Tri-n-butyltin (TBT) compounds are synthetic, multipurpose chemicals, which have been extensively used, in marine antifouling paints. They have been known to be extremely poisonous to mollusc fishery resources (oysters, clams, scallops, etc.). TBT levels in marine sediments from the main ports in Fiji were analysed using the GC/FPD method. The results indicated that these sites were among the worst polluted with TBT in the world. The most contaminated site recorded a TBT concentration of 360μgg-1. TBT comprised 48-90% of the total organotins measured. Some stringent legislative means are needed to regulate the use of this contaminant in marine anti-fouling paints

Koshy, Kanayathu

Maata, Matakite

University of the South Pacific Electronic Research Repository

1A study on tributyltin contamination of marine sediments in the majorports of FijiMatakite Maata and Kanayathu KoshyDepartment of Chemistry, School of Pure and Applied Sciences, The University of the South Pacific, Suva, FijiABSTRACTTri-n-butyltin (TBT) compounds are synthetic, multipurpose chemicals, which have been extensively used, in marine anti-fouling paints. They have been known to be extremely poisonous to mollusc fishery resources (oysters, clams, scallops,etc.). TBT levels in marine sediments from the main ports in Fiji were analysed using the GC/FPD method. The resultsindicated that these sites were among the worst polluted with TBT in the world. The most contaminated site recorded aTBT concentration of 360µgg-1. TBT comprised 48-90% of the total organotins measured. Some stringent legislativemeans are needed to regulate the use of this contaminant in marine anti-fouling paints.Keywords: TBT, biocide, anti-fouling, sediments, Fiji1 IntroductionTBT compounds are active biocides in anti-fouling paintsused on ship hulls (Evans et al., 1996; Stab et al., 1996).The wide applications of TBT began in the early 1960swhen it was found that they inhibited the growth andattachment of fouling organisms such as algae, barnacles,tubeworms (Huet et al., 1996), mussels (Huggett et al.,1992) and wood worm borers (Greenwood and Earnshaw,1993) on ship and boat hulls. It is through this use that themarine TBT finally finds its way into sediments where iteventually decomposes into the less toxic dibutyltin (DBT)and monobutyltin (MBT). This study considers theseorganotin (OT) species in a tropical Pacific environmenttaking Fiji as an example. In the present paper, an attempthas been made to summarise our studies on thequantification and degradation kinetics of TBT into itsequilibrium component forms.2 Study SitesThe sites studied included a slipway in Walu Bay, Suva, ajetty in Lautoka and jetties also in Savusavu and Labasa.These sites are shown in Figure 1.Figure 1. Fiji Islands showing the study sites.Vanua LevuViti LevuThe Fiji Islands0 50Km180  o18  SoLabasaSavusavuSuvaLautoka23 Materials and MethodsSediment samples were collected with a ponar grabsampler (or by hand when possible), and were storedfrozen in polyethylene bags. These were then subsequentlyfreeze-dried and stored till analysis.In preparation for the organotin analysis, a slightlymodified version of an extraction procedure by Krone wasused. This involved extracting the TBT in sediments withmethylene chloride, derivatizing it with Grignard reagent,pentyl magnesium bromide to generate the volatile tetra-alkylated organotins and detecting the tin using GasChromatography with a flame photometric detector(GC/FPD) (Krone, 1995). The analysis with the GC/FPDwas carried out at the Institute of Ocean Sciences, Sidney,B. C., in Canada.4 Results and DiscussionThe data from the analysis of the samples from Suva(Walu Bay), Lautoka, Savusavu and Labasa are presentedin Tables 1, 2 and 3. These include organotinconcentrations and the ratios for [MBT]/Total [OT] and[TBT]/[DBT].Table 1  Results of the field samples from Walu Bay showing the OT concentrations and the ratios of MBT withTotal OT and TBT with DBT.Sample No. Date TBT(µg/g)DBT(µg/g)MBT(µg/g)Total OT(µg/g)MBT/OTratioTBT/DBTratio10 24/4/95 116 40.4 48.4 205 0.236 2.8728 25/5/95 132 45.4 97.7 275 0.355 2.9137 29/6/95 72.2 19.5 7.97 100 0.079 3.742 12/7/95 360 91.1 45.2 496 0.091 3.9563 24/8/95 196 86.7 90.2 373 0.242 2.2677 1/10/95 106 17.3 45.9 169 0.271 6.1388 2/12/95 223 175 66.5 465 0.143 1.2792 2/2/96 91.9 26.0 15.5 133 0.116 3.53Table 2 Results of the field samples from Lautoka wharf (LW) showing the ratios of MBT with Total OT andTBT with DBT.Sample No.Date [TBT](µg/g)[DBT](µg/g)[MBT](µg/g)Total [OT](µg/g)[MBT]/Tot [OT] [TBT]/[DBT]9   (LW1) 20/4/95 25.0 1.35 14.2 40.55 0.35 18.529 (LW1) 25/5/95 52.8 3.83 16.5 73.13 0.226 13.830 (LW2) 25/5/95 45.5 5.00 18.7 69.2 0.27 9.160 (LW1) 12/8/95 43.4 2.03 8.76 54.19 0.162 21.461 (LW2) 12/8/95 20.4 1.97 3.45 25.82 0.134 10.480 (LW1) 28/10/95 37.4 4.13 12.9 54.43 0.237 9.181 (LW2) 28/10/95 41.6 8.52 21.0 71.12 0.295 4.990 (LW1) 1/2/96 15.0 1.88 2.17 19.05 0.114 8.091 (LW2) 1/2/96 29.3 3.46 8.12 40.88 0.197 8.5Table 3 Results of field samples from Savusavu (SVSV) and Labasa (LBS).Sample No. Site [TBT](µg/g)[DBT](µg/g)[MBT](µg/g)Total [OT](µg/g)[MBT]/Tot[OT][TBT]/[DBT]32 SVSV1 39.6 1.22 4.02 44.8 0.089 32.533 SVSV2 15.8 0.669 2.01 18.5 0.109 22.634 SVSV3 21.1 0.205 6.55 27.9 0.235 10335 LBS1 34.9 2.54 5.17 42.6 0.121 13.736 LBS2 89.0 4.16 5.47 98.6 0.056 21.4The TBT concentrations were highest in the Walu Baysediments (Figure 1), when compared with the other ports(Tables 1, 2 & 3). This can be attributed to the slipwaysource at this site. Out of the three organotin species, TBTis dominant in all the samples analysed. Table 4 presentssome of the international TBT data compared with the datafrom this site. It is evident that the Fiji sediments from thetwo studies presented in the table are heavily loaded withthis contaminant. TBT concentration as low as 0.659ngTBT g-1 has been reported to be toxic to molluscs(O’Connor, 1996).3Table 4  TBT concentrations from various studiesSite Depth (cm) Concentration (ng Sn g-1dry weight)ReferenceSuva Harbour, Fiji Surface <5-38 000 Stewart & de Mora, 1992Suva Harbour, Fiji Surface 72 200-360 000 sThis studyArcachon Bay, France 0-50 cm <5-5 000 Astruc et al., 1990Kaipara Harbour, NZ 0-40 cm <4-759 de Mora, King & Miller, 1989San Diego Harbour, USA 0-20 cm 8-66 SStang & Seligman, 1986San Diego Harbour, USA Surface 143 SStang, Lee & Seligman, 1992North Chesapeake Bay, USA Surface 58-570 Matthias et al., 1988Poole Harbour, UK Surface 8-213 Langston et al., 1987Sado Estuary, Portugal Surface 6-213 Quevauviller et al., 1988Sydney Harbour, Australia Surface 10-8 000 Batley & Brockbank, unpublished resultsGeorges River, Sydney, Australia 0-40 cm <0.2-20 Kilby & Batley, 1993Great Bay Estuary, New Hampshire, USA Surface 4-20 Weber et al., 1988TBT degrades to other lesser toxic organotin compounds,DBT and MBT in seawater and sediments. The half-life ofTBT in sediments varies from 16 weeks to 3.5 years withthe latter now believed to be representative (Ko et al.,1995). At the Walu Bay site, the supply of TBT into theenvironment can be considered to be excessive overremoval by degradation.The ratio, [MBT]/total [butyltins] is used to determinewhether the discharge is recent. Low ratios (0.03-0.1)indicate recent discharge of TBT. Ratios as low as 0.03,show TBT “hot spots”. In Hong Kong, measured ratioscorrelated with the recent release of TBT into thesediments in marinas and shipyards, which were heavily,contaminated (Ko et al., 1995). No “hot-spots” wereidentified from these sites although there were twosamples from Walu Bay that had values <0.1 (Table 1).The remaining ports had ratio values >0.1.  This is nosurprise as there is a known source of TBT at this port(Stewart and de Mora, 1992).The ratio, [TBT]/[DBT], has also been used previouslyas a first estimate of the stability of the organotin (Tolosaet al., 1992). This is because the organotin compounddegradation occurs via a successive cleavage of the alkylor aryl substituents (Maguire et al., 1986). In sediments,the higher ratios were found in enclosed systems, whichhad slower anaerobic degradation processes prevailing.The trend in the ratio is a relative decrease from organismsto sediments to seawater and this is thought to be due to alower stability of TBT in water and/or a higher affinity forbiota and sediments (Tolosa et al., 1992). It is obviousfrom the data available (Tables 1-3) that the sites had highvalues of this ratio, implying stability of TBT. This,however, may not necessarily be the case as the high TBTinput could also be responsible for the high ratio value.This again could be attributed to the unrestricted usage ofTBT in marine paints in this country.5 ConclusionsThe sediments of the major ports in Fiji contain very highconcentrations of TBT. The high input of TBT into theenvironment and particularly sediment overrides anyremoval by the degradation pathway.  