Caracterización hidroquímica e isotópica de los recursos hídricos en el área minera Santa Rosa, Ecuador

Abstract

CONDITION FOR PUBLICATION OF PROJECT. This research examined the hydrochemical and isotopic composition of water resources in the Santa Rosa mining area, Ecuador, with the objective of identifying the processes that influence the chemical composition of water, its origin, and potential contamination sources. The study emphasizes the influence of anthropogenic activities on water quality. Sampling campaigns, between 2022 and 2024, were carried out during both dry and rainy seasons. Surface water samples were collected from the Santa Rosa River and its tributaries, while groundwater samples were obtained from nearby commercial wells. Analyses included major ions (Ca²⁺, Mg²⁺, K⁺, Na⁺, HCO₃⁻, SO₄²⁻, Cl⁻, NO₃⁻) and isotopes (18O, 2H, ³H, δ³⁴S-SO₄²⁻, and δ¹⁸O-SO₄²⁻), and the data interpretation combined hydrochemical diagrams, multivariate statistical analysis, and geospatial analysis. Results revealed that surface waters predominantly exhibit SO₄²⁻-Ca²⁺ and HCO₃⁻-Ca²⁺ facies, whereas groundwater is mainly of the Cl⁻-Na⁺ type. The chemistry of surface water is primarily regulated by rock-water interactions, while marine evaporites dominate groundwater chemistry. Isotopic signature of δ18O and δ2H confirm a meteoric origin for the sampled waters. Sulfate in surface water is linked to atmospheric deposition and the oxidation of sulfur compounds, while elevated SO₄²⁻ concentrations in groundwater result from evaporite dissolution. This study provides the first comprehensive hydrochemical and isotopic assessment of water resources in a mining-impacted area in Ecuador, generating valuable baseline information to guide the sustainable management of water under mining influence. Keywords: Water quality, Water-rock interaction, Isotope analyses, Sulfate isotopes, Water management.