خيارات البحث
النتائج 1181 - 1190 من 3,991
Mobile monitoring of particulate matter: State of art and perspectives
2016
Gozzi, Fernando | Della Ventura, Giancarlo | Marcelli, A.
Due to the socio-economic impact and the consequences on human health, the pollution associated to Particulate Matter (PM) represents one of the main emergences at a global scale. For these reasons, in the last decade we assisted to a continuously increasing interest in the mobile monitoring of PM on a regional and a local scale. Here we summarize the current status in this field, outlining the critical issues and the perspectives. The growing availability of instruments designed and optimized to the real-time monitoring of the air quality, considerably increased the spatial and temporal resolution of available datasets, actually improving air pollution maps and forecast models. However, several issues are still unresolved, particularly in terms of data representativeness. Indeed, the future PM monitoring devices have to be designed to support the decisional process but also the management of environmental emergencies in urban and industrial areas. The future of these devices is certainly the development of compact systems that will make possible a real-time characterization of size distribution, morphology, and chemical composition of the airborne particles.
اظهر المزيد [+] اقل [-]Measurement of aerosol nanoparticles from a combustion particle generator by using three types of dilutors
2016
Lee, Byung Uk | Bae, Gwi Nam
Ultrafine aerosol nanoparticles created from combustion were measured by using three types of dilutors: a simple mixing dilutor, an ejector dilutor, and a rotational disk dilutor. The original particle size distribution from combustion was compared to the estimated distribution from these dilutors. The results showed that ultrafine aerosol nanoparticles maintained their particle size distribution, while particle concentrations decreased 10–20 fold in the dilution processes. Therefore, the dilutors not only diluted the aerosol nanoparticle concentration to the level of the measurement devices, but also helped estimate the shape of aerosol particle size distribution, particularly for ultrafine aerosol nanoparticles from combustion.
اظهر المزيد [+] اقل [-]Determination of ciprofloxacin in Jiaozhou Bay using molecularly imprinted solid-phase extraction followed by high-performance liquid chromatography with fluorescence detection
2016
Lian, Ziru | Wang, Jiangtao
A high selective pre-treatment method for the cleanup and preconcentration of ciprofloxacin in natural seawater samples was developed based on molecularly imprinted solid-phase extraction (MISPE). The ciprofloxacin imprinted polymers were synthesized and the characteristics of obtained polymers were evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy and binding experiments. The imprinted materials showed high adsorption ability for ciprofloxacin and were applied as special solid-phase extraction sorbents for selective separation of ciprofloxacin. An off-line MISPE procedure was optimized and the developed MISPE method allowed direct purification and enrichment of the ciprofloxacin from the aqueous samples prior to high-performance liquid chromatography analysis. The recoveries of spiked seawater on the MISPE cartridges ranged from 75.2 to 112.4% and the relative standard deviations were less than 4.46%. Five seawater samples from Jiaozhou Bay were analyzed and ciprofloxacin was detected in two samples with the concentrations of 0.24 and 0.38μgL−1, respectively.
اظهر المزيد [+] اقل [-]Plastic ingestion by Atlantic cod (Gadus morhua) from the Norwegian coast
2016
Bråte, Inger Lise N. | Eidsvoll, David P. | Steindal, Calin Constantin | Thomas, Kevin V.
This study documents the occurrence of microplastic (<5mm), mesoplastics (5–20mm) and macroplastic (>20mm) in Atlantic cod (Gadus morhua), a common and economically important species of marine fish in Norway. Fish stomachs (n=302) were examined from six different locations along the coast of Norway. Three percent of the individual stomachs contained items identified by Fourier transform infrared spectroscopy (FTIR) as synthetic polymers. Bergen City Harbour was a hotspot with 27% of the cod examined found to contain plastic. Polyester was the most frequently detected polymer. All bar one of the stomachs that contained plastic were full of organic stomach content, suggesting a plastic gut clearance rate similar to the ingested food. It is proposed that stomach fullness is an important metric in order to avoid underestimations when assessing the levels of microplastic ingested by fish.
اظهر المزيد [+] اقل [-]Seasonal variation in diffusive exchange of polycyclic aromatic hydrocarbons across the air–seawater interface in coastal urban area
2016
Kim, Seung-Kyu | Chae, Doo Hyun
Concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) in air–seawater interface were measured over 1year in the coastal region of Incheon, South Korea. Most individual PAHs and total PAHs in air displayed statistically significant negative correlations with temperature, but not significant in seawater. Less hydrophobic compounds with three rings were at or near equilibrium in summer, while PAHs with four to six rings were in disequilibrium in all seasons, with higher fugacity gradients in colder seasons and for more hydrophobic compounds. Differently from fugacity gradients, the highest net fluxes occurred for some three- and four-ring PAHs showing the highest atmospheric concentrations. Net gaseous exchange, which was higher in winter, occurred from air to seawater with an annual cumulative flux of 2075μg/m2/year (for Σ15PAHs), indicating that atmospheric PAHs in this region, originating from coal/biomass combustion, can deteriorate the quality of seawater and sediment.
