Department of Ecology, Environment and Plant Sciences, (DEEP), Stockholm University, 10691 Stockholm, Sweden.
Swedish Nuclear Fuel and Waste Management Co, (SKB), Box 250, 10124 Stockholm, Sweden.
J Environ Radioact. 2017 Apr;169-170:85-97. doi: 10.1016/j.jenvrad.2016.12.016. Epub 2017 Jan 19.
In environmental risk assessments of nuclear waste, there is need to estimate the potential risks of a large number of radionuclides over a long time period during which the environment is likely to change. Usually concentration ratios (CRs) are used to calculate the activity concentrations in organisms. However, CRs are not available for all radionuclides and they are not easily scalable to the varying environment. Here, an ecosystem transport model of elements, which estimates concentrations in organisms using carbon flows and food transfer instead of CR is presented. It is a stochastic compartment model developed for Lake Eckarfjärden at Forsmark in Sweden. The model was based on available data on carbon circulation, physical and biological processes from the site and identifies 11 functional groups of organisms. The ecosystem model was used to estimate the environmental transfer of 13 elements (Al, Ca, Cd, Cl, Cs, I, Ni, Nb, Pb, Se, Sr, Th, U) to various aquatic organisms, using element-specific distribution coefficients for suspended particles (K) and upper sediment (K), and subsequent transfer in the foodweb. The modelled CRs for different organism groups were compared with measured CRs from the lake and literature data, and showed good agreement for many elements and organisms, particularly for lower trophic levels. The model is, therefore, proposed as an alternative to measured CR, though it is suggested to further explore active uptake, assimilation and elimination processes to get better correspondence for some of the elements. The benthic organisms (i.e. bacteria, microphytobenthos and macroalgae) were identified as more important than pelagic organisms for transfer of elements to top predators. The element transfer model revealed that most of the radionuclides were channelled through the microbial loop, despite the fact that macroalgae dominated the carbon fluxes in this lake. Thus, element-specific adsorption of elements to the surface of aquatic species, that may be food sources for organisms at higher trophic levels, needs to be considered in combination with generic processes described by carbon fluxes.
在核废料的环境风险评估中，需要估算大量放射性核素在长时间内的潜在风险，在此期间环境可能会发生变化。通常使用浓度比 (CR) 来计算生物体内的放射性活度浓度。然而，并非所有放射性核素都有 CR，并且它们不容易扩展到不断变化的环境中。这里提出了一种元素的生态系统传输模型，该模型使用碳流和食物转移来估算生物体中的浓度，而不是使用 CR。它是一种为瑞典福斯马克的 Eckarfjärden 湖开发的随机隔室模型。该模型基于该地点的碳循环、物理和生物过程的现有数据，确定了 11 个生物体功能组。该生态系统模型用于估算 13 种元素（Al、Ca、Cd、Cl、Cs、I、Ni、Nb、Pb、Se、Sr、Th、U）向各种水生生物的环境转移，使用悬浮颗粒（K）和上覆沉积物（K）的元素特异性分配系数，以及随后在食物网中的转移。不同生物体组的模型化 CR 与湖泊和文献数据中的实测 CR 进行了比较，结果表明，对于许多元素和生物体，特别是对于较低的营养级，结果具有很好的一致性。因此，该模型被提议作为实测 CR 的替代方法，尽管建议进一步探索主动吸收、同化和消除过程，以使某些元素具有更好的对应关系。底栖生物（即细菌、微型底栖生物和大型藻类）被确定为比浮游生物更重要，因为它们可以将元素转移到顶级捕食者中。元素转移模型表明，尽管在这个湖中，大型藻类主导了碳通量，但大多数放射性核素都通过微生物环进行。因此，需要考虑元素特异性吸附到水生物种表面的情况，这些物种可能是更高营养级生物的食物来源，这需要与碳通量描述的一般过程结合起来。
