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排序方式: 共有195条查询结果,搜索用时 609 毫秒
61.
The presence of human adenoviruses (HAdV) in recreational water might cause disease in the population upon exposure. HAdV detected by PCR could also serve as indicators of the virological water quality. In order to assess the applicability of HAdV to the evaluation of the faecal contamination in European bathing waters, a real-time quantitative PCR assay was used for the quantification of HAdV in 132 samples collected from 24 different recreational marine and freshwater sites in nine European countries. Selected samples presenting positive nested PCR results for HAdV were analyzed using quantitative PCR and 80 samples from a total of 132 produced quantitative results with mean values of 3.2 × 102 per 100 ml of water, being human adenovirus 41 the most prevalent serotype between the samples where adenovirus was typified. HAdV were quantified in samples from all 15 surveillance laboratories. Statistical analysis showed no homogeneous linear relation between HAdV and E. coli, intestinal enterococci or somatic coliphages concentrations in the tested samples when considering all the data together. Significant correlations between HAdV and at least one of the other indicators were observed only when data from individual laboratories were considered. The quantification of HAdV may provide complementary information in relation to the use of bacterial standards in the control of water quality in bathing water.  相似文献   
62.
In addition to causing domestic and regional environmental effects, many air pollutants contribute to radiative forcing (RF) of the climate system. However, climate effects are not considered when cost-effective abatement targets for these pollutants are established, nor are they included in current international climate agreements. We construct air pollution abatement scenarios in 2030 which target cost-effective reductions in RF in the EU, USA, and China and compare these to abatement scenarios which instead target regional ozone effects and particulate matter concentrations. Our analysis covers emissions of PM (fine, black carbon and organic carbon), SO2, NOx, CH4, VOCs, and CO. We find that the effect synergies are strong for PM/BC, VOC, CO and CH4. While an air quality strategy targeted at reducing ozone will also reduce RF, this will not be the case for a strategy targeting particulate matter. Abatement in China dominates RF reduction, but there are cheap abatement options also available in the EU and USA. The justification for international cooperation on air quality issues is underlined when the co-benefits of reduced RF are considered. Some species, most importantly SO2, contribute a negative forcing on climate. We suggest that given current knowledge, NOx and SO2 should be ignored in RF-targeted abatement policies.  相似文献   
63.
According to the World Health Organization (WHO), indoor air pollution (IAP) from the use of solid fuels in households in the developing world is responsible for more than 1.6 million premature deaths each year, whereof 0.42 million occur in China alone. We argue that the methodology applied by WHO--the so-called fuel-based approach--underestimates the health effects, and suggest an alternative method. Combining exposure-response functions and current mortality and morbidity rates, we estimate the burden of disease of IAP in China and the impacts of three abatement scenarios. Using linear exposure-response functions, we find that 3.5 [0.8-14.7 95% CI] million people die prematurely due to IAP in China each year. The central estimate constitutes 47% of all deaths in China. We find that modest changes in the use of cooking fuels in rural households might have a large health impact, reducing annual mortality by 0.63 [0.1-3. 2 95% CI] million. If the indoor air quality (IAQ) standard set by the Chinese government (150 microg PM(10)/m(3)) was met in all households, we estimate that 0.9 [0.2-4.8] million premature deaths would be avoided in urban areas and 2.8 [0.7-12.4] million in rural areas. However, in urban areas this would require improvements to the outdoor air quality in addition to a complete fuel switch to clean fuels in households. We estimate that a fuel switch in urban China could prevent 0.7 [0.2-4.8] million premature deaths. The methodology for exposure assessment applied here is probably more realistic than the fuel-based approach; however, the use of linear exposure-response relationships most likely tends to overestimate the effects. The discrepancies between our results and the WHO estimates is probably also explained by our use of "all-cause mortality" which includes important causes of death like cardiovascular diseases, conditions known to be closely associated with exposure to particulate pollution, whereas the WHO estimate is limited to respiratory diseases.  相似文献   
64.
