潜流型人工湿地的脲酶活性分布特性

Distribution characteristic of urease activity in subsurface constructed wetlands

试验考察了潜流型人工湿地中脲酶活性的分布特性,分析了脲酶分布与湿地植物、微生物状态及污水处理效果间的关系,揭示了潜流湿地的脱氮机制.结果表明:潜流湿地中含氮污染物的去除以生物降解为主要途径,脲酶活性与TN去除率显著相关;各潜流湿地中,有植物湿地脲酶活性高于空白湿地,芦苇湿地高于美人蕉湿地,垂直流湿地与水平流湿地无明显差异;潜流湿地的脲酶活性与微生物数量及活性紧密相关;湿地各层的脲酶活性均沿程下降,中、上层明显高于下层;植物根系分泌物直接影响脲酶活性,使其由根面至非根区递减.芦苇根际脲酶活性高于美人蕉,新生根根际明显高于老根;潜流湿地脲酶活性受温度变化影响,低温不利于微生物生长繁殖,使湿地脲酶活性降低.

The distribution characteristic of urease activity in subsurface constructed wetlands and its correlation with activity states of plant and microorganism, and wastewater purification effects were studied. Furthermore, nitrogen removal mechanism in subsurface wetland was disclosed. Results show that biodegradation is the dominating approach to remove nitrogenous contaminations in subsurface wetland. Thereby, urease activity is remarkably correlative with total nitrogen removal efficiency. It can be used as one of the important indexes to reflect nitrogen removal effect and select wetland plants. Among experimental wetlands, urease activity in planted wetlands is higher than unplanted wetland; wetlands planted with reed higher than that with canna. However, there is no obvious difference between vertical flow wetland and horizontal flow wetlands. Urease activity in subsurface wetlands is closely interrelated with the magnitude and activity of microorganism. It decreases gradually with distance in every layers of subsurface wetland and is higher in upper and middle layer than that in lower layer. Therefore, the former layers can be considered as the most available regions for pollutants purification in subsurface wetland. The secretion from plant roots results directly in the gradual decrease of urease activity from root surface to non-root-area. The urease activity around reed roots is higher than that around canna roots, and that around fresh roots is higher than that around old roots. Besides, urease activity is influenced remarkably by season changing. Low temperature is disadvantageous to the growth of microorganism and urease activity.