Impact of the Urban Heat Island Effect on Ozone Pollution in Chengdu City,China

With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.

Cost-Effective Control of Ground-Level Ozone Pollution in and around Beijing

Ground level ozone pollution has become a significant air pollution problem in Beijing. Because of the complex way in which ozone is formed, it is difficult for policy makers to identify optimal control options on a cost-effective basis. This paper identi-fies and assesses a range of options for addressing this problem. We apply the Ambient Least Cost Model and compare the eco-nomic costs of control options, then recommend the most effective sequence to realize pollution control at the lowest cost. The study finds that installing of Stage II gasoline vapor recovery system at Beijing's 1446 gasoline stations would be the most cost-effective option. Overall, options to reduce ozone pollution by cutting ve-hicular emissions are much more cost-effective than options to "clean up" coal-fired power plants.

Impacts of synoptic circulation on surface ozone pollution in a coastal eco-city in Southeastern China during 2014-2019

The coastal eco-city of Fuzhou in Southeastern China has experienced severe ozone(O_(3))episodes at times in recent years.In this study,three typical synoptic circulations types(CTs)that influenced more than 80%of O_(3) polluted days in Fuzhou during 2014-2019 were identified using a subjective approach.The characteristics of meteorological conditions linked to photochemical formation and transport of O_(3) under the three CTs were summarized.Comprehensive Air Quality Model with extensions was applied to simulate O_(3) episodes and to quantify O_(3) sources from different regions in Fuzhou.When Fuzhou was located to the west of a high-pressure system(classified as“East-ridge”),more warm southwesterly currents flowed to Fuzhou,and the effects of cross-regional transport from Guangdong province and high local production promoted the occurrence of O_(3) episodes.Under a uniform pressure field with a low-pressure system occurring to the east of Fuzhou(defined as“East-low”),stagnant weather conditions caused the strongest local production of O_(3) in the atmospheric boundary layer.Controlled by high-pressure systems over the mainland(categorized as“Inland-high”),northerly airflows enhanced the contribution of cross-regional transport to O_(3) in Fuzhou.The abnormal increases of the“East-ridge”and“Inland-high”were closely related to O_(3) pollution in Fuzhou in April and May 2018,resulting in the annual maximum number of O_(3) polluted days during recent years.Furthermore,the rising number of autumn O_(3) episodes in 2017-2019 was mainly related to the“Inland-high”,indicating the aggravation of cross-regional transport and highlighting the necessity of enhanced regional collaboration and efforts in combating O_(3) pollution.

Surface ozone in global cities:A synthesis of basic features,exposure risk,and leading meteorological driving factors

Long-term exposure to high surface ozone(O_(3))concentrations,a complex oxidative atmospheric pollutant,can adversely impact human health.Based on O_(3)monitoring data from 261 cities worldwide in 2020,generalized additive model(GAM)and spatial data analysis(SDA)methods were applied in this study to quantitatively evaluate the spatiotemporal distribution of O_(3)concentration,exposure risk,and dominant meteorological factors.Results indicated that over 40%of the cities worldwide were exposed to harmful O_(3)concentration ranges(40-60μg/m^(3)),with most cities distributed in China and India.Moreover,significant seasonal variations in global O_(3)concentrations were observed,presenting as summer(45.6μg/m^(3))>spring(47.3μg/m^(3))>autumn(38.0μg/m^(3))>winter(33.6μg/m^(3)).Exposure analysis revealed that approximately 12.2%of the population in 261 cities were exposed to an environment with high O_(3)concentrations(80-160μg/m^(3)),with about 36.32 million people in major countries.Thus,the persistent increase in high O_(3)levels worldwide is a critical factor contributing to threats to human health.Furthermore,GAM results indicated temperature,relative humidity,and wind speed as primary determinants of O_(3)variability.The synergy of meteorological factors is critical for understanding O_(3)changes.Our findings are important for enforcing robust air quality policies and mitigating public risk.

