خيارات البحث
النتائج 1151 - 1160 من 4,042
Validation of a new and cost-effective method for mercury vapor removal based on silver nanoparticles coating on micro glassy balls النص الكامل
2016
Shirkhanloo, Hamid | Osanloo, Mahmood | Ghazaghi, Mehri | Hassani, Hamid
Exposure to mercury vapor (Hg0) causes serious health problem in human body. In this study, a novel and applied method based on solid gas phase extraction (SGPE) with silver nanoparticles (AgNPs) coating on micro glassy balls (MGB) was used for Hg0 removal from artificial air. In bench scale set up, the mercury vapor in air composition was produced by mercury vapor generation system (HgGS) and restored in polyethylene air bag (5 Li). In optimized conditions, the mercury vapor in air bag, passed through AgNPs-MGB and absorbed on it. Then, the mercury was completely desorbed from AgNPs by increasing temperature up to 245 °C and online determined by cold vapor atomic absorption spectrometry (CV-AAS). By proposed procedure, the method recovery and capacity of AgNPs were obtained 98% and 91.8 mg g−1, respectively. A simple, fast and low cost synthesis of AgNPs causes, the SGPE introduce as a cost-effective method for mercury vapor removal from air. Validation of methodology was confirmed using ultra trace mercury analyzer (MC3000).
اظهر المزيد [+] اقل [-]Bioavailability and assessment of heavy metal pollution in sediment cores off the Mejerda River Delta (Gulf of Tunis): How useful is a multiproxy approach? النص الكامل
2016
Helali, Mohamed Amine | Oueslati, Walid | Zaaboub, Noureddine | Added, Ayed | Aleya, Lotfi
Three core samples were taken from zones offshore from the Mejerda River Delta (Tunisia) and analyzed for major and trace elements to assess their relationships with organic matter, monosulfides and carbonates, as well as for pollution and bioavailability. Chemical speciation, ∑ SEM/AVS, the enrichment factor (EF) and the geo-accumulation index (I-geo) were used. Iron, cadmium, lead and zinc – the most frequently mined metals in the Mejerda catchment – were found as contaminants in the offshore areas. Estimations of trace element accumulation using the EF and the I-geo index show that lead, and to a lesser extent zinc, are the most polluting metals off the Mejerda outlet. According to their bioavailability, these metals are also the most toxic. Only cadmium is heavily present in delta sediment (EF>100) though deeply sequestrated (100% bound to the residual fraction) and thus presents no toxicity.
اظهر المزيد [+] اقل [-]Marine environmental protection: An application of the nanometer photo catalyst method on decomposition of benzene النص الكامل
2016
Lin, Mu-Chien | Kao, Jui-Chung
Bioremediation is currently extensively employed in the elimination of coastal oil pollution, but it is not very effective as the process takes several months to degrade oil.Among the components of oil, benzene degradation is difficult due to its stable characteristics. This paper describes an experimental study on the decomposition of benzene by titanium dioxide (TiO2) nanometer photocatalysis. The photocatalyst is illuminated with 360-nm ultraviolet light for generation of peroxide ions. This results in complete decomposition of benzene, thus yielding CO2 and H2O. In this study, a nonwoven fabric is coated with the photocatalyst and benzene. Using the Double-Shot Py–GC system on the residual component, complete decomposition of the benzene was verified by 4h of exposure to ultraviolet light. The method proposed in this study can be directly applied to elimination of marine oil pollution. Further studies will be conducted on coastal oil pollution in situ.
اظهر المزيد [+] اقل [-]Oil spill impacts on mangroves: Recommendations for operational planning and action based on a global review النص الكامل
2016
Duke, Norman C.
Mangrove tidal wetland habitats are recognised as highly vulnerable to large and chronic oil spills. This review of current literature and public databases covers the last 6 decades, summarising global data on oil spill incidents affecting, or likely to have affected, mangrove habitat. Over this period, there have been at least 238 notable oil spills along mangrove shorelines worldwide. In total, at least 5.5milliontonnes of oil has been released into mangrove-lined, coastal waters, oiling possibly up to around 1.94millionha of mangrove habitat, and killing at least 126,000ha of mangrove vegetation since 1958. However, there were assessment limitations with incomplete and unavailable data, as well as unequal coverage across world regions. To redress the gaps described here in reporting on oil spill impacts on mangroves and their recovery worldwide, a number of recommendations and suggestions are made for refreshing and updating standard operational procedures for responders, managers and researchers alike.
اظهر المزيد [+] اقل [-]Synoptic weather evolution and climate drivers associated with winter air pollution in New Zealand النص الكامل
2016
Fiddes, S.L. | Pezza, A.B. | Mitchell, T.A. | Kozyniak, K. | Mills, D.
Particulate matter pollution of less than 10 μm in diameter (PM10) is a problem for some regional and urban centres across New Zealand during the winter period when solid fuel (wood and coal) fires are used for home heating. Elevated levels of PM10 concentrations occur during stable atmospheric conditions, when cool air temperatures and low wind speeds allow for a surface inversion to occur and trap PM10. This study examined the relationships between PM10 and local and large-scale synoptic conditions at daily and seasonal scales. Minimum temperature and wind speed were both negatively correlated with PM10 during the winter season, whilst the combination of the two can explain 30–54% of variability in average PM10. Synoptic-scale daily composites of high PM10 days showed the evolution of an anticyclone in the Tasman Sea, with an injection of cool air over New Zealand and persistent south-westerly winds leading to cold and stable conditions on the day of exceedance. Both of these results indicate that there is some potential for predicting days in which atmospheric conditions could favour elevated PM10 concentrations. Furthermore, at the seasonal scale, weaker westerly winds were found to be associated with winters with higher exceedance days, although the relationship is not straightforward. These characteristics can be associated with other, predictable large-scale climate drivers such as the El Niño-Southern Oscillation, and may aid in identifying years in which a higher risk of PM10 pollution events exists.
