Bacterial Transport - Oyster, Virginia

Virginia State Map Showing Enlargement of Delmarva Peninsula and Location of Oyster, Virginia

South Oyster Field Site Location Map Showing Locations of South Oyster, Wheatfield, and Narrow Channel Focus Areas and the Original Oyster Site.

In order to understand the bacterial transport field experiments, intact cores were collected from a quarry near the bacterial injection sites. Three different sedimentary facies were sampled which represents the range of sediment type encountered by the injected bacteria at the field site. The cores were collected by hammering aluminum tubes into the carefully excavated faces of the quarry. Care was taken to record the orientation of the tubes and the sedimentary structures captured inside each tube. The tubes were sealed in wax and packed in shipping boxes to prevent physical disruption of the sedimentary fabric during transport back to the laboratory. Microbial transport laboratory experiments will be performed on these cores to ascertain the degree of bacterial adhesion to different mineral phases in the sediments, particularly iron oxide. These experiments will be performed aerobically and anaerobically. 14C labeled bacteria with identical surface adhesion properties will be run through tubes representing the different sedimentary facies to determine the importance of subsurface heterogeneity to bacterial transport.

   At Envirogen, Inc. the tubes of intact core are mounted vertically. Radiolabelled bacteria are introduced from the bottom, water flows up in the columns. A pressure transducer (blue circle) measures the pressure difference at the influent and effluent end. A chloride probe is used to measure chloride inject into the influent end with the bacteria. The chloride acts as a conservative tracer. The cores are run in a cold room at 15°C which is the average temperature of the ground water. The water velocities vary from 0.5 to 2 m/day, straddling the range of natural ground water velocities. Bacterial breakthrough is monitored by measuring the 14C, 35S, or tritium in the effluent.

A cone-penetrometer rig was used by Golder Associates to sample both Sediment and water from depths up to 20 meters below the surface. An expert geologist (second figure from left) and an expert microbiologist (last figure on right) selected the locations.

Sediment cores 1.5" in diameter collected by CPT rig were sealed in Lexan Lines (for aerobic samples) and in white PVC tubes (for anaerboic samples). These samples were shipped on ice to microbiologists geochemists.

Peristaltic Pump

One hole (SO8) was made by the CPT rig were cased with a screened interval at approximately 7 meters depth. A peristaltic pump was used to purge the well and plastic carboys were filled with the water pumped from the well. This water remained anaerobic during the pumping process. The water will be used to perform small intact core bacterial transport experiments using the cores collected by the CPT. Additional samples were collected for ground water chemistry.

House in Oyster leased from the Nature Conservancy house the sample processing laboratory for the site.

An anaerobic glove bag (courtesy of Tommy Phelps of Oak Ridge National Laboratory) is used when processing samples of intact from the hypoxic zone at South Oyster for general distribution to Oyster investigators and collaborators. Argon is used to fill the glove bag. Samples are passed in and out through long cylindrical airlock. Processing tools are sterilized on site with alcohol and torch.

Related Links:
http://etd.pnl.gov:2080/IGGroup/oystertime.html

http://www.lbl.gov/NABIR/oyster.html

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