Rare earth elements(REEs) can record geologic and geochemical processes. We studied two granitic regolith profiles from different climatic zones in eastern Tibetan Plateau and found that(1)∑ RREEs ranged from119.65 t...Rare earth elements(REEs) can record geologic and geochemical processes. We studied two granitic regolith profiles from different climatic zones in eastern Tibetan Plateau and found that(1)∑ RREEs ranged from119.65 to 275.33 mg/kg in profile ND and5.11–474.55 mg/kg in profile GTC, with average values of205.79 and 161 mg/kg, respectively. ∑RREEs was higher in accumulation horizon and semi-regolith;(2) Influenced by climate, the fractionation of light and heavy REEs(LREEs and HREEs) varied during weathering. The ratio of LREEs/HREEs in pedosphere was higher than semi-regolith in tropical profile;(3) A negative Eu anomaly in both profiles was the result of bedrock weathering. A positive Ce anomaly was observed in all layers of profile ND, and only in the upper 100 cm of profile GTC. This indicates that redox conditions along the regolith profile varied considerably with climate.(4) Normalized by chondrite,LREEs accumulated much more than HREEs; REE distribution curves were right-leaning with a V-type Eu anomaly in both profiles.展开更多
In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected mon...In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected monthly over 1 year in the Min River, eastern Tibetan Plateau, and analyzed for trace element composition. The dissolved trace elements exhibited different relationships with increasing discharge compared with major elements.The elements analyzed can be divided into three groups according to their behavior in response to changing discharge:(1) elements that showed weak positive correlation with discharge, e.g. Cu, V, and Ba;(2) elements that exhibited weak negative correlation with discharge,including Rb, Sr, Pb, Sb, Zn, Cr, Cd, and U; and(3) elements that displayed no significant correlation with variation in discharge, e.g. Ti, Fe, Co, Ni, and As. Cu was strongly affected by anthropogenic activities and flushed into the river with increasing discharge. Ba has a strong solubility in the terrestrial environment, dissolved quickly,and was released into the river. The positive relationship between V concentration and discharge may be attributed to secondary reactions, such as precipitation and adsorption on oxides and aluminosilicate clays. Conservative behavior had an impact on the geochemical behavior of Sr and Rb across hydrologic variation. Pb, Zn, Sb, Cd, and Cr underwent a mild dilution effect connected with anthropogenic activities. The chemostatic behavior of U was regulated by carbonate dissolution and biological uptake.In addition, higher temperatures enhanced biotic activities,affecting the concentrations of Fe and Ni. The relationship between power law slopes and coefficient of variation for discharge and solute concentration suggests that concentrations of trace elements vary significantly with increasing discharge compared with major elements. Silicate mineral weathering had less effect on the fluvial solutes with increasing discharge. Mining activity may exert an additional control on concentration–discharge dynamics of anthropogenic trace elements.展开更多
The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameter...The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameters and buried depth on rectification moment. It is hoped that the reference value of rectification moment can be offered to operator, and theoretical foundation can be laid for future automatic rectification technology. The results show that the rectification moment and angle generally exhibit good linear behavior in clay layers with different soil parameters or buried depths, and then the concept of rectification coefficient, that is, the ratio of rectification angle to rectification moment, is proposed; different soil parameters and buried depths have different influences on rectification coefficient, in which elastic modulus has great influence but others have little influences; the simulations of rectification process are preformed in clay layers with different elastic modulus, and fitting results show that elastic modulus and rectification coefficient present the quadratic function relation.展开更多
In low permeability porous media which permeability anisotropy is ubiquitous,the percolation of fluid no longer follows linear Darcy’s Law.Oil-water two phase flow equation of low permeability reservoir with permeabi...In low permeability porous media which permeability anisotropy is ubiquitous,the percolation of fluid no longer follows linear Darcy’s Law.Oil-water two phase flow equation of low permeability reservoir with permeability anisotropy is established based on generalized Darcy’s law and starting pressure gradient,corresponding finite element program is developed and simulated based on the Finite Element Program Generator system (FEPG).The results show that energy-gathering exists in the flow event of flowing area front in low permeability reservoir.In the process of energy-gathering,the flow velocity changed little but increased rapidly as soon as the pressure gradient exceeded the starting pressure gradient of the reservoir,then gradually stabilized.The greater the starting pressure gradient is,the greater the near wellbore pressure drop is,the smaller the area influenced by the reservoir pressure changes caused by water injection and oil recovery.The greater the starting pressure gradient is,the lower the water saturation in same point of the reservoir is,the smaller the water flood swept area is.There will be more difficulties in water injection to the same extent.展开更多
