Contribution of the chemical weathering to the CO2 consumption in a microbasin of Quadrilátero Ferrífero, Brazil

The drainage microbasin of the Bule stream drains an important part of the Quadrilatero Ferrifero, known as one of the main metallogenetic provinces on the planet and of great importance for Brazilian mineral production. The surface water chemistry was analyzed to quantify the chemical weathering rates and the CO2 consumption associated with the weathering processes. Bicarbonate, calcium, magnesium, and silica are the main ions dissolved in the basin, reflecting the local lithotype composed of dolomites, phyllites, and quartzites. The main source of dissolved elements for the basin is carbonate rocks, followed by rainfall. The sulfide oxidation process appeared as the main source of sulfate for the river (approximately 90%). The total weathering rate was 1.5 × 105 mol km−2 year−1 and the total CO2 consumption was 7.3 × 104 mol km−2 year−1, where carbonate rocks are mainly responsible for these flows (> 90%). The highest values were found at high flow, where for the carbonate phases, the weathering rate was 5.38 × 102 mol km−2 day−1, and for CO2 consumption, it was 2.92 × 102 mol km−2 day−1. Despite being a microbasin, the results are relevant when compared to large basins, showing the importance of small-scale studies of rivers that drain basins with a predominance of the lithological type.