Particulate levoglucosan is an important tracer for biomass burning emission in ambient air.However,recent studies question its reliability as a biomass burning tracer in Chinesemega cities due to important contributi...Particulate levoglucosan is an important tracer for biomass burning emission in ambient air.However,recent studies question its reliability as a biomass burning tracer in Chinesemega cities due to important contribution from potential non-biomass burning sources,such as cooking.To address this,we examined the dynamic variation and sources of levoglucosan using a chemical ionization mass spectrometer and other advanced instruments during Beijing’s summer of 2021.The average mass concentration of levoglucosan and its isomer(C_(6)H_(10)O_(5))was 0.025±0.014μg/m^(3),constituting 0.55%±0.32%of total organic carbon(OC)in this campaign.Despite cooking emissions contributing significantly to the organic aerosol(OA,20%),levoglucosan and its isomers correlated more strongly with biomass-burning related tracers(R>0.6),black carbon(R=0.72)and less so with cooking-related sources(R=0.3).This indicates that levoglucosan is primarily dominated by biomass-burning emissions rather than cooking in Beijing’s urban areas during summertime.The diurnal variation of levoglucosan concentrations highlighted the importance of daytime and nocturnal biomass burning emissions during polluted periods in Beijing.Using levoglucosan as a tracer to quantify the biomass burning OC(BBOC),we found good agreement on the time series of BBOC between the tracermethod and other independent source apportionmentmethod.This reaffirms the reliability of levoglucosan as a biomass burning tracer.Biomass burning contributed an average of 7%-8%to OC,highlighting its significant impact on Beijing’s summer air quality.Our study enhances understanding of biomass burning influences on ambient aerosol in typical urban areas.展开更多
In order to better understand the pyrolysis process of cellulose, the decomposition of levoglucosan and glyceraldehyde, which are important intermediate products of cellulose, are simulated by quantum simulation. Ther...In order to better understand the pyrolysis process of cellulose, the decomposition of levoglucosan and glyceraldehyde, which are important intermediate products of cellulose, are simulated by quantum simulation. Thermodynamic analysis of four possible reaction pathways for levoglucosan is conducted by quantum chemistry.The reaction process of glyceraldehyde is checked, and the intermediates and the activation energies of the process are given. The simulation results indicate that the three well-established chemical pathways for levoglucosan in literature can spontaneously occur within the pyrolysis temperature range from 500 to 1 000 K. However, the reaction pathway involving the formation of erythrose cannot be accepted since the free energy ΔG is estimated to be above zero during the pyrolysis process. Through the analysis of glyceraldehyde decomposition by the transition state theory, decarbonylation and dehydration may be the dominant pathways for glyceraldehyde decomposition. The quantum simulation for determining the chemical pathway of glyceraldehyde and levoglucosan can give a conceptual and methodological guide for searching possible chemical pathways of cellulose pyrolysis or other macromolecules in biomass.展开更多
Expanding urbanization and agricultural intensification across neighboring South Asia and East Asia have substantially threatened atmospheric condition over the Third Pole(TP)during the past few decades.Whether the at...Expanding urbanization and agricultural intensification across neighboring South Asia and East Asia have substantially threatened atmospheric condition over the Third Pole(TP)during the past few decades.Whether the atmospheric condition over the TP is still as clean as a representative of the regional background draws great concern.In this work,great differences in levoglucosan concentration within/above the atmospheric boundary layer height are revealed.Levoglucosan results support the hypothesis that atmospheric pollutants in the mid-troposphere over the TP are mainly affected by long-range transport,although there are some local biomass burning emissions in residential areas.In addition,levoglucosan concentration in the midtroposphere over the TP is at the same magnitude as marine and polar regions,but about 2–3 magnitudes lower than neighboring densely-populated Asian regions.With insights of levoglucosan records,this work therefore proves that the high-altitude TP still has largely pristine atmospheric conditions,and is one of the cleanest remote regions on the Earth.展开更多
To address the pressing global need for carbon-neutral fuels,optimizing the conversion of biomass to biooil(bio-chemicals)is crucial.Here,we introduce MXene(Ti_(3)C_(2)T_(x))as an innovative catalyst in biomass pyroly...To address the pressing global need for carbon-neutral fuels,optimizing the conversion of biomass to biooil(bio-chemicals)is crucial.Here,we introduce MXene(Ti_(3)C_(2)T_(x))as an innovative catalyst in biomass pyrolysis,exhibiting significant prowess in boosting levoglucosan yields.Py-GC/MS analysis indicated a remarkable 438%enhancement in levoglucosan yield when a 5 wt%catalyst-to-biomass ratio was employed.Laboratory-scale studies achieved an impressive 13.95 wt%levoglucosan in ex-situ fixed-bed catalytic pyrolysis,a yield that is 19.6 times higher than that from pure biomass at 40 wt%catalyst loading.Recycling evaluations affirm the robust stability of the MXene catalyst,validating its potential for multiple use cycles in eco-friendly industrial levoglucosan production.展开更多
