Mercury Cycling and Regulation
By: Katlyn Nohr
New methodologies in trace metal concentration analysis provide scientific data to inform environmental policy, embodying the Wisconsin Idea.
The Wisconsin Idea endeavors to apply university research to improve the quality of life and the environment throughout the state. Exemplifying this idea is the research of Dr. James P. Hurley, director of the UW Sea Grant, whose work is with novel methodologies in accurately measuring trace amounts of mercury in aquatic systems. The central issue in mercury regulation is the difficulty in measuring very low concentrations. Only trace quantities of mercury are found in these aquatic systems, and of these, only one to two percent is methylmercury — the form most commonly found in living organisms. Methylmercury starts as very small amounts in phytoplankton, concentrates through the food web, and eventually reaches potentially lethal amounts in fish that are consumed by humans. Hurley found a solution by taking a tip from oceanographers’ methods on the open sea and applying them to other aquatic systems such as the Great Lakes. According to Hurley, his research is innovative in how it “continued to push the envelope on methodologies,” Hurley says.
Hurley applies these new methodologies not only to measure amounts of mercury found in the environment but to also determine its origins. The principal sources of mercury are industry, atmospheric deposition (rain), and contaminated soil. As mercury undergoes chemical transformations from each of these sources, different isotopes become concentrated, giving each source a unique isotopic signature that can be identified through analysis. “[We] have to look at those sources and then back calculate where it might have come from, based on those signatures,” Hurley says. Knowing which signatures represent the greatest percentage of mercury in fish provides information about which sources need to be most heavily regulated to best protect the environment and public health.
One signature of importance is atmospheric deposition. Mercury often exists as a gas, meaning that it can be transported large distances through the atmosphere and deposited elsewhere in rain. This characteristic means that any use of mercury is both a local and global issue. For instance, most mercury currently in the atmosphere results from small-scale gold miners forming compounds that extract gold from reserves. Once the gold has been obtained, the mercury in the compound is burned off, entering the atmosphere in surprisingly vast amounts. “Burning off the mercury from gold would be equivalent to a month of coal burning,” Hurley says. Understanding the contributions from such sources is vital in creating policies that are most effective at preventing mercury from reaching dangerous levels. Locally, mercury deposition into the Great Lakes region has recently caused fishing advisories for many lakes in northern Wisconsin. Hurley’s research therefore directly impacts the wellbeing of many local citizens.
Given the complex, global nature of mercury deposition, treating the problem is far from simple. In the United States and Europe, environmental regulations in recent years have curtailed direct deposition from products such as medical instruments. “We got rid of the point sources, now we have to get rid of the nonpoint sources,” Hurley says. Regional efforts to decrease mercury deposition are showing positive results, but the metal will remain in systems, such as the Great Lakes, if it is still being introduced into the atmosphere and remains in contaminated soils. In the Great Lakes region, according to Hurley, “There has been a shift away from contaminated sites and more toward atmospheric deposition.” For already contaminated soils and sediments, the primary mechanisms for remediation are dredging, disposal, and capping to prevent additional mercury from entering the food web. Cleaner methods for small-scale gold miners and coal burning will be able to decrease these levels of atmospheric deposition.
Research alone will not be able to implement these changes. Rather, policy makers must use the data that scientists and engineers provide to inform environmental regulations and prevent serious health issues. In areas with contaminated water sources, such as the Appalachian region of the United States, mercury in drinking water has been determined to have direct effects on IQ levels and neurological diseases in infants. “Regional contribution of mercury has been decreasing over time because of regulation,” Hurley says. This decrease in concentrations demonstrates that when scientific experts inform conversations surrounding environmental policies, the impacted environment and local public health will see quantifiable positive results. “We did basic and applied research that lead to a measurable outcome,” Hurley says.
“Regional contribution of mercury has been decreasing over time because of regulation”
As Hurley points out, the utilization of this work embodies the Wisconsin Idea. Applied interdisciplinary research at the university level impacts all areas of the state. “The University of Wisconsin is a great place to do research because people want to collaborate and answer these truly complex questions,” Hurley says. Opportunities provided at UW-Madison for collaborative research make the acquisition of this kind of new information possible. While a better understanding of our natural world enriches scientific knowledge, it is the application of this knowledge that ultimately benefits our society, remediates our environment, and protects public health.
