Little Wind
Slate Head Water
Riverton Fall

Groundwater Quality Science Focus Area

The SLAC SFA scientific program addresses the grand challenge: How do biogeochemical and transport processes in shallow alluvial groundwater systems (bedrock to soil) couple to one-another and control water quality under hydrologically variable conditions? We are identifying hydro-biogeochemical mobilization and retention processes for C, nutrients (P, S, and Fe) and contaminants (U, Mo, Pb, Zn) at molecular to meter scales. Emphasis is placed on understanding the spatio-temporal coupling of biogeochemical and hydrological processes in soil, the capillary fringe, and the upper portion of the saturated zone. Field studies at the mining impacted Coal Creek and Slate River head-watersheds (Gunnison county, CO) and the former ore processing site in semi-arid Riverton, WY are combined with laboratory experiments to understand the impact of timing, duration, and intensity of wet-dry cycling, transport direction, organic carbon content and sediment texture on redox and nutrient and contaminant mobilization. Quantitative process representations that are developed within the SLAC SFA program will be shared with collaborating SFAs and the wider community for incorporation into larger-scale models. Results from this work will advance short- and long-term prediction of water quality by DOE and multi-agency collaborations.

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SLAC SFA 2020 flyer

Meet the SLAC SFA scientists videos:

How an x-ray microprobe can solve groundwater quality problems

John Bargar at Slate River, CO

Recent Research Highlights

Microbial Communities in Floodplain Soils Remain Unchanged Throughout Seasonal Redox and Water Table Flux

Tolar, B.B., Boye, K., Bobb, C., Maher, K., Bargar, J.R., Francis, C.A. Stability of floodplain subsurface microbial communities through seasonal hydrological and geochemical cycles. Frontiers in Earth Science – Biogeoscience (in revision).

Highlight Slide

The Science  Microbial communities play a crucial role in environmental systems, mediating biogeochemical reactions through metabolic processes that can vary depending on environmental conditions. microbial_communities_floodplain_imagerv.jpgmicrobial_communities_floodplain_imagerv.jpg

FeS Nanoclusters Can Mobilize Fe and S from sediment to Groundwater

Noël, V., Kumar, N., Boye, K., Barragan, L., Lezama-Pacheco, J., Chu, R., Tolic, N., Gordon E. Brown Jr., G.E, Bargar, J.R. (2020) FeS Colloids – Formation and Mobilization Pathways in Natural Waters. Environmental Science Nano.,  Accepted Manuscript.  

DOI: 10.1039/C9EN01427F

Highlight Slide

Ferrihydrite Sulfidation Promotes FeS Nanocluster Formation.   Read more >

Bone_ESTComplexation by Organic Matter COntrols Uranium Mobility in Anoxic Sediments

Bone, S.E.; Cliff, J.; Weaver, K.; Takacs, C.J.; Roycroft, S.; Fendord, S.; Bargar, J.R. Uranium complexation by organic matter and clay minerals in anoxic contaminated sediments. Environmental Science and Technology 2020, 54, 1493-1502.

Highlight Slide

Uranium(IV) adsorbs to organic matter in anoxic alluvial sediment, which may be mobilized through desorption and colloidal release. Read more >

For more research highlights read more>

Contacts and Websites

Principal Investigator

John Bargar,, (650) 926-4949


This program is funded by the Subsurface Biogeochemistry program within the U.S. Department of Energy, Office of Biological and Environmental Research, Climate and Environmental Sciences Division. Funding for SSRL is provided by the Department of Energy, Office of Basic Energy Sciences.

BER Program Managers

David Lesmes,, (301) 903-2977

Paul Bayer,, (301) 903-5324