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 water quality measurements were taken. These measurements included temperature, total chlorine, total ammonia, pH, dissolved oxygen, and salinity. 3.5 PHASE I TIE METHODS 3.5.1 Protocol Modifications Measures to conserve time and resources required to conduct TIE testing have been developed and approved by the USEPA (USEPA, 1992). This study incorporated modifications which allowed for the reduction in number of test concentrations, replicates, organisms per replicate, and volumes for all TIE tests conducted, relative to test conditions used in standard toxicity tests. The test concentrations used for the TIE tests performed in October and November of 2005 included 50, 75, and 100 percent sample concentrations. In January and February of 2006, only the 100 percent sample concentration from Chollas Creek was tested due to limitations in sample volume. For the H. azteca toxicity test, three replicates with five organisms per replicate in a volume of 50 mL were used in TIEs performed in October, November, and January. In the February TIE, the replicate number was increased to five replicates with five organisms per replicate in a volume of 50 mL, to decrease variability in the test results, and increase our power to detect differences among treatments. Treatment blanks were created for each TIE test to determine the effects of the manipulation on laboratory dilution water. The results of these blanks were used to determine if any changes in toxicity of the control (dilution water) were impacted by the chemical or physical manipulation of the sample. 3.5.2 Baseline Tests The baseline test assesses the toxicity of the unmanipulated sample run concurrently with the TIE tests. This test confirms the presence of toxicity in the stormwater sample, and benchmarks the toxicity for comparison to toxicity in TIE treatments. On Day 1 of the October 18, 2005 Chollas Creek toxicity test, the dissolved oxygen level of the water quality surrogate for the 100 percent sample concentration briefly dropped below the protocol limit of 4.0 mg/L. The test was aerated and dissolved oxygen levels returned within range. To avoid a contribution of toxicity in the Baseline tests due to low dissolved oxygen levels, an Aerated and a Non-aerated Baseline test were performed. The Aerated Baseline test received head space aeration, at low air flow rates, for 5 minutes each day of high grade oxygen. It should be noted that this Aerated Baseline test differs from the aerated test below, in which the sample was aerated at high flow rates for an hour prior to test initiated. The Baseline tests conducted on the November 11, 2005 Chollas Creek sample were performed in both plastic and glass test chambers. This comparison was done because it was hypothesized that pyrethroids could be the causative agent for the toxicity measured in samples from this site. Specifically, pyrethroids are known to adsorb to plastic, leading to a timedependent reduction in toxicity (Wheelock et al., 2005). 3.5.3 Ethylenediaminetetraacetic Acid (EDTA) Tests EDTA tests were performed to determine whether metals were the causative agent of toxicity in the Chollas Creek stormwater sample. Specifically, EDTA binds certain ionic metals, making them biologically unavailable to the test organisms. A reduction in the toxic response of a sample treated with EDTA may indicate the presence of divalent (metal) cation toxicity. Weston Solutions, Inc. 9
Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Materials and Methods August 2006 Two series of EDTA tests were conducted with concentrations of 3.0 and 8.0 mg/L on the October 18, 2005 stormwater sample. First, a stock solution of 2.5 g/L of EDTA was prepared. EDTA treatments were prepared by diluting the EDTA stock solution to final concentrations of both 3.0 and 8.0 mg/L in stormwater (50, 75, and 100 percent sample concentrations) and dilution water. The EDTA was allowed to react with the sample for a minimum of 2 hours prior to the addition of the test organisms. Prior to test initiation, the pH was adjusted to the initial pH of the stormwater sample using 0.12 and 2.0 N hydrochloric acid (HCl) and 0.5 M sodium hydroxide (NaOH). Lower concentrations of EDTA were used on the January 2, 2006 stormwater sample, because the higher concentration of EDTA (8.0 mg/L) demonstrated toxicity to H. azteca in the dilution water control in the October Phase I TIE. Thus, EDTA tests were conducted with concentrations of 0.8 and 3.0 mg/L and were prepared as described above. For the TIE using the February 19, 2006 stormwater sample, only one concentration of EDTA (3.0 mg/L) was used in the TIE, due to high survival in the control (blank) using this EDTA concentration. Specifically, we wished to use the highest concentration of EDTA in the test that would not cause toxicity to the test organisms. EDTA treatment blanks for all TIEs were prepared identically to the stormwater samples described above, using dilution water instead of stormwater. 3.5.4 Sodium Thiosulfate (STS) Tests STS tests were performed to determine whether oxidative chemicals were the causative agent of toxicity in the Chollas Creek stormwater sample. Specifically, the addition of STS removes the effects of oxidative compounds including compounds such as chlorine, bromine, and ozone. This treatment also has success in removing some cationic metals. Two series of STS tests were conducted with concentrations of 10 and 25 mg/L. A stock solution of 2.5 g STS/L was prepared. STS treatments were then prepared by diluting the STS stock solution to final concentrations of 10 and 25 mg/L, separately, in stormwater (50, 75 and 100 percent sample concentrations). In the TIE using the February 19, 2006 stormwater Sample, only one concentration of STS (10 mg/L) was used, due to high survival in the STS treatment control (blank) in the January TIE. STS treatment blanks for all TIEs were prepared identically to the stormwater samples described above, using dilution water instead of stormwater. 3.5.5 Aeration Tests Aeration tests were performed to determine whether volatile chemicals and surfactants were the causative agent of toxicity in the Chollas Creek stormwater sample. Aeration helps reduce concentrations of volatile chemicals and surfactants. The stormwater sample (300 - 750 ml) was aerated with filtered air at a medium to high rate (500 mL air/min) for a minimum of one hour at test temperature. After one hour the sample was collected by siphoning from the middle of the beaker to avoid surfactants on the side of the beaker. This aerated sample was then used to prepare 200 mL dilutions of 50, 75 and 100 percent samples. Aeration treatment blanks for all TIEs were prepared identically to the stormwater samples described above, using dilution water instead of stormwater. Weston Solutions, Inc. 10
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