水温和余氯对拟穴青蟹幼蟹的急性毒性研究

Acute Toxicity of Water Temperature and Residual Clorine to Juvenile Mud Crab Scylla paramanosain

为探明三门湾核电站温排水对海区甲壳类生物的急性致死效应,笔者通过室内模拟三门湾核电站温排水的余氯残留和温升效应,设计3×12的正交试验,研究温度和游离余氯耦合、温度和化合余氯耦合下对拟穴青蟹幼蟹死亡率的影响。试验水温为25、30、35℃,初始游离余氯质量浓度为5.0、6.0、7.0、8.0、9.0 mg/L,以砂滤海水为对照组;化合余氯质量浓度为30.0、36.0、42.0、48.0、54.0 mg/L,以1.575×10^(-3)mg/L NH_4OH为加氨对照组。试验结果显示,单一温度胁迫对拟穴青蟹幼蟹存活率无显著性影响(P>0.05);温度耦合下游离余氯和化合余氯对拟穴青蟹幼蟹的致死率进一步提高。游离余氯和化合余氯的96 h半致死质量浓度随温度升高逐渐降低,且均在35℃时达到最低,35℃时其96 h半致死质量浓度分别为4.455 mg/L和27.290 mg/L,每1℃温升和1 mg/L余氯增加导致死亡率分别提高了0.316%和0.027%。同时,确定了25-35℃游离余氯安全质量浓度为0.446~0.544 mg/L,化合余氯安全质量浓度为2.729^(3).294 mg/L。试验结果表明,化合余氯对拟穴青蟹幼蟹的96 h半致死质量浓度约为游离余氯的6倍,游离余氯和温度耦合导致的拟穴青蟹幼蟹死亡率为化合余氯的11.7倍。本试验结果可为评估三门湾核电站海区中余氯排放对甲壳类生物的影响提供科学依据,也可为制订沿海电厂温排水排放标准提供数据参考。

In order to investigate the acute lethal effect of warm drainage in Sanmenwan Nuclear Power Plant on crustacean in the sea area, a 3×12 orthogonal experiment was designed to study the effects of temperature and residual chlorine coupling on the mortality of juvenile Scylla paramamosain by simulating the residual chlorine and temperature rise effect in Sanmenwan Nuclear Power Plant in laboratory. Three different water temperatures ( 25, 30 and 35 ℃), five different gradients of initial free residual chlorine concentration (5.0, 6.0, 7.0, 8.0 and 9.0 mg/L)and five different gradients of combined residual chlorine concentration (30.0, 36.0, 42.0, 48.0 and 54.0 mg/L) were set. At the same time, filtered seawater was set as the control for temperature treatment groups as well as the free chlorine treatments groups, whereas 4.5×10^(-5) mol/L NH 4OH was set as the control for the combine chlorine treatment groups. The results showed that the single temperature rise had no significant effect on the survival rate of juvenile S.paramamosain ( P >0.05);The mortality rate of the free residual chlorine and combined residual chlorine to the juvenile was further increased in case of coupling with temperature rise. The 96 h semi-lethal concentration (96 h LC 50 ) of free residual chlorine and combined residual chlorine decreased gradually with the rising temperature, and reached the lowest value at 35 ℃. The LC 50 values at 96 h at 35 ℃ were 4.455 mg/L and 27.290 mg/L, respectively. The mortality rate increased by 0.316% and 0.027% with 1 ℃ temperature rise and 1 mg/L residual chlorine increase, respectively. At the same time, the safe concentration of free residual chlorine ranged from 0.446 mg/L to 0.544 mg/L, and the safe concentration of combined residual chlorine ranged from 2.729 mg/L to 3.294 mg/L. The results showed that the 96 h half-lethal concentration of the combined residual chlorine is about 6 times of the value of the free residual chlorine, and the increase in juvenile crabs mortality caused by free residual chlorine together with temperature rise is about 11.7 times of the mortality caused by the combined residue chlorine only. This study can provide a scientific basis for evaluating the effect on crustaceans associated with residual chlorine discharge in the sea area on crustaceans in the sea area of Sanmen Bay Nuclear Power Plant, and also provide a data reference for the formulation of the standards of warm water discharge discharge for coastal power plant.