Researchers at the Mountain Studies Institute are part of a team taking soil and lake-sediment samples here this summer to better understand the far reach of toxic mercury in our ecosystem.
Wildfire is believed to result in the release of mercury from soil, which makes this – the site of the 2002 Missionary Ridge Fire, which burned 72,000 acres around this mountain community – a logical place to look for it.
The study is an extension of ongoing mercury research in the region, which includes monitoring of airborne mercury at Molas Lake and Mesa Verde National Park, sampling mercury in songbirds and analyzing sediment from high-elevation lakes.
Mercury is a neurotoxin that affects humans and wildlife. The concentration of mercury increases as it passes from plants to herbivores to predators to humans.
Five bodies of water in Southwest Colorado – McPhee, Totten, Vallecito and Narraguinnep reservoirs and Navajo Lake – are under fish-consumption advisories because of unsafe levels of mercury.
Methyl mercury, produced by microorganisms, is the form found in fish. Airborne mercury can arrive from coal-fired power plants in northwest New Mexico or from as far away as China, lead investigator Joe Ryan said.
An early conclusion is that low-intensity prescribed burns have little affect on the amount of mercury in the soil. But high-intensity wildfire decreased mercury in the soil, releasing more of it into the environment.
Ryan is a researcher and professor of environmental engineering at the University of Colorado. He has studied mercury from the Florida Everglades to the mountains of the Yukon.
Collaborating with Ryan are Chris Peltz, research coordinator at the Mountain Studies Institute, and students from Fort Lewis College and the University of Colorado.
No all-encompassing answer about the conduct of mercury in the face of fire is expected from the three-year study, Ryan said by telephone Thursday.
Rather, in the next two years it can provide food for thought for water and land managers, Ryan said.
In soil, mercury deposited naturally or from coal-fired power plants remains fairly stable, bound by organic matter, Ryan said. But fire, particularly high-intensity wildfires, releases mercury into the atmosphere and frees it to wash into waterways.
“We’ve found that fire diminishes the ability of forest soil to bind mercury,” Ryan said. “Fire also tends to make soil water-repellent, allowing erosion to occur more easily.”
Soil samples are being taken at Mesa Verde National Park and in the Piedra River drainage, as well as Vallecito Reservoir. Among the targeted sites are some hit by wildfire and some on which the San Juan Public Lands Center, a partner in the study, plans to do prescribed burns to reduce forest fuel.
Ultimately, the core samples are scheduled to be analyzed by X-ray Absorption Near Edge Spectroscopy at the University of Illinois in Chicago. The analysis looks at oxidation of sulfur in organic matter, a clue for understanding the behavior of mercury.
Ryan said his team’s research is sort of a midpoint between work to reduce pollution at its source and after-the-fact treatment.
“We’re looking at how mercury is transported and changed,” Ryan said.
Ryan said the ways soil holds mercury differ from the Everglades to Colorado to the Yukon. As an analogy, he cited what George Aiken, a colleague at the U.S. Geological Survey, says about tea: It’s all organic, but it comes in different flavors.
The current work started with a $16,000 grant from the University of Colorado Outreach Program in 2008, Ryan said. The grant was instrumental in winning $690,000 from the National Science Foundation for the present research, he said.
Jackson Webster, a doctoral candidate in environmental engineering at the University of Colorado who is working with Ryan this summer, independently won a George Melendez Wright Climate Change Fellowship from the National Park Service to study core samples of mercury at Mesa Verde National Park.
Other members of the team are Eric Falk, a biology major at Fort Lewis College; Crystal Kelly, an environmental studies major at Fort Lewis College; Chelsea Ottenfeld, a geology major at Tennessee Tech University who has a summer internship at the University of Colorado; and Doug Winter who is studying environmental engineering at the University of Colorado.