HYPERSPECTRAL ANALYSIS FOR QUALITATIVE AND QUANTITATIVE GEOCHEMICAL FEATURES RELATED TO ACID DRAINAGE AT A REMEDIATED OPEN-PIT SULFUR MINE

The exposure of pyrite to oxygen and water in mining environments is known to generate acidic water and the accumulation of heavy metals. Sulfates and secondary Fe minerals associated with acid mine drainage (AMD) exhibit diverse spectral properties in the ultraviolet, visible and near-infrared regions of the electromagnetic spectrum. The use of airborne hyperspectral imagery for identification of mineralogy relating to AMD and contamination potential has been well studied. Fewer studies have explored the impacts of hydrologic variations on mapping AMD, specifically the mapping of seasonally induced ephemeral features of these minerals. Sulfates dissolve during rain events or from a rising water table and re-precipitate when less humidity is present causing the formation of surface crusts on waste surfaces. Additionally, the unique spectral properties of mine affected waters is often not a focus in mapping due to the minimal reflectance spectra of water. Suspended sediments, chlorophylls, and dissolved organic matter in surface waters are known to produce changes in the visible spectrum; other chemical factors including the colloidal fraction and ion concentration may influence the optical characteristic as well. A better understanding of the spectral properties of mineralogical variation related to climate fluctuations and the spectral signatures of contaminated surface waters will assist in the assessment of environmental contamination, and the mapping and monitoring of impaired water systems. This study will examine the ability of remotely sensed hyperspectral data to identify the geochemical evolution of substances and contaminant patterns by 1) identifying temporal changes in mineralogy around a remediated open-pit mine and acid water treatment facility, 2) exploring the properties which influence acid water spectra, and 3) linking water spectra to know pH values and metal concentrations for quantitative mapping. Hyperspectral data from NASA’s AVIRIS instrument will be collected over three seasons for two consecutive years at the Leviathan Superfund site, an inactive open-pit sulfur mine located 24 miles southeast of Lake Tahoe. Ground-based surveying with the ASD FieldSpec Pro spectrometer and laboratory spectral and chemical analysis will complement the remote sensing data.