中文摘要：

研究中性紫色土表面吸附Cu~（2＋）、Zn~（2＋）后对其在水体中凝聚沉降的影响,为重金属离子释放对三峡库区水-土界面生态系统造成的风险提供数据参考。2014年10月,采集西南大学桑园的中性紫色土表层土壤,以Cu-（NO_3）_2和Zn（NO_3）_2配制重金属离子,进行Cu~（2＋）和Zn~（2＋）对中性紫色土凝聚沉降实验、测定中性紫色土颗粒吸附Cu~（2＋）和Zn~（2＋）后zeta电位值。研究结果表明：（1）中性紫色土吸附Cu~（2＋）、Zn~（2＋）后水体中土壤颗粒含量随时间不断减小,并且呈先快速后缓慢减小的规律,在不同浓度条件下土壤颗粒含量变化规律表现差异较大,其临界浓度分别为0.3~0.5和0.5~0.7 mmol/L。（2）水体中中性紫色土颗粒平均沉降速率均随Cu~（2＋）、Zn~（2＋）浓度升高而增大,分别从1.01 cm/min增加到2.92和2.58 cm/min,表现为Cu~（2＋）〉Zn~（2＋）;过程分为3个阶段：缓慢增加,快速增加和基本不变,平均沉降速率随浓度变化临界范围分别为0.3~0.5和0.5~0.7 mmol/L。（3）水体中中性紫色土颗粒zeta电位绝对值随Cu~（2＋）、Zn~（2＋）浓度升高而变小,同时表现为Ca~（2＋）〉Zn~（2＋）〉Cu~（2＋）,土壤颗粒吸附Ca~（2＋）、Cu~（2＋）和Zn~（2＋）后zeta电位绝对值随浓度变化临界浓度范围分别为0.8、0.3~0.5和0.5~0.7 mmol/L。重金属离子吸附在中性紫色土表面减小zeta电位值和静电斥力,加速土壤颗粒凝聚沉降过程。

英文摘要：

Heavy metal pollution is a global environmental problem, resulting in serious ecological effects on water and soil. Heavy metal ions adsorbed on the soil surface alter the surface charge and affects aggregation and settling of soil particles. Purple soil is the primary soil type in the Three Gorges Reservoir area and Cu2＋ and Zn2＋ are com- mon heavy metal pollutants, occurring at high concentrations in both soil and water. Here, we studied the effect of Cu2＋ and Zn2＋ adsorption on the aggregation and settling of neutral purple soil particles to provide data for evalua- ting the ecological risk of heavy metal ion release to the water-soil interface. In October of 2014, surface soil （0 - 20 cm） was collected from the mulberry field of Southwest University, with a pH of 7. 11, organic content of 1.23%, total surface change of 0. 016 c mol/g and specific area of 4.8 x 104 m2/kg. Cu2＋ and Zn2＋ solutions of different concentrations （0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0 and 3.0 retool/L） were prepared using Cu（ NO3 ）z and Zn（ NO3 ）2＂ The aggregation and settling experiments were carried out in conical flasks and the absolute zeta potential of the soil particles in each group was determined after completing the experiments. Results show that： （ 1 ） Adsorption of Cu2 ~ or Zn2 ＋ increased the settling rate, rapidly at first and then more slowly. The concentration of suspended soil particles varied significantly at different concentration Cu2＋ and Zn2 ＋ groups. The ranges of the critical concentrations of Cu2 ＋ and Zn2 ＋ were, respectively, 0.3 - 0.5 mmol/L and 0.5 - 0.7 mmoL/L, much low- er than the critical concentration of Ca2~ （0.8 mmol/L） ; （2） the average settling velocity of the neutral purple soil particles increased with Cu2＋ or Zn2＋ concentration within the critical concentration ranges and then increased, re- spectively, from （1.01 -＋0.08） cm/min to （2.92 -＋0.11） cm/min and （2.58 -＋0.05） cm/min. The change in settling velocity included three s