predominant in Aroclor 1260, which have lower steric effect coefficients. 

 Structure-activity relationships, particularly for PCBs, can be applied to 

 predictive models of contaminant cycling and biomagnification--and promises to 

 become a fruitful research area. 



Pal et al. (1980), in a review of PCBs in plant-soil systems, indicated 

 three important research needs. First, many isomers of several PCB 

 formulations have not been studied with respect to their biotransformation, 

 volatilization, photodecomposition, adsorption, and transport. Second, highly 

 chlorinated biphenyls, especially tetra-, penta-, and hexachlorobiphenyls, 

 have not been evaluated for uptake by crops, volatilization, or distribution 

 in soil layers. The relative build up and assimilation in soil-plant systems 

 of hepta-, octa-, nona-, and decachlorobiphenyls have not been evaluated or 

 studied. Finally, data are lacking on partition coefficients of PCBs between 

 soil and water, water and atmosphere, atmosphere and plant populations, and 

 during flow in food chains. A similar case can be made for most fish and 

 wildlife species of current concern. 



