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Eitzer, B. D.; Hites, R. A. Enuiron. Sci. Technol. 1989,23, 1389-1395. Hall, D. J.; Upton, S. L. Atmos. Enuiron. 1988, 22, 1383-1394. Hessen, T. C.; Young, D. R.; McDermotbEhrlich, D. Atmos. Enuiron. 1979, 13, 1677-1680. Christensen, E. J.; Olney, C. E.; Bidleman, T. F. Bull. Enuiron. Contam. Toxicol. 1979, 23, 196-202. Murphy, T. J. Atmos. Enuiron. 1981, 15, 206-207. Koester, C. J. Ph.D. Thesis, Indiana University, Bloomington, IN, 1991. Gatz, D. F.; Dingle, A. N. Tellus 1971, 23, 14-26. Lindberg, S. E. Atmos. Enuiron. 1982, 16, 1701-1709. Eitzer, B. D. Ph.D. Thesis, Indiana University, Bloomington, IN, 1989. Ligocki, M. P. Ph.D. Thesis, Oregon Graduate Center, Beaverton, OR, 1986. Yamasaki, H.; Kuwata, K.; Miyamoto, H. Environ. Sci. Technol. 1982, 16, 189-194. Bidleman, T. F.; Foreman, W. T. In Sources and Fates of Aquatic Pollutants; Hites, R. A,, Eisenreich, S. J., Eds.; American Chemical Society: Washington, DC, 1987, pp 27-56. Tsai, W.; Cohen, Y.; Sakugawa, H.; Kaplan, I. Enuiron. Sci. Technol. 1991,25, 2012-2023. Ligocki, M. P.; Leuenberger, C.; Pankow, J. F. Atmos. Environ. 1985,19, 1609-1617.
Ligocki, M. P.; Leuenberger, C.; Pankow, J. F. Atmos. Enuiron. 1985, 19, 1619-1626. Ambre, Y.; Nishikawa, M. Atmos. Enuiron. 1987, 21, 1469-1471.
Lim, B.; Jickells, T. D.; Davies, T. D. Atmos. Enuiron. 1991, 25A, 745-762. Bidleman, T. F.; Christensen, E. J. J. Geophys. Res. 1979, 84, 7857-7862. Eisenreich, S. J.; Looney, B. B.; Thornton, J. D. Enuiron. Sci. Technol. 1981, 15, 30-38. Farmer, C. T.; Wade, T. L. Water,Air, Soil Pollut. 1986, 29,439-452. Sievering, H. Atmos. Enuiron. 1987, 21, 2179-2185. McVeety, B. D.; Hites, R. A. Atmos. Enuiron. 1988, 22, 511-536. Broman, D.; N 8 , C.; Zebiihr, Y. Enuiron. Sci. Technol. 1991, 25, 1841-1850. Koester, C. J.;Hites, R. A. Enuiron. Sci. Technol. 1992,26, 502-507. Orth, R. G.; Ritchie, C.; Hileman, F. Chemosphere 1990, 18, 1275-1282. Atkinson, R. Sci. Total Enuiron. 1990, 104, 17-33.
Received for review December 17,1991. Accepted March 30,1992. This work was supported by U.S. Department of Energy Grant 87ER- 60530.
Evidence for Rapid, Nonbiological Degradation of Tributyltin Compounds in Autoclaved and Heat-Treated Fine-Grained Sediments Peter M. Stang,",t Richard F. Lee,$and Peter F. Seiigmans Applied Technology Division, Computer Sciences Corporation, 4045 Hancock Street, San Diego, California 92 1IO, Skidaway Institute of Oceanography, P.O. Box 13687, Savannah, Georgia 31416, and Naval Ocean Systems Center, Code 52, Environmental Sciences Division, San Diego, California 92152-5000
Sterilized sediments, high in silt and clay content, from various sites in the United States rapidly degraded added 14C-labeledtributyltin (TBTX) or unlabeled TBTX to dibutyltin (DBTXJ, monobutyltin (MBTX,), and inorganic tin. This degradation was primarily abiotic, as documented by similar degradation rates between sterilized and nonsterilized sediment. Degradation occurred in two phases, with a rapid degradation phase (23-94%) after 2 days, followed by slower degradation rates of the remaining TBTX during the next 5-7 days. DBTXz is the primary degradation product found when TBTX is added to marine water, with very little production of MBTX,. For our sediment studies, as well as those of others, the primary degradation product when dissolved TBTX is added to fine-grained sediment was MBTX,. MBTX, is formed in the sediment and, because of ita hydrophilic nature, enters the water shortly after its formation. We suggest that production of MBTX, by bottom sediments is why the ratios of MBTX,/TBTX were significantly higher in bottom water than surface water in a San Diego Bay marina.
