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Eric Pierce’s Interview

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Eric Pierce is a senior scientist and leader of the Earth Sciences Group in the Environmental Sciences Division at Oak Ridge National Laboratory. Born in New Orleans, Pierce has a Ph.D in low-temperature geochemistry from Tulane University. In this interview, Pierce describes some of the work of his team at Oak Ridge, including how contaminants and energy production byproducts such as mercury move through the environment. He provides an overview of the important mercury research and discoveries scientists have made at ORNL, and speaks to the collaborative and dynamic nature of ORNL as a workplace.

Date of Interview:
April 25, 2018
Location of the Interview:


Cindy Kelly: I’m Cindy Kelly. It is Wednesday, April 25, 2018, and I’m in Oak Ridge, Tennessee. I have Eric Pierce, and my first question for Eric is to please say your name and spell it.

Eric Pierce: My name is Eric Pierce, and that’s E-r-i-c, Pierce, P-i-e-r-c-e.

Kelly: Great. Thank you.

Pierce: You’re welcome.

Kelly: All right. Now, another question—which is going to be easy, too—is basically, to tell us about yourself: where you were born, and your child education, and how you became interested in being a scientist.

Pierce: I am originally from New Orleans, Louisiana. I went to high school there. I graduated from a high school which is a college preparatory high school called McDonogh 35. From that school, I went on to undergraduate at Alabama A&M University. It’s a small school in Huntsville, Alabama, where I played four years of baseball, while also getting a Bachelor’s degree in environmental science with a minor in chemistry.

After finishing from Alabama A&M and doing a series of internships at a national lab out in the Pacific Northwest, which is Pacific Northwest National Lab, I went on to graduate school at Tulane University, after graduating from Alabama A&M.

I realized through the internships that probably a Bachelor’s degree wasn’t enough, and I realized that I was quite interested in doing research. I enrolled in Tulane, and at Tulane I finished with a PhD in what I will refer to as low-temperature geochemistry.

As I explain to my kids, geochemistry simply sits at the intersection of how water influences the earth around us, so to speak. Primarily rocks and minerals, which in some respects most of us experience either as rock outcroppings like granites and basalts in Hawaii. But also, as water interacts with those particular rocks, it forms a lot of the soils that we use to grow crops, grasses, et cetera.

That’s kind of my story. From graduate school, I took a job at PNNL and was there for about ten years. From PNNL, which is a national lab, to Oak Ridge, and I’ve been here now about seven or eight years.

Kelly: Wonderful.

Pierce: I’m a scientist. I always tell people all the time, I’m a scientist first, I’m a group leader second, group leader of the Earth Sciences Group, which is in the Environmental Sciences Division. The Environmental Sciences Division is quite diverse in the work that we do, some of which includes primarily a group of geochemists, which I manage. There’s about ten staff members and about another ten post-docs within the organization.

There are a series of groups that span aquatic ecology to terrestrial ecology, to studies on climate change through our Climate Change Science Institute, which is a combination of the terrestrial ecologists but also many of the folks that utilize the large computers that we have here at Oak Ridge National Lab. Several groups that work on hydropower and the impacts of utilizing hydropower on, for example, fish passage in a variety of our river basins, whether it’s the Tennessee River Basin, Colorado River Basin, and/or the Columbia River Basin, which is out west.

Kelly: All of these activities you just named are part of the Earth Sciences?

Pierce: Good question. All these activities I just named, Earth Sciences represents a component. They really span the breadth and depth of the division, which is the Environmental Sciences Division. In my opinion, one of the few Environmental Sciences Divisions across the complex that has a long history in trying to understand how radionuclides migrate through the environment as part of nuclear weapons production, and in trying to understand how that impacts the terrestrial environment.

Building that long history up to where we are today, that division is probably the most complete Environmental Sciences Division—which is the point I wanted to make—across all of the seventeen national labs within the complex. It has its roots sitting in the 1940s, just trying to understand how cesium moves through the environment, in case an enemy would impact or release a nuclear weapon here in the U.S.

The division has had a long history of doing that kind of work. That has transitioned into, “How do you use water to produce energy?” and, “What’s the impact of that use of that water on many of the aquatic resources that we have across the country?” To understanding how an evolving environment may release a certain amount of CO2 and/or methane. A long history in doing work on understanding, “What’s the impact of acid rain on our terrestrial ecosystems?”

