大型海藻对重金属镉、铜的富集动力学研究

以人工培育的龙须菜(Gracilaria lemaneiformis)活体为实验材料,在低浓度Cu2+、Cd2+污染水体中,进行龙须菜对Cu、Cd富集的模拟实验,探索龙须菜对Cu、Cd的污染水体的修复,以及龙须菜食品的安全性.应用两箱动力学模型,对实验结果进行了曲线拟合,对拟合优度进行检验.结果表明,在本实验条件下,龙须菜对重金属Cu、Cd的生物累积符合两箱动力学模型,并获得龙须菜富集Cu、Cd的吸收速率常数(Ku)和排出速率常数(Kc).当Cu2+的浓度￡50mg/L、Cd2+的浓度￡20mg/L时,经过28 d的暴露,随Cu2+、Cd2+的暴露浓度以及暴露时间增大,龙须菜中Cu、Cd的含量升高.龙须菜对Cu、Cd的吸收速率常数分别为15.4~51.1和13.9~55.7,基本随实验水体中元素的暴露浓度升高而降低;排出速率常数分别为0.023~0.070和0.030~0.050,与暴露浓度无明显相关性.理论平衡状态下龙须菜中Cu、Cd含量(质量分数)随水体中暴露浓度升高而增加.龙须菜对Cu、Cd的生物富集因子分别为663~1008和463~1113,Cu、Cd的生物半衰期分别为23.1 d和20.1d.

Kinetic study on the bioconcentration of cadmium and copper by large-sized seaweed Gracilaria lemaneiformis

The large-sized seaweeds are important renewable resources, which can be developed to delicious food and industrial materials. They were used to deal with sewage due to its accumulation of heavy metal. The living seaweeds are sensitive to light and temperature, and its growth was inhibited because of the toxicity of heavy metal. Gracilaria lemaneiformis is large-sized seaweed, which was suit for large-scale cultivation offshore. The uptake and clearance of copper and cadmium by Gracilaria lemaneiformis were investigated using artificial cultivated living Gracilaria lemaneiformis coupled with the low copper and cadmium concentrations in this paper. In order to test the practicability of two-compartment model adapted for accumulation of heavy metal by large-sized seaweeds, the experiment results were analyzed with nonlinear curve fitting. The results showed that the accumulation of heavy metal by Gracilaria lemaneiformis was accordance with two-compartment model, the uptake rate constant (Ku) and clearance rate constant (Kc) were also obtained. The Gracilaria lemaneiformis can accumulate copper and cadmium from waters, the contents of copper and cadmium accumulated in Gracilaria lemaneiformis were increased along with the concentrations of copper and cadmium in waters, and increased with the exposed time. Meanwhile, Gracilaria lemaneiformis can eliminate cadmium and copper strongly, because Gracilaria lemaneiformis accumulate mainly cadmium and copper from water by bio-absorption, which is a two-way process. Gracilaria lemaneiformis can also accumulate cadmium and copper by active transport, and those elements were combined to make into organic metals. The uptake rate constant of copper and cadmium accumulated by Gracilaria lemaneiformis was from 15.4 to 51.1, from 13.9 to 55.7, respectively. The clearance rate constant was from 0.023 to 0.070, from 0.030 to 0.050, respectively. The uptake rate constants decreased with exposure concentrations, while the clearance rate constants were no obviously related exposure concentrations. The bioaccumulation factor of copper and cadmium accumulated by Gracilaria lemaneiformis was from 663 to 1008, from 463 to 1113, respectively; and the biological half-life was 23.1 d, 20.1 d, respectively.