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氧化铁和高岭石是红壤中可变电荷的主要来源,对红壤的酸碱变化起到缓冲作用.本研究基于红壤矿物的表征和酸碱滴定实验结果,采用1-site/2-pK表面络合模型获得了其表面活性位点浓度Hs、密度Ds、酸碱平衡常数pK_a~(int)以及电荷零点pH_(pzc)等相关参数,定量解析了氧化铁和高岭土的酸碱缓冲能力.结果表明:该模型能较好地适用于分析针铁矿、赤铁矿及高岭石的表面酸碱性质;针铁矿、高岭石表面活性位点浓度Hs较高,说明其对酸具有较好的缓冲效果.根据上述酸碱性质参数,模拟计算了不同pH下的矿物表面化学物种,揭示了矿物表面反应缓冲土壤酸碱变化的机制.采用上述酸碱滴定方法及模型计算方法,分析实际林地红壤样品的酸碱缓冲能力,并采用表面络合模型计算了其表面化学物种,验证了该方法用于林地红壤酸碱缓冲能力分析的可行性.
Iron oxide and kaolinite are the main sources of variable charge in red soils, which have a buffer effect on the changes of acid and alkali in red soils.In this study, based on the characterization of red soil minerals and the results of acid-base titration, 1-site / 2-pK surface The complexation model was used to obtain the acid-base buffering capacity of iron oxide and kaolin by quantitatively analyzing the related parameters such as the surface active site concentration Hs, density Ds, acid-base equilibrium constant pK_a ~ (int) and charge zero point pH_ (pzc) The results show that this model can be well applied to the analysis of surface acid-base properties of goethite, hematite and kaolinite. Goethite and kaolinite have higher surface active sites (Hs) Good buffering effect.According to the above parameters of acid-base properties, the chemical species of mineral surface at different pH were simulated and the mechanism of acid-base change of mineral surface reaction buffer soil was revealed.Using the above acid-base titration method and model calculation method, the actual The acid-base buffering capacity of the samples from forest soils was calculated. The surface chemical species were calculated by the surface complexation model. The feasibility of this method for the analysis of acid-base buffering capacity of red soil in forestland was verified.