Riparian wetland creation has been proposed as a means to mediate aquatic nitrate (NO₃^-) pollution from non-point runoff.  Excess nitrate concentrations are known to cause hypoxia in the Gulf of Mexico and other important water bodies.  Denitrification by the anaerobic microbial community in wetland soils results in the permanent removal of NO₃^- through reduction to NO, N₂O, and N₂.  Denitrification rates were quantified using the in situ acetylene inhibition technique at 27 locations in four wetland/riverine sites at the Olentangy River Wetland Research Park, Columbus, OH for one year.  Sites included two created flow-through experimental wetlands, one created flow-through oxbow experiencing naturally pulsing hydrology, and one bottomland forest/river-edge site.  Points were spatially distributed at inflows, center, and outflows to include permanently flooded open water, intermittently flooded transitions, and upland.  

Results/Conclusions

Initial data show higher denitrification rates in permanently flooded zones (for the center of one experimental wetland, annual open water rates were 446.01 ± 130.78 µg N₂O-N m^-2 h^-1, transition zone rates were 89.67 ± 52.90 µg N₂O-N m^-2 h^-1) peaking in spring during the period of highest nitrogen fertilizer application and runoff (for the months of April-June, rates were 956.95 ± 365.57 µg N₂O-N m^-2 h^-1 in the permanently flooded zone).  The impact of temperate riparian wetland creation on greenhouse N₂O emissions needs to be balanced with the important ecosystem service of nitrate removal.