All test chambers
containing the sediment/water systems were fortified with
the test substance at the start of the test by applying
approximately 100 íL of the radiolabeled dosing solution
the water layer to achieve a nominal test concentration
ranging from 0.04 to 0.5 mg/L. Test concentrations were
targeted for the low íg/L range while maintaining sufficient
radioactivity for analysis of biotransformation products at
10% parent in the water and sediment phases. The radiopurities
of the radiolabel test materials for the 3 pharmaceuticals
and the specific activities of each are shown in Table
1. Following the addition of the test material to each test
chamber, the water layer was gently mixed, making sure to
minimize disturbance of the underlying sediment.