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 mg NO 3 -N.g x1 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 mg P.g x1 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.

Nutrient Retention in Restored Streams and Rivers: A Global Review and Synthesis

“…Alternative methods used for evaluating stream and river restoration included: sediment dynamics, plant dynamics, nitrification, stable isotope ratios, dissimilatory nitrate reduction to ammonia (DNRA), anammox, microbial biomass nitrogen (MBN) and potentially mineralizable nitrogen (PMN). Sediment dynamics ranged from measuring concentrations [61] to N sedimentation and turnover rates [62], and experimentally evaluating changes like N release from sediments deposited on the floodplain [63]. Plant dynamics included measurements of biomass, plant uptake, and nutrient utilization efficiency [64,65].…”