This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instru...This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.展开更多
A quick and sensitive method was developed for the determination of 19 metal elements in Saffron,a traditional Chinese medicinal herb,collected from Tibet Autonomous Region and Henan Province of China using inductivel...A quick and sensitive method was developed for the determination of 19 metal elements in Saffron,a traditional Chinese medicinal herb,collected from Tibet Autonomous Region and Henan Province of China using inductively coupled plasma atomic emission spectrometry（ICP-AES）or inductively coupled plasma mass spectrometry（ICP-MS）.The determined 19 metals in Saffron include Ca,Fe,Mg,P,Sr,Al,Mn,Zn,V,Cr,Se,Co,Ni,Mo,and heavy metals As,Cu,Cd,Hg and Pb.For all the analyzed elements,the correlative coefficients of the calibration curves were no less than 0.9938.This proposed method was accurate,and the relative standard deviations of the measurements were lower than 5.25%.It can be used for the quality control of metal elements in Saffron.展开更多
基金funded by National Natural Science Foundation of China(41210004,41603018,41673124 and2013CB956401)ministry of water resources of People’s Republic of China(201401050)
文摘Rare earth elements(REEs) can record geologic and geochemical processes. We studied two granitic regolith profiles from different climatic zones in eastern Tibetan Plateau and found that(1)∑ RREEs ranged from119.65 to 275.33 mg/kg in profile ND and5.11–474.55 mg/kg in profile GTC, with average values of205.79 and 161 mg/kg, respectively. ∑RREEs was higher in accumulation horizon and semi-regolith;(2) Influenced by climate, the fractionation of light and heavy REEs(LREEs and HREEs) varied during weathering. The ratio of LREEs/HREEs in pedosphere was higher than semi-regolith in tropical profile;(3) A negative Eu anomaly in both profiles was the result of bedrock weathering. A positive Ce anomaly was observed in all layers of profile ND, and only in the upper 100 cm of profile GTC. This indicates that redox conditions along the regolith profile varied considerably with climate.(4) Normalized by chondrite,LREEs accumulated much more than HREEs; REE distribution curves were right-leaning with a V-type Eu anomaly in both profiles.
基金financially supported by the National Key R&D Program of China (Grant No. 2016YFA0601002)National Natural Science Foundation of China (Grant Nos. 41372376,41422303,41571130072,41561134017)
文摘In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected monthly over 1 year in the Min River, eastern Tibetan Plateau, and analyzed for trace element composition. The dissolved trace elements exhibited different relationships with increasing discharge compared with major elements.The elements analyzed can be divided into three groups according to their behavior in response to changing discharge:(1) elements that showed weak positive correlation with discharge, e.g. Cu, V, and Ba;(2) elements that exhibited weak negative correlation with discharge,including Rb, Sr, Pb, Sb, Zn, Cr, Cd, and U; and(3) elements that displayed no significant correlation with variation in discharge, e.g. Ti, Fe, Co, Ni, and As. Cu was strongly affected by anthropogenic activities and flushed into the river with increasing discharge. Ba has a strong solubility in the terrestrial environment, dissolved quickly,and was released into the river. The positive relationship between V concentration and discharge may be attributed to secondary reactions, such as precipitation and adsorption on oxides and aluminosilicate clays. Conservative behavior had an impact on the geochemical behavior of Sr and Rb across hydrologic variation. Pb, Zn, Sb, Cd, and Cr underwent a mild dilution effect connected with anthropogenic activities. The chemostatic behavior of U was regulated by carbonate dissolution and biological uptake.In addition, higher temperatures enhanced biotic activities,affecting the concentrations of Fe and Ni. The relationship between power law slopes and coefficient of variation for discharge and solute concentration suggests that concentrations of trace elements vary significantly with increasing discharge compared with major elements. Silicate mineral weathering had less effect on the fluvial solutes with increasing discharge. Mining activity may exert an additional control on concentration–discharge dynamics of anthropogenic trace elements.
