Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sink...Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.展开更多
Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs).The results sho...Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs).The results showed that HCHs and DDTs were found in the soil samples from the remote high altitude areas away from source regions,which confirmed the long-range atmospheric transport phenomenon of these organochlorine pesticides(OCPs) insecticides.The OCP concentrations in the soils had a significant negative correlation with altitude;they showed a trend to increase with decreasing altitude,but the increase was not continuous,being interrupted at some moderate-altitude sites on the transect.The distances from the source region,landforms,soil properties,and physical-chemical properties of OCPs were more important than total organic carbon content to the distribution of OCPs in soils disturbed by human activities.An analysis of the compositions of HCH isomers and DDTs revealed predominantly low ratios of α-HCH to γ-HCH,ranging from 0.06 to 4.79,which suggested current lindane inputs.On the other hand,low p,p-DDT/p,p-DDE and o,p-DDT/p,p-DDT ratios were observed,indicating mainly aged historical DDT residues in the study area.展开更多
As one of the regions with intensive agriculture and rapid economic development in China,North China also has a high nitrogen(N)deposition.This study characterized the spatial pattern of N deposition in North China,co...As one of the regions with intensive agriculture and rapid economic development in China,North China also has a high nitrogen(N)deposition.This study characterized the spatial pattern of N deposition in North China,combining the tropospheric columns from satellite measurements and the simulated profiles from an atmospheric chemistry transport model.The total N deposition fluxes ranged from 16.3 to 106.5 kg N ha−1 yr−1,with an average of 54.5±17.2 kg N ha−1 yr−1.The high values were concentrated in urban and farmland areas,while low values were found in forests and grasslands with less human activities.Of the total N deposition,36%was deposited via precipitation,12%was deposited through dry particulate deposition,and the remaining 52%was comprised of dry gaseous deposition.For the seasonal variation of dry deposition,gaseous HNO3 and particulate NO3−were higher in winter and autumn,but lower in spring and summer.In contrast,gaseous NH3 and particulate NH4+were higher in spring and summer,but lower in winter and autumn.This is possibly caused by the seasonal differences in emission intensity between NOx and NH3 emission sources.The gaseous NO2 deposition did not show strong seasonal variation.The wet deposition was mainly affected by precipitation,with high values in summer and low values in winter.This research provides an objective spatial perspective and insight into the total N deposition in North China.展开更多
Characterized by scarce water resources and fragile ecosystems,Northwest China(NWC)has experienced a climate shift from warm-dry to warm-wet conditions since the 1980s that has garnered extensive concern in recent yea...Characterized by scarce water resources and fragile ecosystems,Northwest China(NWC)has experienced a climate shift from warm-dry to warm-wet conditions since the 1980s that has garnered extensive concern in recent years.In this study,the variability in extreme precipitation(EP)during 1961-2016 in different climate zones of NWC and the possible mechanisms for this variation are investigated.The results show that the EP trends significantly increased in most of the westerly zone(WZ)and plateau zone(PZ),while the EP trends did not significantly decrease in the monsoon zone(MZ).The start dates of extreme precipitation(SDEP)and end dates of extreme precipitation(EDEP)advanced and were postponed,respectively,in the WZ and PZ,while the opposite occurred in the MZ.Summer atmospheric circulation,water vapor transport,and atmospheric instability over NWC varied greatly with the interdecadal shift in EP before and after 1986.During 1986-2016,upper-level divergence and lower-level convergence occurred in the MZ and PZ,which strengthened ascending flow.In addition,the summer water vapor and atmospheric instability increased in the WZ and PZ.These characteristics created favorable conditions for increased occurrences of EP in the WZ and PZ in summer.Conversely,the upper-level convergence and lower-level divergence in the MZ strengthened descending flow.Decreases in summer water vapor and atmospheric instability occurred in the MZ after 1986.Hence,the environmental conditions in the MZ may have prevented the occurrence and development of EP in summer during 1986-2016.展开更多
