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211.
212.
Chencho Norbu Prof. Timothy J. Downs Edward Yeboah Dr. L.J.R. Scholtens Dr. Jyotsna Bapat Maren Oelbermann Ph.D. Sayyed Ahang Kowsar Jaime Alexandra Webbe Bram Govaerts Ph.D. Nele Verhulst M. Sc. Goodspeed Kopolo Maria Rosário Partidário Mr. N’guessan Alphonse Kouassi John All Ph.D. JD Narcisa Pricope Leslie Lipper 《Natural resources forum》2008,32(3):252-256
213.
George R. Holdren Jr. Timothy C. Strickland Bernard J. Cosby David Marmorek David Bernard Robert Santore Charles T. Driscoll Linda Pardo Carolyn Hunsaker Robert S. Turner John Aber 《Environmental management》1993,17(3):355-363
The critical loads approach is emerging as an attractive means for evaluating the effects of atmospheric deposition on sensitive
terrestrial and aquatic ecosystems. Various approaches are available for modeling ecosystem responses to deposition and for
estimating critical load values. These approaches include empirical and statistical relationships, steady-state and simple
process models, and integrated-effects models. For any given ecosystem, the most technically sophisticated approach will not
necessarily be the most appropriate for all applications; identification of the most useful approach depends upon the degree
of accuracy needed and upon data and computational requirements, biogeochemical processes being modeled, approaches used for
representing model results on regional bases, and desired degree of spatial and temporal resolution. Different approaches
are characterized by different levels of uncertainty. If the limitations of individual approaches are known, the user can
determine whether an approach provides a reasonable basis for decision making. Several options, including point maps, grid
maps, and ecoregional maps, are available for presenting model results in a regional context. These are discussed using hypothetical
examples for choosing populations and damage limits.
The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared
at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract #68-C8-0006 with ManTech Environmental
Technology, Inc., and Interagency Agreement #1824-B014-A7 with the U.S. Department of Energy and at Oak Ridge National Laboratory
managed by Martin Marietta Energy Systems, Inc., under Contract DE-AC05-84OR21400 with the US Department of Energy. Environmental
Sciences Division Publication No. 3904. It has been subjected to the agency’s peer and administrative review and approved
for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. 相似文献
214.
Carolyn Hunsaker Robin Graham Robert S. Turner Paul L. Ringold George R. Holdren Jr. Timothy C. Strickland 《Environmental management》1993,17(3):335-341
The United States Environmental Protection Agency, with support from the US Department of Energy and the National Oceanographic
and Atmospheric Administration, has been evaluating the feasibility of an effects-based (critical loads) approach to atmospheric
pollutant regulation and abatement. The rationale used to develop three of the six steps in a flexible assessment framework
(Strickland and others, 1992) is presented along with a discussion of a variety of implementation approaches and their ramifications.
The rationale proposes that it is necessary to provide an explicit statement of the condition of the resource that is considered
valuable (assessment end point) because: (1) individual ecosystem components may be more or less sensitive to deposition,
(2) it is necessary to select indicators of ecosystem condition that can be objectively measured and that reflect changes
in the quality of the assessment end point, and (3) acceptable status (i.e., value of indicator and quality of assessment
end point at critical load) must be defined. The rationale also stresses the importance of defining the assessment regions
and subregions to improve the analysis and understanding of the indicator response to deposition. Subregional definition can
be based on a variety of criteria, including informed judgment or quantitative procedures. It also depends on the geographic
scale at which exposure and effects models are accurate and on data availability, resolution, and quality.
The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared
at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract #68-C8-0006 with ManTech Environmental
Technology, Inc., and Interagency Agreement #1824-B014-A7 with the US Department of Energy and at Oak Ridge National Laboratory
managed by Martin Marietta Energy Systems, Inc., under Contract DE-AC05-84OR21400 with the US Department of Energy. Environmental
Sciences Division Publication No. 3903. It has been subjected to the agency’s peer and administrative review and approved
for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. 相似文献
215.
Hyde Tools, Inc., of Southbridge, Massachusetts, is a medium-sized firm employing about three hundred persons. In 1988, it learned of a company that eliminated its wastewater discharge after being threatened with massive Clean Water Act fines resulting from a suit brought by a Massachusetts environmental group. Hyde decided to devise a similar program to attain zero water discharge and do it within five years. More than 75 percent toward its goal, Hyde'S environmental success, detailed in this article, still relies heavily on the company'S Total Quality Management system and the efforts of a dedicated environmental staff. Hyde'S success typifies TQEM in action—showing how small continuous improvements can lead to significant financial paybacks. 相似文献
216.
Sensitivity of SCS Models to Curve Number Variation1 总被引:1,自引:0,他引:1
Timothy R. Bondelid Richard H. McCuen Thomas J. Jackson 《Journal of the American Water Resources Association》1982,18(1):111-116
ABSTRACT: The Soil Conservation Service (SCS) models, including the TR-20 computer program and the simplified methods in TR-55, are widely used in hydrologic design. The runoff curve number (CN), which is an important input parameter to SCS models, is defined in terms of land use tretments, hydrologic, condition, antecedent soil moisture, and soil type. The objective of this study was to evaluate the sensitivity of the SCS models to errors in CN estimates. The results show that the effects of CN variation decrease as the design rainfall depth increases, such as for the larger storm events. The value and use of the sensitivity curves are demonstrated using a comparison of Landsat and conventionally derived curve numbers for three watersheds in Pennsylvania. 相似文献
217.
