The push-pull framework provides a useful approach for examining the tourist motivation. This paper takes the world heritage-Huangshan Mountain as a sample. From the two different aspects of pull and push factors, the...The push-pull framework provides a useful approach for examining the tourist motivation. This paper takes the world heritage-Huangshan Mountain as a sample. From the two different aspects of pull and push factors, the underlying features of visitors′ motives to Huangshan Mountain are analyzed with the help of factor analysis. As a result, five push factors and four pull factors are identified. Further analyses investigate differences in the push and pull factors among different socio-demographic subgroups with one-way ANOVA analysis. The result of the study affords us useful references for development, protection and marketing expansion of mountain resorts.展开更多
A small number of copepod species have adapted to an existence in the extreme habitat of hypersaline water. 13 copepod species have been recorded in the hypersaline waters of Crimea （the largest peninsula in the Blac...A small number of copepod species have adapted to an existence in the extreme habitat of hypersaline water. 13 copepod species have been recorded in the hypersaline waters of Crimea （the largest peninsula in the Black Sea with over 50 hypersaline lakes）. Summarizing our own and literal_re data, the author concludes that the Crimean extreme environment is not an exception： copepod species dwell in hypersaline waters worldwide. There are at least 26 copepod species around the world living at salinity above 100; among them 12 species are found at salinity higher than 200. In the Crimea Cletocamptus retrogressus is found at salinity 360×10^-3 （with a density of 1 320 individuals/m^3） and Arctodiaptomus salinus at salinity 300×10^-3 （with a density of 343 individuals/m^3）. Those species are probably the most halotolerant copepod species in the world. High halotolerance of osmoconforming copepods may be explained by exoosmolyte consumption, mainly with food. High tolerance to many factors in adults, availability of resting stages, and an opportunity of long-distance transportation of resting stages by birds and/or winds are responsible for the wide geographic distribution of these halophilic copepods.展开更多
AIM To investigate the role of interferon regulatory factor 5(IRF5) in reversing polarization of lung macrophages during severe acute pancreatitis(SAP) in vitro.METHODS A mouse SAP model was established by intraperito...AIM To investigate the role of interferon regulatory factor 5(IRF5) in reversing polarization of lung macrophages during severe acute pancreatitis(SAP) in vitro.METHODS A mouse SAP model was established by intraperitoneal(ip) injections of 20 μg/kg body weight caerulein. Pathological changes in the lung were observed by hematoxylin and eosin staining. Lung macrophages were isolated from bronchoalveolar lavage fluid. The quantity and purity of lung macrophages were detectedby fluorescence-activated cell sorting and evaluated by real-time polymerase chain reaction(RT-PCR). They were treated with IL-4/IRF5 specific siR NA(IRF5 siR NA) to reverse their polarization and were evaluated by detecting markers expression of M1/M2 using RTPCR.RESULTS SAP associated acute lung injury(ALI) was induced successfully by ip injections of caerulein, which was confirmed by histopathology. Lung macrophages expressed high levels of IRF5 as M1 phenotype during the early acute pancreatitis stages. Reduction of IRF5 expression by IRF5 siR NA reversed the action of macrophages from M1 to M2 phenotype in vitro. The expressions of M1 markers, including IRF5(S + IRF5 siR NA vs S + PBS, 0.013 ± 0.01 vs 0.054 ± 0.047, P < 0.01), TNF-α(S + IRF5 siR NA vs S + PBS, 0.0003 ± 0.0002 vs 0.019 ± 0.018, P < 0.001), iN OS(S + IRF5 siR NA vs S + PBS, 0.0003 ± 0.0002 vs 0.026 ± 0.018, P < 0.001) and IL-12(S + IRF5 si RNA vs S + PBS, 0.000005 ± 0.00004 vs 0.024 ± 0.016, P < 0.001), were decreased. In contrast, the expressions of M2 markers, including IL-10(S + IRF5 siR NA vs S + PBS, 0.060 ± 0.055 vs 0.0230 ± 0.018, P < 0.01) and Arg-1(S + IRF5 siR NA vs S + PBS, 0.910 ± 0.788 vs 0.0036 ± 0.0025, P < 0.001), were increased. IRF5 si RNA could reverse the lung macrophage polarization more effectively than IL-4.CONCLUSION Treatment with IRF5 siR NA can reverse the pancreatitisinduced activation of lung macrophages from M1 phenotype to M2 phenotype in SAP associated with ALI.展开更多
