ORGANOTIN DISTRIBUTION IN SEDIMENTS AND WATERS OF SELECTED EAST-COAST ESTUARIES IN THE UK

An extensive spatial survey of butyl- and methyltin compounds in the sediments and water column of seven Suffolk and Essex estuaries was undertaken between June and August 1990 to determine the main areas of organotin contamination. A number of these estuaries contain important shellfisheries and all have a high degree of boating activity. Speciation of organotins was performed by a purge and trap/boiling point separation method and detected by Atomic Absorption Spectrometry. Despite the implementation of the 1987 UK retail ban on tributyltin (TBT) based antifouling paints on vessels <25 m in length, 7 of the 17 sites sampled exhibited TBT water concentrations above the Environmental Quality Target (EQT) set in 1987. Water column concentrations ranged from <3-71.2 ng l-1. Dredging had occurred at some of these sites indicating that desorption of TBT from the sediment may occur following sediment disturbance. Surficial sediment organotin concentrations displayed high spatial variability with TBT levels ranging from <3-3935 ng g-1. The highest organotin concentrations occurred at sites with high levels of boating activity.