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number of hazardous waste :es (HWS) i n the United ates considered threatening human health and the environment has skyrocketed from a few hundred in the 1970s to tens of thousands in the 1980s ( I ) . In the late 1980s more than 4000 solid waste management units (SWMus)-inactive hazardous waste sites and Department of Energy (DOE) facilities-became subject to EPA oversight. Many DOE facilities and their SwMUs, especially larger, abandoned sites, are in the semiarid West (2).Estimated costs of remediating the contaminated federal facilities have varied widely, some exceeding $100 billion. There are numerous examples of remedial measures not working as expected. Clearly, greater flexibility and opportunity for ecological research and monitoring should be factored into the process. Because of these reasons and the lack of proven remediation technology. every site may not be cleaned up (3). The western sites are likely to receive less attention because many are in sparsely populated areas and may be assumed to present low exposure risk. This strongly underscores the necessity for develop1022 Environ. Sd. Technol.. Vol. 27, No. 6, 1993
ing priorities based on adequate analysis and documentation of the human health and environmental risks posed by HWS. To assess and mitigate such risks at these sites, we believe a comprehensive approach is needed. Site management efforts must go beyond the conventional sampling, modeling, and generic health risk assessments currently performed at the Superfund sites. For the remote and expansive semiarid sites, a logical approach would put greater emphasis on determining ecological effects and processes, including contaminant dynamics, than on merely sampling for physical and chemical site characterization. Some major citizen groups have recently called for giving due attention to environmental impacts and issues at inactive HWS ( 4 ) . In response to these concerns. The Of-
S T U A R T A. N I C H O L S O N
New Mexico Highlands University Los Vegas, NM87701
NIRANDER M. SAFAYA North Dakota Public Service Commission Bismarck, ND 58505
fice of Technology Assessment (OTA) noted recently that "ecological issues are often ignored in the initial planning activities at Superfund sites," and recommended that ecological studies be included to better define problems and assess the effectiveness of remedial measures (2).EPA has started to expand its efforts to address ecological effects at H W S (5). There are no comprehensive databases on H W S ecology to draw on other than general principles of ecotoxicology and some documented effects of contaminants on biota. Therefore, it is time to identify and address ways in which ecological factors bear on the HWS discovery and remediation process, especially in advance of major resource commitments along existing lines for the harsh, isolated western sites. Ecological factors at HWS Ecological factors operate at HWS through individual organisms, population interactions, community structure a n d change, bioticedaphic (Le., relating to the soil as it affects living organisms) interactions, and other ecosystem processes. For example, many contaminants affect normal metabolism,
W13-936w93/0927-1022$04.00/0 0 1993 American Chemical S o c i q
bioaccumulate in organisms, and become biomagnified i n food chains (6). Very often, intrusion of contaminants in the biota causes toxic effects of various types and magnitude. A variety of methods has been developed to assess such ecological effects, including toxicity testing, biomarkers, biomonitoring, a n d ecological risk assessments (5,7). Recently, application of ecological risk assessment was demonstrated for a portion of Oak Ridge National Laboratory exposed to contaminants (8). However, although there have been numerous assessments of ecotoxicity for substances such as heavy metals and pesticides, such assessments for other organic xenobiotics characteristic of HWS have been minimal. The fate and distribution of contaminants are largely determined by their chemistry and the abiotic and biotic components of the ecosystem. Abiotic factors affect mobility and transformation. Biotic factors influence contaminants through bioaccumulation, biomagnification, and biotransformation (9). Vegetation particularly has a major influence on H W S because it minimizes water and wind erosion and de-
creases infiltration through evapotranspiration and interception. Less commonly recognized effects of vegetation include contaminant uptake, locally focused infiltration channeling from root decay, and other hydrological effects from litter and incorporated organic matter (10). Increases in organic matter generally promote soil microflora by providing nutrients and habitat. A dense vegetative cover also promotes invasion by various wildlife species, though attraction of deepburrowing animals may be an undesirable effect. Finally, plant communities and habitat characteristics at any given site are subject to change through succession, or in response to stressors and other disturbances, or from developments on neighboring sites. Thus, any attempt to predict the effects of ecological factors at HWS must take into account the possibility of both short-term and long-term changes that occur naturally in the ecosystems. A few predictive models have been developed for certain systems (11).