This study focuses on examining the characteristics of climate factors and extreme climate events in Northeast China during 1961- 2010 by using daily data from 104 stations, including surface air temperature, precipit...This study focuses on examining the characteristics of climate factors and extreme climate events in Northeast China during 1961- 2010 by using daily data from 104 stations, including surface air temperature, precipitation, wind speed, sunshine duration, and snow depth. Results show that annual mean temperature increased at a significant rate of 0.35℃ per decade, most notably in the Lesser Khingan Mountains and in winter. Annual rainfall had no obvious linear trend, while rainy days had a significant decreasing trend. So, the rain intensity increased. High-temperature days had a weak increasing trend, and low-temperature days and cold wave showed significant decreasing trends with rates of 3.9 d per decade and -0.64 times per decade, respectively. Frequency and spatial scope of low-temperature hazard reduced significantly. Warm days and warm nights significantly increased at 1.0 and 2.4 d per decade, while cold days and cold nights decreased significantly at -1.8 and -4.1 d per decade, respectively. The nighttime warming rate was much higher than that for daytime, indicating that nighttime warming had a greater contribution to the overall warming trend than daytime warming. The annual mean wind speed, gale days, and sunshine duration had significant decreasing trends at rates of-0.21 m s-1 per decade, -4.0 d per decade and -43.3 h per decade, respectively. The snow cover onset dates postponed at a rate of 1.2 d per decade, and the snow cover end date advanced at 1.5 d per decade, which leads to shorter snow cover duration by -2.7 d per decade. Meanwhile, the maximum snow depth decreased at -0.52 cm per decade. In addition, the snow cover duration shows a higher correlation with precipitation than with temperature, which suggests that precipitation plays a more important role in maintaining snow cover duration than temperature.展开更多
Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone...Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone changes are also discussed by using the satellite ozone data and the ground-measured ozone data at two Antarctic stations as well as the NCEP/NCAR reanalysis data. The results show that equivalent effective stratospheric chlorine (EESC) and stratospheric temperature are two important factors influencing the ozone hole. The column ozone at Zhongshan and Syowa stations is significantly related with EESC and stratospheric temperature, which means that even though the two stations are both located on the edge of the ozone hole, EESC and stratospheric temperature still played a very important role in column ozone changes, and mean while verifies that EESC is applicable on the coast of east Antarctic continent. Decadal changes in EESC are similar with those of the ozone hole, and inter-annual variations of ozone are closely related with stratospheric temperature. Based on the relation of EESC and ozone hole size, it can be projected that the ozone hole size will gradually reduce to the 1980's level from 2010 to around 2070. Of course there might exist many uncertainties in the projection, which therefore needs to be further studied.展开更多
Daily climate data at 110 stations during 1961-2010 were selected to examine the changing characteristics of climate factors and extreme climate events in South China. The annual mean surface air temperature has incre...Daily climate data at 110 stations during 1961-2010 were selected to examine the changing characteristics of climate factors and extreme climate events in South China. The annual mean surface air temperature has increased significantly by 0.16℃ per decade, most notably in the Pearl River Delta and in winter. The increase rate of the annual extreme minimum temperature (0.48℃ per decade) is over twice that of the annual extreme maximum temperature (0.20℃ per decade), and the increase of the mean temperature is mainly the result of the increase of the extreme minimum temperature. The increase rate of high-temperature days (1.1 d per decade) is close to the decrease rate of low-temperature days (-1.3 d per decade). The rainfall has not shown any significant trend, but the number of rainy days has decreased and the rain intensity has increased. The regional mean sunshine duration has a significant decreasing trend of -40.9 h per decade, and the number of hazy days has a significant increasing trend of 6.3 d per decade. The decrease of sunshine duration is mainly caused by the increase of total cloud, not by the increase of hazy days in South China. Both the regional mean pan evaporation and mean wind speed have significant decreasing trends of -65.9 mm per decade and -0.11 m s-1 per decade, respectively. The decrease of both sunshine duration and mean wind speed plays an important role in the decrease of pan evaporation. The number of landing tropical cyclones has an insignificant decreasing trend of -0.6 per decade, but their intensities show a weak increasing trend. The formation location of tropical cyclones landing in South China has converged towards 10-19°N, and the landing position has shown a northward trend. The date of the first landfall tropical cyclone postpones 1.8 d per decade, and the date of the last landfall advances 3.6 d per decade, resulting in reduction of the typhoon season by 5.4 d per decade.展开更多
