Acid Mine/Rock Drainage
Acid mine drainage (AMD) is one of the major water quality issues in Colorado and at locations throughout the western U.S. AMD and naturally-occurring acid rock drainage (ARD) contain high levels of sulfuric acid and dissolved metals and are produced when minerals, in particular the widespread pyrite, are exposed to both air and water. The often large-scale land disturbances introduced by mining and mineral processing activities can lead to greater mineral exposure, intensifying acid drainage generation.
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Arctic and Boreal Biogeochemistry and Hydrology
Climate change during the last several decades is having major impacts on northern high latitude systems including Arctic and boreal zones. Permafrost soils (frozen continuously for at least 2 years) are warming and thawing in many locations, especially near the southern limit of permafrost distribution. These soils store huge amounts of carbon (C) which becomes vulnerable to decomposition upon thaw, and additional net emissions of carbon dioxide (CO2) and methane (CH4) from these soils have the potential to further exacerbate climate change. In addition, changes in dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and nutrient exports from soils to rivers can occur as a result of newly thawed sources and, importantly, changes in hydrologic flowpaths.
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Diatoms Past and Present
Diatoms are single-celled algae found in nearly every aquatic habitat, and are an important component of phytoplankton providing both oxygen and food for higher organisms. Diatoms are particular in their tolerances of various environmental conditions with different species surviving in different ranges of pH, salinity, nutrient and suspended sediment concentrations, flow regimes and the like. This makes them good indicators of both current and past water quality and potential proxies for environmental variables such as flow.
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Natural Organic Matter-Metal Interactions
Natural organic matter (NOM) is an important constituent of soils and surface waters for environmental and engineering processes. In aquatic systems, dissolved organic matter (DOM) exerts control on the transport and speciation of trace metals such as mercury, the depth of the photo zone, and the formation and stability of particles. In soils, the organic-rich surface layer can accumulate metals. Predicting the influence of disturbances such as forest fires, mining operations, and changes in water use on the cycling and bioavailability of trace metals relies on our understanding of how NOM influence these processes.
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