The large-scale summer monsoon circulations of south Asia makes a strong impact on precipitation in the area of southwestern China including Qinghai-Tibetan Plateau and Yun-Gui Plateau.however,the monsoon is both spat...The large-scale summer monsoon circulations of south Asia makes a strong impact on precipitation in the area of southwestern China including Qinghai-Tibetan Plateau and Yun-Gui Plateau.however,the monsoon is both spatially and temporally complex and smaller-scale circulations are forced by a variety of local or regional orographic effects,local or regional land-atmosphere or展开更多
Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive ...Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According to the peat characteristics of uniform deposition, the tephra was dated at 2002-1976 a B.P. by way of linear interpolation, so the time of volcanic eruption was 15 B.C.-26 A.D. (the calibrated age). While the geochemical characteristics of tephra in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result, there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact of volcanism on climate change.展开更多
This study analyzed the concentrations and chemical forms of Zn,Cu,Pb,Sb,Cd and Mn in airborne particles,road dusts and soils collected along three expressways in Jiangxi Province,China,with different traffic densitie...This study analyzed the concentrations and chemical forms of Zn,Cu,Pb,Sb,Cd and Mn in airborne particles,road dusts and soils collected along three expressways in Jiangxi Province,China,with different traffic densities,and identified the levels and sources of heavy metal contamination.The concentrations of Zn,Cu,Pb,Sb,and Cd except Mn in airborne particles,road dusts and soils were all in direct proportion to traffic volume.Cd concentrations were low compared with other metals.For instance,the concentrations of Zn,Cu,Pb,Sb,Mn and Cd were 6.6,0.7,2.2,0.1,0.1 and 0.1μg·m-3in PM10along the Changjiu Expressway,792.8,241.4,248.3,9.6,340.5and 8.0 mg·kg-1in road dusts,and 201.1,143.2,59.5,9.5,338.9 and 2.3 mg·kg-1in soils,respectively,but in the case of the ratio of concentration to the environmental background value,most serious contamination was caused by Cd.The sources of the heavy metals were judged by comparisons of the chemical forms of the heavy metals in different environmental media.Pb and Mn in airborne particles were both derived from traffic;Pb in road dusts and soils resulted mainly from the use of leaded gasoline in the past;and Mn in road dusts and soils was derived from parent rocks.Zn,Cu,Sb and Cd in airborne particles,road dusts and soils were derived primarily from traffic,and differences in chemical forms of the heavy metals in different media were due to the interaction between heavy metals in airborne particles and organic matter and other surfaces in road dusts and soils.We also discussed the change of chemical forms of heavy metals in particles of different sizes and under different weather conditions.Bioavailability of heavy metals in airborne particles was much higher than that in road dusts and soils,especially Pb(0.676 in airborne particles,0.159 in road dusts and 0.095 in soils).展开更多
Beryllium-7 （^7Be） and lead-210 （^210pb） activities were measured from October 2002 to January 2004 at Waliguan Observatory （WO： 36.287°N, 100.898°E, 3816 m a.s.l （above sea level） in northwest China...Beryllium-7 （^7Be） and lead-210 （^210pb） activities were measured from October 2002 to January 2004 at Waliguan Observatory （WO： 36.287°N, 100.898°E, 3816 m a.s.l （above sea level） in northwest China. ^7Be and ^210pb activities are high with overall averages of 14.74-3.5 mBq m^-3 and 1.8±0.8 mBq m^-3 respectively. For both 7Be and ^210pb, there are significant short-term and seasonal variations with a commonly low value in summer （May-September） and a monthly maximum in April （for ^7Be） and in December （for ^210pb）. The ratio of ^7Be/^210pb showed a broad maximum extending from April to July, coinciding with a seasonal peak in surface ozone （O3）. The seasonal cycles of ^7Be and ^210pb activities were greatly influenced by precipitation and thermal dynamical conditions over the boundary layer, especially for ^210Pb. The vertical mixing process between the boundary layer and the aloft air modulates the variations of ^7Be and ^210pb at WO in summer. It is indicated that air mass had longer residence time and originated from higher altitudes at WO in the spring-summer time and the winter in 2003. During an event with extremely high weeklyaveraged ^7Be concentration （24.8 mBq m^-3） together with high O3 levels and low water mixing ratio, we found that air masses had been convectively transported a long distance to WO from high latitude source regions in central Asia, where significant subsiding motions were observed. In another case with the extreme ^210pb activity of 5.7 mBq m^-3 high CO2 level and specific humidity （in winter）, air masses had come from south China and north Indian regions where 222Rn activities were high. This study, using ^7Be and ^210pb as atmospheric tracers, has revealed that complex interactions of convective mixing from the upper troposphere and long-range transports exist at WO.展开更多
