Search

In recent years, nocturnal ozone enhancement (NOE) events have emerged as a prominent research focus in the field of the atmospheric environment. By using statistical analysis methods, we conducted a comparative investigation of nocturnal ozone concentrations and NOE events in Dongying, the central city of the Yellow River Delta, China, in 2022 and 2023, and further explored the effects of NOE events on O3 and PM2.5 on the same night and the subsequent day. The results showed that from 2022 to 2023, in Dongying, the annual average nocturnal ozone concentrations increased from 51 μg/m3 to 59 μg/m3, and the frequency of NOE events was higher in the spring, summer, and autumn, and lower in the winter. The NOE events not only exhibited promoting effects on nocturnal O3 and Ox, and on the daily maximum 8 h average concentration of O3 (MDA8-O3) on the same day (comparatively noticeable in summer and autumn), but also demonstrated a clear impact on nocturnal PM2.5 and PM2.5-bounded NO3− and SO42− (especially in winter). Additionally, the NOE events also led to higher concentrations of O3 and Ox, as well as higher MDA8-O3 levels during the subsequent day, with more observable impacts in the summer. The results could strengthen our understanding about NOE events and provide a scientific basis for the collaborative control of PM2.5 and O3 in urban areas in the Yellow River Delta in China. [ABSTRACT FROM AUTHOR]

In order to investigate the causes of complex air pollution in coastal cities in the Bohai Rim of China, a one-month intensive field observation combined with model simulation was carried out in a typical city named Dongying in September 2022. The results showed that two PM2.5 and O3 complex pollution episodes occurred in Dongying in the observation period, with the primary pollutant being O3. Atmospheric photochemical reactions occurring under unfavorable meteorological conditions led to the production of O3 while at the same time facilitating the generation of nitrate, sulfate, and other secondary components of PM2.5 by enhancing the atmospheric oxidizing capacity, which promoted the formation of complex air pollution. It was worth noting that in the context of high pollutants emission, the occurrence of complex air pollution was more sensitive to the variation in meteorological conditions than to the change in pollutants emission. To continuously improve air quality and protect human health in Dongying, it is recommended that an effective regional joint air pollution prevention and control mechanism with neighboring cities should be established in the premise of effective local pollutants reduction, and special attention should be paid to the adverse effect of the air mass transportation from Bohai Bay. [ABSTRACT FROM AUTHOR]

Vehicle exhaust, as a major source of air pollutants in urban areas, contains a complex mixture of organic vapours including long-chain alkanes and aromatic hydrocarbons. The atmospheric oxidation of vehicle emissions is a highly complex system as inorganic gases (e.g. NOx and SO2) from other urban sources coexist and therefore remains poorly understood. In this work, the photooxidation of n -dodecane, 1,3,5-trimethylbenzene, and their mixture is studied in the presence of NOx and SO2 to mimic the atmospheric oxidation of urban vehicle emissions (including diesel and gasoline vehicles), and the formation of ozone and secondary aerosols is investigated. It is found that ozone formation is enhanced by higher OH concentration and higher temperature, but is influenced little by SO2 concentration. However, SO2 can largely enhance the particle formation in both number and mass concentrations, likely due to the promoted new particle formation and acid-catalysed heterogeneous reactions from the formation of sulfuric acid. In addition, organo-sulfates and organo-nitrates are detected in the formed particles, and the presence of SO2 can promote the formation of organo-sulfates. These results provide a scientific basis for systematically evaluating the effects of SO2 , OH concentration, and temperature on the oxidation of mixed organic gases in the atmosphere that produce ozone and secondary particles. [ABSTRACT FROM AUTHOR]

