三岔河梯级水库生源要素的时空变化特征

氮磷硅等生源要素是影响水体初级生产力、水生态系统结构与功能的重要因素。为了解梯级水库-河流体系营养盐的时空变化特征,对三岔河梯级水库(平寨水库、普定水库、引子渡水库)及入库河流进行了季度调查,分析了其氮、磷、硅营养盐浓度及其相关环境因子。结果显示,溶解硅(DSi)、总溶解氮(TDN)、PO_4~(3-)浓度分别为049～381、212～498、064～761×10~(-2)mg/L,平均值分别为199、325、003 mg/L。TDN和PO_4~(3-)浓度季节性变化较为明显,但空间变化较小;DSi的时空变化均较为显著。TDN浓度夏季较高,而PO_4~(3-)浓度春、冬季较高。TDN与叶绿素显著正相关,而PO_4~(3-)与温度显著负相关,表明两者的影响因素不同。DSi浓度水平沿程依次降低,主要受生物作用控制。DSi浓度随水体深度增加而增加,秋季尤为显著;而TDN和PO_4~(3-)在剖面上的变化因季节和水库的不同而不同。

Spatiotemporal Variations of Nutrients in Cascade Reservoirs along the Shancha River

Nutrients, such as nitrogen, phosphorus and silicon, are important factors affecting the primary productivity and the structure and function of the aquatic ecosystem. In order to understand the spatiotemporal variation of nutrients in cascade reservoir-river systems, we investigated seasonal variations of nitrogen, phosphorus and silicon and related environmental factors in the mainstream of the Sancha River and cascade reservoirs (Pingzhai, Puding and Yinzidu reservoirs) on the river. The results showed that concentrations of dissolved silicon (DSi), total dissolved nitrogen (TDN) and concentrations of PO₄^3- varied in the ranges of 0.49-3.81 mg/L, 2.12-4.98 mg/L, 0.64-7.61×10^-2 mg/L, respectively, with the averages of 1.99 mg/L, 3.25 mg/L and 0.03 mg/L, respectively. The seasonal variations of TDN and PO₄^3- concentrations were remarkable, but their spatial variations were relatively small. Meanwhile, spatiotemporal variations of DSi were significant. TDN were high in summer, while concentrations of PO₄^3- were high in spring and winter. TDN correlated positively and significantly with chlorophyll, and PO₄^3- concentrations correlated negatively with temperature, indicating that their influencing factors were different. The DSi concentration, which was mainly controlled by biological activity, decreased along the mainstream of the river. The DSi concentration increased with the water depth, especially in autumn, but variations of TDN and PO₄^3- along the water profile varied differently in different seasons and different reservoirs.