Arizona's metal ore mining industry supplies the copper, silver, gold, molybdenum and lead used to make cell phones, cars, electrical wiring and other products that are an important part of everyone's lives.
The state's rich history of mining has resulted in a legacy of older waste sites that have not all been reclaimed. Such wastes include piles of mine tailings, fine-grained waste generated from the crushing of ores and extraction of valuable metals, and acid mine drainage, highly acidified water commonly generated in mined areas.
Legacy site mine tailings and acid mine drainage often contain high levels of toxic metals – particularly arsenic and lead – as older metal extraction processes were not as efficient as they are today. On windy days, the tailings can become airborne and travel to neighboring communities, posing risks to human health and the environment.
Similarly, acid drainage from mine waste can contaminate surface and groundwater that surrounding communities depend on as their only water source. The 2015 Gold King Mine spill in southwestern Colorado is a recent example.
Through a $3.27 million grant from the National Institute of Environmental Health Science that began in October 2017, the University of Arizona Superfund Research Program is addressing the risk and remediation of metal mining wastes. The program studies the health and environmental effects of metal mining in arid and semi-arid environments, focusing on Arizona mines as examples that can apply to other hard-rock mines around the world.
The research involves five UA colleges and is led by principal investigator Raina Maier from the College of Agriculture and Life Sciences, along with 14 co-principal investigators from the College of Engineering, College of Medicine, College of Pharmacy and College of Science.
"The Superfund program at the UA is now in its 28th year," said Maier, a professor in the CALS soil, water and environmental science department. "This current 2 1/2-year UA Superfund Research Program is building on a body of work begun on mining about 10 years ago that has included extensive outreach to policy makers and to the mining industry, and a tremendous amount of work with communities."
Environmental and Biomedical Research
More than 50 UA faculty, staff, and undergraduate and graduate students are conducting research at current and legacy mine sites, and also on the UA campus. Three environmental projects are dedicated to finding innovative and cost-effective methods for remediating airborne and waterborne mine waste. Study sites include the Iron King Mine and Humboldt Smelter Superfund Site in Yavapai County, and the Hayden Winkelman Superfund Alternative site in Gila County. Both are legacy sites where mining started in the early 1900s.
The first team is measuring dust emissions from mine waste sites and using that data to create models that can be combined with weather forecasting to help mining companies know the key times to manage their sites to reduce dust emissions.
The second team is investigating the transport and fate behavior of acid mine drainage contaminants in groundwater. This understanding will lead to the development of new, more cost-effective methods for remediation of contaminated groundwater.
The third team is working on containing and remediating mine tailings by using desert plants and revegetation techniques to stabilize the mine wastes. They hope to find out which native plants can be used to transition the tailings from plant-suppressing, acid-generating waste piles into plant-sustaining material that won't blow away.
The fourth and fifth projects are medical and pharmaceutical studies regarding inhaled toxins. Scientists from the UA Superfund Research Program are evaluating the effect of dusts that contain arsenic, specifically their effect on lung development and health.
They are demonstrating that, in addition to ingestion via drinking water and food, it is important to consider the inhalation of dust as an exposure route for toxins such as arsenic. The researchers are also seeking dietary interventions to reduce or mitigate the toxic effects of inhaled dust. Known health risks from inhaling arsenic include lung disease and lung cancer, which are the focus of the grant.
Preliminary Results and Community Outreach
Recently, two project teams combined forces to examine the effect of plants on dust emissions from a field trial at the Iron King Mine and Humboldt Smelter Superfund Site. The results, published in April, showed the impact of plant canopy cover and irrigation at the field site on dust emissions and the transport of metalloids from mine tailings.
Horizontal dust flux, or distribution, and dust emissions were measured over test plots with various levels of plant cover and no cover. The plots with 16 percent and 32 percent canopy cover had significantly reduced amounts of dust flux and dust emissions that were comparable to those in local undisturbed grasslands.
In addition, airborne particulate matter concentrations were substantially reduced, including those considered among the worst for posing health risks and with the potential to travel long distances. The research not only applies to Arizona, but also to the nearly 500,000 mine sites that are abandoned and unreclaimed across the United States.
"Through our research translation core, the goal is to provide the research results to stakeholders in the mining industry and affected communities, and to policymakers and regulatory organizations," Maier said. "We are providing neutral, science-based information for all of our stakeholders to use in making their own decisions."
In addition, a community engagement component of the project aims to empower underrepresented populations to reduce health and environmental challenges, focusing on Tribal Nations and Tribal Colleges.
"The purpose of community engagement is to champion community members by providing them with consumable science-based information that they have identified a need for. In this way, they will become active players in understanding and dealing with the environmental health issues they face," said Karletta Chief, who leads the community engagement core and is an associate professor and extension specialist in soil, water and environmental science.
"The exchange between the UA Superfund Research Program and communities is multi-directional and supports citizens to become involved in the research process, problem solving, solution development and political dialogue while researchers learn to refine research questions to target community questions," Chief said. "In the Gold King Mine Spill project with the Navajo Nation, the SRP wrote a fact sheet within weeks after the spill to help answer community questions. Through listening sessions, community members' concerns guided the development of research questions that resulted in securing over $1 million in additional grants to focus on addressing those community concerns."
"The investment by the public in projects like this has amazing payback in what we are able to learn through research on how to reduce human exposures and thereby reduce disease. If we know not to drink the water or that we can stay in on a windy day and minimize inhalation exposure, that's really important," Maier said. "That's one of the great rewards of being a director of a program like this – to see those outcomes and how we make a difference."