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Robert C. Santore

Publications and source records attributed to Robert C. Santore.

5 recordsLinked to original sources
USGS2021

Modeling the bioavailability of nickel and zinc to Ceriodaphnia dubia and Neocloeon triangulifer in toxicity tests with Natural Waters

We studied biotic ligand model (BLM) predictions of toxicity of nickel (Ni) and zinc (Zn) in natural waters from Illinois and Minnesota USA which had combinations of pH, hardness, and dissolved organic carbon (DOC) more extreme than 99.7% of waters in a nationwide database. We conducted 7-d chronic tests with Ceriodaphnia dubia, and 96-hr acute test and 14-d chronic tests with Neocloeon triangulifer, and estimated LC50s and EC20s for both species. Toxicity of Ni and Zn to both species differed among test waters by factors from 8 (Zn tests with C. dubia ) to 35 (Zn tests with N. triangulifer ). For both species and metals, tests with Minnesota waters (low pH and hardness, high DOC) showed lower toxicity than Illinois waters (high pH, high hardness, low DOC). Recalibration of the Ni BLM to be more responsive to pH-related changes improved predictions of Ni toxicity, especially for C. dubia . We compared several input data scenarios for the Zn BLM, which generally had minor effects on Model Performance Scores (MPS). A scenario that included inputs of modeled dissolved inorganic carbon and measured Al and Fe(III) produced highest MPS values for tests with both C. dubia and N. triangulifer . Overall, the BLM framework successfully modeled variation in toxicity for both Zn and Ni across wide ranges of water chemistry in tests with both standard and novel test organisms.

Illinois, Minnesota↗
USGS2020

Metal bioavailability models: Current status, lessons learned, considerations for regulatory use, and the path forward

Since the early 2000s, biotic ligand models and related constructs have been a dominant paradigm for risk assessment of aqueous metals in the environment. We critically review 1) the evidence for the mechanistic approach underlying metal bioavailability models; 2) considerations for the use and refinement of bioavailability-based toxicity models; 3) considerations for the incorporation of metal bioavailability models into environmental quality standards; and 4) some consensus recommendations for developing or applying metal bioavailability models. We note that models developed to date have been particularly challenged to accurately incorporate pH effects because they are unique with multiple possible mechanisms. As such, we doubt it is ever appropriate to lump algae/plant and animal bioavailability models; however, it is often reasonable to lump bioavailability models for animals, although aquatic insects may be an exception. Other recommendations include that data generated for model development should consider equilibrium conditions in exposure designs, including food items in combined waterborne–dietary matched chronic exposures. Some potentially important toxicity-modifying factors are currently not represented in bioavailability models and have received insufficient attention in toxicity testing. Temperature is probably of foremost importance; phosphate is likely important in plant and algae models. Acclimation may result in predictions that err on the side of protection. Striking a balance between comprehensive, mechanistically sound models and simplified approaches is a challenge. If empirical bioavailability tools such as multiple-linear regression models and look-up tables are employed in criteria, they should always be informed qualitatively and quantitatively by mechanistic models. If bioavailability models are to be used in environmental regulation, ongoing support and availability for use of the models in the public domain are essential.

Environmental Toxicology and Chemistry↗
USGS2014

Metal Mixture Modeling Evaluation project: 2. Comparison of four modeling approaches

As part of the Metal Mixture Modeling Evaluation (MMME) project, models were developed by the National Institute of Advanced Industrial Science and Technology (Japan), the U.S. Geological Survey (USA), HDR⎪HydroQual, Inc. (USA), and the Centre for Ecology and Hydrology (UK) to address the effects of metal mixtures on biological responses of aquatic organisms. A comparison of the 4 models, as they were presented at the MMME Workshop in Brussels, Belgium (May 2012), is provided herein. Overall, the models were found to be similar in structure (free ion activities computed by WHAM; specific or non-specific binding of metals/cations in or on the organism; specification of metal potency factors and/or toxicity response functions to relate metal accumulation to biological response). Major differences in modeling approaches are attributed to various modeling assumptions (e.g., single versus multiple types of binding site on the organism) and specific calibration strategies that affected the selection of model parameters. The models provided a reasonable description of additive (or nearly additive) toxicity for a number of individual toxicity test results. Less-than-additive toxicity was more difficult to describe with the available models. Because of limitations in the available datasets and the strong inter-relationships among the model parameters (log KM values, potency factors, toxicity response parameters), further evaluation of specific model assumptions and calibration strategies is needed.

Environmental Toxicology and Chemistry↗
USGS2011

Influence of dissolved organic carbon on toxicity of copper to a unionid mussel ( Villosa iris ) and a cladoceran ( Ceriodaphnia dubia ) in acute and chronic water exposures

Acute and chronic toxicity of copper (Cu) to a unionid mussel ( Villosa iris ) and a cladoceran ( Ceriodaphnia dubia ) were determined in water exposures at four concentrations of dissolved organic carbon (DOC; nominally 0.5, 2.5, 5, and 10 mg/L as carbon [C]). Test waters with DOC concentrations of 2.5 to 10 mg C/L were prepared by mixing a concentrate of natural organic matter (Suwannee River, GA, USA) in diluted well water (hardness 100 mg/L as CaCO 3 , pH 8.3, DOC 0.5 mg C/L). Acute median effect concentrations (EC50s) for dissolved Cu increased approximately fivefold (15–72 μg Cu/L) for mussel survival in 4-d exposures and increased about 11-fold (25–267 μg Cu/L) for cladoceran survival in 2-d exposures across DOC concentrations from 0.5 to 10 mg C/L. Similarly, chronic 20% effect concentrations (EC20s) for the mussel in 28-d exposures increased about fivefold (13–61 μg Cu/L for survival; 8.8–38 μg Cu/L for biomass), and the EC20s for the cladoceran in 7-d exposures increased approximately 17-fold (13–215 μg Cu/L) for survival or approximately fourfold (12–42 μg Cu/L) for reproduction across DOC concentrations from 0.5 to 10 mg C/L. The acute and chronic values for the mussel were less than or approximately equal to the values for the cladoceran. Predictions from the biotic ligand model (BLM) used to derive the U.S. Environmental Protection Agency's ambient water quality criteria (AWQC) for Cu explained more than 90% of the variation in the acute and chronic endpoints for the two species, with the exception of the EC20 for cladoceran reproduction (only 46% of variation explained). The BLM-normalized acute EC50s and chronic EC20s for the mussel and BLM-normalized chronic EC20s for the cladoceran in waters with DOC concentrations of 2.5 to 10 mg C/L were equal to or less than the final acute value and final chronic value in the BLM-based AWQC for Cu, respectively, indicating that the Cu AWQC might not adequately protect the mussel from acute and chronic exposure, and the cladoceran from chronic exposure.

Environmental Toxicology and Chemistry↗