Natural processes and human factors can activate and migrate the selenium into and out of the soil.Finding out the provenance and migration mechanism of selenium in soil is of great scientific and practical significance for selenium-rich land management and selenium-rich industrial development.The lithosphere and dry and wet deposition of atmosphere are the most basic sources of soil selenium.Surface runoff,groundwater lixiviation,crop harvesting and volatilization of plants and microorganisms are the main ways of selenium loss.The migration of selenium in soil can be attributed to hydrodynamic migration mechanism,solid phase adsorption mechanism and absorption,degradation and volatilization mechanisms.Soil composition and physicochemical conditions affect the migration and redistribution of selenium in soil by changing the process of the above mechanism.Climate,topography and agricultural activities indirectly affect the migration and redistribution of selenium in soil by changing soil composition and physicochemical conditions.Geological background,climatic conditions,and topographic factors are very important for the distribution of selenium on a regional scale(such as continents,countries and provinces),while on a local scale(such as counties,townships and farmland),the impact of human activities,especially agricultural farming,is more significant.Based on the behavioral characteristics of selenium in soil,a series of selenium resource management strategies have been developed:1)Biofortification and remediation regulate selenium distribution and bioavailability in soil through animal and plant transformation,which is considered to be an ecologically Selenium management solution.2)The irrigation mode adjusts the physical and chemical conditions of the soil by changing the hydrodynamic conditions,thereby changing the solid phase adsorption of the soil and the transformation of animals and plants.The water management mode combining flood irrigation and aerobic irrigation is believed to improve the availability of soil selenium.3)Agronomic measures such as applying selenium fertilizer,phosphate fertilizer,sulfur fertilizer and liming adjust the distribution and availability of soil selenium by directly changing soil composition and physical and chemical conditions.This is a traditional selenium-rich agronomic measure,but it may also produce certain ecological effects,risk.
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