اظهر المزيد [+] اقل [-]Microbial community structure shifts are associated with temperature, dispersants and nutrients in crude oil-contaminated seawaters النص الكامل
2016
Meng, Long | Liu, Han | Bao, Mutai | Sun, Peiyan
This study tracked structure shifts of bacterial compositions before, during and after invading by crude oil to determine the microbial response and explore how temperature, dispersants and nutrients affect the composition of microbial communities or their activities of biodegradation in artificial marine environment. During petroleum hydrocarbons exposed, the composition and functional dynamics of marine microbial communities were altered, favoring bacteria that could utilize this rich carbon source such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes phyla. Low temperature as a dominant factor decreased bacterial richness and catabolic diversity due to abated enzymes activities in correlation with the process of biodegradation. Dispersants exerted no negative consequences on microbial composition, however, bacterial composition by the Chloroflexi, TM6, OP8, Cyanobacteria and Gemmatimonadetes phyla increased. It seemed that more frequent fertilizer application could be equally safe to bacteria and increased significantly the abundance of bacterial strains but Actinobacteria phyla decreased.
اظهر المزيد [+] اقل [-]Assessment of factors enabling halite formation in a marsh in a humid temperate climate (Ajó Marsh, Argentina) النص الكامل
2016
Carol, Eleonora S. | Álvarez, María del Pilar | Borzi, Guido E.
The formation of evaporites associated with the final stages of the precipitation sequence, such as the case of halite, is frequent in marshes in arid areas, but it is not to be expected in those humid climates. This work, by means of the study of the hydrological, climatic and land use conditions, identifies the factors that allow the formation of saline precipitations in a marsh located in a humid climate area. The results obtained show that the exclusion of the marsh as a result of the embankment is the main reason for the presence of halite. It is to be expected that in the future the growth of the embanked marsh areas, together with the climatic and tidal condition tendencies recorded, will favour a higher rate of formation of evaporite salts. The identification of these factors makes it possible to set basic sustainable management guidelines to avoid soil salinisation.
اظهر المزيد [+] اقل [-]Bioaugmentation strategy employing a microbial consortium immobilized in chitosan beads for oil degradation in mesocosm scale النص الكامل
2016
Dellagnezze, B.M. | Vasconcellos, S.P. | Angelim, A.L. | Melo, V.M.M. | Santisi, S. | Cappello, S. | Oliveira, V.M.
A bacterial consortium composed by four metagenomic clones and Bacillus subtilis strain CBMAI 707, all derived from petroleum reservoirs, was entrapped in chitosan beads and evaluated regarding hydrocarbon degradation capability. Experiments were carried out in mesocosm scale (3000L) with seawater artificially polluted with crude oil. At different time intervals, mesocosms were sampled and subjected to GC-FID and microbiological analyses, as total and heterotrophic culturable bacterial abundance (DAPI and CFU count), biological oxygen demand (BOD) and taxonomic diversity (massive sequencing of 16S rRNA genes). The results obtained showed that degradation of n-alkane hydrocarbons was similar between both treatments. However, aromatic compound degradation was more efficient in bioaugmentation treatment, with biodegradation percentages reaching up to 99% in 30days. Community dynamics was different between treatments and the consortium used in the bioaugmentation treatment contributed to a significant increase in aromatic hydrocarbon degradation.
اظهر المزيد [+] اقل [-]A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs النص الكامل
2016
Stelfox, Martin | Hudgins, Jillian | Sweet, Michael
This review focuses on the effect that ghost gear entanglement has on marine megafauna, namely mammals, reptiles and elasmobranchs. A total of 76 publications and other sources of grey literature were assessed, and these highlighted that over 5400 individuals from 40 different species were recorded as entangled in, or associated with, ghost gear. Interestingly, there appeared to be a deficit of research in the Indian, Southern, and Arctic Oceans; and so, we recommend that future studies focus efforts on these areas. Furthermore, studies assessing the effects of ghost gear on elasmobranchs, manatees, and dugongs should also be prioritised, as these groups were underrepresented in the current literature. The development of regional databases, capable of recording entanglement incidences following a minimum global set of criteria, would be a logical next step in order to analyse the effect that ghost gear has on megafauna populations worldwide.
اظهر المزيد [+] اقل [-]Sensitivity of online coupled model to extreme pollution event over a mega city Delhi النص الكامل
2016
Srinivas, Reka | Panicker, Abhilash S. | Parkhi, Neha S. | Peshin, Sunil K. | Beig, Gufran
Sensitivity of interactive Weather-Chemistry model has been examined to predict the air quality (1 and 3 days in advance) of Indian mega city Delhi during two identical extreme events of Diwali in 2012 and 2013. Analysis is conducted 3 days prior to 3 days later of Diwali day for both events to verify the rapid changes in fine particulate matter (PM2.5) due to widespread display of Diwali fireworks. The model successfully predicted the variability in PM2.5 during 2012 for the entire period of analysis with reasonable accuracy. Although model performed reasonably well until Diwali day in 2013 but it was unable to simulate rapid built up of PM2.5 (1500 μg−3 hourly average) during post Diwali day as it failed to capture unusual mid-night steep temperature gradient followed by a record lowering of boundary layer height. The predictability of the model and its limitation to micrometeorological processes are discussed in detail.
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