84283
Hydrologic Effects on Subsurface Transport of Surface-Applied Solutes and Bacteria in a Vadose Zone-Shallow Groundwater Continuum.

See more from this Division: Oral sessions
See more from this Session: TRACK 1--Treatment and Fate of Contaminants
Tuesday, April 8, 2014: 3:00 PM
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Sergio Manacpo Abit Jr.1, Aziz Amoozegar2, Michael J. Vepraskas3 and Chris P. Niewoehner2, (1)Oklahoma State University, Stillwater, OK
(2)North Carolina State University, Raleigh, NC
(3)Department of Soil Science, North Carolina State University, Raleigh, NC
Better understanding of the subsurface transport of contaminants is vital to their proper monitoring and treatment. This study evaluated the effects of groundwater (GW) flow velocity and water table (WT) fluctuation on the extent of horizontal transport of solutes and bacteria in the capillary fringe (CF) and GW underneath an onsite septic system.  Experiments were conducted using a sand-packed 90 × 50 × 3.5 cm flow cell to visually evaluate the transport of a surface-applied dye solution and fluorescent Escherichia coli suspension in the vadose zone and GW under various simulated hydrology. A simulated GW was established at the bottom 12 cm of the flow cell. Dye solution or E. coli suspension was applied to an area on the surface of the flow cell and their transports were monitored.  Surface-applied solutes and microorganisms tended to be transported vertically in the vadose zone but were transported horizontally above the WT when it reached the CF.   At high flow velocity, horizontal transport of surface-applied contaminants were confined to the upper portion of the CF but moved deeper into it and eventually below the WT at slower lateral GW flow velocity. Surface recharge with water containing dye and microbes resulted in WT rise before the contaminants could reach the original WT. Subsequent drainage dropped the WT without appreciably vertically leaching the dye and microbes that were in the CF prior to drainage. Monitoring of the vadose zone, particularly the CF, should be considered when monitoring the horizontal transport of soluble chemicals and suspended microbes in the subsurface.
See more from this Division: Oral sessions
See more from this Session: TRACK 1--Treatment and Fate of Contaminants