Introduction Tributyltin compounds have been and currently are in use as biocides in marine antifouling paints and have been found in marine waters and sediments in areas exposed *Author to whom correspondence should be addressed. Current address: 3631 Caminito Carmel Landing, San Diego. CA 92130. +Computer Sciences Corp. Skidaway Institute of Oceanography. 9 Naval Ocean Systems Center. 1382
Environ. Sci. Technol., Vol. 26, No. 7, 1992
to marine traffic (1-6). Several studies have reported degradation of tributyltin compounds in water (7-9) and in sediment and soil (1G12). Degradation by bacteria and algae was determined to be primarily responsible for the degradation of tributyltin compounds to less toxic products. Although tributyltin compounds in pure form may exist as the chloride, fluoride, hydroxide, oxide, or other species, we shall refer to tributyltin in the generic form. Therefore, we shall refer to tributyltin as TBTX, dibutyltin as DBTX2, and monobutyltin as MBTX,. In sediments, TBTX has often been associated with elevated concentrations of DBTX2 and MBTX, in the sediment. MBTX, and DBTXz were both found in conjunction with the presence of TBTX in harbor and marina sediments from Great Bay Estuary, New Hampshire (13). DBTX2 concentrations exceeded TBTX concentrations in the sediments of Poole Harbour, England, in five of seven survey periods (14). The authors suggested that microbial degradation of TBTX to DBTXz was taking place and presumed DBTXz degraded to MBTX, and Sn, although these compounds were not analyzed for. TBTX was detected in three of four sediment samples and DBTXz in all four samples collected from Lake Biwa, Japan (15). MBTX,, DBTX2, and TBTX were reported in the sediment of San Diego Bay, CA (IO),with TBTX being the dominant butyltin compound only in the vicinity of vessel repair/dry dock facilities, where the majority of TBTX is likely present in particulate, paint chip form. Areas where TBTX entered the sediment by sorption to particles from the dissolved state were dominated by increased levels of DBTX2and MBTX,. The half-life of TBTX in sediment has been reported as 5.5 months in marine sediments (10)
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and 4 months in freshwater sediments (12). Both studies suggested that microbial processes were responsible for the observed degradation. These studies examined the dieaway concentrations of TBTX from environmentally contaminated sediments which, in at least one case (IO), were collected in the vicinity of a yacht repair facility and most probably contained relatively inert TBTX-containing paint chips. In view of the results of the above studies, the focus of our work was to assess the possibility for abiotic degradation of TBTX at the sediment-water interface and rates of TBTX degradation when dissolved TBTX was exposed to sediment particles. This study documents the rapid degradation of TBTX in fine-grained sediments from the San Diego Bay (San Diego, CA), Pearl Harbor (HI), and Skidaway River (an estuarine river near Savannah, GA). Experimental Section Methodologies Using Hydride Derivatization Quantification. Sediment was collected from the top approximately 0.5 cm of the benthic layer in San Diego Bay, Skidaway River, and Pearl Harbor by carefully scraping the surficial sediment layer recovered with a van Veen sediment sampler. This was accomplished by carefully drawing a stainless steel spatula over the surface of the collected sediment. (The sediment from Commercial Basin in San Diego Bay was collected with a spatula at low tide directly from the exposed sediments.) All seawater used in the experiments was filtered through 0.4-pm polycarbonate filters and subsequently autoclaved in individual 500- or 1000-mL polycarbonate bottles to ensure degradation was not the result of metabolism by bacteria or algae from water, but due to added sediment. Once collected, sediment was divided into three treatment types: untreated, sterilized, and reduced organic carbon. The untreated sediment (1or 2 g) was added to the sterilized seawater after the water had cooled to room temperature. Added TBTX was subsequently introduced. For sterile sediment, either 1or 2 g of sediment was added to 200 mL of seawater and this sediment-water mixture was subsequently autoclaved. Reduced organic carbon sediment was heated in 2-g aliquots to 550 "C in a furnace for 2 h (16) to destroy the majority of organics, and the combusted sediment was then added to the seawater. This thermal