خيارات البحث
النتائج 621 - 630 من 1,956
Prevalence and composition of marine debris in Brown Booby (Sula leucogaster) nests at Ashmore Reef النص الكامل
2013
Lavers, Jennifer L. | Hodgson, Jarrod C. | Clarke, Rohan H.
Anthropogenic debris is ubiquitous in the marine environment and has been reported to negatively impact hundreds of species globally. Seabirds are particularly at risk from entanglement in debris due to their habit of collecting food and, in many cases, nesting material off the ocean’s surface. We compared the prevalence and composition of debris in nests and along the beach at two Brown Booby (Sula leucogaster) colonies on Ashmore Reef, Timor Sea, a remote area known to contain high densities of debris transported by ocean currents. The proportion of nests with debris varied across islands (range 3–31%), likely in response to the availability of natural nesting materials. Boobies exhibited a preference for debris colour (white and black), but not type. The ephemeral nature of Brown Booby nests on Ashmore Reef may limit their utility as indicators of marine pollution, however monitoring is recommended in light of increasing demand for plastic products.
اظهر المزيد [+] اقل [-]Assessment of contribution to PM10 concentrations from long range transport of pollutants using WRF/Chem over a subtropical urban airshed النص الكامل
2013
Gupta, Medhavi | Mohan, Manju
A regional chemical transport model was implemented to simulate the Respirable Suspended Particulate Matter (PM10) concentration in order to study the impact of long–range transport of air pollutants over megacity Delhi with due consideration to different geographical domains extending up to entire Asia and corresponding emissions. PM10 concentration levels over megacity Delhi remain persistently high, often exceeding the ambient air quality standards. A chemical transport model namely Weather Research and Forecasting (WRF) model Version 3.2 coupled with chemistry module (WRF/Chem) was utilized with nested domains for this purpose, subsequent to model evaluation for the period during June, 2010 that includes extremely high PM10 concentrations. A highly satisfactory model performance was interpreted based on the several statistical parameters as per the current state of the science and their recommended values. Based on model simulations representing different geographical domains encompassing Asia, India, North India and Delhi and their corresponding emissions, it was clearly reflected that contributions due to emissions of the megacity Delhi alone is 11%–41% and thus remaining (59%–89%) proportion is expected to be contributed from the sources outside of the Delhi region which is significant. It is demonstrated that the WRF/Chem model performs well for a sub–tropical urban airshed though there is scope of improvement for the consistent under– prediction with more refined emission inventories. Nevertheless, this model could be implemented to assess the long– range transport of pollutants so as to adequately address the influence of the remote sources outside the urban airshed. This can serve as an important tool towards planning and implementing the regulatory policies for air pollution control for more effective outcomes.
اظهر المزيد [+] اقل [-]Rapid method demonstration project at four New Jersey marine beaches using real time quantitative Polymerase Chain Reaction (qPCR) النص الكامل
2013
Ferretti, James A. | Tran, Hiep V. | Peterson, Sarah J. | Loftin, Virginia
Real time quantitative Polymerase Chain Reaction (qPCR) was used at four marine bathing beaches in New Jersey as part of a demonstration project to evaluate the potential for use of qPCR as part of a routine beach monitoring program. Split sample analyses for Enterococcus spp. using membrane filtration (MF) and qPCR were performed for 11weeks during the summer of 2011 using swimming advisories based on qPCR results. Comparison of qPCR and MF results from split samples indicated that there was an 82% overall agreement rate between the two methods. Results from the qPCR tests were available by noon the same day of sample collection and swimming advisories were posted on a dedicated website. The qPCR method can be more labor intensive and requires a higher level of training to perform, however, qPCR was able to assess beach water quality in a timelier manner compared to conventional MF techniques.
