With rapid economic growth and urbanization, the Yangtze River Delta(YRD) region in China has experienced serious air pollution challenges. In this study, we analyzed the air pollution characteristics and their relati...With rapid economic growth and urbanization, the Yangtze River Delta(YRD) region in China has experienced serious air pollution challenges. In this study, we analyzed the air pollution characteristics and their relationship with emissions and meteorology in the YRD region during 2014–2016. In recent years, the concentrations of all air pollutants, except O3,decreased. Spatially, the PM2.5, PM10, SO2, and CO concentrations were higher in the northern YRD region, and NO2 and O3 were higher in the central YRD region. Based on the number of non-attainment days(i.e., days with air quality index greater than 100), PM2.5 was the largest contributor to air pollution in the YRD region, followed by O3, PM10, and NO2.However, particulate matter pollution has declined gradually, while O3 pollution worsened.Meteorological conditions mainly influenced day-to-day variations in pollutant concentrations. PM2.5 concentration was inversely related to wind speed, while O3 concentration was positively correlated with temperature and negatively correlated with relative humidity.The air quality improvement in recent years was mainly attributed to emission reductions.During 2014–2016, PM2.5, PM10, SO2, NOx, CO, NH3, and volatile organic compound(VOC)emissions in the YRD region were reduced by 26.3%, 29.2%, 32.4%, 8.1%, 15.9%, 4.5%, and0.3%, respectively. Regional transport also contributed to the air pollution. During regional haze periods, pollutants from North China and East China aggravated the pollution in the YRD region. Our findings suggest that emission reduction and regional joint prevention and control helped to improve the air quality in the YRD region.展开更多
Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine ...Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine the physicochemical properties in atmospheric fine particles at the micrometer level, we described a sensitive and feasible surface-enhanced Raman scattering(SERS) method using Ag foil as a substrate. This novel method enhanced the Raman signal intensities up to 10,000 a.u. for ν(NO_3^-) in fine particles.The SERS effect of Ag foil was further studied experimentally and theoretically and found to have an enhancement factor of the order of ～10~4. Size-fractionated real particle samples with aerodynamic diameters of 0.4–2.5 μm were successfully collected on a heavy haze day,allowing ready observation of morphology and identification of chemical components, such as soot, nitrates, and sulfates. These results suggest that the Ag-foil-based SERS technique can be effectively used to determine the microscopic characteristics of individual fine particles, which will help to understand haze formation mechanisms and formulate governance policies.展开更多
1. Overview China overtook the US as the world＇s top emitter in 2007, and produced 1.5 times the emissions of the US by 2013 [1 ]. At pres- ent, China＇s emissions make up over a quarter of the global total. China is...1. Overview China overtook the US as the world＇s top emitter in 2007, and produced 1.5 times the emissions of the US by 2013 [1 ]. At pres- ent, China＇s emissions make up over a quarter of the global total. China is expected to produce three times the emissions of the US by 2030 [2]. Indeed, China＇s role and efforts in CO2 reductions matter greatly for the peaking of global emissions, even without further emission leakages to less-developed regions or countries. China recently announced the launch of a nation-wide emissiontrading scheme （ETS） starting in 2017 [3] in order to help deliver its emission peak by 2030. A number of climate policies in China are ongoing, and require a full performance review, effective coordination, and appropriate implementation of planning and monitoring measures along with any newly added mechanisms. This paper utilizes the latest energy and emission data to explore the impact of emission trading as a policy driver toward absolute emission and emission intensity changes in China and in its seven provinces or municipalities.展开更多
Dual carbon goals are closely related to high-quality green development.The government has required that dual car-bon goals be included in ecological civilization construction’s overall layout.Achieving carbon peak a...Dual carbon goals are closely related to high-quality green development.The government has required that dual car-bon goals be included in ecological civilization construction’s overall layout.Achieving carbon peak and carbon neutrality is a broad and profound systemic economic and social transformation.China is facing the“three highs and one short”challenges and requires the“five carbon implementations”to achieve dual carbon goals.The core of dual carbon goals is a new round of industrial competition,and the world is laying out dual carbon goals as the starting point and competing for a new round of technological high ground.展开更多
Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air poll...Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air pollution is crucial for mitigating climate change,improving air quality,and promoting the sustainable development of food systems.However,the literature lacks a comprehensive review of these interactions,particularly in the current phase of rapid development in the field.To address this gap,this study systematically reviews recent research on the impacts of climate change and air pollution on food systems,as well as the greenhouse gas and air pollutant emissions from agri-food systems and their contribution to global climate change and air pollution.In addition,this study summarizes various strategies for mitigation and adaptation,including adjustments in agricultural practices and food supply chains.Profound changes in food systems are urgently needed to enhance adaptability and reduce emissions.This review offers a critical overview of current research on the interactions among food systems,climate change,and air pollution and highlights future research directions to support the transition to sustainable food systems.展开更多
Air pollution is a major challenge to the improvement of urban environmental quality.The control of air pollution still faces severe challenges,especially in developing countries,such as ozone pollution control.Ozone ...Air pollution is a major challenge to the improvement of urban environmental quality.The control of air pollution still faces severe challenges,especially in developing countries,such as ozone pollution control.Ozone is a typical secondary air pollutant,and its formation chemistry from its precursors(NOx and volatile organic compounds)is highly nonlinear,which caused the emission reduction of its precursors is not always effective and therefore new assisted approaches to control of ozone pollution are needed.Photocatalysis and ambient catalysis technology are expected to be applied in open atmosphere as a new booster to the direct purification of air pollutants in emission sources.In this perspective,we summarize the current knowledge about the photocatalysis and ambient catalysis technology for the removal of air pollutants under natural photothermal conditions.Based on these technologies,we propose the concept of“Environmental Catalytic City”,which refers to the spontaneous purification of low concentration urban air pollutants in the atmosphere by catalytic materials coating on the artificial surfaces,such as building surfaces in the city.In this way,the urban city with self-purification function can remove air pollution without additional energy consumption.The further improvement,development,and application of the“Environmental Catalytic City”is also discussed.展开更多
