| The soil is the important part of the ecosystem, the human survival of the naturalenvironment and important resource of agricultural production. The growing problem ofheavy metal contamination in soil and groundwater has become a worldwide environmentalproblem. Chromium is one of common heavy metal pollutants in soil and groundwater,attracting widespread attention. Chromium can migrate and transfer; excess accumulation ofchromium in the soil can migrate to deep soil and cause groundwater pollution. In addition,the chromium in the soil can be absorbed by plants and enriched in plants, which endangershuman body health through the food chain. Loess area is widely distributed in our country.The research for the migration and transformation of chromium in the loess layer is few.Aimed at the environmental quality issues of soil and groundwater caused by chromiumpollution, the vertical migration and absorption characteristics of chromium in loess werestudied through indoor soil column-leaching test with the irrigation quantity andconcentration of chromium as controlling factors.The main conclusions of this study are as follows:(1) The migration of water in the loess is studied. Under the unsaturated seepageconditions, soil moisture decreases with the increase of soil depth. Under the saturatedseepage conditions, the soil moisture in the profile increased with the increase of irrigationquota. When the water was irrigated on the soil surface, top soil moisture soon reachedsaturation. As the infiltration and wetting front moved forward constantly, soil moisturecontent was becoming more uniform distribution.(2) Under the unsaturated seepage conditions, Chromium content in the soil has the samechange trend with irrigation quota and moisture content, the migration of chromium and themigration of water has a certain synergy. The result showed that the soil chromium content inthe same loess layer was positively correlated with irrigation quantity and soil water contentunder the condition of the same chromium concentration. When the chromium concentrationin certain, irrigation water, soil water content is higher, the greater the carrying of chromiumions with the water, the soil holds the higher amount of chromium.Under the saturatedseepage conditions, chromium content and the soil moisture content is not the same changetrend. The change trend of the chromium content and the soil moisture content was as well asthe unsaturated seepage at0to20cm soil depth, the chromium content increases with the increase of water content. As the soil water content increases, chrome content shows a trendof decrease in more than20cm depth.(3) The soil chromium content increased with increasing the chromium concentration,the high concentration of chromium can provide sufficient unsaturated adsorption quantity,and chromium content in the soil will increase with the increase of chromium concentration.When the concentration of chromium is high, chromium in surface layer will reach saturationadsorption quickly and flow down to deep soil with saturated adsorption band, and thencontaminate groundwater.(4) When irrigation and chromium concentrations are under certain conditions, thecontent of chromium in soil decreases with the increase of soil depth. Test results show that inunsaturated irrigation conditions, chromium infiltrated in the soil along with the movement ofsoil moisture, and then was fixed by soil adsorption. Due to the loess has good adsorption,chromium ions in the soil solution could be sufficiently adsorbed. Only when the upper layerof soil is too late to adsorb or upper soil layer reaches the saturated adsorption, the chromiumion will continue down with water, because the water content is relatively reduced down and alarge number of chromium ions in the upper soil adsorption, resulting in a lower content ofchromium in soil, the chromium content showed a decreasing trend on the whole section.(5) Loess soils have a good adsorption of chromium. The migration of chromium in loesswas closely related with the depth of soil, irrigation quantity, soil water content and chromiumconcentration, also related to the soil itself on chromium adsorption ability.(6) The migration of chromium in loess was closely related with the depth of soil,irrigation quantity, soil water content and chromium concentration. Using DPS dataprocessing system, the dynamic adsorption quantity of soil chromium and irrigation water andthe concentration of chromium use binary simulation, a curve fitting relation between thesimulation value change trend of the change trend is consistent with the actually measuredvalue, can better describe soil and irrigation water, the concentration of the tracer chromiumthe relationship between the dynamic adsorption capacity. |
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