Grantee Research Project Results
2007 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, 2007 through February 29, 2008
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 biphenyls (PCB) flux and biological effects in lotic environments. The hypotheses are that the fate of PCBs are dominated and can be characterized by sediment type and flow conditions and directly relates 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 is demonstrating improved characterizations and the prediction of how solids-associated PCB exposures affect aquatic organisms. This investigation of PCB fluxes between sediments and overlying water is characterizing the dominant processes of resuspension, deposition, pore-water convection, and sorption/desorption and relates the resulting exposures to biological effects. This investigation involves laboratory experiments, theoretical modeling, and field verification. Laboratory experiments are bein conducted in stream recirculating flume systems (SRF) 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 this summer from two well-studied sites (i.e., Dick’s Creek, OH; Grasse River, NY), thus minimizing artifacts associated with pure compound spiking and equilibration concerns. Most experiments are being conducted with dichlorodiphenyldichloroethylene (DDE), as a PCB surrogate, for health safety reasons. 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 is being measured with solid phase microextraction (SPME) (replacing Tenax), and with the following organisms: Lumbriculus variegates, Daphnia magna, Hyalella azteca, Chironomus tentans, and Pimephales promelas. These five U.S. Environmental Protection Agency (EPA) test organisms and the biomimetic tool 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, however. 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 calibration. 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 decision-making.
Project Status During Year 3:
One new Post-doctoral Research Associate and an MS student were placed on the project. During Years 2 and 3, progress was slowed at WSU due to the loss of the two Ph.D students assigned to this project in Year 2. In July 2007, new Post-doctoral Research Associate, Dr. Keith Taulbee (from the USEPA ORD NMRL Cincinnati) was hired to help lead this project and a new MS student began her thesis research on this and another sediment flux project. Due to lack of EPA funds, these personnel are being supported by other grants and contracts. Two TAMUK graduate students, Celina Camarena and Doris Otero, continued their work on the project. Celina focused on laboratory study of PCB fluxes and Doris focused on the development of process-based models for predicting PCB flux and the corresponding biological effects. Both students worked on interpretation of experimental results using the models developed. Celina has been supported by the NSF funded Center for Research Excellence in Science and Technology (CREST)-Research on Environmental Sustainability of Semi-Arid Coastal Areas (RESSACA). Doris started to work on this project in September 2007 and has been supported by this STAR grant. In addition, one visiting research scholar, Dr. Tong Zheng, started his work on May 1st, 2008 on modeling of the resuspension of contaminated fine sediments. Dr. Zheng will work at TAMUK for one year.
Three flumes were obtained and put on-line at WSU during Year 3, requiring a significant amount of effort and resources (again paid by other grants and contracts). Initial calibration of the flumes with sands and clays and in situ caged organism deployments was accomplished to assure stable reference-control conditions exist. Toxicity testing was conducted on the TAMUK laboratory waters being used for their sediment flumes. Surprisingly, it was found that the TAMUK water source was toxic and could not be used for joint experiments with WSU personnel on-site at TAMUK. Extensive retesting was conducted varying the water collection method and addition of reconstituted salts to try and remove the toxicity. This testing is nearing completion and has again delayed some of the biological testing.
Both laboratory experiments and numerical modeling have been conduced at TAMUK. As proposed in the original proposal, the study has focused on both downwelling and upwelling cases. Up to date, major research results for the downwelling case have been obtained and details on these results are presented below. The numerical modeling for upwelling case started in April 2007, but no major results to be reported here due to project delay caused by the leave of one of the previous graduate students (Sivacharan Peddireddy) due to personal issues. Sivacharan was working on the numerical modeling work proposed. After he left, it took us three months to search for a new student to continue the modeling work. Doris joined us in September 2007 and it took us a few months for her to get sufficient training on the modeling work. Thus, the modeling work for the upwelling case is still ongoing. The preparation for the upwelling experiment work was conducted in spring of 2008, and the experimental work is also ongoing now at TAMUK.
The downwelling case study was conducted by investigating the transport behavior of p,p’-DDE between streamwater and streambed in the presence of naturally occurring fine sediments such as kaolinite clay particles. The experiments were conducted using a recirculating flume. The solid-phase microextraction (SPME) method, a modern and efficient extraction technique, combined with gas chromatography was used to determine the concentrations of DDE. Five flume runs have been performed. The first flume run was a control run which consisted of only DI water and p,p’-DDE to examine p,p’-DDE mass loss due to the flume materials. The second flume run performed was to examine the stream-subsurface exchange of p,p’-DDE. This flume run consisted of DI water, cleaned Ottawa #12 Flint silica sand (F12) (bed sediment), and p,p’-DDE. The third, fourth, and fifth flume runs were conducted to investigate the effects of fine sediments on p,p’-DDE contaminant transport. These flume runs consisted of DI water, cleaned F12 silica sand (bed sediment), p,p’-DDE, and kaolinite particles or natural fine sediments. The kaolinite particles used had an average diameter of 0.22 μm, which was measured using a Brookhaven Instrument Corporation (BIC) ZetaPALS Multi-Angle particle size analyzer. The natural fine sediments were collected from the Rio Grande.
The multiphase exchange model for the downwelling case was developed by considering the kinetic adsorption/desorption of DDE to bed sediments and suspended sediments, particle deposition and hydrodynamic exchange. The two-site equilibrium/kinetic model proposed by Van Genuchten and Wagenet (1989) and verified using the batch experiments conducted in this study was applied to model the kinetic interaction of DDE with sediments. The developed model is being applied to interpret the flume experiment results.
