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101.
Wetlands are critical natural resources in developing countries where they perform a range of environmental functions and provide numerous socio-economic benefits to local communities and a wider population. In recent years, however, many wetlands throughout eastern Africa have come under extreme pressure as government policies, socio-economic change and population pressure have stimulated a need for more agriculturally productive land. Although wetland drainage and cultivation can make a key contribution to food and livelihood security in the short term, in the long term there are concerns over the sustainability of this utilization and the maintenance of wetland benefits. This article draws upon recent research carried out in western Ethiopia, which addressed the sustainability of wetland agriculture in an area of increasing food insecurity and population pressure. It discusses the impacts of drainage and cultivation on wetland hydrology and draws attention to local wetland management strategies, particularly those characterized by multiple use of wetlands, where agriculture exists alongside other wetland uses. The article suggests that where multiple wetland uses exist, a range of benefits can be sustained with little evidence of environmental degradation. Ways of promoting and empowering such sustainable wetland management systems are discussed in the context of the wider need for water security throughout the region. 相似文献
102.
Granger SJ Bol R Dixon L Naden PS Old GH Marsh JK Bilotta G Brazier R White SM Haygarth PM 《Journal of environmental monitoring : JEM》2010,12(5):1159-1169
A study was undertaken on drained and undrained 1 ha grassland lysimeters to assess the effectiveness of multiple novel tracing techniques in understanding how agricultural slurry waste moves from land to water. Artificial fluorescent particles designed to mimic the size and density of organic slurry particles were found to move off the grassland via inter-flow (surface + lateral through-flow) and drain-flow. Where both pathways were present the drains carried the greater number of particles. The results of the natural fluorescence and δ13C of water samples were inconclusive. Natural fluorescence was higher from slurry-amended lysimeters than from zero-slurry lysimeters, however, a fluorescence decay experiment suggested that no slurry signal should be present given the time between slurry application and the onset of drainage. The δ13C values of >0.7 microm and <0.7 microm material in drainage were varied and unrelated to discharge. The mean value of >0.7 microm δ13C in water from the drain-flow pathways was higher from the lysimeter which had received naturally enriched maize slurry compared to the lysimeter which received grass slurry indicating a contribution of slurry-derived material. Values of <0.7 microm δ13C from the same pathway, however, produced counter intuitive trends and may indicate that different fractions of the slurry have different δ13C values. 相似文献
103.
Burger J Murray S Gaines KF Novak JM Punshon T Dixon C Gochfeld M 《Environmental monitoring and assessment》2006,112(1-3):35-52
Levels of 18 elements, including lead, mercury, selenium, and uranium, were examined in three species of snakes from an exposed
and reference site on the Department of Energy's Savannah River Site in South Carolina. We tested the hypotheses that there
were no differences as a function of species, and there were no difference between the exposed and control site for blood
and muscle (tail) samples for banded water snake (Nerodia fasciata), brown water snake (N. taxispilota) and cottonmouth (Akistrodon piscivorous). The banded water snakes collected were significantly smaller than the other two species. For blood, there were significant
species differences only for barium, copper, selenium, uranium and zinc, while for muscle tissue there were significant interspecific
differences in aluminum, arsenic, barium, cobalt, cesium, copper, iron, lead, mercury, manganese, strontium, vanadium and
zinc, suggesting that muscle tissue in the tail is a better indicator of potential interspecific differences. It is also easier
logistically to collect tail tissue than blood. Where one species had significantly higher levels than the other species in
muscle tissue levels, cottonmouth had higherlevels of five elements (aluminum, cobalt, lead, mercury, vanadium), brown water
snake had two (lead, strontium), and banded water snake had only barium. There were few significant differences between the
control and reference site for levels of blood, but several for muscle tissue. All three species had significantly higher
levels of arsenic and manganese at Tim's Branch than the reference site, and nickel and uranium were significantly higher
for banded watersnake and cottonmouth, the larger species. Individuals with high exposure of one element were exposed to high
levels of other elements. 相似文献
104.
