buried in the sediment had turned to black. The hydrogen sulfide in 

 the sediment had reacted with either the tin or the lead present in 

 the PVC plastic panel to form tin or lead sulfide which is black. In 

 another marine exposure test a vinyl paint (orange) containing lead 

 had changed to black when exposed in an anaerobic environment contain- 

 ing hydrogen sulfide in the deep-ocean environment. There was no 

 significant difference in hardness between the two sections. It 

 should be noted, however, that polyethylene and nylon showed a 

 slight increase in hardness where it was exposed in seawater as 

 compared to the section buried in the sediment. There were some 

 differences in hardness between the unexposed (dry) and the exposed 

 (wet) panels. For example, polyethylene, polypropylene, vinyl (pp) , 

 PVC, polystyrene, and TFE increased in hardness after being exposed 

 in seawater. On the other hand, phenolic laminate and nylon panels 

 decreased in hardness. The hardness of vinyl (pm) polycarbonate, 

 acrylic, and polyurethane panels remained about the same before and 

 after exposure in the sea. 



Most of the plastic materials did not absorb significant amounts 

 of moisture during the one year exposure in the harbor. The exceptions 

 to this were phenolic laminate and nylon panels which absorbed signif- 

 icant amounts of moisture during this period. 



The recovered rope specimens (nylon, polyester, polypropylene, 

 manila, and cotton) were covered with a layer of fine silt and some 

 encrusting bryozoans. The fibers of manila and cotton ropes were 

 deteriorated so severely by microorganisms that the fibers could 

 easily be torn apart by one's fingers (Figure 6 and 7). The results 

 of a tensile strength test conducted on the recovered synthetic ropes 

 are presented in Table 2. The tensile strength of polyester, poly- 

 propylene, and nylon ropes decreased by 6.3, 9.5, and 19.7 percent, 

 respectively. Data on tensile strength of manila and cotton ropes 

 were not obtained since these had been severely deteriorated by 

 biological activity. It is of interest to note that, although the 

 tensile strength of polypropylene ropes had decreased when exposed 

 in the bottom sediment, it had increased when such rope specimens 

 were exposed in the deep-ocean environment (6000-ft depth). -> 



Visual examination of the electrical cable insulations (butyl 

 rubber, neoprene rubber, natural rubber, PVC, polyethylene, and TFE) 

 conducted under a stereoscopic microscope showed that the surface of 

 a natural rubber insulating material had deteriorated badly, probably 

 due to effects of hydrogen sulfide and microorganisms (surface crack- 

 ing). The other materials were in good condition. Fouling organisms 

 which were found on the various insulating materials included en- 

 crusting and branching bryozoans, hydroids, calcareous tubeworms , 

 and small barnacles (Figure 8). 



The 1/4 x 4 x 12 inch Douglas fir panel which was exposed 

 immediately above the bottom sediment was riddled by Bankia and 

 Teredo (molluscan borers) and also by Limnoria quadripunctata and 