Figure 1 shows the batch experiment results for the interaction of DDE with silica sand. A fast sorption of p,p’-DDE to silica sand within the first 3-5 days followed by a slow equilibrating process was observed. The DDE sorption to silica sand was modeled using the kinetic sorption/desorption model with fitting parameters of f = 0.92 and = 0.34 day-1, where f is the fraction of equilibrium sites and is the mass transfer rate.
Figure 2 shows the isotherm data collected from the batch experiments after 54 days. The sorption behavior of p,p’-DDE can be described using the Freundlich Isotherm (nonlinear case) as compared to the Linear Isotherm with fitting parameters of kd = 0.071 L/g and ns = 1.88, where kd is the empirical distribution coefficient and ns is nonlinear Freundlich coefficient.
Figure 1. Batch experiment results for the sorption/desorption of DDE with silica sand. C0 is the initial DDE concentration in each batch experiment.
Figure 2. Batch sorption isotherm data collected after 54 days.
Figure 3 shows the comparison of flume results obtained from flume runs #1 and #2 and model simulations for flume run #2. Results are presented as the normalized in-stream concentrations (C* = C/C0) of dissolved p,p’-DDE plotted as a function of dimensionless time. Results from flume run #1 indicate a significant loss of DDE mass due to the flume channel, which needs to be considered in model applications. Results from flume run #2 show that the net bed exchange of p,p’-DDE with clean F12 silica sand in the absence of suspended fine sediments is insignificant. The nonlinear Freundlich coefficient, ns, obtained from the batch experiments (Figure 2) did not accurately predict the DDE exchange results as expected due to the DDE mass loss in the channel although a fitted ns = 1.22 is better to represent Flume Run #2 results.
Figure 3. Comparison of flume results obtained from flume runs #1 and #2 and modeling simulations for flume run #2.
Figure 4 shows the comparison of the dissolved p,p’-DDE exchange results obtained from flume runs #2-4. The significant effect of the presence of kaolinite colloidal particles on DDE exchange is clearly demonstrated. These results indicate that fine sediments can significantly affect the stream-subsurface exchange of p,p’-DDE and that additional contaminant immobilization in the streambed can occur due to the deposition of fine sediments in the streambed sediments.
Figure 4.Comparison of dissolved p,p’-DDE exchange results obtained from flume runs #2-4.
Figure 5 shows the effect of input parameters on simulating the exchange of DDE between stream and streambed under the experimental conditions of flume Run #2. Figure 5A illustrates that increases in f, the fraction of equilibrium sites, shows no significant difference in the results of p,p’-DDE retention in the sediment. Figure 5B show that increases in kd, the distribution coefficient, result in an increase of p,p’-DDE retention in the sediment. Figure 5C demonstrates that increases in ns, the nonlinear Freundlich coefficient, result in a decrease of p,p’-DDE retention in the sediment. Thus, under given flume experiment conditions, the ns parameter is the most sensitive parameter.
Figure 5. Effect of input parameters on simulating exchange of DDE between stream and streambed under the experimental conditions of flume Run #2. The additional simulation parameters used are A) Distribution coefficient, kd, 0.071 L/g; Freundlich nonlinear coefficient, ns, 1.88; Initial conc., C0, 0.061 mg/L; Mass transfer rate, α, 0.000236 1/day; B) Freundlich nonlinear coefficient, ns, 1.88; Initial conc., C0, 0.061 mg/L; Fraction of equilibrium sites, f, 0.92; Mass transfer rate, α, 0.000236 1/day; C) Empirical distribution coefficient, kd, 0.071 L/g; Initial conc., C0, 0.061 mg/L; Fraction of equilibrium sites, f, 0.92; Mass transfer rate, α, 0.000236 1/day;
Overall, the current results indicate a kinetic DDE sorption/desorption behavior characterized with a fast sorption/desorption within the first 3-5 days followed by a slow equilibrating process. This kinetic behavior can be modeled using a two site kinetic/equilibrium sorption/desorption model. The sorption/desorption model input parameters can be estimated using independent batch sorption/desorption experiments. A significant DDE mass loss occurred due to the flume channel in the flume experiment studies even though preventative measures such as using a PTFE liner were employed. This mass loss should be considered in order to correctly apply the exchange model to simulate the exchange of DDE with the streambed. The introduction of fine particles (kaolinite colloids) significantly influences the exchange of p,p’-DDE between the stream and streambed. Under given flume experiment conditions, the Freundlich nonlinear coefficient, ns, is the most sensitive input parameter.
Short Term Work Plan and Expected Results
Given the problems during the past two years with personnel changes and laboratory water toxicity, a no-cost extension was requested and approved to extend the project an additional year. The short-term work plan for June 2008–February 2009 and expected results will include:
- Comparison of the SPMEs with tissue uptake by L. variegates.
- Test additional sediment types within the SRFs with in situ exposures during stressor additions.
- Conducting stream recirculating flume experiments for the upwelling case using various natural sediments, including PCB contaminated sediments.
- Developing the exchange model for upwelling case in the presence or absence of resuspension.
- Linking the bioaccumulation models with the developed transport models and test the modeling results using flume experiments.
- Limited field validation of laboratory findings at a PCB contaminated site (likely Dicks Creek).
Discussion of Expenditures to Date
To date, grant expenditures include student support and supplies purchases. Expenses used for student support has been followed exactly as proposed. However, funds budgeted for supplies have been tight. Thus, CREST-RESSACA (TAMUK) and various grants and contracts of Dr. Burton’s have leveraged some of the supply and personnel costs.
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.