The environmental significance of levoglucosan(LEV) records in Tibetan glacier ice layers on sub-annual to annual scales, in particular their suitability as a specific biomarker for indicating past fire changes, is po...The environmental significance of levoglucosan(LEV) records in Tibetan glacier ice layers on sub-annual to annual scales, in particular their suitability as a specific biomarker for indicating past fire changes, is poorly understood at present. In this work, a continuous LEV record was reconstructed in a central Tibetan ice core for the period 1990–2012. The LEV record was classified into two categories based on its LEV concentrations: background levels and extreme events. Annually-resolved LEV records and background levels in the ice core were strongly correlated with satellite observations of fire occurrence frequency over the northern Indian peninsula between 2003 and 2012, especially for strong fire events during the pre-monsoon season(March–May). In addition, peaks in LEV concentrations may represent extreme fire events in regions around the Tibetan Plateau. LEV records in the ice core reflect a longterm increasing trend in fire background and also an increase in fire extreme events, across the Tibetan Plateau and its surroundings. We therefore conclude that LEV records in Tibetan ice cores can be used as a powerful tool for calibrating and reconstructing past fire changes over subtropical Asia.展开更多
The largest sugarcane-growing area in the United States is in South Florida. An estimated 7 million tons of dry sugarcane leafy biomass is removed from the fields before harvest by burning the leaves off the sugarcane...The largest sugarcane-growing area in the United States is in South Florida. An estimated 7 million tons of dry sugarcane leafy biomass is removed from the fields before harvest by burning the leaves off the sugarcane stalks. Preharvest sugarcane leaf foliage burning is a major source of airborne particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), biogenic trace elements such as K, volatile hydrocarbons and other pollutants. In one harvesting period, approximately 22 million tons of C02, a greenhouse gas, is released, 7 million tons from leaf foliage preharvest burning alone and 15 million tons from burning sugarcane bagasse in the sugar mills for power generation. In this study, PMio was collected from Belle Glade, close to the sugarcane-growing area, and from Delray Beach, an urbanized area along the East Coast of Florida. The PM samples were analyzed for trace elements and close to organic compounds. To elucidate the importance of preharvest sugarcane biomass smoke emissions on air quality, 39 trace elements, 18 PAHs, and levoglucosan were selected to apportion ambient PM constituents. Al, Ca and to a great extend also Mg are the major soil-related trace elements and key markers for fugitive soil dust emissions. Similarly, sea salt aerosol blown from the Atlantic Ocean into Florida added appreciably to PMio trace elements concentration, especially Na and Cl. Approximately half of the sea salt aerosol (PMjo -portion) by mass is removed from the atmosphere during the transport of ocean air from Delray Beach to Belle Glade. Ambient acid displacement reactions caused a substantial portion of the Cl (30%) to be liberated from the sea salt aerosol to the atmosphere during transport as gaseous HC1. The PAH concentrations at Belle Glade were high when the biomass combustion markers levoglucosan and I< also showed the highest concentrations. This indicates that during the sugarcane harvest season, when leaf foliage is burned off just before harvest, most of the ambient PAHs associated with PMio are indeed related to preharvest burning, harvesting machinery emissions, bagasse burning in sugarcane mills, and other related activities that consume biomass and/or fossil fuels for sugarcane harvesting and processing.展开更多
Pretreatment of lignocellulosic biomass is crucial for the release of biofermentable sugars for biofuels production,which could greatly alleviate the burgeoning environment and energy crisis caused by the massive usag...Pretreatment of lignocellulosic biomass is crucial for the release of biofermentable sugars for biofuels production,which could greatly alleviate the burgeoning environment and energy crisis caused by the massive usage of traditional fossil fuels.Pyrolysis is a cost-saving pretreatment process that can readily decompose biomass into levoglucosan,a promising anhydrosugar;however,many undesired toxic compounds inhibitory to downstream microbial fermentation are also generated during the pyrolysis,immensely impeding the bioconversion of levoglucosan-containing pyrolysate.Here,we