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University of California Department Land, Air and Water Resources 123 Veihmeyer Hall University of California Davis, CA 95616
jwhopmans{at}ucdavis.edu
Edited by BRIAN B. LOONEY and RONALD W. FALTA. Batelle Press, 505 King Avenue, Columbus, Ohio 43201-2693. 2000. Hardbound, 2 volumes, 1540 p. ISBN 1-57477-085-3.
The preparation and the writing of this 1500+ two-volume publication on vadose zone principles and applications, together with an accompanying CD of case studies, was sponsored by the U.S. Department of Energy (DOE) in close collaboration with other U.S. Agencies such as EPA, USGS, DOD, and USDA, and scientists at universities and with industries. This comprehensive compilation of current state-of-the-art principles and technology applications was the result of three separate national workshops, with participation of about 50 scientists, having basic and applied backgrounds in a variety of disciplines that collectively comprised a representative cross section of the vadose zone scientific community, including graduate students in science and engineering, professionals, research scientists, and managers. Although the book agrees that much progress has been made in applying basic principles to remedy pollutant fate and transport in the vadose zone environment, it is argued that many issues still remain unresolved and that a concerted effort is required by funding agencies, vadose zone managers and regulators, and the scientific community. The premise of the book is to provide an understanding of vadose zone concepts to a broad audience so as to convince policy makers to continue their sustained support of long-term multi-disciplinary research. This is accomplished by identifying and describing the most significant challenges and knowledge gaps in vadose zone research, using a technical format that may be understood by all stakeholders in the general environmental arena. To achieve this goal, the authors have chosen not to pursue an in-depth review of all scientific details of vadose zone science.
The extensive description of vadose zone science is especially important when realizing that enhanced understanding of the vadose zone is essential for the improved control and management of pollutants in the subsurface, with the ultimate aim to minimize the risks of contamination of groundwater. The books point out that, as compared with groundwater, the vadose zone has not been studied as extensively as a comprehensive science, but rather by a multiple array of separate disciplines, resulting in a wide knowledge gap of underlying principles and delaying effective application of remediation and long-term stewardship technologies. Because of vadose zone complexities, integration of all earth and environmental sciences, including management and policy, is highly relevant. The two books serve to convince the environmental community that existing knowledge and technologies are not adequate to satisfactorily characterize, monitor, manage, remedy, and/or predict the fate and transport of pollutants in the vadose zone. Case studies such as at those conducted at Hanford and Yucca Mountain and many other sites are presented to highlight the common lack of scientific understanding and inadequate technologies. The major shortcomings are identified in the final chapter.
The first chapter defines vadose zone science, its importance, fundamental processes, and the current state-of-the-art, particularly its significance and its controlling role for environmental cleanup, by including high-visibility case studies to document knowledge gaps and future directions. In the second chapter the reader is introduced to a list of principles of effective vadose zone management, to mainly help policy makers overcome technical difficulties, scientific knowledge gaps, and regulatory barriers. One of the guiding principles is the development of a roadmap that formalizes long-term objectives and goals, while considering current limitations of knowledge, data uncertainty, risk analysis, and resources availability. Chapters 3 and 4 comprising some 450 pages, summarize technologies and applications of current and future developments of vadose characterization and monitoring methods, including chemical and biological monitoring. Case studies demonstrate applications of techniques at contaminated sites, such as at INEEL, Yucca Mountain, Hanford, the Savannah River Site, and other DOE facilities. Developments in vadose zone modeling, described in Chapter 5, include sections on data needs and model calibration. The concluding section of this chapter on recommended future research directions points out the need to improve data quantity and quality and to reduce model uncertainty. The importance of geochemical and microbiological processes on contaminant mobility and fate is emphasized in Chapter 6. This chapter concludes that future work must focus on the incorporation of biological and geochemical processes in vadose zone transport models, their control by spatial and temporal variations of hydrological processes, and their upscaling from the laboratory to the field scale. Chapters 7 and 8 review principles and operation of various remediation technologies, and their performances with organic and anorganic chemicals in the vadose zone, respectively. Organic remediation includes contaminant recovery and bioremediation, as well as other attenuation techniques such as reactive barriers and phytoremediation. Key gaps in current capabilities of these technologies are caused by soil and geologic heterogeneities, and a lack of pilot-scale field tests of remedial technologies. In situ remediation of inorganic contaminants (heavy metals, radionuclides, nitrate) include removal, stabilization, and natural attenuation by physical, electrochemical, and biological methods. Principles and performances of various barriers and containment methods are presented in Chapter 9.
The final chapter, "Future Science and Technology Focus," was written by the editors and reviewed by all lead authors of the book. It therefore gives a collective view of the research needs of vadose zone science. I have generalized these in the following three priorities. First, the text concludes that an interdisciplinary approach is needed, including participation by theoreticians and practitioners, across a wide spectrum of disciplines, including soil science, hydrology, geology, engineering, mathematics, social sciences, policy, and management. Such an approach is evident when considering the complexity of the pollutant problem that begs for applying all possible techniques available. In addition, pollutant fate is controlled by physical, chemical, and biological processes that are historically studied in separate disciplines, rather than by the proposed collective effort. Also, the chapter makes a clear case that the transition of application of basic theory to real world applications is greatly enhanced by combining expertise early on, thereby providing more ideal conditions for validation and testing new characterization, monitoring, and remediation technologies.
Second, the vadose zone community must apply theory, measurements, and technology applications to a range of spatial scales, and develop spatial scaling procedures. Much research, both theoretical and applied, and specifically chemistry and biology, should move from the lab bench early on to investigate its validity under real soil conditions. Specifically, it is recommended to prioritize detailed and integrated medium-scale field experiments (at the meter scale), preferentially conducted at existing contaminated sites.
Third, it is recommended to prioritize the development of a standard toolbox of enhanced characterization and monitoring techniques and technologies that can incorporate soil heterogeneity. Especially needed are instrumental and mathematical techniques that improve data quality and better address uncertainty of fate and transport in the vadose zone. Moreover, it is stressed that such tools may be scale-specific and that different characterization and data collection techniques may be needed at different spatial scales, and for different purposes. Within this general priority area, the need for improved coupled (physics, hydrology, chemistry–biology) numerical modeling techniques was highlighted, stimulated by the proposed interdisciplinary research approach.
In summary, the two-volume text provides an enormous inspiration for the vadose zone research community by presenting many opportunities for vadose zone research. In addition to highlighting many specific research areas in a wide spectrum of disciplines, reading this vadose zone text will also stimulate scientists, students, stakeholders, and policy and decision makers to take a general integrated approach so as to provide a consensus among all that vadose zone problems are complex and require a collective vadose zone research effort. As such, the books may serve as a reference that can be used by policy and decision makers to justify their commitment to vadose zone research. In addition, the book provides an excellent overview of vadose zone concepts and measurement techniques, with a broad suite of example applications.
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