Photodegradation technology has been widely applied in the purification of industrial aromatic hydrocarbons.However,whether this technology efficiently removes the pollutants to prevent secondary pollution and health ...Photodegradation technology has been widely applied in the purification of industrial aromatic hydrocarbons.However,whether this technology efficiently removes the pollutants to prevent secondary pollution and health risk is still unclear.Here,the photodegradation processes of three xylenes were compared under designed reaction atmospheres and light sources.Xe lamp showed poor photodegradation ability toward xylenes,no matter in N_(2) or N_(2)+O_(2)system,while much higher photodegradation performance of xylenes were obtained under ultraviolet(UV)and vacuum ultraviolet(VUV)irradiation,especially in N_(2)+O_(2)+VUV system,where 97.9%of m-xylene,99.0%of o-xylene or 87.5%of p-xylene with the initial concentration of 860 mg/m^(3) was removed within 240 min.The xylenes underwent three processes of photo-isomerization,photodecomposition and photo-oxidation to produce intermediates of aromatics,alkanes and carbonyls.Among them,the photo-isomerization products showed the highest concentration percentage(e.g.,≥50%in o-xylene system),confirming that photo-isomerization reaction was the dominated photodegradation process of xylenes.Moreover,these isomerized products not only contributed about 97%and91%to the formation potential of O3(OFP)and secondary organic aerosols(SOAFP),but also displayed obvious non-carcinogenic risk,although one of photodecomposition product—benzene showed the highest occupational exposure risk.Therefore,the secondary pollution and health risks of photodegradation products of xylenes were non-ignorable,although the OFP,SOAFP and health risks of the generated products reduced at least 4.5 times in comparison with that of the degraded xylenes.The findings are helpful for the appropriate application of this technology in the purification of industrial organic waste gas.展开更多
The formation and aging mechanism of secondary organic aerosol(SOA)and its influencing factors have attracted increasing attention in recent years because of their effects on climate change,atmospheric quality and hum...The formation and aging mechanism of secondary organic aerosol(SOA)and its influencing factors have attracted increasing attention in recent years because of their effects on climate change,atmospheric quality and human health.However,there are still large errors between air quality model simulation results and field observations.The currently undetected components during the formation and aging of SOA due to the limitation of current monitoring techniques and the interactions among multiple SOA formation influencing factors might be the main reasons for the differences.In this paper,we present a detailed review of the complex dynamic physical and chemical processes and the corresponding influencing factors involved in SOA formation and aging.And all these results were mainly based the studies of photochemical smog chamber simulation.Although the properties of precursor volatile organic compounds(VOCs),oxidants(such as OH radicals),and atmospheric environmental factors(such as NOx,SO2,NH3,light intensity,temperature,humidity and seed aerosols)jointly influence the products and yield of SOA,the nucleation and vapor pressure of these products were found to be the most fundamental aspects when interpreting the dynamics of the SOA formation and aging process.The development of techniques for measuring intermediate species in SOA generation processes and the study of SOA generation and aging mechanism in complex systems should be important topics of future SOA research.展开更多
