TRANSPORT OF PLUTONIUM BY RIVERS 685 



proper monitoring of the routine operations of these facilities and for developing plans 

 for dealing with any abnormally large releases of transuranic elements that might occur. 



In principle, rivers can carry plutonium and other transuranic elements either in 

 solution or as part of the suspended load. These two transport pathways are probably 

 strongly coupled by some type of quasi-equilibrium partitioning between the two phases 

 and thus cannot really be considered separately. As with many elements that are reactive 

 in natural waters, the classifications of "dissolved" and "particulate" plutonium are based 

 largely on operational procedures, such as whether or not material will pass through a 

 filter of a certain nominal pore size. The actual species distribution of plutonium in 

 natural waters is probably some kind of continuum from small-molecular-weight 

 complexes through silt- or sand-size particles. To further compHcate matters, particles can 

 be transported in suspension or as bed load in a stream or accumulated in depositional 

 environments and either buried or resuspended at a later time. 



There have been relatively few field studies of point-source releases of plutonium to 

 river systems. Three areas in the eastern United States that have received such attention 

 are the Savannah River and its tributary downstream of the reprocessing facility in South 

 Carolina (Hayes and Horton, this volume), the Miami River (a tributary of the Ohio 

 River) downstream of Mound Laboratory in Ohio (Sprugel and Bartelt, 1978) and streams 

 near Oak Ridge, Tenn. These river systems are the focus of ongoing research programs 

 which should provide considerable information about the transport by rivers of 

 plutonium derived from point sources. This chapter discusses the distribution of fallout 

 plutonium in a few natural systems, including the Hudson River and estuary, and 

 attempts to derive some first-order principles by which the transport pathways of 

 plutonium in other river systems can be predicted. The Hudson estuary is now the site of 

 three nuclear reactors, and at least half a dozen other units which are planned for this 

 estuary in the next two decades. 



Plutonium in the Hudson River Estuary 



The Hudson River discharges into one of the large estuarine systems that dominate much 

 of the coastal environment of the northeastern United States (Fig. 1). The Hudson has an 

 unusually long, narrow reach of tidal water (>250 km), most of which is usually fresh. 

 Saline water intrudes only about 40 km from the coastline during seasonal high 

 freshwater discharge and reaches as far inland as 120 km during summer and early fall 

 months of drought years. The near-surface suspended load of the Hudson is relatively low 

 (10 to 20 mg/Uter), as it is for nearly all the larger rivers in the northeastern United 

 States, except during maximum spring runoff and following major storms. 



From studies of the distribution of fallout nuclides and gamma-emitting nuclides 

 released from Indian Point, the patterns of suspended particle transport and recent 

 sediment accumulation in the Hudson estuary have been described (Simpson et al., 

 1976; 1978; Olsen et al., 1978). Much of the estuary has relatively little net 

 accumulation of fine particles, whereas a few areas, such as marginal coves and especially 

 New York harbor, account for a major fraction of the total deposition of fine particles 

 containing fallout and reactor nucHdes. The zone of major sediment accumulation is more 

 than 60 km downstream from the reactor site, and the time scale of transport of fine 

 particles labeled with reactor nucUdes from the release area to burial in the harbor 

 sediments varies from probably less than a month to years. At present there is no 

 evidence in the Hudson sediments, including New York harbor, of releases of reactor 