combustion to produce reduced organic carbon content in the sediments resulted in the reduction of original organic carbon contents of 2-22% to less than 0.1% organic carbon. TBTX was added in all cases after sediment was added to the autoclaved and subsequently cooled seawater. Wet to dry weight ratios were determined so as to add equivalent mass of sediment to each incubation bottle. Ratios of 1.0-g sediments to 200 mL of seawater were used for the Skidaway River sediment and 2.0 g to 200 mL for San Diego Bay and Pearl Harbor sediments. Between 74 and 254 ng of tributyltin chloride was added to the sediment-water mixtures. The individual bottles were capped and suspended approximately 1m below the surface of Pearl Harbor (23-24 "C) for the Pearl Harbor sediment and 1 m below the surface of San Diego Bay (16-19 "C) for both San Diego and Skidaway River sediment. Individual bottles were removed at the specified time intervals (after addition of the TBTX) and analyzed immediately, as described below, or frozen and analyzed within 2 weeks. Controls consisting of autoclaved seawater and TBTX were prepared identically to experimental bottles and analyzed to document TBTX stability in the absence of sediment. Analytic Method: Hydride Derivitization. Quantification of unlabeled TBTX, DBTX,, MBTX,, and in
some cases inorganic tin was performed by hydride derivatization-atomic absorption detection. Sediment-water mixtures were filtered through 0.4-pm polycarbonate filters and the water (2) and sediment (IO), after air-drying and grinding with a mortar and pestle, analyzed separately. Both the sediment and water were normally analyzed in triplicate, except where low levels of remaining TBTX required total exhaustion of the sample for quantification. Mean recovery of butyltin compounds was 95% with a range between 67 and 122%. Radiolabeled Studies. For radiolabeled studies, [butyl-1J4C]tri-n-butyltin oxide custom synthesized by New England Nuclear (21 mCi/mM) was used. [14C]TBTXwas added to bottles containing 5.0 g of sediment and 50 mL of sterile seawater. The final TBTX concentration was 0.3 pg/g of sediment. At the end of the incubation period, 20 mL of 6 N HC1 was added and [14C]TBTX and its degradation products were extracted with methylene chloride (75 mL). Spiked recoveries of [14C]TBTX(0.05 pg/g of sediment) were between 92 and 96%. The methylene chloride extracts, after concentration to near dryness, were applied to silicic acid thin-layer plates. The solvent system was isopropyl ether-acetic acid (98/2 v/v). Autoradiography using X-ray film (X-Omat AR Film, Eastman Kodak Co.) of the thin-layer plates was carried out to locate the position of TBTX and its degradation products. Radiolabeled spots were scraped from the thin-layer plates, added to scintillation fluid, and radioactively determined with a scintillation counter (Tri-carb 300, Packard Instrument Co.). Authentic standards for thin-layer chromatography included tributyltin chloride, dibutyltin dichloride, and butyltin trichloride (Aldrich Chemical Co.), Unlabeled organotins were visualized on the thin-layer plates by spraying plates with dithiozone or pyrocatechol violet spray (17). Documentation of Sediment Sterility. Following the previously described sterilization procedures, the estuarine sediments from the Skidaway River were assayed for bacteria and ATP content to determine the effectiveness of the sterilization procedures. Bacterial counts were determined on sediment samples diluted in 0.22-pm filtered estuarine water and fixed with a glutaraldehyde solution (2%) buffered with 0.1 M cacodylate (pH 7.5). Samples were stained with 0.01 mM 4',6-diamidino-2phenylindole (DAPI) for 20 min and subsequently filtered through 0.22-pm Nucleopore filters (stained with 0.2 70 irgalan black). Bacterial cells retained on the filters were counted using an epifluorescent Zeiss microscope. Extraction of ATP from the sediment was accomplished by utilizing the method of Bulleid (18). The ATP concentrations were quantified using a Chem-Glow photometer (American Instrument Co.). The results of the bacterial counts indicate that sterility was effectively achieved. Prior to sterilization,the bacterial cell counts were 1.1X logcells/mL, and after sterilization, bacterial cells were not observed ( < l o cells/mL). The results of the ATP analysis also support attainment of sterile conditions. Prior to sterilization, the ATP concentration was 2.1 pg/mL, and after sterilization, ATP was not detected (
