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Jerling, L.; Isaeus, M.
Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)2001
Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)2001
AbstractAbstract
[en] This report is a part of the SKB project 'SAFE' (Safety Assessment of the Final Repository of Radioactive Operational Waste). The aim of project SAFE is to update the previous safety analysis of SFR-1.SFR-1 is a facility for disposal of low and intermediate level radioactive waste, which is situated in bedrock beneath the Baltic Sea, one km off the coast near the Forsmark nuclear power plant in Northern Uppland. A part of the SAFE-analysis aims at analysing the transport of radionuclides in the ecosystems.To do so one has to build a model that includes a large amount of information concerning the biosphere.The first step is to collect and compile descriptions of the biosphere.This report is a first attempt to characterise the terrestrial environment of the SFR area of Forsmark. In the first part of the report the terrestrial environment, land class distribution and production of the area is described. The primary production in different terrestrial ecosystems is estimated for a model area in the Forsmark region. The estimations are based on the actual land class distribution and the values for the total primary production (d.w. above ground biomass)and the amount carbon produced, presented as g/m2 for each land class respectively. An important aspect of the biosphere is the vegetation and its development. The future development of vegetation is of interest since production,decomposition and thus storage of organic material, vary strongly among vegetation types and this has strong implications for the transport of radionuclides.Therefore an attempt to describe the development of terrestrial vegetation has been made in the second part. Any prediction of future vegetation is based on knowledge of the past together with premises for the future development.The predictions made, thus, becomes marred with errors enforced by the assumptions and incomplete information of the past. The assumptions made for the predictions in this report are crude and results in a coarse model of the future vegetation. To make this fully clear we have included a description of past development of environmental conditions and vegetation as a key to understand the discrepancy between past events and predictions of the future. Thus, the part dealing with the development of vegetation is started by a description of the past, followed by a prediction of future vegetation. The history of vegetation shows that the development is an interaction between changes in climate, shore displacement,local vegetation development and human activities. Differences in plant community structure can, to a large extent, be related to climatic change. When it got warmer and more humid, nemoral (thermophilus) species immigrated, and the distribution of land classes changed on a regional scale. The most important factors for the change of the biotic environment and plant community has been human impact and climate change, while shore displacement rather has an effect locally and on a short time scale. In the premises for future development of vegetation, change in climate and most of human activities are omitted. A general outline of the anticipated future development of the vegetation is described. There will be a major change in the vegetation of the area from year 3000 to 4000 in that vast areas will be transformed from aquatic to terrestrial. This probably means that new accumulation areas for water transported materials are formed. With the transformation from aquatic to terrestrial environment more stable sinks will be formed such as lakes and mires. In these, organic material will be accumulated and carbon will be concentrated to particular areas. In year 5000 practically no aquatic areas are to be found and at this stage very small amount of organic material will leave the area except by water transport and by gases. Since the mobility is higher in dryer areas where the organic material is decomposed at a faster rate one will expect an increased mobility whereas in wetlands the mobility will be reduced. Therefore, the balance between the wet and dry ecosystems, and hence the mobility of carbon, is hard to predict without a more detailed estimation of future land classes. Environmental factors such as humidity and temperature affect the processes involved and warmer climate, for example, will reduce the accumulation, whereas cool and humid instead speed it up
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Mar 2001; 46 p; ISSN 1402-3091;
; Also available from: http://www.skb.se/uploads/pdf/R-01-09webb.pdf; 75 refs, 11 figs, 7 tabs

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