Wang et al., 2013. Inorganic carbon speciation and fluxes in the Congo River.

Wang, Z.A., Bienvenu, D.J., Mann, P.J., Hoering, K.A., Poulsen, J.R., Spencer, R.G.M., Holmes, R.M., 2013. Inorganic carbon speciation and fluxes in the Congo River. Geophys. Res. Lett. 40, 511-516.

Abstract
Seasonal variations in inorganic carbon chemistry and associated fluxes from the Congo River were investigated at Brazzaville-Kinshasa. Small seasonal variation in dissolved inorganic carbon (DIC) was found in contrast with discharge-correlated changes in pH, total alkalinity (TA), carbonate species, and dissolved organic carbon (DOC). DIC was almost always greater than TA due to the importance of CO₂*, the sum of dissolved CO₂ and carbonic acid, as a result of low pH. Organic acids in DOC contributed 11–61% of TA and had a strong titration effect on water pH and carbonate speciation. The CO₂* and bicarbonate fluxes accounted for ~57% and 43% of the DIC flux, respectively. Congo River surface water released CO₂ at a rate of ~109 mol m⁻² yr⁻¹. The basin-wide DIC yield was ~8.84 × 10⁴ mol km⁻² yr⁻¹. The discharge normalized DIC flux to the ocean amounted to 3.11 × 10¹¹ mol yr⁻¹. The DOC titration effect on the inorganic carbon system may also be important on a global scale for regulating carbon fluxes in rivers.