Emission source-based ozone isopleth and isosurface diagrams and their significance in ozone pollution control strategies

In the past decade,ozone(O_(3))pollution has been continuously worsening in most developing countries.The accurate identification of the nonlinear relationship between O_(3) and its precursors is a prerequisite for formulating effective O_(3) control measures.At present,precursor-based O_(3) isopleth diagrams are widely used to infer O_(3) control strategy at a particular location.However,there is frequently a large gap between the O_(3)-precursor nonlinearity delineated by the O_(3) isopleths and the emission source control measures to reduce O_(3) levels.Consequently,we developed an emission source-based O_(3) isopleth diagram that directly illustrates the O_(3) level changes in response to synergistic control on two types of emission sources using a validated numerical modeling system and the latest regional emission inventory.Isopleths can be further upgraded to isosurfaces when co-control on three types of emission sources is investigated.Using Guangzhou and Foshan as examples,we demonstrate that similar precursor-based O_(3) isopleths can be associated with significantly different emission source co-control strategies.In Guangzhou,controlling solvent use emissions was the most effective approach to reduce peak O_(3) levels.In Foshan,co-control of on-road mobile,solvent use,and fixed combustion sources with a ratio of 3:1:2 or 3:1:3 was best to effectively reduce the peak O_(3) levels below 145 ppbv.This study underscores the importance of using emission source-based O_(3) isopleths and isosurface diagrams to guide a precursor emission control strategy that can effectively reduce the peak O_(3) levels in a particular area.

Functional traits of poplar leaves and fine roots responses to ozone pollution under soil nitrogen addition

Concurrent ground-level ozone(O_(3))pollution and anthropogenic nitrogen(N)deposition can markedly influence dynamics and productivity in forests.Most studies evaluating the functional traits responses of rapid-turnover organs to O_(3) have specifically examined leaves,despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems.How elevated O_(3) levels impact fine root biomass and biochemistry remains to be resolved.This study was to assess poplar leaf and fine root biomass and biochemistry responses to five different levels of O_(3) pollution,while additionally examining whether four levels of soil N supplementation were sufficient to alter the impact of O_(3) on these two organs.Elevated O_(3) resulted in a more substantial reduction in fine root biomass than leafbiomass;relative to leaves,more biochemically-resistant components were present within fine root litter,which contained high concentrations of lignin,condensed tannins,and elevated C:N and lignin:N ratios that were associated with slower rates of litter decomposition.In contrast,leaves contained more labile components,including nonstructural carbohydrates and N,as well as a higher N:P ratio.Elevated O_(3) significantly reduced labile components and increased biochemically-resistant components in leaves,whereas they had minimal impact on fine root biochemistry.This suggests that O_(3) pollution has the potential to delay leaf litter decomposition and associated nutrient cycling.N addition largely failed to affect the impact of elevated O_(3) levels on leaves or fine root chemistry,suggesting that soil N supplementation is not a suitable approach to combating the impact of O_(3) pollution on key functional traits of poplars.These results indicate that the significant differences in the responses of leaves and fine roots to O_(3) pollution will result in marked changes in the relative belowground roles of these two litter sources within forest ecosystems,and such changes will independently of nitrogen load.

Influence of surface ozone on crop yield of maize in China

This study investigated the adverse effect of surface ozone on the maize yield using a unique panel from 880 counties in China.To identify the impact of elevated surface ozone concentrations,we constructed an econometric model by controlling the impact of climate variables and related economic variables.This study also considered the potential spatial correlation in the measurement of the impact of surface ozone on maize yield.Results confirmed that the increase of ozone concentration decreased the maize yield.Moreover,maize was found to be the most sensitive to ozone at the end of the second month of the growing season.The average annual loss of maize caused by ozone pollution is about 4.234 million tons in 2013–2015,accounting for 1.9%of the average output.

Integrated ozone–photo–Fenton process for the removal of pollutant from industrial wastewater

The use of hybrid advanced oxidation processes(AOPs) for the removal of pollutants from industrial effluents has been extensively studied in recent literature. The aim of this study is to compare the performance of the photo,Fenton, photo-Fenton and ozone–photo–Fenton processes in terms of color removal and chemical oxygen demand(COD) removal of distillery industrial effluent together with the associated electrical energy per order. It was observed from the experimental results that the O_3/UV/Fe^(2 +)/H_2O_2 process yielded a 100% color and95.50% COD removals with electrical energy per order of 0.015 k W·h·m^(-3) compared to all other combinations of the AOPs. The effects of various operating parameters such as H_2O_2 and Fe^(2+) concentration, effluent pH, COD concentration and UV power on the removal of color, COD and electrical energy per order for the ozone–photo–Fenton process was critically studied and reported. The color and COD removals were analyzed using a UV/Vis spectrometer and closed reflux method.

Analysis of Ozone Behaviour in the City of Puebla-Mexico Using Non-Homogeneous Poisson Models with Multiple Change-Points

In this work, some non-homogeneous Poisson models are considered to study the behaviour of ozone in the city of Puebla, Mexico. Several functions are used as the rate function for the non-homogeneous Poisson process. In addition to their dependence on time, these rate functions also depend on some parameters that need to be estimated. In order to estimate them, a Bayesian approach will be taken. The expressions for the distributions of the parameters involved in the models are very complex. Therefore, Markov chain Monte Carlo algorithms are used to estimate them. The methodology is applied to the ozone data from the city of Puebla, Mexico.

