不同硬度条件下Cd~(2+)和Cu~(2+)对稀有鮈鲫的急性毒性

为研究水体硬度对稀有鮈鲫Cd~(2+)和Cu~(2+)毒性效应的影响,开展了96 h急性毒性试验。试验结果发现,当水体硬度(以CaCO_3计,下同)为50 mg·L~(-1)、250 mg·L~(-1)、450 mg·L~(-1)时,Cd~(2+)对稀有鮈鲫的96 h半数致死浓度(96 h-LC50)分别为4.30 mg·L-1、12.06 mg·L~(-1)、19.99 mg·L~(-1),对应的安全浓度(SC)依次为0.430 mg·L~(-1)、1.206 mg·L~(-1)、1.999 mg·L~(-1);Cu~(2+)对稀有鮈鲫的96h-LC50分别为0.046 mg·L-1、0.148 mg·L~(-1)、0.228 mg·L~(-1),对应的SC依次为0.0046 mg·L~(-1)、0.0148 mg·L~(-1)、0.0228 mg·L~(-1)。计算得到Cd~(2+)对稀有鮈鲫急性毒性与水体硬度的拟合方程为ln 96 h-LC50=0.687 ln H~(-1).243(r=0.998);Cu~(2+)对稀有鮈鲫急性毒性与水体硬度的拟合方程为ln 96 h-LC50=0.727 ln H-5.923(r=0.999),Cd~(2+)和Cu~(2+)对稀有鮈鲫的硬度斜率分别为0.687和0.727。这些结果表明,水体硬度可有效降低Cd~(2+)和Cu~(2+)对稀有鮈鲫的急性毒性,且稀有鮈鲫的硬度斜率与其他物种差异较大。在评估不同硬度水体下Cd~(2+)和Cu~(2+)的生物毒性及其生态风险时,应根据测试物种特异的硬度斜率而定。

Acute Toxicity of Cadmium and Copper to Gobiocypris rarus under Different Water Hardness

In the present study, the effects of water hardness (as CaCO3) on the acute toxicity to Chinese rare min￣now (Gobiocypris rarus) were investigated. For cadmium (Cd), the 96￣h median lethal concentration (96h￣LC50 ) was 4.30, 12.06, 19.99 mg?L￣1, under 50, 250 and 450 mg?L￣1 concentrations of CaCO3, respectively, and the cor￣responding safety concentration (SC) was 0.430, 1.206 and 1.999 mg?L￣1. For copper (Cu), the 96 h￣LC50 was 0.046, 0.148, 0.228 mg?L￣1, respectively, and the corresponding SC was 0.0046, 0.0148, 0.0228 mg?L￣1, respective￣ly. The relationship between acute toxicity of Cd to rare minnow and water hardness is:ln 96 h￣LC50= 0.687 ln H￣1.243 (r= 0.998), while for Cu, the relationship is:ln 96 h￣LC50= 0.727 ln H￣5.923 (r= 0.999). The hardness slope of toxicity of Cd2+and Cu2+was 0.687 and 0.727, respectively. The results showed that the water hardness effective￣ly reduced the acute toxicity of Cd2+ and Cu2+to G.rarus, and the hardness slope of heavy metals in G.rarus was quite different from that in other species. The present study also imply that the toxicity and ecological risk evalua￣tion of Cd2+ and Cu2+ under different water hardness conditions should depend on the specific hardness slopes of different species.