Investigation of tributyltin: Water/sediment interactions

• Main Author: Unger, Michael A.
• Format: Others
• Language: English
• Published: W&M ScholarWorks 1988
• Subjects: Environmental Sciences
• Online Access: https://scholarworks.wm.edu/etd/1539616885; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=2452&context=etd

Tributyltin (TBT) and its degradation products dibutyltin (DBT) and monobutyltin (MBT) have been quantitatively analyzed in environmental water samples using gas chromatography with flame photometric detection and gas chromatography/mass spectrometry (GC/MS). The butyltins were extracted from environmental samples with hexane/0.2% tropolone and derivatized with hexyl magnesium bromide to form hexylbutyltins. Full scanning GC/MS was used for confirmation of peak identifications and quantification was done by selective ion monitoring (methane chemical ionization) at m/z 319 (TBT) and m/z 347 (DBT, MBT and tripentyltin, the internal standard). Calibration curves were linear and detection limits were less than 2 ngL&\sp{lcub}-1{rcub}&. GC/MS and GC with flame photometric detection were compared as quantification methods and were shown to give similar results at the low ngL&\sp{lcub}-1{rcub}& levels. Water samples from Southern Chesapeake Bay were analyzed for TBT in areas of high boating activity. Several sites around a marina were sampled at repeated intervals. High spatial and temporal variability was noted. Reproducible concentration gradients were apparent, with the highest TBT levels near marinas and boatyards. Equilibrium sorption of TBT was measured on selected estuarine and freshwater sediments. Isotherms from twenty-four hour sorption and desorption equilibrations were linear with sorption coefficients between 1.1 &\times& 10&\sp2& and 8.2 &\times& 10&\sp3& Lkg&\sp{lcub}-1{rcub}&. Sorption coefficients decreased with increasing salinity and varied by a factor of two over the salinity range 0-34&\perthous&. Desorption kinetics were measured and indicated an initial fast rate followed by a slower rate. Water and sediment concentrations for TBT at locations in the Chesapeake Bay system were used to calculate apparent sorption coefficients that generally agreed with laboratory measured sorption coefficients. Exceptionally high apparent sorption coefficients were found near areas of high vessel activity and may be the result of TBT paint chips in the sediment.