Low nitrogen and phosphorus release from sediment deposited on a Danish restored floodplain

Abstract

River floodplains and riparian areas are often considered efficient traps for sediment and sediment-associated nutrients such as nitrogen (N) and phosphorus (P). However, few studies have focused on the fate of sediment-bound N and P after deposition on floodplains. In this study, the leaching of N and P from sediment deposited on a Danish-restored floodplain was quantified by placing trapped sediment samples under a rainfall simulator and exposing them to in situ temperatures and precipitation for two months. The nitrate release was 2.72-1600 μg NO 3-N.g -1 DW which corresponded to 0.06-6.42% of the total nitrogen contained in the sediment. Total dissolved phosphorus (TDP) release was 0.44-3.17 μg P.g -1 DW, corresponding to 0.021-0.065% of the TP content of the sediment. Our results indicate that N and P release from floodplain sediment subjected to rainfall events is very low, which should be considered when applying floodplain restoration to mitigate the load of N and P to rivers. © EDP Sciences, 2011.