خيارات البحث
النتائج 1851 - 1860 من 5,151
Underwater noise levels of pile-driving in a New Zealand harbour, and the potential impacts on endangered Hector's dolphins النص الكامل
2018
Leunissen, Eva M. | Dawson, Stephen M.
Impact pile-driving generates loud underwater anthropogenic sounds, and is routinely conducted in harbours around the world. Surprisingly few studies of these sounds and their propagation are published in the primary literature. To partially redress this we studied pile-driving sounds in Lyttelton Harbour, New Zealand, during wharf reconstruction after earthquake damage. That Lyttelton harbour is routinely used by Hector's dolphins (Cephalorhynchus hectori), an endangered species found only in New Zealand, provided further context for this study. Steel piles of 0.61 or 0.71 m diameter were driven using three different pile-drivers. Maximum calculated source SEL was 192 dB re 1 μPa2s @ 1 m (SPL0−p of 213 dB re 1 μPa @ 1 m). Propagation of piling noise was strongly influenced by harbour bathymetry and a rock breakwater near the piling operation. We calculated range estimates at which Hector's dolphins may suffer temporary hearing threshold shift and behavioural change.
اظهر المزيد [+] اقل [-]Composition and abundance of benthic marine litter in a coastal area of the central Mediterranean Sea النص الكامل
2018
Consoli, Pierpaolo | Falautano, Manuela | Sinopoli, Mauro | Perzia, Patrizia | Canese, Simonepietro | Esposito, Valentina | Battaglia, Pietro | Romeo, Teresa | Andaloro, Franco | Galgani, François | Castriota, Luca
Abundance and qualitative composition of benthic marine litter were investigated in a coastal area of the central Mediterranean Sea. Almost 30 km of video footage, collected by a Remotely Operated Vehicle between 5 and 30 m depth, were analyzed. Litter density ranged from 0 to 0.64 items/m2 with a mean of 0.11 (±0.16) items/m2. General wastes, made up almost entirely of plastic objects, were the dominant sources of debris representing 68% of the overall litter. The remaining 32% consisted of lost or abandoned fishing gears. Synthetic polymers, considering both fishing gears and general waste, represented 73% of total debris items. Our results are comparable with litter amounts reported in other Mediterranean sites at similar depths. Overall, the results are discussed in terms of monitoring strategy, to support the implementation of the Marine Strategy Framework Directive (2008/56/EC) for descriptor 10 and the Mediterranean UN Environment (UNEP/MAP) regional Plan on Marine Litter.
اظهر المزيد [+] اقل [-]Sources and fate of organic matter in constructed versus natural coastal waterways النص الكامل
2018
Pitt, Kylie A. | Lee, Shin Yip | Connolly, Rod M. | Bui, Thi Hong Hanh | Doriean, Nic
Coastal wetlands are increasingly being converted into canal estates with potential consequences for ecosystem functioning. We compared the sources and fate of organic matter and water quality at four types of canal habitats (entrances and ends of canals, canal lakes and lake edges) and shallow and deep natural habitats (four replicates of each habitat). The fate of labile organic matter was assessed by measuring rates of scavenging of carrion. Surface sediments were analysed for organic carbon content and stable carbon isotopes, fatty acid biomarkers and compound specific stable isotope analysis of selected fatty acids were used to elucidate sources of sedimentary organic matter. Canal lakes differed from other habitats and were characterised by negligible scavenging, larger quantities of organic matter comprised of higher contributions from diatoms, and hypoxia. Despite some trends, natural habitats were statistically indistinguishable from canal entrances and ends. Variation among replicate habitats was large.
اظهر المزيد [+] اقل [-]Spreading of waxy oils on calm water النص الكامل
2018
Brönner, Ute | Johansen, Øistein | Leirvik, Frode | Nordam, Tor | Sørheim, Kristin R.
Spreading of waxy oils on calm water النص الكامل
2018
Brönner, Ute | Johansen, Øistein | Leirvik, Frode | Nordam, Tor | Sørheim, Kristin R.
