Air pollution is a grand challenge of our time due to its multitude of adverse impacts on environment and society,with the scale of impacts more severe in developing countries,including China.Thus,China has initiated ...Air pollution is a grand challenge of our time due to its multitude of adverse impacts on environment and society,with the scale of impacts more severe in developing countries,including China.Thus,China has initiated and implemented strict air pollution control measures over last several years to reduce impacts of air pollution.Monitoring data from Jan 2015 to Dec 2019 on six criteria air pollutants(SO_(2),NO_(2),CO,O_(3),PM_(2.5),and PM_(10))at eight sites in southwestern China were investigated to understand the situation and analyze the impacts of transboundary air pollutants in this region.In terms of seasonal variation,the maximum concentrations of air pollutants at these sites were observed in winter or spring season depending on individual site.For diurnal variation,surface ozone peaked in the afternoon while the other pollutants had a bimodal pattern with peaks in the morning and late afternoon.There was limited transport of domestic emissions of air pollutants in China to these sites.Local emissions enhanced the concentrations of air pollutants during some pollution events.Mostly,the transboundary transport of air pollution from South Asia and Southeast Asia was associated with high concentrations of most air pollutants observed in southwestern China.Since air pollutants can be transported to southwestern China over long distances from the source regions,it is necessary to conduct more research to properly attribute and quantify transboundary transport of air pollutants,which will provide more solid scientific guidance for air pollution management in southwestern China.展开更多
Air pollutants can be transported to the pristine regions such as the Tibetan Plateau,by monsoon and stratospheric intrusion.The Tibetan Plateau region has limited local anthropogenic emissions,while this region is in...Air pollutants can be transported to the pristine regions such as the Tibetan Plateau,by monsoon and stratospheric intrusion.The Tibetan Plateau region has limited local anthropogenic emissions,while this region is influenced strongly by transport of heavy emissions mainly from South Asia.We conducted a comprehensive study on various air pollutants (PM_(2.5),total gaseous mercury,and surface ozone) at Nam Co Station in the inland Tibetan Plateau.Monthly mean PM_(2.5)concentration at Nam Co peaked in April before monsoon season,and decreased during the whole monsoon season (June–September).Monthly mean total gaseous mercury concentrations at Nam Co peaked in July and were in high levels during monsoon season.The Indian summer monsoon acted as a facilitator for transporting gaseous pollutants (total gaseous mercury) but a suppressor for particulate pollutants (PM_(2.5)) during the monsoon season.Different from both PM_(2.5)and total gaseous mercury variabilities,surface ozone concentrations at Nam Co are primarily attributed to stratospheric intrusion of ozone and peaked in May.The effects of the Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau are complex and require further studies.展开更多
Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this st...Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury(PBM) and the corresponding seasonality, sources, and influencing factors.The PBM concentration in total suspended particulate(TSP) matter ranged from 6.8 pg m^(-3) to351.7 pg m^(-3)(mean of 99.7 ± 92.6 pg m^(-3)), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content(PBM/TSP) ranged from 68.2 ng g^(-1) to 1744.8 ng g^(-1)(mean of 446.9 ±312.7 ng g^(-1)), indicating anthropogenic enrichment. The PBM levels were higher in the dry season(i.e.,winter and the pre-monsoon period) than in the wet season(i.e., the monsoon period). In addition, the δ^(202) Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ^(199) Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 lg m^(-2) yr^(-1). This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.展开更多
The location of Central Asia,almost at the center of the global dust belt region,makes it susceptible for dust events.The studies on atmospheric impact of dust over the region are very limited despite the large area o...The location of Central Asia,almost at the center of the global dust belt region,makes it susceptible for dust events.The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions (Tianshan,Hindu Kush-KarakoramHimalayas,and Tibetan Plateau).In this study,we analyse and explain the modification in aerosols’physical,optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010–2018 at the AERONET station in Dushanbe,Tajikistan.Aerosol episodes were classified as strong anthropogenic,strong dust and extreme dust.The mean aerosol optical depth (AOD) during these