Silicene,silicon analogue to graphene which possesses a two-dimensional(2D)hexagonal lattice,has attracted increasing attention in the last few years due to predicted unique properties.However,silicon naturally posses...Silicene,silicon analogue to graphene which possesses a two-dimensional(2D)hexagonal lattice,has attracted increasing attention in the last few years due to predicted unique properties.However,silicon naturally possesses a three-dimensional(3D)diamond structure,so there seems to be not any natural solid phase of silicon similar to graphite.Here we report the synthesis of new silicene structure with a unique rectangular lattice by using a coherent electron beam to irradiate amorphous silicon nanofilm produced by pulsed laser deposition(PLD).Under the irradiation of coherent electron beam with proper kinetic energy,the surface layer of silicon nanofilm can be crystallized into silicene.The dynamic stability and the energy band properties of this new silicene structure are investigated by using first-principle calculations and density function theory(DFT)with the help of the observed crystalline structure and lattice constant.The new silicene structure has a real direct bandgap of 0.78 eV.Interestingly,the simulating calculation shows that the convex bond angle is 118°in the new silicene structure with rectangular lattices.The DFT simulations reveal that this new silicene structure has a Dirac-cone-like energy band.The experimental realization of silicene and the theoretically predicted properties shed light on the silicon material with potential applications in new devices.展开更多
Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using i...Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels （P ≤ 0.05） of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg^-1, respectively. These metals were continuously dispersed downstream from the tallings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg^-1, respectively, being significantly higher （P ≤ 0.05） as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.展开更多
Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern Guizhou. Two stages can be recognized during the process of in situ weathering of dolomiti...Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern Guizhou. Two stages can be recognized during the process of in situ weathering of dolomitite: the stage of sedentary accumulation of leaching residue of dolomitite and the stage of chemical weathering evolution of sedentary soil. Ni, Cr, Mo, W and Ti are the least mobile elements with reference to Al. The geochemical behavior of REE is similar to that observed in weathering of other types of rocks. Fractionation of REE is noticed during weathering, and the two layers of REE enrichments are thought to result from downward movement of the weathering front in response to changes in the environment. It is considered that the chemistry of the upper part of the profile, which was more intensively weathered, is representative of the mobile components of the upper curst at the time the dolomitite was formed, while the less weathered lower profile is chemically representative of the immobile constitution. Like glacial till and loess, the 'insoluble' materials in carbonate rocks originating from chemical sedimentation may also provide valuable information about the average chemical composition of the upper continental crust.展开更多
The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma ...The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma lattice structures induced by the nanosecond pulsed laser in the cavity may be similar to the Wigner crystal structure. It is interesting that the beautiful diffraction pattern could be observed in the plasma lattice structure. The radiation lifetime could be shortened to the nanosecond range throughout the entire spectral range and the relaxation time could be lengthened for higher emission efficiency in the Purcell cavity, which results in the fact that the plasmonic emission is stronger and its threshold is lower.展开更多
10Be/7Be is a stratospheric sensitive tracer.In this paper,measurements of 10Be/7Be and surface O3 from October 2005 to May 2006 at Mt.Waliguan (hereafter WLG,100.898°E,39.287°N,3810 m,a.s.l.),China global a...10Be/7Be is a stratospheric sensitive tracer.In this paper,measurements of 10Be/7Be and surface O3 from October 2005 to May 2006 at Mt.Waliguan (hereafter WLG,100.898°E,39.287°N,3810 m,a.s.l.),China global atmospheric watch (GAW) observatory,are introduced and used to investigate the stratosphere-troposphere transport (STT) and its impact on surface O3 on the Tibetan Plateau.The results show that the magnitude of STT is weak in winter,followed by strengthening from the end of winter to the middle of spring (from mid February to mid April) with large increases in 10Be,7Be,10Be/7Be and surface O3.At the end of spring (from the end of April to mid May in this paper),the STT weakened,and the continuous increase of surface O3 at WLG is produced by tropospheric photochemistry reactions.展开更多