Comparing the Adequacy of Some Non-Homogeneous Poisson Models to Estimate Ozone Exceedances in Mexico City

We consider some non-homogeneous Poisson models to estimate the mean number of times that a given environmental threshold of interest is surpassed by a given pollutant. Seven different rate functions for the Poisson processes describing the models are taken into account. The rate functions considered are the Weibull, exponentiated-Weibull, and their generalisation the Beta-Weibull rate function. We also use the Musa-Okumoto, the Goel-Okumoto, a generalised Goel- Okumoto and the Weibull-geometric rate functions. Whenever thought justifiable, the model allowing the presence of change-points is also going to be considered. The different models are applied to the daily maximum ozone measurements data provided by the monitoring network of the Metropolitan Area of Mexico City. The aim is to compare the adjustment of different rate functions to the data. Even though, some of the rate functions have been considered before, now we are applying them to the same data set. In previous works they were used in different data sets and therefore a comparison of the adequacy of those models were not possible. The measurements considered here were obtained after a series of environmental measures were implemented in Mexico City. Hence, the data present a different behaviour from that of earlier studies.

Fast spreading of surface ozone in both temporal and spatial scale in Pearl River Delta

Surface ozone(O_(3))is a major air pollutant and draw increasing attention in the Pearl River Delta(PRD),China.Here,we characterize the spatial-temporal variability of ozone based on a dataset obtained from 57 national monitoring sites during 2013-2019.Our results show that:(1)the seasonal difference of ozone distribution in the inland and coastal areas was significant,which was largely affected by the wind pattern reversals related to the East Asian monsoon,and local ozone production and destruction;(2)the daily maximum 8hr average(MDA8 O_(3))showed an overall upward trend by 1.11 ppbv/year.While the trends in the nine cities varied differently by ranging from-0.12 to 2.51 ppbv/year.The hot spots of ozone were spreading to southwestern areas from the central areas since 2016.And ozone is becoming a year-round air pollution problem with the pollution season extending to winter and spring in PRD region.(3)at the central and southwestern PRD cities,the percentage of exceedance days from the continuous type(defined as≥3 days)was increasing.Furthermore,the ozone concentration of continuous type was much higher than that of scattered exceedance type(<3 days).In addition,although the occurrence of continuous type starts to decline since2017,the total number of exceedance days during the continuous type is increasing.These results indicate that it is more difficult to eliminate the continuous exceedance than the scatter pollution days and highlight the great challenge in mitigation of O_(3)pollution in these cities.

Research on ozone formation sensitivity based on observational methods:Development history,methodology,and application and prospects in China

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.

Estimation of surface ozone concentration over Jiangsu province using a high-performance deep learning model

Recently,the global background concentration of ozone(O_(3))has demonstrated a rising trend.Among various methods,groun-basedmonitoring of O_(3)concentrations is highly reliable for research analysis.To obtain information on the spatial characteristics of O_(3)concentrations,it is necessary that the groundmonitoring sites be constructed in sufficient density.In recent years,many researchers have used machine learning models to estimate surface O_(3)concentrations,which cannot fully provide the spatial and temporal information contained in a sample dataset.To solve this problem,the current study utilized a deep learning model called the Residual connection Convolutional Long Short-Term Memory network(RConvLSTM)to estimate daily maximum8-hr average(MDA8)O_(3)over Jiangsu province,China during 2020.In this research,the R-ConvLSTM model not only provides the spatiotemporal information ofMDA8 O_(3),but also involves residual connection to avoid the problem of gradient explosion and gradient disappearance with the deepening of network layers.We utilized the TROPOMI total O_(3)column retrieved fromSentinel-5 Precursor,ERA5 reanalysismeteorological data,and other supplementary data to build a pre-trained dataset.The R-ConvLSTM model achieved an overall sample-base cross-validation(CV)R^(2)of 0.955 with root mean square error(RMSE)of 9.372μg/m^(3).Model estimation also showed a city-based CV R^(2)of 0.896 with RMSE of 14.029μg/m^(3),the highest MDA8 O_(3)in spring being 122.60±31.60μg/m^(3)and the lowest in winter being 69.93±18.48μg/m^(3).

