The purpose of this study was to assess the effect of long-term cultivation and water erosion on the soil organic carbon （OC） in particle-size fractions. The study site is located at Nihegou Watershed in the Souther...The purpose of this study was to assess the effect of long-term cultivation and water erosion on the soil organic carbon （OC） in particle-size fractions. The study site is located at Nihegou Watershed in the Southern Loess Plateau, China. The soil at this site is loess with loose and silty structure, and contains macropores. The results showed that the OC concentrations in sediments and in the particle-size fractions of sediments were higher than those in soils and in the particle-size fractions of soils. The OC concentration was highest in the clay particles and was lowest in the sand particles. Clay particles possessed higher OC enrichment ability than silt and sand particles. The proportions of OC in the silt fractions of soil and sediment were the highest （mean value of 53.87% and 58.48%, respectively）, and the total proportion of OC in the clay and silt fractions accounted for 96% and 98% of the total OC in the soil and sediment, respectively. The loss of OC was highest in silt particles, with an average value of 0.16 Mg ha^-1 y^-1, and was lowest in the sand （0.003 Mg ha^-1 y^-l）. This result suggests that the fine particle-size fraction in the removed sediment may be an important indicator to assess soil OC losses.展开更多
A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. T...A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.展开更多
Biological column leaching of Ni from low-grade Ni ore was studied,and the effects of ore particle size on leaching rate were investigated.The Ni ore with an average Ni content of 0.23%was crushed into four different ...Biological column leaching of Ni from low-grade Ni ore was studied,and the effects of ore particle size on leaching rate were investigated.The Ni ore with an average Ni content of 0.23%was crushed into four different particle size fractions:>10 mm,5−10 mm,2−5 mm and<2 mm.The main strain components at the genus level were acidithiobacillus(53.11%),leptospirillum(43.52%),and acidiphilium(3.37%).The leaching tests were carried out at pH 2.0 and~23℃.The Ni leaching rates from ores with particle sizes>10 mm(bioleaching),5–10 mm(acid leaching),5–10 mm(bioleaching),and 2–5 mm(bioleaching)were 23.76%,22.15%,32.42%and 54.17%,respectively,after 180 d of bioleaching.The ore particle size changed after leaching,compared with the original ore size,the proportion of the same size of 2−5 mm ore decreased to 44.64%.Ore with particle size of 2–5 mm was most suitable for column bioleaching,and effective Ni extraction was achieved with appropriate control of ore granularity.展开更多
Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving i...Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.展开更多
Micro-filtration membrane （1.2 μm）, hyper-filtration membrane （0.45 μm） and nano-filtration membrane （1000 Dalton） were used to characterize the particle size distribution of the organic matters in effluent le...Micro-filtration membrane （1.2 μm）, hyper-filtration membrane （0.45 μm） and nano-filtration membrane （1000 Dalton） were used to characterize the particle size distribution of the organic matters in effluent leachate treated by the aged-refuse-bioreactor（ARB） installed at Laogang Refuse Landfill, Shanghai. The results showed that the particle size distribution of the treated fresh and aged leachate using the ARB were quite consistent. The organic matter with particle size below 1000 Dalton accounted for about 90%, balanced with the suspended （〉1.2 μm） and colloidal （1000 Dalton-l.2μm） matters. Hence, it is proposed that coagulation, nano-filtration and electrically chemical oxidation may be not applicable for the advanced treatment for the effluents to reach the discharge standard limit value defined in Chinese national Standard for Pollution Control on the Landfill Site of Municipal Solid Wastes （GB16889-2008）, CODCr〈100 mg/L. Aged refuse bioreactor combined reverse osmosis was suggested as an economically and technically feasible technology to treat sanitary landfill leachate.展开更多
Microbe-based cement has been widely reported in recent literatures. It is a new method of consolidating loose fine particles, which relies on the bacterially induced formation of a compatible carbonate precipitation ...Microbe-based cement has been widely reported in recent literatures. It is a new method of consolidating loose fine particles, which relies on the bacterially induced formation of a compatible carbonate precipitation around individual particles and at particle-particle contacts. Materials and cementation procedure are two major factors that influence the cementation performance of microbe-based cement. Besides, there are some other factors related to the performance, such as pH, temperature, metabolism activity, the flushed times of bacterial solution, concentration of substrate and calcium ion, etc., which affect consolidation function. The assessment methods for cementation process are carried out by various techniques. The performance of consolidation loose grains based on microbe-based cement is tested with the help of experiment. In this paper a review is presented on the cementation mechanism of microbe-based cement, techniques utilized to monitor cementation process, the consolidated performance by microbe-based cement and bond factors.展开更多
Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nut...Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field experiments.The results showed that there was a significant size decrease of soil particles in the rhizosheath.Meanwhile,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of maize.The contents of Fe and Mn were also differentially altered in the rhizosheath.Rhizosheath development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental period.The formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient availability.The subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.展开更多
Neuronal toxic pollutants in environment possess hazards to human health. It is essential to determine the causative neuronal toxicants in environmental samples. In the present study, viability of primary cultured cer...Neuronal toxic pollutants in environment possess hazards to human health. It is essential to determine the causative neuronal toxicants in environmental samples. In the present study, viability of primary cultured cerebellar granule neurons (CGNs), combined with sample extraction, chemical fractionation and identification, was applied for screening acid-resistant neuronal toxic substances in environmental samples. River sediments and agricultural soils along the river near a brominated flame retardant (BFR) manufacturing plant in South China were collected to screen the key neuronal toxicants. The results indicated that the manufacturing plant was a source of neuronal toxicity risks. In the sediment and soil near the plant, one of the causative toxicants was identified as tris-(2,3-dibromopropyl) isocyanurate (TBC) using HPLC-MS/MS. In addition, an unknown chemical possibly causing significant neuronal toxicity was isolated from all the soil samples in the region.展开更多
基金supported by the grants from President Foundation of Northwest A & F University, China
文摘The purpose of this study was to assess the effect of long-term cultivation and water erosion on the soil organic carbon （OC） in particle-size fractions. The study site is located at Nihegou Watershed in the Southern Loess Plateau, China. The soil at this site is loess with loose and silty structure, and contains macropores. The results showed that the OC concentrations in sediments and in the particle-size fractions of sediments were higher than those in soils and in the particle-size fractions of soils. The OC concentration was highest in the clay particles and was lowest in the sand particles. Clay particles possessed higher OC enrichment ability than silt and sand particles. The proportions of OC in the silt fractions of soil and sediment were the highest （mean value of 53.87% and 58.48%, respectively）, and the total proportion of OC in the clay and silt fractions accounted for 96% and 98% of the total OC in the soil and sediment, respectively. The loss of OC was highest in silt particles, with an average value of 0.16 Mg ha^-1 y^-1, and was lowest in the sand （0.003 Mg ha^-1 y^-l）. This result suggests that the fine particle-size fraction in the removed sediment may be an important indicator to assess soil OC losses.
基金Supported by the 985 Foundation of Central University for Nationalities（CUN985-3-3） the National Natural Science Foundation of China（90305011）
文摘A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.
基金Project(U1608254)supported by the Special Fund for the National Natural Science Foundation of ChinaProjects(ZJKY2017(B)KFJJ01,ZJKY2017(B)KFJJ02)supported by the Zijin Mining Group Co.,Ltd.,China。
文摘Biological column leaching of Ni from low-grade Ni ore was studied,and the effects of ore particle size on leaching rate were investigated.The Ni ore with an average Ni content of 0.23%was crushed into four different particle size fractions:>10 mm,5−10 mm,2−5 mm and<2 mm.The main strain components at the genus level were acidithiobacillus(53.11%),leptospirillum(43.52%),and acidiphilium(3.37%).The leaching tests were carried out at pH 2.0 and~23℃.The Ni leaching rates from ores with particle sizes>10 mm(bioleaching),5–10 mm(acid leaching),5–10 mm(bioleaching),and 2–5 mm(bioleaching)were 23.76%,22.15%,32.42%and 54.17%,respectively,after 180 d of bioleaching.The ore particle size changed after leaching,compared with the original ore size,the proportion of the same size of 2−5 mm ore decreased to 44.64%.Ore with particle size of 2–5 mm was most suitable for column bioleaching,and effective Ni extraction was achieved with appropriate control of ore granularity.
基金Projects(50704030) supported by the National Natural Science Foundation of ChinaProject(KGCX2-YW-321-2) supported by the Knowledge Innovation Program of the Chinese Academy of Sciences
文摘Gibbsite is the usual precipitation product from alumina refineries with either Bayer or sintering process.However,the advantage of boehmite precipitation over gibbsite precipitation is the significant energy saving in the subsequent calcination step.The current investigation takes a pragmatic approach to measure precipitation ratios,determine product phase,morphology and particle size distribution,and assess the impacts and adjustment capability of main parameters such as seed,temperature,ethanol medium,and supersaturation on the precipitation kinetics and alumina hydrate type during co-precipitation process.The results clarify that gibbsite and boehmite both can be precipitated from supersaturated sodium aluminate solutions simultaneously,and the competitive formation between Al(OH)3 and γ-AlOOH determines the main precipitate phases from pregnant liquor.Boehmite seeds,high temperature and ethanol addition can promote the boehmite precipitation and improve the mass fraction of boehmite in products.Co-precipitation changes the multimodal distribution of seeds to a normal and well distribution of products,and the particle size is more than several times that of seeds.
