Organotin pollution in Malta coastal zone

Self Cite

The presence of compounds of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined in outdoor settled dust collected from several sites on the island of Malta, mainly from flat rooftops of school buildings. The dust was separated into three size fractions with diameters (µm) >250, 125-250 and <125, and the two finer fractions were analysed for butyltins using extraction with glacial acetic acid followed by derivatization/solvent extraction with sodium tetraethylborate in the presence of iso-octane and quantitation by gas chromatography with flame photometric detection. The presence of TBT, DBT and MBT was established in most of the samples and TBT concentrations varied from non-detectable (<5 ng Sn g −1 ) to highs of 15.5 and 18.7 µg Sn g −1 in Senglea and Marsaxlokk. TBT was generally found at concentrations significantly higher than reported hitherto in house dust collected from European homes. The geographical distribution of total organotins in both dust fractions suggests that TBT originates mainly from antifouling marine paint residues which contaminate the urban environment when ships' hulls are sand-or hydro-blasted during maintenance and repair at the drydocks facility in Grand Harbour. Other significant sources of TBT are located at Marsaxlokk fishing port and Wied iż-Żurrieq creek, both hosting sizeable communities of fishermen and leisure boating. The data also suggest that the municipal solid waste landfill at Maghtab is an inland source of butyltins. We suggest that dust containing harmful butyltins could possibly be ingested to expose humans to a risk which is probably of concern especially for young children living close to the hotspots of contamination.

“…The territory comprising the island of Malta was divided into grids of approximate size 7.8 km 2 and at least one sample was taken from each grid area (Fig. 1) …”

Section: Sampling Of Dustmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Contamination of outdoor settled dust by butyltins in Malta

Decelis

Vella

2007

Self Cite

“…[2][3][4] It appears likely that these compounds might be more ubiquitous than is presently apparent, and they could have remained In vitro methylation of tributyltin 905 unidentified due to the fact that attention may have been reserved solely for specifically targeted organotin forms. It is not uncommon to see reports in the literature where FPD-generated gas chromatograms are presented that contain more peaks than are identified and discussed by the authors, and methylbutyltins could well be among such unidentified peaks.…”

Section: Discussionmentioning

confidence: 94%

“…This is the site of one of the major yacht marinas on this central Mediterranean island; the creek also receives considerable runoff from one of the valley systems in Malta. This site was chosen as it provides an organic-matter-rich calcitic sediment that is known to be moderately contaminated with organotins; TBT and methylbutyltins had been identified in various sediments from this marina 2 and, therefore, biota resistant to TBT and possibly capable of transforming organotins biochemically to methylated forms were considered to be present in the sediment. Around 10 l 3 of seawater was collected from a depth of 1 m, and around 2 kg of a greyishblack sediment were removed from the sea bed at 2.5 m water depth using a grab sampler.…”

Section: Methodsmentioning

confidence: 99%

“…1 We have previously reported the occurrence in the marine environment of tetrasubstituted organotins of the type Me n Bu (4Àn) Sn (Me = methyl; Bu = butyl), where n = 1-3. 2 Previously, these compounds were only reported in lacustrine environments, and then very infrequently. 3,4 In the Malta coastal zone, these compounds were found occasionally in the water column and frequently in sediments, where, for example, the concentration of Me 3 BuSn was found at a maximum value of 9 mg Sn g…”

Section: Introductionmentioning

confidence: 98%

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Preliminary evidence for in vitro methylation of tributyltin in a marine sediment

Vella

Adami

2001

Self Cite

Recent reports from our laboratory on the occurrence of methylbutyltins in marine sediments and seawater suggest that these compounds are formed in the environment by the methylation of both tributyltin (TBT) and that of its degradation products, i.e. dibutyltin and monobutyltin, to give Me n Bu (4Àn) Sn for which n = 1, 2 and 3 respectively. We investigated the possibility of inducing methylation of TBT in seawater-sediment mixtures in experiments carried out in vitro using environmental materials collected from a yacht marina in Msida, Malta. Three water-sediment mixtures, which were shown to contain TBT, dibutyltin and monobutyltin but no other organotins, were spiked with tributyltin chloride (90 mg in 100 ml sea-water/100 ml sediment); to one mixture was added sodium acetate and to another methanol, to act as possible additional carbon sources, and all mixtures were allowed to stand at 25°C in stoppered clear-glass bottles in diffused light for a maximum of 315 days. Speciation and quantification of organotins was performed using aqueous phase boroethylation with simultaneous solvent extraction followed by gas chromatography with flame photometric detection. The atmosphere inside the bottles quickly became reducing with abundant presence of H 2 S, and after an induction period of about 112 days, and only in the reaction mixture containing methanol, methyltributyltin (MeBu 3 Sn) was observed in both sediment (maximum concentration 0.87 mg Sn g À1 ) and overlying water (maximum concentration 6.0 mg Sn l À1 ). The minimum conversion yield of TBT into MeBu 3 Sn was estimated to be 0.3%. MeBu 3 Sn has a significantly lower affinity for sediment than TBT and, therefore, is more mobile in the marine environment, possibly also migrating into the atmosphere to generate a hitherto unsuspected flux of organotin into that phase.

Sorption of tributyltin in seawater by municipal solid waste compost

Vassallo¹,

Vella²

2001

Self Cite

The use of municipal solid waste (MSW) compost as a sorbent for tributyltin (TBT) in seawater was investigated. TBT-contaminated seawater, both artificially prepared and that collected from Msida Creek yacht marina (Malta), was allowed to percolate through untreated and water-washed columns 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 À1 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 water to remove soluble organic matter. Breakthrough of TBT from unwashed compost is thought to be due to formation of complexes between the soluble organic matter in compost and aquated TBT, which renders the organotin more hydrophilic. The use of washed MSW compost as sorbent for the purification of TBT-contaminated waters generated in large quantity during hull-cleaning activities in drydocks is suggested as a mitigatory measure against the impact of TBT on the coastal marine environment.