| OCR Text |
Show 2.6.1 Test Concentrations and Test Material Handling A dilution water control and nominal concentrations of 15.6, 26, 43, 72, 120, arid 200 mgIL selenium were selected based on preliminary range- finding studies. The highest test concentration of selenium was prepared by adding 1.4357 g of reagent grade sodium selenate to 3 L of GSL water, providing a 200 mgIL selenium solution. This solution was mixed for 2 hours in a 5-L cubitainer using a Teflonf'-coated stir bar. All test concentrations were calculated and reported as mgIL total selenium, as opposed to sodium selenate. 2.7 Analytical Verification of Test Concentrations Samples were taken at test initiation and termination from each test concentration and control for verification of total recoverable selenium concentrations. Samples were preserved with nitric acid. The analytical method used was EPA test method 6010, by ICP-MS. A duplicate sample from one randomly selected concentration was collected at test initiation. A unique Parametrix identification number was assigned to each sample and not disclosed to the analytical laboratory. The geometric mean (GM) of total selenium concentrations from the two sampling events was calculated and reported as the measured selenium concentration for the test In addition, the coefficient of variation (CV) was also reported for each concentration. 2.8 Analysis of Biological Data Statistical analyses for the NOEC and LOEC were conducted using the Statistical Package for the Social Sciences (SPSS, Norusis, 1993) in accordance with procedures described in U.S. EPA (1994) and EU (1992). Specific growth rate and cumulative area under the curve were calculated for each replicate and summary statistics for each time period calculated. Reports for all statistical manipulations can be found in Appendix A. Parametrix, Inc. Final Report 6 March 1998 |
