خيارات البحث
النتائج 861 - 870 من 3,243
Environmental assessment of coastal surface sediments at Tarut Island, Arabian Gulf (Saudi Arabia)
2015
Youssef, Mohamed | El-Sorogy, Abdelbaset | Al Kahtany, Khaled | Al Otiaby, Naif
Thirty eight surface sediments samples have been collected in the area around Tarut Island, Saudi Arabian Gulf to determine the spatial distribution of metals, and to assess the magnitude of pollution. Total concentrations of Fe, Mn, As, B, Cd, Co, Cr, Cu, Hg, Mo, Pb, Se, and Zn in the sediments were measured using ICP-MS (Inductively Coupled Plasma-Mass Spectrometer). Nature of sediments and heavy metals distribution reflect marked changes in lithology, biological activities in Tarut bay. Very high arsenic concentrations were reported in all studied locations from Tarut Island. The concentrations of Mercury are generally high comparing to the reported values from the Gulf of Oman, Red Sea. The concentrations of As and Hg exceeded the wet threshold safety values (MEC, PEC) indicating possible As and Hg contamination. Dredging and land filling, sewage, and oil pollution are the most important sources of pollution in the study area.
اظهر المزيد [+] اقل [-]GC–MS analysis of two types of mixed oils, a comparison of composition and weathering patterns
2015
Ho, S.J. | Wang, C.Y. | Luo, Y.M.
In order to compare the effects of weathering on two types of mixed oil, simulated weathering experiments were performed. The first sample was a mixture of two fresh oils and the second sample was a mixture of one fresh oil and another oil sample that had undergone a serious weathering process. Comparative studies evaluated decay rates and changes in diagnostic ratios of some fingerprinting biomarkers. Results showed that the mixing process affected the weathering rate of some compounds in the oils and also that certain diagnostic ratios are more suitable for estimating mixing proportions. A Pr/n-C17 versus Ph/n-C18 plot can be used to identify the end-numbers of mixed oils and the (C13+C14)/(C25+C26) ratio is a useful diagnostic ratio to detect the degree of weathering. Finally, hopane, sterane, and alkylated PAH fingerprints were found to give useful insights about the sources of the mixed oils.
اظهر المزيد [+] اقل [-]Are red mullet efficient as bio-indicators of mercury contamination? A case study from the French Mediterranean
2015
Cresson, P. | Bouchoucha, M. | Miralles, F. | Elleboode, R. | Mahé, K. | Marusczak, N. | Thebault, H. | Cossa, D.
Mercury (Hg) is one of the main chemicals currently altering Mediterranean ecosystems. Red mullet (Mullus barbatus and M. surmuletus) have been widely used as quantitative bio-indicators of chemical contamination. In this study, we reassess the ability of these species to be used as efficient bio-indicators of Hg contamination by monitoring during 18months Hg concentrations in muscle tissue of mullet sampled from 5 French Mediterranean coastal areas. Mean concentrations ranged between 0.23 and 0.78μgg−1 dry mass for both species. Values were consistent with expected contamination patterns of all sites except Corsica. Results confirmed that red mullets are efficient bio-indicators of Hg contamination. Nevertheless, the observed variability in Hg concentrations calls for caution regarding the period and the sample size. Attention should be paid to environmental and biologic specificities of each studied site, as they can alter the bioaccumulation of Hg, and lead to inferences about environmental Hg concentrations.
اظهر المزيد [+] اقل [-]Recovery from TBT pollution in English Channel environments: A problem solved?
2015
Langston, W.J. | Pope, N.D. | Davey, M. | Langston, K.M. | O’ Hara, S.C.M. | Gibbs, P.E. | Pascoe, P.L.
