Mercury and Global Change

Alex Demas: Hello everyone and welcome to another edition of USGS Corecast. I’m your host, Alex Demas. Today, we’ll speak with USGS scientist David Krabbenhoft about an article he wrote that was just published in Science on the effects of global change on mercury. Dr. Krabbenhoft has studied mercury for more than 25 years, and was heavily involved in the work that led to the 2013 Minamata Convention on Mercury, a binding resolution signed by 140 countries that regulates man-made emissions of mercury. We’ll now talk with Dave to find out how climate change and other man-related factors will affect global mercury. Alex Demas: What prompted this study? David Krabbenhoft: Well, my co-author and I, Elsie Sunderland, from Harvard University were asked by the organizers of the International Conference on Mercury as a Global Pollutant to put together a very broad description of how current global change drivers were affecting mercury across the world. One of the primary motivators for this were a few very important mercury regulations and treaties that have recently been passed. All told, the inclusion of the United Nations Environmental Program Minamata Treaty with the United States Mercury and Air Toxic Substances Rule will have a significant impact on the amount of mercury being released into the atmosphere. Alex Demas: What are the major sources of man-made mercury? David Krabbenhoft: Man-related mercury releases are currently mostly derived from electric power generation, specifically from coal, and, more recently, particularly in the last decade, mercury uses in the extraction of gold has greatly accelerated in developing countries. In recent years, it has outpaced the emissions of mercury from coal-burning and is now the number one source to the environment. Alex Demas: In that context, how much mercury do we produce? David Krabbenhoft: Well, currently, there’s about 2,000 metric tons of mercury that is released to the environment from all sources. Alex Demas: Looking out to 2050, is that number likely to change or remain about the same? David Krabbenhoft: Well, we have a hard time knowing with great assurity what direction the mercury emissions inventory will trend, but those that have studied that basically bracket the range of possible emissions in 2050 between a best-case scenario that would be about 800 metric tons, and under that scenario, would include full implementation of the Minamata UNEP Negotiated Accord that was recently passed in January. That would eliminate about 70 percent of all man-related emissions. On the other end of that range would be if we did nothing in the future, between now and 2050, and we just continue at this current pace, and that would yield an emission estimate of about 3,400 metric tons. Alex Demas: What are the major ways that global change will affect mercury and its cycling and impacts around the world? David Krabbenhoft: Well, as my co-author, Elsie Sunderland, and I were thinking about that specific question when we were framing the paper that is being published in Science at the end of September, we realized that there were two broad categories of global change that could affect mercury cycling and impacts around the world. Those would largely going to be manifested through what we generally call climate change and then those other factors that are also global-change related, but are more related to the non-climate factors and are driven by man’s actions. We broke the paper up into those two broad areas of driving influences of mercury impacts to the world in the future. Alex Demas: What is the most damaging type of mercury as far as environmental and human health is concerned? David Krabbenhoft: Methylmercury, which is far more toxic to all living systems than inorganic mercury. Alex Demas: And that should do it! Thank you for joining me, Dave. This has been another edition of USGS Corecast, a product of the U.S. Geological Survey, Department of the Interior.