Case Studies > Haddam Demonstration Site > Rain Garden > Results > Nitrogen & Phosphorus

Nitrogen & Phosphorus

These analysis of variance (ANOVA) results are for the entire period of study. After one year of monitoring, the "treatment" garden had a modification performed to increase retention of nitrate-N. The results include the effects of this modification. The table shows geometric means with +/- 1 standard deviation. Means followed by the same letter are not significantly different.

Nitrate-N concentrations in underdrain outflow from the treatment garden were significantly (p=0.001) lower than roof runoff concentrations. Ammonia-N concentrations in outflow from both of the underdrains were significantly (p=0.001) lower than roof runoff, precipitation, and overflow concentrations. TN concentrations in underdrain outflow from the treatment garden were significantly (p=0.001) lower than roof runoff concentrations. Interestingly, TP concentrations in underdrain outflow from both gardens were significantly (p=0.001) higher than precipitation, roof runoff, or overflow concentrations. The suspected cause of this was the disturbance of the soils at the beginning of the study. A graph of TP concentrations from the underdrains over time show a decay trend, whereas the roof runoff concentrations remain fairly stable. For the entire study period, no significant differences in the concentrations of ON and TKN were found among bulk deposition, roof runoff, overflow, or underdrain outflow concentrations.

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