增氧对粉绿狐尾藻氮素吸收及其底泥微环境的影响

Effects of oxygenation on the nitrogen uptake of Myriophyllum aquaticum and sediment microenvironment

为探明增氧对粉绿狐尾藻氮素吸收及其底泥微环境的影响,本研究以粉绿狐尾藻为材料进行盆栽试验,以不增氧处理为对照(CK),分别设置O1(4 min)、O2(6 min)、O3(8 min)、O4(10 min)4个增氧水平,系统研究了粉绿狐尾藻不同生长时期氮素吸收及其底泥铵态氮、硝态氮含量等的变化规律,揭示了增氧调控底泥微环境、提高粉绿狐尾藻对水体氮污染物降解能力的机理。结果表明:无论增氧与否,粉绿狐尾藻根部和地上部氮素吸收量及植株氮素积累量均随生长时间延长呈逐渐增加趋势,且地上部氮素吸收量均高于根部;与CK相比,生长前期(t_(1)、t_(2)时期)增氧8 min、中后期(t_(3)、t_(4)、t_(5)时期)增氧6 min对应的粉绿狐尾藻氮素吸收与积累量均最大,其中增氧6 min对应t_(5)时期的粉绿狐尾藻植株氮积累量为171.08 mg·株^(-1)。增氧使粉绿狐尾藻生长前期底泥pH值降低,使生长后期有机质含量增加的同时,降低了t_(2)时期底泥硝态氮含量和t_(4)、t_(5)时期铵态氮含量,t_(5)时期底泥硝态氮含量反而增加,促进了t_(5)时期粉绿狐尾藻氮素的吸收与累积。研究表明,增氧通过提高水体溶解氧含量影响底泥pH值和有机质,调控底泥氮的形态转化和向水体中的释放,有效提高了粉绿狐尾藻对污染水体氮污染物的降解能力。

To investigate the effects of oxygenation on nitrogen uptake by Myriophyllum aquaticum and sediment microenvironment, a pot experiment was conducted using Myriophyllum aquaticum as tested material. The control group was treated without oxygenation, and four oxygenation levels of O_(1)(4 min), O_(2)(6 min), O_(3)(8 min), and O_(4)(10 min)were designed. The variation characteristics of nitrogen uptake by plants and the content of ammonium nitrogen and nitrate nitrogen in sediments under different culture periods were systematically studied.The mechanism of oxygenation regulating sediment microenvironment and improving the degradation ability of nitrogen pollutants in water by Myriophyllum aquaticum was revealed. Results showed that, with oxygenation or not, the nitrogen uptake of roots and shoots and the nitrogen accumulation of plants all increased gradually with the extension of culture time, and the nitrogen uptake of shoots was higher than that of roots. Oxygenation significantly promoted the absorption of nitrogen by Myriophyllum aquaticum. Oxygenation for 8 min in the early growth stage(t_(1)and t_(2)periods)and for 6 min in the middle and late growth stage(t_(3), t_(4), and t_(5)periods)corresponded to the maximum nitrogen accumulation of Myriophyllum aquaticum. The maximum nitrogen accumulation of plants in the t_(5)sampling periods was 171.08mg·plant^(-1) with 6 min of oxygenation. Oxygenation resulted in the decrease of the sediment pH in the early growth stages and an increase in the organic matter content of the sediment in the late growth stages. Oxygenation decreased the nitrate nitrogen content in the t_(2)period and the ammonium nitrogen content in the t_(4)and t_(5)periods but increased the nitrate nitrogen content of the sediment in the t_(5)period, thus promoting the absorption and accumulation of nitrogen by Myriophyllum aquaticum. Oxygenation affected the pH value and organic matter of sediment by increasing dissolved oxygen content in water. Thereby, the form transformation of sediment nitrogen was regulated and released to the water body, effectively improving the degradation ability of Myriophyllum aquaticum to the nitrogen pollutants in polluted water bodies.