The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004...The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004 are presented. With the establishment of the new datasets of DCCW （Differential Concentrations in Contiguous Weeks） of ^7Be,^210pb, and O3, CO2 （△^7Be, △^210pb, △O3, △CO2, respectively, the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by ^7Be and ^210pb being as independent tracers. The relations among △^7Be, △^210pb, and △O3, △CO2 are examined statistically and compared. The results indicate that with the DCCWs, the interferences with the tracing significance of ^7Be and ^210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced, and the weighting sources of O3 or CO2 variations are more pronounced. Basically, the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer （CBL） has an obvious input for CO2. The relation between △^210pb and △O3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter, and the relation of △^7Be and △CO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter. With the highly correlated relations between ^7Be and O3, a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG： the monthly averages of stratospheric O3 range from 6 ×10^-9 to 8 ×10^-9 （volume mixing ratio） in April and from June to August, and 2 ×10^-9 to 4 ×10^-9 in the remaining months. For the ultimate sources of the baseline concentration of surface 03, which consist of only stratospheric transport and tropospheric photochemistry production, the contribution from stratospheric transport is estimated to be about 20 ×10^-9 from May to July, and （12-15） ×10^-9 in the remaining months, and the total relative contribution rate is about 35% to 40%.展开更多
Tektite arouses great concern of the scientists in different fields, mainly because it is a synthesized material produced by impact between terrestrial material and extraterrestrial material, and the falling or formin...Tektite arouses great concern of the scientists in different fields, mainly because it is a synthesized material produced by impact between terrestrial material and extraterrestrial material, and the falling or forming process of tektite has never展开更多
The Bayan Obo REE-Fe ore deposit is the most famous super-large REE deposit in theworld.It has attracted much attention of many geologists.However,there still exist somedivergences in the genesis of the deposit,metall...The Bayan Obo REE-Fe ore deposit is the most famous super-large REE deposit in theworld.It has attracted much attention of many geologists.However,there still exist somedivergences in the genesis of the deposit,metallogenic epoch and the origin of metallogenicmaterials.Although many methods,for example,Sm-Nd,U-Pb,Rb-Sr,K-Ar have beenused to determine the metallogenic age,the measured values have great changeable ranges,from 100 to 2000Ma.This is because it is difficult to find out the minerals or展开更多
Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from Oc...Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan （WLG） site. The overall average WlRC mass concentration was （1183 ± 120）ng/m3 （n = 79）, while seasonal averages were 2081 ± 1707 （spring）, 454±205 （summer）, 650 ±411 （autumn）, and 1019 ± 703 （winter） ng/m3. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ13C PDB value （-25.3 ± 0.8）%0 determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion. No seasonal change in δ13C PDB was evident. The average percent Modern Carbon （pMC） for 14C in WIRC for winter and spring was （67.2 ± 7.7）% （n = 29）. Lower pMC values were associated with air masses trans- ported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.展开更多
文摘The large-scale summer monsoon circulations of south Asia makes a strong impact on precipitation in the area of southwestern China including Qinghai-Tibetan Plateau and Yun-Gui Plateau.however,the monsoon is both spatially and temporally complex and smaller-scale circulations are forced by a variety of local or regional orographic effects,local or regional land-atmosphere or
基金supported jointly by the National Natural Science Foundation of China (Grant Nos.4973310 and 40602031)the Open Foundation of the State Key Laboratory of Environmental Geochemistry (Grant No.SKLEG5043)
文摘Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According to the peat characteristics of uniform deposition, the tephra was dated at 2002-1976 a B.P. by way of linear interpolation, so the time of volcanic eruption was 15 B.C.-26 A.D. (the calibrated age). While the geochemical characteristics of tephra in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result, there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact of volcanism on climate change.