Volatile organic compounds（VOCs） are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic ...Volatile organic compounds（VOCs） are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic aerosols. Vehicular evaporative emissions have become a major and growing source of VOC emissions in China. This study consists of lab tests, technology evaluation, emissions modeling, policy projections and cost-benefit analysis to draw a roadmap for China for controlling vehicular evaporative emissions. The analysis suggests that evaporative VOC emissions from China＇s light-duty gasoline vehicles were approximately 185,000 ton in 2010 and would peak at 1,200,000 ton in 2040 without control. The current control strategy implemented in China, as shown in business as usual（BAU） scenario, will barely reduce the long-term growth in emissions. Even if Stage II gasoline station vapor control policies were extended national wide（BAU ＋ extended Stage II）, there would still be over 400,000 ton fuel loss in 2050. In contrast, the implementation of on-board refueling vapor recovery（ORVR） on new cars could reduce 97.5% of evaporative VOCs by 2050（BAU ＋ ORVR/BAU ＋ delayed ORVR）. According to the results, a combined Stage II and ORVR program is a comprehensive solution that provides both short-term and long-term benefits. The net cost to achieve the optimal total evaporative VOC control is approximately 62 billion CNY in 2025 and 149 billion CNY in 2050.展开更多
Ambient particulate n-alkanes were determined for fine particle （PM2.5） samples collected from Sep 2003 to July 2004 in Beijing, China. The average concentration of total n-alkanes （∑n-alkanes） from Cll to C34 wa...Ambient particulate n-alkanes were determined for fine particle （PM2.5） samples collected from Sep 2003 to July 2004 in Beijing, China. The average concentration of total n-alkanes （∑n-alkanes） from Cll to C34 was 425.72 ng/m^3, ranged from 7.02 to 2893.28 ng/m^3. The concentration distributions of n-alkanes homologues in this study exhibited peaks at C21 and C29 in heating season, and C29 in non-heating season. The average carbon preference index （CPI） value was 1.88 in the range of 1.18-3.88. The maximum CPI in summer indicated the contribution of biogenic origins such as plant wax; while the minimum CPI value in winter was probably a result of fossil fuel combustion. Preliminary estimation from these results showed that 59% of the n-alkanes in PM2.5 in Beijing summer originated from plant wax, while 74%-88% was from fossil fuel combustion in other three seasons. Source estimation was further performed using principal component analysis method. Two major components were yielded accounting for 57.3% and 30.9% of the total variance, which presented the fossil fuel and biogenic contribution, respectively.展开更多
The nondestructive characterization of the mixing state of individual fine particles using the traditional single particle analysis technique remains a challenge.In this study,fine particles were collected during haze...The nondestructive characterization of the mixing state of individual fine particles using the traditional single particle analysis technique remains a challenge.In this study,fine particles were collected during haze events under different pollution levels from September 5 to 112017 in Beijing,China.A nondestructive surface-enhanced Raman scattering(SERS)technique was employed to investigate the morphology,chemical composition,and mixing state of the multiple components in the individual fine particles.Optical image and SERS spectral analysis results show that soot existing in the form of opaque material was predominant during clear periods(PM_(2.5)≤75μg/m^(3)).During polluted periods(PM_(2.5)>75μg/m^(3)),opaque particles mixed with transparent particles(nitrates and sulfates)were generally observed.Direct classical least squares analysis further identified the relative abundances of the three major components of the single particles:soot(69.18%),nitrates(28.71%),and sulfates(2.11%).A negative correlation was observed between the abundance of soot and the mass concentration of PM_(2.5).Furthermore,mapping analysis revealed that on hazy days,PM_(2.5)existed as a core-shell structure with soot surrounded by nitrates and sulfates.This mixing state analysis method for individual PM_(2.5)particles provides information regarding chemical composition and haze formation mechanisms,and has the potential to facilitate the formulation of haze prevention and control policies.展开更多
A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The da...A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT（Computer Programmer to calculate Emissions from Road Transport） and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5（Highway Vehicle Particulate Emission Modeling Software） models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent,which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.展开更多
A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near th...A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.展开更多
China’s emission control for nonroad diesel mobile machinery(NDMM)must deal with a fast increase in stock as well as regulations that are two decades behind those for on-road vehicles.This study provides the first la...China’s emission control for nonroad diesel mobile machinery(NDMM)must deal with a fast increase in stock as well as regulations that are two decades behind those for on-road vehicles.This study provides the first large-scale review and evaluation of China’s NDMM policies,along with emission measurements and an investigation on diesel fuel quality.The sulfur contents of the investigated diesel declined from 430 ppm(median value)in 2011 to6-8 ppm during the 2017-2018 period.The emission control of NO_(x)and PM greatly improved with the shift from the China II to China IV standards,as demonstrated by engine tests and field NO_(x)measurements.However,the NO_(x)emission factors for non-type-approved engines were approximately twice the limits of the China II standards.Emission compliance based on bench tests was not sufficient to control actual emissions because the field-measured NO_(x)emission factors of all machinery ranged from 24%to 225%greater than the respective emission limits for the engines.These circumstances adversely affected the effectiveness of the regulations and policies for China’s emission control of NDMM.Nevertheless,the policies on new and in-use NDMM,as well as diesel fuel quality,prevented NO_(x)and PM emissions amounting to 4.4 Tg and 297.8 Gg during the period 2008-2017,respectively.The emission management strategy contributed to enhancing the international competitiveness of China’s NDMM industries by promoting advanced technologies.For effective NDMM emission control in the future,portable testing and noncontact remote supervision should be strengthened;also,the issue of noncompliant diesel should be addressed through rigorous control measures and financial penalties.展开更多