اظهر المزيد [+] اقل [-]Alert thresholds for monitoring environmental variables: A new approach applied to seagrass beds diversity in New Caledonia النص الكامل
2013
Van Wynsberge, Simon | Gilbert, Antoine | Guillemot, Nicolas | Payri, Claude | Andréfouët, Serge
Monitoring ecological variables is mandatory to detect abnormal changes in ecosystems. When the studied variables exceed predefined alert thresholds, management actions may be required. In the past, alert thresholds have been typically defined by expert judgments and descriptive statistics. Recently, approaches based on statistical power were also used. In New Caledonia, seagrass monitoring is a priority given their vulnerability to natural and anthropic disturbances. To define a suitable monitoring strategy and alert thresholds, we compared a Percentile Based Approach (PBA) and a sensitivity analysis of power (SAP). Both methods defined statistically relevant alert thresholds, but the SAP approach was more robust to spatial and temporal variability of seagrass cover. Moreover, this method characterized the sensitivity of threshold values to sampling efforts, a useful knowledge for managers.
اظهر المزيد [+] اقل [-]Merchant ships discharging unwanted marine species in close proximity of a French aquaculture area: Risks involved النص الكامل
2013
Masson, Daniel | Thomas, Gerard | Genauzeau, Sylvie | Le Moine, Olivier | Derrien, Annick
Merchant ships discharging unwanted marine species in close proximity of a French aquaculture area: Risks involved النص الكامل
2013
Masson, Daniel | Thomas, Gerard | Genauzeau, Sylvie | Le Moine, Olivier | Derrien, Annick
The most important oyster farming area in Europe is in a close proximity of two medium size merchant ports. Cargo ships deballast in this area before loading, releasing unwanted or noxious marine species. During a sampling campaign aboard these arriving ships, we found in some ballast water samples a huge number of potentially toxic dinoflagellates and some potentially pathogenic bacteria. A model was applied to find the potential geographical spread of the discharged ballast water. This model predicts the water to reach highly vulnerable shellfish farmed areas in six to eight days.
اظهر المزيد [+] اقل [-]Merchant ships discharging unwanted marine species in close proximity of a French aquaculture area: Risks involved النص الكامل
2013
Masson, Daniel | Thomas, Gerard | Genauzeau, Sylvie | Le Moine, Olivier | Derrien, Annick
The most important oyster farming area in Europe is in a close proximity of two medium size merchant ports. Cargo ships deballast in this area before loading, releasing unwanted or noxious marine species. During a sampling campaign aboard these arriving ships, we found in some ballast water samples a huge number of potentially toxic dinoflagellates and some potentially pathogenic bacteria. A model was applied to find the potential geographical spread of the discharged ballast water. This model predicts the water to reach highly vulnerable shellfish farmed areas in six to eight days.
اظهر المزيد [+] اقل [-]Analysis of temporal and spatial variability of total column ozone over West Africa using daily TOMS measurements النص الكامل
2013
Oluleye, Ayodeji | Okogbue, Emmanuel Chilekwu
The aim of this study was to examine the temporal and spatial total column ozone distribution in West Africa using Total Ozone Mapping spectrometer (TOMS) daily data for five years between 2001 and 2005 in fifteen locations. In this study, certain significant observations emerged: weather activity particularly the rainfall producing mechanism (dynamic of the wind systems) was responsible for about 62% ozone distribution in the region. Ozone maximum and minimum concentrations over all the stations were 305 DU and 232 DU respectively producing an average range of 73 DU (only about 27.03% of the mean value). Ozone has a seasonal distribution with minimum occurring during the dry season and maximum occurring during the wet season. A decreasing rate of about –0.6 DU/year was found for the region. Interannual ozone characteristics revealed an oscillating feature similar to Quasi – biennial Oscillation (QBO) footprints which indicated the importance of stratosphere – troposphere exchange to ozone distribution in the region. Furthermore, lag of about one or two months occurs between south (lower latitude) and north (higher latitude) monthly ozone maximums.
