Warming temperatures are causing a steady rise in copper, zinc, and sulfate in the waters of Colorado mountain streams affected by acid rock drainage. Concentrations of these metals have roughly doubled in these alpine streams over the past 30 years, a new study finds, presenting a concern for ecosystems, downstream water quality, and mining remediation.
Warming temperatures are causing a steady rise in copper, zinc, and sulfate in the waters of Colorado mountain streams affected by acid rock drainage. Concentrations of these metals have roughly doubled in these alpine streams over the past 30 years, a new study finds, presenting a concern for ecosystems, downstream water quality, and mining remediation.
Natural chemical weathering of bedrock is the source of the rising acidity and metals, but the ultimate driver of the trend is climate change, the report found.
„Heavy metals are a real challenge for ecosystems,“ said lead author Andrew Manning, a geologist with the U.S. Geological Survey in Denver. „Some are quite toxic. We are seeing regional, statistically significant trends in copper and zinc, two key metals that are commonly a problem in Colorado. It’s not ambiguous, and it’s not small.“
The study was published in Water Resources Research.
Although the mechanism coupling warming temperatures to increased sulfide weathering is still an open research question, the new results point to exposure of rock once sealed away by ice as a top suspect, Manning said. The sudden appearance of „rusting Arctic rivers“ flowing out of regions of thawing permafrost in the last couple of years is likely the same process, magnified.
Colorado is riddled with patches of bedrock rich in metal sulfides. Shiny iron sulfide, familiar to many Coloradans as fool’s gold or pyrite, is the most common of these sulfide minerals, but copper, zinc, and other metal sulfides are also common.
Exposure to air oxidizes the metal sulfides in bedrock, releasing the metals into groundwater, which flows into surface streams.
