Denitrification Potential in Stormwater Control Structures and Natural Riparian Zones in an Urban Landscape

Humans have significantly altered urban landscapes, creating impervious surfaces, and changing drainage patterns that increase volume and velocity as well as frequency and timing of runoff following precipitation events. These changes in runoff have impaired streams and riparian areas that previously reduced watershed nitrogen (N) flux through uptake and denitrification. Stormwater control measures (SCM) are used most frequently to mitigate these hydrologic impacts. While SCM control runoff, their ability to remove N compared to natural riparian areas is not well-known. In this study we compared potential denitrification [as denitrification enzyme activity (DEA)] in five types of SCM (wet ponds, dry detention ponds, dry extended detention, infiltration basin, and filtering practices) and forested and herbaceous riparian areas in Baltimore, MD. DEA was higher in SCM (1.2 mg N kg^–1 hr^–1) than in riparian areas (0.4 mg N kg^–1 hr^–1). While DEA was highly correlated with soil moisture, organic matter, microbial biomass, and soil respiration areas across sites, it was always higher in SCM at equivalent levels of these variables. SCM appear to function as denitrification hotspots and, despite having similar microbial biomass, have higher potential denitrification than natural riparian areas

Appendix A. Additional information regarding methods used to calculate measures of water flow regulation and tree species composition.

Additional information regarding methods used to calculate measures of water flow regulation and tree species composition

Temperature effect on fluorescence and degradation of RWT and fluorescein.

<p>Mean concentration (µg / L) of rhodamine WT and fluorescein solutions in glass vials in the dark before (20 °C), during (45 °C) and after heating (20 °C). Different letters among bars indicate significant differences among treatments for each dye. Total time of heating = 5 h. Error bars are 1 SE.</p

Effect of natural temperature fluctuations on the degradation of RWT.

<p>Mean concentration (C/C₀ x 100) of rhodamine WT solutions in opaque glass vials exposed to solar radiation over 12 d. Error bars are 1 SE. Dashed lines indicate 95% confidence intervals and dotted lines indicate prediction intervals.</p

Rhodamine WT and fluorescein photodegradation after exposure to solar radiation.

<p>Mean concentration (C/C₀ x 100) of rhodamine WT (A) and fluorescein (B) solutions in glass vials exposed to solar radiation over 17 d (rhodamine WT) or 5 h (fluorescein). Error bars are 1 SE. Dashed lines indicate 95% confidence intervals and dotted lines indicate prediction intervals.</p

Appendix A. A table showing litter disappearance exponential rate constants for sugar maple and red oak litter samples in two exotic earthworm invasion fronts at Arnot Forest (central New York).

A table showing litter disappearance exponential rate constants for sugar maple and red oak litter samples in two exotic earthworm invasion fronts at Arnot Forest (central New York)

Experimental setup.

<p>(1) Set of replicate clear vials containing dye solution, (2) set of replicate opaque vials containing dye solution used as controls, (3) quantum sensor connected to a datalogger, (4) waterproofed iButton temperature logger inside a dye solution vial.</p

Appendix C. An ANOVA table evaluating the effects of litter type, site, and sampling date on litter consumption rates.

An ANOVA table evaluating the effects of litter type, site, and sampling date on litter consumption rates

Appendix B. An ANOVA table comparing the total density and biomass of exotic earthworms samples beneath litter boxes with sugar maple or oak litter in two earthworm-invaded plots in a hardwood forest in central New York.

An ANOVA table comparing the total density and biomass of exotic earthworms samples beneath litter boxes with sugar maple or oak litter in two earthworm-invaded plots in a hardwood forest in central New York

Newcomer et al. 2012 (Ecological Monographs) Organic C and Denitrification in Streams

The file “Newcomer et al. 2012 (Ecological Monographs) Organic C and Denitrification in Streams.xlsx” provides original data from the manuscript. The worksheets are named to correspond with the figures in the manuscript. “Figure 4” has field measurements of nitrate and DOC loads (g ha-1 day-1) and runoff (mm day-1). We measured discharge at Spring Branch and discharge was downloaded from USGS gaging stations at the other sites. “Figure 5” was created using discharge (cfs) downloaded from USGS gaging stations and dividing it by watershed area to get runoff (mm day-1). “Figure 6” has field measurements of mean C:N molar ratios for leaves, periphyton, grass, sediment, and stream particulate organic matter (POM). “Figure 7” has field measurements of 15N and 13C stable isotope signatures for leaves, periphyton, grass, sediment, and stream POM. “Figure 8” has laboratory measurements of denitrification potentials associated with glucose versus nitrate amendments. “Figure 9” has laboratory measurements of denitrification potentials associated with the use of leaves, periphyton, and grass as a carbon source