文摘This study analyzed the concentrations and chemical forms of Zn,Cu,Pb,Sb,Cd and Mn in airborne particles,road dusts and soils collected along three expressways in Jiangxi Province,China,with different traffic densities,and identified the levels and sources of heavy metal contamination.The concentrations of Zn,Cu,Pb,Sb,and Cd except Mn in airborne particles,road dusts and soils were all in direct proportion to traffic volume.Cd concentrations were low compared with other metals.For instance,the concentrations of Zn,Cu,Pb,Sb,Mn and Cd were 6.6,0.7,2.2,0.1,0.1 and 0.1μg·m-3in PM10along the Changjiu Expressway,792.8,241.4,248.3,9.6,340.5and 8.0 mg·kg-1in road dusts,and 201.1,143.2,59.5,9.5,338.9 and 2.3 mg·kg-1in soils,respectively,but in the case of the ratio of concentration to the environmental background value,most serious contamination was caused by Cd.The sources of the heavy metals were judged by comparisons of the chemical forms of the heavy metals in different environmental media.Pb and Mn in airborne particles were both derived from traffic;Pb in road dusts and soils resulted mainly from the use of leaded gasoline in the past;and Mn in road dusts and soils was derived from parent rocks.Zn,Cu,Sb and Cd in airborne particles,road dusts and soils were derived primarily from traffic,and differences in chemical forms of the heavy metals in different media were due to the interaction between heavy metals in airborne particles and organic matter and other surfaces in road dusts and soils.We also discussed the change of chemical forms of heavy metals in particles of different sizes and under different weather conditions.Bioavailability of heavy metals in airborne particles was much higher than that in road dusts and soils,especially Pb(0.676 in airborne particles,0.159 in road dusts and 0.095 in soils).
基金the National Science Foundation of China （Grant Nos. 40175032 , 40575013）.
文摘Beryllium-7 （^7Be） and lead-210 （^210pb） activities were measured from October 2002 to January 2004 at Waliguan Observatory （WO： 36.287°N, 100.898°E, 3816 m a.s.l （above sea level） in northwest China. ^7Be and ^210pb activities are high with overall averages of 14.74-3.5 mBq m^-3 and 1.8±0.8 mBq m^-3 respectively. For both 7Be and ^210pb, there are significant short-term and seasonal variations with a commonly low value in summer （May-September） and a monthly maximum in April （for ^7Be） and in December （for ^210pb）. The ratio of ^7Be/^210pb showed a broad maximum extending from April to July, coinciding with a seasonal peak in surface ozone （O3）. The seasonal cycles of ^7Be and ^210pb activities were greatly influenced by precipitation and thermal dynamical conditions over the boundary layer, especially for ^210Pb. The vertical mixing process between the boundary layer and the aloft air modulates the variations of ^7Be and ^210pb at WO in summer. It is indicated that air mass had longer residence time and originated from higher altitudes at WO in the spring-summer time and the winter in 2003. During an event with extremely high weeklyaveraged ^7Be concentration （24.8 mBq m^-3） together with high O3 levels and low water mixing ratio, we found that air masses had been convectively transported a long distance to WO from high latitude source regions in central Asia, where significant subsiding motions were observed. In another case with the extreme ^210pb activity of 5.7 mBq m^-3 high CO2 level and specific humidity （in winter）, air masses had come from south China and north Indian regions where 222Rn activities were high. This study, using ^7Be and ^210pb as atmospheric tracers, has revealed that complex interactions of convective mixing from the upper troposphere and long-range transports exist at WO.
