خيارات البحث
النتائج 721 - 730 من 1,301
The dilution and dispersion of ballast water discharged into Goderich Harbor
2011
Wells, Mathew G. | Bailey, Sarah A. | Ruddick, B. (Barry)
Observations are presented on dilution and dispersion rates of ballast water discharged under normal operational conditions at the semi-enclosed port of Goderich, Ontario. The ballast water was tagged with Rhodamine-WT dye and microscopic magnetically-attractive tracer particles. Maximum concentrations of dye immediately after discharge were diluted to 1–5% of initial ballast tank concentrations, and within 3days had decreased to less than 0.1% of initial concentrations. Inside the harbor, there was 10–20% of the ballast water still present after 2days, consistent with a flushing rate of 0.8–1.15day⁻¹. Magnetic particles were collected up to 7.5km outside the harbor after one day, consistent with a dilution factor of order 10⁵ outside the harbor. The results of this study are discussed in the context of ballast water discharge standards proposed by the International Maritime Organization to minimize the introduction of aquatic nonindigenous species through ships’ ballast water and sediments.
اظهر المزيد [+] اقل [-]Marine-derived filamentous fungi and their potential application for polycyclic aromatic hydrocarbon bioremediation
2011
Passarini, Michel R.Z. | Rodrigues, Marili V.N. | Silva, Manuela da | Sette, Lara D.
Eight marine-derived fungi that were previously selected for their abilities to decolorize RBBR dye were subjected to pyrene and benzo[a]pyrene degradation. The fungus Aspergillus sclerotiorum CBMAI 849 showed the best performance with regard to pyrene (99.7%) and benzo[a]pyrene (76.6%) depletion after 8 and 16days, respectively. Substantial amounts of benzo[a]pyrene (>50.0%) depletion were also achieved by Mucor racemosus CBMAI 847. Therefore, these two fungal strains were subjected to metabolism evaluation using the HPLC-DAD-MS technique. The results showed that A. sclerotiorum CBMAI 849 and M. racemosus CBMAI 847 were able to metabolize pyrene to the corresponding pyrenylsulfate and were able to metabolize benzo[a]pyrene to benzo[a]pyrenylsulfate, suggesting that the mechanism of hydroxylation is mediated by a cytochrome P-450 monooxygenase, followed by conjugation with sulfate ions. Because these fungi were adapted to the marine environment, the strains that were used in the present study are considered to be attractive targets for the bioremediation of saline environments, such as ocean and marine sediments that are contaminated by PAHs.
اظهر المزيد [+] اقل [-]Eutrophication and hypoxia in four streams discharging in Guanabara Bay, RJ, Brazil, a case study
2011
Aguiar, Valquiria Maria de Carvalho | Neto, José Antônio Baptista | Rangel, Carlos Marclei
Four streams in the city of São Gonçalo, were sampled to evaluate their potential as sources of nutrients to Guanabara Bay aiming to contribute with the government program to decrease the levels of pollution in this area. Imbuaçu, Guaxindiba, Marimbondo and Brandoas streams were sampled in 2007, 2008 and 2009. The streams revealed to be hipereutrophic with severe limitation of primary production by nitrogen, as shown by the N/P molar ratio. Phosphate levels were abnormally high varying between 4.35 and 130.82μM, whereas nitrate and nitrite ranged from 0.06 to 54.05μM and from 0.28 to 19.23μM, respectively. The streams also presented severe hypoxia and anoxia, with oxygen values varying from non-detected to 3.72mll⁻¹. Heavy loads of particulate suspended material were recorded in the studied streams, ranging between 6.00 and 400.00mgl⁻¹. The streams were considered inexorable sources of nutrients, enhancing the severe eutrophication process in Guanabara Bay.
اظهر المزيد [+] اقل [-]The factors controlling the partitioning of polybrominated diphenyl ethers and polychlorinated biphenyls in the water-column of the Pearl River Estuary in South China
2011
Chen, Man-Ying | Yumei, | Luo, Xiao-Jun | Chen, She-Jun | Mai, Bi-Xian
In this study, the distribution and partition of polybrominateddiphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in water from the Pearl River Estuary were investigated. A seasonal dependence for dissolved and particle phase PCB and PBDE levels was observed. A high dissolved phase level occurred in the dry season. The positive correlation between POC content in the particles and phase distribution coefficients (Kₚ) suggested that POC may play an important role in determining the partition of PBDEs and PCBs. A linear correlation between the observed log KOC and log KOW for PBDEs and PCBs was found with slopes less than one. The observed log KOC values were lower than the predicted log KOC values for PBDEs (except for BDE28). The log KOC values were higher than the predicted values for PCBs. A combination of sorption to colloids (10–98% for PBDEs and less than 25% for PCBs) and adsorption to BC was responsible for this observation.
اظهر المزيد [+] اقل [-]Uranium pollution in an estuary affected by pyrite acid mine drainage and releases of naturally occurring radioactive materials
2011
Villa, M. | Manjón, G. | Hurtado, S. | García-Tenorio, R.
After the termination of phosphogypsum discharges to the Huelva estuary (SW Spain), a unique opportunity was presented to study the response of a contaminated environmental compartment after the cessation of its main source of pollution. The evolution over time of uranium concentrations in the estuary is presented to supply new insights into the decontamination of a scenario affected by Naturally Occurring Radioactive Material (NORM) discharges. The cleaning of uranium isotopes from the area has not taken place as rapidly as expected due to leaching from phosphogypsum stacks. An in-depth study using various techniques of analysis, including ²³⁴U/²³⁸U and ²³⁰Th/²³²Th ratios and the decreasing rates of the uranium concentration, enabled a second source of uranium contamination to be discovered. Increased uranium levels due to acid mine drainage from pyrite mines located in the Iberian Pyrite Belt (SW Spain) prevent complete uranium decontamination and, therefore, result in levels nearly twice those of natural background levels.
