A freeze-coring technique applied to pollution by fine sediments in gravel-bed rivers

Abstract

The substrate of gravel-bed rivers provides a potential sink for fine sediments which may be associated with potentially toxic metals. However, problems of sampling submerged substrates has constrained investigations of channel substrate pollution. This paper illustrates the utility of a freeze-sampling technique for gravel-bed rivers that may be used to obtain quantitative determinations of fine sediments. Potential applications are illustrated by two case studies. The first shows that flood control can lead to the sedimentation and compaction of gravel substrates. The second shows that high metal concentrations can exist within gravel substrates of urban rivers. Both studies demonstrate that the method can be used to establish fine sediment and contaminant profiles for the upper 30 cm of gravel substrates — the critical zone for biota.