خيارات البحث
النتائج 801 - 810 من 3,207
Simulation of scenarios of oil droplet formation from the Deepwater Horizon blowout النص الكامل
2015
Zhao, Lin | Boufadel, Michel C. | Adams, Eric | Socolofsky, Scott A. | King, Thomas | Lee, Kenneth | Nedwed, Timothy
Knowledge of the droplet size distribution (DSD) from the Deepwater Horizon (DWH) blowout is an important step in predicting the fate and transport of the released oil. Due to the absence of measurements of the DSD from the DWH incident, we considered herein hypothetical scenarios of releases that explore the realistic parameter space using a thoroughly calibrated DSD model, VDROP-J, and we attempted to provide bounds on the range of droplet sizes from the DWH blowout within 200m of the wellhead. The scenarios include conditions without and with the presence of dispersants, different dispersant treatment efficiencies, live oil and dead oil properties, and varying oil flow rate, gas flow rate, and orifice diameter. The results, especially for dispersant-treated oil, are very different from recent modeling studies in the literature.
اظهر المزيد [+] اقل [-]Neutral red cytotoxicity assays for assessing in vivo carbon nanotube ecotoxicity in mussels — Comparing microscope and microplate methods النص الكامل
2015
Miller, M.A. | Bankier, C. | Al-Shaeri, M.A.M. | Hartl, M.G.J.
The purpose of the present study was to compare two neutral red retention methods, the more established but very labour-intensive microscope method (NRR) against the more recently developed microplate method (NRU). The intention was to explore whether the sample volume throughput could be increased and potential operator bias avoided. Mussels Mytilus sp. were exposed in vivo to 50, 250 and 500μgL−1 single (SWCNTs) or multi-walled carbon nanotubes (MWCNTs). Using the NRR method, SWCNTs and MWCNTs caused concentration dependent decreases in neutral red retention time. However, a concentration dependent decrease in optical density was not observed using the NRU method. We conclude that the NRU method is not sensitive enough to assess carbon nanotube ecotoxicity in vivo in environmentally relevant media, and recommend using the NRR method.
اظهر المزيد [+] اقل [-]Variations in the abundance and structural diversity of microbes forming biofilms in a thermally stressed coral reef system النص الكامل
2015
Mahmoud, Huda
Little information is known about biofilm formation in the thermally stressed coral reef systems north of the Arabian Gulf. The current study investigates the abundance and diversity of marine microbes involved in biofilm formation and their succession over a period of 14weeks (May–August 2007) at temperatures exceeding 32°C. The results showed variations in microbial numbers and the development of more stable biofilm communities as the biofilms aged. The culture-dependent technique and microscopic examination of the developed biofilms showed the dominance of key species known for their role in precipitating CaCO3 such as Vibrio and in facilitating coral larvae settlement and metamorphosis such as Pseudoalteromonas, Bacillariophyceae and Rhodophyceae. The results revealed biofilm formations with microbial diversities that have the potential to support the larval settlement and metamorphism of marine organisms and to consolidate and stabilize biofilms via the process of calcification in the thermally stressed coral reef system considered herein.
اظهر المزيد [+] اقل [-]137Cs, 40K and 210Po in marine mammals from the southern Baltic Sea النص الكامل
2015
Ciesielski, Tomasz | Góral, Marta | Szefer, Piotr | Jenssen, Bjørn Munro | Bojanowski, Ryszard
This study provides information on baseline concentrations of the radionuclides Cesium-137, Potassium-40 and Polonium-210 in sea mammals from the Baltic Sea. The radionuclides were analyzed in the liver, kidney and muscle of harbor porpoises, striped dolphins, and gray and ringed seals from the Polish coast by γ- and α-spectrometry. Median 137Cs activities were 14.8, 13.2 and 23.2Bqkg−1 w.w. in the liver, kidney and muscles, respectively. Activities of 40K and 210Po in the respective tissues were found to be 79.1, 79.8 and 111Bqkg−1 for 40K and 58.1, 59.2 and 32.9Bqkg−1 for 210Po. The measured 137Cs concentrations were extraordinarily high in comparison to those reported in sea mammals from other locations. However, dose assessments did not imply health effects from 137Cs exposure in Baltic Sea mammals. Correlations between 137Cs tissue activities and reported sea water concentrations highlight the potential use of marine mammals for biomonitoring purposes.
اظهر المزيد [+] اقل [-]Black coral as a new environmental recorder: The lead profiles in coral skeletons over the past century النص الكامل
2015
Lu, Shan | Cai, Weiying | Zhang, Xiaodi | Li, Xiubao | Huang, Hui | Zhang, Fenfen | Zhang, Jing
Lead (Pb) is a typical heavy metal pollutant in the environment, and most Pb contamination comes from human activities. In the present work, the Pb contents of two black coral specimens (Cirrhipathes spp.) collected from the northern South China Sea were measured by synchrotron radiation micro X-ray fluorescence (SR μ-XRF) analysis with 2.5μm resolution. The results showed that sample SY-1 from the Sanya Bay (near the continent) exhibited higher Pb levels and greater fluctuations than sample XS-1 from the Xisha Islands (off the continent), reflecting the influence of terrestrial input and atmospheric deposition in coastal surface seawater. The present work also demonstrated that the Pb profile in black coral nearshore was highly influenced by human activities, mainly by war and economic development. Thus, black coral may serve as a new potential environmental Pb recorder with SR μ-XRF analytical technology.
