hydrocarbons. MacKay, Halcrow and Thorton (1972) in their study of the 

 Clyde Estuary sludge disposal area in England reported the highest values 

 of organic carbon near the center of the dump. Shelton (1971) reported 

 a buildup of organic matter in the Thames disposal area, which he 

 suggested may be the result of the normal traction load of organic 

 matter usually found in the River Thames. Bottom sediments near the 

 dumping grounds of the N.Y. Bight are also characterized by a high 

 organic content in excess of normal values observed in nonspoil areas, 

 (Figs. 33 through 35). Apparently this high organic content of the 

 sediments has resulted from the dumping of wastes. Sewage sludge 

 accounts for most of the organic material; dredge spoils are composed 

 primarily of inert substances. However, toxic organic substances in 

 polluted dredge spoils (even in low concentrations) may constitute a 

 greater environmental concern than those of the sewage sludges. 



Organics in the sediments of the Bight dumping grounds may include 

 natural organic materials, synthetic organic compounds, and petrochemicals. 

 The relative contents or effects of each type have not yet been established 

 by the studies completed. 



The natural organic materials in the sediments of the dumping grounds 

 result from natural decomposition of marine plants and animals, or from 

 organic constituents contributed by dredge spoils and sewage sludges. 

 These materials are not harmful to the marine environment, and some- 

 times their addition may be beneficial. The major problem of the organic 

 fraction is their biochemical oxygen demand. Large concentrations in the 

 sediments may consume the dissolved oxygen and result in anaerobic con- 

 ditions at the sediment-water interface. Indirectly, reducing conditions 

 caused by these wastes, could affect the chemistry of other compounds. 

 The effects of reduction of dissolved oxygen were discussed on page 117. 



Another class of organic materials in the sediments of the dumping 

 grounds may be synthetic organic chemical compounds. Their content in 

 the sediments has not yet been adequately determined by any of the 

 studies completed. These compounds may be accumulating in the sediments 

 of Harbor, and thus be included in the dredge spoils dumped in the Bight. 

 To a lesser extent, these compounds may also be in the sewage sludges. 

 The origin of these compounds may be point sources such as industrial 

 discharges, or sources such as atmospheric precipitants or runoff from 

 agricultural areas. Examples of these types of compounds are pesticides 

 such as DDT, or polychlorinated biphenyls (PCBs), which have a cumulative 

 toxic effect on marine life. Depending on the physicochemical characteris- 

 tics of the marine environment, these synthetic organic materials may be 

 found relatively undisturbed or may be broken down into other compounds. 

 A pesticide such as DDT may be broken down by micro-organisms into DDE 

 and DDD, both of which are insoluble in water. These chemicals may be 

 taken into the fatty tissue of certain marine organisms and be transmitted 

 up the food chain. PCB's are toxic substances which, according to 

 Gustafson (1970), present a real danger to marine life when accumulated 

 m the sediments. 



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