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Результаты 961-970 из 3,197
Failure of the public health testing program for ballast water treatment systems
2015
Cohen, Andrew N. | Dobbs, Fred C.
Since 2004, an international testing program has certified 53 shipboard treatment systems as meeting ballast water discharge standards, including limits on certain microbes to prevent the spread of human pathogens. We determined how frequently certification tests failed a minimum requirement for a meaningful evaluation, that the concentration of microbes in the untreated (control) discharge must exceed the regulatory limit for treated discharges. In 95% of cases where the result was accepted as evidence that the treatment system reduced microbes to below the regulatory limit, the discharge met the limit even without treatment. This shows that the certification program for ballast water treatment systems is dysfunctional in protecting human health. In nearly all cases, the treatment systems would have equally well “passed” these tests even if they had never been turned on. Protocols must require minimum concentrations of targeted microbes in test waters, reflecting the upper range of concentrations in waters where ships operate.
Показать больше [+] Меньше [-]Indoor environmental quality in chemistry and chemical engineering laboratories at Izmir Institute of Technology
2015
Indoor air pollution in university research laboratories may be important to building occupants, especially for those who work in the laboratories. In this study, indoor air quality (IAQ) and indoor environmental comfort were investigated in research laboratories of two departments at a university. PM2.5, PM10, TVOC (total volatile organic compounds), and CO concentrations, and three comfort variables which are temperature, relative humidity, and CO2 were measured. PM2.5 concentration was determined gravimetrically by collecting particles on glass fiber filters, whereas the remaining pollutants and comfort variables were measured using a monitoring device. IAQ measurements showed that levels of all pollutants were under the limits in both of the departments except for TVOC in one laboratory which had a mean concentration of 182ppb. The comfort variables were in the comfort ranges for laboratories in both of the departments except for temperature in one laboratory with a mean value of 30 °C. In conclusion, measures are needed for extensive uses of organic solvents because ventilation may not be sufficient to keep VOC concentrations within the limits, and to provide thermal comfort.
Показать больше [+] Меньше [-]Comparisons of GM (1,1), and BPNN for predicting hourly particulate matter in Dali area of Taichung City, Taiwan
2015
Chen, Li | Pai, Tzu-Yi
This paper represents the first study to compare seven types of first–order and one–variable grey differential equation model [abbreviated as GM (1, 1)] and back-propagation artificial neural network (BPNN) for predicting hourly particulate matter (PM) including PMio and PM2.5 concentrations in Dali area of Taichung City, Taiwan. Their prediction performance was also compared. The results indicated that the minimum mean absolute percentage error (MAPE), mean squared error (MSE), and root mean squared error (RMSE) was 16.76%, 132.95, and 11.53, respectively for PM10 prediction. For PM2.5 prediction, the minimum MAPE, MSE, and RMSE value of 21.64%, 40.41, and 6.36, respectively could be achieved. All statistical values revealed that the predicting performance of GM (1, 1, x(0)), GM (1, 1, a), and GM (1, 1, b) outperformed other GM (1, 1) models. According to the results, it revealed that GM (1, 1) could predict the hourly PM variation precisely even comparing with BPNN.
Показать больше [+] Меньше [-]Rapid physical and chemical transformation of traffic-related atmospheric particles near a highway
2015
Jeong, Cheol-Heon | Evans, Greg J. | Healy, Robert M. | Jadidian, Parnian | Wentzell, Jeremy | Liggio, John | Brook, Jeffrey R.
