排序方式： 共有19条查询结果，搜索用时 16 毫秒
1.
2.
Trace Metal Solid State Speciation in Aerosols of the Northern Levantine Basin,East Mediterranean 总被引：3，自引：0，他引：3
Mustafa Koçak Nilgun Kubilay Barak Herut Malcolm Nimmo 《Journal of Atmospheric Chemistry》2007,56(3):239-257
An established three stage sequential leach scheme was applied to a series of selected high volume aerosol samples (n = 35) collected from the Turkish Eastern Mediterranean coastline (Erdemli). Samples were selected according to their air
mass back trajectory history to reflect the contrasting mixtures of aerosol material present in the Eastern Mediterranean
marine aerosol. Two populations were adopted, those samples which were classed as “anthropogenic” and those which were “Saharan”
dominated aerosol populations. Applying the three stage leach it was possible to define the proportion for each of the considered
metals (Al, Fe, Cu, Pb, Cd, Zn and Mn) present in the (a) “exchangeable” (b) “carbonate / oxide” and (c) “refractory” phases,
representing novel solid state aerosol speciation data for this marine system. Clear trends were established, conforming with
data from previous studies with mainly crustal derived metals (Al and Fe) being present in the refractory phases (Al > 88%;
Fe > 84%) and those influenced by anthropogenic sources being dominating in the exchangeable phase, although for these metals
the variability was comparatively high (12–64%; 19–85%; 40–100% for Zn, Pb and Cd, respectively). For the majority, greater
exchangeable fractions were present the lower the crustal source contribution to the aerosol population, whereas the “refractory”
fraction exhibited contrasting behaviour. This was illustrated by the novel application of the mixing diagram, presenting
each of the three speciation stages against the corresponding percent anthropogenic contribution to each collected sample.
Zn, Pb and Cd all illustrated progressive decrease in the percent exchangeable with increasing crustal contribution to the
aerosol population. The percent exchangeable was discussed in terms of its use to represent the upper limit of the bioavailable
fraction of metal associated with the aerosol, post deposition. The mixing diagram approach enabled the prediction of the
residual fractions for Cd, Pb and Zn (41 ± 4%; 62 ± 4% and 82 ± 5%, respectively,) in Saharan end-member material. 相似文献
3.
Orit Hyams-Kaphzan Ahuva Almogi-Labin Chaim Benjamini Barak Herut 《Marine pollution bulletin》2009,58(12):1888-1902
The eastern Mediterranean is naturally highly oligotrophic, but urbanization along the Levant coast has led to raised organic and nutrient loads. This study tracks living foraminiferal assemblages at two sites near an activated sewage sludge outfall from 11/2003 to 5/2004. Oligotrophic site PL29 shows seasonal variations in O2, chlorophyll a, and organic carbon, and has an abundant, diverse benthic foraminiferal assemblage living at various in-sediment depths. At eutrophic site PL3, ∼16 years of sludge injection favor a depleted assemblage primarily of opportunist foraminifera. This site shows less seasonality, is subjected to organic matter overload, O2-stress, and periodic anoxia, foraminifera are less abundant and diverse, and live at shallower depths. The assemblages at both sites represent a common pool of species, with Ammonia tepida highly dominant. Benthic foraminifera were therefore found to be sensitive to trophic trajectories, respond on sub-seasonal time-scales, and track injection and dispersal of organic loads on the shelf. 相似文献
4.
The objective of this study was to examine whether dissolved inorganic phosphate (DIP) is removed from the Eastern Mediterranean Sea by adhering to atmospherically deposited loess particles sinking through the water column. In a series of radiolable experiments, loess from the Negev Desert, treated in various ways, was added to surface (SSW) and deep (DSW) seawater spiked with 32PO4−3. It was shown that when fresh loess reaches the Mediterranean SSW approximately 1.3 μmol P/g are released (11% of the total P concentration). Biological activity and inorganic particles removed similar amounts of the tracer (30–40%) from SSW. It was estimated that about 0.2 μmol P/g of ‘aged loess' (proxy of particles sinking into DSW), were removed from poisoned SSW and DSW, while there was minor adsorption when either nothing or quartz powder was added. The adsorbed DIP accounts for approximately 15% of the released P and is equivalent to about 2% of the remaining P (11.17 μmol P/g loess). Therefore, the process of DIP removal by atmospherically derived particles exists, but due to the higher release of P, the result is a net addition of dissolved atmospheric phosphorus in seawater. It is postulated that in actual SSW where dust concentrations are much lower, biological uptake out-competes inorganic adsorption, although it was demonstrated that the decrease in loess particle concentrations tends to increase their adsorption capacity. As the loess descends into the DSW it continues to remove DIP and thus transports phosphate from the water column to the sediments. A preliminary quantitative estimate suggests that the process of DIP removal by loess particles cannot explain the phosphate ‘deficit' in the Eastern Mediterranean DSW characterized by unusually high DIN/DIP ratios (27) reported by others. 相似文献
5.
6.
