Tributyltin compounds are hydrophobic, only slightly soluble in seawater, 

 and partition readily on to solid surfaces. In Schatzberg's study, three 

 soil types were examined for their affinity for tributyltin occpounds to 

 determine leaching and soil disposal effectiveness. Table 4.6 presents 

 results obtained with soil lysimeters and organotin-contaminated abrasive 

 grit from Navy shipyards (Schatzberg, 1986) . The study found that 

 tributyltin compounds were strongly adsorbed by the three selected soil 

 types. Similarly, s tr ong adsorption of tributyltin compounds to 

 particulate matter, suspended and bottom sediments has been found (see 

 Valkirs et al., 1986; Stang, 1987). 



4.2.3 Estimates of Potential loadings of Tributyltin Released by Vessels 

 to Lower Chesapeake Bay 



One of the aspects of concern in the consideration of TBT released from 

 vessels is the relative contribution of different vessel types, because 

 they have different residence times in a specified location as well as 

 different paint formulations (use) patterns. The following assumptions of 

 vessel type (and use) versus expected preference of release rates paints 

 were made by the Navy to estimate the guantities of TBT that would be 

 released to the State of Virginia's coastal waters from all types of 

 vessels (should the Navy implement fleetwide use of TBT antifouling 

 paints) : 



o Commercial and fishing vessels would be painted with copolymer 

 paints having a low release rate (due to desire of limited time 

 for dry-dock maintenance) . 



o Recreational craft would be painted with high release rate free 

 association paints (due to paint costs) . 



o Navy vessels would be painted with lowest release rate paints 

 available, and that Navy ships would be painted on a 10 year 

 implementation schedule. 



Table 4.7 presents the Navy's estimates of the potential total loading of 

 TBT in the Lower Chesapeake Bay, that would be released by all vessels, 

 given full fleetwide implementation of low release rate copolymer paints 

 over the next ten years (NAVSEA, 1986) . The greatest uncertainty in the 

 generation of these estimates is the proportion of recreational boat 

 owners who are in fact using free association paints containing 

 tributyltin as the principal antifoulant. The Navy has estimated that 

 recreational vessels would add 66%, while Navy vessels in lower Chesapeake 

 Bay would only add 4%. The Navy has made a similar estimate for the 

 entire U.S. and determined that their contribution would be 2.5% of the 

 total loading to U.S. waters using the following assumptions and data: 



rv-c 



