aquatic toxicant that is strongly pH-dependent is ammonia. Total ammo- 

 nia concentrations in the acutely toxic samples ranged from 32.7 mg/1 

 (milligrams per liter) to 59.8 mg/1 (Table 4.3). 



4.2.2 1991. Five of the seven sites evaluated in 1991 had the same 

 characterization pattern as in 1990 (Table 4.4). The only manipulation 

 to consistently reduce toxicity was the graduated pH test, again 

 indicating a pH-dependent toxicant such as ammonia (Table 4.3). Total 

 ammonia concentrations in the 1991 samples ranged from 28.6 mg/1 to 51.2 

 mg/1 (Table 4.3). The characterization pattern differed for porewaters 

 from DP277.0 on the Des Plaines River and CS307.4 on the Calumet Sag 

 Channel (Table 4.4). Toxicity in these porewaters was reduced by 

 filtration and solid phase extraction with a Cjg column, indicating that 

 toxicity is due to non-polar organic compounds associated with 

 filterable particles. These samples contained visible quantities of 

 oil. 



In summary, Phase I results from 1990 and 1991 indicate that acute 

 toxicity in most sediment porewaters from the Upper Illinois Waterway is 

 attributable to a pH-dependent toxicant, most likely ammonia. Porewater 

 from one location in the lower Des Plaines River and one location in the 

 lower Calumet Sag Channel contained toxicity attributable to non-polar 

 organics associated with oil or grease. 



4.3 Toxicity Identification Evaluation - Phase II 



Phase II techniques were used to isolate toxicants in porewaters 

 from the seven sites where ammonia was suspect and the two sites where 

 non-polar organics were suspect. The zeolite columns completely removed 

 acute toxicity from porewaters where ammonia was suspect (Table 4.5). 



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