Measuring conservation success beyond the traditional biological criteria: the case of conservation projects in Costa Rica,Mekong Valley,and Cameroon 下载免费PDF全文
Traditionally, the criteria used to measure conservation success or failure are based on biological factors. Biological factors include changes in the amount of targeted conserved species, biodiversity, and total area conserved. However, conservation efforts are not simply a matter of biological concern; environmental, political, social, and conflict pressures on different scales (ranging from local to global) also have strong influences on the outcome of conservation. These other factors can either pose threats to or enhance conservation, but are not addressed by current criteria. Using a proposed holistic rubric that includes interdisciplinary fields, this paper examines a set of conservation factors on different scales – ranging from local to global – to determine their importance in conservation. The paper analyses positive factor influences with more successful conservation and negative factor influences with less successful, or failed, conservation attempts. Neutral and non‐applicable factor influences are also identified, defined, and ranked as a standardization mechanism. The determination of success changed when the holistic rubric was applied to conservation projects in Costa Rica, Mekong Valley, and Cameroon. In the Costa Rica case study, conservation success for Guanacaste and Talamanca national parks is rated ‘moderately low’. In the case of Mekong Valley, conservation success is rated ‘low’ for Lower Mekong, ‘moderately low’ for Greater Annamites, and ‘low’ for Phong Nha‐Ke Bang national parks. Cameroon's Congo Basin and Sangha Tri‐National conservation efforts are both rated ‘low’, while Dja Faunal is rated ‘very low’. We conclude that if conservation efforts are to attain a high level of success, the strategy for global conservation must move away from the traditional biological approach, which focuses mainly on biological concerns, and embrace a holistic approach, which in addition to biological concerns, addresses environmental, political, social, and conflict pressures, which have strong influences on the outcomes of conservation. 相似文献
105.
de Vos J Dixon R Vermeulen G Gorst-Allman P Cochran J Rohwer E Focant JF 《Chemosphere》2011,82(9):1230-1239
The disposal and dumping of toxic waste is a matter of growing concern in developing countries, including South Africa. Frequently these countries do not possess access to gas chromatography-high resolution mass spectrometry (GC-HRMS) for the determination of persistent organic pollutants (POPs). This publication describes an alternative approach to the investigation of toxic waste using comprehensive gas chromatography coupled to time of flight mass spectrometry (GC × GC-TOFMS). The technology permits both comprehensive screening of toxic samples for numerous classes of organic pollutants and also quantitative analysis for the individual compounds. This paper describes the use of this technique by analysing samples obtained from a hazardous waste treatment facility in South Africa. After sampling and extraction the samples were analysed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and four dioxin-like non-ortho substituted polychlorinated biphenyls (PCBs). The quantitative values, as well as detection limits, obtained using the GC × GC-TOFMS methodology compares well with those obtained using GC-HRMS; the accepted benchmark technology for this analysis. Although GC × GC-TOFMS is not a target compound analytical technique (as is GC-HRMS), it is possible to obtain information on numerous other classes of organic pollutants present in the samples in one analytical run. This is not possible with GC-HRMS. Several different column combinations have been investigated for handling very complex waste samples and suggestions are presented for the most suitable combination. 相似文献
106.
William F. Vevers David R. Dixon Linda R.J. Dixon 《Environmental pollution (Barking, Essex : 1987)》2010,158(5):1702-1709
The effect of high hydrostatic pressures on the ecotoxicological profile of pollutants is an unexplored research area. Using Pomatoceros lamarcki as a surrogate organism for this eco-barotoxicological study, it was found that in a 48 h larval bioassay with water accommodated fractions (WAF) of crude oil of up to 15.1 mg L−1 (total hydrocarbon content) and hydrostatic pressures up to 300 bar (3000 m), an additive response was found (p < 0.001) rather than any synergism (p = 0.881). Comprehensive cytogenetic analysis of 6-h (15 °C) embryos exposed to WAF (0.19 mg L−1) at 100 bar showed no effects on mitotic fidelity or cell division rate over the 1 bar treatment. However, embryo's treated with the clastogen mitomycin-c at 100 bar exhibited a significant increase in mitotic aberrations over 1 bar treated as was the case with hypo/hypersaline treatments (p < 0.05). Conversely, an increase in hydrostatic pressure actually reduced the effects of spindle inhibition by the aneugen colchicine (p < 0.05). 相似文献
107.
