Leaphart James C, Wilms Kaitlin C, Bryan A Lawrence, Beasley James C
University of Georgia, Savannah River Ecology Laboratory, Aiken, SC, 29802, USA; University of Georgia, Warnell School of Forestry and Natural Resources, Athens, GA, 30602, USA.
University of Georgia, Savannah River Ecology Laboratory, Aiken, SC, 29802, USA.
J Environ Radioact. 2019 Jul;203:25-29. doi: 10.1016/j.jenvrad.2019.02.012. Epub 2019 Mar 5.
As a result of activities such as nuclear weapons testing, nuclear power generation and waste disposal, and nuclear accidents, radiocesium (Cs) is a widely distributed radio-contaminant of concern that readily accumulates in exposed wildlife. Although bioaccumulation of Cs is an important factor for understanding its fate within the environment, there are currently limited data available on bioaccumulation patterns of Cs in amphibians, despite their widespread distribution and potential to transport contaminants between aquatic and terrestrial ecosystems. Therefore, the objective of this study was to determine the amount of time necessary for anuran larvae experimentally placed in a contaminated system to reach a steady-state whole-body Cs concentration, and to determine the threshold at which that steady-state Cs concentration occurred for tadpoles within our study system. By restricting uncontaminated bullfrog (Lithobates catesbeianus) larvae to three experimental enclosures located along aCs contaminated effluent canal on the U.S. Department of Energy's Savannah River Site, we modeled Cs uptake through time using the von Bertalanffy modification of the Richards Model. The results of our modified Richards Model indicate that bullfrog tadpoles achieved steady-state Cs concentrations of 3.68-4.34 Bq/gCs dry whole-body weight after 11.63-15.50 days of exposure among sampling sites, with an average of 3.94 Bq/g after 14.07 days exposure. Radiocesium accumulation in bullfrog tadpoles was more rapid than that reported for other biota studied from other contaminated systems, likely due to incidental ingestion of sediments and a diet consisting of periphyton and other items that accumulate high levels of Cs. Given their rapid accumulation of Cs and inability to leave aquatic environments prior to metamorphosis, our data suggest amphibian larvae may be useful indicators for monitoring Cs distributions and bioavailability within aquatic systems.
由于核武器试验、核能发电与废物处理以及核事故等活动，放射性铯（Cs）成为一种广泛分布且令人担忧的放射性污染物，它很容易在受辐射的野生动物体内蓄积。尽管铯的生物累积是了解其在环境中归宿的一个重要因素，但目前关于两栖动物体内铯生物累积模式的数据有限，尽管两栖动物分布广泛且有在水生和陆地生态系统之间传输污染物的可能性。因此，本研究的目的是确定实验放置在受污染系统中的无尾目幼体达到全身铯浓度稳态所需的时间，并确定在我们的研究系统中蝌蚪达到该稳态铯浓度的阈值。通过将未受污染的牛蛙（Lithobates catesbeianus）幼体限制在美国能源部萨凡纳河场地一条受铯污染的排污渠沿线的三个实验围栏中，我们使用理查兹模型的冯·贝塔朗菲修正模型对铯随时间的吸收进行了建模。我们修正后的理查兹模型结果表明，牛蛙蝌蚪在各采样点暴露11.63 - 15.50天后，全身铯浓度达到3.68 - 4.34 Bq/g铯干重的稳态，暴露14.07天后平均为3.94 Bq/g。牛蛙蝌蚪体内放射性铯的积累比其他受污染系统研究的其他生物群报告的速度更快，这可能是由于偶然摄入沉积物以及以积累高浓度铯的附生植物和其他物质为食。鉴于它们对铯的快速积累以及在变态前无法离开水生环境，我们的数据表明两栖动物幼体可能是监测水生系统中铯分布和生物可利用性的有用指标。
