乌江中上游水库-河流体系夏秋季N、Si分布特征

测定了乌江中上游的洪家渡至乌江渡水库段水体中总氮、氨氮和溶解态硅等营养物质含量，并现场测定水深、温度、溶解氧和叶绿素浓度等理化参数。研究结果表明：在夏秋水库分层现象不断减弱期间，氮、硅的空间分布受水库生物地球化学作用差异的影响，在空间上具有明显不同的分布特征。流域内地表水总氮含量变化不大，水库内垂直分布也较均一；7至9月份河流和水库表层水体总氮含量平均值呈下降趋势，分别为347、317和 3.00 mg/L。7、8月份水库表层水溶解态硅含量明显低于上下游水体，说明水库生物吸收作用强而导致水库滞留溶解态硅；在垂直剖面上，0～30 m 水体溶解态硅含量随水深增加而增加，30～60 m 溶解态硅含量变化不大，这反映了水库上层水体生物对硅的吸收,和下层水体溶解态硅的吸收和释放平衡。

DISTRIBUTION CHARACTERISTICS OF N,SI IN MIDDLE AND UPPER REACHES OF WUJIANG RIVER IN SUMMER AUTUMN SEASON

he studied area,from Hongjiadu Reservoir to Wujiangdu Reservoir,is located along the middle and upper reaches of Wujiang River.Water samples were collected monthly from July to September in 2007.The concentrations of total nitrogen (TN),ammonia nitrogen (NH+4 N) and dissolved silicon (DSi) were determined.Water depth,temperature,dissolved oxygen and chlorophyll were measured in situ using YSI.Results showed that those reservoirs were in the phase of thermal stratification.This phenomenon was strong in July,and became weaker 〖JP2〗gradually in August and September.Due to their 〖JP〗different biogeochemical behaviors,TN and DSi showed a significant difference in spatial temporal distributions.TN concentrations in the surface water had little variation,and its vertical distribution was also uniform.The average concentrations of TN in surface water showed a tendency to decrease from July to September,with values of 347,317 and 3.00 mg/L,respectively.Compared to TN,the DSi concentrations in the surface water of those reservoirs were obviously lower than that in the upper stream and lower stream water in July and August. Along water column,DSi concentrations decreased downward,which is a response to the biological adsorption in upper layer of reservoir.