Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AO...Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AOC still remains uncertainty.In this study,a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing,where O_(3) and PM_(2.5) episodes had been experienced successively.The observation-based model(OBM)is used to quantify the AOC at O_(3) and PM_(2.5) episodes.The strong intensity of AOC is found at O_(3) and PM2.5 episodes,and hydroxyl radical(OH)is the dominating daytime oxidant for both episodes.The photolysis of O_(3) is main source of OH at O_(3) episode;the photolysis of nitrous acid(HONO)and formaldehyde(HCHO)plays important role in OH formation at PM_(2.5) episode.The radicals loss routines vary according to precursor pollutants,resulting in different types of air pollution.O_(3) budgets and sensitivity analysis indicates that O_(3) production is transition regime(both VOC and NOx-limited)at O3 episode.The heterogeneous reaction of hydroperoxy radicals(HO_(2))on aerosol surfaces has significant influence on OH and O_(3) production rates.The HO_(2) uptake coefficient(γHO_(2))is the determining factor and required accurate measurement in real atmospheric environment.Our findings could provide the important bases for coordinated control of PM_(2.5) and O_(3) pollution.展开更多
Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China,in contrast to the fact that an increase in emissions of non-methane hydrocarbons(NMHCs)has b...Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China,in contrast to the fact that an increase in emissions of non-methane hydrocarbons(NMHCs)has been reported.This study employed seven years continuous NMHCsmeasurements and the related activities data of Shanghai,a megacity in China,to explore evolution of emissions and effectiveness of air pollution control measures.The mixing ratio of NMHCs showed no statistical interannual changes,of which their compositions exhibited marked changes.This resulted in a decreasing trend of ozone formation potential by 3.8%/year(p<0.05,the same below),which should be beneficial to ozone pollution mitigation as its production in Shanghai is in the NMHCs-limited regime.Observed alkanes,aromatics and acetylene changed by+3.7%/year,-5.9%/year and-7.4%/year,respectively,and alkenes showed no apparent trend.NMHCs sources were apportioned by a positive matrix factorization model.Accordingly,vehicular emissions(-5.9%/year)and petrochemical industry emissions(-7.1%/year)decreased significantly,but the decrease slowed down;significant reduction in solvent usage(-9.0%/year)appeared after 2010;however,emissions of natural gas(+12.6%/year)and fuel evaporation(with an increasing fraction)became more important.The inconsistency between observations and inventories was found in interannual trend and speciation as well as source contributions,emphasizing the need for further validation in NMHCs emission inventory.Our study confirms the effectiveness of measures targeting mobile and centralized emissions from industrial sources and reveals a need focusing on fugitive emissions,which provided new insights into future air policies in polluted region.展开更多
Acetaldehyde plays a significant role in atmospheric photochemical reactions and ozone formation.Previous studies have shown that acetaldehyde may rapidly be generated over short periods and impact ozone production,ye...Acetaldehyde plays a significant role in atmospheric photochemical reactions and ozone formation.Previous studies have shown that acetaldehyde may rapidly be generated over short periods and impact ozone production,yet the underlyingmechanism remains unclear.To better elucidate thesemechanisms,a field campaign was conducted in Dongying,a typical petrochemical city in China.The observed acetaldehyde concentration averaged 3.0±1.6 ppbv,with a peak around 09:00 local time.The diurnal variations of acetaldehyde were categorized into two types,with Category 1 exhibiting relatively high values and increasing sharply in concentration between 07:00 and 09:00 a.m.(refer to morning peak episode,MPE),and the remaining classified as Category 2.Category 1 was similar to previous studies at heavily polluted sites but differed fromcleaner locations.Using an observation-based chemical box model,we found that acetaldehyde contributed an average of 10.2%to the net ozone production rate.Combined with a positive matrix factorizationmodel,we identified secondary formation as the dominant source of acetaldehyde(45.0%),and the daytime production rate of acetaldehyde in Category 1 was significantly higher than that in Category 2.Cis-2-butene and trans-2-butene were identified as key precursors for the rapid acetaldehyde formation during the MEP,with the petroleum industry being their primary source.Volatile organic compounds(VOCs)from petroleum industry contributed over 60%to acetaldehyde formation during the morning peak.Our findings underscore the urgent need for targeted VOCs management strategies in petroleum sector tomitigate both carbonyl and ozone formation.展开更多