Establishing alternative methods for freshwater production is imperative to effectively alleviate global water scarcity,particularly in land-locked arid regions.In this context,extracting water from the ubiquitous atm...Establishing alternative methods for freshwater production is imperative to effectively alleviate global water scarcity,particularly in land-locked arid regions.In this context,extracting water from the ubiquitous atmospheric moisture is an ingenious strategy for decentralized freshwater production.Sorption-based atmospheric water harvesting(SAWH)shows strong potential for supplying liquid water in a portable and sustainable way even in desert environments.Herein,the latest progress in SAWH technology in terms of materials,devices,and systems is reviewed.Recent advances in sorbent materials with improved water uptake capacity and accelerated sorption–desorption kinetics,including physical sorbents,polymeric hydrogels,composite sorbents,and ionic solutions,are discussed.The thermal designs of SAWH devices for improving energy utilization efficiency,heat transfer,and mass transport are evaluated,and the development of representative SAWH prototypes is clarified in a chronological order.Thereafter,state-of-the-art operation patterns of SAWH systems,incorporating intermittent,daytime continuous and 24-hour continuous patterns,are examined.Furthermore,current challenges and future research goals of this cutting-edge field are outlined.This review highlights the irreplaceable role of heat and mass transfer enhancement and facile structural improvement for constructing high-yield water harvesters.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41405129&41375130)the National Key Research and Development of China(Grant No.2017YFC0209701)
文摘Atmospheric CO_2 and CH_4 have been continuously measured since 2009 at Longfengshan WMO/GAW station(LFS) in China. Variations of the mole fractions, influence of long-distance transport, effects of local sources/sinks and the characteristics of synoptic scale variations have been studied based on the records from 2009 to 2013. Both the CO_2 and CH_4 mole fractions display increasing trends in the last five years, with growth rates of 3.1±0.02 ppm yr.1 for CO_2 and 8±0.04 ppb yr.1(standard error, 1-σ)for CH_4. In summer, the regional CO_2 mole fractions are apparently lower than the Marine Boundary Layer reference, with the lowest value of.13.6±0.7 ppm in July, while the CH_4 values are higher than the MBL reference, with the maximum of 139±6 ppb.From 9 to 17(Local time, LT) in summer, the atmospheric CO_2 mole fractions at 10 m a.g.l. are always lower than at 80 m, with a mean difference of.1.1±0.2 ppm, indicating that the flask sampling approach deployed may underestimate the background mole fractions in summer. In winter, anthropogenic emissions dominate the regional CO_2 and CH_4 mole fractions. Cluster analysis of backward trajectories shows that atmospheric CO_2 and CH_4 at LFS are influenced by anthropogenic emissions from the southwest(Changchun and Jilin city) all year. The synoptic scale variations indicate that the northeastern China plain acts as an important source of atmospheric CO_2 and CH_4 in winter.
基金Supported by the National Natural Science Foundation of China(No.40473043)the Research Fund for the Doctoral Program of Higher Education,China(No.20090145110004)
文摘Soil samples collected from several sites along an altitudinal transect on the eastern slope of the Tibetan Plateau were analyzed for hexachlorobenzenes(HCHs) and dichlorodiphenyltrichloroethanes(DDTs).The results showed that HCHs and DDTs were found in the soil samples from the remote high altitude areas away from source regions,which confirmed the long-range atmospheric transport phenomenon of these organochlorine pesticides(OCPs) insecticides.The OCP concentrations in the soils had a significant negative correlation with altitude;they showed a trend to increase with decreasing altitude,but the increase was not continuous,being interrupted at some moderate-altitude sites on the transect.The distances from the source region,landforms,soil properties,and physical-chemical properties of OCPs were more important than total organic carbon content to the distribution of OCPs in soils disturbed by human activities.An analysis of the compositions of HCH isomers and DDTs revealed predominantly low ratios of α-HCH to γ-HCH,ranging from 0.06 to 4.79,which suggested current lindane inputs.On the other hand,low p,p-DDT/p,p-DDE and o,p-DDT/p,p-DDT ratios were observed,indicating mainly aged historical DDT residues in the study area.
基金This study was supported by the National Natural Science Foundation of China[grant numbers 41471343 and 41601457].
