## 3 Results  
### Nitrogen Treatment by Dry Detention Basin and Wetland  
The median flow weighted TDN concentrations at the inlet and the outlet of the dry detention basin were identical (0.47 mg L\({}^{-1}\)) (Figure 5). During 39% of sampling events, the outflow concentrations were higher relative to inflow (Figure 6). The highest TDN removal rate for the basin occurred during May of 2018. Inflow and outflow from the basin were sampled during a few different May storms, producing between 0.2 and 2.4 cm of rain, and the median treatment efficiency was 64%. The lowest TDN removal rate for the basin occurred a few months later during the summer of 2018. Inflow and outflow were associated with 3 different storms in July, producing between 1.3 and 4.3 cm of rain and resulting in TDN exports four times greater than the inflow. These more intense, larger rain events quickly flushed through the basin with little opportunity for nitrogen transformations. Overall, the median flow weighted NO\({}_{3}\)-N concentration at the outlet (0.13 mg L\({}^{-1}\)) was about 13% lower than at the inlet (0.15 mg L\({}^{-1}\)). During 61% of events, the inlet concentrations of NO\({}_{3}\)-N were higher than the outlet. Median flow weighted NH\({}_{4}\)+N concentrations at the inlet (0.17 mg L\({}^{-1}\)) were 17.6% higher relative to the outlet (0.14 mg L\({}^{-1}\)) and during 54% of sampling events, the inflow concentrations were higher than the outflow. However, there was no statistical significance (\(p>0.05\)) between inflow and outflow concentrations for any of the nitrogen species. These data suggest that overall, the dry detention basin was not effective at treating any form of dissolved nitrogen. Figure 5: Boxplots of flow-weighted concentrations of total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), nitrate (NO\({}_{3}\)-N), and ammonium (NH\({}_{4}\)+N) at the inlet (I) and outlet (O) of the dry basin (B) and wetland (W). Letter changes indicate significant intra-control measure differences in concentrations. The number of changes indicate significant inter-control measure differences in concentrations. Statistical outliers indicated by (*). The median flow weighted concentration of TDN at the wetland outlet (0.18 mg L\({}^{-1}\)) was 63% lower relative to the inlet (0.49 mg L\({}^{-1}\)), and during 87.5% of sampling events, the outflow concentration of TDN was lower than the inflow. The highest TDN removal rate for the basin occurred in April of 2019 during a 2.1 cm rain event. Outflow concentrations were 94% lower relative to inflow during that period. The lowest median TDN removal rates occurred in February of 2020. Median outflow concentrations of TDN associated with storms producing between 0.4 to 4.3 cm of rain were 15% lower relative to inflow. Overall, the wetland was a sink for NH\({}_{4}\)\({}^{+}\)N and NO\({}_{3}\)\({}^{-}\)N during 75% and 87.5% respectively, of sampling events. Median inflow concentrations of NH\({}_{4}\)\({}^{+}\)N (0.12 mg L\({}^{-1}\)) and NO\({}_{3}\)\({}^{-}\)N (0.30 mg L\({}^{-1}\)) were higher relative to outflow concentrations (0.04 mg L\({}^{-1}\) of NH\({}_{4}\)\({}^{+}\)N; 0.06 mg L\({}^{-1}\) of NO\({}_{3}\)\({}^{-}\)N). Differences in concentrations of NO\({}_{3}\)\({}^{-}\)N in the outflow and inflow were statistically significant (\(p\) = 0.025), but differences in NH\({}_{4}\)+N were not (\(p\) = 0.079). Both NH\({}_{4}\)\({}^{+}\)N and NO\({}_{3}\)\({}^{-}\)N are biologically reactive species of nitrogen, and together comprise dissolved inorganic nitrogen (DIN). There were statistically significant differences (\(p\) = 0.016) in concentrations of DIN when comparing inflow (0.46 mg L\({}^{-1}\)) and outflow (0.09 mg L\({}^{-1}\)). Outflow DIN concentrations were lower than inflow concentrations during 87.5% of sampling events. Inflow DIN concentrations for the dry detention basin (0.32 mg L\({}^{-1}\)) were not significantly different (\(p\) = 0.385) than inflow DIN concentrations for the wetland (0.47 mg L\({}^{-1}\)).