Averting air pollution violations in Chinese cities hinges upon short-term reductions in air pollutant emissions as a critical emergency response. However, the repercussions of short-term emission reductions on the air quality conditions of southern Chinese urban centers in spring remain underexplored. An analysis of air quality fluctuations in Shenzhen, Guangdong, was performed encompassing the time frame before, during, and after the city-wide COVID-19 lockdown in place from March 14th to 20th, 2022. The lockdown period was preceded and accompanied by stable weather, thereby making local air pollution highly susceptible to the influence of local emissions. During the lockdown, a decrease in traffic emissions across the Pearl River Delta (PRD) was observed, evidenced by both in-situ measurements and WRF-GC simulations. This led to corresponding decreases in nitrogen dioxide (NO2), respirable particulate matter (PM10), and fine particulate matter (PM2.5) concentrations in Shenzhen, by -2695%, -2864%, and -2082%, respectively. In contrast, surface ozone (O3) concentrations did not show considerable shifts [-1065%]. TROPOMI satellite measurements of formaldehyde and nitrogen dioxide column concentrations displayed that ozone photochemistry in the Pearl River Delta (PRD) during spring 2022 was largely controlled by volatile organic compound (VOC) concentrations, and there was a lack of responsiveness to decreased nitrogen oxide (NOx) concentrations. The mitigation of NOx might have unexpectedly elevated ozone levels, due to the compromised titration process of ozone by nitrogen oxides. Air quality improvements from the limited urban lockdown, constrained in both space and time regarding emission reductions, were less impactful than the extensive air quality improvements observed across China during the 2020 COVID-19 lockdown. The implications of NOx emission reductions on ozone formation must be incorporated into future air quality management plans for South China cities, and special consideration should be given to strategies for reducing both NOx and VOCs simultaneously.

In China, particulate matter with aerodynamic diameters less than 25 micrometers (PM2.5) and ozone are the two principal air pollutants, posing a significant threat to human health. In Chengdu, between 2014 and 2016, the influence of PM2.5 and ozone on mortality was analyzed using generalized additive modeling and non-linear distributed lag modeling, which estimated the effect sizes of daily maximum 8-hour ozone concentration (O3-8h) and PM2.5. From 2016 to 2020, Chengdu's health impacts were assessed using both the environmental risk model and the environmental value assessment model, assuming reductions in PM2.5 and O3-8h concentrations to specific air pollution control limits (35 gm⁻³ and 70 gm⁻³, respectively). In Chengdu, the annual PM2.5 concentration displayed a progressive downward trend from 2016 to 2020, as shown in the results. In 2016, the PM25 concentration stood at 63 gm-3; however, by 2020, it had risen to a significantly higher level of 4092 gm-3. Selleck Carboplatin On average, values declined at a rate of nearly 98% each year. Notwithstanding past trends, the O3-8h annual concentration witnessed an increase from 155 gm⁻³ in 2016 to 169 gm⁻³ in 2020, at an approximate rate of 24%. Regulatory toxicology The maximum lag effect produced corresponding exposure-response coefficients for PM2.5 of 0.00003600, 0.00005001, and 0.00009237 for all-cause, cardiovascular, and respiratory premature deaths, respectively. The respective coefficients for O3-8h were 0.00003103, 0.00006726, and 0.00007002. A decrease in PM2.5 levels to the national secondary standard limit (35 gm-3) would, unfortunately, coincide with a yearly decrease in health beneficiaries and a reduction in associated economic advantages. A notable reduction in the number of health beneficiaries impacted by deaths from all-cause, cardiovascular, and respiratory diseases is apparent. The count was 1128, 416, and 328 in 2016, diminishing to 229, 96, and 54 in 2020, respectively. A total of 3314 premature deaths, preventable in nature, occurred across five years, yielding a significant health economic gain of 766 billion yuan. Reducing (O3-8h) concentrations to the World Health Organization's standard of 70 gm-3 would predictably translate into a yearly rise in the number of health beneficiaries and corresponding economic benefits. By 2020, the number of deaths among health beneficiaries from all causes, cardiovascular disease, and respiratory illnesses had substantially increased, going from 1919, 779, and 606 in 2016 to 2429, 1157, and 635, respectively. Annual average avoidable all-cause mortality grew by 685%, and cardiovascular mortality rose by 1072%, these figures being higher than the annual average rise rate of (O3-8h). Avoidable deaths from all causes of disease totaled 10,790 across five years, creating a health economic benefit valued at 2,662 billion yuan. The Chengdu PM2.5 pollution levels, according to these findings, were effectively managed, while ozone pollution escalated significantly, emerging as a new and serious threat to public health. Consequently, PM2.5 and ozone control should be managed synchronously in the future.

