Speciation of some triorganotin compounds in sediments from the Anacostia and Potomac Rivers, Washington, DC, using Mössbauer spectroscopy

Abstract

Triorganotin compounds, namely the tributyltin (TBT) and triphenyltin (TPT) moieties, have been used as the active components in antifoulant marine paints. Mo È ssbauer spectroscopy was used in this work to identify the products of speciation of these triorganotin compounds in various types of sediment from rivers around the Washington, DC, USA, area. Aerobic and anaerobic sediments from several sites in the Anacostia and Potomac Rivers were spiked with tributyl-and triphenyl-tin chloride, bis-(tri-n-butyltin) oxide and triphenyltin hydroxide. Mo È ssbauer spectra were recorded for the resultant interactions of the species produced with the various sediments. The Mo È ssbauer spectra of both types of sediment, aerobic and anaerobic, spiked with tributyltin chloride and bis-(tri-nbutyltin) oxide were the same, suggesting that these compounds were converted to the same species, mostly likely the hydrated tributyltin cation, TBT . The spectra of all triphenyltin chloride and triphenyltin hydroxide spiked sediment samples were the same, indicating again that these compounds were converted to the same species, in this case the hydrated triphenyltin cation, TPT . Thus the species that interacts with the various sediments are the respective hydrated cations. The results also support the previous conclusion obtained with Chesapeake Bay sediments, that the product of triorganotin speciation depends on the nature of sediment. Copyright # 2001 John Wiley & Sons, Ltd.KEYWORDS: triorganotin; antifoulant; speciation; sediments; Mo È ssbauerThe use of tributyltin (TBT) and triphenyltin (TPT) compounds in antifouling marine paints has generated great concerns and interest in their fate in the environment because they are known to have toxic effects on non-targeted marine organisms. 1±4 The use of triorganotin compounds in the USA has been restricted by the Organotin Act, 5 which prohibits the use of organotin-based paints on vessels smaller than 25 m. However, the hulls of older pleasure crafts may still contain these toxicants, which may leach into waterways and become potential environmental problems. Hence, it is important to study the fate and chemical speciation of these compounds in sediments when they enter the water system. In general, speciation of organotin compounds has been determined by extraction and/or derivatization procedures.6±8 However, tin Mo È ssbauer spectroscopy offers an advantage in that it permits the direct observation of the triorganotin species in the sediments. Mo È ssbauer spectroscopy yields information about the structure, bonding and oxidation states in organotin compounds by providing a probe of the tin atom. The two parameters obtained from the Mo È ssbauer spectrum are the isomer shift d and the quadrupole splitting D. The isomer shift is related to the s-electron density at the tin nucleus, which can provide information as to its oxidation states and the bonding of the tin atom. The quadrupole splitting reflects the electronic environment around the tin nucleus, and its magnitude gives info...

Use of Mössbauer spectroscopy to determine the effect of salinity on the speciation of triorganotins in Anacostia River sediments

“…Similar to the tributyltin case, the species would be the hydrated triphenyltin cation, and it is this species that would interact with the sediment. Similar results have been previously report [13]. The one inconsistent result in the present study is in the anaerobic sediments spiked with TPTOAc.…”

“…The spectral parameters of the spiked sediments are within experimental error of each other suggesting that in both types of sediments they are being converted to the same species, most likely the hydrated tributyltin cation. Similar results have been reported for the speciation of TBTs in Chesapeake Bay sediments [13]. In addition, the parameters at the different sites for the different salinities are similar suggesting that salinity did not play a major role in the speciation.…”

“…This would suggest that salinity did not play a major role in the speciation of the compounds. This result is similar to a study involving Chesapeake Bay sediments [13]. Rho values (Δ/δ)have been used to deduce the coordination number of tin atoms in various organotin compounds.…”

“…1 Mössbauer spectra of triphenyltin chloride (TPTCl) in anaerobic (top) and aerobic (bottom) spiked sediments from site 4 at salinity of 40%. effect of A more flexible n-butyl group would prevent the hydrated TBT + cation from having strong contacts with the sediments as have been previously reported [13].…”

“…An earlier study reported similar findings. [13] The hydrated species can then interact with the sediment according to the following equation: [13]. In general, the data for the TBT compounds indicated that anaerobic and aerobic spiked sediments from the different sites under the various salinity conditions gave similar Δ and δ values.…”