In particular, for the Earth Sciences Group, we have a long history of studying subsurface migration of energy byproducts. That ranges from trace metals such as mercury or lead or cadmium or cobalt, which you can also have radionuclides that are variations of those.

But also, understanding how uranium, for example, migrates through the environment in subsurface systems. Uranium is a primary product of nuclear weapons in general, and a primary product of much of the nuclear energy that we produce across the country. As a country and as a nation, we have a responsibility to store that material for long-term storage and disposal. Understanding how uranium moves through the environmental, through the terrestrial environment, has been a long history within the Earth Sciences Group in general. A lot of foundational studies that we’ve done.

You know, it’s really born out of a legacy of the history of nuclear weapons production. DOE [Department of Energy] has a number of sites across the complex that are impacted as a result of weapons production. We hear about the Hanford Reservation, where there’s a fair amount of uranium contamination. You hear about, in some cases, here in Oak Ridge. In addition to that, many of the nuclear power plants have used fuel that they eventually will dispose of. How do you store that material in a safe manner?

All of these represent conditions that are, in some cases, energy byproducts, but in some cases, just a history of the Manhattan Project. The Department of Energy has had a long history, one of understanding how those materials move through the environment. But more importantly, how do we address the contamination legacy that exists? What my group does, primarily, is provide that foundational knowledge that enable the Department to address those issues in a safe manner.

Kelly: That’s very worthy. There are a lot of examples of contamination in, let’s say, the East Fork Poplar Creek years ago. It was mercury contamination, right?

Pierce: Um-hmm.

Kelly:  Where does that stand today?

Pierce: I always like to explain to people, while East Fork Poplar Creek represents a point source pollution of mercury to a stream system, mercury really represents a global pollutant that is the result of the burning of fossil fuels, primarily anthropogenic releases from coal-fired plants.

In addition to that, you have a number of sites across the country that were former gold-mining sites, many that exist out west. Elemental mercury has a unique property. It has the ability to amalgamate gold. It creates a material that allows you to extract gold by mixing it with minerals, gold in its native form in the earth. After mixing it, you have the ability to remove the mercury by simply burning the resulting material. That allows you to recover gold.

If you can think back into the 1800s, we did quite a bit of mining of gold in the early 1700s or so, mid-1700s, late 1700s. You have a number of mining sites that have point source pollution from just gold mining itself.

In the case of here in Oak Ridge, the legacy that exists for the mercury contamination within East Fork Poplar Creek is primarily the result of isotope separations that was done within the Y-12 National Security Complex. A fair amount of mercury was lost in the environment, or unaccounted for. It’s estimated somewhere around 700,000 pounds of mercury was lost to the environment. Not all of that mercury ended up in East Fork Poplar Creek, but some of it did.

What we’re currently studying is providing that foundational knowledge—really, basic science—to understand how mercury cycles in the environment. By understanding how it moves, how it migrates, how it interacts with other ligands within the environment—for example, dissolved organic matter. Understand how it’s transformed by different anaerobic microbes in the environment provides a significant amount of understanding that will be required to not only address the issue here in Oak Ridge, but the issues that exist worldwide in terms of former gold-mining sites.

An example of that would be, the United Nations now recognizes the issues around mercury globally, primarily from artisanal gold mining and small-scale gold mining that’s going on in many of the developing countries. While many of the emissions of mercury have decreased from North America as well as in Europe, the emissions from many of your developing countries—Asia, Africa—is on the rise. That’s in part because of small-scale gold-mining, as well as the burning of fossil fuels in places like China.

Being able to develop that foundational knowledge of different reactions that occur in the environment—how mercury moves, how it’s converted from inorganic mercury to methylmercury, which is the primary risk driver; I’ll explain why that it is here in a minute—is important for a broad range of issues both here in the U.S., but also globally.

The reason why we care so much about methylmercury is that it can have an impact on the neurological development of humans. The primary concern is in infants, young kids and elderly. Us as humans come into contact with it [methylmercury] through fish consumption. I want to make sure I make that clear.

The reason why that becomes important is, methylmercury has the ability to bioaccumulate up the food chain. A small amount in water increases in total concentration as you move up the food chain, going from small microbes that are in the stream, certain critters eat those microbes, smaller fish eat those critters. Larger fish—in our case, like trout—eat those smaller fish.

The concentration of methylmercury in trout or bluefin tuna can be quite high, because they sit at the highest level in the food chain. In things like tuna, trout—many people like sushi, bluefin tuna, which is the crème de la crème of sushi—can have quite a bit of methylmercury in it. They live a long time and they get really, really big, and they eat a lot.