The coupling between system and reservoir is considered to be linear in the coordinates of the bath but nonlinear in the system's coordinate. A dissipative threshold is observed at finite temperatures due to nonli...The coupling between system and reservoir is considered to be linear in the coordinates of the bath but nonlinear in the system's coordinate. A dissipative threshold is observed at finite temperatures due to nonlinear dissipation. The quantum decay rate of a metastable state including higher-order expanded terms of the coupling form function is proposed, which can be strongly decreased at finite temperatures when the quantum dissipative threshold is added to the saddle point of the potential.展开更多
Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equi...Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equilibrium method. The calculation results present that the safety factors of pillars in Sections 19, 20, 24, 28 are less than 1.3, and those of unstable sections are identified preliminarily. Further, a numerical investigation in Sections 18, 20, 22, 24, 25 and 28 implemented with numerical code RFPA20 is employed to further validate the pillar performance and the stability of stopes. The numerical results show the pillars in Sections 18, 22 and 24 are stable and the designed pillar size is suitable. The width of the ore body near Section 28 averages 20 m, failure occurs in the left stope, but the boundary pillars near Section 28 maintain good performance. The pillars in Sections 20 and 25 are unstable which are mainly affected by the Faults F8 and F18. The existence of faults alters the stress distribution, failure mode and water inrush pathway. This work provides a meaningful standard for boundary pillar and stope design in a mine as it transitions from an open pit to underground.展开更多
We investigate the behavior of the vacuum polarization of the gauge-boson Ⅱ and the wave-function renormalization factor of the fermion A in QEDs, using the coupled Dyson-Schwinger equations for the gauge-boson and f...We investigate the behavior of the vacuum polarization of the gauge-boson Ⅱ and the wave-function renormalization factor of the fermion A in QEDs, using the coupled Dyson-Schwinger equations for the gauge-boson and fermion propagator. Using several different ansatze for the fermion-gauge-boson vertex, we find that the wave-function renormalization factor .4 and especially the vacuum polarization Ⅱ have different behaviors in the dynamical chiral symmetry breaking phase and in the chiral symmetric phase and hence in the phenomenological applications of QED3 one should choose different forms of gauge-boson propagator for these two phases. We also find that when adopting a specific ansatze of the fermion-gauge-boson vertex （ansatze （3）） the vacuum polarization function equals its one-loop perturbative result in the chiral symmetric phase. This fact suggests that in QEDs the Wigner vacuum corresponds to the perturbative vacuum.展开更多
Nitrate,an oxidized product of NO x preserved in the polar ice cores,has often been used to estimate past changes of the atmospheric nitrogen cycle.A 102.65 m ice core drilled at DT-401(79°01'S,77°00'...Nitrate,an oxidized product of NO x preserved in the polar ice cores,has often been used to estimate past changes of the atmospheric nitrogen cycle.A 102.65 m ice core drilled at DT-401(79°01'S,77°00'E) in 1999 provides an opportunity to investigate the possible influencing factors for the nitrate budget in the eastern Antarctica.We studied the relationship between the δ18O(representing the temperature),accumulation rate,volcanic deposition and the astronomical factors(such as the solar activities,supernovae,etc.),and the nitrate variation along the whole duration(2680-year) of the ice core.Prominent impacts of the accumulation rate acting on the nitrate flux rather than the concentration were detected.However,no significant correlation was found between the δ18O and the nitrate deposition characteristics(concentration and the flux variations).Volcanic deposition can significantly affect the deposition of nitrate with a decreasing trend accompanied by the nss-SO42(volcanic signal) peak values.Impacts of the solar activities on the nitrate deposition can be detected at this site,and three prominent periodicities(16.6,24.0 and 102.0 yr) were found for the nitrate concentration variations.Six climatic events(Dalton Minimum,Maunder Minimum,Sporer Minimum,Wolf Minimum,Oort Minimum and Medieval Maximum) during the past 1150 years were observed with lower nitrate values for the foregoing five events and higher value for the last one.展开更多
文摘The push-pull framework provides a useful approach for examining the tourist motivation. This paper takes the world heritage-Huangshan Mountain as a sample. From the two different aspects of pull and push factors, the underlying features of visitors′ motives to Huangshan Mountain are analyzed with the help of factor analysis. As a result, five push factors and four pull factors are identified. Further analyses investigate differences in the push and pull factors among different socio-demographic subgroups with one-way ANOVA analysis. The result of the study affords us useful references for development, protection and marketing expansion of mountain resorts.
