农田沟渠挺水植物对N、P的吸收及二次污染防治

Absorption and prevention of secondary pollution of N and P by emergent plants in farmland ditch

生长在农田沟渠湿地中的芦苇和茭草对N、P有很好的吸收能力,芦苇茎叶的N、P含量分别为15.0,1.9g/kg,相当于每年吸收818kg/hm2的N和103.6kg/hm2的P,茭草地上部分的N、P含量分别为17.2,3.8g/kg,相当于每年吸收131kg/hm2的N和28.9kg/hm2的P.对比实验发现,收割区0～20cm深度底泥中的有机质、总氮(TN)、总磷(TP)含量明显低于未收割区,但NH4+-N和NO3--N含量增高.植物收割改善了湿地的透光、透气条件,促进污染物分解转化,造成无机氮含量上升.茭白对氮磷的吸收能力也较高,每年收获后可带走200kg/hm2 N,21.1kg/hm2 P.以人为种植取代野生的芦苇和茭草,可获得很好的净化效果,解决植物的二次污染问题.

Reed (Phragmites communis) and wild rice (Zizania latifolia) grown in ditch wetland have a high ability to absorb N and P. Determined assimilation amount of N are 15.0 g/kg [equal to 818 kg/(hm2×a)] by reed and 17.2 g/kg [equal to 131 kg/(h2×a)] by wild rice. The absorbed amount of P by reed and wild rice are 1.9 g/kg [equal to 103.6kg/(hm2×a)] and 3.8 g/kg[equal to 28.9 kg/(hm2×a)] respectively. The contents of organic matters, TN and TP in sediment of harvested plot in the depth of 0-20 cm were lower than that in non-harvested plot. But the contents of NH4+-N and NO3--N increased. The harvest of plant led to the amelioration of transparency and aeration of wetland and accelerated the decomposition and transformation of organic matters and TN. A commercial crop- Zizania caduciflora Turez Hand-mazt also has good assimilation ability of nutrients. The harvest of it would remove 200 kg/hm2 of N and 21.1 kg/hm2 of P every year. Thus, from the view of water quality improvement, the cultivation of Z. caduciflora instead of wild plants could be a good suggestion to resolve the secondary pollution problem of N and P.