 6 months, 9 months, and 12 months ahead of schedule were found to not affect Sanya's air quality. This research suggests that the UDR pilot has an unexpected significant effect on the coordinated control of PM_2.5 and O₃ pollution in Sanya. Identifying the details of the restoration in different UDR phrases will help to accurately control PM_2.5 and O₃, and the promotion of these restoration details to other cities may facilitate mitigating the new air environment problems currently facing China.