鄱阳湖多尺度流域磷源输送特征及其生态效应

Transport Characteristics of Phosphorus Sources at the Multi-scale Watershed and the Associated Ecological Effects on Poyang Lake

本文选取鄱阳湖梯级流域内从初级支流到湖区(香溪→架竹河→赣江→鄱阳湖)连通水系线路为研究对象,通过对鄱阳湖流域磷(P)湿沉降及径流过程进行监测,探讨鄱阳湖多尺度流域磷源输送特征及其对浮游植物群落结构的影响.结果表明:①鄱阳湖流域的P浓度呈明显的季节变化,除香溪流域外,其余流域的总磷(TP)、可溶性总磷(DTP)和磷酸根(PO43-)浓度均为枯水期较高,丰水期较低;丰水期时,TP浓度与硅藻密度存在极显著的相关关系,枯水期时,TP浓度与隐藻有极显著的相关关系.②次降雨过程研究表明:不同降雨强度下TP和PO43-的浓度及地表径流通量的大小顺序均为:小雨>中雨>大雨.③丰水年和枯水年的沉降通量存在显著差异,丰水年约为枯水年的2.8倍,P的输出通量呈明显的季节性变化,丰水期大于枯水期;随流域逐级增大,但P输出贡献率未显著增加,说明逐级支流P输送并不是各级流域P的主要来源.

In this study,a cascaded watershed system in the Poyang Lake area was selected as the study site,which ranged from the primary tributaries to the lake area(Xiangxi River→Jiazhu River→Ganjiang River→Poyang Lake).The aims of the study were to monitor the P wet deposition and runoff process in the Poyang Lake area and discuss the P transport characteristics at the multi-scale watershed and its impact on phytoplankton community structure in the Poyang Lake.The results showed that the P concentration in the Poyang Lake area exhibited significant seasonal changes.Apart from the Xiangxi River watershed,the concentrations of total phosphorus(TP),dissolved total phosphorus(DTP),and orthophosphate(PO43-)were higher in the low flow period than in the high flow period at other watersheds.There was a significant correlation between TP concentration and diatom density during the high flow period,and between TP concentration and cryptophyta during the low flow period.The order of the amounts of TP and PO43-transport by runoff under different rain intensities is as follows:light rain>moderate rain>heavy rain.There is a significant difference in the deposition flux between the wet season and the dry season with seasonal change,in which the flux during the wet years was about 2.8 times higher than in the dry years.The export flux of P was also shown to be higher in the high flow than in the low flow period.As watershed size increased,the contribution rate of P export did not increase,indicating that P transported at different scales was not the main source of P in each watershed.