To evaluate the potential benefits of biomass use for air pollution control, this paper identified and quantified the emissions of major reactive organic compounds anticipated from biomass-fired industrial boilers. Wo...To evaluate the potential benefits of biomass use for air pollution control, this paper identified and quantified the emissions of major reactive organic compounds anticipated from biomass-fired industrial boilers. Wood pellets(WP) and straw pellets(SP) were burned to determine the volatile organic compound emission profiles for each biomass-boiler combination. More than 100 types of volatile organic compounds(VOCs) were measured from the two biomass boilers. The measured VOC species included alkanes, alkenes and acetylenes, aromatics, halocarbons and carbonyls. A single coal-fired boiler(CB) was also studied to provide a basis for comparison. Biomass boiler 1(BB1) emitted relatively high proportions of alkanes(28.9%–38.1% by mass) and alkenes and acetylenes(23.4%–40.8%),while biomass boiler 2(BB2) emitted relatively high proportions of aromatics(27.9%–29.2%)and oxygenated VOCs(33.0%–44.8%). The total VOC(TVOC) emission factors from BB1(128.59–146.16 mg/kg) were higher than those from BB2(41.26–85.29 mg/kg). The total ozone formation potential(OFP) ranged from 6.26 to 81.75 mg/m^3 with an average of 33.66 mg/m^3 for the two biomass boilers. The total secondary organic aerosol potential(SOAP) ranged from 61.56 to 211.67 mg/m^3 with an average of 142.27 mg/m^3 for the two biomass boilers.The emission factors(EFs) of TVOCs from biomass boilers in this study were similar to those for industrial coal-fired boilers with the same thermal power. These data can supplement existing VOC emission factors for biomass combustion and thus enrich the VOC emission inventory.展开更多
Volatile organic compounds(VOCs)are the important precursors of the tropospheric ozone(O3)and secondary organic aerosols(SOA),both of which are known to harm human health and disrupt the earth’s climate system.In thi...Volatile organic compounds(VOCs)are the important precursors of the tropospheric ozone(O3)and secondary organic aerosols(SOA),both of which are known to harm human health and disrupt the earth’s climate system.In this study,VOC emission factors,O3 and SOA formation potentials were estimated for two types of industrial boilers:coal-fired boilers(n=3)and oil-fired boilers(n=3).Results showed that EVOCs concentrations were more than nine times higher for oil-fire d boilers compared to those for coal-fired boilers.Emission factors ofΣVOCs were found to be higher for oil-fired boilers(9.26-32.83 mg-VOC/kg)than for coal-fired boilers(1.57-4.13 mg-VOC/kg).Alkanes and aromatics were obtained as the most abundant groups in coal-fired boilers,while oxygenated organics and aromatics were the most contributing groups in oil-fired boilers.Benzene,n-hexane and o-ethyl toluene were the abundant VOC species in coal-fired boiler emissions,whereas toluene was the most abundant VOC species emitted from oil-fired boilers.O3 and SOA formation potentials were found 12 and 18 times,respectively,higher for oil-fired than for coal-fired boilers.Total OFP ranged from 3.99 to 11.39 mg-O3/kg for coal-fired boilers.For oil-fired boilers,total OFP ranged from 36.16 to 131.93 mg-O3/kg.Moreover,total secondary organic aerosol potential(SOAP)ranged from 65.4 to 122.5 mg-SOA/kg and 779.9 to 2252.5 mg-SOA/kg for the coal-fired and oil-fired boilers,respectively.展开更多
Herein,we use an oxidation flow reactor,Gothenburg:Potential Aerosol Mass(Go:PAM)reactor,to investigate the secondary organic aerosol(SOA)formation from wheat straw burning.Biomass burning emissions are exposed to hig...Herein,we use an oxidation flow reactor,Gothenburg:Potential Aerosol Mass(Go:PAM)reactor,to investigate the secondary organic aerosol(SOA)formation from wheat straw burning.Biomass burning emissions are exposed to high concentrations of hydroxyl radicals(OH)to simulate processes equivalent to atmospheric oxidation of 0-2.55 days.Primary volatile organic compounds(VOCs)were investigated,and particles were measured before and after the Go:PAM reactor.The influence of water content(i.e.5%and 11%)in wheat straw was also explored.Two burning stages,the flaming stage,and non-flaming stages,were identified.Primary particle emission factors(EFs)at a water content of 11%(~3.89 g/kg-fuel)are significantly higher than those at a water content of 5%(~2.26 g/kg-fuel)during the flaming stage.However,the water content showed no significant influence at the non-flaming stage.EFs of aromatics at a non-flaming stage(321.8±46.2 mg/kg-fuel)are larger than that at a flaming stage(130.9±37.1 mg/kg-fuel).The OA enhancement ratios increased with the increase in OH exposure at first and decreased with the additional increment of OH exposure.The maximum OA enhancement ratio is~12 during the non-flaming stages,which is much higher than~1.7 during the flaming stages.The mass spectrum of the primary wheat burning organic aerosols closely resembles that of resolved biomass burning organic aerosols(BBOA)based on measurements in ambient air.Our results show that large gap(0%-90%)still remains to estimate biomass burning SOA if only the oxidation of VOCs were included.展开更多
