As soil cation exchange capacity （CEC） is a vital indicator of soil quality and pollutant sequestration capacity,a study was conducted to evaluate cokriging of CEC with the principal components derived from soil phy...As soil cation exchange capacity （CEC） is a vital indicator of soil quality and pollutant sequestration capacity,a study was conducted to evaluate cokriging of CEC with the principal components derived from soil physico-chemical properties.In Qingdao,China,107 soil samples were collected.Soil CEC was estimated by using 86 soil samples for prediction and 21 soil samples for test.The first two principal components （PC1 and PC2） together explained 60.2% of the total variance of soil physico-chemical properties.The PC1 was highly correlated with CEC （r=0.76,P0.01）,whereas there was no significant correlation between CEC and PC2 （r=0.03）.The PC1 was then used as an auxiliary variable for the prediction of soil CEC.Mean error （ME） and root mean square error （RMSE） of kriging for the test dataset were-1.76 and 3.67 cmolc kg-1,and ME and RMSE of cokriging for the test dataset were-1.47 and 2.95 cmolc kg-1,respectively.The cross-validation R2 for the prediction dataset was 0.24 for kriging and 0.39 for cokriging.The results show that cokriging with PC1 is more reliable than kriging for spatial interpolation.In addition,principal components have the highest potential for cokriging predictions when the principal components have good correlations with the primary variables.展开更多
Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geosta...Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geostatistics were used to analyze the spatial variability of soil CEC in the tea plantation site on Mengding Mountain in Sichuan Province of China on two sampling scales. It was found that, （1） on the small scale, the soil CEC was intensively spatially correlative, the rate of nugget to sill was 18.84% and the spatially dependent range was 1 818 m, and structural factors were the main factors that affected the spatial variability of the soil CEC; （2） on the microscale, the soil CEC was also consumingly spatially dependent, and the rate of nugget to sill was 16.52%, the spatially dependent range was 311 m, and the main factors affecting the spatial variability were just the same as mentioned earlier. On the small scale, soil CEC had a stronger anisotropic structure on the slope aspect, and a weaker one on the lateral side. According to the ordinary Kriging method, the equivalence of soil CEC distributed along the lateral aspect of the slope from northeast to southwest, and the soil CEC reduced as the elevation went down. On the microscale, the anisotropic structure was different from that measured on the small scale. It had a stronger anisotropic structure on the aspect that was near the aspect of the slope, and a weaker one near the lateral aspect of the slope. The soil CEC distributed along the lateral aspect of the slope and some distributed in the form of plots. From the top to the bottom of the slope, the soil CEC increased initially, and then reduced, and finally increased.展开更多
Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was c...Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was carried out for different horizons. All samples were analyzed using two different methods to determine Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). Statistical analysis (T-test) was used in order to investigate the differences between soil samples for the studied locations. Significant differences appeared when compared the two methods for CEC determination at Gedaref area, Wad Medani and Nile flood plain and that appeared in evaluation of ESP at Nile flood plain and Shambat area. The results also revealed that, the developed method used in this study was more practical, simple and reliable for determination of CEC and ESP as the currently used in most soil laboratories. In addition, it will be safer than the other methods in some problematic soils. The adoption of this developed method is advisable because it is less time consuming as it omits the washing step. In contrast, the old method cannot be a good substitute in laboratories which have no possibility to determine sodium by using flame photometer. We conclude that when the developed method is used to determine CEC and ESP time will be saved, that fewer amounts of chemicals will be used and that accurate results will be achieved.展开更多
More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2...More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.展开更多