three types of events was observed a factor of ~3,3.5 and 6.6,respectively,higher than the mean AOD for the period 2010–2018.The corresponding mean fine-mode fraction was 0.94,0.20 and 0.16,respectively,clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events,whereas coarse-mode dust aerosol dominated during the other two types of events.This was corroborated by the relationships among various aerosol parameters (AOD vs.AE,and EAE vs.AAE,SSA and RRI).The mean aerosol radiative forcing (ARF) at the top of the atmosphere (ARF_(TOA)),the bottom of the atmosphere (ARF_(BOA)),and in the atmosphere (ARFATM) were -35±7,-73±16,and38±17 Wm^(-2)during strong anthropogenic events,-48±12,-85±24,and 37±15 Wm^(-2)during strong dust event,and -68±19,-117±38,and 49±21 Wm-2during extreme dust events.Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5–1.6 K day^(-1)(strong anthropogenic events),0.4–1.9 K day^(-1)(strong dust events) and 0.8–2.7 K day^(-1)(extreme dust events).The source regions of air masses to Dushanbe during the onset of such events are also identified.Our study contributes to the understanding of dust and anthropogenic aerosols,in particular the extreme events and their disproportionally high radiative impacts over Central Asia.展开更多
Climate warming is causing rapid permafrost degradation,including thaw-induced subsidence,potentially resulting in heightened carbon release.Nevertheless,our understanding of the levels and variations of carbon compon...Climate warming is causing rapid permafrost degradation,including thaw-induced subsidence,potentially resulting in heightened carbon release.Nevertheless,our understanding of the levels and variations of carbon components in permafrost,particularly during the degradation process,remains limited.The uncertainties arising from this process lead to inaccurate assessments of the climate effects during permafrost degradation.With vast expanses of permafrost in the Tibetan Plateau,there is limited research available on SOC components,particularly in the central Tibetan Plateau.Given remarkable variations in hydrothermal conditions across different areas of the Tibetan Plateau,the existing limited studies make it challenging to assess the overall SOC components in the permafrost across the Tibetan Plateau and simulate their future changes.In this study,we examined the properties of soil organic carbon(SOC)and microbial necromass carbon(MicrobialNC)in a representative permafrost thaw-subsidence area at the southern edge of continuous permafrost in the central Tibetan Plateau.The results indicate that prior to the thaw-subsidence,the permafrost had a SOC content of 72.68±18.53 mg g^(-1),with MicrobialNC accounting for 49.6%.The thaw-subsidence of permafrost led to a 56.4%reduction in SOC,with MicrobialNC accounting for 70.0%of the lost SOC.MicrobialNC constitutes the primary component of permafrost SOC,and it is the main component that is lost during thaw-subsidence formation.Changes in MicrobialNC are primarily correlated with factors pH,plant input,and microbial properties.The present study holds crucial implications for both the ecological and biogeochemical processes associated with carbon release from permafrost,and it furnishes essential data necessary for modeling the global response of permafrost to climate warming.Based on this study and previous research,permafrost thawing in the Tibetan Plateau causes substantial loss of SOC.However,there's remarkable heterogeneity in SOC component changes across different regions,warranting further in-depth investigation.展开更多
Central Asia is one of the largest arid areas on earth,yet little is known about the concentration levels and risks of mercury(Hg)in the soils of this region.In this study,extensive sampling of topsoils(0-10 cm)from r...Central Asia is one of the largest arid areas on earth,yet little is known about the concentration levels and risks of mercury(Hg)in the soils of this region.In this study,extensive sampling of topsoils(0-10 cm)from representative landscapes was carried out over Central Asia(i.e.,Tajikistan,Uzbekistan,and Kyrgyzstan).The total mercury(THg)concentrations in topsoils varied widely from 1.6 to 908.0 ng/g,with high values observed in samples collected in the capital cities and urban areas.Topsoil THg concentrations among different landscapes showed a decreasing order of urban(79.8±184.0 ng/g)>woodland(27.3±28.9 ng/g)>grassland(20.6±15.9 ng/g)>farmland(18.3±9.5 ng/g)>desert(12.3±8.0 ng/g).High THg concentrations were found in the capital cities/urban clusters,followed by a gradual decrease towards the peripheries.THg concentrations were found to be negatively correlated with the distance from the sampling sites to their nearest cities,indicating that anthropogenic emissions significantly influenced the spatial distribution of topsoil Hg.A significant correlation between THg concentrations and topsoil total organic carbon(TOC)contents was also observed,suggesting that TOC played an essential role in the spatial distribution of topsoil Hg.The assessments of pollution and potential ecological risk suggested that topsoils in highly densely-populated areas were contaminated by Hg and had higher degrees of potential ecological risks.The health risk assessment results showed that the exposure risk of topsoil Hg to children was higher than that to adults.Fortunately,there was no unacceptable human health risk of topsoil Hg.This study clarified the spatial distribution and risks of Hg in the Central Asian topsoils,offering new insight into the risk prevention and control of soil Hg.展开更多
