PHOENIX — With their natural beauty and protected environments, the Grand Canyon and other national parks in the West would seem removed from having mercury in their streams and rivers.
But a federal study found small levels of the contaminant in rainbow trout and brown trout at three Grand Canyon creeks — Bright Angel, Havasu and Shinumo — as well as in fish at 20 other parks.
While none of the levels found by the U.S. Geological Survey and National Park Service exceeded standards for mercury set by the Environmental Protection Agency, Colin Eagles-Smith, the lead author, said the findings provide the first comprehensive look at mercury levels in western national parks.
“We often hear the negative side of the story with things like mercury,” Eagles-Smith said. “The positives from this study were that we studied a lot of parks and a lot of lakes and in the majority of those systems, mercury concentrations were low.”
However, some environmental advocates said they’re concerned because the locations studied were thought to be distant from contaminants.
“We hope that our national parks are some of the most pristine, best protected areas in the country,” said Kevin Dahl, senior program manager for the National Parks Conservation Association. “There’s typically no industry in these parks, so they’re the farthest removed from potential sources of pollution.”
Fish at all three creeks studied in the Grand Canyon had more mercury in their systems than trout of comparable weight and length at the other parks.
In addition, trout at Shinumo Creek had double the amount of mercury of fish from the other two creeks, though it’s still a mystery as to why, Eagles-Smith said.
“The goal of this study was really not to answer why on any of these things but to look at how mercury is distributed across the landscape in this large area,” he said.