排序方式: 共有4条查询结果,搜索用时 15 毫秒
1
1.
Krystyna A. Stave 《Journal of the American Water Resources Association》2001,37(5):1369-1379
ABSTRACT: This paper examines the co‐evolution of the Las Vegas, Nevada metropolitan area, Las Vegas Wash ecosystem‐a downstream riparian wetland‐and Wash management as a case of urban‐environment dynamics. Since Las Vegas Wash provides the primary drainage for Las Vegas, changes in the urban system lead to changes in the Wash and its ecosystem. The population of the drainage area has grown from approximately 1,000 people in 1900 to more than 1.3 million in 2000. This phenomenal population growth led to increased Wash flow, from less than .03 m3/sec (1 ft3/sec) to over 7.4 m3/sec (260 ft3/sec), and consequent ecological changes from a nearly dry wash to a rich wetland, and now to an eroded system. As the Wash ecosystem changed, valuation of Wash characteristics by residents and resource managers also changed, shifting the focus of management and use, which ultimately led to further ecosystem changes. Reciprocal relationships among human activity, environmental change, and management in this urban area highlight the need for a comprehensive and dynamic systems perspective and adaptive approaches in urban environmental management and make this a particularly compelling case study. This paper describes a conceptual systems framework for adaptive urban‐environment management derived from this case. 相似文献
2.
DRAGANA MUTAVDŽIĆ IVAN BRNARDIĆ MARIJA KAŠTELAN-MACAN 《Journal of environmental science and health. Part. B》2013,48(7):1085-1101
The purpose of this investigation was to determine the influence of humic acids (HA) and Ca-montmorillonite (CaM) on the solid-phase extraction (SPE) efficiency of atrazine, alachlor and α-cypermethrin from water samples at various pH-values. The nature and intensity of binding of the studied pesticides to CaM were determined by X-ray diffraction analysis and termogravimetric analysis (TGA) test. The studied pesticides eluted from discs were analysed by thin-layer chromatography (TLC). The effects of CaM and humic acid were generally pH-dependent and acted independently in extraction efficiency influence. Lower recovery of pesticides was observed at higher pH values when CaM was ≥0.1 g and was attributed to greater dispersion of clay, increased surface area and subsequent adsorption. Concentrations of dissolved organic carbon (DOC) in humic acid had less effect on the extraction efficiency when water was at pH 8 compared to water at pH 2, which was probably due to greater nonpolar interactions of the pesticides to the charge-neutralized humic acid molecule. 相似文献
3.
A system dynamics model to facilitate public understanding of water management options in Las Vegas,Nevada 总被引:12,自引:0,他引:12
Stave KA 《Journal of environmental management》2003,67(4):303-313
Water managers increasingly are faced with the challenge of building public or stakeholder support for resource management strategies. Building support requires raising stakeholder awareness of resource problems and understanding about the consequences of different policy options. One approach that can help managers communicate with stakeholders is system dynamics modeling. Used interactively in a public forum, a system dynamics model can be used to explain the resource system and illustrate the effects of strategies proposed by managers or suggested by forum participants. This article illustrates the process of building a strategic-level system dynamics model using the case of water management in Las Vegas, Nevada. The purpose of the model was to increase public understanding of the value of water conservation in Las Vegas. The effects of policies on water supply and demand in the system are not straightforward because of the structure of the system. Multiple feedback relationships lead to the somewhat counterintuitive result that reducing residential outdoor water use has a much greater effect on water demand than reducing indoor water use by the same amount. The model output shows this effect clearly. This paper describes the use of the model in research workshops and discusses the potential of this kind of interactive model to stimulate stakeholder interest in the structure of the system, engage participant interest more deeply, and build stakeholder understanding of the basis for management decisions. 相似文献
4.
There is concern that elevated levels of selenium found in the source water of a newly formed wetland park in Las Vegas, Nevada,
may have detrimental effects on local wildlife. In this study, we collected and analyzed water samples monthly for a three
year period from the inflow and outflow of the system. We also gathered dominant aquatic plants and selected terrestrial plants
and analyzed the water and plant tissues (root, shoot, leaf and flower) for selenium by high resolution Inductively Coupled
Plasma Mass Spectrometer. Except for storm events and the introduction of an alternative low selenium content source water
during summer low-flow conditions, selenium in the water was relatively stable. The concentration in the outflow tended to
be slightly lower than the inflow. Concentrations of selenium in the dominant plant taxa in this wetlands were typical of
ecosystems in the western United States and varied by taxa, tissue type, localized conditions (e.g., contact with selenium-laden
water), and to a lesser extent, seasons. Selenium in the aquatic plant spiny naiad (Najas marina) was relatively high and may pose an ecological risk to wildlife during the late spring and summer. Additional work is underway
investigating aquatic food chain accumulations of selenium as well as mass balance of selenium in the system. 相似文献
1