Grantee Research Project Results
2003 Progress Report: Sustainable Remediation
EPA Grant Number: R828770C003Subproject: this is subproject number 003 , established and managed by the Center Director under grant R828770
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: HSRC (2001) - Midwest Hazardous Substance Research Center
Center Director: Banks, M. Katherine
Title: Sustainable Remediation
Investigators: Shann, Jodi R. , Rogstad, Steven
Institution: University of Cincinnati
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2001 through September 30, 2004
Project Period Covered by this Report: October 1, 2002 through September 30, 2003
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The objective of this research project is to determine if the natural process of succession (ecological change over time) is an effective and sustainable means of managing historically contaminated sites. Natural revegetation would eliminate the planting costs that are part of standard phytoremediation plans, and would better ensure the success of plants because they would only persist in areas that support their growth. Subsequent succession of the plant community across a site likely would lead to a self-sustaining system of increasing compositional and, perhaps, functional biodiversity. If the natural vegetation reduces and/or stabilizes contaminants while producing a community that looks and functions in a fashion comparable to others in the vicinity, the outcome would be both site remediation and ecological restoration.
The project approach is split into two studies: one approach is focused on remediation, the other approach is focused on plant succession. Indicators of success under the remediation study include: decreased soil contamination and/or increased stability of contaminants. Stability is measured by this study as decreases in contaminant: (1) mobility within the soil; (2) erosion from the surface; or (3) bioavailability. Ecological restoration is the single success indicator of the succession study. Ecological integrity measures include increased site biodiversity, productivity, and soil quality.
Progress Summary:
Field Design and Sampling Activities
Prior to the actual startup of this funding (the summer of 2000), plots were established and the baseline sampling was completed. Since then, three full field seasons (2001-2003) have been completed. Plant data (cover, species diversity, biomass/productivity) were generated over four seasons (2000-2003). Replicate soil cores were removed from plots seasonally. Soil from each core was analyzed for total organic carbon, C/N, pH, texture, water holding capacity, and cation exchange capacity. Soil extracts were analyzed for metals (Pb, Cr, Ni, Zn) and polycyclic aromatic hydrocarbons (PAHs). These data sets are now complete and available as Excel files.
Remediation Study
Changes in Soil Contamination. Recognizing that the rate of contaminant loss from aged soils may be very slow, we evaluated our ability to detect real changes over time. It appears that a repeated measures approach provides adequate statistical power, but this could be compromised by a high degree of localized heterogeneity. Therefore, a spatial characterization of the Land Treatment Unit (LTU) was conducted in the summer of 2002 by uniformly sampling across the entire site. Data were collected on surface soil PAHs, metals, moisture, as well as surface elevation, light intensity, and air humidity. From this, geographic information system (GIS) plots of contamination and environmental conditions (such as those shown in Figure 1) were generated. Since then, experimental plot data have been combined with the GIS site models of environmental conditions and contamination to answer the question: on an aged site like this, what more influences plant establishment and ecological succession, soil contamination or the standard environmental conditions of light, moisture, and elevation? This question is beyond what was originally proposed, but will make a major contribution to our ability to predict the success of natural site management. Preliminary statistical analysis shows no significant correlation between plant parameters and soil contamination, suggesting that ecological succession is responding to other site factors.
Figure 1. GIS Contour Plots of Environmental Conditions and Soil Contamination Across the Hooven LTU. Sampling locations are marked by dots on the four plots of environmental conditions.
Increases in Contaminant Stabilization. Indicators of stabilization, as noted above, include low mobility in soil, low bioavailability, and reduced particle erosion. Data collection and analysis for these indicator areas have been completed .
Metal mobility has been evaluated by sequential extraction of soil from cores. A mild extraction procedure was used to assess PAH mobility. Although PAHsare somewhat more available (as a percent of their total soil load) than the metals, both types of contamination have become more difficult to extract, indicating increased fixation to the soil.
Data from the field and laboratory studies support the next positive indicator of stabilization, low bioavailability. Bioavailability was extrapolated from data on the ability (i.e., potential) of typical LTU plant species to take up metal, compared to their actual (realized) uptake from LTU soils. To estimate potential, plants were grown hydroponically in metal solutions. To determine realized uptake, tissue metal content was measured in plants grown in LTU soil. Tissue samples were collected from greenhouse grown plants as well as those growing naturally on the LTU. Although Goldenrod took up all metals, the uptake and response to nickel (see Figure 2) generally represents overall results.
