摘要:
金属氧化物纳米颗粒的广泛应用导致它们大量地释放到水环境中,其独特的理化性质有可能改变水环境中其他共存污染物(如重金属)的生态毒性。为评价沉积物中纳米氧化铝(Al2O3-NPs)对重金属Cd生态毒性的影响,采用底栖生物慢性暴露研究了Al2O3-NPs存在条件下Cd在底栖动物铜锈环棱螺体内生物积累的变化和Cd对肝胰脏抗氧化防御系统关键成分超氧化物歧化酶(SOD)与脂质过氧化指标丙二醛(MDA)以及Ⅱ相反应的关键酶谷胱甘肽-S-转移酶(GST)的影响。结果表明,低Cd浓度(5μg·g-1)时,Al2O3-NPs对Cd生物积累没有影响;中、高Cd浓度(25、100μg·g-1)时,Al2O3-NPs显著促进Cd的生物积累,Al2O3-NPs对Cd的生物转运具有明显的携带效应。低Cd浓度时,无Al2O3-NPs处理组和Al2O3-NPs处理组的SOD活性与对照组相比均没有显著差异;中Cd浓度时,SOD活性显著升高,而高Cd浓度时,SOD活性显著下降,而且Al2O3-NPs处理组的SOD活性显著低于无Al2O3-NPs处理组,Al2O3-NPs的存在加重了Cd对肝胰脏细胞的氧化胁迫或损伤。高Cd浓度时,无Al2O3-NPs处理组和Al2O3-NPs处理组的MDA水平均显著升高,但Al2O3-NPs处理组的MDA水平显著低于无Al2O3-NPs处理组,进一步证明Al2O3-NPs对Cd氧化损伤的增强作用。中、高Cd浓度时,无Al2O3-NPs处理组和Al2O3-NPs处理组的GST活性均显著下降,但Al2O3-NPs处理组的GST活性均显著低于无Al2O3-NPs处理组,同样说明了Al2O3-NPs对Cd毒性的增强作用。本研究提供了在沉积物-底栖动物体系中Al2O3-NPs促进重金属生物积累的证据,而且Cd毒性的变化与肝胰脏中Cd的生物积累水平的变化基本一致,在中、高Cd浓度下,由于Al2O3-NPs的存在显著促进了Cd的生物积累,因而增强了Cd对铜锈环棱螺的生态毒性。
Abstract:
The widespread applications of metal oxide nanoparticles lead to unintentional release of these materials into aquatic environments, the unique physico-chemical properties may potentially alter the ecotoxicity of co-existingcontaminants, such as heavy metals. In this work, the dynamics of Cd accumulation and the effects of Cd on two key components of antioxidant defense system, superoxide dismutase(SOD) and lipid peroxidation index malondialdehyde(MDA), and phase Ⅱ biotransformation enzyme glutathione-S-tansferase(GST) in the hepatopancreas of Bellamya aeroginosa, a benthic macroinvertebrate, were investigated in the presence of aluminum oxide nanoparticles(Al2O3-NPs) by applying chronic exposure to assess the impacts of Al2O3-NPs on ecotoxicity of Cd. The results showed that Al2O3-NPs had no significant effect on Cd bioaccumulation at low Cd concentration(5 μg·g-1). By contrast, Cd bioaccumulation was significantly enhanced by Al2O3-NPs at medium and high Cd concentration(25and 100 μg·g-1), indicating obvious carrier effect of Al2O3-NPs on Cd biotransport. At low Cd concentration, SOD activities in treatments with or without Al2O3-NPs, had no significant difference compared to the controls; at medium Cd concentration, SOD activities in all treatments significantly increased. But at high Cd concentration SOD activities significantly decreased, and moreover SOD activities in treatments with Al2O3-NPs were statistically lower than those in treatments without Al2O3-NPs, indicating the presence of Al2O3-NPs aggravated oxidative stress or damage caused by Cd. For MDA, at high Cd concentration, MDA levels in treatments with or without Al2O3-NPs significantly increased, but MDA levels in treatments with Al2O3-NPs were lower than those in treatments without Al2O3-NPs,which further testified the enhancement of Al2O3-NPs on oxidative damage by Cd. As for GST, at medium and high Cd concentration, GST activities in treatments with or without Al2O3-NPs significantly decreased, but GST activities in treatments with Al2O3-NPs were significantly lower than those in treatments without Al2O3-NPs, which also confirmed above enhancement effects. Overall, our study provided the evidence that Al2O3-NPs enhanced Cd bioaccumulation in the sediment-zoobenthos system, and the change of Cd toxicity coincided with the body burden of Cd, at medium and high Cd concentration, high levels of Cd bioaccumulation enhanced ecotoxicity of Cd on B.aeroginosa.
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