基金This study was supported by the National Natural Science Foundation of China(41907328)the Strategic Priority Research Program of Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(XDA20040501)+4 种基金State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2020)financial support from the Youth Innovation Promotion Association of Chinese Academy of Sciences(2016070)financial support from the Chinese Academy of Sciences‘‘Light of West China”ProgramCAS-President’s International Fellowship Initiative(PIFI,Grant No.2019PC0076)support provided by the Institute for Advanced Sustainability Studies(IASS),which is funded by the German Federal Ministry for Education and Research(BMBF)and the Brandenburg Ministry for Science,Research and Culture(MWFK).
文摘Air pollution is a grand challenge of our time due to its multitude of adverse impacts on environment and society,with the scale of impacts more severe in developing countries,including China.Thus,China has initiated and implemented strict air pollution control measures over last several years to reduce impacts of air pollution.Monitoring data from Jan 2015 to Dec 2019 on six criteria air pollutants(SO_(2),NO_(2),CO,O_(3),PM_(2.5),and PM_(10))at eight sites in southwestern China were investigated to understand the situation and analyze the impacts of transboundary air pollutants in this region.In terms of seasonal variation,the maximum concentrations of air pollutants at these sites were observed in winter or spring season depending on individual site.For diurnal variation,surface ozone peaked in the afternoon while the other pollutants had a bimodal pattern with peaks in the morning and late afternoon.There was limited transport of domestic emissions of air pollutants in China to these sites.Local emissions enhanced the concentrations of air pollutants during some pollution events.Mostly,the transboundary transport of air pollution from South Asia and Southeast Asia was associated with high concentrations of most air pollutants observed in southwestern China.Since air pollutants can be transported to southwestern China over long distances from the source regions,it is necessary to conduct more research to properly attribute and quantify transboundary transport of air pollutants,which will provide more solid scientific guidance for air pollution management in southwestern China.
基金This study was supported by the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA20040501)the National Natural Science Foundation of China(41907328)+3 种基金State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2020)financial support from the Chinese Academy of Sciences"Light of West China"Programfinancial support from the Youth Innovation Promotion Association of CAS(2016070)the support provided by the Institute for Advanced Sustainability Studies(IASS),which is funded by the German Federal Ministry for Education and Research(BMBF)and the Brandenburg Ministry for Science,Research and Culture(MWFK)。
文摘Air pollutants can be transported to the pristine regions such as the Tibetan Plateau,by monsoon and stratospheric intrusion.The Tibetan Plateau region has limited local anthropogenic emissions,while this region is influenced strongly by transport of heavy emissions mainly from South Asia.We conducted a comprehensive study on various air pollutants (PM_(2.5),total gaseous mercury,and surface ozone) at Nam Co Station in the inland Tibetan Plateau.Monthly mean PM_(2.5)concentration at Nam Co peaked in April before monsoon season,and decreased during the whole monsoon season (June–September).Monthly mean total gaseous mercury concentrations at Nam Co peaked in July and were in high levels during monsoon season.The Indian summer monsoon acted as a facilitator for transporting gaseous pollutants (total gaseous mercury) but a suppressor for particulate pollutants (PM_(2.5)) during the monsoon season.Different from both PM_(2.5)and total gaseous mercury variabilities,surface ozone concentrations at Nam Co are primarily attributed to stratospheric intrusion of ozone and peaked in May.The effects of the Indian summer monsoon and stratospheric intrusion on air pollutants in the inland Tibetan Plateau are complex and require further studies.