基金the Science and Technology Program of Guizhou Province,China(Grant Nos.[2018]5781 and[2020]1Y022)the Open Project of State Key Laboratory of Surface Physics and Department of Physics,Fudan University,Shanghai,China(Grant No.KF201903)the National Natural Science Foundation of China(Grant No.11847084)。
文摘Silicene,silicon analogue to graphene which possesses a two-dimensional(2D)hexagonal lattice,has attracted increasing attention in the last few years due to predicted unique properties.However,silicon naturally possesses a three-dimensional(3D)diamond structure,so there seems to be not any natural solid phase of silicon similar to graphite.Here we report the synthesis of new silicene structure with a unique rectangular lattice by using a coherent electron beam to irradiate amorphous silicon nanofilm produced by pulsed laser deposition(PLD).Under the irradiation of coherent electron beam with proper kinetic energy,the surface layer of silicon nanofilm can be crystallized into silicene.The dynamic stability and the energy band properties of this new silicene structure are investigated by using first-principle calculations and density function theory(DFT)with the help of the observed crystalline structure and lattice constant.The new silicene structure has a real direct bandgap of 0.78 eV.Interestingly,the simulating calculation shows that the convex bond angle is 118°in the new silicene structure with rectangular lattices.The DFT simulations reveal that this new silicene structure has a Dirac-cone-like energy band.The experimental realization of silicene and the theoretically predicted properties shed light on the silicon material with potential applications in new devices.
基金Project supported by the Guangdong Environmental Protection Bureau of China (No.2001-27)Guangdong Provincial Department of Science and Technology,China (No.2004A30308002)State Key Laboratory of Environment Geochemistry,Chinese Academy of Sciences
文摘Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels （P ≤ 0.05） of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg^-1, respectively. These metals were continuously dispersed downstream from the tallings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg^-1, respectively, being significantly higher （P ≤ 0.05） as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.
文摘Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern Guizhou. Two stages can be recognized during the process of in situ weathering of dolomitite: the stage of sedentary accumulation of leaching residue of dolomitite and the stage of chemical weathering evolution of sedentary soil. Ni, Cr, Mo, W and Ti are the least mobile elements with reference to Al. The geochemical behavior of REE is similar to that observed in weathering of other types of rocks. Fractionation of REE is noticed during weathering, and the two layers of REE enrichments are thought to result from downward movement of the weathering front in response to changes in the environment. It is considered that the chemistry of the upper part of the profile, which was more intensively weathered, is representative of the mobile components of the upper curst at the time the dolomitite was formed, while the less weathered lower profile is chemically representative of the immobile constitution. Like glacial till and loess, the 'insoluble' materials in carbonate rocks originating from chemical sedimentation may also provide valuable information about the average chemical composition of the upper continental crust.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11264007 and 61465003)
文摘The lattice structure image of a plasma standing wave in a Purcell cavity of silicon is observed. The plasma wave produced by the pulsed laser could be used to fabricate the micro-nanostructure of silicon. The plasma lattice structures induced by the nanosecond pulsed laser in the cavity may be similar to the Wigner crystal structure. It is interesting that the beautiful diffraction pattern could be observed in the plasma lattice structure. The radiation lifetime could be shortened to the nanosecond range throughout the entire spectral range and the relaxation time could be lengthened for higher emission efficiency in the Purcell cavity, which results in the fact that the plasmonic emission is stronger and its threshold is lower.