Tilo Ziehn Nick S. Dixon Alison S. Tomlin 《Atmospheric environment (Oxford, England : 1994)》2009,43(37):5978-5988
A combined Lagrangian stochastic model with micro-mixing and chemical sub-models is used to investigate a reactive plume of nitrogen oxides (NOx) released into a turbulent grid flow doped with ozone (O3). Sensitivities to the model input parameters are explored for different source NOx scenarios. The wind tunnel experiments of Brown and Bilger (1996) provide the simulation conditions for the first case study where photolysis reactions are not included and the main uncertainties occur in parameters defining the turbulence scales, source size and reaction rate of NO with O3. Using nominal values of the parameters from previous studies, the model gives a good representation of the radial profile of the conserved mean scalar although slightly over predicts peak mean NO2 concentrations compared to the experiments. The high dimensional model representation (HDMR) method is used to investigate the effects of uncertainties in model inputs on the simulation of chemical species concentrations. For this scenario, the Lagrangian velocity structure function coefficient has the largest impact on simulated profiles. Photolysis reactions are then included in a chemical scheme consisting of eight reactions between species NO, O, O3 and NO2. Independent and interactive effects of 22 input parameters are studied for two source NOx scenarios using HDMR, including turbulence parameters, temperature dependant rate parameters, photolysis rates, temperature, fraction of NO in total NOx at the source and background ozone concentration [O3]. For this reactive case, the variance in the predicted mean plume centre is caused by parameters describing both physical (mixing time-scale coefficient) and chemical processes (activation energy for the reaction O3+NO). The variance in predicted plume centre and root mean square NO2 concentration , is strongly influenced by the fraction of NO in the source NOx, and to a lesser extent the mixing time-scale coefficient. Adjusting the latter gives improved agreement with the Brown and Bilger experiment. Some weak parameter interactions are observed. 相似文献
108.
Jennifer E. Dixon 《Journal of Environmental Planning and Management》1993,36(2):239-251
The Resource Management Act, passed in 1991, has significantly revised the practice of Environmental Impact Assessment (EIA) in New Zealand. In contrast to a previous emphasis on environmental impact reports of major projects, the new requirements call for environmental impact assessment of all resource consent applications and of all regional, district and city policies and plans. This signals a change directed at incorporating environmental considerations into day‐to‐day planning decisions, with the purpose of achieving sustainable management. The paper identifies and discusses some key issues which are critical for successful integration of EIA within a planning framework. 相似文献
109.
Mitigation and Adaptation Strategies for Global Change - 相似文献
110.
Greigh I. Hirata MD Marsha L. Matsunaga Arnold L. Medearis Patricia Dixon Lawrence D. Platt 《黑龙江环境通报》1990,10(8):507-512
A case of a prenatally recognized hepatic mesenchymal hamartoma is presented and the literature reviewed. These tumors are benign and usually present in early infancy with symptoms that are related to the mass effect on adjacent organs. Radiologic methods used in the past to image this tumor include angiography and ultrasound. However, there is no specific radiologic finding, and, therefore, the diagnosis is usually made during surgery. Once the tumor is removed, the prognosis is generally good. With the increasing use of high resolution ultrasound in prenatal diagnosis, this rare tumor should be considered in the differential diagnosis of any multicystic mass found in the fetal abdomen. The recognition of a mass should then alert the physician to the need for early neonatal intervention. 相似文献