Fine particles associated with haze pollution threaten the health of over 400 million people in China. Owing to excellent non-destructive fingerprint recognition characteristics, Raman and surface-enhanced Raman scatt...Fine particles associated with haze pollution threaten the health of over 400 million people in China. Owing to excellent non-destructive fingerprint recognition characteristics, Raman and surface-enhanced Raman scattering(SERS) are often used to analyze the composition of fine particles to determine their physical and chemical properties as well as reaction mechanisms. However, there is no comprehensive Raman spectral library of fine particles. Furthermore, various studies that used SERS for fine-particle composition analysis showed that the uniqueness of the SERS substrates and different excitation wavelengths can produce a different spectrum for the same fine-particle component. To overcome this limitation, we conducted SERS experiments with a portable Raman spectrometer using two common SERS substrates(silver(Ag) foil and gold nanoparticles(Au NPs)) and a 785 nm laser. Herein, we introduced three main particle component types(sulfate-nitrate-ammonium(SNA), organic material, and soot) with a total of 39 chemical substances. We scanned the solid Raman, liquid Raman, and SERS spectra of these substances and constructed a fine-particle reference library containing 105 spectra. Spectral results indicated that for soot and SNA, the differences in characteristic peaks mainly originated from the solid-liquid phase transition;Ag foil had little effect on this difference, while the Au NPs caused a significant red shift in the peak positions of polycyclic aromatic hydrocarbons. Moreover, with various characteristic peak positions in the three types of spectra, we could quickly and correctly distinguish substances. We hope that this spectral library will aid in the future identification of fine particles.展开更多
The response to climate change and air pollution control demonstrates strong synergy across scientific mechanisms,targets,strategies,and governance systems.This report,based on a monitoring indicator system for coordi...The response to climate change and air pollution control demonstrates strong synergy across scientific mechanisms,targets,strategies,and governance systems.This report,based on a monitoring indicator system for coordinated governance of air pollution and climate change,employs an interdisciplinary approach combining natural and social sciences.It establishes 20 indicators across five key areas:air pollution and climate change,governance systems and practices,structural transformation and technologies,atmospheric components and emission reduction pathways,and health impacts and cobenefits.This report tries to provide actionable insights into the interconnectedness of air pollution and climate governance.It highlights key policy gaps,presents updated indicators,and offers a refined monitoring framework to track progress toward China's dual goals of reducing emissions and improving air quality.Compared to previous editions,this year's report has updated four key indicators:meteorological impacts on air quality,climate change and its effects,governance policies,and low-carbon building energy systems.The aim is to further refine the monitoring framework,track progress,and establish a comprehensive theory for collaborative governance while identifying challenges and proposing solutions for China's pathway to carbon neutrality and clean air.The report comprises six chapters.The executive summary chapter is followed by analyzing air pollution and climate change interactions.Governance systems and practices are discussed in the third chapter,focusing on policy implementation and local experiences.The fourth chapter addresses structural transformations and emission reduction technologies,including energy and industrial shifts,transportation,low-carbon buildings,carbon capture and storage,and power systems.The fifth chapter outlines atmospheric component dynamics and emission pathways,presenting insights into emission drivers and future strategies.The sixth chapter assesses health impacts and the benefits of coordinated actions.Since 2019,China Clean Air Policy Partnership has produced annual reports on China's progress in climate and air pollution governance,receiving positive feedback.In 2023,the report was co-developed with Tsinghua University's Carbon Neutrality Research Institute,involving over 100 experts and multiple academic forums.The collaboration aims to continuously improve the indicator system and establish the report as a key resource supporting China's efforts in pollution reduction,carbon mitigation,greening,and sustainable growth.展开更多
Currently,over 80%of the international trade volume is carried by sea.Marked by persistent growth,evident atmospheric impacts,intricate mitigation challenges,international shipping has been recognized as one of the m...Currently,over 80%of the international trade volume is carried by sea.Marked by persistent growth,evident atmospheric impacts,intricate mitigation challenges,international shipping has been recognized as one of the most“hard-to-abate”sectors gathering increasing attention from both academic community and governmental sectors in recent years.Against the backdrop of the ambitious climate and clean air objectives,the quantitative shipping emission characterization,impact assessment and policy effectiveness research are not only fundamental to understand the status quo and ramifications of shipping emissions but also beneficial for future emission regulations.Here,we summarized the achievements in shipping emission modelling and impact research in the past two decades,and identified the challenges lying in the transition pathway towards a clean and carbon-neutral shipping.To address the pressing demand for this,we proposed an innovative framework which aims to facilitate emission abatement.Finally,promising directions for future work were delineated,including the indirect effects of shipping emitted aerosols on the climate,the emissions and impacts of novel contaminants,synergies and conflicts among different emission reduction measures,projections on future shipping emission inventories,Arctic shipping emissions,etc.展开更多