took the first insight into the proteomic responses of a levoglucosan-utilizing and ethanol-producing Escherichia coli to three representative biomass-derived inhibitors,identifying large amounts of differentially expressed proteins(DEPs)that could guide the downstream metabolic engineering for the development of inhibitor-resistant strains.Fifteen up-and eight down-regulated DEPs were further identified as the biomarker stress-responsive proteins candidate for cellular tolerance to multiple inhibitors.Among these biomarker proteins,YcfR exhibiting the highest expression fold-change level was chosen as the target of overexpression to validate proteomics results and develop robust strains with enhanced inhibitor tolerance and fermentation performance.Finally,based on four plasmid-borne genes encoding the levoglucosan kinase,pyruvate decarboxylase,alcohol dehydrogenase,and protein YcfR,a new recombinant strain E.coli LGE-ycfR was successfully created,showing much higher acetic acid-,furfural-,and phenol-tolerance levels compared to the control without overexpression of ycfR.The specific growth rate,final cell density,ethanol concentration,ethanol productivity,and levoglucosan consumption rate of the recombinant were also remarkably improved.From the proteomics-guided metabolic engineering and phenotypic observations,we for the first time corroborated that YcfR is a stress-induced protein responsive to multiple biomass-derived inhibitors,and also developed an inhibitors-resistant strain that could produce bioethanol from levoglucosan in the presence of inhibitors of relatively high concentration.The newly developed E.coli LGE-ycfR strain that could eliminate the commonly-used costly detoxicification processes,is of great potential for the in situ cost-effective bioethanol production from the biomass-derived pyrolytic substrates.展开更多
Polyethylene terephthalate(PET)combustion produces terephthalic acid(TPA),a key indicator of incineration processes.This study examines the diurnal variation of TPA and its association with health risks in Seoul,South...Polyethylene terephthalate(PET)combustion produces terephthalic acid(TPA),a key indicator of incineration processes.This study examines the diurnal variation of TPA and its association with health risks in Seoul,South Korea,based on data from Bokjeong Station.TPA concentrations were significantly higher in winter(28.12 ng/m^(3))compared to summer(12.39 ng/m^(3)),indicating increased PET-related emissions during colder months.Similarly,levoglucosan concentrations were markedly higher in winter(68.17 ng/m^(3))than in summer(16.67 ng/m^(3)),likely due to waste wood incineration.The TPA-to-organic carbon(TPA/OC)ratio was notably higher at night,suggesting more frequent PET waste combustion during nighttime hours.Elevated nighttime TPA concentrations in PM_(2.5)also indicate contributions from coal combustion or the incineration of arsenic-containing materials.The correlation between TPA and oxidative potential underscores heightened health risks associated with nighttime emissions.Moreover,volatile organic compounds(VOCs)such as benzene,toluene,and xylene were significantly higher at night,further degrading air quality.These findings highlight the critical role of nighttime waste incineration in exacerbating urban air pollution and increasing associated health risks,especially during winter.展开更多
Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic ...Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic carbon(OC),daily fine particulate matter(PM_(2.5))samples were collected from March to May 2022 in Pu'er,Southwest China.The concentrations of OC,elemental carbon(EC),levoglucosan(Lev),and potassium from BB(K+BB)during the study period ranged from 5.3 to 31.2μg/m^(3),0.86-13.1μg/m^(3),0.06-0.82μg/m^(3),and 0.05-2.88μg/m^(3),respectively.To eliminate the effects of Lev degradation,this study uses the Aging of Air Mass(AAM)index to correct the atmospheric concentration of Lev and combines Bayesian mixture modeling with a molecular tracer method to assess the original contribution of BB to OC.The results indicated that the AAM index was 0.18±0.05,indicating that the degradation of Lev reached 82%.When considering the degradation of levoglucosan in the atmosphere,the primary source of BB aerosols was crop-straw combustion(71.1%),followed by the combustion of certain hardwoods and softwoods(24.9%)and grasses(4.0%).The original contribution of BB to OC was 62.4%,which was much greater than the contribution when levoglucosan degradation(23.7%)was ignored.The air mass inverse trajectories and Moderate Resolution Imaging Spectroradiometer(MODIS)fire hotspots indicated that the BB plume from Southeast Asia during spring could influence PM_(2.5)long-range transport in remote locations,and the contribution could reach 82%in Southwest China.展开更多
基金supported by the National Key R&D Program of China(Nos.2022YFC3701000 and 2021YFA1601800)the National Natural Science Foundation of China(Nos.42230701 and 42375105)+1 种基金the Foundation for Program of Science and Technology Research(No.2024A1515011937)Guangdong Foundation for Program of Science and Technology Research(No.2023B1212060049).
