Bestimmung des Feststoffanteils in Brackwassersuspensionen

Abstract

To quantifiy sediment accumulation rates on marsh islands in Northern Germany (so called "Halligen") PE-Bottles are widely used as sediment traps. These traps supply a brackish suspension consisting of mainly siliciclastic sediment, organic substance, salt, and water. In the long term only siliciclastic material contributes to the increase of the Hallig surface. Three methods to determine the siliciclastic fraction of the sediment trap content were developed, validated with standard materials and applied to real samples of Hallig Langeness and Hallig Hooge from the winter season 2009/2010. Two methods are based on fractionation of the suspension contents and subsequent weighing. As most precise and best suited method for field conditions the so-called pycnometer method could be identified. This method is based on density measurements of saltwater and suspension. To calculate the siliciclastic content mean values for the density of siliciclastic material and organic substance as well as the content of organic substance were measured and subsequently used.