The objective of this paper is to provide a simple extension of the much-used gravity spreading model for oil on calm water to account for the spreading behavior of waxy crude oils in cold waters – including the observed retardation and eventual termination of spreading at certain oil film thicknesses. This peculiar behavior is not predicted by traditional spreading models for oil on calm water (i.e. viscous-gravity spreading models), but may occur due to non-Newtonian oil properties caused by precipitation of wax at low temperatures. To clarify the spreading behavior of such oils, SINTEF has conducted a series of laboratory experiments with a range of waxy oil mixtures. The present paper contains analyses of data from these experiments, including favorable comparisons with calculations by a proposed improved surface spreading model.
اظهر المزيد [+] اقل [-]Spreading of waxy Crude Oils on calm weather | Spreading of waxy Crude Oils on calm weather النص الكامل
2018
Brönner, Ute | Johansen, Øistein | Leirvik, Frode | Nordam, Tor | Sørheim, Kristin Rist
The objective of this paper is to provide a simple extension of the much-used gravity spreading model for oil on calm water to account for the spreading behavior of waxy crude oils in cold waters – including the observed retardation and eventual termination of spreading at certain oil film thicknesses. This peculiar behavior is not predicted by traditional spreading models for oil on calm water (i.e. viscous-gravity spreading models), but may occur due to non-Newtonian oil properties caused by precipitation of wax at low temperatures. To clarify the spreading behavior of such oils, SINTEF has conducted a series of laboratory experiments with a range of waxy oil mixtures. The present paper contains analyses of data from these experiments, including favorable comparisons with calculations by a proposed improved surface spreading model. | Spreading of waxy Crude Oils on calm weather | acceptedVersion
اظهر المزيد [+] اقل [-]Experimental leaching of massive sulphide from TAG active hydrothermal mound and implications for seafloor mining النص الكامل
2018
Fallon, Emily K. | Niehorster, Ella | Brooker, Richard A. | Scott, Thomas B.
Seafloor massive sulphide samples from the Trans-Atlantic Geotraverse active mound on the Mid-Atlantic Ridge were characterised and subjected to leaching experiments to emulate proposed mining processes. Over time, leached Fe is removed from solution by the precipitation of Fe oxy-hydroxides, whereas Cu and Pb leached remained in solution at ppb levels. Results suggest that bulk chemistry is not the main control on leachate concentrations; instead mineralogy and/or galvanic couples between minerals are the driving forces behind the type and concentration of metals that remain in solution. Dissolved concentrations exceed ANZECC toxicity guidelines by 620 times, implying the formation of localised toxicity in a stagnant water column. Moreover, concentrations will be higher when scaled to higher rock-fluid ratios and finer grain sizes proposed for mining scenarios. The distance at which dilution is achieved to meet guidelines is unlikely to be sufficient, indicating a need for the refinement of the mining process.
اظهر المزيد [+] اقل [-]Microbial communities of polluted sub-surface marine sediments النص الكامل
2018
Catania, Valentina | Cappello, Simone | Di Giorgi, Vincenzo | Santisi, Santina | Di Maria, Roberta | Mazzola, Antonio | Vizzini, Salvatrice | Quatrini, Paola
Microbial communities of coastal marine sediment play a key role in degradation of petroleum contaminants. Here the bacterial and archaeal communities of sub-surface sediments (5–10 cm) of the chronically polluted Priolo Bay (eastern coast of Sicily, Italy), contaminated mainly by n-alkanes and biodegraded/weathered oils, were characterized by cultural and molecular approaches. 16S-PCR-DGGE analysis at six stations, revealed that bacterial communities are highly divergent and display lower phylogenetic diversity than the surface sediment; sub-surface communities respond to oil supplementation in microcosms with a significant reduction in biodiversity and a shift in composition; they retain high biodegradation capacities and host hydrocarbon (HC) degraders that were isolated and identified. HC-degrading Alfa, Gamma and Epsilon proteobacteria together with Clostridia and Archaea are a common feature of sub-surface communities. These assemblages show similarities with that of subsurface petroleum reservoirs also characterized by the presence of biodegraded and weathered oils where anaerobic or microaerophilic syntrophic HC metabolism has been proposed.
