APPENDIX I Toxicity Identification Evaluation Reports for Chollas ...

More documents

Recommendations

Info

Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Materials and Methods August 2006 3.5.6 Filtration Tests Filtration tests were performed to determine whether the chemicals causing toxicity were bound to particulate matter in the Chollas Creek stormwater sample. A reduction in toxicity following filtration indicates that chemicals are particulate bound. The October 18, 2005 stormwater sample manipulation was prepared by filtering stormwater (3 L) through a preconditioned nominal 1 µm groundwater sampling capsule using a peristaltic pump. Half of the filtrate (1.5 L) was reserved for the C 18 SPE Test described below. The remaining filtrate (1.5 L) was then used to prepare 200 mL dilutions of 50, 75 and 100 percent samples. On November 11, 2005 the filtration test was repeated using a 1 µm glass fiber filter and a vacuum pump to compare to toxicity resulting after filtration through the groundwater sampling capsule. Specifically, it was uncertain whether the groundwater sampling capsule was removing just particulate matter (i.e., the capsule may have removed adsorptive chemicals as well). The January 2, 2006 stormwater sample manipulation was prepared by filtering 1.25 L of stormwater. Approximately 360 mL of the filtrate was reserved for the C 18 SPE Test described below. The remaining filtrate (~890 mL) was reserved for the C 18 SPE. Stormwater (1.35 L) from the February 19, 2006 event was filtered and approximately 300 mL was used in the filtration test, while approximately 1 L was reserved for SPE. The filtration treatment blanks for all TIEs were prepared identically to the stormwater sample filtration described above, using dilution water instead of stormwater. 3.5.7 C18 Solid Phase Extraction and Methanol Add-Back Tests SPE followed by methanol elution is a test performed to evaluate whether non-polar organics were the causative agents of toxicity. Specifically, non-polar organics are initially retained on the C 18 column and may be eluted with methanol. In subsequent toxicity tests, toxicity associated with the methanol extract is toxicity is indicative of non-polar organics. The October 18, 2005 stormwater sample manipulation was prepared by passing 1.5 L of filtered stormwater sample through a pre-conditioned 5 g C 18 SPE column at a rate of 5 mL per minute using a peristaltic pump. The January 2, 2006 stormwater sample manipulation involved extracting 887.6 mL of filtered sample through a pre-conditioned 1 g C 18 SPE column at a rate of 5 mL per minute using a peristaltic pump. The February 19, 2006 stormwater sample manipulation involved extracting 1.12 L of filtered sample through a pre-conditioned 1 g SPE C 18 column at a rate of 5 mL per minute using a peristaltic pump. The SPE C 18 treatment blanks for all TIEs were prepared identically to the stormwater sample extractions described above, using dilution water instead of stormwater. The SPE C 18 column was then eluted with 100% reagent grade methanol to extract any contaminants bound to the column. To elute the column for the October 18, 2005 stormwater event, a total of 4.5 mL of 100% methanol was passed through the 5 g column in three, 1.5 mL aliquots, and collected into a test tube. The methanol was then added to clean control water at concentrations equaling 1.0, 2.0, and 4.0 times the concentration of the potential contaminants in the original stormwater sample. To elute the stormwater samples collected from January 2 and February 19, 2006, a total of 10 mL of 100% methanol was passed through the 1 g column in five, 2 mL aliquots, and collected into a test tube. For this treatment, the methanol elution sample was concentrated using nitrogen gas to reduce the sample volume such that toxicity associated with methanol, as Weston Solutions, Inc. 11
Toxicity Identification Evaluation of Chollas Creek Stormwater using Hyalella azteca Materials and Methods August 2006 indicated by the October TIE, would be reduced. Specifically, the methanol elution sample was placed on a warming plate, and nitrogen gas was blown into the headspace of the vial until the volume was reduced to approximately 2-4 mL. The exact concentration was determined and the methanol elution was added to clean control water at a concentration of 2.0 times the concentration of the potential contaminants in the original stormwater sample. 3.5.8 Graduated pH Tests Graduated pH tests are performed to see if the causative agents are pH-sensitive chemicals such as ammonia and aluminum. If changes in pH increase or decrease toxicity, this indicates that pH sensitive chemicals are present. Aliquots of stormwater (200 - 750 mL) and dilution water (750 mL) were elevated to test temperature and then adjusted to a pH of 6.8. These were used to prepare 200 mL dilutions of 50, 75 and 100 percent samples. The pH was adjusted to the target using 4 N HCl and 1.5 M NaOH. Treatment blanks for all TIEs were prepared identically to the stormwater samples described above, using dilution water instead of stormwater. 3.5.9 Piperonyl Butoxide (PBO) Tests PBO tests are performed to identify whether the causative agents are organophosphate pesticides or pyrethroids. Specifically, PBO blocks specific cytochrome P450 enzymes that are involved in metabolizing chemicals such as organophosphates to more toxic metabolites and chemicals such as pyrethroids to less toxic metabolites. Thus, if results from this test demonstrate increased toxicity in the stormwater sample, this is indicative of chemicals (e.g. pyrethroids) that are metabolized to less toxic forms by cytochrome P450 enzymes. In contrast, if the results demonstrate decreased toxicity in the stormwater samples, this is indicative of chemicals (e.g. malathion, organophosphates) that are metabolized to more toxic forms by cytochrome P450 enzymes. Two concentrations of PBO tests were used during each TIE. Concentrations of 0.025 and 0.050 mg/L were used in October, November, and January, whereas concentrations of 0.0007 mg/L and 0.025 mg/L were used in the February TIE. A stock solution of 2.5 mg PBO/L was prepared. PBO treatments were prepared by diluting the PBO stock solution to final concentrations of 0.0007, 0.025, and/or 0.050 mg/L, separately, in stormwater (50, 75 and 100 percent sample concentrations) and dilution water. The initial phase of TIE testing on Chollas Creek indicated that pyrethroids could be the cause of concern for toxicity. Because pyrethroids can adsorb to plastic (Wheelock et al., 2005), this test was repeated on November 15, 2005 using a new sample in both glass and plastic test chambers. In January, a reference toxicant test was also conducted concurrently with Phase I TIE tests to confirm that the concentrations of PBO used in the TIE treatments were at sublethal levels. PBO reference toxicant test used concentrations of 0.01, 0.05, 0.1, 0.5, and 1 mg/L. 3.5.10 Carboxyl Esterase Tests Carboxyl esterase treatments are performed to remove toxicity in samples that may contain pyrethroids. Carboxyl esterase is an enzyme that degrades type I and type II pyrethroids. Thus, recent studies have been performed in which carboxyl esterase has been used to reduce pyrethroid-associated toxicity to test organisms such as H. azteca (Wheelock et al., 2004). The carboxyl esterase test method used in the January and February TIEs was provided to Weston Weston Solutions, Inc. 12
Page 1 and 2: APPENDIX I Toxicity Identification
Page 3 and 4: Toxicity Identification Evaluation
Page 17: Toxicity Identification Evaluation

APPENDIX I Toxicity Identification Evaluation Reports for Chollas ...

Create successful ePaper yourself

Delete template?

Save as template?