High-Andean páramo ecosystems regulate streamflow and water quality through water storage, subsurface flow, and natural hydrogeochemical buffering. However, increasing land-use pressures may generate early water-quality signals that are difficult to distinguish from natural geogenic variability in protected headwater catchments. This study evaluated the spatiotemporal variability of water quality in the Diablo Sacha River, located within the Quinllunga Water Protection Area, Ecuador. Water samples were collected at ten monitoring stations during six bimonthly campaigns from March 2024 to January 2025, generating 60 spatiotemporal observations per parameter. An integrated hydrogeochemical and multivariate framework was applied, combining Piper diagrams, Spearman correlation analysis, independent principal component analyses for hydrogeochemical and anthropogenic variables, and two-way PERMANOVA. Results showed a predominant Ca–Mg–HCO₃ hydrochemical facies, indicating that water chemistry is mainly controlled by natural mineral weathering, water–rock interaction, and longitudinal solute accumulation. The hydrogeochemical PCA explained 52.75% of the variance and identified a mineralization gradient associated with EC, HCO₃⁻, SO₄²⁻, Ca²⁺, Mg²⁺, and hydrological dilution. The anthropogenic PCA explained 61.77% of the variance and revealed secondary signals related to nutrients, organic matter, suspended solids, oils and grease, and microbiological indicators. PERMANOVA confirmed significant spatiotemporal structuring for hydrogeochemical variables and seasonal modulation for anthropogenic indicators. Overall, the Diablo Sacha River functions as a hydrogeochemically buffered high-Andean headwater system, where natural páramo processes maintain water-quality stability, while emerging anthropogenic signals act as early-warning indicators of ecosystem pressure.

El presente estudio evaluó la contaminación por Arsénico (As), Mercurio (Hg), Cadmio (Cd) y Plomo (Pb) en sedimentos mediante el cálculo del Factor de Enriquecimiento (FE), el Índice de Geoacumulación (Igeo) y el Índice de Potencial de Riesgo Ecológico (IPRE), así como el Riesgo Sanitario Ambiental (RSA) en sedimentos y bivalvos. El área de estudio es el estuario La Puntilla, ubicado en la provincia El Oro, Ecuador, donde se definieron tres zonas y se tomaron 66 muestras de sedimentos en 27 puntos de muestreo. Se capturaron 65 ejemplares de Anadara grandis entre 20 y 60 cm de profundidad en zonas aledañas al río Chaguana para el análisis de Hg. Los resultados mostraron que la correlación entre los parámetros físico-químicos del sedimento y los metales pesados es mayoritariamente baja, evidenciando un origen antrópico de la contaminación. Respecto al FE, Igeo, IPRE y RSA en sedimentos, la Zona 2 resultó ser la más impactada, directamente influenciada por actividades locales. En cuanto a Anadara grandis, no se detectó riesgo tóxico por la ingesta del bivalvo.