TRANSPORT OF PLUTONIUM BY RIVERS 687 



TABLE 1 Dissolved 2 3 9 ,2 4 Op^ j^^ Continental Waters 



*mp indicates "mile point" upstream of the mouth of the Hudson, 

 defined as the southern tip of Manhattan Island. The pre treatment 

 procedure of the large-volume samples is indicated by one of the following 

 three letters: U, unfiltered; F, filtered after passing through a 

 continuous-flow centrifuge; S, suspended particles allowed to settle, 

 usually for 24 to 48 hr, before the clarified water was transferred to 

 another tank for processing. 



fMean ± standard error. 



tData from Bennett (1976). 



§Data from Farmer et al. (1973). 



H Data from Wahlgren and Marshall (1975). 



soils of the Hudson drainage basin (~3.5 x 10'* km^). Soluble-phase release of fallout 

 2 3 9,240p^ from Hudson soils thus has a half-time of the order of 10"^ yr and supplies an 

 insignificant amount of dissolved 2 3 9,240p^ ^^ ^j^^ coastal ocean compared with that 

 transported onto the shelf from surface waters of the deep ocean. 



The suspended-load activity of 2 3 9,2 4 0pjj ^^^ which dissolved plutonium concentra- 

 tions are Usted in Table 1 averaged about 20 pCi/kg (18.9 ± 0.9 and 23.4 ± 1.0 pCi/kg). 

 The distribution coefficient (Kj) of 2 3 9,240p^ between the dissolved phase and 

 suspended particles for those two samples was about 1.5 x 10"^. Thus the transport of 

 2 3 9,2 4 0pjj i^y suspended particles equals that in the dissolved phase when the 

 concentration of suspended particles is about 15 mg/liter, a value that is reasonably 

 typical of moderate and low freshwater flow periods in the Hudson. During periods of 

 higher suspended load, the transport of 23 9,24 Op^ ^ ^^^ Hudson is predominantly on 

 particles. 



From the quantities of material dredged annually from New York harbor (~2 x 10^ 

 tons), the downstream transport of particles by the Hudson must be about a factor of 4 



