Studies on reference mires: 1. Lastensuo and Pesaensuo in 2010-2011

New lakes and mires will develop in the sea area now surrounding Olkiluoto Island due to the postglacial land uplift. Despite the lack of well-developed mires at present Olkiluoto Island, input data for modelling the future development of the region are needed. Therefore, analogue objects in a larger geographical area have been selected. This Working Report presents first results from studies targeted on two such mires, Lastensuo and Pesaensuo. Not all collected samples have been analysed yet, but will appear in further versions of this report. The characteristics of the study locations appeared to correspond generally well with preliminary information based on literature and GIS analyses. Various site types were covered by the study locations on Lastensuo mire, whereas those on Pesaensuo mire were dwarf-shrub pine bog all over. Pine was the dominant tree species on all of the plots. Because sampling occurred in late summer, some berry (and on Pesaensuo also mushroom) samples were obtained of species typical of mires. On the studied plots, the deepest peat depths reached to 6.5 m (Lastensuo) and 5.5 m (Pesaensuo). Decomposition of sampled peat varied from very weakly decomposed to almost completely decomposed. Element analyses and distribution coefficient values (Kd) of the indigenous key elements Cl, Cs, I, Mo, Nb, Ni, Se and Sr were presented for one plot on Lastensuo mire. Procedures have been improved based on experiences gained on the field and laboratory analyses of the samples. Factors causing uncertainties and further ideas to improve the representativeness of the work are presented in this Working Report. Studies have already been continued on August 2012, when four more plots were established on the Lastensuo mire. In the future, sampling will be extended to another mire. (orig.)