The health of a substantial portion of urban populations is potentially being impacted by exposure to traffic–related atmospheric pollutants. To better understand the rapid physical and chemical transformation of these pollutants, the number size distributions of non–volatile traffic–related particles were investigated at different distances from a major highway. Particle volatility measurements were performed upwind and downwind of the highway using a fast mobility particle sizing spectrometer with a thermodenuder on a mobile laboratory. The number concentration of non–denuded ultrafine particles decreased exponentially with distance from the highway, whereas a more gradual gradient was observed for non–volatile particles. The non–volatile number concentration at 27 m was higher than that at 280 m by a factor of approximately 3, and the concentration at 280 m was still higher than that upwind of the highway. The proportion of non–volatile particles increased away from the highway, representing 36% of the total particle number at 27 m, 62% at 280 m, and 81% at the upwind site. A slight decrease in the geometric mean diameter of the non–volatile particle size distributions from approximately 35 nm to 30 nm was found between 27 m and 280 m, in contrast to the growth of non–denuded particles with increasing distance from the highway. Single particle analysis results show that the contribution of elemental carbon (EC)–rich particle types at 27 m was higher than the contribution at 280 m by a factor of approximately 2. The findings suggest that people living or spending time near major roadways could be exposed to elevated number concentrations of nucleation–mode volatile particles (<30 nm), Aitken–mode non–volatile particles (30-100 nm), and EC–rich fine–mode particles (>100 nm). The impact of the highway emissions on air quality was observable up to 300 m.
Показать больше [+] Меньше [-]High catalytic activity of Pt–Pd containing USY zeolite catalyst for low temperature CO oxidation from industrial off gases
2015
Lokhande, Suchita | Doggali, Pradeep | Rayalu, Sadhana | Devotta, Sukumar | Labhsetwar, Nitin
Small amounts (0.15wt%) of platinum and palladium were incorporated in porous, high surface area, ultra–stable H–USY–Zeolite by ion exchange method, and their catalytic activity was studied for carbon monoxide (CO) oxidation reaction, under various conditions of industrial importance. The catalyst was characterized by p–XRD, chemical analysis, SEM, TEM, evaluated for catalytic activity using a steady state, fixed bed catalytic reactor. The catalysts show high CO oxidation activity and it was possible to convert 0.044 mmols of CO per gram of catalyst at 120 °C, at a space velocity of 60 000 h−1 and with 100 ppm CO concentration in feed gas. The high catalytic activity of this noble metal catalyst also appears to be a factor of porous structure of zeolite facilitating mass transfer; high surface area as well as highly dispersed catalyst sites of palladium and platinum on zeolite structure. Introduction of acidic sites in zeolites probably makes them more resistant towards SO2, while their surface area and pore characteristics make this catalyst efficient even under high space velocity conditions, thus suggesting the potential of larger pore size zeolites over conventional porous materials for industrial applications.
Показать больше [+] Меньше [-]Influence of dissolved organic nitrogen on Ni bioavailability in Prorocentrum donghaiense and Skeletonema costatum
2015
Huang, Xu-Guang | Li, Hao | Huang, Bang-qin | Liu, Feng-Jiao
Dissolved organic nitrogen (DON) is an important nutrient in the aquatic environment. This study examined the influence of DON addition on the adsorption, absorption, and distribution in macromolecular forms of environmentally deleterious trace metal (Ni) in Prorocentrum donghaiense and Skeletonema costatum over eight days. Ni adsorption and absorption of two species increased with the addition of urea, while Ni adsorption and absorption of two species in the presence of humic substances (HS) decreased. Meanwhile, Ni adsorption and absorption of P. donghaiense were higher than that of S. costatum. Furthermore, Ni contents in the protein fraction of the cells, both in P. donghaiense and S. costatum, were increased with both urea and HS addition. Thus, urea and HS input could impact Ni biogeochemistry and bioavailability, and then affect the biodynamics thereafter.
Показать больше [+] Меньше [-]Long-term functional changes in an estuarine fish assemblage
2015
Baptista, J. | Martinho, F. | Nyitrai, D. | Pardal, M.A. | Dolbeth, M.
The functional diversity of the fish assemblages of the Mondego estuary was studied for a discontinuous 30-year period (1988–2012). During this time, hydrological changes occurred due to man-induced alterations and weather extremes. These changes led to alterations in the structure and function of the fish community. Species richness and functional richness decreased over time and the fish community started to explore new micro-habitats and food resources. Before severe hydrological changes, the community was dominated by pelagic, detritivorous and species with wider salinity ranges. After, the community became dominated by demersal, benthic, piscivorous and marine species. During a drought, omnivorous became increasingly important, reflecting greater possibilities of using available feeding resources. We have also found an increase in sub-tropical species throughout the years, which might be related to gradual temperature increases at a global scale. This study also confirmed estuaries as extremely important for restocking several commercial species.