Current researches on the nutritive characteristics of fibrous feedstuff through determining the feedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehensively discrib...Current researches on the nutritive characteristics of fibrous feedstuff through determining the feedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehensively discribed. and the methods of determining CEC value and the correlation between CEC value and chemical compositions, pH value, and the effect of CEC value on the digestion kinetics in ruminants were also emphatically introduced. The results of research showed that the CEC values of different feedstuff are different, closely correlated with nitrogen and acid detergent fibre (ADF) and lignin (LIG) content of the feedstuff. At the same time, there are markedly effect of CEC value in diet on the nutrients flow of digesta in the digestive tract of ruminants, the degradation rate and digestibility of nutrients in the rumen.展开更多
Cation exchange capacity (CEC) is an important characteristic of zeolites, especially when they are used as adsorbents in the aqueous system. However, no international standard method exists for the determination of C...Cation exchange capacity (CEC) is an important characteristic of zeolites, especially when they are used as adsorbents in the aqueous system. However, no international standard method exists for the determination of CEC of zeolites. We determined CEC of Linde-type A and Na-P1 type zeolites at various pH (4 to 10) with a simple method, where Na+-saturated zeolites were prepared, and then various amounts of HCl were added. CEC was simply calculated by subtracting the amount of Na+ in the final supernatant from the content of Na+ of the Na+-saturated zeolites. CEC of the zeolites decreased with decreasing pH and with decreasing Na+ concentration of the final supernatant. The concentration of Na+ of the supernatant, CEC of the zeolites began to decrease at weakly alkaline or neutral pH, and that of the Linde-type A zeolite became about half at pH around 6. When CEC was plotted against pH-pNa;where pNa is negative logarithm of the activity of Na+;CEC of each zeolite was expressed by a curve. It indicates that the CEC or the amount of Na+ retention is univocally determined by the ratio of activities of Na+ and proton.展开更多
As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions...As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions modify organic carbon （SOC）, nitrogen （N） and phosphorus dynamics, bulk density and water-holding capacity and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil ex- changeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0-10, 10-20, and 20-30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium （Ca）, magnesium （Mg）, and potassium （K）, and cation exchange capacity （CEC） were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium （Na） neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0-10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly （P〈0.001） and positively correlated with SOC, total N, pH and electrical conductivity （EC）. Soil pH and SOC are regarded as the main factors influencing the variation in ex- changeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.展开更多
A novel stationary phase for weak cation exchange （WCX） chromatography was prepared by ＂grafting from＂ strategy. Surface initiated atom transfer radical polymerization （ATRP） of acrylic acid （AA） was conducted...A novel stationary phase for weak cation exchange （WCX） chromatography was prepared by ＂grafting from＂ strategy. Surface initiated atom transfer radical polymerization （ATRP） of acrylic acid （AA） was conducted in toluene medium, starting from the macromolecule initiators of poly（4-vinylbenzyl chloride-co-divinylbenzene） （PcMs/DvB） beads, The amounts of poly（acrylic acid） grafted chains with different ATRP formulations were calculated based on the elemental analyses. The poly（acrylic acid） grafted beads obtained with different ATRP formula- tions were tried as chromatographic packings in the separation of proteins by ion-exchange chromatography. The effect of the poly（acrylic acid） grafted chain lengths on PCMS/DVB beads for the separation of proteins was investigated in details. Simultaneously, characterization of the column was investigated as ion chromatographic stationary phase for the separation of inorganic cations. The results show that poly（acrylic acid） grafted columns had excellent performance for separation of proteins and inorganic cations. The highest of the dynamic capacity of the column was 35.55 mg/mL. The columns were provided with high column efficiency.展开更多
