Effects of pH on the speciation of several triorganotin compounds in Anacostia River sediments using Mossbauer spectroscopy

The effects of pH on the speciation of some tributyltin and triphenyltin compounds in spiked sediments from the Anacostia River were studied. The compounds included tributyltin chloride, oxide, and acetate as well as triphenyltin chloride, hydroxide, and acetate. Mossbauer spectroscopy was used to measure the speciation of the triorganotin compounds in the spiked sediments. In general, for the three pHs (5, 7, and 9) studied, the Mossbauer parameters, quadrupole splitting, and isomer shift, varied depending upon the sediment site and the pH. The rho-values (ratio of quadrupole splitting to isomer shift), which indicate the co-ordination of the tin atom, were greater than 2.1 in all cases, indicating that the co-ordination around the tin atoms in all the spiked sediments is greater than four. The variation in the Mossbauer parameters with pH at different sites in the Anacostia River reflects the variation in the components of the sediments.