Recent sedimentation in 62 lakes in Finland – assessing the possible environmental impacts of peat production

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Authors: 
Vähäkuopus T., Kauppila T., Mäkinen J.E., Ojala A.E.K. and Valpola S.E.
Book (published in): 
Presentations IPS Jubilee 2018
Venue: 
Rotterdam
Year: 
2018
Keywords: 
peat, peat production, lake, sediment, Finland

Summary:

Abstract

The impact of environmental loading of peat production compared to other land uses in lakes and waterways has been actively discussed in Finland for several years.  Especially the question of enhanced sedimentation of organic matter possibly originated from peat production areas has been the most concerning issue. The scarcity of scientific evidence related to the rate of sedimentation in lakes affected by peat production activities has partially prevented a detailed scientific discussion on the topic.

In order to provide a scientific base for governance and decision making, the Geological Survey of Finland launched a lake sediment research project on this topic in 2013. Altogether 62 lakes from 48 different catchment areas were selected, and the majority of field work, data gathering and laboratory analyses were conducted during years 2013-2017. The data gathered from lakes without any connection to peat production areas (reference lake group) were compared to the data from lakes affected by drainage waters coming from peat production areas (target lake group). 

For general classification of catchments the relative proportion of peatland and peat production areas, the amount of ditched peatland areas and relative proportion of lakes and waterways were collected from different national spatial datasets in order to determine the possible differences between lake groups. The results of echo soundings were used for modelling the sedimentation patterns, total amount and areal distribution of sediment. For determining the recent sedimentation development a selected short core samples were taken from each lake with Limnos gravity corer. From the samples 137Cs dating and wide set of chemical and physical properties of sediments were analyzed.

The results show no significant differences in the accumulation rate and recent sedimentation development between two lake groups. According to 137Cs results the 1986 Chernobyl peak is generally found between the sediment depths 3-17 cm. The variation in the lake and catchment characteristics is similar in both lake groups representing areally typical Finnish lakes, geology and land use. The results from chemical and physical analyses of the sediments will be discussed.