Applications

This experiment has direct applications to wetlands constructed to filter rivers or streams with high nitrate concentrations as a result of agricultural runoff. A wetland with a large biomass and water volume will greatly reduce the nitrate concentrations in the water; however, these same conditions may also stimulate the production of large quantities of greenhouse gases. The tradeoff between the quantity of gas produced and the quantity of nitrate removed from the water must be recognized, and taken into consideration when the wetland is designed. For example, high saturation combined with the presence of nitrogen in a wetland environment favours the production of nitrous oxide. Therefore, if the correct measures are not taken to promote the uptake of nitrates by macrophytes, they will be denitrified and emitted as nitrous oxide. Nitrous oxide has a very high Global Warming Potential, and if nitrate-filtering constructed wetlands were to be implemented on a large scale, the quantities of N2O they would emit must be controlled and monitored. Otherwise, one could argue that the many environmental benefits of constructed wetlands would not compensate for their contribution to the rising global warming problem.