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- Konovalenko, Lena, 1976-
(författare)
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Element transport in aquatic ecosystems – Modelling general and element-specific mechanisms
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radionuclides are widely used in energy production and medical, military and industrial applications. Thus, understanding the behaviour of radionuclides which have been or may be released into ecosystems is important for human and environmental risk assessment. Modelling of radionuclides or their stable element analogues is the only tool that can predict the consequences of accidental release.In this thesis, two dynamic stochastic compartment models for radionuclide/element transfer in a marine coastal ecosystem and a freshwater lake were developed and implemented (Paper I and III), in order to model a hypothetical future release of multiple radionuclides from a nuclear waste disposal site. Element-specific mechanisms such as element uptake via diet and adsorption of elements to organic surfaces were connected to ecosystem carbon models. Element transport in two specific coastal and lake ecosystems were simulated for 26 and 13 elements, respectively (Papers I and III). Using the models, the concentration ratios (CR: the ratio of the element or radionuclide concentration in an organism to the concentration in water) were estimated for different groups of aquatic organisms. The coastal model was also compared with a 3D hydrodynamic spatial model (Paper II) for Cs, Ni and Th, and estimated confidence limits for their modelled CRs. In the absence of site-specific CR data, being able to estimate a range of CR values with such models is an alternative to relying on literature CR values that are not always relevant to the site of interest.Water chemistry was also found to influence uptake of contaminants by aquatic organisms. Empirical inverse relationships were derived between CRs of fish for stable Sr (CRSr) and Cs (CRCs) and water concentrations of their biochemical analogues Ca and K, respectively (Paper IV), illustrating how such relationships could be used in the prediction of more site-specific CRCs and CRSr in fish simply from water chemistry measurements.
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| 2. |
- Konovalenko, Lena, 1976-
(författare)
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Element transport in marine coastal ecosystems – modelling general and element-specific mechanisms
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the behaviour of naturally-occurring and anthropogenically-derived radionuclides (isotopes) in the marine environment is important, because there is a need for their effective utilization either as in situ tracers or for industry, medical applications, the planning of waste-disposal facilities, and estimations of human and animal health risks. Radionuclides generally have the same chemical properties as their stable element analogues and thus show similar environmental behaviour and cycling to their stable counterparts. However, they are distinguished by potentially enhanced impacts on organisms due to their radioactivity emitted as alpha, beta or gamma radiation. There are many nuclear facilities, such as power reactors, research reactors, waste handling facilities and fuel production facilities located in the drainage area of the Baltic Sea which discharge directly or indirectly into the Baltic Sea. Thus knowledge about factors and processes in space and time that control the fate of radionuclides in the aquatic ecosystem provide the basis for dose and risk assessment for human and biota. Radionuclides’ stable analogues are often elements that have numerous industrial applications and are used widely in society (e.g., metals, rare earth metals). These are often released in aquatic environments and can be toxic. Consequently, they also require better control in order to protect the environment from pollution and provide quick responses in case of accidents. Understanding how such elements are distributed in the freshwater, seawater, sediments and aquatic organisms is therefore important. Modelling is a useful approach for the estimation of possible element concentrations and inventories in the aquatic ecosystem.In this thesis a dynamic stochastic compartment model (K-model) for radionuclide transfer in a marine coastal ecosystem was implemented for a coastal area in Öregrundsgrepen, Baltic Sea, Sweden, in order to determine the fate of radionuclides released in the sea water (Paper I). Radionuclide-specific mechanisms such as radionuclide uptake via diet and adsorption of radionuclides to organic surfaces were connected to the ecosystem model. Using the model, we estimated concentration ratios (CR; the ratio of the radionuclide concentration in an organism to the concentration in water) in the ecosystem and compared these with measured data for grazers, benthos, zooplankton and fish for 26 elements. The uncertainty variations of CRs were reduced when the model was parameterised with site data and elements with higher sorption capacity had higher CRs for all organism groups. The K-model was also validated with a 3D hydrodynamic spatial model (D-model) (Paper II). Despite differences in temporal resolution, biological state variables and partition coefficients, the accumulation of Th-230, Cs-135 and Ni-59 in biological compartments was comparable between the models and with site measurements. Both models provided confidence limits for their modelled concentration ratios, an improvement over models that only estimate mean values. The models developed here are useful tools for assessing the degree to which organisms can be affected by the distribution and fate of pollutants in the marine environment.
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