Mountain snowpacks in the Rockies, crucial for supplying water to the American West, are becoming contaminated with mercury and other metals due to atmospheric transport from regional mines. This is the central finding of a study published in the journal Environmental Pollution by researchers led by Monica Arienzo, Associate Research Professor of Hydrology at the Desert Research Institute (DRI), alongside colleagues from the U.S. Geological Survey (USGS), the University of Nevada, Reno, and Portland State University.
Arienzo stated, “Metal pollution in the Rockies is relatively understudied,” highlighting the uniqueness of their comprehensive study span from Montana to New Mexico. The study analyzed nearly 50 sites and found higher metal concentrations in the northern Rockies, with emissions from mines in the Pacific Northwest, Idaho, and Montana identified as likely sources.
The study confirmed contamination levels were within EPA guidelines. However, they represent a risk of accelerating snowmelt. The findings contribute to a broader understanding of the dispersion of environmental contaminants.
Researchers collected and analyzed snow samples from 48 sites in spring 2018, measuring concentrations of metals, including both naturally occurring and industrial sources. They strengthened their conclusions using data from the National Atmospheric Deposition Program, examining metal deposition from 2009 to 2018, which aligned geographically with higher contamination in the northern Rockies.
Arienzo remarked, “I was surprised by the amount of agreement we saw between all these different data sets we brought together.” She emphasized that persistent contamination over time suggests a consistent pattern.
To trace contamination sources, they tracked winter storm paths and related them to USGS and EPA datasets on mining and smelting locations, suggesting that current and historical mining operations contribute to the spread of contaminants. Arienzo concluded, “This study shows the importance of continued scientific monitoring efforts, like the long-term USGS datasets we used here, as well as mitigation of current and historical mining sites.”
The research is part of a National Science Foundation-supported project studying historical mercury contamination via tree rings. Arienzo’s team will compare them with snowpack records to better understand mercury's environmental distribution.
The study, titled "Latitudinal gradients of snow contamination in the Rocky Mountains associated with anthropogenic sources," is available in Environmental Pollution. Among the study authors are Monica Arienzo (DRI), Kelly Gleason (Portland State U.), Graham Sexstone (USGS), Mae Gustin (UNR), Melissa Schwan (UNR), Nicole Choma (UNR), Sarrah Dunham-Cheatham (UNR), Joe McConnell (DRI), Peter Weisberg (UNR), and Adam Csank (UNR).
Researchers at DRI are known for pursuing interdisciplinary questions with global and local impacts, bringing economic returns on research investments to Nevada.
For more information, visit www.dri.edu.