W11 PM Advances in Biorestoration Strategies for Contaminated Sediments
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 343-344
(MON-1117-823640) Biodegradation of nitrogenous energetic compounds in coastal ecosystems.
Montgomery, Michael1, Osburn, Christopher1, Boyd, Thomas1, Hamdan, Leila1, Walker, Shelby1, 1 Naval Research Laboratory, Code 6114, Washington, DC, USA
ABSTRACT- Mineralization rates of nitroaromatic energetic compounds (NECs) in sediment were measured during surveys on eight research cruises. Surface sediments were collected over a three year period in Chesapeake Bay, San Francisco Bay, and two tropical locations off the coast of Oahu. Radiolabeled (14C) 2,4,6-Trinitrotoluene (TNT), 2,4-Dinitrotoluene (DNT), and 2,4-Diaminotoluene (DAT) was used in rapid (24 h) assays of submerged sediment and seawater to determine mineralization rates. Cruises conducted in September 2002, September 2003, and March 2004 in the Chesapeake Bay yielded the highest average NEC mineralization rates among the different locations, with average September 2003 values exceeding 0.25 g 
g-1 day-1. These mineralization rates were often an order of magnitude higher than those for three polycyclic aromatic hydrocarbons (PAHs), naphthalene, phenanthrene, and fluoranthene, despite the ubiquity of PAHs and the lack of known current inputs of NECs to the Chesapeake Bay system. The Pacific stations demonstrated significantly lower NEC mineralization rates, equivalent to PAH mineralization rates in the same locations. In general, mineralization rates of TNT were faster than those for DNT or DAT when comparing subsamples from the same location. Using natural bacterial assemblages from seawater collected during the March 2005 Chesapeake Bay cruise, it appears that this may be due to differential uptake and incorporation rate by bacteria which was greater for TNT than for either DNT or DAT. Despite the lack of exposure to exotic nitrogenous compounds, like TNT, natural assemblages may rapidly metabolize these compounds due to nitrogen limitation of bacterial growth in coastal estuarine and marine ecosystems.
Key words: sediment, bacteria, biodegradation, TNT