Carbon fluxes in a carbonate rock dominated microbasin of the Quadrilátero Ferrífero, Brazil.

This study evaluated carbon dynamics in a carbonate microbasin (Bule stream), located in an important metallogenetic area (QF) in Brazil. River water collections were performed on a base and high flow. The microbasin showed high DIC, with HCO being the main component, followed by CO. The pCO showed high values, indicating fluxes in the water → air direction. The degassing was 683.4 mmol m day (average at low flow) and 43.4 mmol m day (average at high flow). The fluvial flow was 9 to 31 kg km day of HCO and 1.4 to 0.7 kg km day of CO, respectively, at the base and high flow. Considering the importance of the lithological unit of the Minas Supergroup for the QF, the total flow of CO released by all the basins that compose such units was estimated. The estimated values were 1.3 × 10 mmol day in low flow and 8.4 × 10 mmol day in high flow. The data obtained in this study were the first in the QF region. The Bule stream is an environmental protection area, free from contamination, considered a background for other drainage basins inserted in the QF. The results obtained reinforce the importance of hydrographic microbasins influence on the river carbon fluxes in a regional and global context.