خيارات البحث
النتائج 1121 - 1130 من 3,208
Modeling the dispersion of viable and total Escherichia coli cells in the artificial semi-enclosed bathing area of Santa Marinella (Latium, Italy) النص الكامل
2015
Bonamano, S. | Madonia, A. | Borsellino, C. | Stefanì, C. | Caruso, G. | De Pasquale, F. | Piermattei, V. | Zappalà, G. | Marcelli, M.
Coastal areas are strongly affected by episodes of fecal contamination due to polluted water inflows from inadequately treated sewages. The present study aims to investigate the dispersion of Escherichia coli in the artificial semi-enclosed bathing area of Santa Marinella (Latium, Italy) through in situ samplings carried out in summer 2012 and the application of a dynamic model. Collected samples were analyzed by the Culture-Based technique and the Fluorescent Antibody method in order to estimate both the viable culturable cells and the total E. coli population, respectively. The in situ datasets were used to test the proposed modeling approach and simulate the behavior of bacteria as particles subjected, or not, to decay. Next, the flushing time and the computation of the Microbiological Potential Risk Area allowed the evaluation of the contribution of physical and biological processes to coliform dispersion and the related potential risk for bathers.
اظهر المزيد [+] اقل [-]Soil Pollution Due to Irrigation with Arsenic-Contaminated Groundwater: Current State of Science النص الكامل
2015
Gillispie, Elizabeth C. | Sowers, Tyler D. | Duckworth, Owen W. | Polizzotto, Matthew L.
Food with elevated arsenic concentrations is becoming widely recognized as a global threat to human health. This review describes the current state of knowledge of soil pollution derived from irrigation with arsenic-contaminated groundwater, highlighting processes controlling arsenic cycling in soils and resulting arsenic impacts on crop and human health. Irrigation practices utilized for both flooded and upland crops have the potential to load arsenic to soils, with a host of environmental and anthropogenic factors ultimately determining the fate of arsenic. Continual use of contaminated groundwater for irrigation may result in soils with concentrations sufficient to create dangerous arsenic concentrations in the edible portions of crops. Recent advances in low-cost water and soil management options show promise for mitigating arsenic impacts of polluted soils. Better understanding of arsenic transfer from soil to crops and the controls on long-term soil arsenic accumulation is needed to establish effective arsenic mitigation strategies within vulnerable agronomic systems.
اظهر المزيد [+] اقل [-]Spatial outlier detection in the PM10 monitoring network of Normandy (France) النص الكامل
2015
Michel, Bobbia | Michel, Misiti | Yves, Misiti | Jean-Michel, Poggi | Bruno, Portier
We consider hourly PM10 measurements from 22 monitoring stations located in Basse–Normandie and Haute–Normandie regions (France) and also in the neighboring regions. All considered monitoring stations are either urban background stations or rural ones. The paper focuses on the statistical detection of outliers of the hourly PM10 concentrations from a spatial point of view. The general strategy uses a jackknife type approach and is based on the comparison of the actual measurement with some robust spatial prediction. Two spatial predictions are considered: the first one is based on the median of the concentrations of the closest neighboring stations which directly consider weighted concentrations while the second one is based on kriging increments, instead of more traditional pseudo–innovations. The two methods are applied to the PM10 monitoring network in Normandy and are fully implemented by Air Normand (the official association for air quality monitoring in Haute–Normandie) in the Measurements Quality Control process. Some numerical results are provided on recent data from January 1, 2013 to May 31, 2013 to illustrate and compare the two methods.
اظهر المزيد [+] اقل [-]Integrating dispersion modelling and lichen sampling to assess harmful heavy metal pollution around the Karabash copper smelter, Russian Federation النص الكامل
2015
Pollard, Adam S. | Williamson, Ben J. | Taylor, Mark | Purvis, William O. | Goossens, Marc | Reis, Stefan | Aminov, Pavel | Udachin, Valery | Osborne, Nicholas J.