اظهر المزيد [+] اقل [-]Sorption–desorption kinetics and toxic cell concentration in marine phytoplankton microalgae exposed to Linear Alkylbenzene Sulfonate
2011
Renaud, Florent | Oberhänsli, François | Teyssié, Jean-Louis | Miramand, Pierre | Temara, Ali | Warnau, Michel
Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C₁₂-LAS congeners were studied in controlled conditions (2–3500μg C₁₂LAS/L) in five marine phytoplanktonic species, using standardized methods. IC₅₀ values ranged from 0.5 to 2mg LAS/L. Sorption of ¹⁴C₁₂-6 LAS isomer was measured at environmentally relevant trace levels (4μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5h in the order dinoflagellate>diatoms>green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24h. Toxic cell concentration was 0.38±0.09mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms.
اظهر المزيد [+] اقل [-]Light-induced bird strikes on vessels in Southwest Greenland
2011
Merkel, Flemming Ravn | Johansen, Kasper Lambert
Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2–3 winters (2006–2009) from navy vessels, cargo vessels and trawlers (total n=19). Forty-one incidents were reported: mainly close to land (<4km, 78%), but one as far offshore as 205km. Up to 88 birds were reported killed in a single incident. All occurred between 5p.m. and 6a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland.
اظهر المزيد [+] اقل [-]Pathogenic fungi: An unacknowledged risk at coastal resorts? New insights on microbiological sand quality in Portugal
2011
Sabino, Raquel | Veríssimo, Cristina | Cunha, Maria Ana | Wergikoski, Bela | Ferreira, Filipa C. | Rodrigues, Raquel | Parada, Helena | Falcão, Leonor | Rosado, Laura | Pinheiro, Catarina | Paixão, Eleonora | Brandão, João
Whilst the potential impact on beach users from microorganisms in water has received considerable attention, there has been relatively little investigation into microbial contaminants in sand. Thirty three beaches across Portugal were analyzed during a five year period (2006–2010) to determine the presence of yeasts, pathogenic fungi, dermatophytes, total coliforms, Escherichia coli and intestinal enterococci in sand. Our results showed that 60.4% of the samples were positive for fungi and that 25.2% were positive for the bacterial parameters. The most frequent fungal species found were Candida sp. and Aspergillus sp., whereas intestinal enterococci were the most frequently isolated bacteria. Positive associations were detected among analyzed parameters and country-regions but none among those parameters and sampling period. Regarding threshold values, we propose 15cfu/g for yeasts, 17cfu/g for potential pathogenic fungi, 8cfu/g for dermatophytes. Eighty four cfu/g for coliforms, 250cfu/g for E. coli, and 100cfu/g for intestinal enterococci.
اظهر المزيد [+] اقل [-]Effects of macroalgal blooms on carbon and nitrogen biogeochemical cycling in photoautotrophic sediments: An experimental mesocosm
2011
García-Robledo, E. | Corzo, A.
The effects of floating macroalgae (250gDWm⁻²) on photoautotrophic microbenthos were studied in a flow-through mesocosm with a parallel mesocosm without macroalgae serving as Control. Vertical microprofiles of O₂ at the sediment–water interface showed a immediate and complete suppression of photosynthetic activity of microphytobenthos (MPB) under the macroalgal canopy, resulting in a shift of benthic metabolism from autotrophic to heterotrophic. MPB abundance and chlorophyll a content decreased and a change from a diatom-dominated to cyanobacteria-dominated community was observed. Inorganic nitrogen nutrients´ concentrations increased in the porewater as a result of the inhibition of MPB nutrient demand, leading to an increase in net ammonification and anaerobic NOₓ ⁻ consumption rates. No organic matter transfer from macroalgae to the sediment was detected, resulting in a net consumption of the carbon and nitrogen stored in the sediment. In consequence, sediment was progressively impoverished in nitrogen, reducing sediment nutrient regeneration.
اظهر المزيد [+] اقل [-]Oil spill detection with fully polarimetric UAVSAR data
2011
Liu, Peng | Li, Xiaofeng | Qu, John J. | Wang, Wenguang | Zhao, Chaofang | Pichel, William
In this study, two ocean oil spill detection approaches based on four scattering matrices measured by fully polarimetric synthetic aperture radar (SAR) are presented and compared. The first algorithm is based on the co-polar correlation coefficient, ρ, and the scattering matrix decomposition parameters, Cloud entropy (H), mean scattering angle (α) and anisotropy (A). While each of these parameters has oil spill signature in it, we find that combining these parameters into a new parameter, F, is a more effective way for oil slick detection. The second algorithm uses the total power of four polarimetric channels image (SPAN) to find the optimal representation of the oil spill signature. Otsu image segmentation method can then be applied to the F and SPAN images to extract the oil slick features. Using the L-band fully polarimetric Uninhabited Aerial Vehicle – synthetic aperture radar (UAVSAR) data acquired during the 2010 Deepwater Horizon oil spill disaster event in the Gulf of Mexico, we are able to successfully extract the oil slick information in the contaminated ocean area. Our result shows that both algorithms perform well in identifying oil slicks in this case.
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