生态沟渠对氮、磷污染物的拦截效应

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

将原农业排水沟渠改建成生态沟,以水生美人蕉、黑三棱、灯心草、铜钱草和绿狐尾藻等为试验植物,通过沟渠水样氮、磷去除的时空变化,各植物区泥沙和植物氮、磷含量的对比,探讨了生态沟渠对农业面源污染的阻控效应.结果表明,生态沟渠出水氮、磷浓度分别低于地表水环境质量标准Ⅳ类和Ⅱ类,整条生态沟渠对水体总氮、总磷的平均去除率分别为64.3%、69.7%.整条生态沟渠2010年和2011年拦截泥沙总量的平均值为40 400 kg,含泥沙氮52.4 kg,泥沙磷21.4 kg;其中各植物段拦截泥沙氮、磷量为水生美人蕉>铜钱草>黑三棱>绿狐尾藻>灯心草.生态沟渠植物每年累积带走的氮、磷量分别为7.9 kg和1.4 kg;5种植物氮、磷吸收量最高的是水生美人蕉和绿狐尾藻,二者的地上生物量与地下生物量比值也远高于其他3种植物.因此,生态沟渠对氮、磷污染物有较好的拦截效应,5种植物中氮、磷吸收效果最好的是水生美人蕉和绿狐尾藻.

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- 1and 1. 4kg·a- 1,respectively. Compared with other plants,Canna glauca and Myriophyllum 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.