Surface modification of different functional molecules onto NaREF_(4)(RE=rare earth)upconversion nanoparticles(UCNPs)impart their multiple functionalities.Functional molecules can be loaded onto NaREF_(4) UCNPs throug...Surface modification of different functional molecules onto NaREF_(4)(RE=rare earth)upconversion nanoparticles(UCNPs)impart their multiple functionalities.Functional molecules can be loaded onto NaREF_(4) UCNPs through the formation of coordination bonds between the surface-exposed RE^(3+) ions and the appropriate chemical groups of functional molecules.The density of surface RE^(3+) ions directly determines the loading efficiency of Na REF4 UCNPs.However,NaREF_(4) is a binary cation system,rendering the surface-distributed Na;and RE^(3+) ions remains a mystery.Here,we develop an effective strategy to significantly enhance the density of surface RE^(3+) ions,thus maximizing the loading capacity of NaREF_(4) UCNPs.This strategy is based on a heterovalent cation exchange(HCE)reaction in the surface region in which Na^(+)ions are replaced by RE^(3+) ions.The density of surface ligands enhances from 3.6 to 8.8 molecules/nm^(2) after reaction,suggesting that the loading efficiency increases by approximately 150%.Benefiting from the improved loading capacity,we demonstrate such surface-RE-rich nanoparticles have the ability to offer higher colloidal stability and more desirable photodynamic therapy(PDT)efficacy.This work not only advances our understanding of cation exchange reactions in RE-based nanoparticles,but also provides significant value for considerable applications such as sensing,bioimaging,and therapy.展开更多
基金funded by the National Natural Science Foundation of China (40771095,40725010 and 41030746)the Water Conservancy Science and Technology Foundation of Qingdao City,China (2006003)
文摘As soil cation exchange capacity （CEC） is a vital indicator of soil quality and pollutant sequestration capacity,a study was conducted to evaluate cokriging of CEC with the principal components derived from soil physico-chemical properties.In Qingdao,China,107 soil samples were collected.Soil CEC was estimated by using 86 soil samples for prediction and 21 soil samples for test.The first two principal components （PC1 and PC2） together explained 60.2% of the total variance of soil physico-chemical properties.The PC1 was highly correlated with CEC （r=0.76,P0.01）,whereas there was no significant correlation between CEC and PC2 （r=0.03）.The PC1 was then used as an auxiliary variable for the prediction of soil CEC.Mean error （ME） and root mean square error （RMSE） of kriging for the test dataset were-1.76 and 3.67 cmolc kg-1,and ME and RMSE of cokriging for the test dataset were-1.47 and 2.95 cmolc kg-1,respectively.The cross-validation R2 for the prediction dataset was 0.24 for kriging and 0.39 for cokriging.The results show that cokriging with PC1 is more reliable than kriging for spatial interpolation.In addition,principal components have the highest potential for cokriging predictions when the principal components have good correlations with the primary variables.
文摘Studies on the spatial variability of the soil cation exchange capacity （CEC） were made to provide a theoretical basis for an ecological tea plantation and management of soil fertilizer in the tea plantation. Geostatistics were used to analyze the spatial variability of soil CEC in the tea plantation site on Mengding Mountain in Sichuan Province of China on two sampling scales. It was found that, （1） on the small scale, the soil CEC was intensively spatially correlative, the rate of nugget to sill was 18.84% and the spatially dependent range was 1 818 m, and structural factors were the main factors that affected the spatial variability of the soil CEC; （2） on the microscale, the soil CEC was also consumingly spatially dependent, and the rate of nugget to sill was 16.52%, the spatially dependent range was 311 m, and the main factors affecting the spatial variability were just the same as mentioned earlier. On the small scale, soil CEC had a stronger anisotropic structure on the slope aspect, and a weaker one on the lateral side. According to the ordinary Kriging method, the equivalence of soil CEC distributed along the lateral aspect of the slope from northeast to southwest, and the soil CEC reduced as the elevation went down. On the microscale, the anisotropic structure was different from that measured on the small scale. It had a stronger anisotropic structure on the aspect that was near the aspect of the slope, and a weaker one near the lateral aspect of the slope. The soil CEC distributed along the lateral aspect of the slope and some distributed in the form of plots. From the top to the bottom of the slope, the soil CEC increased initially, and then reduced, and finally increased.
