水体硬度对铜和镉生物毒性的影响

研究水体不同硬度条件下铜(以Cu²⁺为主)和镉(以Cd²⁺为主)对金鲫鱼、麦穗鱼及大型溞的生物毒性效应。结果表明，当水体硬度(以CaCO₃计，下同)为80 mg/L时，Cu²⁺对麦穗鱼和大型溞的半数致死浓度（LC₅₀）分别为100和79 μg/L；当水体硬度为250 mg/L时，Cu²⁺对麦穗鱼和大型溞的LC₅₀分别为160和159 μg/L；当水体硬度为50和250 mg/L时，Cd²⁺对金鲫鱼的LC₅₀分别为3.69和16.3 mg/L。随着水硬度的增加，Cu²⁺和Cd²⁺的急性毒性均降低。计算得到Cu²⁺和Cd²⁺的生物毒性硬度斜率分别为0.513和0.923，表明硬度对Cd²⁺的毒性影响大于对Cu²⁺。Cd²⁺对金鲫鱼的亚急性毒性试验结果表明，随着水体硬度的升高，Cd²⁺对金鲫鱼的慢性毒性及进入鱼体内的Cd²⁺浓度均显著降低，说明高水体硬度能显著降低重金属的生物有效性。

Effects of Water Hardness on Ecotoxicity of Cadmium and Copper to Aquatic Organisms

The biological toxicity of Cd2+ and Cu2+ to Carassius auratus, Pseudorasbora parva and Daphnia magna was studied under different water hardness. The results revealed that at the hardness of 80 mg/L CaCO3, the median lethal concentration (LC50) of Cu2+ to P. parva and D. magna was 100 and 79 μg/L, respectively; and at the hardness of 250 mg/L the LC50 of Cu2+ to the two organisms was 160 and 159 μg /L, respectively. The LC50 of Cd2+ to C. auratus at the hardness of 50 and 250 mg/L was 3.69 and 16.3 mg/L, respectively. The results showed that the acute toxicity of Cu2+ and Cd2+ to aquatic organism decreased with the increase of water hardness. The hardness slope of toxicity of Cu2+ and Cd2+ was 0.513 and 0.923, respectively, and the influence of hardness on toxicity of Cd2+ was greater than that of Cu2+.The results of subacute toxicity test for C. auratus showed that the chronic toxicity and quantity of Cd2+ absorbed by the fish were reduced when the hardness increased. It revealed that the higher water hardness was able to reduce the bioavailability of heavy metal.