title: The carbon budget of a large catchment in the Argentine Pampa plain through hydrochemical modeling.
abstract: Mar Chiquita is a coastal lagoon located in the Argentine Buenos Aires province in South America. The aim of this study is to estimate the annual contribution of inland waters to the carbon cycle in this lagoon's catchment by estimating the corresponding local carbon budget. Fifteen pairs of water samples were chosen to carry out hydrogeochemical modeling using PHREEQC software. Groundwater samples were considered as recharge water (initial solutions), while streamwater samples were taken as groundwater discharge (final solutions for inverse modeling/reference solutions for direct modeling). Fifteen direct models were performed, where each groundwater sample was constrained to calcite equilibrium under two different carbon dioxide partial pressure (PCO2) conditions: atmospheric conditions (log PCO2 (atm) = -3.5) and a PCO2 value of log PCO2 (atm) = -3. Groundwater samples are close to calcite equilibrium conditions. The calcite precipitation process is kinetically slower than gas diffusion, causing oversaturation of this reactant phase in streamwater samples. This was accompanied by a pH increase of approximately two units due to a PCO2 decrease. From the fifteen inverse models it was estimated that, of the total carbon that enters per year in the hydrological cycle of the study area, about 11.9% is delivered to the atmosphere as CO2 and around 6.7% is buried in sediments. This would indicate that 81.4% of the remaining carbon is retained in equilibrium within the system or discharged into the Mar Chiquita lagoon and/or directly to the ocean through regional flows.
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Ciudad Autónoma de Buenos Aires, Argentina; Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICET-Universidad Nacional de Mar del Plata (UNMDP), Funes 3350, 7600 Mar del Plata, Argentina; Instituto de Geología de Costas y del Cuaternario (IGCyC)-UNMDP, Casilla de correo 722, 7600 Mar del Plata, Argentina. Electronic address: glokgalli@mdp.edu.ar.
authors.forename: M
authors.initials: M
authors.lastname: Glok Galli
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Ciudad Autónoma de Buenos Aires, Argentina; Instituto de Investigaciones Marinas y Costeras (IIMyC), CONICET-Universidad Nacional de Mar del Plata (UNMDP), Funes 3350, 7600 Mar del Plata, Argentina; Instituto de Geología de Costas y del Cuaternario (IGCyC)-UNMDP, Casilla de correo 722, 7600 Mar del Plata, Argentina.
authors.forename: D E
authors.initials: DE
authors.lastname: Martínez
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, C1033AAJ Ciudad Autónoma de Buenos Aires, Argentina; Facultad de Ciencias Naturales y Museo-Universidad Nacional de La Plata (UNLP), Calle 60 y 122, 1900 La Plata, Argentina.
authors.forename: E E
authors.initials: EE
authors.lastname: Kruse
keywords: CO(2) partial pressure; Carbon budget; Hydrogeochemical modeling; Mar Chiquita lagoon's catchment; pH