长期不同管理方式土壤和磷对硒吸附解吸的影响

发布时间：2018-06-02 22:28

本文选题：土壤 + 硒　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：硒(Se)是人类所必需的微量元素之一,人类摄取硒的主要途径是通过植物摄入,从土壤进入到植物体内的硒的数量会直接影响到人类对其的摄入量。长期不同的施肥管理措施会影响土壤有机质等性质的不同,土壤中的有机质对硒有一定的固定和释放作用,而究竟有机质的含量对硒吸附的影响以及其他竞争离子对土壤吸附硒的影响尚不明了。本研究通过批量试验的方式,探讨了2种不同土地利用方式和5种长期不同施肥方式的土壤对硒吸附解吸的影响,研究了磷酸盐对土壤硒吸附解吸的影响,旨在为外源硒盐施入土壤后有效性的评价提供理论依据。主要得到以下结果:1不同管理方式土壤对硒的吸附有显著影响。随着时间的增加,7种土壤对硒的吸附均是一个先快后慢的过程,在8 h达到吸附平衡。其中未种植作物处理土壤的吸附量(撂荒、休闲)显著高于其他5种种植作物的土壤(撂荒休闲);各不同施肥处理土壤对亚硒酸盐的吸附能力排序为:NPKCKSNPKM2NPKM1NPK,对硒酸盐的吸附能力排序为:SNPKNPKM2NPKM1NPKCK;两种除有机质含量差异较大而其余理化性质相似的土壤M1NPK与M2NPK对硒的吸附量均表现为M2NPK处理土壤的吸附量高于M1NPK处理土壤。同一土壤对四价硒的吸附量约为对六价硒吸附量的2.83倍。二级动力学是描述土壤对硒吸附的动力学特征的较好的模型(四价硒R20.982;六价硒R20.981)。Langmiur模型对等温线的拟合较好(R20.991)。七种土壤的分配系数(Kd值)均随着硒溶液初始浓度的升高而降低,无耕作的土壤Kd值明显高于种植作物的土壤。不同土壤的解吸率随硒溶液初始浓度增高而增高,有机质含量高的土壤解吸率相对低,表现出了对硒的固定作用。2.磷酸根对土壤吸附硒有不同的影响。随着竞争离子磷酸根的加入以及浓度的梯度变化,不同土壤对亚硒酸盐与硒酸盐的吸附不同。由于土壤对磷酸根和硒的吸附存在竞争作用,磷酸根离子的存在明显减少了土壤对亚硒酸盐以及硒酸盐的吸附量。由于磷酸根离子结合能较强,占据了土壤表面的专性吸附位点,导致土壤对四价硒的吸附量随磷酸根离子浓度的增大逐渐变小,而导致对六价硒的吸附量有些许的上升。M2NPK处理的吸附量均高于M1NPK处理。亚硒酸盐浓度恒定,土壤的Kd值随磷酸根浓度增加而减小,且随硒溶液浓度的增加逐渐减小;硒酸盐浓度恒定,土壤的Kd值随磷酸根浓度的增加而增加。土壤对亚硒酸盐的解吸率随磷酸根浓度的增加而增加,而对硒酸盐的解吸率却随之下降。总之,长期不同管理措施土壤对硒的吸附-解吸作用产生了明显的影响,有机质含量高可起到固定硒的作用;磷酸根离子对土壤对硒的吸附与土壤中硒的价态有关,在硒的生物强化中应该综合考虑。
[Abstract]:Selenium Seis is one of the essential trace elements for human beings. The main way for human to ingest selenium is through plant intake. The amount of selenium from soil to plant will directly affect the intake of selenium from soil to plant. Long-term fertilization and management measures will affect the properties of soil organic matter, such as soil organic matter, soil organic matter to a certain extent fixed and release of selenium, However, the effect of organic matter content on selenium adsorption and the effect of other competing ions on soil selenium adsorption is unclear. In this study, the effects of two different land use methods and five long-term fertilization methods on the sorption and desorption of selenium were studied by batch experiments, and the effects of phosphate on the adsorption and desorption of selenium in soil were studied. The purpose of this study was to provide a theoretical basis for the evaluation of the availability of exogenous selenium salts in soil. The main results are as follows: (1) the sorption of selenium was significantly affected by different soil management methods. With the increase of time, the sorption of selenium in 7 soils was a fast and slow process, and the adsorption equilibrium was reached at 8 h. Among them, the sorption capacity of uncultivated crops treated soil (abandoned, The sorption capacity of selenite in different fertilization treatments was in the order of: 1. NPKCKSNPKM2NPKM1NPK, and the order of sorption capacity of selenite was: SNPKNPK2NPKM1NPKCK; the content of organic matter was different between the two treatments. The amount of selenium adsorbed by M1NPK and M2NPK in other soils with similar physical and chemical properties was higher than that under M1NPK treatment. The adsorption capacity of tetravalent selenium on the same soil was about 2.83 times as much as that on hexavalent selenium. The second-order kinetics is a better model to describe the kinetic characteristics of soil selenium adsorption (tetravalent selenium R20.982and hexavalent selenium R20.981).Langmiur model to fit the isotherm R20.991a). The K _ d value of the seven soils decreased with the increase of the initial concentration of selenium solution, and the K _ d value of the uncultivated soil was significantly higher than that of the cultivated soil. The desorption rate of different soils increased with the increase of the initial concentration of selenium solution, and the desorption rate of soil with high organic matter content was relatively low, showing the effect of fixing selenium. Phosphate has different effects on soil sorption of selenium. With the addition of competing ion phosphate and the change of concentration gradient, the adsorption of selenite and selenite was different in different soils. The adsorption of selenite and selenite in soil was obviously reduced by the presence of phosphate ion because of the competition between phosphate and selenium in soil. Because of the strong binding energy of phosphate ion, it occupies the specific adsorption site on the soil surface, and the adsorption amount of tetravalent selenium on soil gradually decreases with the increase of phosphate ion concentration. However, the adsorption capacity of hexavalent selenium increased slightly. M _ 2NPK treatment was higher than that of M1NPK treatment. When the concentration of selenite was constant, the KD value of soil decreased with the increase of phosphate concentration, and gradually decreased with the increase of selenium concentration, and the KD value of soil increased with the increase of phosphate concentration when the concentration of selenite was constant. The desorption rate of selenite increased with the increase of phosphate concentration, while the desorption rate of selenite decreased. In a word, the sorption and desorption of selenium by soil with different management measures for a long time have obvious influence, and the high content of organic matter can play a role of fixing selenium, and the adsorption of selenium to soil by phosphate ion is related to the valence state of selenium in soil. Comprehensive consideration should be given to the biological enhancement of selenium.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S153

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