This paper identifies the coalitions involved in the topic of shale oil and gas development in India and identifies the circumstances surrounding a change in policy in 2013 by the Ministry of Petroleum and Natural Gas to promote shale exploration. Using the Advocacy Coalition Framework as the theoretical lens, the data are collected primarily from newspaper articles from 2010 to 2015 to identify coalitions, including actors’ positions, priorities, and interactions. The findings show the presence of a dominant advocacy coalition in favor of shale oil and gas development with priorities about energy security and a regulatory framework. The findings indicate some internal coalition disagreement, but stronger internal coalition agreement. Policy change was preceded by a spike in disagreement internal to the dominant coalition. This paper shows how a change in a dominant coalition can precede a change in policy, offers a replicable method of identifying and measuring coalitions via newspaper content analysis, provides a rare application of the Advocacy Coalition Framework outside of North America and Western Europe, and provides evidence of support for shale oil and gas development in India.  相似文献   
65.
Voie OA  Johnsen A  Rossland HK 《Chemosphere》2002,46(9-10):1367-1372
Accumulation of polychlorinated biphenyls (PCBs) in blue mussels (Mytilus edulis) and semipermeable membrane devices (SPMDs) was still high after the removal of PCB contaminated sediments from a Norwegian fjord by dredging. The accumulation of low chlorinated PCB congeners with a low octanol water-partitioning coefficient (Kow) in blue mussels and SPMDs was higher than for the highly chlorinated congeners with a high Kow. The accumulation of low chlorinated congeners was also higher in a lightly contaminated area compared to a highly contaminated area. That dredging the contaminated sediments was unsuccessful in lowering PCB levels in the biota may be for the following reasons: (1) Due to the low solubility of PCBs in the water it is possible that a decrease in the sediment concentration of PCB would leave the water concentrations of PCB unchanged. (2) Removal of the fine organic sediments may also play an important role, since a seabed with coarse inorganic material has a lesser ability to bind PCB. (3) The dredging may whirl up fine contaminated particles that eventually settles on the seabed producing a thin contaminated sediment layer that determine the water concentration. (4) Bioaccumulation in blue mussels and in the SPMDs occurs mostly from PCB dissolved in the water column. Since the water concentration of PCB is unchanged by the dredging, the accumulation in SPMDs and mussels is the same as before dredging. Further monitoring need to be carried out to report the long-term effect of the dredging.  相似文献   
66.
Hulvey KB  Zavaleta ES 《Ecology》2012,93(2):378-388
The effects of declining plant biodiversity on ecosystem processes are well studied, with most investigations examining the role of species richness declines rather than declines of species abundance. Using grassland mesocosms, we examined how the abundance of a native, resident species, Hemizonia congesta (hayfield tarweed), affected exotic Centaurea solstitialis (yellow starthistle) invasion. We found that progressive H. congesta abundance declines had threshold effects on invasion resistance, with initial declines resulting in minor increases in invasion and subsequent declines leading to accelerating increases in invader performance. Reduced invasion resistance was explained by increased resource availability as H. congesta declined. We also found evidence that resident abundance might indirectly affect invasion by mediating invader impact on resident competitors; C. solstitialis disproportionately reduced H. congesta biomass in low-abundance rather than high-abundance populations. H. congesta's direct and indirect effects on invasion resistance illustrate that an individual species' declining abundance can have accelerating, deleterious effects on ecosystem functions of conservation value.  相似文献   
67.
One potential trade-off that bold individuals face is between increased predation risks and gains in resources. Individuals experiencing high predation and hungry individuals (or individuals with low body condition) are predicted to show increased boldness. We examined one behavioral trait previously reported to be associated with boldness (the time individual fish needed to emerge from shelter) in various populations of mollies (Poecilia spp.). Our study system included several southern Mexican surface streams with high piscine predation and high food availability, sulfidic surface streams with high avian predation, in which the inhabiting fish show reduced body condition, and a sulfidic cave, where predation and body condition are low. Our comparison revealed very short times to emerge from the start box in populations from non-sulfidic streams. In sulfidic habitats (whether surface or cave), it took individual Poecilia mexicana considerably longer to emerge from the start box, and the same difference was also found in an independent comparison between P. mexicana and the closely related, highly sulfide-adapted Poecilia sulphuraria. Fish reared under common garden conditions (in the absence of predators and hydrogen sulfide) showed intermediate boldness scores to the extremes observed in the field. Our data thus indicate that (a) boldness is shaped by environmental conditions/experiential effects, but is not heritable, (b) predation affects boldness in the predicted direction, but (c) low body condition leads to reduced boldness. Extremophile Poecilia spp. spend most of their time surfacing to survive under sulfidic and hypoxic conditions, which exposes them to increased levels of predations, but the fish forage on the bottom. Hence, in this system, increased boldness does not increase foraging success. We argue that energy limitation favors reducing energetically costly behaviors, and exploring novel environments may be just one of them.  相似文献   
68.
