INORGANIC CARBON SEQUESTRATION: THE OXALATE-CARBONATE PATHWAY IN CALCAREOUS KARSTIC ENVIRONMENTS

Abstract

Background. In recent decades there has been an increase in emissions of carbon dioxide (CO2) into the atmosphere, this has caused negative impacts on both natural and anthropic systems. Due to the above, the study of the global dynamics of the carbon cycle has become more important, in order to design technologies and propose management strategies and practices that reduce CO2 emissions into the atmosphere or remove it from it (carbon sequestration). The removal of atmospheric CO2 can occur by biotic and abiotic processes and can be deposited in different natural reservoirs both in organic and inorganic form. One of the mechanisms for sequestering carbon in an inorganic way is the oxalate-carbonate pathway (OCP), which deposits secondary carbonates to the soil, from calcium oxalate crystals. Objective. A review of inorganic carbon sequestration is carried out, emphasizing the deposition of secondary carbonates in soils through the oxalate-carbonate pathway, and we analyzed  its implications in calcareous karst environments. Main findings. The OCP has been mainly studied in acid soils, but it could also be important in alkaline soils, since other secondary sources of calcium, such as those carried by the wind, have not yet been considered (i.e. calcium in Sahara desert dust arriving to Yucatan Peninsula annually). Implications. The study of the OCP has been intensified in recent years, resulting for us of particular interest in calcareous karst environments, due to its high spatio-temporal dynamics dominated by carbonation-decarbonation reactions. Conclusion. Evidence of OCP activity has been found in karst environments; however, this metabolic pathway presents spatial and temporal dynamics, so it is difficult to estimate its contribution to the global dynamics of C, and it may contribute by delaying the return of CO2 to the atmosphere.