• 关键词：土壤胡敏酸  Cu²⁺  电位滴定  解离常数  络合常数

• 基金项目：

• 杨亚提
• 西北农林科技大学生命科学学院

• 张一平
• 西北农林科技大学资源与环境学院,陕西杨凌712100

• 摘要：通过电位滴定法及恒定容量模式(CCM)研究了2种土壤胡敏酸的解离特性及其与Cu²⁺的络合特征,结果证明在pH3-7范围内胡敏酸表现为2种一元酸组成的混合酸,实验数据适用于静电模式.胡敏酸的解离常数和Cu²⁺的络合常数应用计算机程序FITEQL32表明,优化的解离常数pK_HL1在3.50-4.89之间,pK_HL2在6.17-8.38之间,2种形态一元胡敏酸解离常数之比小于10⁵,与滴定曲线只有一个突跃区相一致.2种土壤胡敏酸与Cu²⁺络合常数logK_ACu^int大小分别为土HA1346,黑垆土HA2241,非静电模式的优化结果较好.

• Abstract：Potentiometric titration and CCM were performed the study on humic acid extracted from soils.Results showed that humic acid is a mixture of two monoprotic acids and it fits the electrostatic model in CCM at pH3-7 .The dissociation constants and Cu complexation constants were determined by the optimization procedure in the computer program FITEQL32.The dissociation constants p KpK_HL1 is in the range of 3.50 to 4.89, p K HL2 6.17 to 8.38, pK_HL1 / pK_HL2 is below 10⁵, which is consistant with the results of potentiometric titration curve. The Cu²⁺ complexation constant,is 1.346 for old manured loessal soil and 2.241 for dark cultivated loessal soil.A good optimization result is given by nonelectrostatic model.

• Key words：soil humic acid  copper(Ⅱ)  potentiometric titration  dissociation constant  complexation constant

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