水文地貌分区下鄱阳湖丰水期水质空间差异及影响机制

在2011年7月鄱阳湖丰水期水质参数采样分析的基础上,结合Delft3D水动力模型结果,针对鄱阳湖湖区建立了8个水文地貌分区,分析了丰水期总悬浮泥沙(TSS),总磷(TP)、总氮(TN)与叶绿素a(Chla)浓度的空间分布特征,研究了各分区下的水质因子之间的关系.结果表明,鄱阳湖丰水期平均TSS浓度为33.65mg/L,远高于2003年以前10mg/L的平均浓度水平;平均氮、磷营养盐浓度分别为1.61mg/L及0.075mg/L,已达到并远远高于富营养化发生条件,而平均Chla浓度为5.99μg/L,并未达到富营养化湖泊水体临界值.Chla与其他各水质因子无显著相关性,而高泥沙浓度区域的TP与TSS呈现显著相关性.在不同鄱阳湖水文地貌分区下,高强度湖泊采砂活动的北部高流速水域TSS浓度高于河口三角洲水域3倍;TN,TP营养盐浓度表现为流域面源污染负荷大的赣江,饶河河口三角洲水域≥高强度湖泊采砂活动的北部高流速水域>流域污染负荷较小的修水河口三角洲水域及中部湖心水域.Chla则受营养盐浓度水平与水动力因素共同作用而表现为河流交换速度慢且高营养盐浓度水域>水流交换速度快且高营养盐浓度水域>水流交换速度慢且低营养盐浓度水域,其中饶河信江潼津河河口三角洲水域Chla浓度最高,平均水平达到12.53μg/L,超过了富营养化水体的临界值.

Spatial distribution of water quality and its impacting factor in the wet season of Poyang Lake using the hydro-geomorphological partitions

Based on the in situ measurements from the field survey in July, 2011, the objective of this paper was to investigate the spatial distribution of the total suspended sediment (TSS), total nitrogen (TN), total phosphorus (TP), and chlorophyll a (Chl a), where their impacting factors were also studied by dividing the lake into 8 hydro- geomorphological partitions considering the hydrodynamic conditions. Results show that the TSS concentration was 33.65mg/L, which was three times higher than that of the average conditions before 2003. The N, P concentrations were 1.61mg/L and 0.075mg/L respectively, which appears much higher than the requirements of eutrophication. The average Chl a concentration was 5.99 μg/L, which was smaller than the threshold of being a eutrophic lake. Correlation analysis showed that TP and TSS were significantly correlated with each other in high sediment concentration regions, while no significant correlation was observed between the Chl a and other water quality parameters. In different hydro-geomorphological sections, due to pollution inputs from the watershed and sand mining activities within the lake, the TSS concentration of the northern high velocity water regions was three times higher than the river estuary area. TN and TP concentrations of the Ganjiang and Raohe river estuary area was larger than the northern high velocity water regions, where Xiuhe River estuary area andsome central lake area showed minimum TN and TP concentration. The hydrodynamics also played an important role in regulating the spatial distribution of TSS, TN, TP and Chl a in the lakes, Chl a concentration of the river estuary area was larger than the northern high velocity regions, while the Rao-Xin-Tong Jin River estuary area even reached 12.53μg/L, exceeding the low bound value of being a eutrophic lake.