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Carbon dioxide and the related species bicarbonate and carbonate are known for centuries and are deeply involved with modern chemistry knowledge from the beginning. Carbonic acid, by its turn, was intuited more than a century before being synthesized for the first time, which was not obtained, however, without stumbles and mistakes. The equilibrium between HCO3− and CO32− in aqueous medium is free of disputes. However, the interconversion of the other three species is rather controversial. Several papers starting in the beginning of the 19th century until the present days are critically reviewed in order to understand the controversial history of the CO2/H2O system. Finally, experimental evidence and theoretical calculations allow us to place HCO3− as the central species as the conjugate acid for CO32− and conjugate base for two different acids: H2CO3 and CO2.

Introducción/objetivo: las emisiones de gases de efecto invernadero (GEI) de origen natural han aumentado por las acciones antropogénicas, y amenazan al planeta con un desequilibrio ambiental. Los embalses para almacenar agua, que después se utiliza para mover las turbinas de centrales hidroeléctricas, acumulan sedimentos generando GEI. En este trabajo se analizan los métodos empleados para estimar las emisiones de GEI en embalses, clasificando las publicaciones científicas encontradas en los motores de búsqueda de ScienceDirect y Google Scholar. Metodología: el método analítico utiliza una expresión booleana para recopilar información en los motores de búsqueda indicados y extraer la bibliografía relevante, considerando factores como la temperatura del agua, la ubicación geográfica, el tipo y la superficie del embalse, el tipo de gas y la tecnología, lo que atribuye un valor de pertinencia a cada característica para elaborar una matriz de resultados. Resultados: los resultados muestran que más del 50 % se basan en estimaciones de GEI y el resto en mediciones directas en los embalses. Además, la contribución de la inteligencia artificial como técnica de estimación es menor al 6 %. Conclusiones: finalmente, las regiones mundiales donde se realizan los estudios están distribuidas proporcionalmente y el análisis de literatura científica indica versatilidad en los métodos de estimación de GEI en embalses hidroeléctricos. Abstract Introduction/objective: greenhouse gases (GHG) emissions of natural origin have increased due to anthropogenic actions, and threaten the planet with environmental imbalance. Reservoirs for storing water, which is later used to drive the turbines of hydroelectric power plants, accumulate sediments, generating GHG. This paper analyzes the methods used to estimate GHG emissions in reservoirs, classifying scientific publications found in the ScienceDirect and Google Scholar search engines. Methodology: the analytical method uses a Boolean expression to collect information in the indicated search engines and extract the relevant literature considering factors such as water temperature, geographic location, reservoir type and surface area, gas type and technology, which attributes a relevance value to each characteristic to elaborate a matrix of results. Results: the results show that more than 50 % are based on GHG estimates and the rest on direct measurements in the reservoirs. In addition, the contribution of artificial intelligence as an estimation technique is less than 6 %. Conclusions: finally, the world regions where studies are conducted are proportionally distributed and the analysis of scientific literature indicates versatility in GHG estimation methods in hydropower reservoirs.