Figure 2. Growth (Bars) and Tissue Metal Concentration (Line) of Goldenrod (Hydroponically) Exposed to Nickel Concentrations of 0, 5, 10, or 50 ppm (µg/mL). Shoot tissue concentrations of 200–1,000 ppm indicate the presence of metal uptake mechanisms in Goldenrod. Tissue levels in Goldenrod, however, grown in LTU soil (where the average Ni concentration was 675 ppm) never reached 10 ppm Ni. In addition, significant phytotoxicity was observed with exposure to fully available Ni, although no inhibition occurred in soil-grown plants.
Figure 3. Changes in Vegetative Cover Across the LTU, 1999-2002. Cover associated with rye is shown on the lower portion of each bar. Cover was estimated from data generated within the experimental plots. Cover for this project is not canopy coverage of the surface, but rather the actual presence of plant stems growing out of the soil.
The final indicator of stabilization, low surface erosion of soil particles, has been evaluated from data on cover. Cover in 1999 was 25 percent; all of which was the planted cover species, rye. In subsequent years, cover consisted of both rye (no longer planted in) and the local natural vegetation. From 2000 to 2002, cover increased from 32, to 58, to 80 percent. More significantly, the rye proportion of this cover actually decreased over that same period from 27 to less than 20 percent. The rapid increase in plant cover, therefore, is a function of natural revegetation. Cover associated with non-rye species increased from 5 to 68 percent between 2000 and 2002.
Figure 4. Changes in Cover because of Invasive Plant Species. The natural community does contain some plant species considered invasive, but only to the same extent expected locally.
Succession Study
The data sets on the two most important indicators of success, biodiversity and productivity, are now complete and statistically robust. Biodiversity of the plant community is increasing significantly, which is typical of early stage succession. Primary productivity (measured as biomass per unit area) initially appeared to decrease between 2000 and 2002. This was a function of the decrease in rye and the increase in the natural species. Rye forms heavy clumps that weigh a lot, even if the cover is less. This complicating factor was addressed by separating the biomass produced by the natural species from that produced by the rye. As can be seen in Figure 5, the productivity of successional vegetation increased significantly in 2002.
Figure 5. The Biodiversity and Primary Productivity of the Naturally Revegetating LTU Plant Community. For analysis, rye was removed from the data set.
Future Activities:
All samples have been collected for this project, and a majority of the samples have been analyzed. The enormous task of statistically comparing and interpreting these data is ongoing. The doctoral student involved in this project, Heather Henry, is now in the process of compiling results for her thesis. We anticipate that her graduation—as well as completion of this project—will be mid-year 2004. Heather and I have presented this work throughout the funding period, but also have recently begun to apply the general principles and conclusions to other sites and to other types of contamination. For example, our laboratory was invited to represent the United States at a conference (sponsored by the U.S. Environmental Protection Agency [EPA] and National Institutes of Health) in Vietnam. Heather attended and spoke on the topic of ecological restoration. Trichlorofluoroethene (TCFE) transformation rates were about 2.4 times faster than control microcosms and about four to five times slower than trichloroethene (TCE) transformation rates. TCE transformation products were cis-dichloroethene (DCE) and trans-DCE in approximately a 2:1 ratio, and TCFE transformation products were cis-DCFE and trans-DCFE in approximately 2:1 ratio as well. TCE ultimately was reduced to vinyl chloride (VC), but very little ethene was observed. TCFE was transformed into a mixture of DCFEs and CFEs, with no fluoroethene formation. Chlorinated aliphatic hydrocarbons (CAH) transformation rates were not affected by sulfate addition. From these tests, it was determined that succinate was a potential electron donor for further experiments and that TCFE transformation rates would have to be assessed in the sediments used in the physical aquifer model (PAM) tests to determine the relationship to TCE rates.
