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Sediment Quality Assessment and Management: Insight and Progress Edited by M. Munawar© 2003 Ecovision World Monograph Series Aquatic Ecosystem Health & Management Society Laboratory assay of TNT (2,4,6-trinitro-toluene) fate and toxicity in seawater and sediment G. Dave*, E. Nilsson Department of Applied Environmental Science, University of Göteborg, Box 464, 405 30 Göteborg, Sweden. goran.dave@miljo.gu.se Keywords: Nitocra, dumping, munition, ammunition Introduction Military munition has been dumped in both freshwater and seawater, but the fate and the effects of these dumpings are unknown. Dumping has often been made at considerable depths and, therefore, it is difficult to locate the material and also to study the fate and possible effects of the chemicals that may leach from the munition. Trinitrotoluene (TNT) is a major explosive in the dumped munition. Its fate and effects have mainly been studied in soil and freshwater systems so far. The objective for this study was to determine the toxicity of TNT added to a sediment water system at a laboratory scale in order to determine disappearance rates for TNT toxicity and parent TNT in water. Materials and methods Technical munition TNT was added from a stock solution in acetone at various concentrations to a series small glass tubes. After evaporation of the acetone, the tubes with the dry TNT were distributed in Petri dishes (i.d. 10 cm; volume 50 ml) with 5 g of clean sediment and 45 ml of diluted seawater (7 psu). After addition of a small amount of fish feed and some algae (2.5 106 cells of Selenastrum capricornutum), 10 juvenile harpacticoid copepods (Nitocra spinipes) were added, and the dishes were incubated at room temperature (20-24 o C) at complete darkness. The number of living Nitocra was determined after 7 weeks. Then the 208 glass tubes with remaining TNT, which had not leached out and dissolved in water were removed, the water phase was sucked away and discarded, and clean seawater (7 psu) and 10 new juvenile Nitocra spinipes were added to each dish. After 96 h the number of living Nitocra was recorded. Then the water phase was sucked away again and discarded, and clean seawater (7 psu) and 10 new juvenile Nitocra spinipes were added to each dish. Survival was recorded again after another 96 h. The concentration of TNT in the water after the renewal was analysed spectrophotometrically according to Crockett et al. (1996). Results The results from the entire experiment are presented in Fig. 1. Survival of Nitocra spinipes is presented as the mean value of 4 replicates and the standard deviation (SD) in the Petri dishes with sediment and water amended with a TNT containing object after 7 weeks (Fig. 1a). The number of surviving animals is then the result of both survival and reproduction. The results in Fig. 2b is the survival of new juveniles of Nitocra spinipes, which were added after removal of the miniature missile with TNT and the old water phase, and subsequent addition of new water. After recording survival after 96 h and renewal of the water phase the survival was tested again during a new 96 h period. In replicates 1 and 2, sediment from a sandy location was used, and in replicate 3 and 4 another sediment with more mud (organic carbon) was used. The analysis of variance (ANOVA) for number of living Nitocra after 7 weeks (shown in Fig. 1a) proved that survival in all TNT concentrations was significantly different from the control and the acetone control (p<0.05). However, no significant effect of sediment type was detected. The analysed concentration of TNT in water was 6.3 mg l-1 at the highest nominal concentration (1000 mg l-1 ) after the first renewal. After the first renewal of the water phase, the survival of the added Nitocra spinipes was affected in all tested total concentrations, but after the second water phase removal there was only a slight reduction of survival at the highest concentration of TNT. After the second renewal of the water phase no TNT was detected in any of the treatments. The detection limit by the analytical method was 0.2 mg l-1 . Discussion The present results showed that TNT dissolved passively from an object added to a sediment-water system and affected Nitocra spinipes significantly at nominal maximum theoretical concentrations down to at least 10 mg l-1 . The 96-h LC50 of TNT for Nitocra spinipes is around 7 mg l-1 , and this value is not immediately affected by sediment addition, but toxicity decreases by time in the presence of sediment, and this is presumably due to biotransformation (Dave et al., 2000). Therefore, the long-term effect at 10 mg l-1 seen in this study is consistent with the results from Dave et al. (2000). The present results also showed that TNT was still present in the system after removal of the contaminated object and the renewal of the water phase. This shows that TNT and/or its toxic transformation products will bind to the sediment, but also that TNT and/or its toxic metabolites can be leached out with water. The analysed concentrations of TNT in the renewed water phases of the 1000 mg l-1 nominal concentration were 6.3 mg l-1 and <0.2 mg l-1 Fig. 1a. Number of surviving Nitocra spinipes after 7 weeks in Petri dishes with added TNT. TNT was added in miniature missiles at the theoretical maximum nominal concentrations shown and inoculated with 1 juveniles at time 0. The survival is given as mean and SD for all 4 replicates. 