Stringent legislativemeasures are needed to curb the uncontrolled usage of thiscontaminant in marine paints. The people who areconsumers of the marine resources, which are beingthreatened, need awareness and education programmes onthe impact of TBT on the environment. It is these peoplewho can pressure the authorities for tougher legislation onTBT use.6 ReferencesAstruc, A., Lavigne, R., Desauziers, V., Pinel, R. & Astruc, M. (1990) Tributyltin determination in marinesediments: a comparative study of methods. Appl.Organomet. Chem. 3, 267-271.Batley, G. and Brockband, C. I., (1996), Unpublished results. In Trbutyltin: case study of an environmentalcontaminant, de Mora, S. J., (ed), CambridgeUniversity Press,  pp 139-166.de Mora, S. J., King, N. G. and Miller, M. C. (1989) Tributyltin and total tin in marine sediments: profilesand the apparent rate of TBT degradation. Environ.Technol. Lett. 10, 901-908.Evans, S. M., Evans, P. M. and Leksono, T. (1996) Widespread recovery of Dogwhelks, Nucella lapillus(L.), from Tributyltin Contamination in the North Seaand Clyde Sea. Mar. Poll. Bull. 32 (3), 263-269.Greenwood, N. N. and Earnshaw, A. (1993) Organometallic compounds (Chapter 10). Chemistry ofthe elements, Pergamon Press, Oxford.Huet, M., Paulet, Y. M. and Glemarec, M. (1996) Tributyltin pollution in the coastal waters of WestBrittany as indicated by imposex in Nucella lapillus.Mar. Environ. Res. 41 (2), 157-167.Huggett, R. J., Unger, M. A., Seligman, P. F. and Valkirs, A. O. (1992) The marine biocide tributyltin. Environ.Sci. & Technol. (26), 233-410.Kilby, G. W. and Batley, G. E., (1993). Chemical indicators of sediment chronology. Aust. J. Mar.Freshwater Res., 44, 635-47.Ko, M. M. C., Bradley, G. C., Neller, A. H. and Broom, M. J. (1995) Tributyltin contamination of marinesediments of Hong Kong. Mar. Poll. Bull. 31 (4-12),249-253.Krone, F. (1995) Butyltin sediment extraction procedure. Unpublished report.Langston, W. J., Burt, G. R. and Zhou Mingjiang (1987). 4Tin and organotin in water, sediments and benthicoganisms of Poole Harbour. Mar. Poll. Bull., 18, 634-9.Maguire, R. J., Tkacz, R. J., Chau, Y. K., Bengert, G. A. & Wong, P. T. S. (1986) Occurrence of organotincompounds in water and sediment in Canada.Chemosphere 15 (3) 253-274.Matthias, C. L., Bushong, S. J., Hall, L. W., Bellama, J. M. and Brinckman, F. E., (1988). Simultaneous butyltindeterminations in the microlayer, water column andsediment of a northern Chesapeake Bay marina andreceiving systems. App. Organometall. Chem., 2, 547-52.O'Connor, P. T. (1996). Trends in Chemical Concentrations in Mussels and Oysters CollectedAlong the US Coast from 1986 to 1993. Mar. Environ.Res. 41 (2), 183-200.Quevauviller, P., Lavigne, R., Pinel, R. and Astruc, M., (1988). Organotin compounds in intertidal sediments ofthe Sado Estuary and mussels from the adjacent coastalarea, Portugal. In Heavy Metals in the HydrologicalCycle, M. Astruc and J. N. Lester (eds), Selper,London, pp.425-432.Stab, J. A., Frenay, M., Freriks, I, L., Brinkman, U. A. T. and Kofino, W. P. (1996) Survey of nine organotincompounds in the Netherlands using the zebra mussel(Dreissena polymorphia) as biomonitor. Environ.Toxicol. Chem. 14(12), 2023-2032.Stang, P. M. and Seligman, P. F. (1986) Distribution and fate of tributyltin in the sediment of San Diego Bay. In:Proceedings of the Organotin Symposium, Oceans ‘86Conference, Washington, DC, USA, 23-25 September,1986, New York, the Institute of Electrical andElectronics Engineers, Inc., Vol. 4. pp1256-1261.Stang, P. M., Lee, R. F. and Seligman, P. (1992) Evidence for rapid, nonbiological degradation of tributyltincompounds in autoclaved and heat-treated fine-grainedsediments. Environ. Sci. & Technol. 26, 1382-1387.Stewart, C. and de Mora, S. J. (1992) Elevated tri (n-butyl) tin concentrations in shellfish and sediments from SuvaHarbour, Fiji. Appl. Organomet. Chem. 6 507-512.Tolosa, I., Merlini, L., de Bertrand, N., Bayona, J. M. and Albaiges, J. (1992) Occurrence and fate of tributyl- andtriphenyltin compounds in Western Mediterraneancoastal enclosures. Environ. Toxicol. & Chem. 11, 145-155.Weber, J. H., Han, J. S. and Francois, R., (1988). Speciation of methyl- and butyltin compounds incompartments of the Great Bay Estuary. In HeavyMetals in the Hydrological Cycle, M. Astruc and J. N.Lester (eds), Selper, London, pp.395-400.5

A study on tributyl tin (TBT) contamination of marine sediments in the major ports of Fiji

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A study on tributyl tin (TBT) contamination of marine sediments in the major ports of Fiji

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