Grantee Research Project Results
2006 Progress Report: Defining and Predicting PCB Fluxes and Their Ecological Effects in Stream and River Systems for Risk Characterizations
EPA Grant Number: R832213Title: Defining and Predicting PCB Fluxes and Their Ecological Effects in Stream and River Systems for Risk Characterizations
Investigators: Burton, Jr., G. Allen , Ren, Jianhong-Jennifer
Institution: Wright State University - Main Campus , Texas A & M University - Kingsville
EPA Project Officer: Hahn, Intaek
Project Period: March 1, 2005 through February 29, 2008 (Extended to February 28, 2009)
Project Period Covered by this Report: March 1, 2006 through February 29, 2007
Project Amount: $325,000
RFA: Greater Research Opportunities: Persistent, Bioaccumulative Chemicals (2004) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management , Safer Chemicals
Objective:
The primary objective of this research project is to develop and verify a predictive model and approach for assessing polychlorinated biphenyl (PCB) flux and biological effects in lotic environments. The hypotheses are that the fate of PCBs is dominated and can be characterized by sediment type and flow conditions and is directly related to biological exposure and in situ effects.
Progress Summary:
Overview
To accurately determine ecological risk and effective remedial actions, it is necessary to understand how ecosystem dynamics affect the linkage of exposure and ecological effects. In particular, a fundamental process that must be quantitatively understood is the flux of contaminants from sediments into overlying water and biota. This research demonstrates improved characterizations and then predicts the methodology by which solids-associated PCB exposures affect aquatic organisms. This investigation of PCB fluxes between sediments and overlying water characterizes the dominant processes of resuspension, deposition, pore-water convection, and sorption/desorption and relates the resulting exposures to biological effects. The investigation involves laboratory experiments, theoretical modeling, and field verification. Laboratory experiments are being conducted in stream recirculating flume (SRF) systems using a range of sediment types (low-to-high levels of gravel, sand, clay, and organic matter) and flow conditions. Chemicals in the SRF are loaded from above to simulate suspended solids loadings of PCB and from below to simulate groundwater upwellings and resuspension events. PCB-contaminated sediments used in the SRF will be obtained next year from three well-studied sites (Dick’s Creek, OH; Housatonic River, MA; Sheboygan River, WI), thus minimizing artifacts associated with pure compound spiking and equilibration concerns. Preliminary experiments are being conducted with dichlorodiphenyldichloroethylene (DDE) as a PCB surrogate. The SRF is being used to calibrate the model and allow for simultaneous characterizations of bioaccumulation and adverse biological effects. Test organisms are exposed to pore waters, surficial sediments, overlying waters and associated colloids, and suspended sediments within the recirculating systems and in the field. PCB bioaccumulation and effects are being measured with solid phase microextraction (SPME) and Tenax (both biomimetic tools), and with in the following organisms: Lumbriculus variegates (tissue concentrations), Daphnia magna (survival), Hyalella azteca (survival), and Chironomus tentans (survival and growth). These four U.S. Environmental Protection Agency (EPA) test organisms and the biomimetic tools will link effects characterization with exposure over a range of typical riverine conditions, thus allowing for multi-species, ecological risk characterizations. The scope of this project will not allow for a complete field validation of the model. A field verification of flux process importance and the in situ assessment approach will be conducted in Dick’s Creek. Because the model is based on descriptions of dominant processes over a range of conditions, it will be readily transferable to other surface waters and to high flow events with minimal extrapolation. The accompanying in situ assessment approach will allow for accurate calibration of the model and generation of site-specific bioavailability and accumulation factors. This will provide improved determinations of PCB risk from contaminated sediments, thus improving risk management decisionmaking.
Project Status During Year 2
Sorption kinetics of PCB Aroclor 1242 were evaluated using batch adsorption tests. Various techniques were evaluated to determine adsorption rates using sand and montmorillonite clay with various static-to-mixing techniques. In general, equilibrium was reached within 3 to 4 days.