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 forma...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.展开更多
The petroleum industry is a significant source of anthropogenic volatile organic compounds(VOCs),but up to now,its exact impact on urban VOCs and ozone(O_(3))remains unclear.This study conducted year-long VOC ob-serva...The petroleum industry is a significant source of anthropogenic volatile organic compounds(VOCs),but up to now,its exact impact on urban VOCs and ozone(O_(3))remains unclear.This study conducted year-long VOC ob-servations in Dongying,China,a petroleum industrial region.The VOCs from the petroleum industry(oil and gas volatilization and petrochemical production)were identified by employing the positive matrix factorization model,and their contribution to O_(3) formation was quantitatively evaluated using an observation-based chemical box model.The observed annual average concentration of VOCs was 68.6±63.5 ppbv,with a maximum daily av-erage of 335.3 ppbv.The petroleum industry accounted for 66.5%of total VOCs,contributing 54.9%from oil and gas evaporation and 11.6%from petrochemical production.Model results indicated that VOCs from the petroleum industry contributed to 31%of net O_(3) production,with 21.3%and 34.2%contributions to HO_(2)+NO and RO_(2)+NO pathways,respectively.The larger impact on the RO_(2) pathway is primarily due to the fact that OH+VOCs ac-count for 86.9%of the primary source of RO_(2).This study highlights the critical role of controlling VOCs from the petroleum industry in urban O_(3) pollution,especially those from previously overlooked low-reactivity alkanes.展开更多
Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been...Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been clearly elucidated.Here we measured carbonyl compounds and other trace gasses together with PM_(2.5)over urban Jinan in North China Plain during the winter.Markedly higher carbonyl concentrations(average:14.63±4.21 ppbv)were found during wintertime haze pollution,about one to three-times relative to those on nonhaze days,with slight difference in chemical composition except formaldehyde(HCHO).HCHO(3.68 ppbv),acetone(3.17 ppbv),and acetaldehyde(CH_3CHO)(2.83 ppbv)were the three most abundant species,accounting for~75% of the total carbonylson both haze and non-haze days.Results from observational-based model(OBM)with atmospheric oxidation capacity(AOC)indicated that AOC significantly increased with the increasing carbonyls during the winter haze events.Carbonyl photolysis have supplied key oxidants such as RO_(2) and HO_(2),and thereby enhancing the formation of fine particles and secondary organic aerosols,elucidating the observed haze-carbonyls inter-correlation.Diurnal variation with carbonyls exhibiting peak values at early-noon and night highlighted the combined contribution of both secondary formation and primary diesel-fuel sources.1-butene was further confirmed to be the major precursor for HCHO.This study confirms the great contribution of carbonyls to AOC,and also suggests that reducing the emissions of carbonyls would be an effective way to mitigate haze pollution in urban area of the NCP region.展开更多
Regional ozone （O3） pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand ...Regional ozone （O3） pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O3 problem in the North China Plain （NCP）, intensive field measurements of O3 and related parameters were conducted at a rural site downwind of Ji＇nan, the capital city of Shandong province, in the summer of 2013. Markedly severe 03 pollution was recorded, with the 03 mixing ratios exceeding the Chinese national ambient air quality standard on 28 days （a frequency of 78%） and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O3 production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O3 accumulation, while the remainder （54%） was contributed by regional transport of the O3-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional 03 pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.展开更多
