Modeling Metal(loid)s Transport in Arid Mountain Headwater Andean Basin: A WASP-Based Approach

Area of Science:

• Environmental Chemistry
• Water Quality Modeling
• Ecotoxicology

Background:

• Toxic metal(loid)s in surface freshwater pose global risks to human and ecosystem health.
• Acid rock drainage impacts watersheds, necessitating robust metal(loid) models.
• Arid and semiarid headwaters often lack crucial hydrological and hydrochemical data.

Purpose of the Study:

• To model aluminum (Al), iron (Fe), arsenic (As), copper (Cu), and sulfate (SO4^2-) concentrations in the Upper Elqui River watershed.
• To assess the performance of the WASP8 model for predicting metal(loid) and sulfate concentrations.
• To identify key factors influencing model accuracy, particularly for dissolved concentrations.

Main Methods:

• Utilized the Water Quality Analysis Simulation Program (WASP8) for water quality modeling.
• Modeled total and dissolved concentrations of Al, Fe, As, Cu, and SO4^2-.
• Performed model calibration, validation, and sensitivity analysis.

Main Results:

• WASP8 demonstrated 'good' to 'very good' performance for total metal(loid) and sulfate concentrations.
• Model predictions for dissolved concentrations were less accurate, ranging from 'acceptable' to 'very good'.
• Sensitivity analysis identified the partition coefficient as critical for dissolved concentration accuracy, emphasizing the role of sorption and sediment interactions.

Conclusions:

• The WASP8 model is effective for simulating total metal(loid) and sulfate concentrations in the Upper Elqui River watershed.
• Accurate prediction of dissolved metal(loid) concentrations requires detailed, site-specific data on suspended solids properties.
• Integrating sediment dynamics (sorption, sedimentation, resuspension) is vital for improving model performance.