Figure 1.
A.) Influent concentration experiment (under fully saturated conditions) and B.) Multiple plant species experiment (with saturated zone overlaid by a non-saturated zone). Note diagrams are not drawn to scale.
Table 1.
Summary of experiment details.
Figure 2.
Nitrogen species concentrations.
Examples of time series NH4+, NOx, excess 29N2 and 30N2 concentrations (± standard error (n = 4)) following dosing in the influent concentration experiment under very high nutrient dosing (20 mg N/L) measured in July 2012.
Figure 3.
Rates of denitrification (14N+15N) against inflow TN concentration.
Measured in the influent concentration experiment (± standard error (n = 4)) during July and August. Michaelis-Menten curves were fitted to give Vmax = 861 µmol m−2 h−1 and Km = 8.46 mg L−1 in July and Vmax = 1653 µmol m−2 h−1 and Km = 5.01 mg L−1 in August.
Figure 4.
Division of 15NO3− between denitrification, plant or microbial assimilation and remaining as 15NO3− within the pore water.
Measured 12(non-vegetated) and low, medium, high and very high (vegetated) nutrient dosing rates (n = 4).
Figure 5.
Change in pore water dissolved oxygen.
Dissolved oxygen (% air saturated) (± standard error (n = 3) at base of columns across sampling period. Note the sample collection method introduced up to ∼7% air saturation.
Figure 6.
Division of 15NO3− between denitrification, plant or microbial assimilation or remaining in the pore water.
Results for each biofilter column in the multiple species experiment (3 replicates per species, n = 1).
Figure 7.
Conceptual diagram illustrating nitrate processing.
Removal by assimilation and denitrification at different nitrogen loadings in vegetated and non-vegetated systems. The dependence of denitrifying bacteria on plant-derived carbon is also represented.