The EPA laboratory in Gulf Breeze, Florida analyzed samples collected from 

 4 sites in the Chesapeake Bay once each week from May 1986 to September 

 1986. A tidal component to the variation in TBT concentrations was 

 observed. The butyl tin was derivatized with borohydride, separated to 

 species by gas chromatography and quantified by mass spectrometry. The 

 detection limits were given as 10 to 60 ng/1 for TBT. 



The only other region of the U.S. to be sampled in an comparable manner 

 is San Diego Bay, California. The impetus for theses sampling programs 

 was that both Chesapeake Bay and San Diego Bay have major U.S. Navy 

 facilities. The Navy baseline study in San Diego Bay (Grovhoug et al., 

 1986) indicate that the highest environmental concentrations of TBT were 

 associated with drydock facilities and recreational boating facilities. 

 In Pearl Harbor, where the Navy drydock facilities are located, TBT was 

 not detected. In Honolulu Harbor, where recreational vessels predominate, 

 TBT concentrations in the water column were higher by an order of 

 magnitude than concentrations of TBT measured around drydock areas. 



Studies conducted by the U.S. Navy (NOSC) in San Diego Bay have reported 

 concentrations in Commercial Basin to be <2.0 ng/1 in 1983 (Stang and 

 Seligman, 1986) . By 1986 the maximum measured concentration had become 

 520 ng/1 (Valkirs et al., 1986). Monitoring studies conducted by Goldberg 

 in the same area analyzed six surface water samples collected in January 

 1986, below the surface at an arms depth, from the Selter Island Marina 

 Marlin Club Dock and found 4 above 400 ng/1 (Stallard et al., 1987). 

 Shelter Island is a very large recreational boating marina. The San Diego 

 Bay Studies by NOSC utilized borohydride derivatization and gas 

 chromatography to separate tributyltin and dibutyltin. Unspeciated total 

 tin was measured from sediment samples collected at the same locations as 

 the water samples. Sediment samples were collected by Stang and Seligman 

 (1983) at the same time and were found to contain TBT concentrations of up 

 to 551 ug/kg. The sediment samples collected by Valkirs et al. (1986) 

 found concentrations up to 228 ug/kg. In general, the San Diego Bay 

 studies found that sediment concentrations were three orders of magnitude 

 higher than the concentrations in the overlying water. 



4.7 IABORATORY ANALYTICAL METHODOLOGIES 



As the nature and extent of TBT concentrations in the environment have 

 become better understood as a result of monitoring studies, the focus of 

 current research has shifted to study the speciation of butyltins and the 

 relative partitioning of butyltins into the surface microlayer, the water 

 column, and bottom sediments. The degradation pathway for tributyltin is 

 progressive debutylation, to dibutyltin and then to monobutyltin. Each of 

 these chemical species is less toxic than its predecessor. 



With the ability to speciate organotins in the laboratory has come the 

 discovery of tetrabutyltin in same locations (Olson et al., 1985; Matthias 

 et al . , 1986) . Tetrabutyltin has not been identified as a degradation 



IV-4J 