اظهر المزيد [+] اقل [-]A spatial assessment of baseline nutrient and water quality values in the Ashepoo–Combahee–Edisto (ACE) Basin, South Carolina, USA النص الكامل
2015
Keppler, C.J. | Bergquist, D.C. | Brock, L.M. | Felber, J. | Greenfield, D.I.
The Ashepoo–Combahee–Edisto (ACE) Basin (South Carolina, USA) National Estuarine Research Reserve System (NERRS) encompasses some of the least developed USA coastline. Yet, periodic sampling showed that certain regions have higher nutrient, fecal coliform, and chlorophyll a levels, often with lower dissolved oxygen, than other South Carolina estuaries. To evaluate the spatial extent of these issues, a summer (2008) baseline study was conducted. Physical water quality, total nitrogen and phosphorus, chlorophyll a, dissolved organic carbon, and suspended solids were measured from surface waters of 67 stations (30 tidal creek, 37 open water). Nutrient and chlorophyll a levels were significantly (p<0.01) and negatively correlated with the extent of open water (% land cover), and chlorophyll a and nitrogen levels were, at times, elevated relative to concentrations typical of other estuaries in the state, reinforcing previous findings. This survey also identified several creeks not previously monitored that exhibited elevated nutrients.
اظهر المزيد [+] اقل [-]Distributions, sources and ecological risk assessment of arsenic and mercury in the surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea النص الكامل
2015
Zhuang, Wen | Gao, Xuelu
The spatial distributions of As and Hg in riverine and marine surface sediments of the coastal southwestern Laizhou Bay were obtained, and multiple indices and guidelines were applied to assess their contamination and ecological risks. The As concentrations in riverine sediments were close to those in marine sediments, and on the whole the dominant proportion of As was identified to be from natural sources. The Hg concentrations in riverine sediments were much higher than those in marine sediments, so river transportation was likely the main way of Hg into the southwestern Laizhou Bay. In respect of As, the sediment quality was fine according to the risk assessment methods used; in contrast, Hg presented an extremely contaminated status with a very high ecological risk in some riverine sediments, while most of the marine sediments were relatively much less polluted by Hg and under a lower ecological risk from it.
اظهر المزيد [+] اقل [-]JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys: We can do better النص الكامل
2015
Wright, Andrew J. | Cosentino, A Mel
The U.K.’s Joint Nature Conservation Committee 1998 guidelines for minimising acoustic impacts from seismic surveys on marine mammals were the first of their kind. Covering both planning and operations, they included various measures for reducing the potential for damaging hearing – an appropriate focus at the time. Since introduction, the guidelines have been criticised for, among other things: the arbitrarily-sized safety zones; the lack of shut-down provisions; the use of mitigation measures that introduce more noise into the environment (e.g., soft-starts); inadequate observer training; and the lack of standardised data collection protocols. Despite the concerns, the guidelines have remained largely unchanged. Moreover, increasing scientific recognition of the scope and magnitude of non-injurious impacts of sound on marine life has become much more widespread since the last revisions in 2010. Accordingly, here we present feasible and realistic recommendations for such improvements, in light of the current state of knowledge.
اظهر المزيد [+] اقل [-]Mass culture strategy for bacterial yeast co-culture for degradation of petroleum hydrocarbons in marine environment النص الكامل
2015
Priya, Anchal | Mandal, Ajoy K. | Ball, A. S. | Manefield, Mike | Lal, Banwari | Sarma, Priyangshu M.
In the present study a metabolically versatile co-culture with two Bacilli and one yeast strain was developed using enrichment culture techniques. The developed co-culture had affinity to degrade both aliphatic and aromatic fractions of petroleum crude oil. Degradation kinetics was established for designing the fermentation protocol of the co-culture. The developed mass culture strategy led to achieve the reduction in surface tension (26dynescm−1 from 69 dynescm−1) and degradation of 67% in bench scale experiments. The total crude oil degradation of 96% was achieved in 4000l of natural seawater after 28days without adding any nutrients. The survival of the augmented co-culture was maintained (109cellsml−1) in contaminated marine environment. The mass culture protocol devised for the bioaugmentation was a key breakthrough that was subsequently used for pilot scale studies with 100l and 4000l of natural seawater for potential application in marine oil spills.
اظهر المزيد [+] اقل [-]Endangered New Caledonian endemic mushroom coral Cantharellus noumeae in turbid, metal-rich, natural and artificial environments النص الكامل
2015
Gilbert, Antoine | Heintz, Tom | Hoeksema, Bert W. | Benzoni, Francesca | Fernandez, Jean-Michel | Fauvelot, Cécile | Andréfouët, Serge
Since its description in 1984, little attention has been paid to the New Caledonian endemic mushroom coral Cantharellus noumeae (Fungiidae), an IUCN Red-listed, endangered coral species. Our study presents the first ever quantitative assessment conducted on C. noumeae populations for two contrasting sites in the same turbid bay. Sites differed by their substrates of artificial or natural origins. Metal concentrations of superficial sediment were measured. C. noumeae was found in high densities in metal-rich and turbid environments at both locations, reaching up to 288 individuals per 50m2. It was 3.5 times more abundant on natural rock than on artificial substrates. Recruitment was also higher proportionally on rock (47% vs 7–14%). The composition of the associated coral communities included 30–37 species occurring in low densities. Our findings clarify the environmental niche of this species and its colonization potential, in order to eventually better characterize its conservation status.
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