Rocking the Duluth Complex

MnDRIVE researcher looks to Minnesota’s Iron Range for microbial components of sulfide mineral oxidation and sulfate remediation.

by Sarah Perdue

For Dan Jones, a research associate in the BioTechnology Institute and the Department of Earth Sciences, biogeochemistry is not simply an important field of research — it literally rocks.

Jones, who is funded through MnDRIVE: Advancing Industry, Conserving Our Environment (MnDRIVE: Environment), studies natural rock formations and their associated microbial communities. His work, which includes basic science, fieldwork, and industrial applications is focused on microbial processes related to sulfide mineral oxidation in the Duluth Complex — a huge rock body that holds one of the largest undeveloped sources of copper, nickel, and platinum group elements in the world. It is also under review as a potential mining site.

“If you dig up that rock, expose it to oxygen, and nothing is done to contain drainage, it could produce problems such as acidic drainage or sulfate contamination,” Jones said.

Because the Duluth Complex has never been mined for metals, potential contaminants and their concentrations need to be determined experimentally. Through the Minnesota Department of Natural Resources (DNR), Jones obtained rock samples from the Duluth Complex that have been weathered in the lab for over a decade, in effect mimicking their exposure on the Earth’s surface. Working with MnDRIVE co-directors Paige Novak and Mike Sadowsky, and Earth Sciences assistant professor Jake Bailey. Jones uses the samples to understand the associated microbial communities and processes.

“The end goal for me is to understand which microbes are there and what role they play in sulfide mineral oxidation,” Jones said. “The end goal for the DNR and the companies proposing to mine the Duluth Complex is to understand what types of metals, acids, and contaminants are going to be released from this rock and what to do about it.”

Jones is also part of a research team working on a MnDRIVE-funded bioreactor designed for cost-effective sulfate removal. The team, which includes Sadowsky and BTI research associate Chan Lan Chun is partnering with researchers at the Natural Resources Research Institute at UM-Duluth, along with Clearwater Layline LLC, a small Minnesota-based water technology company.

“In Minnesota we have a strict sulfate standard because it is detrimental to wild rice,” Jones said. “Sulfate is just a challenge to remove from water, so one of the best ways to remove it is to biologically reduce it and immobilize it as an iron sulfide mineral.”

Cost and efficiency are limiting factors, so Jones and UM-Duluth colleagues Nathan Johnson and Adrian Hanson also recently proposed research to improve the process. They want to investigate cheap sources of carbon, like waste from paper mills or water treatment facilities, to feed the microbes. They are also looking at low-cost sources of iron (like mine tailings) required to immobilize the sulfur.

“They’re not juicy, nutritionally-rich sources, but they’re cheap,” Jones said.

In addition to his research role, Jones is the industrial liaison for MnDRIVE Environmental initiative. His role is to organize meetings and connect the relevant professionals, with the expectation that once an environmental concern has been identified in one sector of the economy, MnDRIVE-funded research can help to reduce the impacts.

“The goal is to bring microbiologists, geologists, engineers, mining engineers, and regulatory people together to bridge the gaps, get people talking, understand the issues, and figure out what we can do about them,” Jones said.

While the current focus is primarily mining, Jones expects MnDRIVE to play a role in other areas where economic activity and environmental concern overlap.