The atmospheric chemistry in complex air pollution remains poorly understood.In order to probe how environmental conditions can impact the secondary organic aerosol(SOA)formation from biomass burning emissions,we inve...The atmospheric chemistry in complex air pollution remains poorly understood.In order to probe how environmental conditions can impact the secondary organic aerosol(SOA)formation from biomass burning emissions,we investigated the photooxidation of 2,5-dimethylfuran(DMF)under different environmental conditions in a smog chamber.It was found that SO_(2)could promote the formation of SOA and increase the amounts of inorganic salts produced during the photooxidation.The formation rate of SOA and the corresponding SOA mass concentration increased gradually with the increasing DMF/OH ratio.The addition of(NH_(4))_(2)SO_(4)seed aerosol accelerated the SOA formation rate and significantly shortened the time for the reaction to reach equilibrium.Additionally,a relatively high illumination intensity promoted the formation of OH radicals and,correspondingly,enhanced the photooxidation of DMF.However,the enhancement of light intensity accelerated the aging of SOA,which led to a gradual decrease of the SOA mass concentration.This work shows that by having varying influence on atmospheric chemical reactions,the same environmental factor can affect SOA formation in different ways.The present study is helpful for us to better understand atmospheric complex pollution.展开更多
Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aeroso...Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol（SOA） production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.展开更多
基金supported by the National Natural Science Foundation of China (Nos.42177354 and 21777032)the National Key R&D Program of China (No.2019YFC0214402)the Guangdong Basic and Applied Basic Research oundation (No.2019B151502064)。
文摘Photodegradation technology has been widely applied in the purification of industrial aromatic hydrocarbons.However,whether this technology efficiently removes the pollutants to prevent secondary pollution and health risk is still unclear.Here,the photodegradation processes of three xylenes were compared under designed reaction atmospheres and light sources.Xe lamp showed poor photodegradation ability toward xylenes,no matter in N_(2) or N_(2)+O_(2)system,while much higher photodegradation performance of xylenes were obtained under ultraviolet(UV)and vacuum ultraviolet(VUV)irradiation,especially in N_(2)+O_(2)+VUV system,where 97.9%of m-xylene,99.0%of o-xylene or 87.5%of p-xylene with the initial concentration of 860 mg/m^(3) was removed within 240 min.The xylenes underwent three processes of photo-isomerization,photodecomposition and photo-oxidation to produce intermediates of aromatics,alkanes and carbonyls.Among them,the photo-isomerization products showed the highest concentration percentage(e.g.,≥50%in o-xylene system),confirming that photo-isomerization reaction was the dominated photodegradation process of xylenes.Moreover,these isomerized products not only contributed about 97%and91%to the formation potential of O3(OFP)and secondary organic aerosols(SOAFP),but also displayed obvious non-carcinogenic risk,although one of photodecomposition product—benzene showed the highest occupational exposure risk.Therefore,the secondary pollution and health risks of photodegradation products of xylenes were non-ignorable,although the OFP,SOAFP and health risks of the generated products reduced at least 4.5 times in comparison with that of the degraded xylenes.The findings are helpful for the appropriate application of this technology in the purification of industrial organic waste gas.
