| Loessial soil was used to investigate the effect of plant and Arbuscular Mycorrhizal (AM) fungi on the horizontal and vertical migration of selenium (Se) in soil in Liudaogou watershed Shenmu County, Shaanxi Province, and discussed the effect mechanism of AM fungi and sail stress on Se and nutrient uptake. The transport of Se in loessial soil columns was studied using a miscible displacement technique to analyze the accuracy of fitting results by different fit methods and different convection-dispersion equation (CDE) models. The main results were shown as following:1. Proper Se can significantly promote the uptake the selenium and nutrient of plants from soil. While the plants with high levels of Se about 2 mg·kg-1, it may inhibit the nutrient uptake in plant. In hydroponics, plants can adapt to higher concentration range of Se, which was 20 mg·kg-1.2. Inoculation with Glomus constrictum (GC) and Glomus mosseae (GM) significantly increased the nitrogen, phosphorus and potassium contents of plants. Inoculation with GC increased Se uptake of plants, decreased the effect of different Se levels on nutrient uptake in plant. Inoculation with GC decreased Se uptake of plants,enhanced the effect of an adequate of Se level on nutrient uptake in plant,and reduced the effect of high levels of Se.3. Zea mays and Robinia pseudoacacia Lynn. (RPL) can reduce the vertical migration of Se in soil columns by immobilization of roots. Zea mays and RPL inoculation with GC reduced the vertical migration of Se by increasing Se content in soil of 0~12 cm depths. Zea mays inoculation with GM reduced the vertical migration of Se, RPL inoculation with GM enhanced the vertical migration.4. Zea mays inoculation with GC enhanced the uptake of Se, which lied in the soil 40 cm away from plant, but inoculation with GM reduced the uptake of Se. RPL inoculation with GC and GM had little influence of Se uptake. Zea mays inoculation with AM fungi reduced the horizontal migration, and the influence of GM was higher than GC. RPL inoculation with AM fungi had little influence on Se horizontal migration.5. Proper calcium salt, sodium salt and mixed salt may promote Se uptake of Zea mays and RPL. The types of salt had great influence on Se uptake of Zea mays, as the effect of sodium salt exceeded calcium salt and mixed salt. Types of salt had influence on Se uptake of RPL but a little difference between them. When salt stress in excess, Se content of plant could reduce with the increase of salt content, and Zea mays was more sensitive to salt concentration.6. Proper calcium salt, sodium salt and mixed salt may promote nitrogen, phosphorus, and potassium uptake of Zea mays, or nitrogen and phosphorus uptake of RPL. The mixed salt could restrain potassium uptake of RPL. Compare with single salt, the mixed salt enable plant nutrient uptake remained relatively stable.7. Inoculation with GC and GM decreased the inhibitory action of high salt levels on Se and nutrition uptake of plants. Inoculation with GC had higher effect on improving the salt tolerance of Zea mays, and GM was more conducive to improving the salt tolerance of RPL.8. The method of parameter estimation using CDE accurately defined the dispersion coefficient (D) and retardation factor (R) from the breakthrough curves (BTC) and modeled selenite transport through soil. The method without tracer was more accurate than the method with the tracer. STudio of ANalytical MODels (STANMOD) was a very flexible tool for approximate analysis of one dimensional solute transport problems in soil. D increased with the increase of influent concentration and average pore-water velocity. R increased with the increase of soil bulk density, while D was first increase and then decrease. D decreased with the increase of soil column height.9. Nonequilibrium two-region model was more suited in fitting the transport of selenite ion than equilibrium model. D was larger if the inflection point of the BTCs occurred earlier or the curve was closed to the y-axis, R was larger if the curve was more flat. |
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