The lack of toolkits for assessing the shipping-related atmospheric impacts limits China's ability to formulate effective shipping emissions control policies to address coastal air pollution and mitigate related h...The lack of toolkits for assessing the shipping-related atmospheric impacts limits China's ability to formulate effective shipping emissions control policies to address coastal air pollution and mitigate related health burdens.Here,we developed a deep learning model,DeepShip,to efficiently predict shipping-related PM_(2.5)concentrations and further coupled it with a multi-task learning and generative-adversarial training strategy to enhance the sensitivity of the data-driven model to variations in small emission sources.Based on DeepShip,we comprehensively analyzed the response of shipping-related PM_(2.5)to changes in anthropogenic emissions based on 210 scenarios involving emission reductions of shipping and land-based sectors.Furthermore,sulfur and nitrogen emission control scenarios that China might implement in the future were established to assess their cost,air quality improvement,and health benefits.We found that shipping-related PM_(2.5)shows an almost linear relationship with shipping emissions,while exhibiting a nonlinear relationship with land-based emissions.Considering the cost and environmental-health benefits,future shipping emissions control should prioritize progressively enhancing the NOx emission standard while coordinating with land-based emission reductions.展开更多
Exposure to fine particulate matter(PM2.5)is known to harm public health.In China,after implementation of aggressive emissions control measures under the Action Plan of Air Pollution Prevention and Control(2013-2017),...Exposure to fine particulate matter(PM2.5)is known to harm public health.In China,after implementation of aggressive emissions control measures under the Action Plan of Air Pollution Prevention and Control(2013-2017),air quality has significantly improved.In this work,we investigated changes in PM2.5 exposure and the associated health impacts in China for the period 2013-2017.We used an optimal estimator of PM2.5 combining in-situ observations,satellite measurements,and simulations from a chemical transport model to derive the spatial and temporal variations in PM2.5 exposure,and then used welldeveloped exposure-response functions to estimate the premature deaths attributable to PM2.5 exposure.We found that national population-weighed annual mean PM2.5 concentrations decreased from 67.4μgm-3 in 2013 to 45.5μgm-3 in 2017(32%reduction).This rapid decrease in PM2.5 pollution led to a 14%reduction in premature deaths due to long-term exposure.We estimated that,during 2013-2017,the premature deaths attributable to long-term PM2.5 exposure decreased from 1.2 million(95%CI:1.0,1.3;fraction of total mortality:13%)in 2013 to 1.0 million(95%CI:0.9,1.2;10%)in 2017.Despite the rapid decrease in annual mean PM2.5 concentrations,health benefits associated with reduced long-term exposure were limited,because for many cities,the PM2.5 levels remain at the portion where the exposure-response function is less steeper than that at the lowconcentration end.We also found that the deaths associated with acute exposure decreased by 61%during 2013-2017 due to rapid reduction in the number of heavily polluted days.Our results confirm that clean air policies in China have mitigated the air pollution crisis;however,continuous emissions reduction efforts are required to protect citizens from air pollution.展开更多
China promulgated the Air Pollution Prevention and Control Action Plan(the Action Plan)in 2013 and developed stringent control measures to mitigate fine particulate matter(PM2.5) pollution.Here,we investigated the PM2...China promulgated the Air Pollution Prevention and Control Action Plan(the Action Plan)in 2013 and developed stringent control measures to mitigate fine particulate matter(PM2.5) pollution.Here,we investigated the PM2.5 chemical composition changes over eastern China associated with the Action Plan during 2013-2017 using satellite-based PM2.5 chemical composition data derived using CMAQ simulations and satellite inputs.The PM2.5 concentrations decreased considerably during this time as a result of the reductions in all chemical species in PM2.5.The population-weighted mean concentrations over eastern China decreased from 11.1 to 6.7μgm-3 for SO42-,13.8-13.1μgm-3 for NO3-,7.4-5.8μgm-3 for NH4+,9.9-8.4μgm-3 for OM,4.6-3.8μg m-3 for BC and 12.9-9.6μg m-3 for other species in PM2.5.SO42-had the largest reduction of 40%,while NO3-had the lowest reduction of 5%,resulting in a greater fraction of NO3-and a smaller fraction of SO42-in PM2.5.Among the three key regions,Beijing-Tianjin-Hebei had the largest reduction in PM2.5 and its chemical compositions.The decrease in SO42-concentrations was in line with the reduction of SO2 emissions,and the major driver of the SO2 emission reductions was the industrial sector.The decrease in NO3 concentrations was limited because the decrease in SO2 emissions and the stable NH3 emissions facilitated the formation of NO3-from HNO3,which partially offset the reduction in NOx emissions driven by the power sector.To mitigate PM2.5 pollution more effectively,future efforts are needed to reduce NH3 emissions.展开更多
基金supported by the National Science and Technology Program of China(Nos.2017YFC0211601,2016YFC0202700)the National Natural Science Foundation of China(No.81571130090)the National Research Program for Key Issues in Air Pollution Control(No.DQGG0103)
文摘With rapid economic growth and urbanization, the Yangtze River Delta(YRD) region in China has experienced serious air pollution challenges. In this study, we analyzed the air pollution characteristics and their relationship with emissions and meteorology in the YRD region during 2014–2016. In recent years, the concentrations of all air pollutants, except O3,decreased. Spatially, the PM2.5, PM10, SO2, and CO concentrations were higher in the northern YRD region, and NO2 and O3 were higher in the central YRD region. Based on the number of non-attainment days(i.e., days with air quality index greater than 100), PM2.5 was the largest contributor to air pollution in the YRD region, followed by O3, PM10, and NO2.However, particulate matter pollution has declined gradually, while O3 pollution worsened.Meteorological conditions mainly influenced day-to-day variations in pollutant concentrations. PM2.5 concentration was inversely related to wind speed, while O3 concentration was positively correlated with temperature and negatively correlated with relative humidity.The air quality improvement in recent years was mainly attributed to emission reductions.During 2014–2016, PM2.5, PM10, SO2, NOx, CO, NH3, and volatile organic compound(VOC)emissions in the YRD region were reduced by 26.3%, 29.2%, 32.4%, 8.1%, 15.9%, 4.5%, and0.3%, respectively. Regional transport also contributed to the air pollution. During regional haze periods, pollutants from North China and East China aggravated the pollution in the YRD region. Our findings suggest that emission reduction and regional joint prevention and control helped to improve the air quality in the YRD region.