Jacobs MW  Sherrard KM 《Ecology》2010,91(12):3598-3608
The presumed trade-off between offspring size and quality predicted by life history theory is often invoked to explain the wide range of propagule sizes observed in animals and plants. This trade-off is broadly supported by intraspecific studies but has been difficult to test in an interspecific context, particularly in animals. We tested the fitness consequences of offspring size both intra- and interspecifically for seven species of ascidians (sessile, suspension-feeding, marine invertebrates) whose offspring volumes varied over three orders of magnitude. We measured two major components of fitness, juvenile growth rates and survival, in laboratory and field experiments encompassing several food conditions. Contrary to the predictions of life history theory, larger offspring size did not result in higher rates of growth or survival, and large offspring did not perform better under nutritional stress, either intraspecifically or interspecifically. In fact, two of the four species with small offspring grew rapidly enough to catch up in size to the species with large offspring in as little as eight weeks, under wild-type food conditions. Trade-offs between growth potential and defense may overwhelm and obscure any trade-offs between offspring size and survival or growth rate. While large initial size may still confer a competitive advantage, we failed to detect any consequences of interspecific variation in initial size. This implies that larger offspring in these species, far from being inherently superior in growth or survival, require compensation in other aspects of life history if reproductive effort is to be efficient. Our results suggest that the importance of initial offspring size is context dependent and often overestimated relative to other life history traits.  相似文献   
69.
Forested riparian corridors are thought to minimize impacts of landscape disturbance on stream ecosystems; yet, the effectiveness of streamside forests in mitigating disturbance in urbanizing catchments is unknown. We expected that riparian forests would provide minimal benefits for fish assemblages in streams that are highly impaired by sediment or hydrologic alteration. We tested this hypothesis in 30 small streams along a gradient of urban disturbance (1–65% urban land cover). Species expected to be sensitive to disturbance (i.e., fluvial specialists and “sensitive” species that respond negatively to urbanization) were best predicted by models including percent forest cover in the riparian corridor and a principal components axis describing sediment disturbance. Only sites with coarse bed sediment and low bed mobility (vs. sites with high amounts of fine sediment) had increased richness and abundances of sensitive species with higher percent riparian forests, supporting our hypothesis that response to riparian forests is contingent on the sediment regime. Abundances of Etheostoma scotti, the federally threatened Cherokee darter, were best predicted by models with single variables representing stormflow (r2 = 0.34) and sediment (r2 = 0.23) conditions. Lentic-tolerant species richness and abundance responded only to a variable representing prolonged duration of low-flow conditions. For these species, hydrologic alteration overwhelmed any influence of riparian forests on stream biota. These results suggest that, at a minimum, catchment management strategies must simultaneously address hydrologic, sediment, and riparian disturbance in order to protect all aspects of fish assemblage integrity.  相似文献   
70.
The goal of restoring environmental health and qualities to Hamilton Harbour Great Lakes Area of Concern, an embayment at the western end of Lake Ontario, is considered to be achievable by the year 2015. Restoring Hamilton Harbour is a dynamic process that relies heavily on research and monitoring to direct remediation efforts. Three principle means of coordinating this research and monitoring include: research and monitoring workshops; a monitoring catalogue outlining both government and nongovernment initiatives; and an annual report written by a local community group. These tools increase the effectiveness of remedial actions by: (i) improving stakeholders' ability to track trends; (ii) allowing program decision-makers to utilize adaptive management techniques to continuously modify programs based on new results; (iii) integrating interdisciplinary fields, and (iv) increasing accountability. This paper describes in detail these tools used for coordinating research and monitoring in implementing the Remedial Action Plan of the Hamilton Harbour Great Lakes Area of Concern, along with lessons learned to assist other implementers who are considering similar programs.  相似文献   
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