滇池凤眼莲种养水域水体理化指标24小时变化规律

在滇池水域选择3个实验点,分别是外草海、老干鱼塘和龙门村,构建围栏控制性种养凤眼莲,用于吸收富集水体氮磷。于凤眼莲旺盛生长期内(2010年8月),每隔3小时监测种养区与对照区水体理化指标,包括气温、水温、pH、溶解氧(DO)、总氮(TN)、氨氮(NH4+-N)、硝氮(NO3--N)、总磷(TP)和磷酸根(PO43--P),分析24 h内水体理化指标的变化规律。结果显示,(1)昼夜变化使得3个实验点水体pH和DO白天高于夜晚。由于气泡浮力机制影响,龙门村水体Chl-a浓度在中午12:00达到最高,在日落后21:00又出现一个高值;(2)外草海种养区NO3--N浓度与TN浓度呈显著的正相关关系,与NH4+-N浓度呈显著的负相关关系,推测是因为凤眼莲可以促进富营养化水体的硝化、反硝化、硝化-反硝化反应的耦合过程。老干鱼塘水体由于pH过高,使得水体NH4+-N浓度明显高于NO3--N浓度;(3)昼夜变化对水体氮、磷浓度并未表现出显著的影响。在野外大水面种养相对小面积的凤眼莲,种养水域内部的氮磷浓度均高于相对较远的对照水域;规模化种养凤眼莲方可有效降低整个水体的氮磷浓度。

24 hour changes rule of physical and chemical indexes in water area of Lake Dianchi with water hyacinth (Eichhornia crassipes) cultivated

In the three experiment points of Waicaohai, Laoganyutang, Longmencun in Lake Dianchi, water hyacinth was cultivated by man-made fence to assimilate nitrogen and phosphorus in water.In order to analyze the changes rule of water physical and chemical indexes in 24 hours, the indexs in planting area of water hyacinth and contrast area were monitored every 3 hours in vigorous growth periods (August 2010) of water hyacinth, including air temperature, water temperature, pH, DO, TN, NH4+-N, NO3--N, TP and PO43--P.The results were shown as follows.(1)The values of pH and DO in day were higher than night in the three experiment points because of diurnal variation, and the concentration of Chl-a in water of Longmencun reached the highest value at 12:00 noon, then reached the other higher value at 21:00 p.m.for bubble buoyancy mechanism.(2) There was a significant positive correlation between the concentrations of NO3--N and TN, and there was a significant negative correlation between the concentrations of NO3--N and NH4+-N in planting area of Waicaohai, maybe because cultivation of water hyacinth could stimulate the nitrification, denitrification and coupling process of nitrification and denitrification reactions.The values of pH in water of Laoganyutang were excessively high, so the concentrations of NH4+-N in water were significantly higher than NO3--N.(3) Diurnal variation didn't show significant effect on the concentrations of nitrogen and phosphorus in water.While relatively very small area of water hyacinth was cultivated in a large lake, the concentrations of nitrogen and phosphorus in planting area of water hyacinth were all higher than the contrast area.Only water hyacinth large-scale cultivated in lake could reduce the concentrations of nitrogen and phosphorus of the whole water.