4.4 BEHAVIOR AND FATE OF ORGANOTTN COMPOUNDS IN THE MARINE ENVIRONMENT 



Tributyltin and the other butyltin moieties are poorly soluble in water 

 and are strongly lipophilic. In the marine environment TBT will 

 preferentially dissolve in polar molecular films in the surface 

 microlayer. Concentrations have been reported in the surface microlayer 

 several orders of magnitude above ambient water column values (Brinckman 

 et al., 1986; Cleary et al., 1987). TBT also adsorbs to particulate 

 matter suspended in the water column. The partitioning of organotins 

 between the water fraction and the particulate fraction is currently under 

 investigation. The tendency to adsorb on particulates is influenced by 

 the composition of the particles, whether alive or dead and by the nature 

 of the charge interactions with certain clay materials (Valkirs, et al., 

 1987; Unger et al., 1987). In laboratory studies with high quantities of 

 sediments, once the particulate material settles out, TBT concentrations 

 in the water column were lower, and bottom sediment TBT concentrations 

 increased which subsequently may become available to the benthic fauna. 

 Although this area has been little studied to date, Maguire and Tkacz 

 (1985) have demonstrated that benthic oligochaetes can take up and 

 metabolize TBT associated with sediment. The body burden of these worms 

 is thus potentially available to bottom feeding fish. 



4.4.1 Surface Microlayer 



The sea surface microlayer is a naturally occurring surface film in 

 relatively calm water, about 30 Ang st roms thick, is polar in nature and 

 readily accumulates lipophilic compounds. Organotins are strongly 

 lipophilic and have a high octanol to water partition coefficient and will 

 readily bind to the lipid monolayer at the air-water interface. Cleary 

 and Stabbing (1987) have characterized tributyltin concentrations in the 

 water column and the surface microlayer. They found organotin levels in 

 the surface microlayer up to 27 times greater than in the subsurface water 

 samples. Maguire et al. (1982) found concentrations in the surface 

 microlayer of 2 times subsurface water. They found high organotin 

 concentrations in the surface microlayer both in the summer of 1986 and 

 the spring of 1987 in both estuarine and freshwater environments. 

 Table 4.15 summarizes surface microlayer concentrations found in Canada, 

 the U.S. and England. These microlayer concentrations are not directly 

 comparable, because each study was conducted with a different sampling 

 instrument. An indication of the degree of variability introduced by the 

 different sampling methods can be seen in the measurements taken in the 

 same waters at the same time with the Garrett screen and the glass plate 

 samplers. The forces adhering the surface film to the sampler surface are 

 different in the two cases. Also the thickness of the surface film 

 removed are different between the two samplers. The glass plate sampler 

 removes a layer 60 to 110 microns thick while the screen removes a 280 to 

 300 micron thick layer. 



iv-3; 



