Wang Nan, Lyu Xiaopu, Deng Xuejiao, Huang Xin, Jiang Fei, Ding Aijun
Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, China; Jiangsu Provincial Collaborative Innovation Center for Climate Change, Nanjing, China; Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou, China.
Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong.
Sci Total Environ. 2019 Aug 10;677:732-744. doi: 10.1016/j.scitotenv.2019.04.388. Epub 2019 Apr 28.
During the past five years, China has witnessed a rapid drop of nitrogen oxides (NO) owing to the wildly-applied rigorous emission control strategies across the country. However, ozone (O) pollution was found to steadily deteriorate in most part of eastern China, especially in developed regions such as Jing-Jin-Ji (JJJ), Yangtze River Delta region (YRD) and Pearl River Delta region (PRD). To shed more light on current O pollution and its responses to precursor emissions, we integrate satellite retrievals, ground-based measurements together with regional numerical simulation in this study. It is indicated by multiple sets of observational data that NO in eastern China has declined more than 25% from 2012 to 2016. Based on chemical transport modeling, we find that O formation in eastern China has changed from volatile organic compounds (VOCs) sensitive regime to the mixed sensitive regime due to NO reductions, substantially contributing to the recent increasing trend in urban O. In addition, such transitions tend to bring about an ~1-1.5 h earlier peak of net O formation rate. We further studied the O precursors relationships by conducting tens of sensitivity simulations to explore potential ways for effective O mitigation. It is suggested that the past control measures that only focused on NO may not work or even aggravate O pollution in the city clusters. In practice, O pollution in the three regions is expected to be effectively mitigated only when the reduction ratio of VOCs/NO is greater than 2:1, indicating VOCs-targeted control is a more practical and feasible way.
在过去五年中，由于全国广泛实施严格的排放控制策略，中国的氮氧化物（NO）排放量迅速下降。然而，在中国东部大部分地区，尤其是京津冀（JJJ）、长江三角洲地区（YRD）和珠江三角洲地区（PRD）等发达地区，臭氧（O）污染却在稳步恶化。为了更深入了解当前的臭氧污染及其对前体排放的响应，我们在本研究中整合了卫星反演数据、地面测量数据以及区域数值模拟。多组观测数据表明，从2012年到2016年，中国东部的NO排放量下降了超过25%。基于化学传输模型，我们发现由于NO排放量的减少，中国东部的臭氧形成已从对挥发性有机化合物（VOCs）敏感的状态转变为混合敏感状态，这在很大程度上导致了近期城市臭氧浓度的上升趋势。此外，这种转变往往会使净臭氧形成速率的峰值提前约1 - 1.5小时。我们通过进行数十次敏感性模拟进一步研究了臭氧前体之间的关系，以探索有效减轻臭氧污染的潜在方法。研究表明，过去仅关注NO的控制措施可能无效，甚至会加剧城市群中的臭氧污染。实际上，只有当VOCs/NO的减排比例大于2:1时，这三个地区的臭氧污染才有望得到有效缓解，这表明针对VOCs的控制是一种更实际可行的方法。
