MERCURY CONTAMINATION STANDARDS 253 



magnitude higher in the vicinity of chlor^-alkali plants and similar 

 industrial operations (Kazantzis, 1971). Mercury levels in sediments 

 varied widely and tended to be elevated in the neighborhood of 

 sewer outfalls (Klein and Goldberg, 1970), sludge disposal areas, and 

 especially areas impacted by mercury wastes from industrial opera- 

 tions, such as Minamata Bay, Japan (Irukayama, 1967). Vucetic, 

 Vernberg, and Anderson (1974) reported values ranging from 130 to 

 1500 /ig/kg of mercury in sediments in the Adriatic Sea, and Williams 

 and Weiss (1973) found 390 ^ig/kg in pelagic clays collected 430 km 

 southeast of San Diego, Calif. It is reported that mercury in seawater 

 exists almost entirely bound to suspended particles (Jemelov et al., 

 1972), that the surface area of sediment granules is instrumental in 

 determining final mercury content (Renzoni, Bacci, and Falciai, 

 1974), that conversion and transformations occur in the surface layer 

 of the sediment or on suspended organic particles in the water (Dean, 

 1972; Fagerstrom and Jernelov, 1972; Jernelov et al., 1972), and, 

 finally, that mercury-containing sediments would require many 

 decades to purge themselves naturally to background levels (Langley, 

 1973). 



Mercury— sediment— water interactions affect uptake by marine 

 life. Bivalves can accumulate mercury directly from seawater, and 

 molluscs had higher concentrations of the metal in turbulent waters 

 than in clear waters (Raymont, 1972). Further, marine organisms 

 feeding in direct contact w.ith sediment have higher overall mercury 

 levels than those feeding above the sediment— water interface 

 (Klemmer, Unninayer, and Ukubo, 1976). 



Residues in Biota 



Table 2 summarizes the ranges of concentrations of mercury in 

 field collections of marine flora and fauna. These data support the 

 findings of other investigators (Cocoros, Cahn, and Siler, 1973; 

 Huckabee and Blaylock, 1972; Jernelov and Lann, 1971; Knauer and 

 Martin, 1972; Skei, Saunders, and Price, 1976; Stickney et al., 1975), 

 who demonstrated that the efficiency of mercury transfer through 

 natural marine food chains among lower trophic levels is compara- 

 tively low. Higher trophic levels, such as fishes, fish-eating birds, and 

 mammals, however, exhibit marked mercury amplification. The 

 variability of concentrations is partly explainable in terms of 

 collection locale; some field collections were taken from areas where 

 human activities have raised the mercury content in the aquatic 

 environment above natural levels, thus producing a significant 

 increase in the mercury content of endemic fauna (Hearnden, 1970; 

 Johnels et al., 1967; Kazantzis, 1971; Kleinert and Degurse, 1972; 



