Zong Zheng, Tan Yang, Wang Xiao, Tian Chongguo, Li Jun, Fang Yunting, Chen Yingjun, Cui Song, Zhang Gan
State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, China.
Key Laboratory of Coastal Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, China.
Environ Int. 2020 Apr;137:105592. doi: 10.1016/j.envint.2020.105592. Epub 2020 Feb 27.
In China, nitrate (NO) becomes the main contributor to fine particles (PM) because the emissions of its precursor, nitrogen oxides (NO), were not recognized and controlled well in recent years. In this work, sources, conversion, and geographical origin of NO were interpreted combining the isotopic information (δN and δO) of NO and dual modelling at five Chinese megacities (Beijing, Shanghai, Guangzhou, Wuhan and Chengdu) during 2013-2014. Results showed that the δN-NO values (n = 512) ranged from -12.3‰ to +22.9‰, and the average δO-NO value was +83.4‰ ± 17.2‰. The isotopic compositions both had a rising tendency as ambient temperature dropped, attributing largely to the source changes. Bayesian model indicated the percentage for the OH pathway of NO conversion had a clear seasonal variation with a higher value during summer (58.0% ± 9.82%) and a lower value during winter (11.1% ± 3.99%); it was also significantly correlated with latitude (p < 0.01). Coal combustion was the most important source of NO (31.1%-41.0%), which was geographically derived from North China and other south-central developed regions implied by Potential Source Contribution Function (PSCF). Apart from Chengdu, mobile sources was the second largest contributor to NO. This source was extensive but uniformly distributed all around the typical urban agglomerations of China. Biomass burning and microbial processes shared similar source areas, mostly originating from the North China Plain and Sichuan Basin. Based on the NO features, we infer that residential coal combustion was the primary source of heavy PM pollution in Chinese megacities. Controlling the source categories of these regional priorities would help mitigate atmospheric pollution in these areas.
在中国，硝酸盐（NO）成为细颗粒物（PM）的主要贡献者，因为其前体氮氧化物（NO）的排放近年来未得到很好的认识和控制。在这项工作中，结合2013 - 2014年期间中国五个特大城市（北京、上海、广州、武汉和成都）的NO同位素信息（δN和δO）以及双重模型，解释了NO的来源、转化和地理起源。结果表明，δN-NO值（n = 512）范围为-12.3‰至+22.9‰，平均δO-NO值为+83.4‰±17.2‰。随着环境温度下降，两种同位素组成均呈上升趋势，这在很大程度上归因于源的变化。贝叶斯模型表明，NO转化的OH途径百分比具有明显的季节变化，夏季较高（58.0%±9.82%），冬季较低（11.1%±3.99%）；它也与纬度显著相关（p < 0.01）。煤炭燃烧是NO的最重要来源（31.1% - 41.0%），潜在源贡献函数（PSCF）表明其地理来源是中国北方和其他中南部发达地区。除成都外，移动源是NO的第二大贡献者。该来源广泛但均匀分布在中国典型的城市群周围。生物质燃烧和微生物过程具有相似的源区，大多起源于华北平原和四川盆地。基于NO的特征，我们推断居民煤炭燃烧是中国特大城市重PM污染的主要来源。控制这些区域重点源类别将有助于减轻这些地区的大气污染。
