Transport of Polycyclic Aromatic Hydrocarbons in Unsaturated Porous Media.

Polycyclic aromatic hydrocarbons (PAHs) are complex organic molecules containing 2 or more fused benzene rings. Some of these compounds such as fluoranthene are known to be human carcinogens and mutagenic to mammals. Being hydrophobic and non-polar, PAHs tend to partition to the organic matter in the soil from bulk aqueous phase. Though transport of these contaminants has been well studied in saturated environment, interactive mechanisms of these fluorescent compounds in unsaturated (identified by presence of air-water interface) porous media need to be yet explored. The objective of our study is to assess the transport of fluoranthene in unsaturated porous media with moving air-water interfaces. We used confocal microscopy (emission wavelength: 444 nm for fluoranthene) to visualize the interactions of fluoranthene particles in a glass channel (i.d. 3.7 mm x 7.5 cm) packed with quartz glass beads (dia. 0.5 μm). Acid-washed glass beads were inoculated with ethanol-dissolved fluoranthene prior to packing. The packed glass channel was used to mimic a porous media and effects of an advancing and receding capillary fringe on the detachment of fluoranthene.