基金supported by the National Natural Science Foundation of China (Nos.21707077,81571130090)the National Key Research and Development Program (Nos.2017YFC0211500,2016YFC0202700,2017YFC0211601)+1 种基金the Science Fund for Creative Research Groups (No.21521064)the China Postdoctoral Science Foundation (No.2017M610923)
文摘Fine particles associated with haze pollution threaten the health of more than 400 million people in China. It is therefore of great importance to thoroughly investigate and understand their composition. To determine the physicochemical properties in atmospheric fine particles at the micrometer level, we described a sensitive and feasible surface-enhanced Raman scattering(SERS) method using Ag foil as a substrate. This novel method enhanced the Raman signal intensities up to 10,000 a.u. for ν(NO_3^-) in fine particles.The SERS effect of Ag foil was further studied experimentally and theoretically and found to have an enhancement factor of the order of ～10~4. Size-fractionated real particle samples with aerodynamic diameters of 0.4–2.5 μm were successfully collected on a heavy haze day,allowing ready observation of morphology and identification of chemical components, such as soot, nitrates, and sulfates. These results suggest that the Ag-foil-based SERS technique can be effectively used to determine the microscopic characteristics of individual fine particles, which will help to understand haze formation mechanisms and formulate governance policies.
文摘1. Overview China overtook the US as the world＇s top emitter in 2007, and produced 1.5 times the emissions of the US by 2013 [1 ]. At pres- ent, China＇s emissions make up over a quarter of the global total. China is expected to produce three times the emissions of the US by 2030 [2]. Indeed, China＇s role and efforts in CO2 reductions matter greatly for the peaking of global emissions, even without further emission leakages to less-developed regions or countries. China recently announced the launch of a nation-wide emissiontrading scheme （ETS） starting in 2017 [3] in order to help deliver its emission peak by 2030. A number of climate policies in China are ongoing, and require a full performance review, effective coordination, and appropriate implementation of planning and monitoring measures along with any newly added mechanisms. This paper utilizes the latest energy and emission data to explore the impact of emission trading as a policy driver toward absolute emission and emission intensity changes in China and in its seven provinces or municipalities.
文摘Dual carbon goals are closely related to high-quality green development.The government has required that dual car-bon goals be included in ecological civilization construction’s overall layout.Achieving carbon peak and carbon neutrality is a broad and profound systemic economic and social transformation.China is facing the“three highs and one short”challenges and requires the“five carbon implementations”to achieve dual carbon goals.The core of dual carbon goals is a new round of industrial competition,and the world is laying out dual carbon goals as the starting point and competing for a new round of technological high ground.
基金supported by the National Natural Science Foundation of China(42277087,42130708,42471021,42277482,and 42361144876)the Natural Science Foundation of Guangdong Province(2024A1515012550)+3 种基金the Hainan Institute of National Park grant(KY-23ZK01)the Tsinghua Shenzhen International Graduate School Cross-disciplinary Research and Innovation Fund Research Plan(JC2022011)the Shenzhen Science and Technology Program(JCYJ20240813112106009 and ZDSYS20220606100806014)the Scientific Research Start-up Funds(QD2021030C)from Tsinghua Shenzhen International Graduate School。
文摘Food systems are deeply affected by climate change and air pollution,while being key contributors to these environmental challenges.Understanding the complex interactions among food systems,climate change,and air pollution is crucial for mitigating climate change,improving air quality,and promoting the sustainable development of food systems.However,the literature lacks a comprehensive review of these interactions,particularly in the current phase of rapid development in the field.To address this gap,this study systematically reviews recent research on the impacts of climate change and air pollution on food systems,as well as the greenhouse gas and air pollutant emissions from agri-food systems and their contribution to global climate change and air pollution.In addition,this study summarizes various strategies for mitigation and adaptation,including adjustments in agricultural practices and food supply chains.Profound changes in food systems are urgently needed to enhance adaptability and reduce emissions.This review offers a critical overview of current research on the interactions among food systems,climate change,and air pollution and highlights future research directions to support the transition to sustainable food systems.
基金the support of the National Natural Science Foundation of China(NSFC)(Nos.52425003,22188102,and 52400144)the Project funded by China Postdoctoral Science Foundation(Nos.BX20220325 and 2023M743707)the Youth Innovation Promotion Association,CAS(Nos.Y2021020 and Y2022023).
文摘Air pollution is a major challenge to the improvement of urban environmental quality.The control of air pollution still faces severe challenges,especially in developing countries,such as ozone pollution control.Ozone is a typical secondary air pollutant,and its formation chemistry from its precursors(NOx and volatile organic compounds)is highly nonlinear,which caused the emission reduction of its precursors is not always effective and therefore new assisted approaches to control of ozone pollution are needed.Photocatalysis and ambient catalysis technology are expected to be applied in open atmosphere as a new booster to the direct purification of air pollutants in emission sources.In this perspective,we summarize the current knowledge about the photocatalysis and ambient catalysis technology for the removal of air pollutants under natural photothermal conditions.Based on these technologies,we propose the concept of“Environmental Catalytic City”,which refers to the spontaneous purification of low concentration urban air pollutants in the atmosphere by catalytic materials coating on the artificial surfaces,such as building surfaces in the city.In this way,the urban city with self-purification function can remove air pollution without additional energy consumption.The further improvement,development,and application of the“Environmental Catalytic City”is also discussed.
