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941.
Sandy beaches represent typical venues for recreation and tourism worldwide, as well as part of the lifestyle and identity of coastal communities. Their overexploitation, however, threatens their survival. Especially in urban areas, beach management requires balancing needs by different users and obligations to protect beach functions, including conservation. In light of this, research about the human dimension of beach ecosystems has been advanced as a way to assist planning and decision making in beach management. This study assessed beachgoers' perceptions of sandy beach conditions in South Africa, by means of a questionnaire survey. The effects of demographic profile, travelling habits, motivations to visit, and recreational preferences on beachgoers' perceptions of beach conditions were tested. Beachgoers shared a general concern for the wellbeing of sandy beaches, with particular reference to the state of biodiversity and conservation. They also gave great importance to the values underlying beach ecosystems. Three motivations to visit groups and four recreational preferences types were identified. Demography, travelling habits, motivations to visit, and recreational preferences all influenced perceptions of beach conditions. The results from this study were used to draw management recommendations, with particular attention towards the promotion of conservation while also maintaining the recreational quality of urban sandy beaches. The results also highlighted the relevance of considering users' views as a tool in decision-making processes in Integrated Coastal Zone Management. 相似文献
942.
Environmental Fluid Mechanics - Turbulent mixing processes in deep alpine Lake Garda (I) have not extensively been observed. Knowledge about drivers of turbulent fluxes are important for insights... 相似文献
943.
To gain insight in the startup of an incinerator, this article deals with piloted ignition. A newly developed model is described to predict the piloted ignition times of wood, PMMA and PVC. The model is based on the lower flammability limit and the adiabatic flame temperature at this limit. The incoming radiative heat flux, sample thickness and moisture content are some of the used variables. Not only the ignition time can be calculated with the model, but also the mass flux and surface temperature at ignition. The ignition times for softwoods and PMMA are mainly under-predicted. For hardwoods and PVC the predicted ignition times agree well with experimental results. Due to a significant scatter in the experimental data the mass flux and surface temperature calculated with the model are hard to validate. The model is applied on the startup of a municipal waste incineration plant. For this process a maximum allowable primary air flow is derived. When the primary air flow is above this maximum air flow, no ignition can be obtained. 相似文献
944.
Nicolaas G. J. Jaspers Magna van der Kraan Peter C. M. L. Linssen Milan Maçek Eva Seemanová Wim J. Kleijer 《黑龙江环境通报》1990,10(10):667-674
Prenatal diagnosis was performed in two pregnancies at risk of the Nijmegen breakage syndrome. In one pregnancy, an affected fetus was diagnosed by demonstration of radioresistant DNA synthesis, using autoradiographic detection of incorporated tritiated thymidine in cultured chorionic villus cells. The diagnosis was confirmed in fetal skin fibroblasts. In the other case, the fetus appeared unaffected. Using the same procedure, unaffected fetuses were predicted from chorionic villus cells in two pregnancies at risk of ataxia telangiectasia, which is another genetic disorder showing the feature of radioresistant DNA synthesis. The present biochemical method for prenatal detection of Nijmegen breakage syndrome and ataxia telangiectasia can be used as a simplified alternative to the cytogenetic procedures reported earlier for ataxia telangiectasia. 相似文献
945.
946.
The Saldanha-Langebaan coastal zone forms an integral part of the South African coastal resource base. As elsewhere in the world, an acute need exists to balance development and economic growth and conservation in the coastal zone as an exploitable resource frontier area. Vegetated buffers and greenways are conservation concepts that have been used with great success in such conservation efforts. They are applied in the study area through the use of a Geographic Information System (GIS) as spatial decision-support system to legitimize the demarcation of a vegetated buffer zone. The method of multicriteria evaluation, as applied here, incorporates public decision-making in constructing an objective model for buffer zone demarcation. Representatives from interested and affected parties participated in model construction and calibration, resulting in the spatial delimitation of a multifunctional vegetated buffer. It conforms to a range of functional criteria and can serve as an environmental element in coastal conservation planning frameworks. 相似文献
947.
