Determination of the Pore Water Velocity Using a Salt Tracer Combined with Self-Potential Measurements

The tracer technique is recommended as an effective tool in surveying abnormal seepage through lakes and dams. By injecting a tracer into a known upstream location and monitoring the appearance of the tracer in the downstream leak point, it is possible to determine the direction and the average water velocity of the preferential flow through the dam. The detailed result achieved depends on the number of samples and the sampling locations to analyze tracer concentration over time in the field. This study proposes to use noninvasive self-potential measurements to determine the location and time the salt tracer moves through the seepage zone. The connection between the potential signal according to the propagation of the NaCl salt tracer and the water velocity was demonstrated through an experiment on a sandbox model. Experimental results express a good agreement between the time to reach the maximum value of the potential variation and the salt concentration variation with the time that water comes to monitoring locations. The result indicates an ability to determine the pore water velocity of the seepage zone based on the recording of potential signals produced by a salt tracer movement. The salt tracer test using NaCl combined with self-potential measurements was then applied to survey a leaking earth dam in the Dong Nai river basin (Vietnam).

Evaluation of Erythrocyte Iron Incorporation in Beijing Prepubertal Children Using a Single Stable Isotope Tracer Method

Objective To analyze the rate of erythrocyte iron incorporation and provided guidance for the iron nutrition for prepubertal children.Methods Fifty-seven prepubertal children of Beijing were involved in this study and each subject was orally administered 3 mg of 57 Fe twice daily to obtain a total of 30 mg 57 Fe after a 5-d period. The stable isotope ratios in RBCs were determined in 14 th day, 28 th day, 60 th day, and 90 th day. The erythrocyte incorporation rate in children was calculated using the stable isotope ratios, blood volume and body iron mass.Results The percentage of erythrocyte 57 Fe incorporation increased starting 14 th day, reached a peak at 60 d(boys: 19.67% ± 0.56%, girls: 21.33% ± 0.59%) and then decreased. The erythrocyte incorporation rates of 57 Fe obtained for girls in 60 th day was significantly higher than those obtained for boys(P < 0.0001).Conclusions The oral administration of 57 Fe to children can be used to obtain erythrocyte iron incorporation within 90 d. Prepubertal girls should begin to increase the intake of iron and further studies should pay more attention to the iron status in prepubertal children.

Craniocerebral injury promotes the repair of peripheral nerve injury

The increase in neurotrophic factors after craniocerebral injury has been shown to promote fracture healing. Moreover, neurotrophic factors play a key role in the regeneration and repair of peripheral nerve. However, whether craniocerebral injury alters the repair of peripheral nerve injuries remains poorly understood. Rat injury models were established by transecting the left sciatic nerve and using a free-fall device to induce craniocerebral injury. Compared with sciat- ic nerve injury alone after 6-12 weeks, rats with combined sciatic and craniocerebral injuries showed decreased sciatic functional index, increased recovery of gastrocnemius muscle wet weight, recovery of sciatic nerve ganglia and corresponding spinal cord segment neuron mor- phologies, and increased numbers of horseradish peroxidase-labeled cells. These results indicate that craniocerebral injury promotes the repair of peripheral nerve injury.

Stability on the ^(109)Cd,^(65)Zn Complex with Humus Acids

The radioactive isotope tracer and ion exchange balanced method was used to study the stability of 109Cd, 65 Zn complexes with humus acids. In the 109Cd and 65 Zn single existing system with humic acids, the stability constants of the humic-109Cd(65Zn) complex compound was higher than the fulvic-109 Cd(65Zn) complex compound. The stability constant of the humic (fulvic) -65Zn was higher than that of the humic (ful-vic)-109Cd. In the 109Cd and 65 Zn coexisting system, the stability constant and the co-ordination number of the humic (fulvic)-65Zn complex obviously increased, but the stability constant and the co-ordination number of the humic (fulvic)-109Cd complex obviously decreased as compared with its respectively single existing system . The result showed that the humus matter with higher molecular weight could more effectively reduce plant availability of heavy metals than that with lower molecular weight in polluted soil by heavy metals. The humus matter could more effectively reduce plant availability of Zn than that of Cd. Application of humus-acid increased the harm of Cd and decreased the harm of Zn to plants in Cd-Zn coexisting system.

HYDRAULIC CHARACTERISTICS OF VERTICAL VORTEX AT HYDRAULIC INTAKES

The trace of vertical vortex flow at hydraulic intakes is of the shape of spiral lines, which was observed in the presented experiments with the tracer technique. It represents the fluid particles flow spirally from the water surface to the underwater and rotate around the vortex-axis multi-cycle. This process is similar to the movement of screw. To describe the multi-circle spiral characteristics under the axisymmetric condition, the vertical vortex would change not only in the radial direction but also in the axial direction. The improved formulae for three velocity components for the vertical vortex flow were deduced by using the method of separation of variables in this article. In the improved formulae, the velocity components are the functions of the radial and axial coordinates, so the multi-circle spiral flow of vertical vortex could be simulated. The calculated and measured results for the vertical vortex flow were compared and the causes of errors were analyzed.

Distribution and Fate of Anthropogenic Nitrogen in the Calamagrostis angustifolia Wetland Ecosystem of Sanjiang Plain, Northeast China

Wetlands are important for the protection of water quality of rivers and lakes, especially those adjacent to agricultural landscapes, by intercepting and removing nutrients in runoff. In this study, the ^15N tracer technique was applied to study the distribution and fate of anthropogenic nitrogen （^15N-fertilizer） in Calamagrostis angustifolia Kom wetland plant-soil microcosms to identify the main ecological effects of it. ^15NH4^15NO3 solution （14.93 mg N/L, 20.28 at.% ^15N） was added to each microcosm of the first group, which was approximate to the current nitrogen concentration （CNC） of farm drainage, and 29.86 mg NIL ^15NH4^15NO3 solution was added to another group, which was approximate to the double nitrogen concentration （DNC） of farm drainage, while no nitrogen （NN） was added to the third group. The results suggest that the input of anthropogenic nitrogen has positive effects on the biomass and total nitrogen content of plant, and the positive effects will be elevated as the increase of its input amount. The increase of ^15N-fertilizer can also elevate its amounts and proportions in plant nitrogen. Soil nitrogen is still the main source of plant nitrogen, but its proportion will be reduced as the increase of ^15 N-fertilizer. The study of the fate of ^15N-fertilizer indicates that, in CNC treatment, only a small proportion is water-dissolved （0,13 ± 0.20%）, a considerable proportion is soil-immobilized （17.02 ± 8.62%）, or plant-assimilated （23.70 ± 0.92%）, and most is lost by gaseous forms （59.15 ± 8.35%）. While in DNC treatment, about 0.09 ± 0.15% is water-dissolved, 15.33 ± 7.46% is soil-immobilized, 23.55±2.86% is plant-assimilated, and 61.01±5.59% is lost by gaseous forms. The double input of anthropogenic nitrogen can not elevate the proportions of plant-assimilation, soil-immobilization and water-dissolution, but it can enhance the gaseous losses.