基金Acknowledgments： This work was financially supported by Science and Technology Support Plan of The Ministry of Science and Technology of People＇s Republic of China （No. 2006BAC02A19） China National Natural Science Foundation with Grant （No. 20177014）.
文摘Micro-filtration membrane （1.2 μm）, hyper-filtration membrane （0.45 μm） and nano-filtration membrane （1000 Dalton） were used to characterize the particle size distribution of the organic matters in effluent leachate treated by the aged-refuse-bioreactor（ARB） installed at Laogang Refuse Landfill, Shanghai. The results showed that the particle size distribution of the treated fresh and aged leachate using the ARB were quite consistent. The organic matter with particle size below 1000 Dalton accounted for about 90%, balanced with the suspended （〉1.2 μm） and colloidal （1000 Dalton-l.2μm） matters. Hence, it is proposed that coagulation, nano-filtration and electrically chemical oxidation may be not applicable for the advanced treatment for the effluents to reach the discharge standard limit value defined in Chinese national Standard for Pollution Control on the Landfill Site of Municipal Solid Wastes （GB16889-2008）, CODCr〈100 mg/L. Aged refuse bioreactor combined reverse osmosis was suggested as an economically and technically feasible technology to treat sanitary landfill leachate.
基金supported by the National Natural Science Foundation of China (Grant No. 51072035)
文摘Microbe-based cement has been widely reported in recent literatures. It is a new method of consolidating loose fine particles, which relies on the bacterially induced formation of a compatible carbonate precipitation around individual particles and at particle-particle contacts. Materials and cementation procedure are two major factors that influence the cementation performance of microbe-based cement. Besides, there are some other factors related to the performance, such as pH, temperature, metabolism activity, the flushed times of bacterial solution, concentration of substrate and calcium ion, etc., which affect consolidation function. The assessment methods for cementation process are carried out by various techniques. The performance of consolidation loose grains based on microbe-based cement is tested with the help of experiment. In this paper a review is presented on the cementation mechanism of microbe-based cement, techniques utilized to monitor cementation process, the consolidated performance by microbe-based cement and bond factors.
基金Supported by the National Natural Science Foundation of China (No. 30671237),the Innovative Group Grant of the National Natural Science Foundation of China (No. 30821003)the National Basic Research Program(973 Program) of China (No. 2007CB109302)
文摘Root exudates,microorganism colonization and soil aggregates together form the rhizosheath,a special cylinder of micro-ecosystem adhering to the root surface.To study how the rhizosheath affects soil structure and nutrient distribution,we analyzed the impact of maize rhizosheath on soil particle size and nutrient availability in pot and field experiments.The results showed that there was a significant size decrease of soil particles in the rhizosheath.Meanwhile,the soil mineral nitrogen in the rhizosheath was significantly higher than that in the rhizosphere or bulk soil at tasseling and maturity stages of maize.The contents of Fe and Mn were also differentially altered in the rhizosheath.Rhizosheath development,indicated by a dry weight ratio of rhizosheath soil to the root,was relatively independent of root development during the whole experimental period.The formation of maize rhizosheath contributed to the modulation of soil particle size and nutrient availability.The subtle local changes of soil physical and chemical properties may have profound influence on soil formation,rhizospheric ecosystem initiation,and mineral nutrient mobilization over the long history of plant evolution and domestication.
基金supported by the National Basic Research Program of China (973 Program 2009CB421605)the National Natural Science Foundation of China (20890111, 20921063 & 20931160427)the Ministry of Science and Technology of China (2008IM041300)
文摘Neuronal toxic pollutants in environment possess hazards to human health. It is essential to determine the causative neuronal toxicants in environmental samples. In the present study, viability of primary cultured cerebellar granule neurons (CGNs), combined with sample extraction, chemical fractionation and identification, was applied for screening acid-resistant neuronal toxic substances in environmental samples. River sediments and agricultural soils along the river near a brominated flame retardant (BFR) manufacturing plant in South China were collected to screen the key neuronal toxicants. The results indicated that the manufacturing plant was a source of neuronal toxicity risks. In the sediment and soil near the plant, one of the causative toxicants was identified as tris-(2,3-dibromopropyl) isocyanurate (TBC) using HPLC-MS/MS. In addition, an unknown chemical possibly causing significant neuronal toxicity was isolated from all the soil samples in the region.
