Abstract
The study utilizes open-source satellite imagery and the HSV (Hue, Saturation, Value) color model to analyze the color of pit lakes, which is indicative of their
physicochemical properties. This is a cost-effective and efficient method compared to traditional in-situ monitoring.
The true colour (i.e. hue) of a body of water results from the combination of
absorption, reflection and transmission of specific wavelengths of sunlight through
water, mediated by dissolved ions and suspended colloids/fine mineral particles.
Transition metals form distinctive coloured complexes in aqueous solutions depending on the oxidation state of the metal and the ligand it binds (Fe2+: olive-green, Cu2+: blue-green, Fe3+: brown-yellow). Suspended particles interact with sunlight by scattering it. Fe(III) oxyhydroxide colloids scatter the red component of sunlight, Al oxyhydroxide colloids scatter the blue-green component, and very fine aqueous colloidal silica and sulfur particles scatter the blue component. Since both the aqueous complexation and the saturation of both Al and Fe oxy-hydroxides depend on the pH and redox conditions of the water, the results of this study show that the temporal evolution and variations of the HSV parameters give an indication of the changes in the physico-chemical characteristics that pit lakes undergo.
The methodology was successfully tested using the Berkley Pit Lake in Montana (USA), which has extensive historical water quality data (since late 80s). The satellite-derived HSV values correlated well with known events like meromixing (mixing of water layers) and the transition from a meromictic (layered) to a holomictic (fully mixed) state.
This approach can be applied to pit lakes worldwide, providing a valuable tool for
continuous and remote monitoring of pit lakes, even in inaccessible locations. This can help detect potential environmental issues early on, enabling timely interventions.
Date: Friday, April 25th
Time: 10:15–10:30 a.m.
