Science Center Objects

Reston Biogeochemical Processes in Groundwater Laboratory (RBPGL) research on hydrocarbons and biofuels is aimed at understanding the controls on rates of hydrocarbon biodegradation and secondary effects in the shallow subsurface and at the mixing interface between groundwater and surface water bodies such as wetlands.

The RBPGLĀ has done long-term investigations at the Bemidji, Minn., crude oil spill site. Hydrocarbon biodegradation under various redox conditions is being investigated using innovative field experiments. Although in situ experiments are more complex than laboratory studies, they provide more realistic conditions because natural system complexities are maintained. The results of these studies provide insight into how hydrocarbon degradation rates are related to microbial communities and will contribute understanding of the controls on rates of natural attenuation processes. Using field and laboratory approaches we are also evaluating the influence of ethanol concentrations on biodegradation rates of fuel hydrocarbons. Few studies have looked at the impact of multiple competing organic compounds, such as when BTEX and ethanol are both present. This project is relevant to the current USGS efforts towards understanding the potential impact of a greater use of biofuels as an energy source in the future and fits within the societal goals of understanding the impact of human behavior on water quality and ecosystem health.

While monitored natural attenuation is widely applied as a remediation strategy for petroleum leaks and spills, there is little understanding of the secondary effects of hydrocarbon or biofuels biodegradation in situ. Previous studies document that the introduction of organics from human sources can drive iron reduction, resulting in release of naturally occurring metals from sediment. There is limited research on arsenic mobilization in dissolved hydrocarbon plumes. The Bemidji site is an ideal field location to examine arsenic mobilization. We are studying the dynamics and controls of arsenic concentrations in groundwater and sediment over time at the Bemidji site to examine the cycling of arsenic in hydrocarbon plumes. Arsenic is of particular concern because of its known toxicity and links to liver, bladder, and lung cancers.