基金supported by the National Natural Science Foundation of China (Grant Nos.41801042 and 41630754)the Second Tibetan Plateau Scientific Expedition and Research Program (STEP)(Grant No.2019QZKK0605)+3 种基金State Key Laboratory of Cryospheric SciencesChinese Academy of Sciences (Grant No.SKLCSZZ-2020)Grant received from the Asia-Pacific Network for Global Change Research (APN)(Grant reference:CRECS2020-07MYTripathee) is highly appreciatedsupported by a PIFI fellowship from the Chinese Academy of Sciences as a young staff member (2020FYC0001)。
文摘Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury(PBM) and the corresponding seasonality, sources, and influencing factors.The PBM concentration in total suspended particulate(TSP) matter ranged from 6.8 pg m^(-3) to351.7 pg m^(-3)(mean of 99.7 ± 92.6 pg m^(-3)), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content(PBM/TSP) ranged from 68.2 ng g^(-1) to 1744.8 ng g^(-1)(mean of 446.9 ±312.7 ng g^(-1)), indicating anthropogenic enrichment. The PBM levels were higher in the dry season(i.e.,winter and the pre-monsoon period) than in the wet season(i.e., the monsoon period). In addition, the δ^(202) Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ^(199) Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 lg m^(-2) yr^(-1). This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.
基金This study was supported by the Strategic Priority Research Program of Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(XDA20040501)the National Natural Science Foundation of China(41907328,41630754)+3 种基金State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2020)CAS-President’s International Fellowship Initiative(PIFI,Grant no.2019PC0076)the support provided by the Institute for Advanced Sustainability Studies(IASS),which is funded by the German Federal Ministry for Education and Research(BMBF)and the Brandenburg Ministry for Science,Research and Culture(MWFK)the International Science and Technology Center(ISTC)Projects(T-1688 and T-2076)。
文摘The location of Central Asia,almost at the center of the global dust belt region,makes it susceptible for dust events.The studies on atmospheric impact of dust over the region are very limited despite the large area occupied by the region and its proximity to the mountain regions (Tianshan,Hindu Kush-KarakoramHimalayas,and Tibetan Plateau).In this study,we analyse and explain the modification in aerosols’physical,optical and radiative properties during various levels of aerosol loading observed over Central Asia utilizing the data collected during 2010–2018 at the AERONET station in Dushanbe,Tajikistan.Aerosol episodes were classified as strong anthropogenic,strong dust and extreme dust.The mean aerosol optical depth (AOD) during these three types of events was observed a factor of ~3,3.5 and 6.6,respectively,higher than the mean AOD for the period 2010–2018.The corresponding mean fine-mode fraction was 0.94,0.20 and 0.16,respectively,clearly indicating the dominance of fine-mode anthropogenic aerosol during the first type of events,whereas coarse-mode dust aerosol dominated during the other two types of events.This was corroborated by the relationships among various aerosol parameters (AOD vs.AE,and EAE vs.AAE,SSA and RRI).The mean aerosol radiative forcing (ARF) at the top of the atmosphere (ARF_(TOA)),the bottom of the atmosphere (ARF_(BOA)),and in the atmosphere (ARFATM) were -35±7,-73±16,and38±17 Wm^(-2)during strong anthropogenic events,-48±12,-85±24,and 37±15 Wm^(-2)during strong dust event,and -68±19,-117±38,and 49±21 Wm-2during extreme dust events.Increase in aerosol loading enhanced the aerosol-induced atmospheric heating rate to 0.5–1.6 K day^(-1)(strong anthropogenic events),0.4–1.9 K day^(-1)(strong dust events) and 0.8–2.7 K day^(-1)(extreme dust events).The source regions of air masses to Dushanbe during the onset of such events are also identified.Our study contributes to the understanding of dust and anthropogenic aerosols,in particular the extreme events and their disproportionally high radiative impacts over Central Asia.
