10-20 



copper. Thus, we conclude that the atmospheric burden of trace metals 

 to the sediments of Long Island Sound is not trivial and indeed may be 

 dominant for at least some elements. 



The Kinetiaii of Trace-Metal Scavenging from the Water Column 



210 

 The above discussxon tacitly assumed that Pb and the trace 



metals have a very short transit time as dissolved species in the water 



column. This implies efficient scavenging and removal of these nuclides 



from Long Island Sound. This hypothesis is supported by the results of 



210 

 Benninger (1978) on Pb distribution in Long Island Sound waters. 



210 

 Figure 10-12 shows that virtually all of the Pb in Long Island Sound 



210 

 waters is associated with particles. The dissolved Pb concentration 



is nil. When this is compared to the much higher open-ocean surface- 

 water concentrations (Nozaki, Thomson and Turekian, 1976) , it is clear 

 that nearshore processes quickly and effectively remove reactive chemi- 

 cal species from the water column. Aller and Cochran (1976) came to the 



234 

 same conclusion regarding Th in Long Island Sound. Together these 



results imply that the mean residence time of reactive metals in the 



water of Long Island Sound with respect to removal into the sediments is 



of the order of days. 



The agent of scavenging of the trace metals is almost certainly 



adsorption on particles rather than association with plankton. Table 10-2 



210 

 shows how the flux of Pb out of the ocean surface is ascribable 



almost totally to the effect of particle scavenging. Most other reactive 



elements probably behave in a similar fashion. Most of the particles in 



Long Island Sound are resuspended bottom sediments and probably include 



manganese and iron oxide coatings that are effective adsorbers of many 



trace metals. 



Any geographic redistribution of elements in Long Island Sound 

 is thus affected by the transport of particles from the moment of sca- 

 venging to final burial in the sediments (see Turekian, 1977 for a more 

 detailed discussion) . This generalization does not hold for manganese 

 or iron completely as these elements (and others affected by coprecipita- 



