苦草不同生命阶段对水体、底泥中氮迁移转化的影响

Effect of Different Life Stage Vallisneria natans( Lour. ) Hara on Migration and Transformation of Nitrogen in Water and Sediment

沉水植物的生长发育、衰亡过程会对水体中氮循环产生一定影响。为了研究氮在水体-底泥-沉水植物系统中的迁移转化规律,构建了人工模拟的水体-底泥-沉水植物(苦草)系统,连续270 d测定了苦草整个生命周期内水体、底泥、苦草中总氮(TN)及各形态氮浓度的变化。结果表明,在苦草生长期的前90 d中,苦草生物量增长了近30倍,水体和底泥中的TN浓度都有所降低;90 d之后苦草陆续进入衰减期及腐解期,整个体系的TN浓度持续下降,在第180天时苦草组的水体及底泥TN浓度都小于空白组。至试验结束的第270天,苦草已经完全腐解,底泥中TN浓度比第180天下降了9.11%,但水体中的TN浓度与第90天时相当,是第180天的2.42倍。苦草组底泥及苦草中的NH+4-N和NO-3-N浓度在试验周期内变化较大,NH+4-N和NO-3-N在生长期由底泥迁移到苦草中,被植物吸收和利用,随着苦草的逐渐衰亡腐解,NH+4-N和NO-3-N大量释放,一部分沉积在底泥中;而空白组NH+4-N和NO-3-N浓度在底泥及水体中波动不大。

The growth and decomposition of submerged macrophytes affects the nitrogen cycle in water body.In order to investigate the migration and transformation rule of nitrogen in the water-sediment-submerged macrophytes system, a simulated system was constructed. The changes of nitrogen in water, sediment and submerged macrophytes （Vallisneria natans（Lour.）Hara, V.natans） as well as its migration and transformation in the life cycle of V.natans were studied for 270 days.The results show that the biomass of V.natans increased by more than 30 times in the first three months, and the total nitrogen （ TN） amount in water and sediment decreased.After 90 days, V.natans grew slowly and stepped into decaying stage and TN of the whole system decreased gradually. TN in both water and sediment from the group with V.natans was less than that of the control group in the 180th day.In the 270th day, the decomposition rate of V.natans reached 100% and TN in sediment decreased by 9.11%compared with that in the 180th day, while the content of TN in water was similar to that of the 90th day, and was 2.42 times as that in the 180th day.NH4＋-N and NO3--N in water and sediment of the control group fluctuated slightly, whereas those in sediment and plant of the group with V.natans changed greatly.During the growth period, NH4＋-N and NO3--N in sediment transferred into V.natans, while they were released in a large amount during decomposition process of V.natans, some of which deposited into sediment.