岸边带湿地对富营养化河流的净化作用研究

对北运河上游污染严重流域实地调查发现,水中TN、TP和NH4+-N的最大超标倍数分别为12、10和7,以NH4+-N污染为主要特征.对北运河流域沙河水库附近一处典型岸边带湿地进行深入研究发现,天然河流岸边带湿地系统对河水中NH4+-N、TN和TP浓度有明显的削减作用,分别由河水中的27.0、29.0、1.82mg·L-1降至湿地中的2.50、6.54、0.12mg·L-1.由于微生物驱动的硝化-反硝化脱氮作用以及岸边带植物对营养元素的吸收作用,植被型岸边带沉积物中NH4+-N、TN和OM含量(分别为23.0mg·kg-1,0.66g·kg-1和9.13g·kg-1)分别为裸露型岸边带沉积物的0.20,0.48,0.67倍.植被型岸边带沉积物各层C/N比(平均为8.68)是裸露型岸边带沉积物各层C/N比(5.53)的1.6倍,为反硝化作用的发生提供了相对充足的碳源.与裸露型岸边带相比,植被型岸边带更利于营养元素的去除.作为工程实例,模拟天然河流岸边带湿地的罗马湖旁路/离线人工湿地系统对水体营养元素有显著的去除作用.

The purification function of riparian wetlands on the eutrophicated river

According to the water quality investigation of the upstream of the North Canal, the concentrations of total nitrogen, total phosphorus and NH₄⁺-N exceeded their respective standard for 12, 10 and 7 times, respectively, and NH₄⁺-N is the main pollutant in the North Canal. Further studies were carried out in a typical riparian wetland near Shahe Reservoir of the North Canal. The results showed that the concentrations of NH₄⁺-N, TN and TP in the natural riparian wetland (2.50,6.54,0.12 mg·L^-1, respectively) decreased greatly compared with that of river water. The average contents of NH₄⁺-N, TN and OM of the macrophyte-covered riparian zone (MRZ) sediment (23.0 mg·kg^-1, 0.66 g·kg^-1 and 9.13 g·kg^-1, respectively) were 0.20, 0.48 and 0.67 times lower than that of bare riparian zone (BRZ) sediment, respectively. The main reasons were the coupled nitrification / denitrification drived by microbes and the absorption of nutrient elements by riparian plants. The average C/N ratio in the MRZ sediment was 1.6 times higher than that of BRZ, which supplied relatively sufficient carbon source for denitrification. In contrast to BRZ, MRZ was more favorable for nutrient element removal. As a demonstration of simulating natural riparian wetland, Luomahu Lake constructed wetland showed obvious removal effect of water nutrient elements.