基金supported by the National Natural Science Foundation of China (No. 71101078)the National High Technology Research and Development Program of China (No. 2013AA065303D)the National Environmental Protection Public Welfare Research Fund (No. 201209003 and No.201409021)
文摘Volatile organic compounds（VOCs） are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic aerosols. Vehicular evaporative emissions have become a major and growing source of VOC emissions in China. This study consists of lab tests, technology evaluation, emissions modeling, policy projections and cost-benefit analysis to draw a roadmap for China for controlling vehicular evaporative emissions. The analysis suggests that evaporative VOC emissions from China＇s light-duty gasoline vehicles were approximately 185,000 ton in 2010 and would peak at 1,200,000 ton in 2040 without control. The current control strategy implemented in China, as shown in business as usual（BAU） scenario, will barely reduce the long-term growth in emissions. Even if Stage II gasoline station vapor control policies were extended national wide（BAU ＋ extended Stage II）, there would still be over 400,000 ton fuel loss in 2050. In contrast, the implementation of on-board refueling vapor recovery（ORVR） on new cars could reduce 97.5% of evaporative VOCs by 2050（BAU ＋ ORVR/BAU ＋ delayed ORVR）. According to the results, a combined Stage II and ORVR program is a comprehensive solution that provides both short-term and long-term benefits. The net cost to achieve the optimal total evaporative VOC control is approximately 62 billion CNY in 2025 and 149 billion CNY in 2050.
基金supported by the General Motors, the National Excellent Doctoral Dissertation Author Funds of the Ministry of Education of China (No. 2007B57)the Special Research Fund for the Doctoral Program of the Ministry of Education of China (No. 200800031033)+1 种基金the Special Fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (No. 09Z04ESPCT)the National Science Foundation for the Distinguished YoungScholars (No. 20625722)
文摘Ambient particulate n-alkanes were determined for fine particle （PM2.5） samples collected from Sep 2003 to July 2004 in Beijing, China. The average concentration of total n-alkanes （∑n-alkanes） from Cll to C34 was 425.72 ng/m^3, ranged from 7.02 to 2893.28 ng/m^3. The concentration distributions of n-alkanes homologues in this study exhibited peaks at C21 and C29 in heating season, and C29 in non-heating season. The average carbon preference index （CPI） value was 1.88 in the range of 1.18-3.88. The maximum CPI in summer indicated the contribution of biogenic origins such as plant wax; while the minimum CPI value in winter was probably a result of fossil fuel combustion. Preliminary estimation from these results showed that 59% of the n-alkanes in PM2.5 in Beijing summer originated from plant wax, while 74%-88% was from fossil fuel combustion in other three seasons. Source estimation was further performed using principal component analysis method. Two major components were yielded accounting for 57.3% and 30.9% of the total variance, which presented the fossil fuel and biogenic contribution, respectively.
基金supported by the National Natural Science Foundation of China(Nos.21707077,21775042)the National Key Research and Development Program of China(No.2017YFA0207003)the Fundamental Research Funds for the Central Universities(No.2020 MS037)。
文摘The nondestructive characterization of the mixing state of individual fine particles using the traditional single particle analysis technique remains a challenge.In this study,fine particles were collected during haze events under different pollution levels from September 5 to 112017 in Beijing,China.A nondestructive surface-enhanced Raman scattering(SERS)technique was employed to investigate the morphology,chemical composition,and mixing state of the multiple components in the individual fine particles.Optical image and SERS spectral analysis results show that soot existing in the form of opaque material was predominant during clear periods(PM_(2.5)≤75μg/m^(3)).During polluted periods(PM_(2.5)>75μg/m^(3)),opaque particles mixed with transparent particles(nitrates and sulfates)were generally observed.Direct classical least squares analysis further identified the relative abundances of the three major components of the single particles:soot(69.18%),nitrates(28.71%),and sulfates(2.11%).A negative correlation was observed between the abundance of soot and the mass concentration of PM_(2.5).Furthermore,mapping analysis revealed that on hazy days,PM_(2.5)existed as a core-shell structure with soot surrounded by nitrates and sulfates.This mixing state analysis method for individual PM_(2.5)particles provides information regarding chemical composition and haze formation mechanisms,and has the potential to facilitate the formulation of haze prevention and control policies.
基金supported by the National Science Foundation of China (Nos. 41275124, 51278272)the Beijing Natural Science Foundation (8142011)+1 种基金the Ministry of Environmental Protection of China (No. 201209007)the International Council on Clean Transportation (ICCT) research program
文摘A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT（Computer Programmer to calculate Emissions from Road Transport） and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5（Highway Vehicle Particulate Emission Modeling Software） models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent,which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.
基金supported by the National Natural Science Foundation of China (No.41605095)the Beijing Natural Science Foundation (No.JQ19030)+1 种基金the Beijing Municipal Commission of Education (No.PXM2019014213000007)the School Level Cultivation Fund of Beijing Technology and Business University for Distinguished and Excellent Young Scholars (No.BTBUYP2020)。
文摘A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.
