خيارات البحث
النتائج 1041 - 1050 من 4,307
Perfluorocarbon emissions from electrolytic reduction of rare earth metals in fluoride/oxide system النص الكامل
2017
Lizhi, Zhang | Xiufeng, Wang | Bin, Gong
Perfluorocarbons (PFC) are important greenhouse gas. In the aluminum electrolysis industry, PFC emission had been valued. The electrolytic reduction of rare earth metals in fluoride/oxide system with carbon anode and tungsten cathode also has PFC emission. But the PFC emission in rare earth metals industry received less attention. The PFC emissions during the electrolysis were studied by tracking the change of CF4 concentration in the flue gas of neodymium electrolysis and dysprosium-iron alloy electrolysis. The results showed that there were continuous CF4 overflows in the electrolysis process. The CF4 was outburst when anode effect occurred. The anode effect was always accompanied with the low electrolysis temperature. In addition, because of the electrolytic dysprosium-iron alloy requires higher cell voltage, the PFC emissions are higher than rare earth electrolysis. In general, PFC emissions from rare earth metal electrolysis are quite same as the aluminum electrolysis industry.
اظهر المزيد [+] اقل [-]Resource recovery of Eichhornia crassipes as oil superabsorbent النص الكامل
2017
The elastic cellulose-based aerogels (CBAs) with highly porous (99.56%) and low-density (0.0065gcm−1) were prepared using Eichhornia crassipes as cellulose source and polyvinyl alcohol directly as cross-linker via a facile and environment-friendly process. The prepared CBAs exhibited excellent oil/solvent sorption capacities (60.33–152.21gg−1), super-hydrophobicity (water contact angle of 156.7°) as well as remarkable reusability. More importantly, the absorbed oil could be quickly recovered by simple squeezing without significantly structure damage (at least 16 times). All these merits make CBAs very promising materials for oil spillage cleaning.
اظهر المزيد [+] اقل [-]Particulate waste outflow from fish-farming cages. How much is uneaten feed? النص الكامل
2017
Particulate waste outflow from fish-farming cages. How much is uneaten feed? النص الكامل
2017
Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability.
اظهر المزيد [+] اقل [-]Particulate waste outflow from fish-farming cages. How much is uneaten feed? النص الكامل
2017
Ballester-Moltó, Mateo | Sanchez-Jerez, Pablo | Cerezo-Valverde, Jesús | Aguado Giménez, Felipe | Universidad de Alicante. Departamento de Ciencias del Mar y Biología Aplicada | Biología Marina
Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability. | Part of this research was funded by the Spanish Institute of Agro-Forestry Research (INIA; Ministry of Economy and Competitiveness; project RTA2011-00088-00-00). Another part was supported by the Autonomic Government (Department of Water, Agriculture and Environment) (FEDER 1420-10) of Murcia, Spain (Regional Programme co funded by FEDER, project grant number 1420.10). The study was also partially sponsored by the student grant Sub-Programme of Researcher Formation of the Spanish Institute of Agro-Forestry Research (FPI-INIA).
اظهر المزيد [+] اقل [-]Impingement of marine organisms in a tropical atomic power plant cooling water system النص الكامل
2017
A one-year impingement monitoring was conducted at Madras Atomic Power Station (MAPS), Kalpakkam, southeastern coast of India and identified a total of 67 species of marine organisms in the cooling water system. Estimates of total annual impingement contributed about 1.47×106 individuals and 142.5t of biomass. Jellyfish contributed about 6.8×105 individuals and 135.6t of biomass. Crabs, shrimps and fish were the most vulnerable organisms contributing about 4.29×105 individuals, 1.39×105 individuals and 2.16×105 individuals respectively. Commercially important species namely Trichiurus lepturus, Sardinella longiceps and Portunus pelagicus were found to be impinged 1.88% and 0.29% by number and weight of the total biomass respectively. Out of ~327 fish species recorded at Kalpakkam, only about 9.4% of species were impinged at MAPS. Multispecies impingement at MAPS poses the problem of finding the best mitigation options for tropical conditions.
اظهر المزيد [+] اقل [-]Managing the risk of non-indigenous marine species transfer in Singapore using a study of vessel movement النص الكامل
2017
Lim, Chin Sing | Leong, Yi Lin | Tan, Koh Siang
Shipping is recognized as a major vector for the global transfer of non-indigenous marine species (NIMS). As a major transshipment port, Singapore can minimize the risk of NIMS transfer by implementing pragmatic management strategies, such as using vessel movement information to assess the risk of NIMS transfer.Findings from vessel movement information in a major port terminal in Singapore showed that vessel residence time is short, with >92% of vessels spending seven days or less. There was little variation in vessel residence time to vessel arrival numbers, while the top three last ports of call were found to be from regional ports. Using two key features obtained from vessel movement records, 1) vessel residence time and 2) biogeographic origin of the vessels' last port of call, a simple risk assessment matrix was constructed and applied to assess the level of risk of NIMS transfer by transiting vessels.