HWS discovery Ecological attributes have frequently played a significant role, al-
beit accidentally, in HWS discovery. However, the systematic use of site ecological attributes as indicators of contamination in commercial site assessments is still in its infancy. The state of the art is little more than noting “that funny looking vegetation” or “yellow grass.” Aerial photo analysis and interpretation provide innovative means of detecting time-space patterns of toxic chemical contamination. Another possibility, apparently little explored in the context of H W S assessment, is detecting contamination through remote sensing of vegetation spectral properties. The scientific feasibility and costeffectiveness of such techniques need to be thoroughly explored. EPA’s recent review of ecotoxicity indicators (7)offers insights into additional approaches that may be applied to discovering HWS. There also are many unexploited uses of ecological attributes in initial site investigations. Increased attention to and improved methods of studying ecological stress indicia could greatly assist in mapping the extent and severity of contamination. These methods include sampling biomarkers, ecological endpoints (71, absence of expected Envimn. Sci. Technol., Vol. 27. No. 6, 1993 1025
species, and aberrant vegetation patterns reflective of contaminant stress gradients or “hot spots.” Selected organisms may be directly analyzed for contaminants, but this is generally more expensive than the quick screening methods listed above. Once contamination is verified, analysis of vegetation patterns through historical sequences of aerial photographs will help determine patterns of contaminant spread, contaminant origin sites, and possibly the nature of the contamination sources. Remedial and feasibility studies Until recently, EPA guidelines on addressing ecological factors in remedial investigations (RI)and feasibility studies (FS) were general and limited (12). Therefore, ecological attributes were often ignored or discounted in RI and FS. This was unfortunate because, first, all remedial actions have some ecological effects, particularly those involving major excavation, chemical treatments, or compaction; second, ecological factors often determine the effectiveness of remedial measures: and third, the way ecological attributes are affected critically influences both remedial reclamation and end use. To assess the effectiveness of remedial actions it is necessary to know their nature, the risks involved in adoption, and ecotoxicological responses (5, 7,8). Therefore, we need both qualitative and quantitative information on HWS to evaluate responses to stressors and their postremediation suitability for vegetation establishment. An approach similar to that used for the reclamation of surface coal mines would be an appropriate starting point (13). This approach includes characterization of soils and vegetation, wildlife inventory, and bioassays using indicator species. An understanding of the vegetation and other ecological attributes of the unremediated site and the uncontaminated neighboring sites will provide valuable information on the type of plant communities (or ecosystems) that the remediated sites will be capable of developing. Considerations in remedial design Ecological factors must also be considered in the selection and implementation of remedial plans. Because drastically disturbed ecosystems take a long time to reach some degree of equilibrium and rehabilitate, imposition of short, rigid time 1024 Envimn. Sci. Technol., Vol. 27, No, 6, 1993
frames can be counterproductive. Cover systems-that is, techniques for covering HWS-of various designs have been researched and used for remediation. These include appropriate vegetation, surface soils, and “biobarriers.” An Army Corps study ( 1 7 ) has listed desirable properties of herbaceous and woody vegetation which include ability to establish, proliferate, and develop dense cover on remediated sites. Species with deep taproots and those that attract burrowing animals should be avoided. Also, raptor roosts could be designed in to limit burrowing rodents. Cline (15) demonstrated that a subsurface cobble layer provided a successful biobarrier to burrowers and, to some extent, roots. One issue conspicuously omitted in reviews of vegetation appropriate for HWS is the problem of community change. Clearly, in choosing species one must be aware of the changes that a community may undergo under the given set of conditions, and, to the extent possible, design for these. This would mean either directly establishing the endpoint community at the site (seldom feasible because of unsuitable substrate), or starting with appropriate precursors (site-adapted pioneer species) that would lead to such endpoints. In the meantime, the physical and chemical conditions of the remediated site should not be allowed to deteriorate, as they will affect both the establishment and succession of the plant community. This may require the adoption of interim management techniques that help stabilize the sites and allow proper plant establishment and succession. Ecological factors are also relevant in bioremediation. Organisms other than bacteria, such as molds and yeasts (161, affect organic matter generation, decomposition, and site environmental modification. Vegetation with high productivity and decomposable litter is likely to provide a favorable environment to most bacteria and other microorganisms. Also, in case of passive remediation or the “no action” scenario, vegetation with characteristics desirable for both cover systems and bioremediation would be appropriate. Where remediation methods that solidify or vitrify contaminants have been used, the surface vegetation should be of a type that neither brings up the contaminants nor creates wide channels through deep rooting.