The primary concern is really through fish consumption. In many of these cases, things like bluefin tuna, trout, they have fish consumption advisories. In other words, how many of them can you eat if you’re pregnant, if you’re a pregnant female?

Kelly:  Wow. Really a global perspective.

Pierce: Yeah. Methylmercury is quite complicated. Understanding how it transforms in the environment, its ability to move around the environment, and how it relates to how we use energy today and how we produce energy today—it’s quite fascinating, quite fascinating.

Kelly:  This is just one piece of the kinds of problems you’re dealing with, right?

Pierce: Yeah. It just represents one piece. We use East Fork Poplar Creek really as a test bed, to have that global perspective. For example, the team here at Oak Ridge National Lab, back in 2013—and this is just one example—discovered the two gene clusters that are responsible for how bacteria has the ability to methylate mercury, convert inorganic mercury to methylmercury.

Prior to that discovery in 2013, no one knew within the science community how that was happening. We knew it happened in environments—when I say anaerobic microbes, I’m talking about bacteria that live in zones that are oxygen-deficient. These microbes really have the internal machinery that’s required to convert inorganic mercury to methylmercury. Understanding that phenomenon has really revolutionized the way people today do research within the mercury community when they collect samples from many different places across the globe.

The team has used ORNL’s [Oak Ridge National Laboratory] foundational capability in genomics, in genetics, to not only identify those genes, but to also look for the variety of different microorganisms that live in these zones that are oxygen-deficient, that exist globally. Ultimately leading to the discovery that there are other types of microbes that have the ability to do this.

We’ve continued to build on those types of discoveries in the project to not only address our challenge here in Oak Ridge, but address those challenges globally. Those just represent two examples of really many that have literally changed the way people do mercury research today, and the level of depth of information they can get out of that research today, globally.

Kelly: That’s fascinating. I think on the flip side of bacteria in this case, they’re bad actors. They make inorganic into methylmercury.

Pierce: That’s right.

Kelly: It’s problematic. But aren’t there other microbes that you’ve been discovering that can make toxic substances less toxic?

Pierce: Yeah, yeah. For a long time, researchers have known that certain aerobic microbes have the ability to demethylate the mercury. In other words, remove a carbon and a hydrogen group—CH3 is the methyl group—remove it from the mercury.

Early on in the project, we did a lot of studies on those particular microbes. More recently, though, a researcher that’s in my group, Dr. Baohua Gu, discovered that methanotrophs have the ability to actually demethylate mercury. It’s kind of like we stumbled on it, with some collaborators both at the University of Michigan and at another university that escapes me right now.

We identified that certain microbes have a particular molecular compound referred to as methanobactin. It’s just a way that microbes have the ability to acquire copper in the environment. Copper is an essential micronutrient for a variety of different functions in microbes. Some, when they’re copper-deficient, these particular microorganisms, methanotrophs, they emit a molecule that has the ability to go out and look for copper and bind it. Then the microbes have the ability to pull that molecule back in, so that they have the copper that they need.

This particular molecule also has the ability to complex methylmercury, and then when it comes back into the microorganism, the microorganism has the ability to then demethylate that mercury. We still don’t know how it does it. That’s really a part of what we plan to do as we move out into our next three years of the project.

It’s a fascinating thing. There are a lot of things we have to work on over the next three years to unravel that mystery. But it’s quite exciting, knowing that microbes have the ability to do this. The truth is they do it with other metals, too, such as iron. Siderophores is another similar to methanobactin. We know microbes have the ability to emit these things. But what we didn’t know was that this particular molecule had the ability to demethylate the mercury. That discovery was quite exciting.

You have some bad actors, you have some good actors. What we want to understand is, what’s the balance between those two processes? Some produce methylmercury. Some have the ability to degrade it. How do you determine which one wins in a particular condition? Again, brings it back to understanding how mercury cycles within a system, such as a flowing stream, which represents our test bed that we’re studying today.

Kelly: It’s interesting if you think about, if people are so adversely affected by methylmercury, but there are these microbes that destroy it. Maybe somebody who’s been poisoned with that might be cured or treated?

Pierce: Yeah. I’m not a medical doctor, but what I can tell you is the history and the story behind how we figured out that methylmercury was a problem. That really sits as a result of mercury being used in the industrial process in Japan. As I mentioned before, we talked about sushi and tuna. In this particular situation, mercury was being used in the industrial process.