文摘Twenty-six soil samples were collected from five soil profiles at different climatological and ecological regions in central Sudan. Soil profile was dug in each studied area and morphological profile description was carried out for different horizons. All samples were analyzed using two different methods to determine Cation Exchange Capacity (CEC) and exchangeable sodium percentage (ESP). Statistical analysis (T-test) was used in order to investigate the differences between soil samples for the studied locations. Significant differences appeared when compared the two methods for CEC determination at Gedaref area, Wad Medani and Nile flood plain and that appeared in evaluation of ESP at Nile flood plain and Shambat area. The results also revealed that, the developed method used in this study was more practical, simple and reliable for determination of CEC and ESP as the currently used in most soil laboratories. In addition, it will be safer than the other methods in some problematic soils. The adoption of this developed method is advisable because it is less time consuming as it omits the washing step. In contrast, the old method cannot be a good substitute in laboratories which have no possibility to determine sodium by using flame photometer. We conclude that when the developed method is used to determine CEC and ESP time will be saved, that fewer amounts of chemicals will be used and that accurate results will be achieved.
文摘More than 500 datasets from the literature have been used to evaluate the relationships of specific surface area (SSA),cation exchange capacity (CEC) and activity versus the liquid limit (LL).The correlations gave R^2 values ranging between 0.71 and 0.92.Independent data were also used to validate the correlations.Estimated SSA values slightly overestimate the measured SSA up to 100 m^2/g.Regarding the estimated CEC values,they overestimated the measured CEC values up to 20 meq/(100 g).A probabilistic approach was performed for the correlations of SSA,CEC and activity versus LL.The analysis shows that the relations of SSA,CEC and activity with LL are robust.Using the LL values,it is possible to assess other basic engineering properties of clays.
文摘Current researches on the nutritive characteristics of fibrous feedstuff through determining the feedstuff cation exchange capacity (CEC) to evaluate its nutritive value at home and abroad were comprehensively discribed. and the methods of determining CEC value and the correlation between CEC value and chemical compositions, pH value, and the effect of CEC value on the digestion kinetics in ruminants were also emphatically introduced. The results of research showed that the CEC values of different feedstuff are different, closely correlated with nitrogen and acid detergent fibre (ADF) and lignin (LIG) content of the feedstuff. At the same time, there are markedly effect of CEC value in diet on the nutrients flow of digesta in the digestive tract of ruminants, the degradation rate and digestibility of nutrients in the rumen.
文摘Cation exchange capacity (CEC) is an important characteristic of zeolites, especially when they are used as adsorbents in the aqueous system. However, no international standard method exists for the determination of CEC of zeolites. We determined CEC of Linde-type A and Na-P1 type zeolites at various pH (4 to 10) with a simple method, where Na+-saturated zeolites were prepared, and then various amounts of HCl were added. CEC was simply calculated by subtracting the amount of Na+ in the final supernatant from the content of Na+ of the Na+-saturated zeolites. CEC of the zeolites decreased with decreasing pH and with decreasing Na+ concentration of the final supernatant. The concentration of Na+ of the supernatant, CEC of the zeolites began to decrease at weakly alkaline or neutral pH, and that of the Linde-type A zeolite became about half at pH around 6. When CEC was plotted against pH-pNa;where pNa is negative logarithm of the activity of Na+;CEC of each zeolite was expressed by a curve. It indicates that the CEC or the amount of Na+ retention is univocally determined by the ratio of activities of Na+ and proton.