文摘Particulate levoglucosan is an important tracer for biomass burning emission in ambient air.However,recent studies question its reliability as a biomass burning tracer in Chinesemega cities due to important contribution from potential non-biomass burning sources,such as cooking.To address this,we examined the dynamic variation and sources of levoglucosan using a chemical ionization mass spectrometer and other advanced instruments during Beijing’s summer of 2021.The average mass concentration of levoglucosan and its isomer(C_(6)H_(10)O_(5))was 0.025±0.014μg/m^(3),constituting 0.55%±0.32%of total organic carbon(OC)in this campaign.Despite cooking emissions contributing significantly to the organic aerosol(OA,20%),levoglucosan and its isomers correlated more strongly with biomass-burning related tracers(R>0.6),black carbon(R=0.72)and less so with cooking-related sources(R=0.3).This indicates that levoglucosan is primarily dominated by biomass-burning emissions rather than cooking in Beijing’s urban areas during summertime.The diurnal variation of levoglucosan concentrations highlighted the importance of daytime and nocturnal biomass burning emissions during polluted periods in Beijing.Using levoglucosan as a tracer to quantify the biomass burning OC(BBOC),we found good agreement on the time series of BBOC between the tracermethod and other independent source apportionmentmethod.This reaffirms the reliability of levoglucosan as a biomass burning tracer.Biomass burning contributed an average of 7%-8%to OC,highlighting its significant impact on Beijing’s summer air quality.Our study enhances understanding of biomass burning influences on ambient aerosol in typical urban areas.
基金The National High Technology Research and Development Program of China(863 Program)(No.2012AA051801)
文摘In order to better understand the pyrolysis process of cellulose, the decomposition of levoglucosan and glyceraldehyde, which are important intermediate products of cellulose, are simulated by quantum simulation. Thermodynamic analysis of four possible reaction pathways for levoglucosan is conducted by quantum chemistry.The reaction process of glyceraldehyde is checked, and the intermediates and the activation energies of the process are given. The simulation results indicate that the three well-established chemical pathways for levoglucosan in literature can spontaneously occur within the pyrolysis temperature range from 500 to 1 000 K. However, the reaction pathway involving the formation of erythrose cannot be accepted since the free energy ΔG is estimated to be above zero during the pyrolysis process. Through the analysis of glyceraldehyde decomposition by the transition state theory, decarbonylation and dehydration may be the dominant pathways for glyceraldehyde decomposition. The quantum simulation for determining the chemical pathway of glyceraldehyde and levoglucosan can give a conceptual and methodological guide for searching possible chemical pathways of cellulose pyrolysis or other macromolecules in biomass.
基金the Youth Innovation Promotion Association CAS(2020071)Chinese Academy of Sciences(YIPA-2020071,XDA20060200)+1 种基金the National Natural Science Foundation of China(41701078,41805127)the Second Tibetan Plateau Scientific Expedition and Research(2019QZKK0201).
文摘Expanding urbanization and agricultural intensification across neighboring South Asia and East Asia have substantially threatened atmospheric condition over the Third Pole(TP)during the past few decades.Whether the atmospheric condition over the TP is still as clean as a representative of the regional background draws great concern.In this work,great differences in levoglucosan concentration within/above the atmospheric boundary layer height are revealed.Levoglucosan results support the hypothesis that atmospheric pollutants in the mid-troposphere over the TP are mainly affected by long-range transport,although there are some local biomass burning emissions in residential areas.In addition,levoglucosan concentration in the midtroposphere over the TP is at the same magnitude as marine and polar regions,but about 2–3 magnitudes lower than neighboring densely-populated Asian regions.With insights of levoglucosan records,this work therefore proves that the high-altitude TP still has largely pristine atmospheric conditions,and is one of the cleanest remote regions on the Earth.
