[Interception Effect of Vegetated Drainage Ditch on Nitrogen and Phosphorus from Drainage Ditches]

In order to effectively intercept and remove nitrogen (N) and phosphorus (P) from agricultural water, Canna glauca, Sparganium stoloniferum, Juncus effusus, Hydrocotyle vulgaris, and Myriophyllum elatinoides were planted in an agricultural drainage ditch. The temporal and spatial variations of the dissolved N and P concentrations were monitored during the whole experimental period. In addition, the contents of N and P in sediments and plants were compared among different plant plots. The results showed the effluent TN and TP concentrations in the vegetated drainage ditch were lower than the surface water environmental quality standards for class IV and class II . The average removal rates of TN and TP in water were 64.3% and 69.7%, respectively. The average sediment interceptions in 2010 and 2011 reached 40,400 kg, containing 52.4 kg of N and 21.4 kg of P. The amounts of sediment N and P in five plant plots exhibited the descending order: Canna glauca > Hydrocotyle vulgaris > Sparganium stoloniferum > Myriophyllum elatinoides > Juncus effuses. The accumulated N and P amounts assimilated by five kinds of aquatic plants reached 7.9 kg · a⁻¹ and 1.4 kg · a⁻¹, respectively. Compared with other plants, Canna glauca and Myriophyllu elatinoides had the highest ratios of above-ground and below-ground tissues, and the strongest absorption capacity of N and P was also observed in these two plants. Therefore, the vegetated drainage ditch has good interception effect on N and P pollutants. Furthermore, Canna glauca and Myriophyllum elatinoides can be considered as the optimal plants for N and P uptake.