| Landfills are ubiquitous in modern society, and the proper managerment of their potential environmental impact is of the highest priority. Mentals may be mobilized by infiltrating rainwater to become part of the landfill leachate, a concentrated aqueous solution of refuse-derived materials. The leachate may then contaminate groundwater supplies by leakage through the landfill liner and/or the vadose zone. Given the signification TOC concentrations, metal-organic complexes are common in landfill leachate.Cadmium and Zinc which are common and have good mobility in the landfill liner are selected as the research model. Hexanoic, representing early stage of landfill leachate evolution, is chosen to study its influence on heavy metal adsorption and fraction distribution. Two liner soils are used as our sample soils: one is subclay from Xiao jianxi landfill in Qingdao; the other is weathering clay from Ling shan landfill in Jimo. Our experiments mainly work over the behavior of heavy metal in single system, binary system and ternary system. Batch equilibrium experiments are conducted to investigate heavy metals sorption on the sample soils and Tessier sequential extraction scheme is carried out to analysis the heavy metals'modality adsorbed to the sample soils. The SPSS analysis software is used to do multi-regression analysis in order that the main factor determining the adsorption of heavy metal can be found out. Fistly, some physico-chemical properties of the experimental soils is mensurated. The result indicate that the sample soils are alkalescent: the pH value of subclay is 8.14 and the pH value of weathering clay is 8.15.The cation exchange capacity of subclay and weathering clay respectively is 16.00cmol/kg and 12.87cmol/kg.Sequently the single system, binary system and ternary system are studied to understand the sorption behavior of heavy metal, the main work is as follows:1. Before all of the experiments, the sufficient time for heavy metal adsorption to reach equilibrium is ascertained. After that, the single system is studied, the result shows:â—‹1 The time for Cadmium to reach adsorption equilibrium in the two soils is 22h, and that for Zinc is 24h.Therefore, in the convenience of practice, the time for heavy metal to reach adsorption equilibrium is determined as 24h.â—‹2 The variation of temperature has some effect on the heavy metal adsorption quantity, but compared with the effect caused by the variation of heavy metal concentration, the influence of temperature is negligible.â—‹3 In the single system, i.e. the sorbate is none but heavy metals, the heavy metal quantity can not unboundedly increase with the augment of its concentration. The Cdmium saturated sorption quantity of subclay is about 31.38g/kg, and the Zinc saturated sorption quantity of weathering clay is about 37.87g/kg. In the single system the Temkin model fits the sorption isotherm better. The sorption of metal is greater with the increase of pH. Two heavy metals have a greater sorption percent in subclay than in weathering clay. For one kind soil, its sorption percent for Zinc is bigger than that for Cadmium.2. In binary system, the addition of hexanoic influencing on the sorption of heavy metal is evaluated. The conclusions summed up are that, compared with the single system, the presence of haxanoic augments the saturated quantity of heavy metal onto the sample soils. It may attribute to the formation of metal-haxanoic complexes. In the binary system, it shows that the Henry model fits the sorption isotherm better, as the result of the low heavy metal concentration. The existence of hexanoic has a great effect on the configuration of Cadmium, because it can increase the organic-Cd fraction; but it has no effect on the modality of Zinc.3. After the research on ternary system, we know:â—‹1 In the ternary system, due to competition on sorption sites, the sorption quantity of two metals on the soils reduces compared with the single system and binary system. The Cdmium saturated sorption quantity of subclay is about 41.91g/kg, the Zinc saturated sorption quantity of weathering clay is about 42.09g/kg. The sorption isotherm can be fitted better with Temkin model. â—‹2 The behavior of Cadmium in subclay and weathering clay with the variation of pH: looking at the variational curve individually, the resemblance is that they all have ascending trend. But after analysising with SPSS software, we find the chief factor deciding the curve is different: it is pH for subclay, and that is the concentration of Zinc for weathering clay.The behavior of Zinc in subclay and weathering clay with the variation of pH: the variational curve in subclay and weathering clay is similar, and after analysising with SPSS software, we find the determinant factor of the two curves is the same, it is pH.â—‹3 No matter in single system, binary system or ternary system, the fraction of Cadmium and Zinc adsorbed in soils represents that, the main configuration of Cadmium is exchangeable-Cd, which can be released easily and has good mobility; that for Zinc is Fe-Mnoxides-Zn, often regarded as steady formation.â—‹4 In the ternary system, the addition of Zinc makes the carbonates-Cd quantity augmented, thereby it accelerates the release of Cadmium; but the addition of Cadmium has no effect on the configuration of Zinc.
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