Following recognition of effects in the 1980s, tributyltin (TBT) has been monitored at sites in the English Channel to evaluate the prognosis for biota – spanning the introduction of restrictions on TBT use on small boats and the recent phase-out on the global fleet. We describe how persistence and impact of TBT in clams Scrobicularia plana has changed during this period in Southampton Water and Poole Harbour. TBT contamination (and loss) in water, sediment and clams reflects the abundance and type of vessel activity: half-times in sediment (up to 8y in Poole, 33y in Southampton) are longest near commercial shipping. Recovery of clam populations – slowest in TBT-contaminated deposits – provides a useful biological measure of legislative efficacy in estuaries. On rocky shores, recovery from imposex in Nucella lapillus is evident at many sites but, near ports, is prolonged by shipping impacts, including sediment legacy, for example, in the Fal.
اظهر المزيد [+] اقل [-]Entrenching environmental obligation in marine regulation
2015
Wakefield, Jill
The institutional frameworks addressing issues in connection with the marine commons agreed by States are set out in the 1982 UN Convention on the Law of the Sea, which is the basis of the European Union’s common fisheries policy. Despite a substantial body of environmental legislation, provisions concerning the protection of ecosystems and bioversity have not been incorporated into any international measure or EU to control fishing, leading to ecosystem degradation. Regulation should impose the responsibility for rectifying damage to fish stocks and ecosystems as a result of fishing activity on the fishing industry.
اظهر المزيد [+] اقل [-]Enrichment and isolation of crude oil degrading bacteria from some mussels collected from the Persian Gulf
2015
Bayat, Zeynab | Hassanshahian, Mehdi | Hesni, Majid Askari
To date, little is known about existing relationships between mussels and bacteria in hydrocarbon-contaminated marine environments. The aim of this study is to find crude oil degrading bacteria in some mussels at the Persian Gulf. Twenty eight crude oil degrading bacteria were isolated from three mussels species collected from oil contaminated area at Persian Gulf. According to high growth and degradation of crude oil four strains were selected between 28 isolated strains for more study. Determination the nucleotide sequence of the gene encoding for 16S rRNA show that these isolated strains belong to: Shewanella algae isolate BHA1, Micrococcus luteus isolate BHA7, Pseudoalteromonas sp. isolate BHA8 and Shewanella haliotis isolate BHA35. The residual crude oil in culture medium was analysis by Gas Chromatography (GC). The results confirmed that these strains can degrade: 47.24%, 66.08%, 27.13% and 69.17% of crude oil respectively. These strains had high emulsification activity and biosurfactant production. Also, the effects of some factors on crude oil degradation by isolated strains were studied. The results show that the optimum concentration of crude oil was 2.5% and the best degradation take place at 12% of salinity. This research is the first reports on characterization of crude oil degrading bacteria from mussels at Persian Gulf and by using of these bacteria in the field the effect of oil pollution can be reduce on this marine environment.
اظهر المزيد [+] اقل [-]A heavy haze episode in Beijing in February of 2014: Characteristics, origins and implications
2015
Yan, Renchang | Yu, Shaocai | Zhang, Qingyu | Li, Pengfei | Wang, Si | Chen, Bixin | Liu, Weiping
More than half Chinese cities are suffering from severe air pollution due to the rapid development of industry and urbanization. Beijing, as a political and cultural center of China, has frequently suffered from severe haze. However, the precise sources of air pollution in Beijing still remain uncertain. In this study, the observational data (PM2.5, PM10, O3, NO2, CO and SO2) at ten monitoring stations from February 8 to 28, 2014, in Beijing were used to analyze air pollution. The satellite observations for aerosol optical thickness were also used. Backward trajectory model and receptor models were used to identify the sources of air pollution in Beijing. On the basis of PM2.5 concentrations, we separated the whole data into three categories: relatively clean air (PM2.5 concentrations less than 75 μg m–3), haze (PM2.5 concentrations greater than 75 μg m3 but less than 200 μg m3) and heavy haze (PM2.5 concentrations greater than 200 μg m3). The results show that the average concentrations of PM2.5 are 29.5 μg m3, 136.6 μg m3 and 311.2 μg m3 for relatively clean air, haze and heavy haze cases, respectively. The back trajectory cluster analysis reveals that the predominant clusters are east and south for the heavy haze case. The results of the receptor models show that for the haze case, pollutants mainly originated from south of Beijing such as Dezhou, Liaocheng and Heze in Shandong province, while for the heavy haze case, pollutants were mainly from southwest of Beijing such as Baoding, Hengshui and Handan in Hebei province. These results indicate that the emissions in the surrounding provinces made a significant contribution to Beijing's air pollution. Thus, it is necessary to implement air pollution control for all surrounding areas, especially for the industrial zones in the south/southwest regions of Beijing.
