三峡水库蓄水过程中神农溪库湾营养盐的动态分布

The Dynamic Distribution of Nutrients in Shennong Bay in the Impoundment of the Three Gorges Reservoir

基于2013年9-11月神农溪库湾水动力过程及营养盐变化连续监测数据,研究三峡水库蓄水期干流倒灌这一特殊水动力过程对支流库湾营养盐分布的影响。结果表明:在蓄水过程中,干流水体分别以表层、中层和底层异重流的形式倒灌入神农溪库湾,蓄水第一阶段库湾上游区域的(N/P)介于10到22之间,上游区域暴发水华的风险大于下游;第二阶段库湾中TP浓度由最初的0.056 mg/L上升至0.11 mg/L,TN浓度由1.30 mg/L上升到2.02 mg/L,库湾(N/P)几乎都集中在14到20之间,满足藻类生长的最佳条件,水华暴发风险最大;第三阶段TP由0.11 mg/L降至0.049mg/L,TN由2.02 mg/L降至1.77 mg/L,整个库湾(N/P)>22,此阶段由于磷营养盐的限制,相较于前两个阶段水华暴发的风险明显降低。

Based on the data of continuous measurement of hydrodynamics and nutrients of the Shennong Bay obtained during September and November 2013, the goal of this study is to investigate the effect of reverse density flow on nutrients distribution of the Shennong Bay during impoundment of Three Gorges Reservoir. The results show that during impoundment, the water backward flow from the main stream into Shennong Bay respectively by surface layer, middle and bottom in the form of density flow. The N/P ratio at the upstream of the Shennong Bay ranged froml0 to 22 during the initial stage of impoundment, indicating a higher risk of algal bloom at the upstream compared to the down-stream. The TP concentration of the bay increased from the initial 0.056 mg,/L to 0.11 mg/L, the TN concentration increased from 1.30 mg/ L to 2.02 mg/L during the second stage of impoundment, the bay was characterized by the N/P ratio of 14- 20 which was ideal for algal growth. The TP concentration of the bay dropped from 0.11 mg/L to 0.049 mg/L, the TN concentration dropped from 2.02 mg/L to 1.77 mg/ L during the third stage of impoundment, indicating the highest risk of algal bloom. The third stage of impoundment was characterized by negligible water level changes and the N/P ratio 〉 22, indicating a reduced risk of algal bloom compared to the previous two stages due to the restriction of phosphorus nutrient.