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611.
Christopher R. Blattel Karl W.J. Williard Sara G. Baer James J. Zaczek 《Journal of the American Water Resources Association》2005,41(2):301-307
ABSTRACT: Forest and grass riparian buffers have been shown to be effective best management practices for controlling nonpoint source pollution. However, little research has been conducted on giant cane [Arundinaria gigantea (Walt. Muhl.)], a formerly common bamboo species, native to the lower midwestern and southeastern United States, and its ability to reduce nutrient loads to streams. From May 2002 through May 2003, orthophosphate or dissolved reactive phosphate (DRP) concentrations in ground water were measured at successive distances from the field edge through 12 m of riparian buffers of both giant cane and mixed hardwood forest along three streams draining agricultural land in the Cache River watershed in southern Illinois. Giant cane and mixed hardwood forest did not differ in their DRP sequestration abilities. Ground water DRP concentrations were significantly reduced (14 percent) in the first 1.5 m of the buffers, and there was an overall 28 percent reduction in DRP concentration by 12 m from the field edge. The relatively low DRP reductions compared to other studies could be attributed to high DRP input levels, narrow (12 m) buffer lengths, and/or mature (28 to 48 year old) riparian vegetation. 相似文献
612.
Studies of two samples of 24 selected local planning authorities (LPAs) in the UK were undertaken to determine the effect of environmental assessment (EA) regulations on planning practice during their first 18 months of operation. EA has been integrated into the UK planning system without significant recourse to the courts and many LPAs regarded EA as a worthwhile and helpful procedure. However, several LPAs did not consider whether to request EA for projects that might be likely to have significant impacts and some LPAs did not follow statutory and recommended consultation procedures. LPAs did not evaluate environmental statements systematically and their quality was often unsatisfactory. However, mitigation of environmental impacts took place in many cases though two‐fifths of the 20 determined applications involving EA were refused. Half the decisions took longer than the 16‐week time limit. While practice is evolving as experience is gained, there is obvious scope for further improvement and suggestions are made to enhance the contribution of EA to the planning system. 相似文献
613.
Potential of the Conservation Reserve Program to control agricultural surface water pollution 总被引:1,自引:0,他引:1
Christopher L. Lant 《Environmental management》1991,15(4):507-518
The Conservation Reserve Program (CRP), initiated by the Conservation Title of the Food Security Act of 1985, is the primary
federal program to control nonpointsource pollution in agricultural watersheds of the United States. However, the program
is designed primarily to reduce soil erosion rather than to retire croplands in a manner optimal for controlling runoff of
sediment and associated pollutants. This study estimates potential enrollment of streamside and floodplain croplands in this
ten-year retirement program in order to gauge the potential of the CRP as a water-quality improvement policy. A contingent
choice survey design was employed in Fayette County, Illinois, to demonstrate that there is substantial potential for retirement
of streamside and floodplain croplands in the CRP. Enrollments in each program climb from less than 6% to over 83% of eligible
croplands as the annual rental rate is increased from $20 to $200/acre. Potential retirement of streamside and floodplain
croplands declines, however, if tree planting, drainage removal, or a 20-year contract are required. The potential of a CRP-based
water-quality program to improve water quality and aquatic ecosystems in agricultural watersheds is thus substantial but constrained
by the economic trade-offs that farmers make between crop production and conservation incentives in determining the use of
their riparian lands. 相似文献
614.
615.
Christopher D. Wren 《Environmental monitoring and assessment》1986,6(2):127-144
Wild mammals can be valuable biological monitors of environmental gradients of metal concentrations. The choice of a particular species for a biological monitor must be based upon the circumstances of each study including species availability, the metals to be examined, area, and the study objectives and priorities. Ideally, a biological monitoring study should be designed to obtain and make use of the optimum amount of available information by complementing existing environmental studies, or through the simultaneous collection of other environmental data. 相似文献
616.
Larval behaviors are increasingly recognized as determining factors in the water column distribution and subsequent settlement patterns of marine invertebrates. In particular, larvae within one or two body lengths of the seafloor (= interaction zone) may be better able to control their settlement location or respond to settlement cues. Here we examine temporal changes the behavior of larval oysters (Crassostrea virginica) swimming in the bottom 1 cm of a flume boundary layer. In addition, we present a novel behavior, called "dive-bombing", that consists of an abrupt downward acceleration and subsequent contact with the bottom. Larvae were divided into two arbitrarily chosen size classes (those retained on a 153 m screen and those retained on a 202 m screen) to separate those that developed eyespots from those that did not develop eyespots. Behavior in a flume boundary layer was monitored from day 15 to day 21 post-fertilization. In the larger size class, the percentage of oyster larvae within close proximity (1 to 2 body lengths) of the flume bed steadily increased from 6% to 28% with larval age. In contrast, if larvae were restricted from reaching larger sizes through sieving this proportion remained constant at 12%. Dive-bombing was exhibited by a constant 4% of the larval population regardless of age or size. Kinematic analysis of swimming paths shows dive-bombing to be distinct from other swimming behaviors and from the passive sinking of dead larvae. For example, vertical acceleration at the initiation of dive-bombing is some 30–400 times that measured for other live or dead larvae. Our results indicate that larvae are capable of rapid acceleration and that they may be able to control their approach to the bottom under a much wider range of conditions than had previously been suspected.Communicated by P.W. Sammarco, Chauvin 相似文献
617.
