Ren Jie, Hao Yufang, Zheng Xudong, Li Xin, Xie Shaodong
College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, Beijing 100871, China.
College of Environmental Sciences and Engineering, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Peking University, Beijing 100871, China; Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen, -PSI, Switzerland.
Sci Total Environ. 2024 Nov 25;953:176037. doi: 10.1016/j.scitotenv.2024.176037. Epub 2024 Sep 3.
Ozone (O) pollution has become a noticeable problem in the Chengdu-Chongqing Economic Circle in China. The April-September MDA8 O level increases significantly by 2.26 μg m year from 2015 to 2023, with meteorological factors occupying merely 18 % in line with multivariate linear regression. To reveal the impact of anthropogenic emissions on O increase, O production sensitivity is accurately diagnosed by deriving localized thresholds for satellite formaldehyde (HCHO) to NO ratio and validated by in-situ measurements and observation-based model. Tracking volatile organic compounds (VOCs) and NOx through satellite HCHO and NO, the O responses to precursor changes are assessed for long-term and special cases, and appropriate precursor reduction ratios are inferred. The results present that the transition range of satellite HCHO/NO from VOC-limited to NOx-limited in the region ranges from 2.7 to 4.3. The VOC-limited regime is concentrated in the urban areas of Chongqing and Chengdu as well as the central of the neighboring cities such as Deyang, Mianyang, and Meishan. The relative incremental reactivity from in-situ observations and box model at three sites in August 2019 demonstrates that O is most sensitive to anthropogenic VOC at urban and suburban sites, consistent with satellite results. Satellite and surface NO decrease at an annual rate of -2.1 % and - 2.9 % between 2015 and 2023, with larger decreases in Chengdu and Chongqing. In contrast, the trend of satellite HCHO is insignificant, indicating effective reduction in NOx but no significant reduction in VOC. This inappropriate reduction results in an increase in urban O. The three short-term cases further validate the need for synergistic NOx and VOC reductions. Based on the relationship between O and satellite NO and HCHO, the minimum and optimal reduction ratios of VOC to NOx are 0.4:1 and 2.4:1 for the entire region, with higher ratios in Chengdu and Chongqing.
在中国成渝经济圈，臭氧（O₃）污染已成为一个显著问题。从2015年到2023年，4月至9月的日均最大8小时滑动平均臭氧水平每年显著上升2.26 μg m⁻³，根据多元线性回归分析，气象因素仅占18%。为揭示人为排放对臭氧增加的影响，通过推导卫星甲醛（HCHO）与一氧化氮（NO）比值的局部阈值，准确诊断了臭氧生成敏感性，并通过实地测量和基于观测的模型进行了验证。通过卫星HCHO和NO追踪挥发性有机化合物（VOCs）和氮氧化物（NOₓ），评估了长期和特殊情况下臭氧对前体变化的响应，并推断出合适的前体减排比例。结果表明，该地区卫星HCHO/NO从VOC限制向NOₓ限制的转变范围为2.7至4.3。VOC限制区域集中在重庆和成都的市区以及德阳、绵阳和眉山等邻近城市的中部。2019年8月三个站点的实地观测和箱式模型得出的相对增量反应活性表明，在城市和郊区站点，臭氧对人为排放的VOC最为敏感，这与卫星观测结果一致。2015年至2023年期间，卫星和地面NO分别以-2.1%和-2.9%的年速率下降，成都和重庆的下降幅度更大。相比之下，卫星HCHO的趋势不显著，表明NOₓ得到有效减排，但VOC没有显著减少。这种不适当的减排导致城市臭氧增加。这三个短期案例进一步验证了协同减排NOₓ和VOC的必要性。基于臭氧与卫星NO和HCHO的关系，整个区域VOC与NOₓ的最小和最佳减排比例分别为0.4:1和2.4:1，成都和重庆的比例更高。