基金supported by the National Science Foundation of China (40575013,40175032 and 40830102)
文摘10Be/7Be is a stratospheric sensitive tracer.In this paper,measurements of 10Be/7Be and surface O3 from October 2005 to May 2006 at Mt.Waliguan (hereafter WLG,100.898°E,39.287°N,3810 m,a.s.l.),China global atmospheric watch (GAW) observatory,are introduced and used to investigate the stratosphere-troposphere transport (STT) and its impact on surface O3 on the Tibetan Plateau.The results show that the magnitude of STT is weak in winter,followed by strengthening from the end of winter to the middle of spring (from mid February to mid April) with large increases in 10Be,7Be,10Be/7Be and surface O3.At the end of spring (from the end of April to mid May in this paper),the STT weakened,and the continuous increase of surface O3 at WLG is produced by tropospheric photochemistry reactions.
基金supported by National Natural Science Foundation of China (Grant Nos.40575013,40175032 and 40830102)
文摘The weekly averages of near-surface ^7Be, ^210pb, 03, and CO2 concentrations at the Global Atmospheric Watch Observatory, Mt. Waliguan （101.98°E, 36.287°N, 3810 m a.s.l.）, from October 2002 to January 2004 are presented. With the establishment of the new datasets of DCCW （Differential Concentrations in Contiguous Weeks） of ^7Be,^210pb, and O3, CO2 （△^7Be, △^210pb, △O3, △CO2, respectively, the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by ^7Be and ^210pb being as independent tracers. The relations among △^7Be, △^210pb, and △O3, △CO2 are examined statistically and compared. The results indicate that with the DCCWs, the interferences with the tracing significance of ^7Be and ^210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced, and the weighting sources of O3 or CO2 variations are more pronounced. Basically, the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer （CBL） has an obvious input for CO2. The relation between △^210pb and △O3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter, and the relation of △^7Be and △CO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter. With the highly correlated relations between ^7Be and O3, a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG： the monthly averages of stratospheric O3 range from 6 ×10^-9 to 8 ×10^-9 （volume mixing ratio） in April and from June to August, and 2 ×10^-9 to 4 ×10^-9 in the remaining months. For the ultimate sources of the baseline concentration of surface 03, which consist of only stratospheric transport and tropospheric photochemistry production, the contribution from stratospheric transport is estimated to be about 20 ×10^-9 from May to July, and （12-15） ×10^-9 in the remaining months, and the total relative contribution rate is about 35% to 40%.
文摘Tektite arouses great concern of the scientists in different fields, mainly because it is a synthesized material produced by impact between terrestrial material and extraterrestrial material, and the falling or forming process of tektite has never
基金Project supported by the National Natural Science Foundation of China.
文摘The Bayan Obo REE-Fe ore deposit is the most famous super-large REE deposit in theworld.It has attracted much attention of many geologists.However,there still exist somedivergences in the genesis of the deposit,metallogenic epoch and the origin of metallogenicmaterials.Although many methods,for example,Sm-Nd,U-Pb,Rb-Sr,K-Ar have beenused to determine the metallogenic age,the measured values have great changeable ranges,from 100 to 2000Ma.This is because it is difficult to find out the minerals or
基金supported by the National Natural Sciences Foundation of China(Grant Nos.411751154083010240575013 and 40175032)
文摘Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan （WLG） site. The overall average WlRC mass concentration was （1183 ± 120）ng/m3 （n = 79）, while seasonal averages were 2081 ± 1707 （spring）, 454±205 （summer）, 650 ±411 （autumn）, and 1019 ± 703 （winter） ng/m3. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ13C PDB value （-25.3 ± 0.8）%0 determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion. No seasonal change in δ13C PDB was evident. The average percent Modern Carbon （pMC） for 14C in WIRC for winter and spring was （67.2 ± 7.7）% （n = 29）. Lower pMC values were associated with air masses trans- ported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.
