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181.
Freshly deposited surface sediments from the Alexandria coastal zone were collected and analysed in 1995 for their trace metal concentrations. Metal concentrations in the sediments vary between sites within a wide range for copper, zinc, iron, lead, chromium and cadmium. the statistical analysis between the metal concentrations and the different constituents (organic carbon, total nitrogen, silt, clay and total iron) showed significant correlations. the enrichment factors for the sediments ranged between 3 and 4-fold for copper, chromium and zinc and reached up to 9-fold for lead and 113-fold for cadmium. the highest index for cadmium and lead may be attributed to the anthropogenic inputs from the surrounding area, where they are highest in lower discharge areas.  相似文献   
182.
In spite of the advantages of Vetiver grass in light of environmental aspects, this plant is not used in the Mediterranean region. The objectives of the present study were: (i) to elucidate growth parameters and establishment of Vetiver under Mediterranean conditions suitable for its various environmental applications; and (ii) to develop management practices for growing vetiver under Mediterranean conditions. In greenhouse experiments conducted under controlled conditions it was found that, in general, increasing the minimum/maximum temperatures to 21-29 degrees C significantly increased plant height. In the Mediterranean region, this range of air temperatures is obtained mainly during the summer, from June to September. For air temperatures up to 15-23 degrees C the effect of day length on plant height was insignificant, whereas in air temperature >15-23 degrees C, the plant heights under long day conditions were significantly higher than under short day. The number of sprouts per plant increased exponentially with increasing air temperature, and was not significantly affected by the day length at any air temperature range. In open fields, the heights of irrigated vetiver plants were significantly higher than those of rain-fed plants. It was concluded that, once they were established, vetiver plants could survive the dry summer of the Mediterranean region under rain-fed conditions, but they would be shorter than under irrigation. Cutting or burning of the plant foliage during the spring did not improve the survival of vetiver during the dry summer. In order to obtain fast growth of vetiver and to increase the possibility of its using the rainwater, the plants should be planted in the winter, during February and March. However, under this regime, the vetiver plant cannot be used as a soil stabilizer during the first winter, because the plant is still small. In contrast, under irrigation it is advantageous to plant vetiver at the beginning of the summer; the plant then has sufficient time to grow and develop before the beginning of the winter, so that its effect as a soil stabilizer in the following wet winter could be maximal. It was found that vetiver could grow in a wide range of substrates, such as: sandy soil, loamy sand, clay soil, crushed limestone, sandy clay loam, and tuff/peat mixture.  相似文献   
183.
In a context of increasing urban sprawl and water scarcity common to other Mediterranean cities, this article focuses on the urban parks in the Region of Barcelona (Catalonia, Spain) to examine how these parks are distributed in this region and to assess whether their design and management follow criteria adapted to Mediterranean environmental conditions, especially in what concerns water use. In order to evaluate the environmental performance of these parks, we selected four factors possibly influencing the adoption of park management practices at the local scale: urban density, population size of the municipality, municipal income per capita, and political orientation of the city council. After determining the location and area of urban parks in the region, we correlated these four explanatory factors with several management tasks extracted from two different samples of parks (one of 315 parks and another of 125 parks) and a survey of 86 city councils. Results show that, in general, urban parks were more frequent in large, dense, and left/green municipalities but that environmentally sound practices were more common in small and low-density municipalities. We conclude that changes in certain practices (especially the substitution of high water demanding species) could improve significantly the environmental performance of public spaces in large urban areas with Mediterranean climates. Our observations may be pertinent for other cities interested in the provision of environmental public goods such as parks that necessitate water for irrigation.  相似文献   
184.
Eels are exposed to pollutants due to their unusual life cycle and are vulnerable to contamination associated with sediment due to their diet, feeding habits and territoriality. Since the 1980s, a decline in American and European eel populations has been recorded. The causes of this decline still are unknown but pollution from domestic and industrial effluents is known to be involved. Since little data is available on PCB contamination in eels from Italian waters, PCBs were measured in muscle of Anguilla anguilla captured in 2001 in two brackish ecosystems of the Mediterranean: the lagoons of Orbetello and Santa Giusta (Italy). PCBs were higher in samples from Orbetello lagoon than in those detected from Santa Giusta lagoon (P < 0.05). Congener and isomer analyses indicated Aroclor 1260 as a likely source of PCBs in the Orbetello and Santa Giusta samples. Only the toxic equivalents (TEQs) of mono-ortho PCBs were calculated.  相似文献   
185.