文摘A small number of copepod species have adapted to an existence in the extreme habitat of hypersaline water. 13 copepod species have been recorded in the hypersaline waters of Crimea （the largest peninsula in the Black Sea with over 50 hypersaline lakes）. Summarizing our own and literal_re data, the author concludes that the Crimean extreme environment is not an exception： copepod species dwell in hypersaline waters worldwide. There are at least 26 copepod species around the world living at salinity above 100; among them 12 species are found at salinity higher than 200. In the Crimea Cletocamptus retrogressus is found at salinity 360×10^-3 （with a density of 1 320 individuals/m^3） and Arctodiaptomus salinus at salinity 300×10^-3 （with a density of 343 individuals/m^3）. Those species are probably the most halotolerant copepod species in the world. High halotolerance of osmoconforming copepods may be explained by exoosmolyte consumption, mainly with food. High tolerance to many factors in adults, availability of resting stages, and an opportunity of long-distance transportation of resting stages by birds and/or winds are responsible for the wide geographic distribution of these halophilic copepods.
基金Supported by Graduate Innovative Projects in Jiangsu Province,No.1201270052Zhenjiang Science and Technology Program,No.SH2013032+2 种基金National Natural Science Foundation of China,No.81672348Six-Major-Peak-Talent Project of Jiangsu Province of China,No.2015-WSW-014the Scientific Research Fund for the Returned Overseas Chinese Scholars,State Ministry of Education,No.the 50th batch,2015
文摘AIM To investigate the role of interferon regulatory factor 5(IRF5) in reversing polarization of lung macrophages during severe acute pancreatitis(SAP) in vitro.METHODS A mouse SAP model was established by intraperitoneal(ip) injections of 20 μg/kg body weight caerulein. Pathological changes in the lung were observed by hematoxylin and eosin staining. Lung macrophages were isolated from bronchoalveolar lavage fluid. The quantity and purity of lung macrophages were detectedby fluorescence-activated cell sorting and evaluated by real-time polymerase chain reaction(RT-PCR). They were treated with IL-4/IRF5 specific siR NA(IRF5 siR NA) to reverse their polarization and were evaluated by detecting markers expression of M1/M2 using RTPCR.RESULTS SAP associated acute lung injury(ALI) was induced successfully by ip injections of caerulein, which was confirmed by histopathology. Lung macrophages expressed high levels of IRF5 as M1 phenotype during the early acute pancreatitis stages. Reduction of IRF5 expression by IRF5 siR NA reversed the action of macrophages from M1 to M2 phenotype in vitro. The expressions of M1 markers, including IRF5(S + IRF5 siR NA vs S + PBS, 0.013 ± 0.01 vs 0.054 ± 0.047, P < 0.01), TNF-α(S + IRF5 siR NA vs S + PBS, 0.0003 ± 0.0002 vs 0.019 ± 0.018, P < 0.001), iN OS(S + IRF5 siR NA vs S + PBS, 0.0003 ± 0.0002 vs 0.026 ± 0.018, P < 0.001) and IL-12(S + IRF5 si RNA vs S + PBS, 0.000005 ± 0.00004 vs 0.024 ± 0.016, P < 0.001), were decreased. In contrast, the expressions of M2 markers, including IL-10(S + IRF5 siR NA vs S + PBS, 0.060 ± 0.055 vs 0.0230 ± 0.018, P < 0.01) and Arg-1(S + IRF5 siR NA vs S + PBS, 0.910 ± 0.788 vs 0.0036 ± 0.0025, P < 0.001), were increased. IRF5 si RNA could reverse the lung macrophage polarization more effectively than IL-4.CONCLUSION Treatment with IRF5 siR NA can reverse the pancreatitisinduced activation of lung macrophages from M1 phenotype to M2 phenotype in SAP associated with ALI.
