Influence of discharge on silicate weathering dynamics of the Tietê river basin : major cations and dissolved silica approach

Abstract

The Tietê river water was investigated in terms of the seasonality of major cations and dissolved silica mainly due to the influences of discharges in the watershed, in order to recognize the main rock weathering type occurring in the basin. With the proposed geochemical model it was possible to identify, after atmospheric and anthropogenic input corrections, the main chemical species released from the silicate weathering in the basin and their relationship with the river discharge. With the Re index calculated for the basin (3.09) it was possible to identify the main weathering process occurring in the basin and the transition of the stability field of monosiallitization to bisiallitization, with no significant seasonal variations in the river water discharge.