文摘As one of the regions with intensive agriculture and rapid economic development in China,North China also has a high nitrogen(N)deposition.This study characterized the spatial pattern of N deposition in North China,combining the tropospheric columns from satellite measurements and the simulated profiles from an atmospheric chemistry transport model.The total N deposition fluxes ranged from 16.3 to 106.5 kg N ha−1 yr−1,with an average of 54.5±17.2 kg N ha−1 yr−1.The high values were concentrated in urban and farmland areas,while low values were found in forests and grasslands with less human activities.Of the total N deposition,36%was deposited via precipitation,12%was deposited through dry particulate deposition,and the remaining 52%was comprised of dry gaseous deposition.For the seasonal variation of dry deposition,gaseous HNO3 and particulate NO3−were higher in winter and autumn,but lower in spring and summer.In contrast,gaseous NH3 and particulate NH4+were higher in spring and summer,but lower in winter and autumn.This is possibly caused by the seasonal differences in emission intensity between NOx and NH3 emission sources.The gaseous NO2 deposition did not show strong seasonal variation.The wet deposition was mainly affected by precipitation,with high values in summer and low values in winter.This research provides an objective spatial perspective and insight into the total N deposition in North China.
基金The authors would like to extend sincere gratitude for the support from the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0103)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA2006010101)+2 种基金the National Natural Science Foundation of China(91837208)the National Key Research and Development Program of China(2018YFC1505701)This work was jointly supported by the National Natural Science Foundation of China(42075043)and the Youth Innovation Promotion Association CAS.
文摘Characterized by scarce water resources and fragile ecosystems,Northwest China(NWC)has experienced a climate shift from warm-dry to warm-wet conditions since the 1980s that has garnered extensive concern in recent years.In this study,the variability in extreme precipitation(EP)during 1961-2016 in different climate zones of NWC and the possible mechanisms for this variation are investigated.The results show that the EP trends significantly increased in most of the westerly zone(WZ)and plateau zone(PZ),while the EP trends did not significantly decrease in the monsoon zone(MZ).The start dates of extreme precipitation(SDEP)and end dates of extreme precipitation(EDEP)advanced and were postponed,respectively,in the WZ and PZ,while the opposite occurred in the MZ.Summer atmospheric circulation,water vapor transport,and atmospheric instability over NWC varied greatly with the interdecadal shift in EP before and after 1986.During 1986-2016,upper-level divergence and lower-level convergence occurred in the MZ and PZ,which strengthened ascending flow.In addition,the summer water vapor and atmospheric instability increased in the WZ and PZ.These characteristics created favorable conditions for increased occurrences of EP in the WZ and PZ in summer.Conversely,the upper-level convergence and lower-level divergence in the MZ strengthened descending flow.Decreases in summer water vapor and atmospheric instability occurred in the MZ after 1986.Hence,the environmental conditions in the MZ may have prevented the occurrence and development of EP in summer during 1986-2016.
基金supported by the National Natural Science Funds for Distinguished Young Scholar of China(52325601)the Major Program of National Natural Science Foundation of China(52293412)。
文摘Establishing alternative methods for freshwater production is imperative to effectively alleviate global water scarcity,particularly in land-locked arid regions.In this context,extracting water from the ubiquitous atmospheric moisture is an ingenious strategy for decentralized freshwater production.Sorption-based atmospheric water harvesting(SAWH)shows strong potential for supplying liquid water in a portable and sustainable way even in desert environments.Herein,the latest progress in SAWH technology in terms of materials,devices,and systems is reviewed.Recent advances in sorbent materials with improved water uptake capacity and accelerated sorption–desorption kinetics,including physical sorbents,polymeric hydrogels,composite sorbents,and ionic solutions,are discussed.The thermal designs of SAWH devices for improving energy utilization efficiency,heat transfer,and mass transport are evaluated,and the development of representative SAWH prototypes is clarified in a chronological order.Thereafter,state-of-the-art operation patterns of SAWH systems,incorporating intermittent,daytime continuous and 24-hour continuous patterns,are examined.Furthermore,current challenges and future research goals of this cutting-edge field are outlined.This review highlights the irreplaceable role of heat and mass transfer enhancement and facile structural improvement for constructing high-yield water harvesters.
