2001—2020年天津市大气污染特征的演变与防治历程

近20年来，随着经济社会的快速发展与污染防治工作的不断深入，我国大气污染特征发生显著变化，特别是京津冀及周边城市空气质量显著改善，大气污染特征与来源构成出现结构性变化，十分有必要对这20年来大气污染的演变历程加以梳理总结. 本文选取北方特大工业城市——天津市为研究对象，基于20年来连续监测数据与相关统计学方法，结合天津市历年大气颗粒物源解析结果，总结了该地区大气污染特征的演变过程. 结果表明:天津市环境空气质量在过去20年出现明显好转，大气污染类型由燃煤扬尘为主的一次混合型逐渐演变为O₃与PM_2.5为代表的二次复合型. 历年源解析结果表明，天津市2020年秋冬季二次硫酸盐贡献率比2011年同期减少了74.1%，燃煤贡献率则下降了31.6%；扬尘和机动车尾气尘贡献率分别从2011年的17.7%和19.9%降至2020年的15.8%和18.2%；而2020年二次硝酸盐贡献率比2011年增长了63.3%. 过去20年天津市重大污染防治措施的有效性分析表明，能源结构调整和“双散”替代使煤炭消耗量减少，PM_2.5浓度下降与煤炭消耗量减少呈显著相关〔偏相关系数(R)=0.879，P<0.05〕；粗颗粒(PM_2.5~10)浓度下降与绿化覆盖率增加呈显著相关〔偏相关系数(R)=?0.859，P<0.05〕；大规模取缔中小燃煤锅炉及脱硫除尘等重大举措的实施，使得SO₂浓度显著下降〔秩相关系数(r_s)=?0.958 6，P<0.05〕. 研究显示，近20年来大气污染防治减排措施的实施使得天津市环境空气质量明显改善，未来要紧密结合国家“双碳”战略，进一步优化产业与能源结构，实现空气质量的持续改善. 

Characteristics Evolution and Prevention Development of Ambient Pollution in Tianjin,China

With rapid socio-economic development and continuous air pollution prevention over the past two decades, the characteristics of air pollution in China has changed significantly. Considerable efforts have been made to improve air quality, led to dramatical changes in atmospheric pollution sources in the Beijing-Tianjin-Hebei Region, thus it is necessary to overview the evolution of air pollution in the past twenty years to get implications for future air quality management. In this study, we analyzed a long-term observation data from Tianjin, a mega-industrial city in northern China, and reanalyzed the previously reported annual source apportionment results during the past twenty years. The results indicate that the air quality in Tianjin improved greatly, and the type of air pollution changed from primary mixing pollution (dominated by coal combustion and resuspended dust) to secondary-rich pollution (represented by ozone and PM_2.5). Multiple years source apportionment data shows that secondary sulfate and coal combustion decreased by 74.1% and 31.6%, respectively, from the autumn and winter of 2011 to the same period of 2020, while dust and vehicle emissions decreased from 17.7% and 19.9% to 15.8% and 18.2%, respectively. As oppose to these sources, nitrate increased by 63.3%. The effectiveness of major pollution prevention and control measures enacted in Tianjin over the past two decades was qualitatively reviewed. The adjustment of energy structure together with the displacement of coal for residential combustion and ‘Dispersed, Disrupted and Polluted’ enterprises reduced coal consumption, which is significantly correlated with the decline in PM_2.5 concentrations (coefficient of partial correlation R=0.879, P<0.05). Major measures such as wide range ban on small and medium-sized coal-fired boilers and flue gas desulfurization have been implemented, and the SO₂ concentration has been obviously reduced (coefficient of rank correlation r_s= ?0.9586, P<0.05). Meanwhile, the decrease in the concentration of coarse particles (PM_2.5-10) is obviously related to the increase in greenery coverage (coefficient of partial correlation R= ?0.859, P<0.05). The study indicates that the air quality improved significantly due to the implement of atmospheric pollution prevention measures in the past two decades. It is necessary for policy makers to integrated with the ‘carbon peaking and neutrality’ strategy closely, and further optimize the industrial and energy structure in order to achieve continuous improvement of air quality.