Toxic Effects Of Nanomaterial-cadmium Complexes On Aquatic Organisms

The effects of Cd²⁺ and cadmium-adsorbed nanomaterials（Nano-Cd）on acute toxicity,physiological indexes and tihe DNA damage status of Daphnia magna and Zebrafish were studied in this paper.The results were as follows:The toxicity of cadmium（Cd）,nano-manganese dioxide-cadmium（nMn02-Cd）,20 nm nano-hydroxyapatite-cadmium（nHAP20-Cd）,and 40 nm nano-hydroxyapatite-cadmium（nHAP40-Cd）to D.magna was in the following order:Cd²⁺>nMnO₂-Cd>nHAP20-Cd>nHAP40-Cd.Further,nMnO₂-Cd,nHAp20-Cd,and nHAp40-Cd showed acute toxicity to D.magna of toxic and level Ⅱ grade according to the Commission of the European Communities（ECC）and OECD standards.The activities of superoxide dismutase（SOD）,Catalase（CAT）,Peroxidase（POD）and anti-superoxide anion（ASA）in D.magna increased with the concentration of Cd²⁺and Nano-Cd,showing a trend of rising first and then decreasing.Exposure to low and medium,but not high,Nano-Cd concentrations increased the activities of peroxidase（POD）,superoxide dismutase（SOD）,catalase（CAT）and anti-superoxide anion（ASA）.Thus,Nano-Cd,particularly at high concentrations,could exert oxidative damage in D.magna.An increase in Cd and Nano-Cd concentrations gradually increased the malondialdehyde（MDA）content,indicating cell membrane damage caused by the production of excessive O₂-.The toxicity of Cd²⁺ and Nano-Cd to Zebrafish was in the following order:Cd²⁺>nMnO₂-Cd>nHAP20-Cd>nHAP40-Cd.Further,nMnO₂-Cd,nHAp20-Cd,and nHAp40-Cd showed acute toxicity to Zebrafish of toxic and level Ⅱ grade according to the ECC and OECD standards.Cd²⁺ and Nano-Cd could affect the levels of O₂·-,malondialdehyde,and membrane permeability,accompanied by changes in the antioxidant status.Exposure to low and medium Nano-Cd concentrations increased the activities of POD,SOD,CAT and ASA,but declined at high Nano-Cd.It is indicated that the Nano-Cd could exert oxidative damages to zebrafish,particularly in samples with higher concentrations of Nano-Cd.With the increase of Cd²⁺ and Cd-loaded concentrations,the MDA content increased gradually.This result showed the cell membrane was damaged due to its produces the excessive O₂·-.According to comet assay,both Cd²⁺ and Nano-Cd can cause DNA damage of zebrafish liver,and with an increase of exposure concentration,DNA damage became more serious.In addition,DNA damage in Cd treatment was more severe than that of Nano-Cd The toxicity of Cd and Nano-Cd to DNA was same trend as acute toxicity.Thus,the use of nanomaterials as an adsorption material is associated with a potential risk to the aquatic environment.