The effect of recent (0-80 years) environmental change on the geochemical (XRF and magnetic susceptibility) record of Lærdalsfjord sediments, Western Norway

Abstract

This thesis reconstructs past environmental change using the geochemical record of two sediment cores the Inner and Outer Lærdalsfjord, Western Norway. Reconstruction of past environmental change of the Lærdalsfjord can provide useful information to evaluate the general health status of the related aquatic environment.

X-ray fluorescence and magnetic susceptibility for each of the two fjord basins are analysed and linked to their respective sources.

These sources are (a) the garbage dumping at Raudberg between the 1950s and 1970s, (b) the construction of the Hydropower plants in Borgund (1974) and Stuvane (1988), (c) the building of the Fodnestunnel (from 1993 to 1995) and the Lærdalstunnel (from 1995 to 1999), and (d) the successive loss of the natural delta of the river Lærdalselv due to construction activity by using the rock masses from the tunnel buildings.

Effects are visible in the XRF record regarding marine organic matter (bromine), mineral matter (iron, titanium, manganese, and potassium) and pollutants (lead, copper, argon, and niobium). The magnetic susceptibility reveals the distribution of organic and mineral matter and supports the XRF interpretation.

A simple box model is developed illustrating and summarising the effects of local environmental change on the Lærdalsfjord sediments. This model might help responsible authorities in managing necessary measures