It was being released to a stream system, ultimately into a reservoir—maybe not necessarily a reservoir as it was a lake, per se. That lake was used for subsistence fishing. Many of the people within the community began to get sick as a result of methylmercury poisoning, and in general, mercury poisoning. Several researchers and doctors traced it back to the activities that were happening at this particular industrial plant.

That, to this day, has sparked many of the conferences that are going on within the mercury community. Every two years, everyone who does research on mercury transformations in the environment attends the conference called the International Conference on Mercury as a Global Pollutant. It moves around the world, roughly every two years.

As a result of that situation in Minamata, Japan, much of the foundational work that has gone on within the community has focused on trying to understand how methylmercury is being produced in the environment and cycled in the environment, and then ultimately, how it biomagnifies up the food chain.

While I can’t speak directly to strategies to detoxify methylmercury, people who may experience high levels of methylmercury, that one anecdotal story speaks to how we discovered it.

Kelly: I think I’ve seen a photographic album of the victims of that poisoning, and it’s just crippling.

Pierce: Yeah, it’s crippling.

Kelly: It’s terrible.

Pierce: It’s crippling. Neurological effects. Methylmercury affects fine motor skills.

We don’t send everybody to the conference every year. It’s travel to places like Japan or China, Asi. You have to select a few. But I’ve had colleagues come back from the conference and just mention that in some cases, people who were victims, or who had family members that were victims are in some of those photos—which is one of the reasons why we don’t show the photos at all—explain and interact with many of those family members or descendants who had family members that were impacted. And have discussions with them about the importance of the work that we’re doing.

Much of the team that’s here at ORNL, as well as many other researchers across the country, that serves as extra motivation to want to understand it and to help not only DOE, but others across the globe design ways to mitigate the issue.

Kelly: That’s great. Are there other aspects of your mission that you want to talk about?

Pierce: One comment I do want to make is simply speak to the unique environment of the laboratory. I don’t think I can emphasize that enough. From the historical mission, the national labs were built to very simply beat Hitler in building a nuclear bomb. The world today has been forever changed as a result of that intense focus of a variety of scientists from a variety of different disciplines tackling a challenge that at the time seemed insurmountable. They did it short order.

An anecdotal story to that is somewhat similar to the discovery of the two gene cluster in the project. The ability of the national lab to bring together these multidisciplinary teams that first and foremost have to figure out how to communicate with one another, similar to me communicating science to my mom.

Then, after they figure out how to communicate with one another, they have to figure out how to exchange those ideas in a productive manner to address a really, really challenging problem. I talked about one: how does mercury convert to methylmercury in the environment, and how do we resolve that challenge?

The project started in 2010, and a number of the scientists had this quest. How is mercury being converted? How are microbes that live in these oxygen-deficient zones converting inorganic mercury to methylmercury? How are they doing it?

For forty years, people had been looking for this and trying to resolve this issue. In three years, this multidisciplinary team, who had not done any mercury research prior to this time—although the laboratory has a long history of mercury research. Whether atmospheric transport of mercury through work that Steve Lindbergh did when he was here—he was a former lab fellow—or work that people along the lines of George Southworth. Many of these folks are retired now. The lab has had a long history.

But this collection, this team that was brought together roughly nine years ago had not done anything in the area. They were starting from scratch. They had to go from reading the literature, understanding the literature. Collaborating with others in the community. That was key, because there were a number of different people, both in our science advisory board as well as collaborators that were on the project, that had done some mercury research—had done a fair amount, actually.

But, again, bringing this collection of computational scientists, biophysicists who are using neutrons to study protein crystals, geochemists, just regular chemists, microbiologists, people who understand genetics, all together, figure out how to talk to one another, and solve a forty-year mystery in three, speaks to the power of the labs.

What has me here today, what made me accept a position at PNNL when I first was exposed to the lab, was that. The scale of the nuclear facilities that were built as a result of the Manhattan Project, recognizing they did that again in short order.

Then this kind of thing that was done here in Oak Ridge, in three years solving something that was forty, speaks to the lab’s power of bringing these multidisciplinary teams together. Tackling something that is in the national interest, and doing it in short order to resolve these really, really, really, really, really challenging problems. It makes it exciting, because the discoveries that will come out into the future, given ORNL’s 75-year history, will be quite impactful, in my mind at least, in my opinion, I’ll say.

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