The vertical distributions of trace metals and physicochemical parameters in water columns in Kigoma Bay and Kungwe Bay in eastern Lake Tanganyika, Tanzania, were studied. The Al, Ba, Ca, Co,K, Mg, Mn, Mo, Na, Sn, Sr,...The vertical distributions of trace metals and physicochemical parameters in water columns in Kigoma Bay and Kungwe Bay in eastern Lake Tanganyika, Tanzania, were studied. The Al, Ba, Ca, Co,K, Mg, Mn, Mo, Na, Sn, Sr, and V concentrations were low and varied very little with depth. The toxic heavy metal(As, Cr, Cu, Ni, Pb, and Zn) concentrations were relatively high in the surface water, and the Cu, Ni, Pb, and Zn concentrations decreased with depth. Principal component and cluster analyses indicated that the metals in the lake had three main sources. Al, Ba, Ca, Co, Cu, Cr, Mn, Sr, Sn, and V were found to be geogenic; As, Cr, Cu, Mo, Ni, Pb, Sn and Zn anthropogenic; and As, Ca, Co, Mg, and Na biogenic.Human health risk assessments were performed, and it was found that trace metals in the water at most of the sampling sites would cause no potential adverse ef fects or non-carcinogenic health risks through dermal contact or ingestion. However, trace metals in surface water in Kungwe Bay could have certain adverse ef fects on human health through the ingestion pathway(the total hazard quotient for ingestion(ΣHQi ng)was 1.75(a value >1 was de?ned as possibly indicating adverse ef fects). The Pb HQi ng for surface water in Kungwe Bay was 1.50 and contributed >80% of the ΣHQ_(ing_, implying that Pb pollution is a water quality and safety problem that needs to be carefully monitored and the potential sources identi?ed.展开更多
Laboratory batch sorption and column transport experiments were performed on heterogeneous alluvial soils with a wide range of physical characteristics from wells that are located in the region between Mogan Lake and ...Laboratory batch sorption and column transport experiments were performed on heterogeneous alluvial soils with a wide range of physical characteristics from wells that are located in the region between Mogan Lake and Eymir Lake,Glbasι,Ankara.The mean values for the Kd of Cu were found to be highest in clay(32550.350 L/kg) and lowest in loamy sand(18170.76 L/kg).The minimum and maximum sorption capacity values(mean values) for Zn were found to be in clay(10985.148 mg/kg) and in silty loam(8597.14 mg/kg) units,respectively.Similarly,the minimum and maximum values for Mn were found in loamy sand(4908.695 mg/kg) and clay(7587.391 mg/kg) units.The non-linear least-squares optimization code "CXTFIT" was used to determine transport parameter values by curve-fitting.The results of the column experiments demonstrate dispersivity values within the range of 0.024-1.13 cm for soil samples.展开更多
The process of rolling step-shaft was simulated with the help of the FEM(Finite-Element Model) software-DEFORM^(TM) 3D. The characteristics of metal flow in differentperiods were analyzed, and the curve of variety in ...The process of rolling step-shaft was simulated with the help of the FEM(Finite-Element Model) software-DEFORM^(TM) 3D. The characteristics of metal flow in differentperiods were analyzed, and the curve of variety in non-round area at different cross-sections of therolled piece, the curve of variety in bulge volume and the curve of variety in non-column volumewere obtained. On this base the method of tool design is worked out and validated by experiment.展开更多
The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative stu...The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.展开更多
There is no enough information about metal transport parameters in residual soil. These soils are generally structured and still there is no answer to what happens with the contaminant transport parameters when an aci...There is no enough information about metal transport parameters in residual soil. These soils are generally structured and still there is no answer to what happens with the contaminant transport parameters when an acid solution with metal percolates this material with different structure. The objective of this study was to determine the contaminant transport parameters for Cd, Ni, Cu and Zn metals in an acid multispecies solution to a residual soil from south Brazil with an undisturbed and remolded structure. Column tests were carried out to determine the kd, Rd, Dh transport parameters. It was possible conclude that the magnitude of the kd, Rd and Dh parameter did not vary significantly with the soil structure.展开更多
