Fate of tributyltin in a created tidal wetland

The ability of Spartina alterniflora to degrade tributyltin (TBT) in contaminated dredge spoils was investigated in a created wetland at Little Creek Naval Amphibious Base in Norfolk, Virginia, USA. Concentrations of TBT up to 250 ng/g did not inhibit S. alterniflora growth over a 16-month period. Disappearance rates of TBT in vegetated and unvegetated treatments were similar, with half-lives of 300 to 330 d. Disappearance rates were not constant, but they were correlated to temperature changes and were possibly due to microbial degradation within the sediment. Of the initial amount of TBT in the sediment, only 0.4% accumulated in S. alterniflora biomass. Uptake of TBT by S. alterniflora was greatest in belowground biomass (43 ng/g). During plant senescence, most of the TBT was retained in the detrital material. Whereas S. alterniflora did not expedite the degradation of TBT, using TBT-contaminated dredge spoils to create wetlands is plausible. However, this should only be undertaken after further investigation into the potential for plant biomass to become a biovector for TBT.