Spatial variability of metal pollution in groyne fields of the Middle Elbe – Implications for sediment monitoring

High spatial heterogeneity of physical and chemical sediment properties was observed in both horizontal and vertical directions of deposits in a groyne field of the Middle Elbe. The respective sediment cores were less polluted on the top compared to consolidated deeper layers, indicating a decreasing trend of contamination in the river basin. In contrast to water quality monitoring, the impact of the large Elbe flood in 2002 was still visible in the deeper layers (5–30 cm) of the groyne field sediments six years after the event. Due to the fact that the environmental risk increases with erosion potential of discharge and contamination level of sediments, monitoring for environmental risk must capture not only surface sediments but also deeper layers up to an anticipated erosion depth. - Highlights: ► High spatial variability of physical and chemical sediment properties was observed. ► Depth depending patterns in sediment pollution were found. ► The patterns reveal the main pollution sources. ► Three main structures (top, barrier, consolidated layer) were indicated in the cores. ► Impact of the large Elbe flood (2002) is still visible in deeper sediment layers. - Monitoring of contaminated river sediments must capture layers up to an anticipated erosion depth.