A seed culture was obtained from Dr. Semprini's group from their Evanite culture reactor, was serially fed butanol and PCE for about 2 months, and has shown complete dehalogenation of PCE to ethene. This culture will be used in future tests related to this project. A series of microcosms has been prepared with the same sediments that were used to pack the PAM, and will be used to test the survivability of the bioaugmented culture under different geochemical conditions. The water phase in the microcosms consists of tap water or tap water amended with 5 percent media solution used in the culture reactor. Both lactate and butanol will be tested as fermentable substrates, and bioaugmentation doses of 0.1, 1, and 10 mL of reactor culture also will be tested. The microcosms recently have been inoculated, and survivability should be assessed within about 30 days. The results will be used to determine the necessary water amendments and bioaugmentation dose for the PAM experiments.
A glass column of 5 cm diameter and 34 cm length has been packed with the same sediments used to pack the PAMs, and will be used to evaluate the transport characteristics of the bioaugmentation culture. A feed rate approximating the same linear average velocity to be used in the PAM will be used with an influent culture concentration approaching that found in the mother reactor (approximately 25-40 mg/L protein). Effluent samples will be acquired and analyzed for Dehalococcoides sp. using group-specific polymerase chain reaction (PCR) primers and compared to influent concentrations. The Evanite culture was tested using Dehalococcoides group-specific primers in PCR reactions and universal bacterial primers for terminal restriction fragment length polymorphism (T-RFLP) analyses. The Evanite culture was found to be highly enriched in Dehalococcoides sp. Serial dilutions of the Evanite culture were extracted and analyzed using Dehalococcoides group-specific PCR, and dilutions down to 10-4 were detectible by this process. Future work includes expanding this testing to limited real-time quantifiable PCR analyses to attain better enumeration of Dehalococcoides sp. within the effluent samples and for use in the PAM tests. A bromide tracer test currently is underway on the column to determine the flow characteristics of the system.
The PAMs have been packed with sediment from the Hanford, WA, site and have been saturated with oxygen-free water to produce anoxic conditions for the start of the test. Lactate solution will be added to the PAM just prior to bioaugmentation to ensure anaerobic conditions prior to bioaugmentation. Information in the literature on Dehalococcoides sp. involved in the critical step of VC transformation to ethane indicates an extreme sensitivity to oxygen, and every effort will be made to ensure anaerobic conditions in the PAM before onset of bioaugmentation.
Journal Articles:
No journal articles submitted with this report: View all 14 publications for this subprojectSupplemental Keywords:
remediation, phytoremediation, polycyclic aromatic hydrocarbon, PAH, metals, bioavailability, succession, ecological restoration, waste, water, contaminated sediments, ecology, ecosystem, hazardous, hazardous waste, chemical transport, community succession, contaminant transport, contaminated soil, ecological impacts, extraction of metals, hazardous waste treatment, heavy metal contamination, heavy metals, metal contamination, metal wastes, revegetation, sustainable remediation., RFA, Scientific Discipline, Waste, Water, Contaminated Sediments, Remediation, Environmental Chemistry, Hazardous Waste, Ecology and Ecosystems, Hazardous, hazardous waste treatment, revegitation, contaminant transport, revegetation, contaminated sediment, chemical transport, contaminated soil, PAH, ecological impacts, treatment, community succession, phytoremediation, metal wastes, extraction of metals, heavy metal contamination, sustainable remediation, heavy metals, metal contaminationRelevant Websites:
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R828770 HSRC (2001) - Midwest Hazardous Substance Research Center Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R828770C001 Technical Outreach Services for Communities
R828770C002 Technical Outreach Services for Native American Communities
R828770C003 Sustainable Remediation
R828770C004 Incorporating Natural Attenuation Into Design and Management
Strategies For Contaminated Sites
R828770C005 Metals Removal by Constructed Wetlands
R828770C006 Adaptation of Subsurface Microbial Biofilm Communities in Response to Chemical Stressors
R828770C007 Dewatering, Remediation, and Evaluation of Dredged Sediments
R828770C008 Interaction of Various Plant Species with Microbial PCB-Degraders
in Contaminated Soils
R828770C009 Microbial Indicators of Bioremediation Potential and Success
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.
Project Research Results
Main Center: R828770
108 publications for this center
14 journal articles for this center