基金supported by the Special Climate Change Research Program of China Meteorological Ad-ministration (No.062700s010c01)the Special Scientific Research Fund of Meteorological Public Welfare Profession of China (No.201206024)
文摘This study focuses on examining the characteristics of climate factors and extreme climate events in Northeast China during 1961- 2010 by using daily data from 104 stations, including surface air temperature, precipitation, wind speed, sunshine duration, and snow depth. Results show that annual mean temperature increased at a significant rate of 0.35℃ per decade, most notably in the Lesser Khingan Mountains and in winter. Annual rainfall had no obvious linear trend, while rainy days had a significant decreasing trend. So, the rain intensity increased. High-temperature days had a weak increasing trend, and low-temperature days and cold wave showed significant decreasing trends with rates of 3.9 d per decade and -0.64 times per decade, respectively. Frequency and spatial scope of low-temperature hazard reduced significantly. Warm days and warm nights significantly increased at 1.0 and 2.4 d per decade, while cold days and cold nights decreased significantly at -1.8 and -4.1 d per decade, respectively. The nighttime warming rate was much higher than that for daytime, indicating that nighttime warming had a greater contribution to the overall warming trend than daytime warming. The annual mean wind speed, gale days, and sunshine duration had significant decreasing trends at rates of-0.21 m s-1 per decade, -4.0 d per decade and -43.3 h per decade, respectively. The snow cover onset dates postponed at a rate of 1.2 d per decade, and the snow cover end date advanced at 1.5 d per decade, which leads to shorter snow cover duration by -2.7 d per decade. Meanwhile, the maximum snow depth decreased at -0.52 cm per decade. In addition, the snow cover duration shows a higher correlation with precipitation than with temperature, which suggests that precipitation plays a more important role in maintaining snow cover duration than temperature.
基金supported by the program of China Polar Environment Investigation and Assessment(2011-2015)the National Nature Science Foundation of China (No. 41076132)
文摘Influencing factors, and variations and trends of Antarctic ozone hole in recent decades are analyzed, and sudden change processes of ozone at Zhongshan station and the effect of atmospheric dynamic processes on ozone changes are also discussed by using the satellite ozone data and the ground-measured ozone data at two Antarctic stations as well as the NCEP/NCAR reanalysis data. The results show that equivalent effective stratospheric chlorine (EESC) and stratospheric temperature are two important factors influencing the ozone hole. The column ozone at Zhongshan and Syowa stations is significantly related with EESC and stratospheric temperature, which means that even though the two stations are both located on the edge of the ozone hole, EESC and stratospheric temperature still played a very important role in column ozone changes, and mean while verifies that EESC is applicable on the coast of east Antarctic continent. Decadal changes in EESC are similar with those of the ozone hole, and inter-annual variations of ozone are closely related with stratospheric temperature. Based on the relation of EESC and ozone hole size, it can be projected that the ozone hole size will gradually reduce to the 1980's level from 2010 to around 2070. Of course there might exist many uncertainties in the projection, which therefore needs to be further studied.
基金supported by the Special Climate Change Research Program of China Meteorological Administration (No. CCSF-09-11, CCSF-09-03, CCSF2011-25, and CCSF201211)the Science and Technology Planning Project of Guangdong province (No.2011A030200021)
文摘Daily climate data at 110 stations during 1961-2010 were selected to examine the changing characteristics of climate factors and extreme climate events in South China. The annual mean surface air temperature has increased significantly by 0.16℃ per decade, most notably in the Pearl River Delta and in winter. The increase rate of the annual extreme minimum temperature (0.48℃ per decade) is over twice that of the annual extreme maximum temperature (0.20℃ per decade), and the increase of the mean temperature is mainly the result of the increase of the extreme minimum temperature. The increase rate of high-temperature days (1.1 d per decade) is close to the decrease rate of low-temperature days (-1.3 d per decade). The rainfall has not shown any significant trend, but the number of rainy days has decreased and the rain intensity has increased. The regional mean sunshine duration has a significant decreasing trend of -40.9 h per decade, and the number of hazy days has a significant increasing trend of 6.3 d per decade. The decrease of sunshine duration is mainly caused by the increase of total cloud, not by the increase of hazy days in South China. Both the regional mean pan evaporation and mean wind speed have significant decreasing trends of -65.9 mm per decade and -0.11 m s-1 per decade, respectively. The decrease of both sunshine duration and mean wind speed plays an important role in the decrease of pan evaporation. The number of landing tropical cyclones has an insignificant decreasing trend of -0.6 per decade, but their intensities show a weak increasing trend. The formation location of tropical cyclones landing in South China has converged towards 10-19°N, and the landing position has shown a northward trend. The date of the first landfall tropical cyclone postpones 1.8 d per decade, and the date of the last landfall advances 3.6 d per decade, resulting in reduction of the typhoon season by 5.4 d per decade.
