养殖池塘底泥中重金属镉对孔雀石绿代谢的影响

Effect of Cadmium on Degradation of Malachite Green in Sediment from an Aquaculture Pond

采集养殖池塘底泥作为环境载体,进行不同浓度孔雀石绿(MG)的单一污染和MG与重金属镉的复合污染,对培养过程中MG及其代谢产物LMG的含量进行测定,考察重金属镉的环境行为对孔雀石绿降解的影响。结果显示,同MG浓度下的单独污染和复合污染中MG的降解趋势几乎一致,MG的降解动力学方程也相似。在含0、0.5、5.0 mg·kg-1Cd的复合污染下,高浓度(2.5 mg·kg-1)MG的半衰期分别为(3.432±0.059)、(3.362±0.041)、(3.456±0.088)d,低浓度(0.25 mg·kg-1)MG的半衰期分别为(4.140±0.042)、(4.318±0.167)、(4.271±0.045)d,表明在养殖池塘等水体底泥环境中,重金属Cd对MG降解产生的影响很小,不会因Cd的存在而使MG的降解复杂化。实验组LMG的检测结果减去对照组的检测结果,得出LMG的存在量,结果表明重金属Cd对LMG的存在量存在一定影响。在高浓度MG组中,LMG的存在量在整个实验周期中都体现为C0.5 mg·kg-1 Cd(LMG)>C5.0 mg·kg-1 Cd(LMG)>C0 mg·kg-1 Cd(LMG),结合前面Cd对MG的降解影响很小的结果 ,分析Cd对LMG存在量产生影响的原因可能在于:Cd对LMG的进一步降解产生了影响,即一定浓度的Cd能够抑制LMG的生物降解,但较高浓度的Cd又对LMG的非生物降解形成更大的促进作用。

Malachite green(MG) and its metabolites are mutagenic, carcinogenic, and teratogenic to living organisms. These organic com-pounds and heavy metals often coexist in the environment. Here we studied the effect of Cd on MG degradation in aquaculture pond sediment. At the same concentrations, MG degradation trend was not different between single and compound pollution, and the kinetic equations for MG degradation were also similar between them. At 2.5 mg MG·kg-1, the half-life of MG was(3.432 ±0.059),(3.362 ±0.041) and(3.456±0.088)d at 0, 0.5, and 5.0 mg·kg-1Cd, respectively, while at 0.25 mg MG·kg-1, it was(4.140 ±0.042),(4.318 ±0.167) and(4.271 ±0.045)d at 0, 0.5, and 5.0 mg·kg-1Cd, respectively. However, Cd had significant influence on the presence of leuco malachite green(LMG). At high MG concentration, LMG was in order of 0.5 mg·kg-1Cd>5.0 mg·kg-1Cd>0 mg·kg-1Cd treatments during the whole experimental period, implying that low Cd may inhibit biodegradation of LMG, but relatively high concentrations of Cd could facilitate nonbiodegradation of LMG. These results show that heavy metal Cd has little influence on the degradation of MG in sediment environment of aquaculture pond.