Organochlorines (including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs)) were analysed in 10 surface sediment samples collected from the Bahiret el Bibane lagoon, which is one of the most productive lagoons and one of the most important active commercial fish traps in the southern Tunisia. The aim was to obtain information concerning the recent deposition of these compounds in this area, together with the levels, the distribution and any potential biological risk. Total concentrations of OCPs and PCBs in the sediments ranged from below the limit of detection (?1 and from 29.5 to 88.2?ng?g?1?dw, respectively. The spatial distribution of PCBs suggested that the sources of these contaminants are probably located outside the lagoon and are transported by water currents and atmospheric deposition. Compared with some other regions of the world, the Bahiret el Bibane lagoon exhibited low to moderate levels of PCBs and OCPs. According to established sediment quality guidelines, PCBs and Lindane at most of the study sites would be more concerned for the ecotoxicological risk in the Bahiret el Bibane lagoon. The results of this study could provide a useful aid for the sustainable marine management of the region.  相似文献   
186.
Portman ME  Nathan D  Levin N 《Ambio》2012,41(7):670-681
Marine protected areas (MPAs) are critical to the well-being of threatened ecosystems and thus can be highly beneficial to humans, especially to those residing nearby. We explore the qualities of 117 MPAs in the Mediterranean basin and develop a taxonomy of their characteristics. We relate the spatial distribution of the MPAs to the various characteristics of the taxonomy (size, distance from shore, protection levels, management regimes, etc.) and to areas of high human impact and influence levels. To do this we use information on biogeographic regions and information from two different human influence models; one model developed for the marine environment and one covering the littoral terrestrial environment. Our analysis provides insights to planners and managers working in a regional capacity and trying to build MPA networks. Generally, current MPAs have not been established in high impact areas despite their being close to shores containing intense human activity. Decision-makers wishing to design and establish new MPAs may seek out areas of high cumulative human impacts (near the marine-terrestrial interface) or avoid them depending on marine conservation objectives, including the desire to vary types of MPAs within a network. Limitations of our analysis and methodology indicate areas for further research.  相似文献   
187.
The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy.Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water endmember. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d).A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 ± 1.5, 3.8 ± 0.7, 3.0 ± 1.3, and 3.5 ± 1.0 × 1010 L d−1 for 223,224,226, 228Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 × 109 L d−1). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater.  相似文献   
188.
Extensive research has been done on the 'high politics' of negotiations of international environmental agreements. However, little attention has been paid to the effectiveness of their implementation after coming into force. Effectiveness cannot be easily measured, since different stakeholders use different criteria as the basis of their opinion. The purpose of this study is to investigate discourses on the effectiveness of an international environmental regime. The regime chosen is the Mediterranean Action Plan (MAP) - and its legal framework, the Barcelona Convention - which was established in 1975 under the aegis of the United Nations Environment Programme (UNEP). Q methodology was used to reveal discourses on the effectiveness of UNEP/MAP. After collecting relevant literature and identifying the stakeholders, 25 in-depth interviews were conducted. The stakeholders were from the Secretariat of the Convention, academia, NGO workers, and others that studied or knew the subject well. From these interviews 294 statements were extracted, from which 44 were finally selected to be used in the Q study. The interviewees were approached for the second time to complete the Q sorts. This study revealed four distinct discourses concerning the effectiveness of international environmental regimes. It concludes that there is no one 'right' way of defining effectiveness and that no approach can provide more than a partial evaluation of the overall effectiveness of a regime.  相似文献   
189.
High O3 levels, driving uptake and challenging defense, prevail on the Canary Islands, being associated with the hot and dry summers of the Mediterranean-type climate. Pinus canariensis is an endemic conifer species that forms forests across these islands. We investigated the effects of ozone on photosynthesis and biochemical parameters of P. canariensis seedlings exposed to free-air O3 fumigation at Kranzberg Forest, Germany, where ambient O3 levels were similar to those at forest sites in the Canary Islands. The twice-ambient O3 regime (2xO3) neither caused visible injury-like chlorotic or necrotic spots in the needles nor significantly affected violaxanthin, antheraxanthin and zeaxanthin levels and the de-epoxidation state of the xanthophyll cycle. In parallel, stomatal conductance for water vapour, net photosynthesis, intercellular CO2 concentration, chlorophyll fluorescence parameters, as well as antioxidant levels were hardly affected. It is concluded that presently prevailing O3 levels do not impose severe stress on P. canariensis seedlings.  相似文献   
190.
Although ecotoxicological data on heavy metals are abundant, information on other potentially toxic elements with attributed deficiency and/or toxic disturbances is scarce. Here we quantify zinc, copper, iron, manganese, chromium, molybdenum, strontium, barium, and boron in bones of greater white-toothed shrews, Crocidura russula, inhabiting two protected Mediterranean coastal sites: the Ebro Delta, a wetland impacted by human activities, and the Medas Islands, a reference site. Natural and anthropogenic inputs significantly increase Fe, Mn, Mo, Sr, Ba, and B in specimens from the Ebro Delta, whereas Cu and Cr were higher in Medas' shrews. Principal component analysis allowed complete separation between sites along the first two axes in particular due to B, Sr, and Cu. This study provides metal reference values in bones of insectivores, explores their variability and bioaccumulation patterns in depth, and assesses the potential environmental risk and toxicity for biota exposed to the above elements.  相似文献   
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