APPENDIX I Toxicity Identification Evaluation Reports for Chollas ...

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Toxicity Identification Evaluation of Sweetwater River Stormwater Using Selenastrum capricornutum August 2006 methanol used in this manipulation was likely responsible for the toxicity produced by this treatment. The 0.025 mg/L PBO treatment did not significantly affect growth in the 100% sample concentration (83.64 RFU Chlorophyll) relative to growth in the unmanipulated Baseline test (69.70 RFU Chlorophyll in the 100% sample concentration) at P=0.05. Growth in the 0.025 mg/L PBO treatment blank was 87.07 RFU Chlorophyll. Statistical analysis showed that while there was no significant increase in growth in the 75 or 100% sample concentration of the 0.025 mg/L PBO treatment, growth was significantly elevated in the 50% sample concentration compared to growth in the 0.025 mg/L PBO treatment blank. The 0.050 mg/L PBO treatment did not significantly affect growth in the 100% sample concentration (71.34 RFU Chlorophyll) relative to growth in the unmanipulated Baseline test (69.70 RFU Chlorophyll in the 100% sample concentration). Growth in the 0.050 mg/L PBO treatment was 93.16 RFU Chlorophyll. Statistical analysis showed that while there was no significant reduction in growth in the 75 or 100% sample concentration of the 0.050 mg/L PBO treatment, there was significantly elevated growth in the 50% sample concentration compared to the 0.050 mg/L PBO treatment blank. The NOEC was 100% of the sample concentration and the IC 50 was greater than 100% for both treatments. A copper sulfate reference toxicant was tested at nominal concentrations of 7, 14, 28, 56 and 112 µg Cu 2+ /L. The calculated 96-hour IC 50 (68.36 µg Cu 2+ /L) was within two standard deviations of the laboratory mean (59.93 µg Cu 2+ /L) at the time of testing. This indicates that the sensitivity of S. capricornutum used in this evaluation fell within the normal range. Weston Solutions, Inc. 9
Toxicity Identification Evaluation of Sweetwater River Stormwater Using Selenastrum capricornutum August 2006 4.1.2 Summary of TIE Performed on October 18, 2005 Sample Table 3: Summary of Growth in TIE tests on Sweetwater Stormwater Sample Collected on October 18, 2005 Test Control (Blank) – Dilution Water Mean Growth – Chlorophyll (RFU) 50% 75% Stormwater Stormwater 100% Stormwater NOEC LC 50 Baseline 113.87 131.75 112.54 69.70 75 >100 C-18 117.4 122.37 86.09 56.8 50 97.32 EDTA 3 92.03 116.02 112.92 85.47 100 >100 EDTA 8 83.91 131.37 131.28 106.96 100 >100 PBO 0.25 87.07 119.17 109.66 83.64 100 >100 PBO 0.50 93.16 137.63 116.7 71.34 100 >100 4.1.3 Statistical Analysis: Differences in Growth Among Stormwater Dilutions Data was evaluated using one-way, fixed factor ANOVA and Dunnett’s multiple comparisons to examine the differences in growth of S. capricornutum among the different dilutions of stormwater. It was determined that regardless of the TIE treatment, significant differences in growth of S. capricornutum were detected among the different dilutions of stormwater (i.e., 0, 50, 75 or 100%) to which S. capricornutum were exposed (ANOVA, P=0.008). Specifically, as depicted in Figure 1, growth of S. capricornutum from highest to lowest in the different stormwater dilutions was as follows: 50%, 75%, 0% (control), and 100%. Growth of S. Capricornutum (RFU) 160 140 120 100 80 60 40 B C A D 0 50 75 100 Stormwater Dilution (%) Figure 1. Growth of S. capricornutum exposed to multiple dilutions of a Sweetwater River stormwater sample. Different letters indicate statistically significant differences among treatments where B>C>A>D. Weston Solutions, Inc. 10
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