基金supported by the National Key Basic Research Program of China (2011CB403204)the Natural Science Foundation of China (31000200)
文摘As a pioneer leguminous shrub species for vegetation re-establishment, Caragana microphylla is widely distributed in the semi-fixed and fixed sandy lands of the Horqin region, North China. C. microphylla planta- tions modify organic carbon （SOC）, nitrogen （N） and phosphorus dynamics, bulk density and water-holding capacity and biological activities in soils, but little is known with regard to soil exchange properties. Variation in soil ex- changeable base cations was examined under C. microphylla plantations with an age sequence of 0, 5, 10, and 22 years in the Horqin Sandy Land, and at the depth of 0-10, 10-20, and 20-30 cm, respectively. C. microphylla has been planted on the non-vegetated sand dunes with similar physical-chemical soil properties. The results showed that exchangeable calcium （Ca）, magnesium （Mg）, and potassium （K）, and cation exchange capacity （CEC） were significantly increased, and Ca saturation tended to decrease, while Mg and K saturations were increased with the plantation years. No difference was observed for exchangeable sodium （Na） neither with plantation years nor at soil depths. Of all the base cations and soil layers, exchangeable K at the depth of 0-10 cm accumulated most quickly, and it increased by 1.76, 3.16, and 4.25 times, respectively after C. microphylla was planted for 5, 10, and 22 years. Exchangeable Ca, Mg, and K, and CEC were significantly （P〈0.001） and positively correlated with SOC, total N, pH and electrical conductivity （EC）. Soil pH and SOC are regarded as the main factors influencing the variation in ex- changeable cations, and the preferential absorption of cations by plants and different leaching rates of base cations that modify cation saturations under C. microphylla plantation. It is concluded that as a nitrogen-fixation species, C. microphylla plantation is beneficial to increasing exchangeable base cations and CEC in soils, and therefore can improve soil fertility and create favorable microenvironments for plants and creatures in the semi-arid sandy land ecosystems.
基金Project supported by the Foundation of the Ministery of Science and Technology of China （No. 2009CB626608） and the National Natural Science Foundation of China （No. 201065008）.
文摘A novel stationary phase for weak cation exchange （WCX） chromatography was prepared by ＂grafting from＂ strategy. Surface initiated atom transfer radical polymerization （ATRP） of acrylic acid （AA） was conducted in toluene medium, starting from the macromolecule initiators of poly（4-vinylbenzyl chloride-co-divinylbenzene） （PcMs/DvB） beads, The amounts of poly（acrylic acid） grafted chains with different ATRP formulations were calculated based on the elemental analyses. The poly（acrylic acid） grafted beads obtained with different ATRP formula- tions were tried as chromatographic packings in the separation of proteins by ion-exchange chromatography. The effect of the poly（acrylic acid） grafted chain lengths on PCMS/DVB beads for the separation of proteins was investigated in details. Simultaneously, characterization of the column was investigated as ion chromatographic stationary phase for the separation of inorganic cations. The results show that poly（acrylic acid） grafted columns had excellent performance for separation of proteins and inorganic cations. The highest of the dynamic capacity of the column was 35.55 mg/mL. The columns were provided with high column efficiency.
基金financially supported by the National Natural Science Foundation of China(Nos.61805083,31801968,and 51802281)。
文摘Surface modification of different functional molecules onto NaREF_(4)(RE=rare earth)upconversion nanoparticles(UCNPs)impart their multiple functionalities.Functional molecules can be loaded onto NaREF_(4) UCNPs through the formation of coordination bonds between the surface-exposed RE^(3+) ions and the appropriate chemical groups of functional molecules.The density of surface RE^(3+) ions directly determines the loading efficiency of Na REF4 UCNPs.However,NaREF_(4) is a binary cation system,rendering the surface-distributed Na;and RE^(3+) ions remains a mystery.Here,we develop an effective strategy to significantly enhance the density of surface RE^(3+) ions,thus maximizing the loading capacity of NaREF_(4) UCNPs.This strategy is based on a heterovalent cation exchange(HCE)reaction in the surface region in which Na^(+)ions are replaced by RE^(3+) ions.The density of surface ligands enhances from 3.6 to 8.8 molecules/nm^(2) after reaction,suggesting that the loading efficiency increases by approximately 150%.Benefiting from the improved loading capacity,we demonstrate such surface-RE-rich nanoparticles have the ability to offer higher colloidal stability and more desirable photodynamic therapy(PDT)efficacy.This work not only advances our understanding of cation exchange reactions in RE-based nanoparticles,but also provides significant value for considerable applications such as sensing,bioimaging,and therapy.