Paul D. Boehm Judith E. Barak David L. Fiest Adria A. Elskus 《Marine environmental research》1982,6(3):157-188
The fate of saturated and aromatic hydrocarbons discharged into the coastal Baltic Sea environment from the TSESIS oil spill has been studied in the acute and postacute (one year) phases of the spill. Periodic samples of Mytilus edulis (mussels) from eight littoral zone stations and Macoma balthica from nine soft bottom stations were obtained as well as sediment trap samples and surface sediment samples. Glass capillary gas chromatography and gas chromatographic mass spectrometry were used as the analytical tools to determine saturated and aromatic hydrocarbon composition and concentrations in these samples.Sediment trap samples indicated that sizable quantities of chemically and microbially weathered oil were sedimented, and available for benthic uptake shortly after the spill. After initial uptake of sedimented oil (500 to 1000 μ/g dry weight), Macoma populations appear to have begun slow depuration through the first winter after the spill, but TSESIS oil was again introduced to the benthic stations studied during the following summer. Mytilus populations in the region were severely impacted by the oil. Initial depuration of spilled oil during the first month was rapid and nearly complete at all but the most heavily impacted stations one year after the spill. The post-spill depuration of assimilated hydrocarbons was characterised by a relative retention of alkylated dibenzothiophenes and alkylated phenanthrenes compared to their unsubstituted parent compounds and compared with the entire homologous naphthalene series.These data suggest that petroleum hydrocarbons from the TSESIS spill have become a chronic source of degraded saturated and aromatic hydrocarbons to the soft bottom benthic communities. Petroleum hydrocarbons in the benthic environment from this spill appear to reside in the difficulty sampled and mobile flucculent layer at the sediment/water interface and may affect epifaunal communities for an extended period of time. 相似文献
7.
8.
Sasan Barak Marziye Yousefi Hamidreza Maghsoudlou Sanaz Jahangiri 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(4):1167-1187
In the recent centuries, one of the most important ongoing challenges is energy consumption and its environmental impacts. As far as agriculture is concerned, it has a key role in the world economics and a great amount of energy from different sources is used in this sector. Since researchers have reported a high degree of inefficiency in developing countries, it is necessary for the modern management of cropping systems to have all factors (economics, energy and environment) in the decision-making process simultaneously. Therefore, the aim of this study is to apply Multi-Objective Particle Swarm Optimization (MOPSO) to analyze management system of an agricultural production. As well as MOPSO, two other optimization algorithm were used for comparing the results. Eventually, Taguchi method with metrics analysis was used to tune the algorithms’ parameters and choose the best algorithms. Watermelon production in Kerman province was considered as a case study. On average, the three multi-objective evolutionary algorithms could reduce about 30 % of the average Greenhouse Gas (GHG) emissions in watermelon production although as well as this reduction, output energy and benefit cost ratio were increased about 20 and 30 %, respectively. Also, the metrics comparison analysis determined that MOPSO provided better modeling and optimization results. 相似文献
9.
A key concern in crime analysis is the “hidden crime” problem. Crime events unaccounted for in police records limit the external validity of official statistics and, more importantly, hinder the ability of the police to manage crime and utilize their resources effectively. The problem is exacerbated in proactive initiatives aimed at curbing violence through hotspot policing, where inaccuracies and imprecision, or, worse, no data at all, diminish prevention efforts. Previous studies have sought to overcome the data problem by juxtaposing police records with ambulance data on assault callouts and have found profound disparities. Specifically, researchers matched “crime hotspots” with “ambulance hotspots” (rather than individual events) because patient confidentiality considerations have prevented health professionals from sharing subject-level data with the police. However, health services can safely share spatial data on wider areas that do not disclose personal information. We build on this line of inquiry by analyzing data from the Thames Valley, United Kingdom, and observing spatial hotspots of different sizes. The results demonstrate that while the police and ambulance services attend to the same communities and similar types of facilities, the police are “blinded” to the location of nearly 8 out of 10 assaults. The incongruency is shown even with severe assaults, but to a lesser extent. We then simulate the reduction in injuries if the police had access to health data at different spatial levels and show that even under the most conservative set of assumptions, such an approach can prevent between 113 and 116 violent injuries each year that might otherwise require hospitalization. 相似文献
10.
The thermal pollution patch of Hadera power plant was used as a natural laboratory to evaluate the potential long-term effects of rise in Eastern Mediterranean SST on living benthic foraminifera. Their sensitivity to environmental changes makes foraminifera ideal for this study. Ten monthly sampling campaigns were performed in four stations located along a temperature gradient up to 10 °C from the discharge site of heated seawater to a control station. The SST along this transect varied between 25/18 °C in winter and 36/31 °C in summer. A significant negative correlation was found between SST in all stations and benthic foraminiferal abundance, species richness and diversity. The total foraminiferal abundance and species richness was particularly low at the thermally polluted stations especially during summer when SST exceeded 30 °C, but also throughout the entire year. This indicates that thermal pollution has a detrimental effect on benthic foraminifera, irrelevant to the natural seasonal changes in SST. 相似文献