Print PageHumans have significantly altered the landscape in urban areas by cutting trees, creating impervious surfaces, and changing drainage patterns resulting in increased volume and velocity of runoff following precipitation events. These changes in runoff have impaired streams and riparian areas that previously played a role in reducing watershed N flux through uptake and denitrification. The primary method used to control stormwater discharge is stormwater control measures (SCM) such as retention basins. Although the SCMs were designed to mitigate hydrologic impacts associated with urban development how these compare to natural riparian areas in their ability remove N is not well known. In this study we compare potential denitrification in five types of stormwater control measures (wet ponds, dry Detention Ponds, dry extended detention, Infiltration Basin, and filtering practices) and two types of riparian areas (forested and herbaceous) in Baltimore Md.
Results/Conclusions
Denitrification enzyme activity was higher in the in the stormwater control measures (1.2 mg N kg-1 hr-1) than in the riparian areas (0.4 mg N kg-1 hr-1). Denitrification enzyme activity was highly correlated with soil moisture, soil organic matter, microbial biomass, and soil respiration in both stormwater structures and natural riparian areas. However, under equivalent levels of soil moisture, soil organic matter, microbial biomass, and soil respiration denitrification enzyme activity in stormwater structures was higher than in riparian areas. Stormwater control structures appear to function as hotspots of denitrification in the landscape and have higher potential denitrification compared to the natural riparian areas despite their having similar amounts of microbial biomass. This higher potential denitrification is likely due to the engineered nature of the structures facilitating the interaction between soil and the nitrate-laden runoff.
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