John Bargar Joins EMSL as Environmental Transformations and Interactions Group Leader

Science has always been a passion of John Bargar, the new Environmental Transformations and Interactions group leader at the Environmental Molecular Sciences Laboratory. In fact, he has never considered doing anything else. 

As a child, Bargar was passionate about astronomy, studying stars, constellations, and planets. In high school, he found his way to field-based science that affects Earth and its systems. As a student, he conducted an amateur ecology project over several years that helped understand songbird nesting behavior. Looking back, he remarks that the project was where he discovered his love for field work, which eventually led to his current passion and research emphasis in metal micronutrients and contaminants in soils and natural waters.  

“I loved it and still love it,” he said. “Being outside and doing science. There are few things better.” 

Now a new member of the EMSL leadership team, Bargar said he is excited to blend his long-held passion for field work with his background in both molecular and large systems research as it applies to soil, water, and ecosystem health. 

“As a geoscientist, I have been trained to think about large systems,” he said. “To me, large systems are really cool and I want to know how the different parts like rivers and aquifers interact. But as a biogeochemist, I want to know what molecular species are present, about their molecular structures and compositions, and what is controlling their behavior in soils. You can’t get the full picture of either unless you study both perspectives at the same time.” 

EMSL, he said, focuses on exactly those areas. 

Previous connections with EMSL 

For more than 25 years, Bargar has led projects pertaining to both molecular structure and system-scale research with respect to the behavior of essential metal micronutrients and metal contaminants in soils and natural waters. Throughout that time, he has worked with researchers and instrumentation at EMSL as an external user, including for research projects through his previous role as the lead scientist for the geosciences group at the SLAC National Accelerator Laboratory (SLAC). His previous experience with and knowledge of PNNL and EMSL’s expertise and capabilities are what excites him most about joining the team at EMSL. 

“I have watched PNNL staff doing strong science and providing leadership to the community,” he said. “EMSL is among the premier Earth sciences molecular-scale research laboratories in the United States and has teams of researchers with a range of expertise. Moreover, we have some of the very best tools and very brightest minds to deploy on Earth sciences problems here at EMSL. Who wouldn’t be drawn here?” 

Before joining EMSL, Bargar led the SLAC geosciences program, including the Department of Energy's Biological and Environmental Research program SLAC Floodplain Hydro-Biogeochemistry Sciences Focus Area project, the SLAC-led multi-laboratory nuclear forensics research program, and the SLAC deep subsurface geochemistry project. Through many projects at SLAC, he utilized both the instrumentation and expertise of researchers at EMSL to contribute to his work. 

Important discoveries in metals and contaminant behaviors 

At the molecular level, Bargar’s research has contributed important findings and models of metal behavior in soils and groundwater. Coordinated laboratory and field work conducted by Bargar and his team discovered that uranium behavior in contaminated soils at legacy DOE sites is controlled by short seasonal “hot moments” when water tables and dissolved oxygen are elevated. 

At the larger systems scale, Bargar’s research focused on understanding how, where, and when molecular reactions occur and interact across larger distances, from floodplains to regions. For example, laboratory studies coordinated with field sampling performed by Bargar’s team showed that soil organic matter interactions control uranium accumulation and release in soils across the entire upper Colorado River Basin where these interactions moderate persistent uranium groundwater contamination.  

“The implications of this work are that we now have the ability to construct conceptually accurate models to predict the fate and transport of uranium, which was not previously possible for these sites,” he said. 

He and the SLAC science focus area group also studied how hydrology controls the stability and reactivity of iron-bearing colloids, which are tiny and reactive nano-scale minerals that don’t settle, in floodplain soils and groundwater near rivers and streams. Colloids help transport iron and other micronutrients, as well as contaminants, in natural waters. Ongoing work being performed by postdoctoral researchers at SLAC is identifying how those colloids are transported to rivers where they contribute to iron exports from watersheds. 

“We studied the molecular structures of these colloids, but also the non-chemical factors that control their system-scale behavior,” he said. 

Excitement for the future 

Now joining EMSL as a member of its leadership team, Bargar said he is most excited to help support efforts as they pertain to EMSL’s Molecular Observation Network (MONet), one of the major strategic priorities for EMSL. The strategic initiative is an effort to develop a national network of environmental sampling and sensing sites to produce comprehensive molecular, as well as physical, data on the composition and structure of soils and microbial communities through time. This comprehensive new information will help improve the span and accuracy of multiscale models of Earth systems. 

“Most scientists collect samples at specific sites at specific moments in time,” Bargar said. “This is the conventional approach. One major problem with this approach is that we miss a lot of important short-lived dynamics—so called ‘hot moments’—because they happen in between our sampling times. But with community collaboration supported by MONet, we can enable a national effort to continuously collect samples and advanced soils data from a network of sites and sensors that use novel measurement capabilities still under development.” 

Bargar said MONet is both an intimidating endeavor because it is a big project still building out with many uncertainties and also incredibly exciting because of the scope of what it can accomplish. 

“This approach resonates directly with my sensibilities of understanding how molecular processes are occurring over landscapes, and it is inherently a field-oriented strategy,” he said. 

Bargar said he is excited to get started on his work at EMSL right away supporting and leading the Environmental Transformations and Interactions group. He is also looking forward to working with and supporting the next generation of scientists and leaders—those who are student interns, postdoctoral researchers, and others early in their career, as well as mid-career staff. Serving as a mentor and enabling scientists’ careers, he said, has been one of the most rewarding parts of his career. 

“To all of my colleagues at PNNL who have been so supportive and welcoming before I even arrived, thank you,” he said. “I really want to get rolling, and I’m looking forward to being much closer and working together.” 

Bargar is the author of more than 190 scholarly articles and has contributed to six journals as a reviewer. 

He received his Bachelor of Science in geology from The Ohio State University and a PhD in geological and environmental sciences from Stanford University. He completed a National Research Council postdoctoral fellowship with the U.S. Geological Survey. 

For more information on Bargar, view his bio on the EMSL website.