APPENDIX I Toxicity Identification Evaluation Reports for Chollas ...

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Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Materials and Methods August 2006 Solutions by Bryn Phillips (personal communication, Granite Canyon Laboratory). In this method, the protein Bovine Serum Albumin (BSA) is used as a control for the esterase. Specifically, if toxicity is reduced in both the BSA treatment and the carboxyl esterase treatment, this indicates that both BSA and esterase are adsorbing the chemicals in the water samples. In contrast, if toxicity is only reduced in the carboxyl esterase treatment, this indicates that the chemicals in the water sample have been enzymatically altered by the carboxyl esterase, and that these chemicals may be pyrethroids due to the affinity of carboxyl esterase for these compounds. This sample treatment was only performed on the January 2, 2006 and February 19, 2006 stormwater samples. A stock solution of 2 mg carboxyl esterase/mL was prepared. The carboxyl esterase treatment was prepared by diluting the carboxyl esterase stock solution to achieve a final concentration of 0.52 μg/mL (or 1.25 Units/ml) in stormwater (100 percent sample concentration only). A stock solution of 2 mg BSA/mL was also prepared. The BSA treatment was prepared by diluting the BSA stock solution to achieve a final concentration of 0.52 μg/mL in stormwater (100 percent sample concentration only). 3.6 STATISTICAL ANALYSIS At the conclusion of all tests, test species data were evaluated statistically using ToxCalc to determine the ECp, or estimated concentration that causes any effect, either lethal (LC) or inhibitory (sublethal; IC), on p% of the test population, and NOEC values. ToxCalc is a comprehensive statistical application that follows standard guidelines for acute and chronic toxicity data analysis. Statistical effects can be measured by the ECp. The LC 50 or LC 25 is the point estimate of the concentration at which a lethal effect is observed in 50% or 25% of the test organisms. ECp values include 95% confidence limits where available. The NOEC is the highest tested concentration at which mortality and other sublethal measured effects are not significantly different from the those in the control treatment. All statistics were run against treatment blanks to mitigate for any artifactual effect that the treatment had upon the toxicity. The non-parametric Wilcoxon Signed Rank test (WSR) was used according to Gilbert (1987) to determine whether or not there were statistically significant differences between survival of H. azteca in TIE treatments and survival of H. azteca in the Baseline, or untreated stormwater sample. Briefly, this method involved the following steps: (1) subtracting the concentrations of contaminants (for specific contaminants/classes separately) in sediment within and adjacent to the leasehold from the reference level, (2) ranking these differences according to their absolute values, and (3) calculating the WSR statistic of the test according to standard procedures (Gilbert 1987). The null hypothesis was rejected when the WSR statistic was below the Wilcoxon critical value (from a pre-determined table in Zar 1991). Weston Solutions, Inc. 13
Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Materials and Methods August 2006 4. RESULTS 4.1 TIE TESTS ON CHOLLAS CREEK STORMWATER USING HYALELLA AZTECA 4.1.1 Results of TIE Performed on the October 18, 2005 Sample Results for the TIE performed on the October 18, 2005 sample are summarized in Table 3. Table 3. Percent Survival of Hyalella azteca in TIE Tests performed on the Chollas Creek Stormwater Sample Collected on October 18, 2005. Test Control (Blank) – Dilution Water Stormwater Dilution 50% Stormwater (1X 1 ) 75% Stormwater (2X 1 ) 100% Stormwater (4X 1 ) NOEC LC 50 Baseline 86.7 100 80 80 2 100 >100 Non-aerated Baseline 73.3 93.3 86.7 66.7 100 >100 EDTA – 3 mg/L 60 66.7 66.7 40 100 >100 STS - 10 mg/L 86.7 86.7 80 60 75 >100 Aeration 53.3 93.3 80 33.3 100 97.37 Filtration 46.7 100 100 100 100 >100 Solid Phase Extraction (C 18 ) 93.3 100 100 100 100 >100 Methanol Elution 33.3 86.7 33.3 0 2X 2.2X pH 6.8 100 93.3 93.3 86.7 100 >100 PBO - 0.025 mg/L 86.7 13.3 26.7 0
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