基金supported by the Central Level,Scientific Research Institutes for Basic R&D Special Fund Business,China(No.2021-JY-16)the National Natural Science Foundation of China(Nos.42075182 and 2130721)+1 种基金the National Research Program for Key Issue in Air Pollution Control(No.DQGG2021101)the National Key Research and Development Program of China(No.2019YFC0214800)。
文摘The formation and aging mechanism of secondary organic aerosol(SOA)and its influencing factors have attracted increasing attention in recent years because of their effects on climate change,atmospheric quality and human health.However,there are still large errors between air quality model simulation results and field observations.The currently undetected components during the formation and aging of SOA due to the limitation of current monitoring techniques and the interactions among multiple SOA formation influencing factors might be the main reasons for the differences.In this paper,we present a detailed review of the complex dynamic physical and chemical processes and the corresponding influencing factors involved in SOA formation and aging.And all these results were mainly based the studies of photochemical smog chamber simulation.Although the properties of precursor volatile organic compounds(VOCs),oxidants(such as OH radicals),and atmospheric environmental factors(such as NOx,SO2,NH3,light intensity,temperature,humidity and seed aerosols)jointly influence the products and yield of SOA,the nucleation and vapor pressure of these products were found to be the most fundamental aspects when interpreting the dynamics of the SOA formation and aging process.The development of techniques for measuring intermediate species in SOA generation processes and the study of SOA generation and aging mechanism in complex systems should be important topics of future SOA research.
基金supported by the National Natural Science Foundation of China(No.41275135)the Chinese National Key Research and Development Plan(No.2017YFC0212503)
文摘To evaluate the potential benefits of biomass use for air pollution control, this paper identified and quantified the emissions of major reactive organic compounds anticipated from biomass-fired industrial boilers. Wood pellets(WP) and straw pellets(SP) were burned to determine the volatile organic compound emission profiles for each biomass-boiler combination. More than 100 types of volatile organic compounds(VOCs) were measured from the two biomass boilers. The measured VOC species included alkanes, alkenes and acetylenes, aromatics, halocarbons and carbonyls. A single coal-fired boiler(CB) was also studied to provide a basis for comparison. Biomass boiler 1(BB1) emitted relatively high proportions of alkanes(28.9%–38.1% by mass) and alkenes and acetylenes(23.4%–40.8%),while biomass boiler 2(BB2) emitted relatively high proportions of aromatics(27.9%–29.2%)and oxygenated VOCs(33.0%–44.8%). The total VOC(TVOC) emission factors from BB1(128.59–146.16 mg/kg) were higher than those from BB2(41.26–85.29 mg/kg). The total ozone formation potential(OFP) ranged from 6.26 to 81.75 mg/m^3 with an average of 33.66 mg/m^3 for the two biomass boilers. The total secondary organic aerosol potential(SOAP) ranged from 61.56 to 211.67 mg/m^3 with an average of 142.27 mg/m^3 for the two biomass boilers.The emission factors(EFs) of TVOCs from biomass boilers in this study were similar to those for industrial coal-fired boilers with the same thermal power. These data can supplement existing VOC emission factors for biomass combustion and thus enrich the VOC emission inventory.
文摘Volatile organic compounds(VOCs)are the important precursors of the tropospheric ozone(O3)and secondary organic aerosols(SOA),both of which are known to harm human health and disrupt the earth’s climate system.In this study,VOC emission factors,O3 and SOA formation potentials were estimated for two types of industrial boilers:coal-fired boilers(n=3)and oil-fired boilers(n=3).Results showed that EVOCs concentrations were more than nine times higher for oil-fire d boilers compared to those for coal-fired boilers.Emission factors ofΣVOCs were found to be higher for oil-fired boilers(9.26-32.83 mg-VOC/kg)than for coal-fired boilers(1.57-4.13 mg-VOC/kg).Alkanes and aromatics were obtained as the most abundant groups in coal-fired boilers,while oxygenated organics and aromatics were the most contributing groups in oil-fired boilers.Benzene,n-hexane and o-ethyl toluene were the abundant VOC species in coal-fired boiler emissions,whereas toluene was the most abundant VOC species emitted from oil-fired boilers.O3 and SOA formation potentials were found 12 and 18 times,respectively,higher for oil-fired than for coal-fired boilers.Total OFP ranged from 3.99 to 11.39 mg-O3/kg for coal-fired boilers.For oil-fired boilers,total OFP ranged from 36.16 to 131.93 mg-O3/kg.Moreover,total secondary organic aerosol potential(SOAP)ranged from 65.4 to 122.5 mg-SOA/kg and 779.9 to 2252.5 mg-SOA/kg for the coal-fired and oil-fired boilers,respectively.