Показать больше [+] Меньше [-]Rapid deterioration of sediment surface habitats in Bellingham Bay, Washington State, as indicated by benthic foraminifera
2015
Nesbitt, Elizabeth A. | Martin, Ruth A. | Martin, David E. | Apple, Jude
Foraminiferal assemblages in sediment grab samples were utilized to evaluate the impacts of anthropogenic activities on benthic habitats in Bellingham Bay, Washington State, U.S.A. Seventy-three samples taken in 1987, 1997, 2006 and 2010 yielded 35 species of foraminifera from 28 genera. Assemblage composition and diversity data indicate a marked deterioration between 1987 and 2010, contrary to the published Chemical Index, but analogous to the situation with macrobiota. Correlation of diversity with chemical pollutants and metals did not identify any significant correlations, however, an unrelated but highly relevant study of bottom water dissolved oxygen concentrations and pH in Bellingham Bay suggests eutrophication with accompanying hypoxia and acidification may be part of the cause. Thus, the metrics of contamination alone do not adequately characterize habitat viability, and benthic foraminiferal assemblages provide insight into the health of coastal ecosystems.
Показать больше [+] Меньше [-]Assessment of growth, genotoxic responses and expression of stress related genes in the Pacific oyster Crassostrea gigas following chronic exposure to ionizing radiation
2015
Devos, Alexandre | Dallas, Lorna J. | Voiseux, Claire | Lecomte-Pradines, Catherine | Jha, Awadhesh N. | Fiévet, Bruno
Marine organisms are exposed to low doses of anthropogenic contaminants during their entire life. Authorized amounts of radionuclides are discharged in the Channel by nuclear facilities. The Pacific oyster was used to investigate the potential impact of chronic exposure to ionizing radiation. Though we exposed larvae and spat for two weeks to much higher concentrations than those encountered near nuclear facilities, oyster growth and expression of 9 selected stress genes were not significantly changed. To determine potential DNA damage, 2year old oysters were exposed for two weeks to tritiated water. The comet assay was used to evaluate the level of DNA strand breaks in haemocytes, whilst the ‘clearance rate’ was used as a measure of physiological effects. Whilst other parameters did not alter, DNA damage significantly increased. Our results highlight the significance of the observed DNA damage and their potential consequences at higher levels of biological organization.
Показать больше [+] Меньше [-]Characterization of the size-segregated inorganic compounds in Lin'an, a Regional Atmosphere Background Station in the Yangtze River Delta region
2015
Li, Xingru | Zhang, Ruiying | Cong, Xiaoguang | Cheng, Linglong | Liu, Jie | Xu, Honghui
PM1.0 and PM2.5 samples are collected in Lin'an, a Regional Atmosphere Background Station in spring (1–30 April), summer (1–31 July), autumn (1–31 October) and winter (1–31 January) in 2011 to investigate the seasonal characteristics of aerosol pollution in the Yangtze River Delta region. The daily concentrations of water-soluble ions are 24.6 ± 12.0 μg m−3 and 36.6 ± 23.6 μg m−3 in PM1.0 and PM2.5, respectively. SO42−, NO3− and NH4+ are the dominant contributors of water-soluble ions, accounting for 78.6% (spring), 83.5% (summer), 80.6% (autumn) and 81.9% (winter) of the total ions measured in PM1.0 and 80.2% (spring), 85.4% (summer), 78.9% (autumn) and 78.9% (winter) in PM2.5. Seasonal variation is observed, with the lowest ions concentration in winter and the highest one in summer. Nevertheless, the crustal elements (e.g., Ca, Mg, Al, Fe, etc.) have the highest concentrations in spring. Most of the pollution species (Sb, Se, Cd, Pb, As and Zn) have enrichment factor values higher than 100, implying a strong possibility that the air pollution originates from anthropogenic sources and have no evident seasonal variation. The high concentration of K+ and biomass burning potassium (K+BB) in PM2.5 in autumn and winter and its good correlation with black carbon (r = 0.74) suggest that the most severe pollution derives from biomass burning. Factor analysis results indicate that road dust, combustion processes (biomass burning and fossil fuels combustion), sea salt from marine sources and industrial activities are main sources of aerosol pollution in Lin'an.
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