209 210 after the 1st and 2nd water phase renewal, respectively. These concentrations are consistent with the recorded effects shown in Fig 1b. These results show that objects with TNT will leach into water, and that TNT will bind to the sediment. This is not surprising considering its water solubility of 130 mg l-1 at 20 o C and its Koc of 1600. The volatilisation of TNT is expected to be slow based on its calculated Henry’s Law Constant of 4.57x10-7 atm-cu m/mole at 20 o C (Lyman et al., 1982). The present experiment was made at room temperature (20-24 o C), which is much higher than the temperature in Swedish marine waters, where bottom temperatures are typically around 5-10 o C. Temperature affects the rates of both abiotic and biotic processes like leaching, adsorption, desorption and degradation/ biotransformation. Therefore, the overall fate and effects may be different in the field and than in this laboratory experiment. Other laboratory experiments with radiolabelled TNT have shown that some degradation products of TNT bind very strongly to sediment (Achtnich et al., 1999; Wikström et al., 2000). This suggests that remains of TNT will be present in the sediment for a long time even after the source of TNT has disappeared. Other desorption tests at 4 °C have shown that the remaining TNTconcentration after repeated leaching was about 10 to 20 mg TNT kg-1 dry sediment (Eriksson, 1997). Summary TNT (2,4,6-trinitrotuluene) is a major explosive found in dumped munition. The objective for this study was to determine its toxicity, when added to a sediment water system at a laboratory scale in order to determine disappearance rates for toxicity and parent TNT in water. The experiment was performed in Petri dishes with marine sediment, brackish water and small amounts of TNT added in open miniature missiles made from glass. All dishes were inoculated with the harpacticoid copepod Nitocra spinipes and some nutrients and incubated in complete darkness at room temperature (20-24 o C) for 7 weeks. After recording the survival and reproduction, the miniature missile and the water phase was removed. New water was added, tested for survival of new Nitocra spinipes. This renewal and testing of the remaining sediment and the new water phase was repeated once more. The results showed that TNT was dissolved passively from an object added to a sediment-water system and affected Nitocra spinipes significantly at nominal maximum theoretical concentrations down to at least 10 mg l-1 . The present results also showed that TNT was still present in the system after removal of the contaminated object and the renewal of the water phase. This shows that TNT and/or its toxic transformation products will bind to the sediment, but also that TNT and/or its toxic metabolites can be leached out with water. This means that objects with TNT will leach into water, and that TNT will bind to the sediment. This is not 211 surprising considering its water solubility of 130 mg l-1 at 20 o C and its Koc of 1600. The actual rate of disappearance, fate and effects at a dumping site is expected to be affected by sediment burial, temperature and water renewal rate. Acknowledgements This study has been supported by a research grant from the Environmental Department, Swedish Armed Forces, Stockholm. References Achtnich, C., Sieglen, U., Knackmus, H.-J., Lenke, H., 1999. Irreversible binding of biologically reduced 2,4,6-trinitrotoluene to soil. Environ. Toxicol. Chem. 18,2416-2423. Crockett, A.B., Craig, H.D., Jenkins, T.F., Sisk, W.E., 1996. Field sampling and selecting on-site analytical methods for explosives in soil. EPA/540/R-97/501, November 1996. U.S. Environmental Protection Agency. 33 pp. Dave, G., Nilsson, E., Wernersson,A.-S., 2000. Sediment and water phase toxicity and UV-activation of six chemicals used in military explosives. Aquatic Ecosystem Health and Management, 3,291-299. Eriksson, L., 1997. TNT in Baltic Sea sediment – adsorption and desorption. FOA-R—96-003438 .7—SE. Defence Research Establishment, Umeå, Sweden. 27 pp. Lyman, W.J., Reehl, W.F., Rosenblatt, D.H., 1982. Handbook of Chemical Property Estimation Methods: Environmental behaviour of organic compounds, McGraw-Hill, NY, pp.15-29. Wikström, P., Andersson, A.-C., Nygren, Y., Sjöström, J., Forsman, M., 2000. Influence of TNT transformation on microbial community structure in four different lake microcosms. J. Appl. Microbiol. 89,302-308. ...

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Additional Information

ISBN
9780993918452
Related ISBN
9788178982328
MARC Record
OCLC
933516293
Pages
378
Launched on MUSE
2016-01-01
Language
English
Open Access
No
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