The SRF at Texas A&M University at Kingsville (TAMUK) was used to conduct a flume run with polydispersed fine sediments. Analytical methods for determination of dichlorodiphenyldichloroethylene (DDE) and poly-chlorinated biphenyl (PCB) concentrations were developed and have been tested and the use of SPME evaluated. Since PCB is highly toxic, DDE, which is less toxic compared with PCB but has similar physicochemical and biological properties, was used at the beginning of the project as a substitute for PCB. In addition, subsurface sampling techniques have been explored to prepare the subsequent recirculating flume experiments. The modeling work was also initiated starting from the downwelling case.
The amount of DDE sorbed on the SPME fiber depends on the sorption time. Once the system of the fiber and water reaches equilibrium, an increase in sorption time does not increase the amount of DDE sorbed on the fiber. To determine the sorption time required to reach equilibrium, fiber sorption kinetics was evaluated for a DDE solution of 70 μg/L. No significant difference in the peak area was observed among the sorption times tested. Thus, 30 minutes of sorption provides sufficient time for the system to reach equilibrium. Since significant carryover was not observed during the fiber cleaning, 2 minutes of desorption time was sufficient to prevent carryover of DDE and incomplete desorption of DDE from the SPME fiber.
In the original proposal, in situ chambers were proposed to be used in the SRF experiments to examine the sediment and contaminant flux and their corresponding biological effects on test organisms. The proposed in situ chamber was designed mainly for field experiments. Since the SRF to be used in the laboratory study is on a much smaller scale compared with any field experiments, modification of the original in situ chamber is needed. The major modification of the current design of the in situ chamber was replacement of the part of solid plastic tube with netting. This minimizes the flow disturbance caused by the installation of the chambers in the streambed. Another modification needed was reduction of the chamber dimensions so that higher resolutions for subsurface sampling can be obtained and model predictions for subsurface contaminant distributions can be evaluated using the experimental results. The implementation of these modifications is currently being conducted at both the TAMUK and WSU campuses.
The first case being considered for modeling is the downwelling case as indicated in the project proposal. This case involves the transport of PCBs from the water column into the sediment bed. To predict the deterministic amount of the PCBs adsorbed on the bed sediments and in the pore water and prepare for analysis of risks associated with the PCBs for biota in river systems, the multiphase transport model developed by Ren and Packman (2004) was modified to output the contaminant distribution in the streambed.
Future Activities:
Short Term Work Plan and Expected Results
The short-term work plan for March 2007–February 2008 and expected results will include:
- Evaluation of other SPME coatings and Tenax for sampling within the SRFs and comparison of those levels to those of the in situ toxicity test species being evaluated.
- Completion of the development of additional calibration curves to ensure the desired reliability of the DDE concentration analysis in water samples (within the next three weeks).
- Conducting additional laboratory batch and column experiments to examine PCB and DDE adsorption and desorption kinetics, and obtaining input parameters to prepare subsequent model development.
- Completing modification of the in situ chamber during the summer.
- Starting SRF experiments for the downwelling case during the fall.
- Testing additional sediment types within the SRFs with in situ exposures during stressor additions.
- Application of the modified version of the multiphase transport model of Ren and Packman (2004) to the flume results obtained in the fall.
- Preparation of the first journal publication focusing on the downwelling case frpm December 2006.
- Initiation of studies for the upwelling case during the fall.
Reference:
Ren J, Packman AI. Multi-phase contaminant exchange between streams and streambeds: theory and numerical simulations. Environmental Science & Technology 2004;38(1):2901-2911.
Journal Articles:
No journal articles submitted with this report: View all 10 publications for this projectSupplemental Keywords:
sediment transport, bioassessment, sediment flux, PCB stream dynamics, sediment risk assessment,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Aquatic Ecosystem, Environmental Monitoring, Ecological Risk Assessment, bioassessment, risk assessment, aquatic sediments, aquatic ecosystems, PCB fluxes, riverine ecosystems, sediment dynamicsRelevant Websites:
http://www.wright.edu/~allen.burton Exit
Progress and Final Reports:
Original AbstractThe 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.