基金supported by the National Key Research and Development Program(Nos.2019YFC0214800 and 2016YFC0208004)the National Natural Science Foundation of China(Nos.41822505 and 42061130213)+1 种基金supported by the Royal Society of the UK through the Newton Advanced Fellowship(No.NAFR1201166)the Tsinghua University Initiative Scientific Research Program(No.2019Z02CAU)。
文摘China’s emission control for nonroad diesel mobile machinery(NDMM)must deal with a fast increase in stock as well as regulations that are two decades behind those for on-road vehicles.This study provides the first large-scale review and evaluation of China’s NDMM policies,along with emission measurements and an investigation on diesel fuel quality.The sulfur contents of the investigated diesel declined from 430 ppm(median value)in 2011 to6-8 ppm during the 2017-2018 period.The emission control of NO_(x)and PM greatly improved with the shift from the China II to China IV standards,as demonstrated by engine tests and field NO_(x)measurements.However,the NO_(x)emission factors for non-type-approved engines were approximately twice the limits of the China II standards.Emission compliance based on bench tests was not sufficient to control actual emissions because the field-measured NO_(x)emission factors of all machinery ranged from 24%to 225%greater than the respective emission limits for the engines.These circumstances adversely affected the effectiveness of the regulations and policies for China’s emission control of NDMM.Nevertheless,the policies on new and in-use NDMM,as well as diesel fuel quality,prevented NO_(x)and PM emissions amounting to 4.4 Tg and 297.8 Gg during the period 2008-2017,respectively.The emission management strategy contributed to enhancing the international competitiveness of China’s NDMM industries by promoting advanced technologies.For effective NDMM emission control in the future,portable testing and noncontact remote supervision should be strengthened;also,the issue of noncompliant diesel should be addressed through rigorous control measures and financial penalties.
基金supported by National Natural Science Foundation of China (Nos. 21707077, 21775042, and 21475134)the National Key Research and Development Program of China (No. 2017YFA0207003)+1 种基金the Special Fund of Beijing Key Laboratory of Indoor Air Quality Evaluation and Control (No. BZ0344KF2006)the Fundamental Research Funds for the Central Universities (No. 2020MS037)。
文摘Fine particles associated with haze pollution threaten the health of over 400 million people in China. Owing to excellent non-destructive fingerprint recognition characteristics, Raman and surface-enhanced Raman scattering(SERS) are often used to analyze the composition of fine particles to determine their physical and chemical properties as well as reaction mechanisms. However, there is no comprehensive Raman spectral library of fine particles. Furthermore, various studies that used SERS for fine-particle composition analysis showed that the uniqueness of the SERS substrates and different excitation wavelengths can produce a different spectrum for the same fine-particle component. To overcome this limitation, we conducted SERS experiments with a portable Raman spectrometer using two common SERS substrates(silver(Ag) foil and gold nanoparticles(Au NPs)) and a 785 nm laser. Herein, we introduced three main particle component types(sulfate-nitrate-ammonium(SNA), organic material, and soot) with a total of 39 chemical substances. We scanned the solid Raman, liquid Raman, and SERS spectra of these substances and constructed a fine-particle reference library containing 105 spectra. Spectral results indicated that for soot and SNA, the differences in characteristic peaks mainly originated from the solid-liquid phase transition;Ag foil had little effect on this difference, while the Au NPs caused a significant red shift in the peak positions of polycyclic aromatic hydrocarbons. Moreover, with various characteristic peak positions in the three types of spectra, we could quickly and correctly distinguish substances. We hope that this spectral library will aid in the future identification of fine particles.
基金supported by the National Key Research and Development Program of China(2022YFC3702704)the National Natural Science Foundation of China(42293324)the Energy Foundation,China.
文摘The response to climate change and air pollution control demonstrates strong synergy across scientific mechanisms,targets,strategies,and governance systems.This report,based on a monitoring indicator system for coordinated governance of air pollution and climate change,employs an interdisciplinary approach combining natural and social sciences.It establishes 20 indicators across five key areas:air pollution and climate change,governance systems and practices,structural transformation and technologies,atmospheric components and emission reduction pathways,and health impacts and cobenefits.This report tries to provide actionable insights into the interconnectedness of air pollution and climate governance.It highlights key policy gaps,presents updated indicators,and offers a refined monitoring framework to track progress toward China's dual goals of reducing emissions and improving air quality.Compared to previous editions,this year's report has updated four key indicators:meteorological impacts on air quality,climate change and its effects,governance policies,and low-carbon building energy systems.The aim is to further refine the monitoring framework,track progress,and establish a comprehensive theory for collaborative governance while identifying challenges and proposing solutions for China's pathway to carbon neutrality and clean air.The report comprises six chapters.The executive summary chapter is followed by analyzing air pollution and climate change interactions.Governance systems and practices are discussed in the third chapter,focusing on policy implementation and local experiences.The fourth chapter addresses structural transformations and emission reduction technologies,including energy and industrial shifts,transportation,low-carbon buildings,carbon capture and storage,and power systems.The fifth chapter outlines atmospheric component dynamics and emission pathways,presenting insights into emission drivers and future strategies.The sixth chapter assesses health impacts and the benefits of coordinated actions.Since 2019,China Clean Air Policy Partnership has produced annual reports on China's progress in climate and air pollution governance,receiving positive feedback.In 2023,the report was co-developed with Tsinghua University's Carbon Neutrality Research Institute,involving over 100 experts and multiple academic forums.The collaboration aims to continuously improve the indicator system and establish the report as a key resource supporting China's efforts in pollution reduction,carbon mitigation,greening,and sustainable growth.
基金supported by National Natural Science Foundation of China(42325505 and U2233203 to H.L.)National Key Research and Development Program of China(2022YFC3704200).