基金financial support provided by the National Natural Science Foundation of China(Nos.22108221 and 52203145)。
文摘To address the pressing global need for carbon-neutral fuels,optimizing the conversion of biomass to biooil(bio-chemicals)is crucial.Here,we introduce MXene(Ti_(3)C_(2)T_(x))as an innovative catalyst in biomass pyrolysis,exhibiting significant prowess in boosting levoglucosan yields.Py-GC/MS analysis indicated a remarkable 438%enhancement in levoglucosan yield when a 5 wt%catalyst-to-biomass ratio was employed.Laboratory-scale studies achieved an impressive 13.95 wt%levoglucosan in ex-situ fixed-bed catalytic pyrolysis,a yield that is 19.6 times higher than that from pure biomass at 40 wt%catalyst loading.Recycling evaluations affirm the robust stability of the MXene catalyst,validating its potential for multiple use cycles in eco-friendly industrial levoglucosan production.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA20100000)the National Natural Science Foundation of China(41701078,41805127)+1 种基金International Partnership Program of Chinese Academy of Sciences(GJHZ1674)the Second Comprehensive Scientific Expedition on Tibetan Plateau
文摘The environmental significance of levoglucosan(LEV) records in Tibetan glacier ice layers on sub-annual to annual scales, in particular their suitability as a specific biomarker for indicating past fire changes, is poorly understood at present. In this work, a continuous LEV record was reconstructed in a central Tibetan ice core for the period 1990–2012. The LEV record was classified into two categories based on its LEV concentrations: background levels and extreme events. Annually-resolved LEV records and background levels in the ice core were strongly correlated with satellite observations of fire occurrence frequency over the northern Indian peninsula between 2003 and 2012, especially for strong fire events during the pre-monsoon season(March–May). In addition, peaks in LEV concentrations may represent extreme fire events in regions around the Tibetan Plateau. LEV records in the ice core reflect a longterm increasing trend in fire background and also an increase in fire extreme events, across the Tibetan Plateau and its surroundings. We therefore conclude that LEV records in Tibetan ice cores can be used as a powerful tool for calibrating and reconstructing past fire changes over subtropical Asia.
文摘The largest sugarcane-growing area in the United States is in South Florida. An estimated 7 million tons of dry sugarcane leafy biomass is removed from the fields before harvest by burning the leaves off the sugarcane stalks. Preharvest sugarcane leaf foliage burning is a major source of airborne particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), biogenic trace elements such as K, volatile hydrocarbons and other pollutants. In one harvesting period, approximately 22 million tons of C02, a greenhouse gas, is released, 7 million tons from leaf foliage preharvest burning alone and 15 million tons from burning sugarcane bagasse in the sugar mills for power generation. In this study, PMio was collected from Belle Glade, close to the sugarcane-growing area, and from Delray Beach, an urbanized area along the East Coast of Florida. The PM samples were analyzed for trace elements and close to organic compounds. To elucidate the importance of preharvest sugarcane biomass smoke emissions on air quality, 39 trace elements, 18 PAHs, and levoglucosan were selected to apportion ambient PM constituents. Al, Ca and to a great extend also Mg are the major soil-related trace elements and key markers for fugitive soil dust emissions. Similarly, sea salt aerosol blown from the Atlantic Ocean into Florida added appreciably to PMio trace elements concentration, especially Na and Cl. Approximately half of the sea salt aerosol (PMjo -portion) by mass is removed from the atmosphere during the transport of ocean air from Delray Beach to Belle Glade. Ambient acid displacement reactions caused a substantial portion of the Cl (30%) to be liberated from the sea salt aerosol to the atmosphere during transport as gaseous HC1. The PAH concentrations at Belle Glade were high when the biomass combustion markers levoglucosan and I< also showed the highest concentrations. This indicates that during the sugarcane harvest season, when leaf foliage is burned off just before harvest, most of the ambient PAHs associated with PMio are indeed related to preharvest burning, harvesting machinery emissions, bagasse burning in sugarcane mills, and other related activities that consume biomass and/or fossil fuels for sugarcane harvesting and processing.
基金The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China(Grants NO.21978287)the Fundamental Research Funds for the Central Universities(Y954035XX2).
