摘要：In order to investigate the relationship between dissolved silicon (DSi) and bicarbonate (HCO 3 – ), we analysed water samples from the main Changjiang channel and its main tributaries in August 2006 and, during 2007-2009, the contrasting tributaries Wujiang (WJ) – mainly dominated by carbonate weathering, and Ganjiang – mainly dominated by silicate weathering.The DSi: HCO 3 – ratio ranged from 0 to 0.67, which is in agreement with mixing between the weathering of carbonate or silicate.A negative correlation between DSi and HCO 3 – was observed and interpreted as the imprint of regional geology on water chemistry.This relationship and the DSi: HCO 3 – ratios illustrate the predominant role of carbonate weathering on the riverine HCO 3 – , even forcatchments where silicate rocks are dominant.In contrast, a cascade of dams in WJ tributary influenced the concentrations of Dsi and HCO 3 – and resulted in a positive correlation between DSi and HCO 3 – .This is because reservoirs allowed populations of diatomsto develop and diatoms stoichiometrically sequestered DSi and HCO 3 – causing a negative feedback regulation on the DSi: HCO 3 – ratio.Our study demonstrates that the relationship between DSi and HCO 3 – can reflect not only their geological background but also the influence of algal activity (diatom uptake) within rivers.
关键词：chemical weathering; dam effect; diatoms; negative regulation; Changjiang river.
