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181.
Numerical site-specific chemical and biological criteria were established to assess the impact of a pilot dredging project
on water quality at the New Bedford Harbor, Massachusetts, USA, Superfund site. Because most existing chemical concentrations
in the water column and indigenous biota exceeded federal and state water quality limits, the derivation of site-specific
criteria was required. Prior to any operational phases of the project (i.e., dike construction, dredging), criteria values
were developed from background concentrations of PCBs and metals in water and biota, as well as for the toxic effects of water
quality on the biota. During each operational phase of the project, water samples were collected, analyzed within 16 h, and
the data supplied to a management committee in order to assess the environmental impact of the previous days' operation. The
ambient unfiltered water concentration of PCBs and metals were the only chemical or biological criteria exceeded. Modification
of the next days' operations resulted in a return of these concentrations to background levels. The combined use of site-specific
criteria and a real-time decision making management process allowed for successful completion of this project with a minimal
effect on water quality. 相似文献
182.
William F. Porter Nancy E. Mathews H. Brian Underwood Richard W. Sage Jr. Donald F. Behrend 《Environmental management》1991,15(6):809-814
Populations of white-tailed deer (Odocoileus virginianus) inhabiting many state and national parks and suburban areas have grown to the point that they conflict with human activities.
Conflicts range from destruction of vegetation through browsing to public perception that diseases carried by deer pose threats
to human health. Traditional modes of hunting to control populations are inappropriate in many of these areas because of intense
human development and activity. This article explores an alternative approach for population reduction based on deer social
organization. Female white-tailed deer are highly philopatric and female offspring remain near their dams for life. This suggests
that a population expands slowly as a series of overlapping home ranges in a form analogous to the petals on a rose. Incorporating
the rose petal concept into a model of population growth shows that removal of deer by family unit can potentially alleviate
conflicts in localized areas for as many as 10–15 yr. 相似文献
183.
184.
Analysis of bank erosion on the Merced River,Yosemite Valley,Yosemite National Park,California, USA 总被引:1,自引:0,他引:1
Channel changes from 1919 to 1989 were documented in two study reaches of the Merced River in Yosemite National Park through
a review of historical photographs and documents and a comparison of survey data. Bank erosion was prevalent and channel width
increased an average of 27% in the upstream reach, where human use was concentrated. Here, trampling of the banks and riparian
vegetation was common, and banks eroded on straight stretches as frequently as on meander bends. Six bridges in the upper
reach constrict the channel by an average of 38% of the original width, causing severe erosion. In the downstream control
reach, where human use was minimal, channel widths both decreased and increased, with a mean increase of only 4% since 1919.
Bank erosion in the control reach occurred primarily on meander bends. The control reach also had denser stands of riparian
vegetation and a higher frequency of large woody debris in channels. There is only one bridge in the lower reach, located
at the downstream end. Since 1919, bank erosion in the impacted upstream reach contributed a significant amount of sediment
(74,800 tonnes, equivalent to 2.0 t/km2/yr) to the river. An analysis of 75 years of precipitation and hydrologic records showed no trends responsible for bank erosion
in the upper reach. Sediment input to the upper reach has not changed significantly during the study period. Floodplain soils
are sandy, with low cohesion and are easily detached by lateral erosion. The degree of channel widening was positively correlated
with the percentage of bare ground on the streambanks and low bank stability ratings. Low bank stability ratings were, in
turn, strongly associated with high human use areas. Channel widening and bank erosion in the upper reach were due primarily
to destruction of riparian vegetation by human trampling and the effect of bridge constrictions on high flow, and secondarily
to poorly installed channel revetments. Several specific recommendations for river restoration were provided to park management. 相似文献
185.
Terrie K. Boguski Robert G. Hunt William E. Franklin 《Resources, Conservation and Recycling》1994,12(3-4)
Life cycle inventory (LCI) is becoming more widely used as a tool to evaluate the resource and energy use and the environmental releases associated with various products. The methodology for handling different recycling scenarios is also becoming increasingly important. Several different methods exist for handling recycling in an LCI. The method described in this paper uses mathematical models to show that the same basic equations can be used to handle a variety of recycling options for multi-product systems. 相似文献
186.