اظهر المزيد [+] اقل [-]Liver histopathology and biochemical biomarkers in Gobius niger and Zosterisessor ophiocephalus from polluted and non-polluted Tunisian lagoons (Southern Mediterranean Sea) النص الكامل
2018
Louiz, Ibtissem | Palluel, Olivier | Ben-Attia, Mossadok | Aït-Aïssa, Sélim | Hassine, Oum Kalthoum Ben
The aim of this study was to appraise the response of a multi-marker approach in fish species, Gobius niger and Zosterisessor ophiocephalus, in a polluted lagoon (Bizerte lagoon: MB and ML sites) and in a reference site (Ghar-El-Melh lagoon entrance) by the analysis of physiological indexes, liver histopathology and some biochemical biomarkers. The results showed liver hypertrophy in fish collected from Bizerte lagoon as well as many non-specific lesions, unlike the reference site. All Bizerte lagoon sites had the same prevalence of histopathological lesions, but the mean intensity (MI) of parasites seemed to be more sensible as an indicator of pollution levels. Indeed, parasite MI was more important in MB site that has a higher pollution level. Also, biochemical biomarkers showed an induction in Bizerte lagoon sites with some differences within sites and species. The impact of the continuous release of pollution on the biomarker's response is discussed.
اظهر المزيد [+] اقل [-]Heavy metal levels of ballast waters in commercial ships entering Bushehr port along the Persian Gulf النص الكامل
2018
Dobaradaran, Sina | Soleimani, Farshid | Nabipour, Iraj | Saeedi, Reza | Mohammadi, Mohammad Javad
In this study we report the concentration levels of heavy metals (including Pb, Cd, Hg, Cr, Ni, Fe, Mn, Cu) in ballast water of commercial ships, entering Bushehr port for the first time in the region of the Persian Gulf. The concentration levels of Cu and Fe in all samples of the ballast water were higher compared with the coastal waters of Bushehr port. In the case of Cd, 76.47% of samples had higher concentration level compared with the coastal waters of Bushehr port. Results showed that in a long term the ballast water has the potential to change the chemical quality in marine environments and also may affect the human health and marine ecosystem where ships discharge their ballast water. Therefore, permanent monitoring as well as treatment of ballast water before discharging is crucial to keep the marine environment health.
اظهر المزيد [+] اقل [-]Degradation of Deepwater Horizon oil buried in a Florida beach influenced by tidal pumping النص الكامل
2018
Huettel, Markus | Overholt, Will A. | Kostka, Joel E. | Hagan, Christopher | Kaba, John | Wells, Wm Brian | Dudley, Stacia
After Deepwater Horizon oil reached the Florida coast, oil was buried in Pensacola Beach (PB) sands to ~70cm depth, resulting in Total Petroleum Hydrocarbon (TPH) concentrations up to ~2kg per meter of beach. This study followed the decomposition of the buried oil and the factors influencing its degradation. The abundance of bacteria in oiled sand increased by 2 orders of magnitude within one week after oil burial, while diversity decreased by ~50%. Half-lives of aliphatic and aromatic hydrocarbons reached 25 and 22days, respectively. Aerobic microbial oil decomposition, promoted by tidal pumping, and human cleaning activities effectively removed oil from the beach. After one year, concentrations of GC-amenable hydrocarbons at PB were similar to those in the uncontaminated reference beach at St. George Island/FL, and microbial populations that disappeared after the oil contamination had reestablished. Yet, oxihydrocarbons can be found at PB to the present day.
اظهر المزيد [+] اقل [-]Development of a storm surge driven water quality model to simulate spills during hurricanes النص الكامل
2018
Kiaghadi, Amin | Rifai, H. S. | Burleson, Daniel W.
Hurricanes can cause widespread environmental pollution that has yet to be fully articulated. This study develops a predictive water quality model to forecast potential contamination resulting from buckled or ruptured storage tanks in coastal industrialized areas when subjected to storm surge. The developed EFDC-Storm Surge model (EFDC-SS) couples EPA's EFDC code with the SWAN-ADCIRC hurricane simulation model. EFDC-SS is demonstrated using the Houston Ship Channel in Texas as a testbed and hurricane Ike as a model hurricane. Conservative and decaying dye runs evaluated various hurricane scenarios, combined with spills released at different locations and release times. Results showed that tank locations with shorter distances to the main waterbody and lower ground elevations have a higher risk of inundation and rapid spill mass transport. It was also determined that hurricane strength and landfall location, the location of the spill, and the spill release time relative to peak surge were interdependent.
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