摘要
核能发电实现经济效益增长的同时,也存在使得放射性物质进入核电站附近水域的风险,对生态环境产生了一定的影响.斑马鱼作为实验室常用的水生模式生物,对外界环境变化十分敏感,可起到理想的环境监测指示作用.该文探究了斑马鱼对核电站液态流出物中主要放射性核素之一的137Cs的浓集与排出动力学过程.通过对养殖方法和装置进行设计,实现了斑马鱼在放射性水体条件下的养殖,并以活体检测的方式对斑马鱼体内的137Cs活度进行定期测量.结果显示:在放射性活度浓度约1 000 Bq/L的养殖条件下,浓集实验初期斑马鱼对137Cs的吸收较快,其体内137Cs比活度呈直线上升趋势,直至第50d左右基本保持不变,对应的生物浓集系数为(5.81±0.23)L/kg;排出实验初期斑马鱼体内137 Cs比活度下降较快,但从第60 d左右下降趋势开始变得不明显,最终趋于平缓.整体表现出斑马鱼对137 Cs富集水平相对较低,但不易排出的特点.该实验可为核电发展对水生生物的影响评估以及水环境评价工作提供一定的参考.
Abstract
[Objective]Although nuclear energy provides economic benefits,it releases substantial radioactive substances into nearby waters,thereby affecting the ecological environment.Aquatic organisms in radioactive waters accumulate nuclides,reaching a stable concentration within their bodies over time.At this point,the concentration factor,combined with the nuclide concentration in aquatic organisms,can be used to estimate the radioactivity level in target waters.Radiation doses at other trophic levels can be estimated through the food chain.During the transmission process of the food chain,different degrees of radionuclide accumulation were observed at various fish trophic levels.In addition,at the same trophic level,radionuclide accumulation usually differs in fish individuals with various feeding and metabolic rates.Therefore,the concentration factor of different fish species,especially those with large differences in body size,varies considerably.Direct application of the concentration factor recommended by the International Atomic Energy Agency may lead to large deviations in the calculated results.Zebrafish are commonly used aquatic model organisms in the laboratory.This typically small fish has a length of 3-5 cm and is sensitive to changes in the water environment,making it an ideal indicator organism for environmental monitoring.Therefore,this study considered zebrafish as the research subject to explore the accumulation and discharge kinetics of 137Cs,which is one of the main radionuclides in the liquid effluents of nuclear power plants,to provide a reference for assessing the impact of nuclear power development on aquatic organisms.[Methods]Zebrafish were bred in radioactive water via a specially designed breeding method and equipment,and 137Cs activity in live zebrafish was measured periodically through high-purity germanium gamma spectrometry.The reliability of the living efficiency scale was verified through the gray treatment of zebrafish postmortem.[Results]The results showed a 8.16％average absolute relative error between measurements obtained from living and deceased zebrafish,which confirmed the scale's reliability.Accumulation and discharge experiments revealed that under approximately 1 000 Bq/L radioactivity,137Cs after being rapidly accumulated in the zebrafish during the initiation of the experiment and 137Cs activity in zebrafish increases linearly.Then,after approximately 50 days,the value remained unchanged and reached equilibrium.At the beginning of the discharge experiment,the 137Cs activity in zebrafish decreased rapidly.However,from around the 60th day,the decreased trend of 137Cs activity became insignificant,and the curve flattened in later stages.[Conclusions]Zebrafish exhibited relatively low 137Cs accumulation with a concentration factor of(5.81±0.23)L/kg at equilibrium.The 137Cs discharged by zebrafish exhibited an initial rapid change,followed by a slow rate of change.When all the zebrafish died on the 198t1 day,the specific activity of 137Cs remained at approximately 2 370 Bq/kg.This finding suggests the prolonged discharge of 137Cs in zebrafish,indicating a relatively low metabolic rate and difficult discharge.Zebrafish are sensitive to changes in the water environment,and the accumulation and discharge characteristics of 137 Cs can provide a reference for investigating the influence of liquid effluents from nuclear power plants on other aquatic organisms and assessing the water environment.
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