William Towers 《Journal of Environmental Planning and Management》1994,37(4):447-460
Patterns of sewage sludge disposal will undergo dramatic changes in the next decade because of recent EC legislation; land utilization is likely to increase as a result. The legislation as applied in the UK is discussed and the current situation in Scotland is outlined. A rule‐based risk assessment classification has been formulated and by applying it to the Scottish National Soils Inventory database, national and regional estimates of land availability for sludge utilization have been obtained. The relationship of these area estimates with the projected sludge volumes and the long‐term implications are discussed. In addition, the impact of potential policy changes are described. The need for incorporating objective strategic analyses of this type into the restructuring of the Scottish water industry is advocated. 相似文献
187.
188.
William H. Parker 《环境质量管理》1994,3(4):421-431
EG&G is a Fortune 200 company with annual sales of $2.7 billion. It designs and manufactures laboratory and field-test instruments and electronic and mechanical components for commercial customers. EG&G provides systems engineering, precision component manufacturing, and test-site operating and management services to many government agencies and laboratories. It employs 34,000 people worldwide. Recognizing the need to improve its business practices as they related to environmental excellence, EG&G initiated policies, procedures, and programs to establish itself as an environmentally responsible company. Waste reduction was designated priority number one in EGG's environmental program. Our major customers are also making waste reduction a high visibility program. For example, on August 3, 1993, the president signed Executive Order 12856 making pollution prevention at federal facilities a goal of this administration. This article describes the EG&G Waste Reduction Pays (WARP) program, developed for use by all its operating entities, and why it is a model program to implement Executive Order 12856. It also depicts how the implementation of the program at federal facilities differs, in some respects, from that at other EG&G operating units. 相似文献
189.
Martha W. Gilliland Lee Becker Ralph Cady Joe Gabig James Gilley Richard A. Kern Arley Larson Quang M. Nguyen William Powers Raymond Supalla 《Journal of the American Water Resources Association》1985,21(2):281-290
Substantial conflict exists over water management and allocation in the Platte River Basin of Nebraska. An interdisciplinary computer simulation model, representing the water quantity, water quality, environmental, and economic dimensions of the conflict, was developed in order to analyze the tradeoffs among allocation scenarios. Most importantly, decisionmakers and interest groups were involved in model development. Simulation results for a base case and two scenarios are presented. One scenario favors protection of instream flow for wildlife; the other favors water diversions for agriculture. Impacts of the instream flow scenario, as measured by the amount of land irrigated, groundwater levels, the amount of wildlife habitat for cranes and catfish, and net agricultural benefits did not differ greatly from those of the base case. However, impacts of the diversion scenario were substantial. On the negative side, instream flows and wildlife habitat declined an average of 39 percent; while, on the positive side, groundwater levels and net agricultural benefits each increased 6 percent. The modeling process was successful insofar as it promoted an understanding among the highly diverse interest groups of the systems nature of the Basin. One agreement on a water diversion schedule among three of the parties has been reached, partly as a result of this process. More comprehensive compromises have not yet been forged. Our experience, however, indicates that modeling success at the policymaking level depends more on the extent to which the policymakers understand the model than it does on model sophistication. 相似文献
190.
ABSTRACT: Variability in bedload-transport rates during constant water discharge is an inherent part of the bedload-transport process. Although this variability has been measured extensively in the laboratory, similar information generally is not available from field measurements. During a four-day period of nearly constant water discharge, four sets of consecutively collected bedload samples, ranging from 43 to 120 samples, were obtained at the same cross channel location using a standard 65-pound Helley-Smith bedload sampler. When the measured transport rates are converted to dimensionless rates and plotted as cumulative frequency distributions, they show good agreement with a theoretical probability distribution function of rates derived for the case of ripples on dunes. The distributions show that during constant water discharge individual measured rates at a fixed point vary from near zero to four times the mean rate, and 60 percent of the sampled rates will be less than the mean. Because of the large variation in transport rates that occurs at every location in the cross section, many observations are required to establish an accurate estimate of the mean rate at any given location. 相似文献