اظهر المزيد [+] اقل [-]Characterization of mercury in atmospheric particulate matter in the southeast coastal cities of China النص الكامل
2013
Xu, Lingling | Chen, Jinsheng | Niu, Zhenchuan | Yin, Liqian | Chen, Yanting
Although present in a low concentration in the atmosphere, mercury in particulate matter (PHg) plays an important role in the biogeochemical process of mercury. In this study, the mercury concentrations in three size fractions of airborne particulate matters collected from 14 sites (12 urban sites, 1 rural site and 1 remote site) in the southeast coastal cities of China during different seasons in 2010–2011 were investigated. Most of PHg (46.8–71.9%) was concentrated in the finer particles, i.e. PM2.5 (particulate matter ≤2.5 µm in aerodynamic diameter). The average mercury concentrations in PM2.5 were 141.2±128.1 (range of 7.6–956.5), 37.0±19.2 (5.6–89.4), and 24.0±14.6 (3.2– 59.9) pg m–3 at urban, rural, and remote sites during the whole sampling period, respectively. The PHg concentrations were almost at the same level in spring, autumn, and winter, approximately two times of that in summer. PHg concentrations in the atmosphere displayed a significant spatial variation with far higher values in urban areas than those at rural and remote sites. The dry deposition fluxes of total PHg estimated by a theoretical model were 38.3, 47.7, and 58.7 µg m–2 y–1 at Ji’an (JA), Jimei (JM), and Longwen (LW), respectively. The backward air trajectory analysis revealed that the atmospheric PHg concentrations were mainly influenced by air masses from ocean sources that diluted PHg in summer and on contrary from continental sources in other seasons.
اظهر المزيد [+] اقل [-]Using 222Rn to estimate submarine groundwater discharge (SGD) and the associated nutrient fluxes into Xiangshan Bay, East China Sea النص الكامل
2013
Wu, Zijun | Zhou, Huaiyang | Zhang, Shuai | Liu, Yang
Continuous radon (222Rn) monitoring was conducted at two stations (site A and site B) with different perpendicular distance from the shoreline in Xiangshan Bay, East China Sea. Based on a 222Rn balance model (various sources and sinks of 222Rn in coastal water), the average rate of SGD was estimated to be 0.69cm/day and 0.23cm/day for site A and site B, respectively. The results from a nutrient analysis of the groundwater indicate that the associated nutrients fluxes loading through the SGD pathway were 4.27×106mol/day for DIN, 2.24×104mol/day for DIP and 1.82×106mol/day for DSi, respectively, which were comparable to or even higher than the levels observed in the local streams. Therefore, adequate attention should be paid to the importance of SGD as one source of nutrients during the eutrophication control process in this area.
اظهر المزيد [+] اقل [-]Composition of in situ burn residue as a function of weathering conditions النص الكامل
2013
Fritt-Rasmussen, Janne | Ascanius, Birgit Elkjær | Brandvik, Per Johan | Villumsen, Arne | Stenby, Erling H.
Troll B crude oil was weathered under Arctic conditions with different ice coverage: open water, 50% ice and 90% ice. Samples (100mL) were taken during the experiment and tested for ignitability in a burning cell. From each burning a residue sample was taken for analysis. The burning process removed the light compounds eluting before C13. No effect from the prior weathering time or the different ice coverage was seen in the burn residue composition. The content of selected Poly Aromatic Hydrocarbons (PAHs) was determined and it was noted that the concentration of PAHs with more than 4 rings were increased. The source origin of the PAHs was investigated by use of relative ratios of PAH isomers and indicated that some formation of PAHs was additionally taking place during burning.
اظهر المزيد [+] اقل [-]Droplet breakup in subsea oil releases – Part 2: Predictions of droplet size distributions with and without injection of chemical dispersants النص الكامل
2013
Johansen, Øistein | Brandvik, Per Johan | Farooq, Umer
A new method for prediction of droplet size distributions from subsea oil and gas releases is presented in this paper. The method is based on experimental data obtained from oil droplet breakup experiments conducted in a new test facility at SINTEF. The facility is described in a companion paper, while this paper deals with the theoretical basis for the model and the empirical correlations used to derive the model parameters from the available data from the test facility. A major issue dealt with in this paper is the basis for extrapolation of the data to full scale (blowout) conditions. Possible contribution from factors such as buoyancy flux and gas void fraction are discussed and evaluated based on results from the DeepSpill field experiment.
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