苦草生长对沉积物中磷迁移转化的影响

Abstract

Phosphorus is a very important limiting factor in nutrient cycling. Sediments act as both sinks and sources of phosphorus due to continuous transport of chemical species across the sediment-water interface. The submerged macrophyte has an important influence on the migration and transformation of phosphorus in sediments. In order to investigate the impact of the macrophyte on the transformation of phosphorus in sediment,Vallisneria natans was taken as an example,and the ecological system of water- Vallisneria natans- sediment was constructed in different nutrient levels of sediments. Thevariations of phosphorus and environmental factors were measured during the growing season of Vallisneria natans. The result showed that Vallisneria natans directly and indirectly influenced the migration and transformation of different phosphorus forms in different degree. In addition,the transformation of phosphorus showed different variation tendencies as the sediments depth increased. In oligotrophic sediment( L),moderate eutrophic sediment( M) and eutrophic sediment( H),total phosphorus( TP) showed decreasing trends at various levels. However,the decreasing rate of TP in Vallisneria natans group was larger than that of the control group,and they had,on average,decreased more 11.63,18.50 and 46.25 mg / kg than the control group,respectively. TP had a decreasing trend with increasing depth. The extent and influence of Vallisneria natans on sediment depended on the range of its root action. In oligotrophic sediment and Vallisneria natans group( LV),the root length increased 9.2 cm than the initial value,and it could affect the sediment depth over 6 cm. But they affected the sediments depth within 6cm because they didn' t increase significantly in the root length. There was a significant difference between Vallisneria natans group and the control group( P 0.05). Exchangeable-phosphorus( ExP) and aluminum bound phosphorus( Al-P) of Vallisneria natans group increased with increasing depth,and they were lower than those of the control group in L,M and H. Moreover,the extent of variation in Vallisneria natans group was significantly greater than that of the controls( P 0.05). Iron bound phosphorus( Fe-P) decreased with increasing depth.Fe-P of Vallisneria natans group was higher than that of the control group in vertical direction. Ex-P had,on average,decreased more 0. 065,0. 215 and 1. 483 mg / kg than the control group,respectively. Meanwhile Al-P had on average,decreased more 1.198,2.040 and 2.390 mg / kg than the control group,respectively. But Fe-P had,on average,increased more 8.135,16.689 and 8.598 mg / kg than the control group,respectively. Vallisneria natans affected the sediment depth to10 cm in LV. But it affected the depth within 6 cm in moderate eutrophic sediment and Vallisneria natans group( MV) and eutrophic sediment and Vallisneria natans group( HV). As for Ex-p,there was an significant difference between Vallisneria natans group and the control group in L( P0.01),but there were no significant differences in others( P 0. 05). As for Al-P and Fe-P,there were no significant differences in L,M and H( P0.05).