Surface ozone(O_(3))has become a critical pollutant impeding air quality improvement in many Chinese megacities.Chengdu is a megacity located in Sichuan Basin in southwest China,where O_(3)pollution occurs frequently ...Surface ozone(O_(3))has become a critical pollutant impeding air quality improvement in many Chinese megacities.Chengdu is a megacity located in Sichuan Basin in southwest China,where O_(3)pollution occurs frequently in both spring and summer.In order to understand the elevated O_(3)during spring in Chengdu,we conducted sampling campaign at three sites during O_(3)pollution episodes in April.Volatile organic compounds(VOCs)compositions at each site were similar,and oxygenated VOCs(OVOCs)concentrations accounted for the highest proportion(35%-45%),followed by alkanes,alkens(including acetylene),halohydrocarbons,and aromatics.The sensitivity of O_(3)to its precursors was analyzed using an observation based box model.The relative incremental reactivity of OVOCs was larger than other precursors,suggesting that they also played the dominant role in O_(3)formation.Furthermore,the positive matrix factorization model was used to identify the dominant emission sources and to evaluate their contribution to VOCs in the city.The main sources of VOCs in spring were from combustion(27.75%),industrial manufacturing(24.17%),vehicle exhaust(20.35%),and solvent utilization(18.35%).Discussions on VOCs and NO_(x)reduction schemes suggested that Chengdu was typical in the VOC-limited regime,and VOC emission reduction would help to prevent and control O_(3).The analysis of emission reduction scenarios based on VOCs sources showed that the emission reduction ratio of VOCs to NO_(2)needs to reach more than 3 in order to achieve O_(3)prevention.Emission reduction from vehicular exhaust source and solvent utilization source may be more effective.展开更多
Marine microbes are major drivers of marine biogeochemical cycles and play critical roles in the ecosystems. Aerobic anoxygenic phototrophic bacteria(AAPB) are an important bacterial functional group with capability o...Marine microbes are major drivers of marine biogeochemical cycles and play critical roles in the ecosystems. Aerobic anoxygenic phototrophic bacteria(AAPB) are an important bacterial functional group with capability of harvesting light energy and wide distribution, and appear to have a particular role in the ocean's carbon cycling. Yet the global pattern of AAPB distribution was controversial at the beginning of the 21 st century due to the defects of the AAPB enumeration methods. An advanced time-series observation-based infrared epifluorescence microscopy(TIREM) approach was established to amend the existing AAPB quantitative deviation and led to the accurate enumeration of AAPB in marine environments. The abundance of AAPB and AAPB% were higher in coastal and continental shelf waters than in oceanic waters, which does not support the idea that AAPB are specifically adapted to oligotrophic conditions due to photosynthesis in AAPB acting a supplement to their organic carbon respiration. Further investigation revealed that dependence of AAPB on dissolved organic carbon produced by phytoplankton(PDOC) may limit their competition and control AAPB distribution. So, the selection of carbon sources by AAPB indicated that they can effectively fractionate the carbon flow in the sea. Enlightened by these findings, the following studies on the interactions between marine microbes and DOC led to the discovery of a new mechanism of marine carbon sequestration—the Microbial Carbon Pump(MCP). The conceptual framework of MCP addresses the sources and mechanism of the vast DOC reservoir in the ocean and represents a breakthrough in the theory of ocean carbon sequestration.展开更多
基金supported by the National Key Research and Development Program of China (No. 2017YFC0210001)the National Natural Science Foundation of China (Nos. 41830106, 42022039)+1 种基金Beijing National Laboratory for Molecular Sciences (No. BNLMS-CXXM-202011)the Youth Innovation Promotion Association CAS (No. 2017042)
文摘Atmospheric oxidizing capacity(AOC)is the fundamental driving factors of chemistry process(e.g.,the formation of ozone(O_(3))and secondary organic aerosols(SOA))in the troposphere.However,accurate quantification of AOC still remains uncertainty.In this study,a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing,where O_(3) and PM_(2.5) episodes had been experienced successively.The observation-based model(OBM)is used to quantify the AOC at O_(3) and PM_(2.5) episodes.The strong intensity of AOC is found at O_(3) and PM2.5 episodes,and hydroxyl radical(OH)is the dominating daytime oxidant for both episodes.The photolysis of O_(3) is main source of OH at O_(3) episode;the photolysis of nitrous acid(HONO)and formaldehyde(HCHO)plays important role in OH formation at PM_(2.5) episode.The radicals loss routines vary according to precursor pollutants,resulting in different types of air pollution.O_(3) budgets and sensitivity analysis indicates that O_(3) production is transition regime(both VOC and NOx-limited)at O3 episode.The heterogeneous reaction of hydroperoxy radicals(HO_(2))on aerosol surfaces has significant influence on OH and O_(3) production rates.The HO_(2) uptake coefficient(γHO_(2))is the determining factor and required accurate measurement in real atmospheric environment.Our findings could provide the important bases for coordinated control of PM_(2.5) and O_(3) pollution.
