模拟人工湿地中植物多样性对铵态氮去除的影响

为了研究植物多样性对人工湿地生态系统的氮去除功能和硝化作用的影响,在模拟人工湿地中配置了单种和4种植物混种2个处理,并以铵态氮为唯一入水氮源负荷。结果表明:混种系统出水中的无机氮浓度显著低于单种系统(分别为3.41和7.20mg·L-1,P<0.05),铵态氮浓度也显著低于单种系统(分别为1.35和4.11mg·L-1,P<0.05);而出水硝铵浓度比(NO3-∶NH4+=1.55)则高于(P<0.05)单种系统(0.80),说明多样性增强了系统的硝化作用;混种系统基质的无机氮存留量(1455mg·m-2)低于(P<0.05)单种(2235mg·m-2),说明混种系统中可能存在资源的互补利用;根据物质平衡法推算出混种系统中植物总的氮吸收量对无机氮去除的贡献率(48%)大于(P<0.05)单种(31%),植物的可移除部分(地上)对无机氮移除的贡献率也呈现此规律(混种和单种分别为33%和20%,P<0.05);基质氮存留在2种系统中的贡献率则与植物吸收规律相反(混种和单种分别为5%和9%,P<0.05);混种系统中的反硝化作用、氨挥发和微生物的氮固持等对氮去除的贡献率低于单种系统。

Effects of plant diversity on ammonium removal in simulated constructed wetland

To understand the effects of plant diversity on the nitrogen removal and nitrification in constructed wetlands, simulated constructed wetlands with monoculture and mixed planting of four kinds of plants were constructed, and ammonium nitrogen was taken as the sole inflowing nitrogen loading. In the mixed planting system, both the effluent inorganic nitrogen concentration and the effluent ammonium nitrogen concentration were lower than those in the monoculture system (3.41 mg·L-1 vs. 7.20 mg·L-1, and 1.35 mg·L-1 vs. 4.11 mg·L-1, respectively; P<0.05), but the ratio of NO3-/NH4+ concentration was greater than that in the monoculture system (1.55 vs. 0.80, P<0.05), indicating that mixed planting enhanced the nitrification in the simulated constructed wetlands. The substrate inorganic nitrogen accumulation in the mixed planting system was lower than that in the monoculture system (1455 mg·m-2 vs. 2235 mg·m-2, P<0.05), suggesting that the complementary resource use might occur in the mixed planting system. Based on the mass-balance approaches, the plant nitrogen uptake in the mixed planting system had a greater contribution rate to the total inorganic nitrogen removal than in the monoculture system (48% vs. 31%, P<0.05), and the nitrogen removal by the plant aboveground parts also presented the similar trend (33% vs. 20%, P<0.05). The substrate nitrogen accumulation had an opposite trend to the plant nitrogen uptake, with 5% in mixed planting system and 9% in monoculture system (P<0.05). As compared with those in monoculture system, the denitrification, ammonia volatilization, and microbial nitrogen immobilization in the mixed planting system had lower contribution rates to the nitrogen removal.