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

Abstract

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. Mo¨ssbauer 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 Mo¨ssbauer parameters, quadrupole splitting, and isomer shift, varied depending upon the sediment site and the pH. The r-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 Mo¨ssbauer parameters with pH at different sites in the Anacostia River reflects the variation in the components of the sediments.

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

“…The color of the sediments changed from black/greenish to black to brown. The locations of the various sites have been previously reported [12]. Salinity of the anaerobic or aerobic sediments was adjusted with artificial seawater so that the resulting salinities of the samples were 20, 40, and 60% of that of synthetic seawater, which was taken as 100%.…”