Seasonal Variation in Floodplain Biogeochemical Processing in a Restored Headwater Stream

Environ Sci Technol. 2015 Nov 17;49(22):13190-8. doi: 10.1021/acs.est.5b02426. Epub 2015 Oct 28.

Abstract

Stream and river restoration activities have recently begun to emphasize the enhancement of biogeochemical processing within river networks through the restoration of river-floodplain connectivity. It is generally accepted that this practice removes pollutants such as nitrogen and phosphorus because the increased contact time of nutrient-rich floodwaters with reactive floodplain sediments. Our study examines this assumption in the floodplain of a recently restored, low-order stream through five seasonal experiments. During each experiment, a floodplain slough was artificially inundated for 3 h. Both the net flux of dissolved nutrients and nitrogen uptake rate were measured during each experiment. The slough was typically a source of dissolved phosphorus and dissolved organic matter, a sink of NO3(-), and variable source/sink of ammonium. NO3(-) uptake rates were relatively high when compared to riverine uptake, especially during the spring and summer experiments. However, when scaled up to the entire 1 km restoration reach with a simple inundation model, less than 0.5-1.5% of the annual NO3(-) load would be removed because of the short duration of river-floodplain connectivity. These results suggest that restoring river-floodplain connectivity is not necessarily an appropriate best management practice for nutrient removal in low-order streams with legacy soil nutrients from past agricultural landuse.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Agriculture
  • Ecosystem
  • Environmental Restoration and Remediation / methods*
  • Floods
  • Nitrates / analysis
  • Nitrogen / analysis*
  • Phosphorus / analysis
  • Rivers*
  • Seasons
  • Soil
  • Virginia

Substances

  • Nitrates
  • Soil
  • Phosphorus
  • Nitrogen