Table 4.6. Toxicity of sediment porewater following fractionation by 

 filtration, centrifugation, and column absorption and extraction. 

 Fractions were tested for toxicity using Ceriodaphnia dubia. Toxicity 

 is expressed as the 48-hour LC50, reported as % of sample fraction in 

 test solution, and as toxic units, (100/LC50). Numbers in parentheses 

 indicate a range of dilutions that caused 50% mortality in 48 hours. 



^Porewater was filtered, then the filters were extracted with methylene 

 chloride. Extracts tested for toxicity. 



'^Centrifugation at 10,000 g for 30 minutes to settle the particles in 

 the porewater. Supernatant tested for toxicity. 



^200-ml samples of supernatants from b were passed through absorption 

 columns, then aliquots were taken after passage of 25 ml and 100 ml of 

 methanol through the columns. Aliquots tested for toxicity. 



>100 indicates that the undiluted fraction did not kill at least half 

 the test organisms in 48 hours. 



indicates that toxic units could not be calculated because the 



undiluted fraction was not lethal within the 48-hour exposure period. 



37 



