ENVIRONMENTAL IMPLICATIONS 



171 



10" 



10-^ 



0) 



10^ 



10' 



10^ 



, 48-hr LC50 



, Solubility 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



60 80 100 120 140 



MOLECULAR WEIGHT 



160 



180 



Fig. 5 Theoretical solubility and LC5 values plotted against 

 molecular weights for a series of aromatic hydrocarbons. 



potentially present in coal-conversion effluents. This divergence in 

 interpretation might be explained if solubility becomes the limiting 

 factor in reaching concentrations in water necessary for toxicity to 

 be expressed. This is show^n in Fig. 5, a theoretical plot of solubility 

 and LC50 vs. molecular weight. To the right of the junction of the two 

 curves, the materials would not be toxic because sufficient quantities 

 would not be in solution. The finding of the preponderance of 

 toxicity in materials with low boiling points (which transects all the 

 chemical classes) quite possibly results from insufficient quantities in 

 the water columns. 



Certain flaws or, more appropriately, certain real -world 

 phenomena detract from this oversimplification. These include: 



1. Differential sensitivity of biological systems to the same 

 molecule 



2. Differential response of biological systems to various isomers 

 of the same compound 



3. Interactive phenomena, both toxicological and physio- 

 chemical, already alluded to 



4. Transport and transformation of materials in the aquatic 

 environment 



For example, quinoline, an aromatic amine, has an LCg of 1.5 

 mg/liter in the fathead minnow and 17.5 mg/liter in the bluegill 



