乌江渡水库中溶解性硅的时空分布特征

Spatial-temporal variation of dissolved silicon in Wujiangdu reservoir

在2003年10月-2004年9月期间每月一次采集了乌江干流上乌江渡水库大坝前开阔水域中的表层水;并于2003年10月、2004年4月和7月在同一采样点采集了分层水样及其底部的柱状沉积物.分别测定了其中溶解性硅（DSi）和叶绿素a（Chl-a）的浓度, 同时还现场测定了水体中的温度（T）, 溶解氧（DO）和pH值.结果表明：乌江渡水库表层水中DSi的浓度范围为0.53～3.96 mg/L,平均值为1.74 mg/L;但沉积物孔隙水中DSi浓度大约是上覆水体中DSi浓度的7倍.分层期间,水体中DSi浓度在垂直方向上随水深增加而升高,而孔隙水中DSi浓度随沉积深度先增加后降低.同时还发现乌江渡水库中DSi与叶绿素a之间存在较好的反相关关系,这表明该水库中DSi的含量和分布可能主要受到浮游植物尤其是硅藻的生物活动调节.

Wujiangdu reservoir is located at the mainstream of Wujiang river, the biggest tributary in the upstream of Yangtse River. The surface water was collected monthly near the dam of Wujiangdu reservoir from Oct 2003 to Sept. 2004. The water sample and sediment cores were at the same station in （December） 2003, and April and July 2004 respectively. The concentrations of the dissolved silicon （DSi） in the water column and the porewater were determined, and the （Chl-a） concentrations of chlorophyⅡ-a in the water column were analyzed. Other parameters such as temperature and dissolved oxygen were measured in situ. The result shows that the DSi concentration in the surface water ranged from 0.53 to 3.96 mg/L, with average of 1.74 mg/L; and the DSi concentration in the porewater is about 7 times higher than the overlying water. The DSi concentration in the stratified water bodies increases with their depths, compared with the increase of porewater, firstly, and then decrease with its depth. The good inverse relationship between DSi and Chlorophyll a suggests that the variation of DSi concentration in Wujiangdu reservoir is determined by the biological activities.