Can Algal Growth Prevent Pollution from the Duluth Complex?

Problem: The Duluth Complex rocks of northern Minnesota contain mineral resources such as copper, nickel, and platinum that are valuable to the state and global economy. However, these minerals are found in sulfide bearing rocks. Although natural oxidation of sulfide in mine waste occurs, rapidly enhanced rates of oxidation have been tied to the presence of certain microbial communities in these tailings. This enhanced oxidation results in elevated levels of sulfate and acid being input to the surrounding environment. These environmental contaminants are particularly detrimental to the culturally significant local wild rice populations.

Solution: Prior work has demonstrated that specific microbial species are responsible for enhanced sulfide oxidation of mining waste. One promising mitigation step towards decreasing sulfide oxidation rates is “bio-shrouding”, where sulfide ore is coated with organic material to prevent interaction between microbes and sulfide. Coating mine waste with organic compounds also promotes the growth of microbes that do not actively utilize sulfide, like algae. This creates a further physical barrier between the microbes that oxidize sulfide and the sulfide itself. The Feinberg team researched whether algal growth can be maintained on the surface of materials directly extracted from the Duluth Complex rocks. We found that algal growth on synthetic tailings may impede the growth of sulfide-oxidizing microorganisms and result in diminished sulfate release, but further study is required to determine if this effect scales in an industrially-useful way.

Impact: Contamination from sulfide-hosted mineral mining has the potential to significantly impact the economy of northern Minnesota and the entire state. However, the environmental consequences should not be ignored or overlooked. The predicted impact on ecosystems, particularly those hosting indigenous wild rice, can be positive if solutions like this prove to be sustainable and effective. Undergraduate ZhaaZhaawaanong Greensky received the 2018 SACNAS Student Presentation Award for her presentation on this research project (Society for Advancement of Chicanos/Hispanics and Native Americans in Science).