An insight into the formation of severe ozone episodes: modeling the 21/03/01 event in the ESCOMPTE region

High ozone concentrations are observed more and more frequently in the lower troposphere. The development of such polluted episodes is linked to a complex set of chemical, physical and dynamical parameters that interact with each other. To improve air quality, it is necessary to understand and quantify the role of all these processes on the intensity of ozone formation. The ESCOMPTE program, especially dedicated to the numerical simulation of photochemical episodes, offers an ideal frame to investigate details of the roles of many of these processes through 3D modeling. This paper presents the analysis, with a 3D eulerian model, of a severe and local episode of ozone pollution that occurred on the 21st of March 2001 in the ESCOMPTE region. This episode is particularly interesting due to the intensity of the observed ozone peaks (450 μg/m³ during 15 mn) but also because it did not occur in summer but at the beginning of spring. As part of the premodeling work of the ESCOMPTE program, this study focuses on the sensitivity of the simulated ozone peaks to various chemical and physical phenomena (long-range transport, industrial emissions, local dynamic phenomena…) to determine their influence on the rise of high local photooxidant concentrations and to better picture the photochemistry of the ESCOMPTE region. Through sensitivity tests to dynamical calculation resolution and emissions, this paper shows how the combination of sea and pond breezes with emissions of reactive VOCs can generate local intense ozone peaks.     

Changes in air pollutants during the COVID-19 lockdown in Beijing:Insights from a machine-learning technique and implications for future control policy

基于2015-2020年北京35个环境空气站和20个气象站观测资料,应用机器学习方法(随机森林算法)分离了气象条件和源排放对大气污染物浓度的影响.结果发现,为应对疫情采取的隔离措施使北京2020年春节期间大气污染物浓度降低了35.1％-51.8％;其中,背景站氮氧化物和一氧化碳浓度的降幅最大,超过了以往报道较多的交通站...     

Effects of pollution control measures on carbon emission reduction in China: evidence from the 11th and 12th Five-Year Plans

SO₂ emissions have been declining in China recently. The emission reduction has mainly been achieved engineering reduction, structural reduction, and administrative reduction. In this paper, three key industries (electricity generation, steel, and cement) are selected to measure the effects of SO₂ emission reductions, the synergy effects of energy saving, and CO₂ emission reduction. The main results show that, during the period of the ‘11th Five-Year Plan’, engineering reduction of coal-fired power plant desulfurization played the most crucial role in the emission reduction; both engineering reduction and structural reduction can achieve low-pollution emission, but the contributions are not the same due to the divergence of relevant industries. Generally speaking, structural reduction can relatively easily achieve the synergy effect of the main pollutants and GHGs; in comparison, however, engineering reduction does not easily achieve the synergy effect. During the ‘13th Five-Year Plan’ period, the following plans are proposed: strengthening the front pollution control, increasing the engineering reduction, narrowing the difference between the pollution reduction engineering ability and the actual pollution reduction effect, and strengthening the supervisory and administrative effect of both the approval of the front end and the running of the middle end.

POLICY RELEVANCE

China is on the way to realize industrialization and urbanization. The climate-friendly environmental protection strategy is particularly important for rapidly developing countries such as China, because it can address air pollution and climate change issues at the same time in a more economically efficient manner. This paper selects three key industries to evaluate current pollutant control policy synergy effect from the ‘11th Five-Year Plan’ to the ‘12th Five-Year Plan’ period in order to give more sense to policy makers during 13th Five-Year Plan. The estimate of this study shows that the control of pollutants can generally have synergic control effects on GHG emissions and give detailed measures for 13th Five-Year Plan.