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(38-51) Fate and effects of ordnance compounds in marine environments. Nipper, Marion*,1, Carr, Robert2, Biedenbach, James2, Hooten, Russell2, Miller, Karen3, 1 Texas A & M University - Corpus Christi, Corpus Christi, Texas2 U.S. Geological Survey - Biological Resources Division, Corpus Christi, Texas3 Naval Facilities Engineering Service Center, Port Hueneme, California ABSTRACT- Several organic chemicals are well recognized as toxic to aquatic organisms, but the effects of their degradation products are often overlooked. Previous studies indicated that several ordnance compounds in seawater caused acute and chronic toxicity to marine organisms (SETAC-Europe, 1999). When marine sediments were spiked with some of the same compounds and analyzed for toxicity, the measured concentrations could not have been responsible for the extent of toxic effects exhibited (SETAC-Europe, 2000). Therefore, two of these ordnance compounds, picric acid (trinitrophenol) and 2,6-dinitrotoluene were selected for further studies with spiked samples. Biodegradation in marine sediments and photodegradation in seawater were assessed. Sediment type, total organic carbon (TOC) content and temperature strongly influenced biodegradation rates. Both picric acid and 2,6-DNT were totally biodegraded 24 hours after spiking into a muddy sample with 1% total organic carbon (TOC), when kept at 20°C. In a sandy sediment with 0.1% TOC, total degradation of 2,6-DNT and picric acid only occurred after 14 and 28 days, respectively. When sediments were kept at 10°C, 2,6-DNT biodegradation was remarkably slower, particularly in the sandy sediment. This chemical was totally degraded after 3 days in the muddy sample, but 46% of the original concentration still remained after 28 days in the sand. The main initial biodegradation product of 2,6-DNT was identified as 2-methyl-3-nitroaniline. Pore waters containing this degradation product were significantly more toxic than pore waters containing primarily the parent compound. Further toxicity assessments of bio- and photodegradation products of both ordnance compounds are underway and an update will be presented. Key words: ordnance compounds, marine toxicity, photo-degradation, biodegradation |
