化工污泥中放射性核素226Ra,232Th的r 辐射环境行为

摘要

Objective To investigate environmental influences of heavy metals and contained radionuclides released from downstream factories of chemical industry according to distribution and contents of radionuclides contained in heavy metal sludge from down-stream enterprise of chemical production.Methods Heavy-metal-containing sludge samples from the area of battery factories and electroplating factories were analyzed and researched. The radioactivity and concentration of radionuclides, such as228Ac,212Pb,212Bi,208Tl,214Pb,214Bi and40K, existing in various specific sludge samples, were analyzed on a High Purity Germaniumγ spectrometer (HPGe). The estimated annual average effective dosage rate con-tributed by these sludge samples were calculated with Monte Carlo N Particle Transport Code (MCNP) dosage rate con-version factors. The enrichment level of radionuclides,232Th and226Ra, during production were indicated by Enrichment Factors (EF). The mathematical correlation was analyzed by connecting the concentration of Pb or Cr measured in sludge, and the concentration of corresponding radionuclide232Th or radium equivalent activity(Raeq) by Pearson matrix.Results The average effective dosage rate caused by the sludge from battery or electroplating factories was 44.8μSv·a-1. The enrichment factors of radionuclides232Th and226Ra ranged from 0.478 to 2.217 and 2.509 to 4.115 respectively, indicating that thorium was enriched in the chromium-containing sludge samples, while radium was enriched in all sludge samples. According to data analysis in Pearson matrix, the correlation between heavy metal Pb or Cr and Raeq was above 0.8, re-vealing that the radioactivity of heavy-metal-containing sludge could be inferred from the content of Pb or Cr within the same sludge sample in practical monitoring task.Conclusion The research makes a contribution to both efficient radiation environmental monitoring and TENORM evaluation.%目的 以化工生产下游企业排放含重金属污泥中放射性核素的分布与含量为研究对象,考察工业生产末端随物料流下行的重金属及其中携带的放射性核素对环境的影响.方法 在重金属排放较为显著的电池、电镀化工企业采集含重金属污泥进行分析研究.利用高纯锗(HPGe)γ能谱仪系统分析不同类别污泥中放射性核素228Ac,212Pb,212Bi,208Tl,214Pb,214Bi和40K的活度和含量,选用蒙特卡罗模型(Monte Carlo N Particle Transport Code)剂量转化因子计算化工企业污泥的年有效剂量率,通过计算富集因子得到放射性核素232Th,226Ra在化工污泥中的富集水平,通过皮尔森系数将测量得到污泥中Pb,Cr等重金属含量以及相应的232Th含量或镭当量活度Raeq相互关联,分析其中的数学相关性.结果 来自电池、电镀化工企业的污泥中放射性有效剂量率为44.8μSv·a-1.放射性核素232Th,226Ra的富集因子(EF-Th和EF-Ra)数值范围分别为0.478~2.217和2.509~4.115,表明放射性核素232Th在含铬污泥中存在富集,而226Ra在污泥中均存在明显富集.皮尔森系数的分析显示,重金属元素Pb和Cr与Raeq的相关性可达到0.8以上,在监测工作中可利用污泥中Pb,Cr含量推算含重金属污泥的放射性水平.结论 该研究工作对辐射环境的快捷监测和TENORM的评价均有实际应用价值.