Distribution and geochronology of priority pollutants in a large sedimentation area, River Rhine, The Netherlands

Abstract

The concentrations of heavy metals, As, polychlorinated biphenyl (PCB) congeners, poly-nuclear aromatic hydrocarbons (PAH) and various sediment characteristics were determined in 77 samples of the surficial sediments and one 3 m core of Lake Ketelmeer and Lake IJsselmeer in The Netherlands. Absolute contents of these polluting compounds were corrected according to a Dutch normalization procedure. In Lake IJsselmeer the youngest geological layer (Um-deposit) is mainly found in deep sedimentation areas (25%). This deposit is severely polluted in Lake Ketelmeer. Contents of all polluting compounds in this IJm-deposit of Lake Ketelmeer proved to be 1.6–9 times higher than in Lake IJsselmeer. These contents in this deposit in Lake IJsselmeer are 2–4 times higher than those in the older sandy sediments in this lake. Concentrations of heavy metals, As and PCBs increase with depth to a maximum and then decrease to lower levels or background, corresponding to the historic inputs of the river during the past five decades. With increasing distance from the river mouth (Lake Ketelmeer) to Lake IJsselmeer a decrease of the degree of pollution for this young layer is found. Internal carbonate production and the mixing with eroded sediment from other areas seem responsible for the dilution of this deposit.