• Research progress of observation-based ozone formation sensitivity is reviewed. • Threshold values for Photochemical Indicator methods need to be localized. • Reaction mechanisms and monitoring capability need to be improved for OBM. • Ozone formation sensitivity in China presents the gradual shifting tendency. • Dynamic regulation capability for ozone pollution control needs to be built. Observation-based method for O 3 formation sensitivity research is an important tool to analyze the causes of ground-level O 3 pollution, which has broad application potentials in determining the O 3 pollution formation mechanism and developing prevention and control strategies. This paper outlined the development history of research on O 3 formation sensitivity based on observational methods, described the principle and applicability of the methodology, summarized the relative application results in China and provided recommendations on the prevention and control of O 3 pollution in China based on relevant study results, and finally pointed out the shortcomings and future development prospects in this field in China. The overview study showed that the O 3 formation sensitivity in some urban areas in China in recent years presented a gradual shifting tendency from the VOC-limited regime to the transition regime or the NO x -limited regime due to the implementation of the O 3 precursors emission reduction policies; O 3 pollution control strategies and precursor control countermeasures should be formulated based on local conditions and the dynamic control capability of O 3 pollution control measures should be improved. There are still some current deficiencies in the study field in China. Therefore, it is recommended that a stereoscopic monitoring network for atmospheric photochemical components should be further constructed and improved; the atmospheric chemical mechanisms should be vigorously developed, and standardized methods for determining the O 3 formation sensitivity should be established in China in the near future. [Display omitted] [ABSTRACT FROM AUTHOR]

PM2.5 level has decreased significantly in Beijing in recent years due to the strict air quality control measures taken in Jingjinji Region and the surrounding areas. However, the variation characteristics of the concentrations of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in Beijing in recent years are still not so clear. In order to understand the pollution status of PM2.5-bound PAHs in Beijing, fifteen PAHs were measured in a typical urban area of Beijing from 1 March to 20 March 2018. The average mass concentration of the 15 PAHs was 21 ng/m3 and higher in the nighttime than that in the daytime. The proportion of 4-ring PAHs in 15 PAHs was highest (43%), while 6-ring PAHs was lowest (10%). The levels of PAHs were higher during heavy pollution episodes than those in non-heavy pollution episodes, and the proportions of 5- and 6-ring PAHs were increased during a heavy pollution episode. PAHs posed obvious carcinogenic risks to the exposed populations, and the risk was higher during heavy pollution episodes than the average value of the whole monitoring period. The main sources of PAHs were traffic emissions and coal/biomass burning. Air masses from the south-southeast had a great influence on the PM2.5 levels during a heavy pollution episode. It is recommended that not only the PM2.5 levels but also the PAHs levels bounded in PM2.5 should be controlled to protect human health in Beijing. [ABSTRACT FROM AUTHOR]

Twenty-three atmospheric volatile halogenated hydrocarbons (VHHs) were detected in a typical urban area of Beijing, China from 24 August to 4 September, 2012. The mean and range in daily mass concentrations of the 23 VHHs were 30.53 and 13.45–76.33 µg/m3, respectively. Seven of those VHHs were controlled ozone-depleting substances in China, with a mean of 12.95 µg/m3, accounting for 42.43% of the total. Compared with other national and international cities, the concentrations of the selected 11 VHHs in this study were relatively higher. Dichloroethane had the highest mass concentration, followed by difluorochloromethane. Maxima of total VHHs occurred within the period 8:30–9:00 a.m., while minima occurred during 1:30–2:00 p.m. Source apportionment suggested that the main sources of VHHs in the study area were solvents usage and industrial processes, leakage of chlorofluorocarbons banks, refrigerants, and fumigant usage. Among the selected 7 VHHs, trichloromethane, tetrachloromethane, 1,2-dichloroethane, and 1,4-dichlorobenzene posed potential carcinogenic risks to exposed populations, while none of the selected 11 VHHs posed appreciable non-carcinogenic risks to exposed populations. The carcinogenic risks from atmospheric VHHs in Beijing are higher than in other Chinese cities, indicating that it is necessary to implement immediate control measures for atmospheric VHHs in Beijing. [ABSTRACT FROM AUTHOR]