文摘Pretreatment of lignocellulosic biomass is crucial for the release of biofermentable sugars for biofuels production,which could greatly alleviate the burgeoning environment and energy crisis caused by the massive usage of traditional fossil fuels.Pyrolysis is a cost-saving pretreatment process that can readily decompose biomass into levoglucosan,a promising anhydrosugar;however,many undesired toxic compounds inhibitory to downstream microbial fermentation are also generated during the pyrolysis,immensely impeding the bioconversion of levoglucosan-containing pyrolysate.Here,we took the first insight into the proteomic responses of a levoglucosan-utilizing and ethanol-producing Escherichia coli to three representative biomass-derived inhibitors,identifying large amounts of differentially expressed proteins(DEPs)that could guide the downstream metabolic engineering for the development of inhibitor-resistant strains.Fifteen up-and eight down-regulated DEPs were further identified as the biomarker stress-responsive proteins candidate for cellular tolerance to multiple inhibitors.Among these biomarker proteins,YcfR exhibiting the highest expression fold-change level was chosen as the target of overexpression to validate proteomics results and develop robust strains with enhanced inhibitor tolerance and fermentation performance.Finally,based on four plasmid-borne genes encoding the levoglucosan kinase,pyruvate decarboxylase,alcohol dehydrogenase,and protein YcfR,a new recombinant strain E.coli LGE-ycfR was successfully created,showing much higher acetic acid-,furfural-,and phenol-tolerance levels compared to the control without overexpression of ycfR.The specific growth rate,final cell density,ethanol concentration,ethanol productivity,and levoglucosan consumption rate of the recombinant were also remarkably improved.From the proteomics-guided metabolic engineering and phenotypic observations,we for the first time corroborated that YcfR is a stress-induced protein responsive to multiple biomass-derived inhibitors,and also developed an inhibitors-resistant strain that could produce bioethanol from levoglucosan in the presence of inhibitors of relatively high concentration.The newly developed E.coli LGE-ycfR strain that could eliminate the commonly-used costly detoxicification processes,is of great potential for the in situ cost-effective bioethanol production from the biomass-derived pyrolytic substrates.
基金supported by a grant funded by the Ministry of Environment(MOE)of the Republic of Korea(Nos.NIER-2024-03-00-005 and NIER-2021-03-03-007)。
文摘Polyethylene terephthalate(PET)combustion produces terephthalic acid(TPA),a key indicator of incineration processes.This study examines the diurnal variation of TPA and its association with health risks in Seoul,South Korea,based on data from Bokjeong Station.TPA concentrations were significantly higher in winter(28.12 ng/m^(3))compared to summer(12.39 ng/m^(3)),indicating increased PET-related emissions during colder months.Similarly,levoglucosan concentrations were markedly higher in winter(68.17 ng/m^(3))than in summer(16.67 ng/m^(3)),likely due to waste wood incineration.The TPA-to-organic carbon(TPA/OC)ratio was notably higher at night,suggesting more frequent PET waste combustion during nighttime hours.Elevated nighttime TPA concentrations in PM_(2.5)also indicate contributions from coal combustion or the incineration of arsenic-containing materials.The correlation between TPA and oxidative potential underscores heightened health risks associated with nighttime emissions.Moreover,volatile organic compounds(VOCs)such as benzene,toluene,and xylene were significantly higher at night,further degrading air quality.These findings highlight the critical role of nighttime waste incineration in exacerbating urban air pollution and increasing associated health risks,especially during winter.
基金supported by the Basic Research Key Project of Science and Technology Department of Yunnan Province(No.202401AS070116)the National Natural Science Foundation of China(No.21966016)。
文摘Biomass burning(BB)emits carbonaceous aerosols that significantly influence air quality in Southwest China during spring.To further understand the characteristics of spring BB and its original contribution to organic carbon(OC),daily fine particulate matter(PM_(2.5))samples were collected from March to May 2022 in Pu'er,Southwest China.The concentrations of OC,elemental carbon(EC),levoglucosan(Lev),and potassium from BB(K+BB)during the study period ranged from 5.3 to 31.2μg/m^(3),0.86-13.1μg/m^(3),0.06-0.82μg/m^(3),and 0.05-2.88μg/m^(3),respectively.To eliminate the effects of Lev degradation,this study uses the Aging of Air Mass(AAM)index to correct the atmospheric concentration of Lev and combines Bayesian mixture modeling with a molecular tracer method to assess the original contribution of BB to OC.The results indicated that the AAM index was 0.18±0.05,indicating that the degradation of Lev reached 82%.When considering the degradation of levoglucosan in the atmosphere,the primary source of BB aerosols was crop-straw combustion(71.1%),followed by the combustion of certain hardwoods and softwoods(24.9%)and grasses(4.0%).The original contribution of BB to OC was 62.4%,which was much greater than the contribution when levoglucosan degradation(23.7%)was ignored.The air mass inverse trajectories and Moderate Resolution Imaging Spectroradiometer(MODIS)fire hotspots indicated that the BB plume from Southeast Asia during spring could influence PM_(2.5)long-range transport in remote locations,and the contribution could reach 82%in Southwest China.
