Dissolved Trace Metals and Cu Cycling in a Tropical Small Mountainous River in Costa Rica: The Reventazon-Parismina Basin

Small mountainous river systems (SMR) underlain by volcanic lithology substantially contribute to silicate weathering yields and the associated CO₂ consumption. Identifying the sources of trace metals and stable isotopes in dissolved and weathered pools provides insights into metal cycling processes and controlling mechanisms that affect river chemistry. The identification of natural and anthropogenic sources is essential for understanding modern river flux and constraining oceanic mass balance. This study provides the first systematic geochemical analysis of source-to-sink processes in Central America and the first Cu isotopic dataset for a volcanic catchment. Bioactive metals (Cu, Ni, and Mo) are highly correlated with volcanic-derived weathering and dissolved organic carbon (DOC), whereas Zn, Cd, and Cr mainly reflect anthropogenic contributions. Dissolved Cu (DCu) mean of 18.9 nM and the δ⁶⁵Cu values of 0.69 ± 0.08 ‰ (2σ, n= 9) are closely related to the global riverine average. Our results indicate that DCu displays minimal evidence of anthropogenic contributions, suggesting that the gradual increase downstream is driven by natural processes, such as physical erosion, chemical weathering, and organic complexation. Conversely, the δ⁶⁵Cu values suggest a major contribution from agricultural sources.  Here, we present the first trace metal and Cu isotope data in the dissolved pool of the Reventazon-Parismina Basin sampled from its source to the estuary. This study aims to decipher the natural and anthropogenic sources in the catchment’s geochemical pool and constrain the mechanisms driving Cu isotopic variations in one of the larger catchments in Costa Rica.

Presentation Preference: Oral

Primary Presenter: Ana Vasquez Vargas, Tongji University / Latin American University of Science and Technology (anacvv211@outlook.com)

Authors:

Nur Sakinah Abdul Razak, State Key Laboratory of Marine Geology, Tongji University  (nursakinah_abdulrazak@outlook.com)

Zhiwei He, State Key Laboratory of Marine Geology, Tongji University  (hezw@tongji.edu.cn)

Shouye Yang, State Key Laboratory of Marine Geology, Tongji University  (syyang@tongji.edu.cn)