اظهر المزيد [+] اقل [-]Parametric study to determine the effect of temperature on oil solidifier performance and the development of a new empirical correlation for predicting effectiveness
2015
Sundaravadivelu, Devi | Suidan, Makram T. | Venosa, Albert D.
Temperature can play a significant role in the efficacy of solidifiers in removing oil slicks on water. We studied and quantified the effect of temperature on the performance of several solidifiers using 5 different types of oils under a newly developed testing protocol by conducting experiments in constant temperature rooms set at 22°C and 5°C. The results indicated that solidifier efficiency decreased substantially at the lower temperature, especially at lower application rates. The removal efficiency of the solidifier was in general directly proportional to temperature, except for the heavier oils, where removal by attachment was observed. Solidifier products with lower powder bulk density exhibited the best removal effectiveness. Analysis of experimental data yielded empirical correlations involving certain operational variables such as application rate, temperature, solidifier property (bulk density), and oil property (viscosity). Regression analysis was used to fit a mathematical model to the experimental solidifier effectiveness data.
اظهر المزيد [+] اقل [-]Geographic structure evidenced in the toxic dinoflagellate Alexandrium pacificum Litaker (A. catenella – group IV (Whedon & Kofoid) Balech) along Japanese and Chinese coastal waters
2015
Genovesi, Benjamin | Berrebi, Patrick | Nagai, Satoshi | Reynaud, Nathalie | Wang, Jinhui | Masseret, Estelle
The intra-specific diversity and genetic structure within the Alexandrium pacificum Litaker (A. catenella – Group IV) populations along the Temperate Asian coasts, were studied among individuals isolated from Japan to China. The UPGMA dendrogram and FCA revealed the existence of 3 clusters. Assignment analysis suggested the occurrence of gene flows between the Japanese Pacific coast (cluster-1) and the Chinese Zhejiang coast (cluster-2). Human transportations are suspected to explain the lack of genetic difference between several pairs of distant Japanese samples, hardly explained by a natural dispersal mechanism. The genetic isolation of the population established in the Sea of Japan (cluster-3) suggested the existence of a strong ecological and geographical barrier. Along the Pacific coasts, the South–North current allows limited exchanges between Chinese and Japanese populations. The relationships between Temperate Asian and Mediterranean individuals suggested different scenario of large-scale dispersal mechanisms.
اظهر المزيد [+] اقل [-]Historical trends (1998–2012) of nickel (Ni), copper (Cu) and chromium (Cr) concentrations in marine sediments at four locations in the Northern Adriatic Sea
2015
Traven, Luka | Furlan, Nikolina | Cenov, Arijana
Historical trends (1998–2012) nickel (Ni), copper (Cu) and chromium (Cr) concentrations in marine sediments were assessed at four locations in the Northern Adriatic Sea (Croatia) in the proximity of an oil refinery. Ecological risks were characterized by benchmarking the dataset against Sediment Quality Guidelines (SQG). A significant number of samples had Ni values above ERL with no exceedance of the ERL values for Cu and Cr. Weak positive historical trends were found for only for Cu. At all sites there were statistically significant correlations between Ni and Cr indicating a common origin of these heavy metals in the investigated marine sediments. There were statistically significant differences between the sites under the direct influence of the oil refinery compared to the control site indicating the possibility that the oil refinery is contributing to the concentration of these heavy metals in the marine sediments.
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