Evaluation and Optimization of Electrode Configuration of Multi-Channel Corona Discharge Plasma for Dye-Containing Wastewater Treatment

A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment,the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density,and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration.The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance（d/s） was 0.5.Reactive Brilliant Blue（RBB） wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5,which was consistent with the result obtained in the discharge characteristics experiments.In addition,the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration.RBB degradation processes were analyzed by GC-MS and IC,and the possible mechanism for RBB decoloration was also discussed.

Enhancement of the polynomial functions response surface model for real-time analyzing ozone sensitivity

Quantification of the nonlinearities between ambient ozone(O3)and the emissions of nitrogen oxides(NOx)and volatile organic compound(VOC)is a prerequisite for an effective O3 control strategy.An Enhanced polynomial functions Response Surface Model(Epf-RSM)with the capability to analyze O3-NOx-VOC sensitivities in real time was developed by integrating the hill-climbing adaptive method into the optimized Extended Response Surface Model(ERSM)system.The Epf-RSM could single out the best suited polynomial function for each grid cell to quantify the responses of O3 concentrations to precursor emission changes.Several comparisons between Epf-RSM and pf-ERSM(polynomial functions based ERSM)were performed using out-of-sample validation,together with comparisons of the spatial distribution and the Empirical Kinetic Modeling Approach diagrams.The comparison results showed that Epf-RSM effectively addressed the drawbacks of pf-ERSM with respect to overfitting in the margin areas and high biases in the transition areas.The O3 concentrations predicted by Epf-RSM agreed well with Community Multi-scale Air Quality simulation results.The case study results in the Pearl River Delta and the north-western area of the Shandong province indicated that the O3 formations in the central areas of both the regions were more sensitive to anthropogenic VOC in January,April,and October,while more NOx-sensitive in July.

Extrapolating plot-scale CO_(2) and ozone enrichment experimental results to novel conditions and scales using mechanistic modeling

Introduction:The Aspen-FACE experiment was an 11-year study of the effect of elevated CO_(2) and ozone(alone and in combination)on the growth of model aspen communities(pure aspen,aspen-birch,and aspen-maple)in the field in northern Wisconsin,USA.Uncertainty remains about how these short-term plotlevel responses might play out over broader temporal and spatial scales where climate change,competition,succession,and disturbances interact with tree-level responses.In this study,we used a new physiologybased approach(PnET-Succession v3.1)within the forest landscape model LANDIS-II to extrapolate the FACE results to broader temporal scales(and ultimately to landscape scale)by mechanistically accounting for the globally changing drivers of temperature,precipitation,CO_(2),and ozone.We added novel algorithms to the model to mechanistically simulate the effects of ozone on photosynthesis through ozone-induced impairment of stomatal control(i.e.,stomatal sluggishness)and damage of photosynthetic capacity at the chloroplast level.Results:We calibrated the model to empirical observations of competitive interactions on the elevated CO_(2) and O_(3) plots of the Aspen-FACE experiment and successfully validated it on the combined factor plots.We used the validated model to extend the Aspen-FACE experiment for 80 years.When only aspen clones competed,we found that clone 271 always dominated,although the ozone-tolerant clone was co-dominant when ozone was present.Under all treatments,when aspen clone 216 and birch competed,birch was always dominant or co-dominant,and when clone 216 and maple competed,clone 216 was dominant,although maple was able to grow steadily because of its shade tolerance.We also predicted long-term competitive outcomes for novel assemblages of taxa under each treatment and discovered that future composition and dominant taxa depend on treatment,and that short-term trends do not always persist in the long term.Conclusions:We identified the strengths and weaknesses of PnET-Succession v3.1 and conclude that it can generate potentially robust predictions of the effects of elevated CO_(2) and ozone at landscape scales because of its mechanistically motivated algorithms.These capabilities can be used to project forest dynamics under anticipated future conditions that have no historical analog with which to parameterize less mechanistic models.

Impact of emission control on regional air quality: An observational study of air pollutants before, during and after the Beijing Olympic Games

An observational study on trace gases and PM2.5 was conducted at three sites in and around Beijing, during the Olympic season from 2007 to 2009. Air quality improved significantly during the Olympic Games due to the special emission control measures. However, concentrations of the primary pollutants and PM were found to have risen significantly after the Games. Although the major O3 precursors （NOx and VOCs） were well controlled during the Olympic season, O3 was still found to be the highest in 2008, based on the data of ground-based observation. All this information suggests that while control of regional emissions for the Beijing Olympic Games did improved the air quality in Beijing, more efforts will be needed for the continuous improvement of regional air quality, especially for significant reductions of O3 and fine particulate pollution, and not only in Beijing, but also in the B eijing-Tianjin-Hebei region.