剑潭大坝蓄水前后东江惠州河段营养盐动态

Dynamical Analysis of Nutrient Salt in Huizhou Reach of Dongjiang River before and after Impoundment of Jiantan Dam

2006～2008年调查了东江惠州河段在剑潭大坝蓄水前后的营养盐分布特征。在调查期间,表层悬浮颗粒物浓度和透明度变幅分别为3.2～123mg/L和0.1～1.5m。在大坝蓄水之前的2006年,由于水力滞留时间不足1d,悬浮颗粒物浓度和透明度空间变化不明显;在大坝正常运行的2008年,由于水力滞留时间延长,悬浮颗粒物浓度由上游向下游呈下降趋势,透明度相应呈上升趋势。蓄水后坝区悬浮颗粒物浓度比蓄水前有所降低,透明度有所升高。TN和TP变幅分别为0.75～4.7mg/L和0.01～0.27mg/L。从空间变化看,在调查期间,TN和TP浓度基本上是下游高于上游;从年间变化看,蓄水后坝区TN和TP浓度比蓄水前有所升高。剑潭大坝蓄水后,水力滞留时间的延长,颗粒物沉降速率的提高并没有导致坝区TN和TP浓度的下降,坝区TN和TP浓度的不降而升可能与覆没植被腐烂降解导致营养盐的释放有关。水库正处于一个营养盐"上升"期。

From April 2006 to December 2008,nine cruises were undertaken in the Huizhou Reach of Dongjiang River to compare the nutrient concentrations before and after impoundment of the Jiantan dam.The concentration of suspended solid(SS)and Secchi disk depth(SD)varied from 3.2 to 123 mg/L and from 0.1 to 1.5 m respectively.Before impoundment,the high inflow rate made both the concentrations of SS and SD show no apparent spatial patterns.However,after impoundment of Jiantan Dam the SS concentration declined from the upstream to the downstream and SD increased from the upstream to the downstream with the longer water retention time.After impoundment,the downstream SS concentration was lower than that before impoundment and SD higher than that before impoundment.Total nitrogen(TN)and total phosphorus(TP)varied from 0.75 to 4.7 mg/L and from 0.01 to 0.27 mg/L respectively.During the investigation,the concentrations of TN and TP increased from upstream to downstream.After impoundment, the downstream concentrations of TN and TP were higher than those before impoundment.Maybe due to the nutrient release from the submerged vegetation,the downstream concentrations of TN and TP didn't decline with longer water retention time and higher sedimentation rate after impoundment.