文摘Currently,over 80%of the international trade volume is carried by sea.Marked by persistent growth,evident atmospheric impacts,intricate mitigation challenges,international shipping has been recognized as one of the most“hard-to-abate”sectors gathering increasing attention from both academic community and governmental sectors in recent years.Against the backdrop of the ambitious climate and clean air objectives,the quantitative shipping emission characterization,impact assessment and policy effectiveness research are not only fundamental to understand the status quo and ramifications of shipping emissions but also beneficial for future emission regulations.Here,we summarized the achievements in shipping emission modelling and impact research in the past two decades,and identified the challenges lying in the transition pathway towards a clean and carbon-neutral shipping.To address the pressing demand for this,we proposed an innovative framework which aims to facilitate emission abatement.Finally,promising directions for future work were delineated,including the indirect effects of shipping emitted aerosols on the climate,the emissions and impacts of novel contaminants,synergies and conflicts among different emission reduction measures,projections on future shipping emission inventories,Arctic shipping emissions,etc.
基金supported by Jing-Jin-Ji Regional Integrated Environmental Improvement-National Science and Technology Major Project(2025ZD1202004)National Natural Science Foundation of China(42325505)+1 种基金the China National Postdoctoral Program for Innovative Talents(BX20250327)the Shuimu Tsinghua Scholar Program(2024SM028).
文摘The lack of toolkits for assessing the shipping-related atmospheric impacts limits China's ability to formulate effective shipping emissions control policies to address coastal air pollution and mitigate related health burdens.Here,we developed a deep learning model,DeepShip,to efficiently predict shipping-related PM_(2.5)concentrations and further coupled it with a multi-task learning and generative-adversarial training strategy to enhance the sensitivity of the data-driven model to variations in small emission sources.Based on DeepShip,we comprehensively analyzed the response of shipping-related PM_(2.5)to changes in anthropogenic emissions based on 210 scenarios involving emission reductions of shipping and land-based sectors.Furthermore,sulfur and nitrogen emission control scenarios that China might implement in the future were established to assess their cost,air quality improvement,and health benefits.We found that shipping-related PM_(2.5)shows an almost linear relationship with shipping emissions,while exhibiting a nonlinear relationship with land-based emissions.Considering the cost and environmental-health benefits,future shipping emissions control should prioritize progressively enhancing the NOx emission standard while coordinating with land-based emission reductions.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41571130032, 41571130035, 41625020 & 41701591)the National Key R & D Program (Grant No. 2016YFC0201506)
文摘Exposure to fine particulate matter(PM2.5)is known to harm public health.In China,after implementation of aggressive emissions control measures under the Action Plan of Air Pollution Prevention and Control(2013-2017),air quality has significantly improved.In this work,we investigated changes in PM2.5 exposure and the associated health impacts in China for the period 2013-2017.We used an optimal estimator of PM2.5 combining in-situ observations,satellite measurements,and simulations from a chemical transport model to derive the spatial and temporal variations in PM2.5 exposure,and then used welldeveloped exposure-response functions to estimate the premature deaths attributable to PM2.5 exposure.We found that national population-weighed annual mean PM2.5 concentrations decreased from 67.4μgm-3 in 2013 to 45.5μgm-3 in 2017(32%reduction).This rapid decrease in PM2.5 pollution led to a 14%reduction in premature deaths due to long-term exposure.We estimated that,during 2013-2017,the premature deaths attributable to long-term PM2.5 exposure decreased from 1.2 million(95%CI:1.0,1.3;fraction of total mortality:13%)in 2013 to 1.0 million(95%CI:0.9,1.2;10%)in 2017.Despite the rapid decrease in annual mean PM2.5 concentrations,health benefits associated with reduced long-term exposure were limited,because for many cities,the PM2.5 levels remain at the portion where the exposure-response function is less steeper than that at the lowconcentration end.We also found that the deaths associated with acute exposure decreased by 61%during 2013-2017 due to rapid reduction in the number of heavily polluted days.Our results confirm that clean air policies in China have mitigated the air pollution crisis;however,continuous emissions reduction efforts are required to protect citizens from air pollution.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41571130032 & 41571130035)the National Key R & D Program (Grant No. 2016YFC0201506)supported by the MAIA science team at the JPL, California Institute of Technology (Grant No. 1588347)
文摘China promulgated the Air Pollution Prevention and Control Action Plan(the Action Plan)in 2013 and developed stringent control measures to mitigate fine particulate matter(PM2.5) pollution.Here,we investigated the PM2.5 chemical composition changes over eastern China associated with the Action Plan during 2013-2017 using satellite-based PM2.5 chemical composition data derived using CMAQ simulations and satellite inputs.The PM2.5 concentrations decreased considerably during this time as a result of the reductions in all chemical species in PM2.5.The population-weighted mean concentrations over eastern China decreased from 11.1 to 6.7μgm-3 for SO42-,13.8-13.1μgm-3 for NO3-,7.4-5.8μgm-3 for NH4+,9.9-8.4μgm-3 for OM,4.6-3.8μg m-3 for BC and 12.9-9.6μg m-3 for other species in PM2.5.SO42-had the largest reduction of 40%,while NO3-had the lowest reduction of 5%,resulting in a greater fraction of NO3-and a smaller fraction of SO42-in PM2.5.Among the three key regions,Beijing-Tianjin-Hebei had the largest reduction in PM2.5 and its chemical compositions.The decrease in SO42-concentrations was in line with the reduction of SO2 emissions,and the major driver of the SO2 emission reductions was the industrial sector.The decrease in NO3 concentrations was limited because the decrease in SO2 emissions and the stable NH3 emissions facilitated the formation of NO3-from HNO3,which partially offset the reduction in NOx emissions driven by the power sector.To mitigate PM2.5 pollution more effectively,future efforts are needed to reduce NH3 emissions.
