Publications (7)20.05 Total impact
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Article: It is time for changes in the analysis of whole effluent toxicity data.
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ABSTRACT: The whole effluent toxicity (WET) program in the United States, Canada, and other countries typically requires multi concentration testing of effluents. While multiconcentration testing of chemicals is desirable for regulatory and scientific reasons, we believe this requirement is not as efficient for evaluating effluent compliance in a WET program. The key regulatory question of concern is whether an effluent is toxic or not, which is best answered statistically using a hypothesis approach, not a point estimate approach. However, the traditional hypothesis approach currently recommended does not reward high within-test precision. This report describes the need for 3 specific changes in the analysis of WET compliance data that we believe would yield a more robust WET regulatory program: (1) restate the null hypothesis so that test power is associated with demonstrating that the effluent is not toxic, (2) use USEPA's Test of Significant Toxicity (based on the noninferiority approach) to identify unacceptable toxicity as well as acceptable effects with a high probability, and (3) evaluate only the test control and the critical concentration of concern (e.g., instream waste concentration). We demonstrate that instituting these 3 changes would provide: Positive incentives for permittees to produce high-quality WET data, a transparent analysis approach in which the permittee could have greater control over regulatory decisions based on test results, and potentially a less expensive testing program because fewer effluent concentrations need to be examined within a test. As a result, WET test frequency could be increased for the same cost as current testing programs while providing greater representativeness of effluent quality.Integrated Environmental Assessment and Management 09/2011; 8(2):351-8. -
Article: Pesticide and toxicity reduction using an integrated vegetated treatment system.
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ABSTRACT: The California, USA, central coast is one of the most productive agricultural areas in the world, and numerous stakeholders are working there to implement conservation practices to reduce contaminated runoff. Practices include vegetated treatment systems (VTS) designed to promote contaminant reduction and breakdown. The current study evaluated the effectiveness of a vegetated drainage ditch incorporating a sedimentation basin, a vegetated section, and a Landguard organophosphate-A (OP-A) enzyme dosing system. The VTS was constructed on a working farm and was designed to remove organophosphate and pyrethroid pesticides, the primary pesticides causing toxicity in Salinas Valley watersheds. The present study was conducted during five separate irrigation events on tailwater runoff containing mixtures of pesticides and suspended sediments. Water samples were collected at four stations within the system, and these were subjected to chemical analyses and tested for toxicity to Ceriodaphnia dubia. All inflow samples were highly toxic to C. dubia, and this was largely because of diazinon. Treatment of diazinon-contaminated runoff was only partially effective using aquatic vegetation. All diazinon remaining after vegetated treatment was effectively removed after treatment with the Landguard OP-A enzyme. Chemical analysis of the VTS water samples showed that pyrethroid and organochlorine pesticide concentrations in water were greatly reduced in the sedimentation section of the ditch, and these pesticides were further reduced in the vegetated section of the ditch. The overall conclusion from these analyses is that the VTS was effective at reducing the more hydrophobic organochlorine and pyrethroid pesticides from water. The water-soluble pesticide diazinon was not sufficiently removed during the VTS residence times observed in this study; however, residual diazinon was effectively removed using Landguard OP-A.Environmental Toxicology and Chemistry 02/2011; 30(5):1036-43. · 2.81 Impact Factor -
Article: A role for analytical chemistry in advancing our understanding of the occurrence, fate, and effects of Corexit oil dispersants.
Environmental Science & Technology 08/2010; 44(16):6016-8. · 4.80 Impact Factor -
Article: Comparison of methods for evaluating acute and chronic toxicity in marine sediments.
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ABSTRACT: Sublethal test methods are being used with increasing frequency to measure sediment toxicity, but little is known about the relative sensitivity of these tests compared to the more commonly used acute tests. The present study was conducted to compare the sensitivity of several acute and sublethal methods and to investigate their correlations with sediment chemistry and benthic community condition. Six sublethal methods (amphipod: Leptocheirus plumulosus survival, growth, and reproduction; polychaete: Neanthes arenaceodentata survival and growth; benthic copepod: Amphiascus tenuiremis life cycle; seed clam: Mercenaria mercenaria growth; oyster: Crassostrea virginica lysosome destabilization; and sediment-water interface testing with mussel embryos, Mytilus galloprovincialis) and two acute methods (amphipod survival with Eohaustorius estuarius and L. plumulosus) were used to test split sediment samples from stations in California. The test with Amphiascus proved to be the most sensitive sublethal test and the most sensitive overall, identifying 90% of the stations as toxic. The Leptocheirus 10-d test was the most sensitive of the acute tests, identifying 60% of the stations as toxic. In general, the sublethal tests were not more sensitive to sediments than the acute tests, with the sublethal tests finding an average of 35% of the stations to be toxic while the acute found 44%. Of the sublethal tests, only the Amphiascus endpoints and Neanthes growth significantly (p <or= 0.05) correlated with sediment chemical concentrations. Poor correspondence occurred between the toxicity endpoints and the indicators of benthic community condition. Differences in test characteristics such as mode of exposure, species-specific contaminant sensitivity, changes in contaminant bioavailability, and influence of noncontaminant stressors on the benthos may have been responsible for variation in response among the tests and low correspondence with benthic community condition. The influence of these factors cannot be easily predicted, underscoring the need to use multiple toxicity methods, in combination with other lines of evidence, to provide an accurate and confident assessment of sediment toxicity.Environmental Toxicology and Chemistry 04/2008; 27(4):933-44. · 2.81 Impact Factor -
Article: Use of toxicity identification evaluations to determine the pesticide mitigation effectiveness of on-farm vegetated treatment systems.
