Sorption of tributyltin in seawater by municipal solid Sorption of tributyltin in seawater by municipal solid waste compost waste compost Ruth Vassallo and Alfred J. Vella* Department of Chemistry, University of Malta, Msida, Malta MSD06 Received 9 August 2000; Accepted 21 January 2001 TheuseofmunicipalsolidwasteMSW)compostasasorbentfortributyltinTBT)inseawaterwas investigated. TBT-contaminated seawater, both artificially prepared and that collected from Msida CreekyachtmarinaMalta),wasallowedtopercolatethroughuntreatedandwater-washedcolumns of compost and then analysed for organotins using gas chromatography-flame photometric detection. About 90% of dissolved TBT ranging in concentration from about 800 to 8000 ng Sn l 1 was sorbed by treating 500 ml solutions with 100 g untreated compost. On the other hand, no detectable breakthrough of TBT was observed from compost that had previously been washed by watertoremovesolubleorganicmatter.BreakthroughofTBTfromunwashedcompostisthoughtto beduetoformationofcomplexesbetweenthesolubleorganicmatterincompostandaquatedTBT, whichrenderstheorganotinmorehydrophilic.TheuseofwashedMSWcompostassorbentforthe purificationofTBT-contaminatedwatersgeneratedinlargequantityduringhull-cleaningactivities in drydocks is suggested as a mitigatory measure against the impact of TBT on the coastal marine environment. Copyright # 2001 John Wiley & Sons, Ltd. KEYWORDS: tributyltin; sorption; compost; seawater; environment The biocidal properties of tributyltin TBT) and its use in antifouling marine paints have led to the release of this substance in marine environments. TBT, which has been cited as the most toxic substance ever introduced deliber- atelyintothemarineenvironment, 1 isalsotoxictonon-target organisms. Imposex in marine gastropods and shell defor- mation in oysters are the best known effects resulting from TBT contamination, and laboratory experiments and field observations suggest that adverse biological effects occur at concentrations below those detectable, so that a no-observed effect level NOEL) has yet to be demonstrated. 2 A previously suggested 3 NOEL of 2 ng TBT l 1 0.8ng Sn l 1 ) is often exceeded in locations near ship-repairing and ship- building dockyards. The lipophilic character and poor water solubility of TBT are such that, when the substance is introduced into water, partitioning will occur, with the organotin preferentially adsorbing onto particles. Reports from different authors usingvariousconditionssuggestthatbetween10and95%of TBT introduced into water is removed by sorption onto particles and remains strongly adsorbed to the solid matrix. 4 Several studies have shown that tributyltin compounds sorb onto sediments. TBT concentrations in aquatic sediments have generally been found to be approximately 5  10 2 to 1  10 4 times the overlying water column values. 5 Unger et al. 6 reported sorption coefficients [TBT] sed /[TBT] water ) ran- ging between 10 3 and 10 4 lkg 1 for Chesapeake Bay; values for Toronto Harbour sediments 7 range between 3.5  10 3 and 6.4  10 4 l kg 1 and for Detroit River sediments 8 between 3.3  10 2 and 1.9  10 4 l kg 1 . TBT also binds onto soilsofvarioustypes.FentandMullerfoundthatorganotins in municipal sewage were primarily associated with suspended solids and that these compounds transferred from sewage water to sludge in the process of sewage treatment. 9 In this paper, we present results on a study of the sorption ofTBTinseawaterbymunicipalsolidwasteMSW)compost. The hypothesis that we set out to test was whether MSW compost could provide an effective method for purifying TBT-contaminated waters as generated in large quantities in activities related to ship-repair and maintenance as practiced in drydocks in Malta). The marine environment in coastal zones proximate to drydocking facilities is known locally, as elsewhere, to be a `hot spot' of TBT pollution 10 and a *Correspondence to: A. J. Vella, Department of Chemistry, University of Malta, Msida, Malta MSD06. E-mail: avel3@um.edu.mt DOI:10.1002/aoc.254 Copyright # 2001 John Wiley & Sons, Ltd. APPLIED ORGANOMETALLIC CHEMISTRY Appl. Organometal. Chem. 2002; 16: 21±26