Conclusion We urgently need to address ecological considerations in the preand post-remediation and reclamation of HWS. It is an opportune time for integrating ecological information with the remediation measures that will be needed at many western semiarid sites. Ecological monitoring of HWS must become an integral part of remediation. Greater interagency cooperation and information exchange should expedite these goals. This approach will provide better environmental protection and prove to be more costeffective and socially acceptable in
S t u d A. Nicholson is on envimnmental scientist/ecologist ond attorney who teaches in the Environmental Science Pmgmm at NMHU and consults notionally and internotionally. He has a Ph.D. from Georgia ond a 1.D. degree from North Dakota. He focuses on ecological, ethical, and policy aspects of envimnmental restoration, risk assessment/ management, canservotion biology, business and the environment, and sustoinobility. He recently contributed to the book, The Greening of American Business (Government Institutes, 1992). and is authoring a text on business environmental ethics.
Nimnder M.Sofoyo is a senior envimnmental scientist at the North Dakota Public Service Commission, Bismarck. ND. He received an M.Sc. degree in botany and a Ph.D. in soil-plont nutrition from Aligorh University in Indio, and post-doctoml tmining at the CSIRO labomtories in Australia. He has worked on troce element problems in agriculture and conducted reclamation research and regulotion of surfoce-mined U S . lands. He is interested in environmental policy and has presented his work in national ond internationol forums.
the long run than the purely engineering approaches. It is therefore essential that agencies and organizations involved in HWS cleanup allocate adequate technical and monetary resources for determining ecological impacts, processes, and changes at HWS. Acknowledgment The authors are thankful to several scientists of Oak Ridge National Laboratory, TN, and Los Alamos National Laboratory, NM, for their s u p p o r t a n d encouragement.
Reagent Chem Eighth Edition
References (1) “The Superfund Program: Ten Years
of Progress”; U.S. Environmental Protection Agency: Washington, DC, 1991; EPA/540/8-91/003. (2) U.S.Congress Office of Technology Assessment. “Complex Cleanup: The Environmental Legacy of Nuclear Weapons Production”; U.S. Government Printing Office: Washington, DC, 1991; OTA-0-484. (3) Satchell, M. US.News & World Report, March 27, 1989, pp. 20-22. (4) Comp, T. A,, Ed.; Blueprint for the Environment; Island Press: Washington, DC, 1988. (5) Bascietto, J, et al. Environ. Sci. Techno]. 1990, 24, 10-14. (6) Ramade, F. Ecotoxicology; John Wiley: New York, 1987. (7) Warren-Hicks, B.; Parkhurst, R.; Baker, S. “Ecological Assessment of Hazardous Waste Sites: A Field and Laboratory Reference”; US.Environmental Protection Agency: Washington, DC, 1989; EPA/600/3-89-13. (8) Suter, G. W. 111; Loar, J. M. Environ. Sci. Technol. 1992,26,432-38. (9) Connell, D.; Miller, G. J,, Eds.; Chemistry and Ecotoxicology of Pollution; John Wiley: New York, 1984. (10) Wallace, A. et al. In Research Program at Maxey Flats and Consideration of Other Shallow Burial Sites; Pacific Northwest Laboratories. Department of Energy: Richland, WA, 1981; NUREGICR-1832. Luken, J. 0. Directing Ecological Succession; Chapman and Hall: New York, 1990. “Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA”; U.S. Environmental Protection Agency: Washington, DC, 1988; EPA 540/G-89/004. (13) Nicholson, S. A., Ed.; Vegetation-Environment Relafionships of Abandoned Mines: Toward their Successful Revegetation, Stability, and Longterm Production; University of North Dakota: Grand Forks, ND, 1984. (14) McAneny, C. C. et al. “Covers for Uncontrolled Hazardous Waste Sites’’; Washington, DC, 1985;EPA 540/2-85. (15) Cline, J, F. Bio-Barriers Used in Shallow Ground Burial Stabilization; Department of Energy. Pacific Northwest Laboratory. National Technical Information Service: Springfield, VA, 1979. (16) Newton, J. Pollut. Eng. 1990, 22,
46-49.
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