基金supported by the National Key Research and Development Program of China (No. 2018YFC0209800, 2017YFC1501405)the Shanghai Science and Technology Commission of the Shanghai Municipality (No. 20ZR1447800)the National Natural Science Foundation of China (No. 41775129)
文摘Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China,in contrast to the fact that an increase in emissions of non-methane hydrocarbons(NMHCs)has been reported.This study employed seven years continuous NMHCsmeasurements and the related activities data of Shanghai,a megacity in China,to explore evolution of emissions and effectiveness of air pollution control measures.The mixing ratio of NMHCs showed no statistical interannual changes,of which their compositions exhibited marked changes.This resulted in a decreasing trend of ozone formation potential by 3.8%/year(p<0.05,the same below),which should be beneficial to ozone pollution mitigation as its production in Shanghai is in the NMHCs-limited regime.Observed alkanes,aromatics and acetylene changed by+3.7%/year,-5.9%/year and-7.4%/year,respectively,and alkenes showed no apparent trend.NMHCs sources were apportioned by a positive matrix factorization model.Accordingly,vehicular emissions(-5.9%/year)and petrochemical industry emissions(-7.1%/year)decreased significantly,but the decrease slowed down;significant reduction in solvent usage(-9.0%/year)appeared after 2010;however,emissions of natural gas(+12.6%/year)and fuel evaporation(with an increasing fraction)became more important.The inconsistency between observations and inventories was found in interannual trend and speciation as well as source contributions,emphasizing the need for further validation in NMHCs emission inventory.Our study confirms the effectiveness of measures targeting mobile and centralized emissions from industrial sources and reveals a need focusing on fugitive emissions,which provided new insights into future air policies in polluted region.
基金supported by the National Key Research and Development Program of the Ministry of Science of Technology of China(No.2022YFC3701101)the National Natural Science Foundation of China(No.42105106)+2 种基金China Postdoctoral Science Foundation(No.2021M691921)the Ministry of Ecology and Environment of the People’s Republic of China(No.DQGG202121)Dongying Ecological and Environmental Bureau(No.2021DFKY-0779).
文摘Acetaldehyde plays a significant role in atmospheric photochemical reactions and ozone formation.Previous studies have shown that acetaldehyde may rapidly be generated over short periods and impact ozone production,yet the underlyingmechanism remains unclear.To better elucidate thesemechanisms,a field campaign was conducted in Dongying,a typical petrochemical city in China.The observed acetaldehyde concentration averaged 3.0±1.6 ppbv,with a peak around 09:00 local time.The diurnal variations of acetaldehyde were categorized into two types,with Category 1 exhibiting relatively high values and increasing sharply in concentration between 07:00 and 09:00 a.m.(refer to morning peak episode,MPE),and the remaining classified as Category 2.Category 1 was similar to previous studies at heavily polluted sites but differed fromcleaner locations.Using an observation-based chemical box model,we found that acetaldehyde contributed an average of 10.2%to the net ozone production rate.Combined with a positive matrix factorizationmodel,we identified secondary formation as the dominant source of acetaldehyde(45.0%),and the daytime production rate of acetaldehyde in Category 1 was significantly higher than that in Category 2.Cis-2-butene and trans-2-butene were identified as key precursors for the rapid acetaldehyde formation during the MEP,with the petroleum industry being their primary source.Volatile organic compounds(VOCs)from petroleum industry contributed over 60%to acetaldehyde formation during the morning peak.Our findings underscore the urgent need for targeted VOCs management strategies in petroleum sector tomitigate both carbonyl and ozone formation.