Timothy O'Riordan 《The Environmentalist》1981,1(1):15-24
Summary Environmental management is defined as a mechanism for alleviating the worst of environmental damage and reducing the most unacceptable aspects of social inequalities but without really altering the patterns of political and economic power. It is now increasingly regarded as accepted practice in development partly because it is economically and socially counterproductive to ignore it. The purpose of the paper is to illustrate the difficulties involved in incorporating environmental management into economic growth with special reference to development assistance. Much environmental damage in the Third World is a product of the forces of development rather than the fault of the people, and in the past development assistance projects have often inadvertently led to environmental destruction and social distress. Case examples are given. The paper argues that among the many impediments to the full incorporation of environmental management into development are the following: the administrative structure of the agencies involved, suspicions in the past of receiving nation governments and the risky nature, and expensive labour intensity of programmes aimed at integrated rural development and appropriate technology. Some recommendations are advanced involving administrative reorganisation, new training skills and diplomacy, although no major breakthroughs are expected to come quickly.Geography graduate from the University of Edinburgh, Harkness Fellowship and Carnegie Scholarship to study at Cambridge (UK) and Cornell (USA). University appointments in Canada and UK. Authority in the field of Resource Management. Author of Progress in Resource Management and Environmental Planning. 相似文献
218.
David B. Baker R. Peter Richards Timothy T. Loftus Jack W. Kramer 《Journal of the American Water Resources Association》2004,40(2):503-522
ABSTRACT: The term flashiness reflects the frequency and rapidity of short term changes in streamflow, especially during runoff events. Flashiness is an important component of a stream's hydrologic regime. A variety of land use and land management changes may lead to increased or decreased flashiness, often to the detriment of aquatic life. This paper presents a newly developed flashiness index, which is based on mean daily flows. The index is calculated by dividing the pathlength of flow oscillations for a time interval (i.e., the sum of the absolute values of day‐to‐day changes in mean daily flow) by total discharge during that time interval. This index has low interannual variability, relative to most flow regime indicators, and thus greater power to detect trends. Index values were calculated for 515 Midwestern streams for the 27‐year period from 1975 through 2001. Statistically significant increases were present in 22 percent of the streams, primarily in the eastern portion of the study area, while decreases were present in 9 percent, primarily in the western portion. Index values tend to decrease with increasing watershed area and with increasing unit area ground water inputs. Area compensated index values often shift at ecoregion boundaries. Potential index applications include evaluation of programs to restore more natural flow regimes. 相似文献
219.
Arturo A. Keller Yi Zheng Timothy H. Robinson 《Journal of the American Water Resources Association》2004,40(3):721-735
ABSTRACT: Traditional approaches to establishing critical water quality conditions, based on statistical analysis of low flow conditions and expressed as a recurrence interval for low flow conditions (e.g., 7Q10), may be inappropriate for drier watersheds. The use of 7Q10 as a standard design flow assumes year‐round flow, but in these watersheds, 7Q10 is zero or very small. In addition, the increasing use of multiple year dynamic water quality models at daily time steps can supercede the use of steady state approaches. Many of these watersheds are also under increasing urbanization pressure, which accentuates the flashiness of runoff and the episodic nature of critical water quality conditions. To illustrate, the conditions in the Santa Clara River, California, are considered. A statistical analysis indicates that higher inorganic nitrogen concentrations correlate strongly with low flow. However, peaks in concentrations can occur during the first storms, particularly where nonpoint source contribution is significant. Critical conditions can thus occur at different flow regimes depending on the relative magnitude of flow and pollutant contributions from various sources. The use of steady state models for these dry semi‐urbanized watersheds based on 7Q10 flows is thus unlikely to accurately simulate the potential for exceeding water quality objectives. Dynamic simulation of water quality is necessary, and as the recent intense storm event sampling data indicate, the models should be formulated to consider even smaller time steps. This places increasing demand on computational resources and datasets to accurately calibrate the models at this temporal resolution. 相似文献
220.
Aquatic toxicity due to the creation and mobilization of chemical constituents by fire has been little studied, despite reports of post-fire fish kills attributed to unspecified pyrogenic toxicants. We examined releases of cyanides from biomass burning and their effect on surface runoff water. In laboratory test burns, available cyanide concentrations in leachate from residual ash were much higher than in leachate from partially burned and unburned fuel and were similar to or higher than the 96-h median lethal concentration (LC50) for rainbow trout (45 microg/l). Free cyanide concentrations in stormwater runoff collected after a wildfire in North Carolina averaged 49 microg/l, again similar to the rainbow trout LC50 and an order of magnitude higher than in samples from an adjacent unburned area. Pyrogenic cyanide inputs, together with other fire-related stressors, may contribute to post-fire fish mortalities, particularly those affecting salmonids. 相似文献