Grantee Research Project Results
Final Report: Center for the Study of Metals in the Environment
EPA Grant Number: R829500Center: Center for the Study of Metals in the Environment
Center Director: Allen, Herbert E.
Title: Center for the Study of Metals in the Environment
Investigators: Allen, Herbert E.
Institution: University of Delaware
EPA Project Officer: Hahn, Intaek
Project Period: April 1, 2002 through March 31, 2005
RFA: Targeted Research Center (2006) Recipients Lists
Research Category: Targeted Research , Hazardous Waste/Remediation
Objective:
The Center for the Study of Metals in the Environment is a multi-investigator program of scientists and engineers working to further the understanding of processes affecting the fate and effects of metals in aquatic and terrestrial ecosystems. Significant gaps in the ability to predict the fare and effects of metals in both aquatic and terrestrial systems continue to hamper appropriate risk assessments and cost-effective risk management. In these situations, decisions include many assumptions and the application of safety factors. The focus of the Center is to develop appropriate information so that regulatory decisions will be based on sound scientific principles. Much of the existing methodology for hazard identification and for risk assessment is based on experience with persistent organic pollutants such as DDT and PCBs. The large differences in environmental behavior and potential for toxicity between organic compounds and metals are not incorporated into these methods. Assessment methodology is currently focused on the extent to which chemicals exhibit PBT (persistent, bioaccumulative, and toxic) characteristics. All three characteristics are important aspects of the assessment of risk, but their applicability to metals and the evaluation of metals data for these criteria differ from organic compounds.
As a replacement for the current methods for evaluating the effect of metals in the environment, the Center is developing a model for the behavior of metal compounds that can be used as a tool in the hazard assessment of metals and metal compounds. This model will include the physical and chemical mechanisms that control the fate and resulting bioavailability of metals discharged to natural waters. In particular the transformations that affect metal fate and toxicity will be included. It is anticipated that it would be similar to the Unit World models, for example EUSES that are used for evaluating PBT organic chemicals. Metal behavior in watersheds, streams, lakes and reservoirs will be considered. The focus of the research efforts is to provide the information necessary to formulate and parameterize the model.
The Center funded four research projects, including that for the development of the Unit World Model. In all cases, these projects have been highly successful and have lead to the development of a number of publications. This report presents important papers that have been developed from these projects and which contain the key results of the research.
Unit World Model for Metals in Aquatic Environments
Introduction
There is a clear need for methods that can be used for evaluating the environmental hazard associated with the release of metals and metal compounds to the environment (Adams et al., 2000). The purpose of the Unit World Model (UWM) is to provide such a framework. The idea for a UWM comes from the fugacity and regional models developed for organic chemicals (Mackay 1979, 1991, Mackay et al. 1992). Models of this sort have previously been applied in various forms to pesticides (USEPA, 1986a) and industrial organic chemicals (European Commission, 1996). The UWM for metals is structured such that it can be used to estimate both the exposure and effects of metal and metal compounds. It incorporates the necessary metal specific processes that differentiate the behavior of metals from organic chemicals.
Approach
The Unit World Model is designed to represent the major processes that determine the fate and transport of metals in the aquatic environment. In the water column these processes include solubilization for particulate metal compounds, speciation among inorganic and organic dissolved ligands, and partitioning to suspended particles. The WHAM series of aqueous speciation models (Tipping, 1994) have been extensively calibrated and are well suited for incorporation in the UWM. A metal particle sorption model (SCAMP) has also recently become available (Lofts and Tipping 1998). Although not as well calibrated, it provides a useful starting point.
The sorption of metals to water column pat1iculate matter leads to the transfer of the metal to the bottom sediments. Hence, sediments are the ultimate repositories of metals in aquatic settings. A number of sediment models have been developed that successfully predict levels of sulfide (A VS-Acid Volatile Sulfide) and partitioned metal (SEM) in sediments and resulting fluxes of dissolved metal from the sediments to the overlying water column (Di Toro et al., 1996; Carbonaro, 1999; Di Toro et al., 2001). Therefore the frameworks exist for at least most of the processes, in various stages of development, for the water column and sediment compartments.
