In-situ partitioning of butyltin species in estuarine sediments

The in-situ solid/pore-water partitioning of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined for an estuarine sediment profile collected from a commercial marina. Total butyltin levels exceeded sediment quality guideline values, and were 220–8750 μg/kg for TBT, 150–5450 μg/kg for DBT and 130–4250 μg/kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 μg/l for TBT, 0.07–3.25 μg/l for DBT, and 0.05–0.53 μg/l for MBT. The partitioning of butyltin compounds between the sediment solid-phase and pore-water was described by an organic carbon normalised distribution ratio (D_OC). The observed D_OC values were similar for TBT, DBT and MBT, and were 10⁵–10⁶ l/kg. Values for the Butyltin Degradation Index (BDI) were larger than 1 at depths greater than 10 cm below the sediment/water-column interface. This indicates that substantial TBT degradation has occurred in the sediments, and suggests that natural attenuation may be a viable sediment remediation strategy.