基金supported by the National Research Program for Key Issues in Air Pollution Control(No.DQGG202121)the Beijing Municipal Science&Technology Commission(No.Z181100005418015)+1 种基金National Natural Science Foundation of China(No.42075094)the National Research Program for Key Issue in Air Pollution Control(No.DQGG2021101)。
文摘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.
基金funded by the National Natural Science Foundation of China[grant number 42075094]the China Postdoctoral Science Foundation[grant number 2021M691921]+1 种基金the Ministry of Ecology and Environment of the People’s Republic of China[grant number DQGG202121]the Dongying Ecological and Environmental Bureau[grant number 2021DFKY-0779]。
文摘The petroleum industry is a significant source of anthropogenic volatile organic compounds(VOCs),but up to now,its exact impact on urban VOCs and ozone(O_(3))remains unclear.This study conducted year-long VOC ob-servations in Dongying,China,a petroleum industrial region.The VOCs from the petroleum industry(oil and gas volatilization and petrochemical production)were identified by employing the positive matrix factorization model,and their contribution to O_(3) formation was quantitatively evaluated using an observation-based chemical box model.The observed annual average concentration of VOCs was 68.6±63.5 ppbv,with a maximum daily av-erage of 335.3 ppbv.The petroleum industry accounted for 66.5%of total VOCs,contributing 54.9%from oil and gas evaporation and 11.6%from petrochemical production.Model results indicated that VOCs from the petroleum industry contributed to 31%of net O_(3) production,with 21.3%and 34.2%contributions to HO_(2)+NO and RO_(2)+NO pathways,respectively.The larger impact on the RO_(2) pathway is primarily due to the fact that OH+VOCs ac-count for 86.9%of the primary source of RO_(2).This study highlights the critical role of controlling VOCs from the petroleum industry in urban O_(3) pollution,especially those from previously overlooked low-reactivity alkanes.
基金supported by the National Natural Science Foundation of China(Nos.42005092,42275127,42075112and 41775127)the Natural Science Foundation of Shandong Province(No.ZR2020QD058)。
文摘Atmospheric carbonyl compounds play significant roles in the cycling of radicals and have exhibited surprisingly high levels in winter that were well correlated to particulate matter,for which the reason have not been clearly elucidated.Here we measured carbonyl compounds and other trace gasses together with PM_(2.5)over urban Jinan in North China Plain during the winter.Markedly higher carbonyl concentrations(average:14.63±4.21 ppbv)were found during wintertime haze pollution,about one to three-times relative to those on nonhaze days,with slight difference in chemical composition except formaldehyde(HCHO).HCHO(3.68 ppbv),acetone(3.17 ppbv),and acetaldehyde(CH_3CHO)(2.83 ppbv)were the three most abundant species,accounting for~75% of the total carbonylson both haze and non-haze days.Results from observational-based model(OBM)with atmospheric oxidation capacity(AOC)indicated that AOC significantly increased with the increasing carbonyls during the winter haze events.Carbonyl photolysis have supplied key oxidants such as RO_(2) and HO_(2),and thereby enhancing the formation of fine particles and secondary organic aerosols,elucidating the observed haze-carbonyls inter-correlation.Diurnal variation with carbonyls exhibiting peak values at early-noon and night highlighted the combined contribution of both secondary formation and primary diesel-fuel sources.1-butene was further confirmed to be the major precursor for HCHO.This study confirms the great contribution of carbonyls to AOC,and also suggests that reducing the emissions of carbonyls would be an effective way to mitigate haze pollution in urban area of the NCP region.