Effects Concentration and Bioavailability
In addition to the exposure concentrations in the water column and sediment, it is necessary to predict the effects to be expected. The traditional method is to use an effects concentration for the water column and the sediment. For the water column the EPA Water Quality Criteria (Stephan et al., 1985, USEPA 1986b, 1996) or the PNEC (Predicted No Effect Concentration) derived following the EU Technical Guidelines (EU, 1996) are possibilities. However, these criteria make only limited bioavailability corrections (for water hardness only). This is a much more critical issue for metals than for organic chemicals. To remedy this situation, the Biotic Ligand Model (BLM) has recently been developed (USEPA, 1999, 2000; Di Toro, et al., 2001; Paquin, et al., 2002). It incorporates the WHAM speciation model and in addition models the competitive metal binding at the toxic site of action (the Biotic Ligand). BLMs are currently available for copper and silver (Di Toro, et al., 2001; Santore, et al., 2001), zinc (Santore, et al., 2002) and are under development for cadmium, nickel and lead.
The situation in the sediment is similar. There are guideline values that do not take bioavailability into account-the sediment PNEC-or which are empirical and therefore are not predictive of individual metal toxicity (e.g., Long and Morgan, 1991; Field, et al., 2002).
For metals, EPA has developed sediment quality guidelines that are causally related to metal effects and do take bioavailability into account. They are based on the relative magnitudes of acid volatile sulfide AVS and simultaneously extractable metal SEM, and organic carbon (Di Toro, et al., 1990, 1992; Ankley, et al., 1993, 1996; USEPA, 2000).
Summary/Accomplishments (Outputs/Outcomes):
Notable Accomplishments of Research Projects
- Development of Fate and Transport Models for Exposure Assessment: Application to Streams and Rivers
Principal Investigator: Dominic Di Toro
We have developed a Unit World Model that describes the fate of metals in rivers and lakes. To allow the model to be used for the large number of metals for which there are few to no field data, new model parameters have been developed that permit the prediction of metal partitioning to particles in the overlying water and sediments. The model is fully integrated with our model for toxicity of metals to aquatic life. The Unit World Model has been used to prioritize the need for research and potential regulation for a suite of metals under consideration for regulation in Europe. It is part of the EPA metals action plan. Two manuscripts have been developed based on this research. These are:
Rader KJ, Warnken KW, Santschi PH, Di Toro DM. Modeling the Solid-Solution Partitioning of Metals in the Trinity River using WHAM6.
Rader KJ, Butler B, Carbonaro RF, Farley KJ, Di Toro DM. A Probabilistic Unit World Model for Metal Toxicity Assessment in Rivers
Three other manuscripts are anticipated in the near future.
- Refinement and Application of an Electroanalytical Method for the Determination of the Extent and Strength of Metal Complexation in Natural Waters.
Principal Investigator: George W. Luther, III
To describe quantitatively the impacts of trace metals as nutrients and toxicants in aquatic environments, one must be able to accurately predict the extent and nature of aquatic complexation Research involving reference scales developed using pseudopolarography has provided evidence of very strong metal complexes at very low metal levels in 'natural water bodies. The desirable characteristics of this method are that determination of complex stability is independent of the ligand concentration and samples can be analyzed with little matrix modification. Recent work has expounded the theoretical underpinnings of this method and discussed some of the limitations of its applicability, and, is so doing, provided an essential foundation for its continued use as an analytical tool. One paper has been published (Tsang JYJ, Rozan TF, Hsu-Kim H, Mullaugh KM, Luther III GW. Pseudopolarographic Determination of Cd2 + Complexation in Freshwater), and a second is to be submitted in the near future.
- Metal Sequestration in Soils
Principal Investigator: Donald L. Sparks
We have developed new understanding of how metals become immobilized in soils. This has been a two-pronged approach in our work. We have applied advanced spectroscopic methods using the accelerators at Brookhaven, Argonne, and Lawrence-Berkeley National Laboratories to identify chemical products formed when metals are added to soils. We have studied the kinetics of metal reactions with soils and used chemical models to understand how metals become immobilized. These results aid in understanding impacts of metals and in the development of remediation measures. One paper has been published Shi Z, Di Toro DM, Allen HE, Sparks DL. A WHAM-based Kinetics Model for Zn Adsorption and Desorption to Soils), and a second is to be submitted in the near future (Shi Z, Peltier EF, Sparks DL. Kinetics of Zn Desorption from Soils: A Modeling and Spectroscopic Study).