اظهر المزيد [+] اقل [-]Susceptibility of seagrass to oil spills: A case study with eelgrass, Zostera marina in San Francisco Bay, USA النص الكامل
2017
Fonseca, Mark | Piniak, Gregory A. | Cosentino-Manning, Natalie
Existing literature illustrates inconsistent responses of seagrasses to oil exposure, both in the field and in the laboratory. Here, we add a new study that combined morphometric, demographic and photophysiology assessments to determine the potential oiling impacts to eelgrass (Zostera marina) from the 2007 Cosco Busan event in San Francisco Bay. Shoot densities, reproductive status, and rhizome elongation of Z. marina were examined at sites with pre-spill data, and eelgrass photosynthetic efficiency was measured post-spill. Shoot densities and percent elongation of rhizome internodes formed after the oil spill varied but with no consistent relationship to adjacent shoreline cleanup assessment team (SCAT) oiling categories. Similarly, differences in seagrass photosynthetic efficiency were not consistent with SCAT oiling categories. While thresholds for negative impacts on seagrass in general remain to be defined, conclusive oiling indicators for degree and duration of exposure would be important considerations and need examination under controlled study.
اظهر المزيد [+] اقل [-]Modelling and assessment of accidental oil release from damaged subsea pipelines النص الكامل
2017
Li, Xinhong | Chen, Guoming | Zhu, Hongwei
This paper develops a 3D, transient, mathematical model to estimate the oil release rate and simulate the oil dispersion behavior. The Euler-Euler method is used to estimate the subsea oil release rate, while the Eulerian-Lagrangian method is employed to track the migration trajectory of oil droplets. This model accounts for the quantitative effect of backpressure and hole size on oil release rate, and the influence of oil release rate, oil density, current speed, water depth and leakage position on oil migration is also investigated in this paper. Eventually, the results, e.g. transient release rate of oil, the rise time of oil and dispersion distance are determined by above-mentioned model, and the oil release and dispersion behavior under different scenarios is revealed. Essentially, the assessment results could provide a useful guidance for detection of leakage positon and placement of oil containment boom.
اظهر المزيد [+] اقل [-]Impact of kelp cultivation on the Ecological Status of benthic habitats and Zostera marina seagrass biomass النص الكامل
2017
Walls, A.M. | Kennedy, R. | Edwards, M.D. | Johnson, M.P.
The Ecological Status of subtidal benthic communities within a commercial kelp farm on the southwest coast of Ireland was not impacted by macroalgal cultivation. Additionally, there was no effect on the biomass of Zostera marina, a key habitat under the EU Habitats Directive and OSPAR Commission. However, sediment grain size and total organic matter (TOM) were influenced by abiotic and biotic aspects of the farm. A temporal effect on univariate and multivariate species data, Infaunal Quality Index (IQI) and Z. marina biomass was observed. This effect was likely a community response to high storm disturbance in winter 2013/14.The use of IQI to assess the impact of macroalgal cultivation on benthic communities is a novel approach. This study supports a view that environmental impacts of macroalgal cultivation are relatively benign compared to other forms of aquaculture. Further research must be conducted to understand all interactions between aquaculture activities and the environment.
اظهر المزيد [+] اقل [-]Toxic metals biomonitoring based on prey-predator interactions and environmental forensics techniques: A study at the Romanian-Ukraine cross border of the Black Sea النص الكامل
2017
Strungaru, Stefan-Adrian | Nicoară, Mircea | Teodosiu, Carmen | Micu, Dragos | Plavan, Gabriel
Marine cross-border areas are ideal for monitoring pollutants so as to increase ecosystems protection. This study was conducted at the Romanian-Ukraine border of the Black Sea to reveal evidence of contamination with toxic metals based on biomonitoring of: cadmium, lead, total chromium, nickel and copper at different water depths and prey-predator interactions, combined with environmental forensics techniques of biological sampling and separation in witnesses size groups. The species used were Mytilus galloprovincialis L. and Rapana venosa V. collected at 17.5m, 28m and 35m depth. An atomic absorption spectrometer with a high-resolution continuum source and graphite furnace was used for toxic metals quantification in various samples: sediments, soft tissue, stomach content, muscular leg, hepatopancreas. The best sample type, based on the pathology of metal location and bioaccumulation, is the hepatopancreas from R. venosa that proved a significant decrease of cadmium and lead at lower depths.
اظهر المزيد [+] اقل [-]Temporal evolution of the environmental quality of the Vallona Lagoon (Northern Mediterranean, Adriatic Sea) النص الكامل
2017
Maggi, Chiara | Berducci, Maria Teresa | Di Lorenzo, Bianca | Dattolo, Manuela | Cozzolino, Antonella | Mariotti, Silvia | Fabrizi, Valerio | Spaziani, Roberta | Virno Lamberti, Claudia
Guidance Document 25/2010, suggests sediment and biota are the most suitable matrices for the trend monitoring purpose, because they integrate the pollution over time and space. So, from 2005 to 2014, the sediment and biota concentrations of heavy metals (As, Cd, Cr, Hg, Ni, Pb) were analysed in the Vallona Lagoon (northern Adriatic Sea, Italy), widely used for intensive and extensive bivalve farming. The contamination levels in sediment and biota were compared with Environmental Quality Standard (EQS) and threshold levels (TL) for human health.The results identified critical issues related to Cd in sediment samples as well as to Hg and Pb in biota which were not only ascribable to the physiological and seasonal variability of organisms. The Cr and Ni levels in sediment were higher than the EQS. However, the concentration increases at biota stations close to sites where EQS excesses were observed in sediment were not verified.
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