基金Project(2007CB714006)supported by the National Basic Research Program of China
文摘The finite element method is used to simulate the rectification process of shield machine, to study the relationship between rectification moment and angle and to explore the influence laws of different soil parameters and buried depth on rectification moment. It is hoped that the reference value of rectification moment can be offered to operator, and theoretical foundation can be laid for future automatic rectification technology. The results show that the rectification moment and angle generally exhibit good linear behavior in clay layers with different soil parameters or buried depths, and then the concept of rectification coefficient, that is, the ratio of rectification angle to rectification moment, is proposed; different soil parameters and buried depths have different influences on rectification coefficient, in which elastic modulus has great influence but others have little influences; the simulations of rectification process are preformed in clay layers with different elastic modulus, and fitting results show that elastic modulus and rectification coefficient present the quadratic function relation.
文摘In low permeability porous media which permeability anisotropy is ubiquitous,the percolation of fluid no longer follows linear Darcy’s Law.Oil-water two phase flow equation of low permeability reservoir with permeability anisotropy is established based on generalized Darcy’s law and starting pressure gradient,corresponding finite element program is developed and simulated based on the Finite Element Program Generator system (FEPG).The results show that energy-gathering exists in the flow event of flowing area front in low permeability reservoir.In the process of energy-gathering,the flow velocity changed little but increased rapidly as soon as the pressure gradient exceeded the starting pressure gradient of the reservoir,then gradually stabilized.The greater the starting pressure gradient is,the greater the near wellbore pressure drop is,the smaller the area influenced by the reservoir pressure changes caused by water injection and oil recovery.The greater the starting pressure gradient is,the lower the water saturation in same point of the reservoir is,the smaller the water flood swept area is.There will be more difficulties in water injection to the same extent.
文摘This paper presents the results of determining trace elements and δ 13C, δ 18O in Gyraulus sibirica shell continuously preserved in Xingcuo Lake sediments in the recent 50 years. By coupling these indexes and instrumental meteorological data on its basin to determine the relations among them, we probed quantitatively the climatic signals recorded in Xingcuo Lake sediments. The results showed that gastropod shells in Xingcuo Lake were formed in warm seasons; that trace elements, and stable isotope in shells just recorded the climatic signals of the warm seasons instead of that of the whole year; that Mg/Ca ratio and δ 18O proxy had certain correlation with air temperature in warm seasons, when the δ 18O proxy was more sensitive; with the average ratio of them being 0.28×10 -3/℃ and the variation rate dδ 18O/dT being 1.64×10 -3/℃; that the Sr/Ca ratio and δ 13C proxy, especially Sr/Ca ratio, had close correlation; and that dSr/Ca/dP was -0.045/mm.
文摘A quick and sensitive method was developed for the determination of 19 metal elements in Saffron,a traditional Chinese medicinal herb,collected from Tibet Autonomous Region and Henan Province of China using inductively coupled plasma atomic emission spectrometry（ICP-AES）or inductively coupled plasma mass spectrometry（ICP-MS）.The determined 19 metals in Saffron include Ca,Fe,Mg,P,Sr,Al,Mn,Zn,V,Cr,Se,Co,Ni,Mo,and heavy metals As,Cu,Cd,Hg and Pb.For all the analyzed elements,the correlative coefficients of the calibration curves were no less than 0.9938.This proposed method was accurate,and the relative standard deviations of the measurements were lower than 5.25%.It can be used for the quality control of metal elements in Saffron.