Recent years have brought a marked increase in the severity of O3 pollution in Rizhao, a city characteristically situated on the coast, a typical condition for such locations. To ascertain the origins and causes of O3 pollution in Rizhao, the CMAQ model's IPR process analysis and ISAM source tracking tools were respectively employed to quantify the contributions of various physicochemical processes and specific source areas to O3 levels. Moreover, a comparison of days with ozone concentrations above the threshold and those below, along with the HYSPLIT model, enabled an investigation of the ozone transportation patterns in the Rizhao area. On days when ozone concentrations exceeded the permissible limits in the coastal areas of Rizhao and Lianyungang, the concentrations of O3, NOx, and VOCs showed a notable increase compared to days when ozone remained within the permissible range, as indicated by the results. The primary driver of pollutant transport and accumulation was Rizhao serving as a convergence zone for the western, southwestern, and eastern winds on days of exceedance. Transport process (TRAN) analysis revealed a substantial rise in near-surface ozone (O3) contribution near Rizhao and Lianyungang coastal areas during exceedance days. Conversely, the contribution to areas west of Linyi exhibited a decline. During Rizhao's daytime hours and across all altitudes, the photochemical reaction (CHEM) positively influenced ozone concentration levels. Conversely, the TRAN effect was positive below 60 meters and mainly negative above. A notable increase in the contributions of CHEM and TRAN was observed at heights of 0 to 60 meters above the ground on days when thresholds were exceeded, escalating approximately twofold compared to non-exceedance days. Local Rizhao sources were identified as the main contributors to NOx and VOC emissions, demonstrating contribution rates of 475% and 580%, respectively, according to the source analysis. An external source, significantly impacting O3 levels (675%), was outside the simulation area. There will be a pronounced escalation in the ozone (O3) and precursor contributions from Rizhao, Weifang, and Linyi in the west, along with cities in the south like Lianyungang, whenever air quality standards are breached. The transportation route analysis demonstrated that the western Rizhao path, the significant O3 and precursor transport route in Rizhao, had the largest proportion of exceedances, comprising 118% of the total. Microscopes and Cell Imaging Systems The findings of process analysis and source tracking demonstrated this, with 130% of the trajectories having originated and traversed Shaanxi, Shanxi, Hebei, and Shandong.

Data from 181 tropical cyclones in the western North Pacific, spanning 2015 to 2020, along with hourly ozone (O3) concentration data and meteorological observations from 18 Hainan Island cities and counties, were utilized in this study to assess the impact of tropical cyclones on ozone pollution in Hainan. A considerable 40 tropical cyclones (221% of total) observed O3 pollution on Hainan Island throughout their lifetimes over the past six years. The incidence of tropical cyclones in Hainan Island and the number of days with ozone pollution are positively related. 2019 saw the highest number of severely polluted days, which were identified as those with three or more cities and counties violating air quality standards. These numbered 39, signifying a 549% increase compared to previous years. Tropical cyclone occurrences linked to high pollution (HP) showed an upward trend, represented by a trend coefficient of 0.725 (exceeding the 95% confidence level) and a climatic trend rate of 0.667 per unit of time. The intensity of tropical cyclones demonstrated a positive correlation with the maximum 8-hour moving average of ozone (O3-8h) levels observed on Hainan Island. A significant portion of the typhoon (TY) intensity level samples, 354%, were HP-type tropical cyclones. Tropical cyclone paths' cluster analysis revealed South China Sea cyclones (type A), accounting for 37% (67 cyclones), as the most frequent and the most likely to induce significant O3 pollution events of high concentration across Hainan Island. For type A tropical cyclones over Hainan Island, the average occurrence rate was 7, and the average O3-8h measurement was 12190 gm-3. During the high-pressure period, tropical cyclone centers were generally clustered in the middle of the South China Sea and the western Pacific Ocean, near the Bashi Strait. Hainan Island's atmospheric conditions, altered by HP tropical cyclones, encouraged a surge in ozone concentration.

From 2015 to 2020, the Pearl River Delta (PRD) ozone observation and meteorological reanalysis data were subjected to the Lamb-Jenkinson weather typing method (LWTs) to study the characteristics of various circulation types and assess their role in influencing the yearly shifts in ozone levels. The results presented a count of 18 unique weather types found within the PRD. A correlation between Type ASW and ozone pollution was observed, with Type NE exhibiting a more significant link to more substantial ozone pollution impacts.