Rehabilitation(amendment and vegetation establishment)on bauxite residue is viewed as a promising strategy to stabilize the surface and initiate soil development.However,such approaches are inhibited by high pH,high e...Rehabilitation(amendment and vegetation establishment)on bauxite residue is viewed as a promising strategy to stabilize the surface and initiate soil development.However,such approaches are inhibited by high pH,high exchangeable sodium(ESP)and poor nutrient status.Amendment with gypsum is effective in improving residue physical and chemical properties and promoting seed establishment and growth.Application of organics(e.g.compost)can address nutrient deficiencies but supplemental fertilizer additions may be required.A series of germination bioassays were performed on residue to determine candidate species and optimum rehabilitation application rates.Subsequent field trials assessed establishment of grassland species Holcus lanatus and Trifolium pratense as well as physical and chemical properties of amended residue.Follow up monitoring over five years assessed elemental content in grassland and species dynamics.With co-application of the amendments several grassland species can grow on the residue.Over time other plant species can invade the restored area and fast growing nutrient demanding grasses are replaced.Scrub species can establish within a 5 Yr period and there is evidence of nutrient cycling.High pH,sodicity and nutrient deficiencies are the major limiting factors to establishing grassland on residue.Following restoration several plant species can grow on amended residue.展开更多
The processes involved in the major steps of successful revegetation of bauxite residues are examined.The first phase is the natural physical,chemical and microbial ripening of the profile.This involves allowing the p...The processes involved in the major steps of successful revegetation of bauxite residues are examined.The first phase is the natural physical,chemical and microbial ripening of the profile.This involves allowing the profile to drain,dry,shrink and crack to depth,leaching of soluble salts,alkalinity and Na down out of the surface layers,acidification by direct carbonation and natural seeding of tolerant vegetation with an accumulation of organic matter near the surface and an attendant development of an active microbial community.Following ripening,the surface layer can be tilled and gypsum and organic matter(e.g.manures,composts,biosolids)incorporated.These amendments result in a further decrease in pH,increase in Ca and other exchangeable cations,increased leaching of Na(with a reduction in exchangeable Na and ESP),improved physical properties,particularly aggregation,and a large increase in microbial activity.Other important considerations include the choice of suitable plant species tolerant to salinity/sodicity and local environmental conditions and the addition of balanced fertilizer applications.展开更多
Phosphate is widely used to immobilize cadmium(Cd)and lead(Pb)in soils through the insoluble metal phosphate precipitation.However,an increase in the phosphorus content of the environment can cause new pollution.In th...Phosphate is widely used to immobilize cadmium(Cd)and lead(Pb)in soils through the insoluble metal phosphate precipitation.However,an increase in the phosphorus content of the environment can cause new pollution.In this study,five slow-release phosphate amendments(SRPAs)were synthesized and their characteristics including BET,SEM,FTIR,swelling ratio,and thephosphorus release were determined.The results show that SRPA was a sphere with a network structure with a specific surface area of 5 to 7.18 m^(2)/g andcontained phosphate,hydroxyl,carboxyl and other functional groups.Among five SRPAs,S3 sample showed good performance for phosphate release.Phosphate release from SRPA was well fitted with Ritger-Peppas model with constant n between 0.45 and 0.85,indicating that the phosphate release was in accordance with non-Fickian diffusion.As compared with monocalcium phosphate(MCP),SRPA application led to a lower concentration of water-soluble phosphorus in the soil sample and higher remediation efficiencies of Cd and Pb.The remediation efficiencies of water-soluble Cd and Pb in soil with SRPA were 97.1%and 97.9%,respectively.The remediation efficiencies of bioavailable Cd and Pb were 71.85%and 76.47%,respectively.The results of Tessier extraction showed that the exchangeable and carbonatebound fractions of Cd and Pb in the soil sample after SRPA application significantly reduced,while the residual fraction increased,indicating the stability of heavy metals increased.展开更多
Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signal...Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.展开更多
基金Projects(41877551,41842020)supported by the National Natural Science Foundation of ChinaProject supported by the Science Foundation Ireland 17/CDA/4778
文摘Rehabilitation(amendment and vegetation establishment)on bauxite residue is viewed as a promising strategy to stabilize the surface and initiate soil development.However,such approaches are inhibited by high pH,high exchangeable sodium(ESP)and poor nutrient status.Amendment with gypsum is effective in improving residue physical and chemical properties and promoting seed establishment and growth.Application of organics(e.g.compost)can address nutrient deficiencies but supplemental fertilizer additions may be required.A series of germination bioassays were performed on residue to determine candidate species and optimum rehabilitation application rates.Subsequent field trials assessed establishment of grassland species Holcus lanatus and Trifolium pratense as well as physical and chemical properties of amended residue.Follow up monitoring over five years assessed elemental content in grassland and species dynamics.With co-application of the amendments several grassland species can grow on the residue.Over time other plant species can invade the restored area and fast growing nutrient demanding grasses are replaced.Scrub species can establish within a 5 Yr period and there is evidence of nutrient cycling.High pH,sodicity and nutrient deficiencies are the major limiting factors to establishing grassland on residue.Following restoration several plant species can grow on amended residue.
文摘The processes involved in the major steps of successful revegetation of bauxite residues are examined.The first phase is the natural physical,chemical and microbial ripening of the profile.This involves allowing the profile to drain,dry,shrink and crack to depth,leaching of soluble salts,alkalinity and Na down out of the surface layers,acidification by direct carbonation and natural seeding of tolerant vegetation with an accumulation of organic matter near the surface and an attendant development of an active microbial community.Following ripening,the surface layer can be tilled and gypsum and organic matter(e.g.manures,composts,biosolids)incorporated.These amendments result in a further decrease in pH,increase in Ca and other exchangeable cations,increased leaching of Na(with a reduction in exchangeable Na and ESP),improved physical properties,particularly aggregation,and a large increase in microbial activity.Other important considerations include the choice of suitable plant species tolerant to salinity/sodicity and local environmental conditions and the addition of balanced fertilizer applications.
基金Projects(2020YFC1808002,2019YFD1100502)supported by the National Key R&D Program of China。
文摘Phosphate is widely used to immobilize cadmium(Cd)and lead(Pb)in soils through the insoluble metal phosphate precipitation.However,an increase in the phosphorus content of the environment can cause new pollution.In this study,five slow-release phosphate amendments(SRPAs)were synthesized and their characteristics including BET,SEM,FTIR,swelling ratio,and thephosphorus release were determined.The results show that SRPA was a sphere with a network structure with a specific surface area of 5 to 7.18 m^(2)/g andcontained phosphate,hydroxyl,carboxyl and other functional groups.Among five SRPAs,S3 sample showed good performance for phosphate release.Phosphate release from SRPA was well fitted with Ritger-Peppas model with constant n between 0.45 and 0.85,indicating that the phosphate release was in accordance with non-Fickian diffusion.As compared with monocalcium phosphate(MCP),SRPA application led to a lower concentration of water-soluble phosphorus in the soil sample and higher remediation efficiencies of Cd and Pb.The remediation efficiencies of water-soluble Cd and Pb in soil with SRPA were 97.1%and 97.9%,respectively.The remediation efficiencies of bioavailable Cd and Pb were 71.85%and 76.47%,respectively.The results of Tessier extraction showed that the exchangeable and carbonatebound fractions of Cd and Pb in the soil sample after SRPA application significantly reduced,while the residual fraction increased,indicating the stability of heavy metals increased.
文摘Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.
