长江流域水库泥沙过滤器效应对溶解硅的滞留行为

Sediment filter effect on dissolved silica retention in reservoirs of the Yangtze River Basin

近几十年来,长江入海溶解硅(DSi)通量显著下降,对河口和近海藻类及赤潮灾害产生深远影响。传统认为水库"生物过滤器"效应是DSi下降的主因,但研究表明"生物过滤器"对DSi的滞留量远小于实际观测的减少量。本文将长江流域大型水库按照滞留时间分成四类,并选取柘溪水库、柘林水库、花凉亭水库、鸭河口水库作为四类典型代表,利用现场采取的表层沉积样,系统研究水库"泥沙过滤器"对DSi的滞留效应。结果表明:四类水库单位泥沙对DSi的滞留率为0.25‰(平均解吸减少率0.11‰+平均吸附率0.14‰);四类水库因泥沙沉降对DSi的总滞留量范围为97~625t/yr,平均为259t/yr;全流域162座大型水库因泥沙沉降对DSi的滞留量合计为16.88×104t/yr,占流域年入海通量减少量的9.12%。

In recent decades,the dissolved silicate(DSi)flux from the Yangtze River into the sea has declined significantly,and this decline has had a profound influence on algae and red tide in the estuary and offshore area.Traditionally,the mainreason for the decline is the bio-filter effect of reservoir;however,the reduction in DSi caused by bio-filter effect is muchless than the actual observed value.In this paper,large reservoirs are divided into four classes according to residence time,and the Zhexi Reservoir,Zhelin Reservoir,Hualiangting Reservoir,and Yahekou Reservoir are each chosen to be studiedfrom the four classes,respectively.To study the sediment filter effect on DSi,surface sediment samples were analyzed.The results show:1)the average detention rate of DSi in the four reservoirs is0.25‰(the average desorption decrementrate is0.11‰,and the average adsorption is0.14‰).2)The retention volume of DSi ranges from97t/yr to625t/yr,andthe average is259t/yr for the four reservoirs.3)The total retention volume of DSi for162large reservoirs is16.88×104t/yr,which accounts for9.12%of all decrement.