isotope i at a distance x from the center of the source (ia the direction of 

 the current) is approximately 



C. = ^l__ exp 1-^^] (1) 



IKx / 



Qi 



1 ZD-^^zTkUx \4 



•where K is the diffusivity coefficient ( under turbulent conditions ) and y is 

 the transverse distance measured from the axis of the dispersed material ( see 

 Fig. 1 ). Eq.(l) applies for Fickian type diffusion and since it is restricted to 

 distances x which are large relative to L , the formula cannot be used for 

 concentrations within the source region. The equation is an adaptation of the 

 formula given by Sutton (p. 137 , Eq. 4.43) for a continuous line source across 

 wind. In the present case the plume is taken with a vertical plane of symmetry 

 yrtth the material from the source dispersing equally on each side ; consequently 

 we take half the source strength given by Sutton's formula (where the dispersal 

 is confined to one side of the plane of symmetry only) . However, if the source 

 were very close to shore then Sutton's formula would apply directly. Thus the 

 influence of the proximity of the shore can at the very most, increase the con- 

 centrations by a factor of two over those indicated by Eq. (1). This is small 

 considering the fact that other safety factors involved in our present computations 

 tend to give concentrations which are overestimated by at least one or even two 

 orders of magnitude . 



The maximum concentration for isotope i at distance x from the 

 source is simply 



Qi 



(Ci) = . (2) 



"" " 2D ^ZttKUx 



max 



♦ Note that in Sutton's formula 4.44 , U is omitted in the term ^2f[ KUx ; 

 apparently this is a typographical error . 



