MERCURY CONTAMINATION STANDARDS 261 



contaminated with mercury to the extent that fish and other 

 organisms taken from these waters are unsafe to eat (Anonymous, 

 1971). This process shows httle sign of abatement. Accordingly, high 

 priority should be given to research and development technology to 

 remove mercury from existing contaminated areas. These could 

 include bacterial strains and other methods to solubilize mercury 

 from sediments, with subsequent removal and reclamation from 

 waterways via biological or abiotic vectors. One interim alternative 

 would be to feed mercury-contaminated scrapfish and seafoods as 

 partial diet supplements to migratory anadromous fishes. Removal 

 by dredging of mercury-contaminated sediments and storage at 

 designated locations is another alternative, but numerous problems 

 are associated with this approach as currently practiced. 



5. Develop monitoring criteria. Preventing mercury feedback into 

 human diets is of paramount importance. To achieve this goal, we 

 must refine existing mercury-residue standards for waste waters, 

 sediments, and biota, with due consideration for geographical 

 location and economic aspects of the resource. 



It is emphasized at this time that mercury in marine waters is 

 usually bound to bottom materials, proteinaceous matter, plankton, 

 and higher organisms. Even in water heavily polluted by mercury 

 discharges, only a fraction is found free in solution, except near the 

 point of discharge. The best available evidence indicates that total 

 mercury in waste waters, dissolved plus particulate, emanating from 

 the pipe terminus should not exceed 1.0 /ag/liter; however, I believe 

 two additional restrictions on pipe terminus concentrations are 

 warranted to achieve a reasonable margin of safety. First, outfall 

 volume should not exceed one-fiftieth of the mean daily waterflow 

 of the receiving water. Second, the receiving waters upstream of the 

 terminus (or in direction of positive tidal flow, if applicable) should 

 contain less than 0.02 /ug/liter total mercury, dissolved plus particu- 

 late. The final recommended value of 0.0392 /ug total Hg/liter after 

 mixing is about 2.5 times lower than the currently recommended 

 value of less than or equal to 0.10 /ig/liter proposed by the National 

 Academy of Sciences (1973); however, the 0.10 yug/liter does not 

 consider mixing processes. 



Because benthic animals sometimes reflect the mercury levels of 

 their sediment substrate, it is recommended that sediments in outfall 

 environs should not exceed 500 jUg total Hg/kg. This value is less than 

 the 750 )ug/kg set by the Environmental Protection Agency (1977) 

 for solid wastes disposed offshore. 



For biological monitoring, two groups of indicator organisms are 

 recommended, filter-feeding bivalve molluscs and piscivorous fishes. 



