Hydrogeochemistry and dissolved organic matter as support tracers of recharge, flow paths, and discharge processes in hydrological systems

Abstract

This study evaluates the role of dissolved organic matter (DOM) as a tracer of hydrogeological processes in a fluvio–aeolian system of southern Córdoba, Argentina, integrating optical DOM properties with hydrochemistry. Groundwater from an unconfined aquifer, river water, and a shallow lagoon were analyzed to assess the relationships between water composition, DOM characteristics, and hydrological setting. Water mineralization is primarily controlled by water–sediment interactions, including silicate weathering, carbonate dissolution, and cation exchange. In contrast, DOM exhibits systematic variations related to source, degree of processing, and residence time. Groundwater contains moderately processed and variably humified DOM, reflecting transport within the aquifer under heterogeneous residence times, whereas river water is characterized by fresher, biologically influenced DOM associated with rapid renewal. Lagoon waters show highly humified and refractory DOM consistent with longer residence times and discharge conditions. Multivariate statistical analysis (PCA and HCA) reveals coherent patterns linking hydrochemical evolution and DOM composition, allowing differentiation of recharge, groundwater flow, and discharge sectors within the system. These results demonstrate that DOM provides complementary information to hydrochemistry and acts as a sensitive indicator of biogeochemical processing along flow paths in lowland environments.