SOURCES AND RATE OF DEGRADATION OF TRI(N-BUTYL)TIN IN MARINE-SEDIMENTS NEAR AUCKLAND, NEW-ZEALAND

The distribution of tri(n-butyl)tin (TBT) was determined in marine sediments near Auckland, New Zealand. The highest TBT concentrations were measured in sediments near a naval dry dock and close to boat washdown facilities. In Waitemata Harbour, yachts and commercial ships both act as a significant source of TBT. Considering the TBT concentrations in sediment cores from two marinas, subsurface maxima suggest that the recently introduced restrictions on the use of organotin antifouling paints has decreased the flux of TBT to the marine environment. Nonetheless, TBT was detected in sediments deposited over 15 years ago. Applying a simple model to interpret the TBT profiles indicates that degradation occurs with first-order kinetics and that TBT in marina sediments has a half-life of about 2.5 years.