Changes in Concentrations of Organotins in Water and Sediment in England and Wales Following Legislation

Abstract

This chapter reports the results of monitoring environmental concns. of tributyltin (TBT) in the UK from 1986 to 1988. The UK government implemented legislation in 1986, that limited the amt. of Sn in copolymer and free-assocn. tributyltin-based antifouling paints. This was followed in 1987 by a ban on the use of TBT-based paints on boats under 25 m in length and on mariculture equipment. Concns. of TBT have been monitored in seawater and sediments from estuaries that have traditionally supported shellfisheries and are popular centers of boating activity. By 1988, concns. of TBT in water samples taken close to sites of oyster and mussel cultivation were approx. half of the concns. recorded in 1986. However, at all of these sites in 1988 the concns. of TBT in the water exceeded 2 ng/L, which is the environmental quality std. (EQS) set by the UK for the protection of marine life. The concns. in many areas were above the toxocol. threshold values of a variety of species. Water samples from marinas have also been analyzed, and in some cases concns. of TBT in excess of 1000 ng/L have been recorded; however, by 1988, concns. of TBT in the water of several marinas had decreased to approx. a quarter of the values recorded in 1986. The concns. of TBT in sediments were highest in samples taken close to sites of oyster and mussel cultivation were approx. half of the concns. recorded in 1986. However, at all of these sites in 1988 the concns. of TBT in the water exceeded 2 ng/L, which is the environmental quality std. (EQS) set by the UK for the protection of marine life. The concns. in many areas were above the toxicol. threshold values of a variety of species. The concns. of TBT in sediments were highest in samples taken close to high-d. boat moorings or in marinas. Such samples contained concns. of TBT >1 .mu.g/g (dry wt.). Water samples have also been taken from com. harbors, major waterways, and close to anchorages. It is difficult to assess the contribution of shipping to the inputs of TBT to the environment, when ships share the same body of water with small boats and yachts. However, the hosing-down of ships in drydock has been identified as a major source of input of TBT to the aquatic environment. Concns. of TBT in major rivers, lakes, and the Norfolk Broads have been recorded. Levels of TBT in excess of 1000 ng/L have been measured in samples from some freshwater marinas and boatyards. The spillage of timber-treatment chems., contg. TBT, from riverside storage facilities, has sometimes been the cause of major inputs of TBT to the freshwater environment. The distribution of organotin (tributyltin and dibutyltin) throughout the water column has been investigated. Maximum concns. occur in the surface microlayer and min. values near the bottom. Concns. in samples from the surface microlayer, taken with a Garrett screen sampler, were as much as 27 times greater than those in subsurface waters. It is probable that such high concns. in the surface microlayer may have deleterious effects on both the neuston and on organisms of the littoral zone.