基金funded by the Taishan Scholar Grand (No. ts20120552)the National Natural Science Foundation of China (No. 41375126)+2 种基金supported by the National Natural Science Foundation of China (No. 41675118)the Qilu Youth Talent Programme of Shandong Universitythe Jiangsu Collaborative Innovation Center for Climate Change
文摘Regional ozone （O3） pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O3 problem in the North China Plain （NCP）, intensive field measurements of O3 and related parameters were conducted at a rural site downwind of Ji＇nan, the capital city of Shandong province, in the summer of 2013. Markedly severe 03 pollution was recorded, with the 03 mixing ratios exceeding the Chinese national ambient air quality standard on 28 days （a frequency of 78%） and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O3 production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O3 accumulation, while the remainder （54%） was contributed by regional transport of the O3-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional 03 pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.
基金supported by the National Natural Science Foundation of China(No.21906108)the Fundamental Research Funds for the Central Universities(No.YJ201937)Chengdu Science and Technology Bureau(No.2020-YF09-00051-SN)
文摘Surface ozone(O_(3))has become a critical pollutant impeding air quality improvement in many Chinese megacities.Chengdu is a megacity located in Sichuan Basin in southwest China,where O_(3)pollution occurs frequently in both spring and summer.In order to understand the elevated O_(3)during spring in Chengdu,we conducted sampling campaign at three sites during O_(3)pollution episodes in April.Volatile organic compounds(VOCs)compositions at each site were similar,and oxygenated VOCs(OVOCs)concentrations accounted for the highest proportion(35%-45%),followed by alkanes,alkens(including acetylene),halohydrocarbons,and aromatics.The sensitivity of O_(3)to its precursors was analyzed using an observation based box model.The relative incremental reactivity of OVOCs was larger than other precursors,suggesting that they also played the dominant role in O_(3)formation.Furthermore,the positive matrix factorization model was used to identify the dominant emission sources and to evaluate their contribution to VOCs in the city.The main sources of VOCs in spring were from combustion(27.75%),industrial manufacturing(24.17%),vehicle exhaust(20.35%),and solvent utilization(18.35%).Discussions on VOCs and NO_(x)reduction schemes suggested that Chengdu was typical in the VOC-limited regime,and VOC emission reduction would help to prevent and control O_(3).The analysis of emission reduction scenarios based on VOCs sources showed that the emission reduction ratio of VOCs to NO_(2)needs to reach more than 3 in order to achieve O_(3)prevention.Emission reduction from vehicular exhaust source and solvent utilization source may be more effective.
基金Ministry of Science and Technology of the People’s Republic of China Project (Grant No. 2011IM010700)the National Natural Science Foundation of China (Grant Nos. 91428308, 41422603 and 41176095)the State Oceanic Administration of China Project (Grant No. GASI-03-01-02-03)
文摘Marine microbes are major drivers of marine biogeochemical cycles and play critical roles in the ecosystems. Aerobic anoxygenic phototrophic bacteria(AAPB) are an important bacterial functional group with capability of harvesting light energy and wide distribution, and appear to have a particular role in the ocean's carbon cycling. Yet the global pattern of AAPB distribution was controversial at the beginning of the 21 st century due to the defects of the AAPB enumeration methods. An advanced time-series observation-based infrared epifluorescence microscopy(TIREM) approach was established to amend the existing AAPB quantitative deviation and led to the accurate enumeration of AAPB in marine environments. The abundance of AAPB and AAPB% were higher in coastal and continental shelf waters than in oceanic waters, which does not support the idea that AAPB are specifically adapted to oligotrophic conditions due to photosynthesis in AAPB acting a supplement to their organic carbon respiration. Further investigation revealed that dependence of AAPB on dissolved organic carbon produced by phytoplankton(PDOC) may limit their competition and control AAPB distribution. So, the selection of carbon sources by AAPB indicated that they can effectively fractionate the carbon flow in the sea. Enlightened by these findings, the following studies on the interactions between marine microbes and DOC led to the discovery of a new mechanism of marine carbon sequestration—the Microbial Carbon Pump(MCP). The conceptual framework of MCP addresses the sources and mechanism of the vast DOC reservoir in the ocean and represents a breakthrough in the theory of ocean carbon sequestration.
