Interactions of Tin(IV) and monomethyltin cation in estuarine water–sediment slurries from the great bay estuary,New Hampshire,USA

This study describes experiments on sedimentestuarine water slurries originating from a Spartina alterniflora salt marsh. We investigated the fate of tin(IV) or monomethyltin cation (MeSn³⁺) chlorides after their additon to slurries under anaerobic and aerobic conditions. We did not observe methylation of tin in anaerobic or aerobic slurries with and without added tin(IV). MeSn³⁺-amended samples occasionally formed small amounts of Me₂Sn²⁺ or Me₃Sn⁺ after extended periods of time, particularly when MeSn³⁺ remained in solution. The stability of MeSn³⁺ in slurries demonstrates that the absence of net methylation of tin(IV) is not due to rapid demethylation of MeSn³⁺ or its further methylation. Inorganic tin concentrations in the aqueous phase of anaerobic slurries spiked with MeSn³⁺ and unspiked slurries decreased by about 85% in 21 days and remained relatively constant until the end of the 59-day experiments. In similar anaerobic experiments about 25% of the MeSn³⁺ spike was adsorbed to sediment within 1 h and about 75% was adsorbed within 10 days. The lack of methylation and demethylation reactions in our aerobic and anaerobic slurries, which contrasts with two previous reports, undoubtedly reflects the absence of added nutrients and low concentrations of added tin(IV) in our experiments. We believe that our model experiments more accurately reflect conditions in salt marshes than do previous studies. We conclude that future model studies on methylation of inorganic tin should include. S. alterniflora because it is so prominent in observations of methyltin compounds in the estuary.