文摘The coupling between system and reservoir is considered to be linear in the coordinates of the bath but nonlinear in the system's coordinate. A dissipative threshold is observed at finite temperatures due to nonlinear dissipation. The quantum decay rate of a metastable state including higher-order expanded terms of the coupling form function is proposed, which can be strongly decreased at finite temperatures when the quantum dissipative threshold is added to the saddle point of the potential.
基金Projects(1004025,51174044,50934006)supported by the National Natural Science FoundationProject(2011AA060400)supported by the National High Technique Research and Development Program of ChinaProject(Sklgduek1113)supported by Funds of the State Key Laboratory for Geomechanics&Deep Underground Engineering,Chinese University of Mining and Technology,China
文摘Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equilibrium method. The calculation results present that the safety factors of pillars in Sections 19, 20, 24, 28 are less than 1.3, and those of unstable sections are identified preliminarily. Further, a numerical investigation in Sections 18, 20, 22, 24, 25 and 28 implemented with numerical code RFPA20 is employed to further validate the pillar performance and the stability of stopes. The numerical results show the pillars in Sections 18, 22 and 24 are stable and the designed pillar size is suitable. The width of the ore body near Section 28 averages 20 m, failure occurs in the left stope, but the boundary pillars near Section 28 maintain good performance. The pillars in Sections 20 and 25 are unstable which are mainly affected by the Faults F8 and F18. The existence of faults alters the stress distribution, failure mode and water inrush pathway. This work provides a meaningful standard for boundary pillar and stope design in a mine as it transitions from an open pit to underground.
基金The project supported in part by National Natural Science Foundation of China under Grant Nos, 10175033 and 10135030 and the Research Fund for the Doctoral Program of Higher Education under Grant No. 20030284009
文摘We investigate the behavior of the vacuum polarization of the gauge-boson Ⅱ and the wave-function renormalization factor of the fermion A in QEDs, using the coupled Dyson-Schwinger equations for the gauge-boson and fermion propagator. Using several different ansatze for the fermion-gauge-boson vertex, we find that the wave-function renormalization factor .4 and especially the vacuum polarization Ⅱ have different behaviors in the dynamical chiral symmetry breaking phase and in the chiral symmetric phase and hence in the phenomenological applications of QED3 one should choose different forms of gauge-boson propagator for these two phases. We also find that when adopting a specific ansatze of the fermion-gauge-boson vertex （ansatze （3）） the vacuum polarization function equals its one-loop perturbative result in the chiral symmetric phase. This fact suggests that in QEDs the Wigner vacuum corresponds to the perturbative vacuum.
基金supported by the Foundation for Excellent Youth Scholars of CAREERI,CASthe National Natural Science Foundation of China(Grant Nos.40776002,40825017,41171052)+2 种基金the Hundred Talent Project of Chinese Academy of Sciencesthe Polar Scientific Explore Organizing Committee Foundation (Grant Nos.20080202&0852H71001)State Oceanic Administration of People's Republic of China Project on Climate in Polar Regions(Grant Nos.CHINARE2012-04-04 and CHINARE2012-02-02)
文摘Nitrate,an oxidized product of NO x preserved in the polar ice cores,has often been used to estimate past changes of the atmospheric nitrogen cycle.A 102.65 m ice core drilled at DT-401(79°01'S,77°00'E) in 1999 provides an opportunity to investigate the possible influencing factors for the nitrate budget in the eastern Antarctica.We studied the relationship between the δ18O(representing the temperature),accumulation rate,volcanic deposition and the astronomical factors(such as the solar activities,supernovae,etc.),and the nitrate variation along the whole duration(2680-year) of the ice core.Prominent impacts of the accumulation rate acting on the nitrate flux rather than the concentration were detected.However,no significant correlation was found between the δ18O and the nitrate deposition characteristics(concentration and the flux variations).Volcanic deposition can significantly affect the deposition of nitrate with a decreasing trend accompanied by the nss-SO42(volcanic signal) peak values.Impacts of the solar activities on the nitrate deposition can be detected at this site,and three prominent periodicities(16.6,24.0 and 102.0 yr) were found for the nitrate concentration variations.Six climatic events(Dalton Minimum,Maunder Minimum,Sporer Minimum,Wolf Minimum,Oort Minimum and Medieval Maximum) during the past 1150 years were observed with lower nitrate values for the foregoing five events and higher value for the last one.
