Mitigation of Acid Mine Drainage and Other Contamination in the Prince William Forest National Park in Northern Virginia

Michael Komelaslky, Douglas Mose and George Mushrush, Chemistry Department, George Mason University, Fairfax, VA 22030,  Tel/Fax: 703-273-2282

Prolonged use of northern Virginia forests produced contamination problems in an area that is now a new National Park.  Pyrite mining of shallow hydrothermal ore deposits for about 50 years, which ended about 50 years ago, produced mine tailings that still produce acidic and metal-enriched groundwater to the local streams and wetlands. Military training facilities contributed vehicle fuels lubricants, and some metal contamination. Recently, relatively dense housing developments contribute road runoff. Measurements of stream waters and stream sediment throughout the park reveal that mitigation efforts have significantly reduced or eliminated most of the contamination, though the acid mine drainage still is present, in spite of extensive remediation efforts.  

Monitoring Changes in Microbial Ecology during Sulfate Amendment of a BTEX-Contaminated Aquifer using Bio-Sep Traps

Kerry Sublette, University of Tulsa, Tulsa, OK
Aaron Peacock, University of Tennessee, Knoxville, TN
Ravi Kolhatkar, Group Environmental Management Co. (BP), La Palma, CA
Dennis Beckman, Group Environmental Management Co. (BP), Tulsa, OK
David Cook, GeoEngineers, Seattle, WA
David White, University of Tennessee, Knoxville, TN
Thomas Mathew, University of Tulsa, Tulsa, OK
Chintan Mehta, University of Tulsa, Tulsa, OK
Greg Davis, Microbial Insights, Inc., Rockford, TN

A gasoline-contaminated aquifer in Washington state has been under remediation since 1999 using soil-vapor extraction and catalytic oxidation following a period of free product removal.  By late 2002 the highest benzene concentrations in the plume were 0.8-4 mg/L.  A field trial is currently underway to enhance natural attenuation of hydrocarbons at the site by amending the aquifer with sulfate which is introduced into the aquifer using an infiltration trench in 1000-gal batches at a concentration of 500 mg/L. 

Bio-Sep^® consists of 3-4 mm diameter spherical beads engineered from a composite of 25% aramid polymer (Nomex) and 75% powdered activated carbon (PAC). The bulk density is about 0.16 g/cm³ with a porosity of 74%.  Beads are surrounded by an ultrafiltration-like membrane with pores of 1-10 microns.  Bio-Sep^® beads have been shown to be very effective in collecting biofilms which are believed to be more indicative of in situ microbial ecology than planktonic organisms from groundwater samples.  Bio-Sep^® beads may also be “baited” with potential remediation amendments during fabrication or loaded onto PAC post fabrication

Prior to initiation of the field trial five groundwater monitoring wells (one upgradient, three plume, and one fringe) were investigated to predict the effect of the sulfate amendment on subsurface microbial ecology by incubating two types of Bio-Sep^® traps in each well.   In each well one trap contained non-baited Bio-Sep^® beads.  The second trap contained both non-baited beads and beads in which Na₂SO₄ had been incorporated during fabrication.  The baited beads provided a source of slow-release sulfate in the trap to mimic the effect of sulfate amendment of the aquifer.  After 30 days of incubation the trap biofilms were analyzed using phospholipid fatty acid (PLFA) analysis and analysis of PCR-amplified 16S rDNA.

Biofilms from the sulfate-baited traps and the non-baited traps were shown to have distinctly different community structures.  Sulfate-baited traps were more likely to contain lipid anaerobic biomarkers, biomarkers for sulfate-reducing bacteria, and specifically identified anaerobes like Geobacter sp.  The aquifer is currently being monitored using non-baited Bio-Sep^® traps to determine whether the predicted shifts in the subsurface microbial ecology are observed as the sulfate amendment is introduced.

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