富里酸对重金属在沉积物上吸附及形态分布的影响

以连续碱提取法获得的乌梁素海沉积物中的富里酸为基础,以原状沉积物和去除有机质沉积物为吸附剂,开展了富里酸对重金属在沉积物上吸附行为和形态分布的影响实验研究.结果表明,有机质的去除和富里酸的添加对沉积物吸附重金属均有一定影响;未添加富里酸条件下,有机质的去除对Cu~(2+)影响最大,可导致沉积物对Cu~(2+)的吸附率下降17.85%;随富里酸添加量的增加,2种沉积物对重金属离子的吸附率均逐渐降低,下降速率表现为Cu~(2+)?Cd~(2+)Zn~(2+)Pb~(2+);当富里酸添加量超过5%时,富里酸逐渐成为影响重金属离子吸附率下降的主导因素;随富里酸添加量的增加,原状沉积物和去除有机质沉积物中重金属的形态分布均有明显变化,添加富里酸增加了体系中H~+的浓度,H~+能够置换碳酸盐结合态金属,使碳酸盐结合态金属从沉积物中释放出来,从而导致重金属的碳酸盐结合态与富里酸添加量呈显著负相关,重金属的有机硫化物结合态含量与富里酸添加量呈显著正相关,Cd因亲有机性较弱,其有机硫化物结合态的含量最低且变化幅度最小.

Effects of Fulvic Acid on Absorption and Form Distribution of Heavy Metals on Sediments

Based on the extracted fulvic acid (FA) from Lake Wuliangsuhai sediments by sequential alkali extraction, this work studied the effects of FA on the adsorption and fraction distribution of heavy metals (HM) on sediments using original sediments and sediments treated with 30% H₂O₂ as adsorbents. The results showed both organic matter and FA had effects on the HM adsorption onto sediments; The treatments of FA-free conditions and the sediments treated by H₂O₂ showed relatively strong influence on Cu²⁺ adsorption, which decreased the Cu²⁺ adsorption by 17.85%. With the increasing FA addition, the adsorption percentage of HM on both types of sediments showed gradually decreasing trends, with the order of Cu²⁺ >>Cd²⁺ >Zn²⁺ >Pb²⁺; when the FA content was more than 5%, FA became the governing factor on the decreasing adsorption percentage of HM. With increasing FA addition, forms distribution of HM showed significant changes in both types of sediments; i.e. FA additions showed significant negative and positive correlations with percentages of metals bound to carbonates and organic matter, respectively, since the FA addition increased the H⁺ concentration of the system, in which H⁺ could activate the metals bound to carbonate from the sediments. As an organophilic weak element, the fraction percentage of Cd bound to organic matter was the lowest with the minimal changes.