基金supported by National Natural Science Foundation of China(Nos.51636003,91844301,41977179)Beijing Municipal Science and Technology Commission(No.Z201100008220011)+2 种基金Natural Science Foundation of Beijing(No.8192022)China Postdoctoral Science Foundation(No.2020M680242)the Open Research Fund of State Key Laboratory of Multi-phase Complex Systems(No.MPCS-2021-D-12)
文摘Herein,we use an oxidation flow reactor,Gothenburg:Potential Aerosol Mass(Go:PAM)reactor,to investigate the secondary organic aerosol(SOA)formation from wheat straw burning.Biomass burning emissions are exposed to high concentrations of hydroxyl radicals(OH)to simulate processes equivalent to atmospheric oxidation of 0-2.55 days.Primary volatile organic compounds(VOCs)were investigated,and particles were measured before and after the Go:PAM reactor.The influence of water content(i.e.5%and 11%)in wheat straw was also explored.Two burning stages,the flaming stage,and non-flaming stages,were identified.Primary particle emission factors(EFs)at a water content of 11%(~3.89 g/kg-fuel)are significantly higher than those at a water content of 5%(~2.26 g/kg-fuel)during the flaming stage.However,the water content showed no significant influence at the non-flaming stage.EFs of aromatics at a non-flaming stage(321.8±46.2 mg/kg-fuel)are larger than that at a flaming stage(130.9±37.1 mg/kg-fuel).The OA enhancement ratios increased with the increase in OH exposure at first and decreased with the additional increment of OH exposure.The maximum OA enhancement ratio is~12 during the non-flaming stages,which is much higher than~1.7 during the flaming stages.The mass spectrum of the primary wheat burning organic aerosols closely resembles that of resolved biomass burning organic aerosols(BBOA)based on measurements in ambient air.Our results show that large gap(0%-90%)still remains to estimate biomass burning SOA if only the oxidation of VOCs were included.
基金supported by National Natural Science Foundation of China(No.91644214)Youth Innovation Program of Universities in Shandong Province(No.2019KJD007)Fundamental Research Fund of Shandong University(No.2020QNQT012)
文摘The atmospheric chemistry in complex air pollution remains poorly understood.In order to probe how environmental conditions can impact the secondary organic aerosol(SOA)formation from biomass burning emissions,we investigated the photooxidation of 2,5-dimethylfuran(DMF)under different environmental conditions in a smog chamber.It was found that SO_(2)could promote the formation of SOA and increase the amounts of inorganic salts produced during the photooxidation.The formation rate of SOA and the corresponding SOA mass concentration increased gradually with the increasing DMF/OH ratio.The addition of(NH_(4))_(2)SO_(4)seed aerosol accelerated the SOA formation rate and significantly shortened the time for the reaction to reach equilibrium.Additionally,a relatively high illumination intensity promoted the formation of OH radicals and,correspondingly,enhanced the photooxidation of DMF.However,the enhancement of light intensity accelerated the aging of SOA,which led to a gradual decrease of the SOA mass concentration.This work shows that by having varying influence on atmospheric chemical reactions,the same environmental factor can affect SOA formation in different ways.The present study is helpful for us to better understand atmospheric complex pollution.
基金supported by the National Key Basic Research and Development Program (No. 2013CB228500)the National Basic Research Program (973) of China (Nos. 2013CB228503, 2013CB228502)+3 种基金National Natural Science Foundation of China (Nos. 91544214, 51636003)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB05010500)China Postdoctoral Science Foundation (No. 2015M580929)the State Key Lab of Automotive Safety and Energy at Tsinghua University for their support for the experiments
文摘Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol（SOA） production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.
