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such pesticides as DDT and its derivatives, and polychlorinated biphenyls 
(PCBs). It is still problematical as to whether or not pelagic and benthic 
Organisms can acquire significant body burdens of chlorinated hydrocarbons 
from polluted sediments. Even when they do, most benthic organisms do not 
exhibit acute symptoms of toxicity. As a result, concern is expressed as 
to the potential for elicitation of chronic responses and bioaccumulation. 
Clearly these matters are again the reason why “special measures" of dis- 
posal can be so effective in minimizing potential harm to the environment 
while providing time for biodegradation of these compounds. 
It should be noted that Burks and Engler (1978) demonstrated that chlori- 
nated hydrocarbons are normally very strongly bound to pariculates in 
sediment-water systems. It is in this state that micro-organisms may act 
to degrade many of these compounds. This activity in regard to DDT and 
related species is well known, but less well known is the fact that PCBs 
are also degraded by sediment-living bacteria and fungi. It is reported, 
however, that the rates are inversely proportional to chlorine number but 
only very slowly above four (Wong and Kaiser, 1975, Ahmed and Focht, 1973). 
Thus, because of the long-term stability of many chlorinated hydrocarbons 
in sediments any problems will be associated with gradual release and sub- 
sequent accumulation by organisms. In quiescent offshore waters, say, 30 
meters or more depth, release directly from contaminated sediments* to the 
water column should present low environmental risk. Even this low risk 
factor could be reduced further by mounding the polluted material and then 
capping it with clean material having considerable clay and organic matter 
in it. Again, "special care" measures can ameliorate the impact of these 
compounds by sequestering them in isolation from benthic organisms and 
providing time for biodegradation. Covering polluted dredged material with 
cleaner sediment from the same project to accomplish this sequestering has 
also been advocated by Rhoads et al. (1978) and Gambrell et al. (1978). 