- Further Development of a Terrestrial Biotic Ligand Model (TBLM)
Principal Investigator: Herbert E. Allen
We have developed a means to predict the ecotoxicity of metals in soils. Methods used presently can be either under or overprotective. The new method addresses the issue of bioavailability directly. This is a terrestrial version of the biotic ligand model that we had previously adapted for prediction of toxicity of metals in water and which EPA has used for the Water Quality Criteria (WQC) for copper. Our model uses WHAM VI to predict the partitioning of metals in noncalcareous soils. The toxicity of the free metal ion in soil solution is modified by competing cations (H+, Ca2+, and Mg2+) at the biotic ligand of soil organisms. In this project we have developed species sensitivity relationships that account for soil chemistry and we have independently developed biotic ligand constants for the effect of nickel on barley root elongation. Two manuscripts (Thakali S, Allen HE, Di Toro DM. A Terrestrial Biotic Ligand Model. 3. Application to Soil Metal Criteria and Species Sensitivity Distributions; and Lin Y, Allen HE, Di Toro DM. A Terrestrial Biotic Ligand Model. 4. Validation of Ni Toxicity to Barley Root Elongation) are near completion and two further manuscripts will be prepared on this work.
References:
Journal Articles: 4 Displayed | Download in RIS Format
Other center views: | All 4 publications | 4 publications in selected types | All 4 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Field LJ, Macdonald DD, Norton SB, Ingersoll CG, Severn CG, Smorong D, Lindskoog R. Predicting amphipod toxicity from sediment chemistry using logistic regression models. Environmental Toxicology and Chemistry 2002;21(9):1993-2005. |
R829500 (2002) R829500C001 (2002) R829500C002 (2002) R829500C003 (2002) R829500C004 (2002) R829500C005 (2002) R829500C006 (2002) R829500C007 (2002) |
|
|
Paquin PR, Gorsuch JW, Apte S, Batley GE, Bowles KC, Campbell PGC, Delos CG, Di Toro DM, Dwyer RL, Galvez F, Gensemer RW, Goss GG, Hogstrand C, Janssen CR, McGeer JC, Naddy RB, Playle RC, Santore RC, Schneider U, Stubblefield WA, Wood CM, Wu KB. The biotic ligand model: a historical overview. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 2002;133(1-2):3-35. |
R829500 (2002) R829500C001 (2002) R829500C002 (2002) R829500C003 (2002) R829500C004 (2002) R829500C005 (2002) R829500C006 (2002) R829500C007 (2002) |
Exit Exit |
|
Santore RC, Mathew R, Paquin PR, DiToro DM. Application of the biotic ligand model to predicting zinc toxicity to rainbow trout, fathead minnow, and Daphnia magna. Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 2002;133(1-2):271-285. |
R829500 (2002) R829500C001 (2002) R829500C002 (2002) R829500C003 (2002) R829500C004 (2002) R829500C005 (2002) R829500C006 (2002) R829500C007 (2002) |
Exit Exit |
|
Smith K, Rainville J, Lesher E, Diedrich D, McKnight D, Sofield R. Fractionation of Fulvic Acid by Iron and Aluminum Oxides-Influence on Copper Toxicity to Ceriodaphnia dubia. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014;48(20):11934-11943. |
R829500 (Final) R829515 (Final) |
Exit Exit |
Supplemental Keywords:
International Cooperation, Scientific Discipline, Waste, RFA, Ecological Risk Assessment, Hazardous Waste, Hazardous, Ecology and Ecosystems, Geochemistry, remediation, fate and transport , extraction of metals, bioaccumulation, PCB, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, Geochemistry, Hazardous Waste, Ecological Risk Assessment, Ecology and Ecosystems, Hazardous, fate and transport , PCB, remediation, DDT, extraction of metalsProgress and Final Reports:
Original Abstract Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R829500C001 Role of Dietary Exposure for Bioaccumulation and Toxicity of Metals in Aquatic Ecosystems Affected by Mining
R829500C002 The Role of Organic Matter and Metal Oxides in the Retention of Trace Metals by Soil and Suspended Particles
R829500C003 Developing a Model to Predict the Persistence of Metals in Aquatic Environments
R829500C004 Effects of Dietary Metal Exposure on Fish and Aquatic Invertebrates
R829500C005 Aquatic Toxicity and Exposure Assessment
R829500C006 Development of a Model to Predict the Bioavailability of Metals to Soil Invertebrates
R829500C007 Bioaccumulation and Toxicity of Dietborne Particulate Metals to Benthic Invertebrates
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.