Organic matter in karstic aquifers: a potential tracer in the carbon cycle. A small-scale laboratory model approach

Abstract : In karstic aquifers, organic carbon is a potential tracer of the fast flows coming from the soil. To study natural tracing using organic carbon, during karstic flows, we focused on the degradation of organic matter by bacterial activity during the infiltration of water. To demonstrate the impact of TOC (total organic carbon) mineralization on the TDIC (total dissolved inorganic carbon), we created a small-scale model of a karstic aquifer to study the kinetics of degradation for dissolved and particulate organic carbon in two different closed systems, one without carbonate and the other with limestone. During the three-month experiment we found that the proportion of C02 produced by mineralization is significant. Therefore the production of C02 resulting from the mineralization of organic matter must be considered in the carbon balance of karstic aquifers.