基金Supported by the Construction Plan for Overseas Scientific Education Base of the Chinese Academy of Sciences(No.SAJC201609)the National Natural Science Foundation of China(No.51409241)the National Key Research and Development Program of China(No.2016YFE0123300)
文摘The vertical distributions of trace metals and physicochemical parameters in water columns in Kigoma Bay and Kungwe Bay in eastern Lake Tanganyika, Tanzania, were studied. The Al, Ba, Ca, Co,K, Mg, Mn, Mo, Na, Sn, Sr, and V concentrations were low and varied very little with depth. The toxic heavy metal(As, Cr, Cu, Ni, Pb, and Zn) concentrations were relatively high in the surface water, and the Cu, Ni, Pb, and Zn concentrations decreased with depth. Principal component and cluster analyses indicated that the metals in the lake had three main sources. Al, Ba, Ca, Co, Cu, Cr, Mn, Sr, Sn, and V were found to be geogenic; As, Cr, Cu, Mo, Ni, Pb, Sn and Zn anthropogenic; and As, Ca, Co, Mg, and Na biogenic.Human health risk assessments were performed, and it was found that trace metals in the water at most of the sampling sites would cause no potential adverse ef fects or non-carcinogenic health risks through dermal contact or ingestion. However, trace metals in surface water in Kungwe Bay could have certain adverse ef fects on human health through the ingestion pathway(the total hazard quotient for ingestion(ΣHQi ng)was 1.75(a value >1 was de?ned as possibly indicating adverse ef fects). The Pb HQi ng for surface water in Kungwe Bay was 1.50 and contributed >80% of the ΣHQ_(ing_, implying that Pb pollution is a water quality and safety problem that needs to be carefully monitored and the potential sources identi?ed.
文摘Laboratory batch sorption and column transport experiments were performed on heterogeneous alluvial soils with a wide range of physical characteristics from wells that are located in the region between Mogan Lake and Eymir Lake,Glbasι,Ankara.The mean values for the Kd of Cu were found to be highest in clay(32550.350 L/kg) and lowest in loamy sand(18170.76 L/kg).The minimum and maximum sorption capacity values(mean values) for Zn were found to be in clay(10985.148 mg/kg) and in silty loam(8597.14 mg/kg) units,respectively.Similarly,the minimum and maximum values for Mn were found in loamy sand(4908.695 mg/kg) and clay(7587.391 mg/kg) units.The non-linear least-squares optimization code "CXTFIT" was used to determine transport parameter values by curve-fitting.The results of the column experiments demonstrate dispersivity values within the range of 0.024-1.13 cm for soil samples.
基金This work was financed by the National Nature Science Foundation of China (No. 50035010)
文摘The process of rolling step-shaft was simulated with the help of the FEM(Finite-Element Model) software-DEFORM^(TM) 3D. The characteristics of metal flow in differentperiods were analyzed, and the curve of variety in non-round area at different cross-sections of therolled piece, the curve of variety in bulge volume and the curve of variety in non-column volumewere obtained. On this base the method of tool design is worked out and validated by experiment.
文摘The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.
文摘There is no enough information about metal transport parameters in residual soil. These soils are generally structured and still there is no answer to what happens with the contaminant transport parameters when an acid solution with metal percolates this material with different structure. The objective of this study was to determine the contaminant transport parameters for Cd, Ni, Cu and Zn metals in an acid multispecies solution to a residual soil from south Brazil with an undisturbed and remolded structure. Column tests were carried out to determine the kd, Rd, Dh transport parameters. It was possible conclude that the magnitude of the kd, Rd and Dh parameter did not vary significantly with the soil structure.
