Wetterhahn winner uses native plants to stabilize arsenic in mine waste
By Sara Mishamandani
University of Arizona (UA) Superfund Research Program (SRP) graduate student Corin Hammond and an interdisciplinary group of scientists are experimenting with using native plants as an easy, cost effective, and sustainable method of stabilizing arsenic in mine waste. Hammond, winner of the 16th Karen Wetterhahn Memorial Award, presented results and ongoing research from the waste stabilization project in a March 17 talk at NIEHS.
Hammond’s doctoral work focuses on the Iron King Mine and Humboldt Smelter Superfund site near Dewey-Humboldt, Arizona. At the site, large piles of mine waste contain arsenic and other metals that that can spread through the air in dust, due to the region’s arid conditions, and through water, from periodic flooding and runoff. To reduce exposure to arsenic, UA SRP scientists are studying the use of plants to stabilize contaminants from the mine waste and thus prevent transport to nearby communities.
Testing plant growth and stabilization potential
Hammond wants to know whether phytostabilization can prevent movement of arsenic from mine waste piles. To find out, Hammond and her team planted several types of plants, using different amounts of compost, on top of several mine waste piles. As the plants grow, Hammond's team collects soil cores from each plot to test whether the arsenic is becoming more tightly bound to particles in the soil.
Researchers chose native plants that can grow in the arid climate and acidic soil with a high metal content. They are also testing plants that do not accumulate arsenic in plant tissue, but instead stabilize metals in the root zone of the soil. This provides a longer-term solution, because it does not require harvesting the plants to remove arsenic from the area, and it poses less danger to animals that may eat the plants.
So far, Hammond’s team has identified chemical processes that convert arsenic into stable products in the root zone of the plants. This shows that the plants may be helping to keep arsenic from moving through the soil and producing dust that contains arsenic.
A simple solution to a complicated problem
Sustainable management of waste is a challenge facing the mining industry worldwide. Capping or covering mine waste is often used to reduce or eliminate erosion, but it can be prohibitively expensive. According to Hammond, this project is establishing the potential for plants to serve as a vegetative cap, which is a far more cost-effective method to reduce movement of arsenic from mine waste piles.
“We are looking for a simple solution to a very complicated problem,” said Hammond. “The project requires scientists from a wide range of disciplines, and long-term studies, to explore the interactions between plants and the characterists of the mine waste during the vegetation process.”
(Sara Mishamandani is a research and communication specialist for MDB Inc., a contractor for the NIEHS Superfund Research Program and Division of Extramural Research and Training.)