Biostabilization of Polycyclic Aromatic Hydrocarbons (PAH's) under Denitrification Conditions in Sediments

The research assessed the fundamental character of the binding of polycyclic aromatic hydrocarbons (PAH) compounds to sediments that make the PAHs more or less bioavailable and toxic. Complementary techniques were employed to provide direct microscale information on-the sequestration of PAH contaminants in Milwaukee Harbor sediment particles. Two-step laser mass spectrometry was used for PAH measurements, infrared microscopy was used for organic carbon measurements, and scanning electron microscopy with wavelength dispersive X-ray spectroscopy was used for elemental microanalysis. PAH concentrations on coal- and wood-derived particles were found to be several orders of magnitude higher than on silica particles. The coal/wood-derived particles constitute only 5% of the sediment by weight but contain 62% of the total PAHs. The remaining 38% are mainly in a clay and silt fraction. Desorption kinetic studies on these separated fractions revealed a relatively low availability of PAHs from the coal/wood fractions and a high availability from the clay/silt fractions. Preliminary work was done to understand the effects of degrading bacteria on contaminated sediment. The results indicated that bacteria and PAHs are co-located on the particles and degradation should not be hampered by spatial considerations.