Tal Y Schwartsburd B Nussinovitch A van Rijn J 《Environmental pollution (Barking, Essex : 1987)》2001,112(2):99-106
The relative abundance of the denitrifier, Pseudomonas sp. JR12, was examined in an alginate-based entrapment complex under non-sterile, denitrifying conditions. Immuno-labeling of the Pseudomonas inoculant followed by flow cytometry (FCM) was used for determination of the relative abundance of this bacterium under the various incubation conditions. Additional information on the relative abundance of the inoculant was obtained by a quantitative enzyme-linked immunosorbent assay (ELISA) and results obtained by FCM and ELISA were compared. Ambient nitrate levels controlled the successful, long-term proliferation of the inoculant. At low ambient nitrate levels, Pseudomonas sp. remained the dominant microorganism during incubation. Higher ambient nitrate concentrations, attained by either decreasing the inoculum size of Pseudomonas sp. or raising inlet nitrate concentrations of the medium supplied to the incubation vessels, resulted in a gradual shift toward other, nitrite-accumulating denitrifiers. Thus far, most studies on the use of entrapped microorganisms for bioremediation purposes have been conducted under controlled laboratory conditions. Based on this study, conducted under non-sterile laboratory conditions, it is concluded that in-situ bioremediation using entrapped target microorganisms is bound to fail without a proper understanding of the factors that cause the target microorganism to out-compete undesired microbial invaders. Furthermore, based on the close agreement between the two detection methods used, it is concluded that flow cytometry provides a rapid and accurate tool for the detection of the relative abundance of immuno-labeled target organisms in heterogeneous microbial populations. 相似文献
948.
In Costa Rica as many other tropical countries, the disposal problem of agricultural wastes is widely recognized but efforts to find solutions are not equal for different sectors. This study describes the situation of major agricultural residues in Costa Rica, identifying the activities with higher amounts produced and, the potential use of these residues in fish feeds. In Costa Rica, during the 1993-1994 production season, major agricultural sectors (crop and livestock) generated a total amount of 3.15-3.25 million MT of residues (classified in by-products: used residues and wastes: not used residues). Some residues are treated to turn them into valuable items or to diminish their polluting effects (e.g., the so-called by-products). About 1.56-1.63 million MT of by-products were used for different purposes (e.g. fertilization, animal feeding, fuel, substrates in greenhouses). However, the remainder (1.59-1.62 million MT) was discharged into environment causing pollution. About 1.07-1.2 million MT wastes came from major crop systems (banana, coffee, sugarcane and oil palm) whereas the remainder came from animal production systems (porcine and poultry production, slaughtering). These data are further compared to residues estimates for the 2001-2002 production season coming from the biggest crops activities. Unfortunately, most of the studied wastes contain high levels of moisture and low levels of protein, and also contain variable amounts of antinutritional factors (e.g., polyphenols, tannins, caffeine), high fibre levels and some toxic substances and pesticides. All these reasons may limit the use of these agricultural wastes for animal feeding, especially in fish feeds. The potential use of the major vegetable and animal residues in fish feeds is discussed based on their nutritional composition, on their amount available over the year and on their pollution risks. Other constraints to use these wastes in fish feeds are the extra costs of drying and, in most cases, of transportation from several dispersed locations. It was stated that most interesting wastes are rejected green banana and coffee pulp. 相似文献
949.
Automated and continuous redox potential measurements in soil 总被引:2,自引:0,他引:2
Vorenhout M van der Geest HG van Marum D Wattel K Eijsackers HJ 《Journal of environmental quality》2004,33(4):1562-1567
Redox potential (Eh) describes the electrical state of a matrix. In soils, Eh is an important parameter controlling the persistence of many organic and inorganic compounds. A popular, but also criticized, manual measuring method makes use of a small tip of Pt placed on a copper wire that is placed in the soil; a reference electrode is placed in the same soil at a fixed distance. Fluctuations in redox potential values measured in the soil can be very large and depth-dependent. This will be overlooked when making single-point measurements. We developed the datalogger Hypnos 2.0 for continuous redox potential and temperature measurements at various depths in the soil and without disturbance of the site. Hypnos is field-deployable, relatively cheap, and runs on batteries. The datalogger can use a "sleep mode" between sampling events. In sleep mode, there is no constant voltage on the Pt wire or the reference electrode, but there is only a short pulse during sampling. We did not measure an effect of this short pulse on the measured redox potential. In sandy soils in mesocosms and in a salt marsh soil we measured changes in the Eh as large as from -400 to +100 mV within 4 d, and daily cycles of 200 mV. Both absolute redox potential values and their diurnal variations were depth-dependent. Because single redox measurements are insufficient in describing redox conditions in some soil systems, Hypnos can be a powerful tool when studying the effects of fluctuating redox conditions on metal availability and pollutant degradation. 相似文献