水葫芦对滇池底泥氮磷营养盐释放的影响

为了探讨水葫芦对富营养湖泊底泥氮磷营养盐释放的影响,通过原位采集滇池柱状底泥,以蒸馏水为上覆水,进行了25d的室内静态模拟实验。实验比较了水葫芦处理组和空白对照组底泥氨氮（NH4-N）、硝态氮（NO3^-N）、溶解性总氮（DTN）、正磷酸盐（PO4^3--P）等的释放特征。结果表明,与对照组相比,水葫芦处理组上覆水溶解氧、pH显著性降低,而PO4^3-P浓度显著性升高;在实验前2d,水葫芦处理组上覆水NH4^＋N和DTN浓度显著性高于对照组,而在5～25d时,其显著性低于对照组。根据上覆水营养盐浓度、水葫芦植株吸收营养盐总量,推算底泥氮磷营养盐释放的平均速率,表明水葫芦加速了滇池底泥氮、磷营养盐的释放速率,处理组氮、磷释放速率分别为对照组的5．3～170．2和1．5～21．6倍。

Effects of water hyacinth (Eichhornia crassipes) on release of nitrogen and phosphorus from sediment of Lake Dianchi

To evaluate the effects of water hyacinth (Eichhornia crassipes) on release of nitrogen and phosphorus from sediment, a 25-day laboratory experiment was carried out. The sediment was taken from Lake Dianchi and was covered by water with water hyacinth as treatments and by water only as controls. Released nutrients such as ammonia, nitrate and dissolved total nitrogen, orthophosphate from the sediment were compared between treatments and controls. Results showed that dissolved oxygen and pH significantly decreased and orthophosphate significantly increased in treatments compared to controls (P<0.05). During the first two days of the experiment, ammonia and dissolved total nitrogen in treatments were significantly (P<0.05) higher than in controls. However, from the fifth day forward, the results were inversed. The average release rates of nitrogen and phosphorus were calculated based on the concentrations of nitrogen and phosphorus in overlying water and total contents of nitrogen and phosphorus absorbed by water hyacinth. The results showed that water hyacinth accelerated the release rates of nitrogen and phosphorus from the sediment. The release rates of nitrogen and phosphorus released were 5.3~170.2 and 1.5~21.6 times higher in treatments than in controls respectively.