Christopher Snary 《Journal of Environmental Planning and Management》2002,45(2):267-283
With a view to suggesting ways in which we might arrive at a more socially acceptable waste management facility siting process, this paper considers the effectiveness of a more innovative approach to risk communication for a planned municipal waste-to-energy incinerator in Portsmouth, Hampshire, UK. The risk communication programme involved a contact group process designed to enable key members of the local community to participate in structured and informed discussions about the proposal before it was submitted as a planning application to the competent authority. The paper concludes that the communication model was dominated by the findings of technical assessments and that it provided only limited opportunities for interested stakeholders to participate fairly and competently in the development process. 相似文献
618.
Using public procurement to achieve social outcomes 总被引:3,自引:0,他引:3
Christopher McCrudden 《Natural resources forum》2004,28(4):257-267
The use of public procurement to achieve social outcomes is widespread, but detailed information about how it operates is often sketchy and difficult to find. This article is essentially a mapping exercise, describing the history and current use of government contracting as a tool of social regulation, what the author calls the issue of ‘linkage’. The article considers the popularity of linkage in the 19th century in Europe and North America, particularly in dealing with issues of labour standards and unemployment. The use of linkage expanded during the 20th century, initially to include the provision of employment opportunities to disabled workers. During and after World War II, the use of linkage became particularly important in the United States in addressing racial equality, in the requirements for non‐discrimination in contracts, and in affirmative action and set‐asides for minority businesses. Subsequently, the role of procurement spread both in its geographical coverage and in the subject areas of social policy that it was used to promote. The article considers examples of the use of procurement to promote equality on the basis of ethnicity and gender drawn from Malaysia, South Africa, Canada, and the European Community. More recently, procurement has been used as an instrument to promote human rights transnationally, also by international organizations such as the International Labour Organisation. The article includes some reflections on the relationship between ‘green’ procurement, ‘social’ procurement, and sustainable development, and recent attempts to develop the concept of ‘sustainable procurement.’ 相似文献
619.
Yuri Mun Christopher G. Uchrin 《Journal of the American Water Resources Association》2004,40(1):229-239
ABSTRACT: The discrete heterogeneity of fracture distribution and hydraulic discontinuity are the primary difficulties in the modeling of flow in fractured media. The equivalent porous medium (EPM) approach, however, which has been frequently applied to simulate flow in fractured media due to its ease of use, ignores this. This practice results in some severe limitations such as hydraulic head averaging and an inability to handle preferred fluid pathways. The PMF package (a Preprocessor to MODFLOW for Fractured media) was developed employing percolation theory to address these limitations and to utilize the simplicity of the EPM approach at the same time. This preprocessor was applied to a fractured rock aquifer around Cranberry Lake in northern New Jersey. The calibration using hydraulic head observations, validation using water balance, and evaluation using residuals show that the model generated by the PMF package can provide a superior simulation of ground water flow to the EPM approach. 相似文献
620.
Dan Binkley George G. Ice Jason Kaye Christopher A. Williams 《Journal of the American Water Resources Association》2004,40(5):1277-1291
ABSTRACT: Seventy to eighty percent of the water flowing in rivers in the United States originates as precipitation in forests. This project developed a synoptic picture of the patterns in water chemistry for over 300 streams in small, forested watersheds across the United States. Nitrate (NO3?) concentrations averaged 0.31 mg N/L, with some streams averaging ten times this level. Nitrate concentrations tended to be higher in the northeastern United States in watersheds dominated by hardwood forests (especially hardwoods other than oaks) and in recently harvested watersheds. Concentrations of dissolved organic N (mean 0.32 mg N/L) were similar to those of NO3~, whereas ammonium (NH4+) concentrations were much lower (mean 0.05 mg N/L). Nitrate dominated the N loads of streams draining hardwood forests, whereas dissolved organic N dominated the streams in coniferous forests. Concentrations of inorganic phosphate were typically much lower (mean 12 mg P/L) than dissolved organic phosphate (mean 84 mg P/L). The frequencies of chemical concentrations in streams in small, forested watersheds showed more streams with higher NO3? concentrations than the streams used in national monitoring programs of larger, mostly forested watersheds. At a local scale, no trend in nitrate concentration with stream order or basin size was consistent across studies. 相似文献