Groundwater Nitrate Removal

in Salt Marshes

General Background:

• Salt marshes in the northeast characterized by peat at the marsh surface overlying sands or gravels
• Early studies: Minimal groundwater nitrate processing in these sandy aquifers
• Recent studies: Groundwater denitrification through these sands with high hydraulic conductivity can be substantial as approach coast

What has been our contribution?

Addy et al. 2002
• New method to provide useful insights into spatial and temporal patterns of groundwater denitrification in riparian zones and at the coastal margin

Addy et al. 2005
•  We found substantial groundwater denitrification capacity in the low marsh year-round.
•  Carbon additions did not alter groundwater denitrification suggesting that an alternative electron donor may be limiting.
•  Combining flowpaths with denitrification capacity, we estimated that as much as 29-60 mg N could be removed from 1 L of water flowing through the groundwater below the low marsh, arguing for the significance of salt marshes in annual watershed scale N budgets.

To learn more about our most recent work on groundwater denitrification in filled salt marshes, download this pdf of a powerpoint presentation.