اظهر المزيد [+] اقل [-]Sensitivity of online coupled model to extreme pollution event over a mega city Delhi
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.
اظهر المزيد [+] اقل [-]Co-selection of antibiotic and metal(loid) resistance in gram-negative epiphytic bacteria from contaminated salt marshes
2016
Henriques, Isabel | Tacão, Marta | Leite, Laura | Fidalgo, Cátia | Araújo, Susana | Oliveira, Cláudia | Alves, Arthur
The goal of this study was to investigate co-selection of antibiotic resistance in gram-negative epiphytic bacteria. Halimione portulacoides samples were collected from metal(loid)-contaminated and non-contaminated salt marshes. Bacterial isolates (n=137) affiliated with Vibrio, Pseudomonas, Shewanella, Comamonas, Aeromonas and with Enterobacteriaceae. Vibrio isolates were more frequent in control site while Pseudomonas was common in contaminated sites. Metal(loid) and antibiotic resistance phenotypes varied significantly according to site contamination, and multiresistance was more frequent in contaminated sites. However, differences among sites were not observed in terms of prevalence or diversity of acquired antibiotic resistance genes, integrons and plasmids. Gene merA, encoding mercury resistance, was only detected in isolates from contaminated sites, most of which were multiresistant to antibiotics. Results indicate that metal(loid) contamination selects for antibiotic resistance in plant surfaces. In salt marshes, antibiotic resistance may be subsequently transferred to other environmental compartments, such as estuarine water or animals, with potential human health risks.
اظهر المزيد [+] اقل [-]Spatial–temporal trend and health implications of polycyclic aromatic hydrocarbons (PAHs) in resident oysters, South China Sea: A case study of Eastern Guangdong coast
2016
Yu, Zi-Ling | Lin, Qin | Gu, Yang-Guang | Ke, Chang-Liang | Sun, Run-Xia
Spatial and temporal distributions of polycyclic aromatic hydrocarbons (PAHs) were investigated in Eastern Guangdong coast, China. Total PAH concentrations in oysters ranged from 231 to 1178ng/g with a mean concentration of 622ng/g dry weight. Compared with other bays and estuaries, PAH levels in oysters were moderate. Spatial distribution of PAHs was site specific, with relatively high PAH concentrations observed in Zhelin Bay and Kaozhouyang Bay. Based on the Spearman test analysis, only PAH concentration in oysters from Jiazi Harbor showed a significant increasing trend (P<0.05). Three-ring PAHs were the most abundant, accounting for 54.2%–88.4% of total PAHs. Diagnostic ratios suggested that PAHs were derived mainly from petroleum origin. BaP and ∑4PAH concentrations were well within the European Union limits (5ng/g and 30ng/g wet weight, respectively). The incremental lifetime cancer risks (ILCR) for PAHs were <10−5, indicating that the adverse health risks associated with oyster consumption in this area were minimal.
اظهر المزيد [+] اقل [-]Influence of enhancing electrolytes on the removal efficiency of heavy metals from Gabes marine sediments (Tunisia)
2016
Missaoui, Amel | Said, Imen | Lafhaj, Zoubeir | Hamdi, Essaieb
This study focused on the feasibility of the treatment of heavy metals-contaminated sediments from Gabes harbor (Tunisia) using enhanced electrokinetic process. It presented a laboratory short-time electrokinetic experiment. The enhancing agents, as citric, acetic acids and sodium dodecyl sulfate (SDS) were used regarding their low environmental hazard. The electrokinetic cell was specially designed in order to elaborate two experiments at the same time. This paper is composed of three parts. The first part introduces the characterization of Gabes sediments. The second part describes the design of laboratory electrokinetic cell and the followed methods. The third part is dedicated to the results analysis. Treatment efficiency revealed that more than 80% of lead was removed from Gabes marine sediments. The reduction of cooper concentration, in sediments after treatment, ranged from 74 to 87%. Despite, the high removal of cadmium that ranged from 58 to 79%, treated sediments presented Cd concentration above the threshold limit.
اظهر المزيد [+] اقل [-]Identification and quantification of microplastics using Nile Red staining
2016
Shim, Won Joon | Song, Young Kyoung | Hong, Sang Hee | Jang, Mi
We investigated the applicability of Nile Red (NR), a fluorescent dye, for microplastic analysis, and determined the optimal staining conditions. Five mg/L NR solution in n-hexane effectively stained plastics, and they were easily recognized in green fluorescence. The NR staining method was successfully applied to micro-sized polyethylene, polypropylene, polystyrene, polycarbonate, polyurethane, and poly(ethylene-vinyl acetate), except for polyvinylchloride, polyamide and polyester. The recovery rate of polyethylene (100–300μm) spiked to pretreated natural sand was 98% in the NR stating method, which was not significantly (p<0.05) different with FT-IR identification. The NR staining method was suitable for discriminating fragmented polypropylene particles from large numbers of sand particles in laboratory weathering test samples. The method is straightforward and quick for identifying and quantifying polymer particles in the laboratory controlled samples. Further studies, however, are necessary to investigate the application of NR staining to field samples with organic remnants.
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