基金This study was supported by the National Natural Science Foundation of China(U23A2062,32361133551)State Key Laboratory of Cryospheric Science(SKLCS-ZZ-2023)+1 种基金Second Tibetan Plateau Scientific Expedition and Research Program_(STEP,2019QZKK0605)NaturalScience FoundationoGf ansuProvince(21JR7RA500 and 22ZD6FA005).
文摘Climate warming is causing rapid permafrost degradation,including thaw-induced subsidence,potentially resulting in heightened carbon release.Nevertheless,our understanding of the levels and variations of carbon components in permafrost,particularly during the degradation process,remains limited.The uncertainties arising from this process lead to inaccurate assessments of the climate effects during permafrost degradation.With vast expanses of permafrost in the Tibetan Plateau,there is limited research available on SOC components,particularly in the central Tibetan Plateau.Given remarkable variations in hydrothermal conditions across different areas of the Tibetan Plateau,the existing limited studies make it challenging to assess the overall SOC components in the permafrost across the Tibetan Plateau and simulate their future changes.In this study,we examined the properties of soil organic carbon(SOC)and microbial necromass carbon(MicrobialNC)in a representative permafrost thaw-subsidence area at the southern edge of continuous permafrost in the central Tibetan Plateau.The results indicate that prior to the thaw-subsidence,the permafrost had a SOC content of 72.68±18.53 mg g^(-1),with MicrobialNC accounting for 49.6%.The thaw-subsidence of permafrost led to a 56.4%reduction in SOC,with MicrobialNC accounting for 70.0%of the lost SOC.MicrobialNC constitutes the primary component of permafrost SOC,and it is the main component that is lost during thaw-subsidence formation.Changes in MicrobialNC are primarily correlated with factors pH,plant input,and microbial properties.The present study holds crucial implications for both the ecological and biogeochemical processes associated with carbon release from permafrost,and it furnishes essential data necessary for modeling the global response of permafrost to climate warming.Based on this study and previous research,permafrost thawing in the Tibetan Plateau causes substantial loss of SOC.However,there's remarkable heterogeneity in SOC component changes across different regions,warranting further in-depth investigation.
基金This study was supported by Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(XDA20040501)State Key Labora-tory of Cryospheric Science,Chinese Academy of Sciences(Grant No.SKLCS-ZZ-2022)+1 种基金China Postdoctoral Science Foundation(2021M693375)the Startup Foundation for Introducing Talent of NUIST(2022r024).
文摘Central Asia is one of the largest arid areas on earth,yet little is known about the concentration levels and risks of mercury(Hg)in the soils of this region.In this study,extensive sampling of topsoils(0-10 cm)from representative landscapes was carried out over Central Asia(i.e.,Tajikistan,Uzbekistan,and Kyrgyzstan).The total mercury(THg)concentrations in topsoils varied widely from 1.6 to 908.0 ng/g,with high values observed in samples collected in the capital cities and urban areas.Topsoil THg concentrations among different landscapes showed a decreasing order of urban(79.8±184.0 ng/g)>woodland(27.3±28.9 ng/g)>grassland(20.6±15.9 ng/g)>farmland(18.3±9.5 ng/g)>desert(12.3±8.0 ng/g).High THg concentrations were found in the capital cities/urban clusters,followed by a gradual decrease towards the peripheries.THg concentrations were found to be negatively correlated with the distance from the sampling sites to their nearest cities,indicating that anthropogenic emissions significantly influenced the spatial distribution of topsoil Hg.A significant correlation between THg concentrations and topsoil total organic carbon(TOC)contents was also observed,suggesting that TOC played an essential role in the spatial distribution of topsoil Hg.The assessments of pollution and potential ecological risk suggested that topsoils in highly densely-populated areas were contaminated by Hg and had higher degrees of potential ecological risks.The health risk assessment results showed that the exposure risk of topsoil Hg to children was higher than that to adults.Fortunately,there was no unacceptable human health risk of topsoil Hg.This study clarified the spatial distribution and risks of Hg in the Central Asian topsoils,offering new insight into the risk prevention and control of soil Hg.
