Flow of inorganic carbon dissolved on the Piracicaba River (São Paulo): partition and equilibria reactions of the carbonate system.

Abstract

The flow of dissolved inorganic carbon (DIC) in the Piracicaba River (Artemis sampling station, state of São Paulo) was estimated by taking into account the main fluvial components.To this end, equations related to equilibria of carbonate system were applied, and the main involved parameters such as pH, temperature,total alkalinity and discharge during the sampling period were taken into account. The results emphasized that fluvial DIC flow (40,383tC y-1) was controlled mainly by the biogenic processes related to the consumption of atmospheric/soil CO2, including silicate and carbonate weathering. HCO3 - and dissolved CO2 were the dominant DIC species, with a flow of 32,811 (81% of total flow) and 7,557 (19%) tC y-1 respectively, whereas CO3 2- flow was less than 0.1%. In terms of total carbon river flow, the inorganic species represented by HCO3- was higher than the dissolved organic carbon, DOC, which showed an average flow of 22,064 tC y-1. This last figure was mainly associated to domestic effluent contributions.