Cu smelting has had a severe impact on the environment around the town of Karabash, Russia. Dispersion modelling has been carried out to estimate atmospheric fallout of metals and metalloids (henceforth termed metals for brevity) from the copper smelter, calibrated and ground-truthed using metal concentrations in transplanted and naturally growing lichens.Lichens (Hypogymnia physodes) were transplanted in June 2011 from a relatively little impacted ‘reference site’ to stations in NE–SW and W–E transects centred on the smelter at Karabash. The transplants were removed during September 2011 and then analysed for As, Cu and Pb. The results were compared with deposition loads estimated using TAPM modelling which was carried out for particles of various sizes, and with simple chemistries, and with the smelter conceptualised as a continuously emitting point source.Variation in the ratio of lichen divided by modelled concentrations was lowest for Pb, ranging from 30.3 to 939.9 and 4.9–107.8 for PM2.5 and PM10, respectively, across eight sample points.The TAPM modelling is in agreement with previous studies that smelter emissions are the major source of environmental Pb deposition around Karabash. Further modelling will be required to determine whether the Pb in the lichens is largely sourced from current smelter airborne emissions or windblown soil particles containing historic additions of Pb.
اظهر المزيد [+] اقل [-]The NET effect of dispersants — a critical review of testing and modelling of surface oil dispersion النص الكامل
2015
Zeinstra-Helfrich, Marieke | Koops, Wierd | Murk, Albertinka J.
Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and transport of the oil.We aim to identify how natural, chemical and mechanical dispersion could be quantified in oil spill models. For each step in the dispersion process, we review available experimental data in order to identify overall trends and propose an algorithm or calculation method. Additionally, the conditions for successful mechanical and chemical dispersion are defined.Two commonly identified key parameters in surface oil dispersion are: oil properties (viscosity and presence of dispersants) and mixing energy (often wind speed). Strikingly, these parameters play a different role in several of the dispersion sub-processes. This may explain difficulties in simply relating overall dispersion effectiveness to the individual parameters.
اظهر المزيد [+] اقل [-]Detection of water quality parameters in Hangzhou Bay using a portable laser fluorometer النص الكامل
2015
Chen, Peng | Pan, Delu | Mao, Zhihua | Tao, Bangyi
A field, light-weight laser fluorometer based on the method of laser induced fluorescence was developed for water quality monitoring. The basic instrument configuration uses a high pulse repetition frequency microchip laser, a confocal reflective fluorescent probe and a broadband hyperspectral micro spectrometer; it weights only about 1.7kg. Simultaneous estimates of three important water quality parameters, namely, chlorophyll a (chl-a), colored dissolved organic matter (CDOM), and total suspended matter (TSM) measured by the laser fluorometer were observed to agree well with those measured by traditional methods (0.27–0.84μgL−3 chl-a, R2=0.88; 0.104–0.295m−1 CDOM absorption, R2=0.90; and 59.8–994.9mgL−3 TSM, R2=0.86) in Hangzhou Bay water. Subsequently, distribution and characteristics of CDOM and chl-a laser fluorescence in Hangzhou Bay were analyzed, which will enhance our understanding of biogeochemical processes in this complex estuarine system at high-resolution, high-frequency and long-term scale.
اظهر المزيد [+] اقل [-]Maternal transfer of organohalogenated compounds in sharks and stingrays النص الكامل
2015
Weijs, Liesbeth | Briels, Nathalie | Adams, Douglas H. | Lepoint, Gilles | Dāsa, Kr̥shṇā | Blust, Ronny | Covaci, Adrian
Maternal transfer of organohalogenated compounds in sharks and stingrays النص الكامل
2015
Weijs, Liesbeth | Briels, Nathalie | Adams, Douglas H. | Lepoint, Gilles | Dāsa, Kr̥shṇā | Blust, Ronny | Covaci, Adrian
Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study provides preliminary data on the POP transfer from pregnant females to offspring of three species (Atlantic stingrays, bonnethead, blacktip sharks) with different reproduction modes (aplacental, placental viviparity). Polychlorinated biphenyl (PCB) levels were generally higher than any other POPs. Stingrays and blacktip shark embryos contained the lowest POP concentrations while bonnetheads and the blacktip adult female had the highest concentrations. Results suggest that POPs are more readily transferred from the mother to the embryo compared to what is transferred to ova in stingrays. Statistically significant differences in levels of selected POPs were found between embryos from the left and right uterus within the same litter as well as between female and male embryos within the same litter for bonnetheads, but not for the blacktip sharks.
