Crude Oil Contamination in the Shallow Subsurface: Bemidji, Minnesota
To help understand the geochemical conditions that control arsenic mobilization in the subsurface
scientist uses a syringe to withdraw water from a core for analysis. The core sample was collected using the "freezing drive shoe" technology developed by USGS
scientists. The freezing drive shoe enables nearly complete core recovery from saturated, sandy aquifers. The core is shrouded in aluminum foil to prevent oxidation. Photo Credit: Jeanne Jaeschke, USGS
scientists collecting a groundwater sample from a well at the USGS
Bemidji Crude-Oil Spill Research Site, Minnesota. The scientists monitored in real time the dissolved oxygen, pH, specific conductance, and temperature of the water as the well is pumped so they can know when to collect a representative sample. USGS
scientists measured concentrations of oil breakdown products at greater concentrations than parent compound
. Photo Credit: Jared Trost, USGS
Map of surface oil areas resulting from the pipeline rupture at the Bemidji Crude Oil Spill Research Site, Minnesota
. The map delineates areas where the oil pooled in the subsurface, where oil drained, where oil sprayed from the rupture, and where soil was removed.
Oblique areal view of the crude oil spray area at the pipeline rupture site. USGS
scientists and others have been studying the long-term fate of the spilled crude oil.
Conceptual model of the subsurface contaminant plume's microbial geochemistry. The model shows the right to left progression of what electron acceptors are being used by subsurface microbial communities to degraded dissolved oil constituents in groundwater.
Collecting vapor samples from contaminated areas in the unsaturated zone. The USGS
scientist is using a syringe to extract air from a small sampling tube that extends into the subsurface.
scientists cutting a frozen core for later biogeochemical analysis. Freezing the core keeps the natural pore fluids in place. The scientists have been studying the natural attenuation of a plume of dissolved constituents in groundwater that resulted from a crude oil spill.
A scientist operating a gas chromatograph in an onsite laboratory. The onsite laboratory enables the scientists to make measurements quickly so sampling plans can be adjusted on the fly.
Installing a tensiometer in the unsaturated zone prior to a tracer test. Tensiometers are used to measure water pressure in the unsaturated zone.
scientist measuring hydrogen gas in groundwater samples in the onsite laboratory at the Bemidji Crude Oil Spill Research Site, Minnesota. Hydrogen is an important intermediate compound that is both produced and consumed during biodegradation. The hydrogen gas concentrations can help identify the types of microbial communities that are degrading contaminants.
scientists conducting a subsurface tracer test at the Bemidji Crude Oil Spill Research Site, Minnesota. The scientists use tracer tests to study subsurface contaminant transport processes.
scientist working on geochemical characterization of the contaminant plume at the site. A multidisciplinary team of scientists from the USGS
and other organizations have been studying the natural attenuation of crude oil in the subsurface.
scientist collecting an unsaturated-zone gas sample with a syringe from a vapor sampling well. The sample was used to study the natural attenuation of hydrocarbon vapors in the unsaturated zone.
scientists conducting a ground penetrating radar (GPR) survey at the south subsurface oil pool. GPR can help delineate the extent of oil in the subsurface.
scientist lowers borehole radar into a borehole near the Naval Industrial Reserve Ordnance Plant, Fridley, Minnesota. The investigative approaches the scientists used at this site were developed as part of the Bemidji Crude Oil Research Site, Bemidji, Minnesota
Soil moisture probes and tensiometers installed in the side of a pit for monitoring a tracer test in the unsaturated zone. Note black oil-contaminated sand on pit walls.
Geochemical zones in the subsurface plume of dissolved constituents at the Bemidji Crude Oil Spill Site, Minnesota
. Each zone has a unique microbial community that's actively degrading the dissolved constituents.
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