The influence of land use on the sedimentation of the river delta in the Kyroenjoki drainage basin

Sediment surface samples (0-2 cm) from 66 sites, and longer cores (up to 540 cm) from 9 sites in the estuary of the river Kyroenjoki, Western Finland, were analysed for organic content, P, Fe, Mn, Pb, Cd, Cu and Zn. One core was dated on the basis of annual laminations. Chemical analyses of the cores showed that organic matter and heavy metal content have increased in recent decades. The heavy metal content was clearly lower than in areas polluted by industry. The sedimentation rate in the delta increased between the 1930s and 1950. It decreased in the 1960s, and has been below 1930s levels since 1970. The sedimentation rates of organic matter were fairly stable all through the period measured, even though the organic content increased.