اظهر المزيد [+] اقل [-]Maternal transfer of organohalogenated compounds in sharks and stingrays النص الكامل
2015
Weijs, Liesbeth | Briels, Nathalie | Adams, Douglas | Lepoint, Gilles | Das, Krishna | Blust, Ronny | Covaci, Adrian
peer reviewed | Elasmobranchs can bioaccumulate considerable amounts of persistent organic pollutants (POPs) and utilize several reproductive strategies thereby influencing maternal transfer of contaminants. This study provides preliminary data on the POP transfer from pregnant females to offspring of three species (Atlantic stingrays, bonnethead, blacktip sharks) with different reproduction modes (aplacental, placental viviparity). Polychlorinated biphenyl (PCB) levels were generally higher than any other POPs. Stingrays and blacktip shark embryos contained the lowest POP concentrations while bonnetheads and the blacktip adult female had the highest concentrations. Results suggest that are more readily transferred from the mother to the embryo compared to what is transferred to ova in stingrays. Statistically significant differences in levels of selected POPs were found between embryos from the left and right uterus within the same litter as well as between female and male embryos within the same litter for bonnetheads, but not for the blacktip sharks.
اظهر المزيد [+] اقل [-]Studies on crude oil removal from pebbles by the application of biodiesel النص الكامل
2015
Oil residues along shorelines are hard to remove after an oil spill. The effect of biodiesel to eliminate crude oil from pebbles alone and in combination with petroleum degrading bacteria was investigated in simulated systems. Adding biodiesel made oil detach from pebbles and formed oil–biodiesel mixtures, most of which remained on top of seawater. The total petroleum hydrocarbon (TPH) removal efficiency increased with biodiesel quantities but the magnitude of augment decreased gradually. When used with petroleum degrading bacteria, the addition of biodiesel (BD), nutrients (NUT) and BD+NUT increased the dehydrogenase activity and decreased the biodegradation half lives. When BD and NUT were replenished at the same time, the TPH removal efficiency was 7.4% higher compared to the total improvement of efficiency when BD and NUT was added separately, indicating an additive effect of biodiesel and nutrients on oil biodegradation.
اظهر المزيد [+] اقل [-]A spatial–seasonal analysis of the oiling risk from shipping traffic to seabirds in the Aleutian Archipelago النص الكامل
2015
Renner, Martin | Kuletz, Kathy J.
Some of the largest seabird concentrations in the northern hemisphere are intersected by major shipping routes in the Aleutian Archipelago. Risk is the product of the probability and the severity incidents in an area. We build a seasonally explicit model of seabird distribution and combine the densities of seabirds with an oil vulnerability index. We use shipping density, as a proxy for the probability of oil spills from shipping accident (or the intensity chronic oil pollution). We find high-risk (above-average seabird and vessel density) areas around Unimak Pass, south of the Alaska Peninsula, near Buldir Island, and north of Attu Island. Risk to seabirds is greater during summer than during winter, but the month of peak risk (May/July) varies depending on how data is analyzed. The area around Unimak Pass stands out for being at high-risk year-round, whereas passes in the western Aleutians are at high risk mostly during summer.
اظهر المزيد [+] اقل [-]Highly recyclable superhydrophobic sponge suitable for the selective sorption of high viscosity oil from water النص الكامل
2015
Wang, Jintao | Geng, Guihong
Inspired by the adhesion of marine mussels, a kind of superhydrophobic oil sorbent was successfully fabricated by robustly immobilizing the micro/nanostructure layer onto the sponge skeleton. The as-prepared sponges possess excellent hydrophobicity with the water contact angle of 154°, which enables the sponge to selectively absorb various oils floating on water surface. The oil sorption capacities of as-prepared sponge for a series of oils can reach 18.3–46.8g/g. The absorbed oil can be recovered by mechanical squeezing and the resulting sponge can be recycled more than 70 cycles while still keeping high oil sorption capability. More importantly, the obtained sponge has excellent affinity to the high viscosity oils. Therefore, the as-prepared sponge might find practical applications in the large-scale removal of oils especially high viscosity oils from water surface.
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