Lake Järnsjön

Järnsjön is a very small and shallow lake, traversed by the river Emån, and that has been heavily polluted by PCB. Fourteen sediment cores were sampled and X-rayed before the restoration of the lake, among others in order to determine the erodibility of the bottom deposits. Radiographs of one of these cores is shown below.

Stereoradiographs of the upper and monoradiograph of the middle part of core 1377 from a depth of 2 m in the eastern part of  Lake Järnsjön. The lead letter 0 marks corresponding levels on the partly overlapping radiographs.

These radiographs are shown in a reduced scale in order to make it possible to study the sedimentary structures in three dimensions without the help of a stereoscope. When studying the stereoradiographs, you should start with your nose close to the monitor, then pull your face slowly away from it, and look through the image.

Click here to get a better resolution of the radiographs.

As exemplified by the radiographs of core 1377 the uppmost deposits in Lake Järnsjön were to a large part redistributed both due to bioturbation and to erosion by currents.

Downcore variation in void ratio in core 1377.

Void ratio is a very important parameter when calculating the erodibility of fine-grained, more or less cohesive sediments.

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