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ABSTRACT: Evidence of ecological impacts from pesticide runoff has prompted installation of vegetated treatment systems (VTS) along the central coast of California, USA. During five surveys of two on-farm VTS ponds, 88% of inlet and outlet water samples were toxic to Ceriodaphnia dubia. Toxicity identification evaluations (TIEs) indicated water toxicity was caused by diazinon at VTS-1, and chlorpyrifos at VTS-2. Diazinon levels in VTS-1 were variable, but high pulse inflow concentrations were reduced through dilution. At VTS-2, chlorpyrifos concentrations averaged 52% lower at the VTS outlet than at the inlet. Water concentrations of most other pesticides averaged 20-90% lower at VTS outlets. All VTS sediment samples were toxic to amphipods (Hyalella azteca). Sediment TIEs indicated toxicity was caused by cypermethrin and lambda-cyhalothrin at VTS-1, and chlorpyrifos and permethrin at VTS-2. As with water, sediment concentrations were lower at VTS outlets, indicating substantial reductions in farm runoff pesticide concentrations.Environmental pollution (Barking, Essex: 1987) 04/2008; 156(2):348-58. · 3.43 Impact Factor -
Article: Comparison of Methods for Evaluating Acute and Chronic Toxicity in Marine Sediments.
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ABSTRACT: Sublethal test methods are being used with increasing frequency to measure sediment toxicity, but little is known about the relative sensitivity of these tests compared to the more commonly used acute tests. A study was conducted to compare the sensitivity of several acute and sublethal methods and investigate their correlations with sediment chemistry and benthic community condition. Six sublethal methods (amphipod: Leptocheirus plumulosus survival, growth and reproduction; polychaete: Neanthes arenaceodentata survival and growth; benthic copepod: Amphiascus tenuiremis, life-cycle; seed clam: Mercenaria mercenaria growth; oyster: Crassostrea virginica lysosome destabilization; and sediment-water interface testing with mussel embryos, Mytilus galloprovincialis) and two acute methods (amphipod survival with Eohaustorius estuarius and Leptocheirus plumulosus) were used to test split sediment samples from stations in California. The test with Amphiascus, proved to be the most sensitive sublethal test and the most sensitive overall. The Leptocheirus 10-day test was the most sensitive of the acute tests. In general, the sublethal tests were not more sensitive to sediments than the acute tests. Of the sublethal tests, only the Amphiascus endpoints and Neanthes growth correlated with sediment chemistry. There was poor correspondence between the toxicity endpoints and indicators of benthic community condition. Differences in test characteristics such as mode of exposure, species-specific contaminant sensitivity, changes in contaminant bioavailability, and the influence of noncontaminant stressors on the benthos may have been responsible for variation in response among the tests and low correspondence with benthic community condition. The influence of these factors cannot be easily predicted, underscoring the need to use multiple toxicity methods in combination with other lines of evidence to provide an accurate and confident assessment of sediment toxicity.Environmental Toxicology and Chemistry 01/2008; · 2.81 Impact Factor -
Article: Patterns and trends in sediment toxicity in the San Francisco Estuary.
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ABSTRACT: Widespread sediment toxicity has been documented throughout the San Francisco Estuary since the mid-1980s. Studies conducted in the early 1990s as part of the Bay Protection and Toxic Cleanup Program (BPTCP), and more recently as part of the Regional Monitoring Program (RMP) have continued to find sediment toxicity in the Estuary. Results of these studies have shown a number of sediment toxic hotspots located at selected sites in the margins of the Estuary. Recent RMP monitoring has indicated that the magnitude and frequency of sediment toxicity is greater in the winter wet season than in the summer dry season, which suggests stormwater inputs are associated with sediment toxicity. Additionally, spatial trends in sediment toxicity data indicate that toxic sediments are associated with inputs from urban creeks surrounding the Estuary, and from Central Valley rivers entering the northern Estuary via the Delta. Sediment toxicity has been correlated with a number of contaminants, including selected metals, PAHs and organochlorine pesticides. While toxicity identification evaluations (TIEs) suggest that metals are the primary cause of sediment toxicity to bivalve embryos; TIEs conducted with amphipods have been inconclusive.Environmental Research 10/2007; 105(1):145-55. · 3.40 Impact Factor
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2007–2011
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University of California, Davis
- Department of Environmental Toxicology
Davis, CA, USA
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