Occurrence of organotin compounds in water, sediments and mollusca in estuarine systems in the southwest of Spain

Six organotin species - tributyltin (TBT), dibutyltin (DBT), monobutyltin ( MBT), triphenyltin (TPT), diphenyltin (DPT) and monophenyltin (MPT) - have been determined in seawater (255 samples), sediments (85 samples) and bival ves (558 samples) collected at seventeen locations in the southwest of Spai n in five occasions between May 1992 and August 1994. No phenyltin species were found but butyltin species were present in all the stations. The TBT c oncentrations ranged between 23 and 1500 ng g(-1) Sn in biota, from less th an 0.6 to 160 ng g(-1) Sn in sediments and from less than 0.5 to 31 ng L-1 Sn in water, with the highest values closely related with boating activity and decreasing according to the distance from the potential sources. For bi ota and water, a consistent seasonal pattern of fluctuation of TBT concentr ations was evident, with the highest values found in spring and summer exce pt for a fishing harbour. A slow decrease of TBT concentration was observed between 1992 and 1994. Percentages of DBT and MBT in biota (22 +/-7 and 13 +/-6, respectively) were lower than those in water (33 +/- 10 and 31 +/- 1 5, respectively) and sediments (48 +/- 16 and 25 +/- 16, respectively). Sed iment-water partition coefficients for TBT were 240-65 000 and bioconcentra tion factors 17 000-350 000. This article discusses the significance of the pollution in our study area in comparison with other world coastal areas.