The sampling was conducted in autumn 2012 during low tides. Sediment samples were taken both at the intertidal and 150 m upstream (except for LC), in order to determine the sediment particle size distribution, organic matter content and PCB analysis. Samples were dried in an oven at 60 C until constant weight. Organic matter content was determined from the weight loss after incineration in a muffle at 500 C during 4 h, whilst particle size distribution was determined through sieving (Carver, 1971).