خيارات البحث
النتائج 191 - 200 من 2,512
Passive sampling of nonpolar contaminants at three deep-ocean sites النص الكامل
2014
Booij, Kees | van Bommel, Ronald | van Aken, Hendrik M. | van Haren, Hans | Brummer, Geert-Jan A. | Ridderinkhof, Herman
Concentrations of polychlorinated biphenyls, polyaromatic hydrocarbons, hexachlorobenzene, and DDE were determined by passive sampling (semipermeable membrane devices) with exposure times of 1–1.5 years at 0.1–5 km depth in the Irminger Sea, the Canary Basin (both North Atlantic Ocean), and the Mozambique Channel (Indian Ocean). The dissipation of performance reference compounds revealed a pronounced effect of hydrostatic pressure on the sampler-water partition coefficients. Concentrations in the Irminger Sea were uniform over the entire water column (0.1–3 km). At the Canary Basin site, concentrations were 2–25 times lower near the bottom (5 km) than at 1.4 km. Concentrations in the Mozambique Channel (0.6–2.5 km) were lower than at the other two locations, and showed a near-bottom maximum. The data suggest that advection of surface waters down to a depth of about 1 km is an important mechanism of contaminant transport into the deep ocean.
اظهر المزيد [+] اقل [-]Quantitative assessments of indoor air pollution and the risk of childhood acute leukemia in Shanghai النص الكامل
2014
Gao, Yu | Zhang, Yan | Kamijima, Michihiro | Sakai, Kiyoshi | Khalequzzaman, Md. | Nakajima, Tamie | Shi, Rong | Wang, Xiaojin | Chen, Didi | Ji, Xiaofan | Han, Kaiyi | Tian, Ying
We investigated the association between indoor air pollutants and childhood acute leukemia (AL). A total of 105 newly diagnosed cases and 105 1:1 gender-, age-, and hospital-matched controls were included. Measurements of indoor pollutants (including nitrogen dioxide (NO2) and 17 types of volatile organic compounds (VOCs)) were taken with diffusive samplers for 64 pairs of cases and controls. Higher concentrations of NO2 and almost half of VOCs were observed in the cases than in the controls and were associated with the increased risk of childhood AL. The use of synthetic materials for wall decoration and furniture in bedroom was related to the risk of childhood AL. Renovating the house in the last 5 years, changing furniture in the last 5 years, closing the doors and windows overnight in the winter and/or summer, paternal smoking history and outdoor pollutants affected VOC concentrations. Our results support the association between childhood AL and indoor air pollution.
اظهر المزيد [+] اقل [-]Assessing the relationship among urban trees, nitrogen dioxide, and respiratory health النص الكامل
2014
Rao, Meenakshi | George, Linda A. | Rosenstiel, Todd N. | Shandas, Vivek | Dinno, Alexis
Modeled atmospheric pollution removal by trees based on eddy flux, leaf, and chamber studies of relatively few species may not scale up to adequately assess landscape-level air pollution effects of the urban forest. A land use regression (LUR) model (R2 = 0.70) based on NO(2) measured at 144 sites in Portland, Oregon (USA), after controlling for roads, railroads, and elevation, estimated every 10 ha (20%) of tree canopy within 400 m of a site was associated with a 0.57 ppb decrease in NO(2). Using BenMAP and a 200 m resolution NO(2) model, we estimated that the NO(2) reduction associated with trees in Portland could result in significantly fewer incidences of respiratory problems, providing a $7 million USD benefit annually. These in-situ urban measurements predict a significantly higher reduction of NO(2) by urban trees than do existing models. Further studies are needed to maximize the potential of urban trees in improving air quality.
اظهر المزيد [+] اقل [-]Ecotoxicity of binary mixtures of Microcystis aeruginosa and insecticides to Daphnia pulex النص الكامل
2014
Asselman, J. | Janssen, C.R. | Smagghe, G. | De Schamphelaere, K.A.C.
In aquatic ecosystems, mixtures of chemical and natural stressors can occur which may significantly complicate risk assessment approaches. Here, we show that effects of binary combinations of four different insecticides and Microcystis aeruginosa, a toxic cyanobacteria, on Daphnia pulex exhibited distinct interaction patterns. Combinations with chlorpyrifos and tetradifon caused non-interactive effects, tebufenpyrad caused an antagonistic interaction and fenoyxcarb yielded patterns that depended on the reference model used (i.e. synergistic with independent action, additive with concentration addition). Our results demonstrate that interactive effects cannot be generalised across different insecticides, not even for those targeting the same biological pathway (i.e. tebufenpyrad and tetradifon both target oxidative phosphorylation). Also, the concentration addition reference model provided conservative predictions of effects in all investigated combinations for risk assessment. These predictions could, in absence of a full mechanistic understanding, provide a meaningful solution for managing water quality in systems impacted by both insecticides and cyanobacterial blooms.
اظهر المزيد [+] اقل [-]Occurrence of antibiotics and antibiotic resistances in soils from wastewater irrigation areas in Beijing and Tianjin, China النص الكامل
2014
Chen, Chaoqi | Li, Jing | Chen, Peipei | Ding, Rui | Zhang, Pengfei | Li, Xiqing
Non-irrigated and wastewater-irrigated soils were collected from five wastewater irrigation areas in Beijing and Tianjin, China. The concentrations of sulfadiazine, sulfamethoxazole, oxytetracycline and chlortetracycline in the soils were determined. Abundances of antibiotic resistant bacteria and corresponding resistance genes were also measured to examine the impact of wastewater irrigation. No significant difference in antibiotic resistance bacteria was observed between irrigated and non-irrigated soils. However, the concentrations of antibiotics and abundances of resistance genes were significantly greater in irrigated soils, indicating that agricultural activities enhanced the occurrence of antibiotics and resistance genes in the soils. In addition, no significant difference was observed between previously and currently wastewater-irrigated soils. Therefore, cessation of wastewater irrigation did not significantly reduce the levels of antibiotic concentrations and resistance gene abundances. Other factors, e.g., manure application, may explain the lack of significant difference in the occurrence of antibiotics and resistance genes between previously and currently wastewater-irrigated soils.
اظهر المزيد [+] اقل [-]Interrogating trees for isotopic archives of atmospheric sulphur deposition and comparison to speleothem records النص الكامل
2014
Wynn, P.M. | Loader, N.J. | Fairchild, I.J.
Palaeorecords which depict changes in sulphur dynamics form an invaluable resource for recording atmospheric pollution. Tree rings constitute an archive that are ubiquitously available and can be absolutely dated, providing the potential to explore local- to regional-scale trends in sulphur availability. Rapid isotopic analysis by a novel “on-line” method using elemental analyser isotope ratio mass spectrometry (EA-IRMS) is developed, achieving sample precision of <0.4‰ using sample sizes of 40 mg wood powder. Tree cores from NE Italy show trends in pollution, evidenced through increasing concentrations of sulphur towards the youngest growth, and inverse trends in sulphur isotopes differentiating modern growth with light sulphur isotopes (+0.7‰) from pre-industrial growth (+7.5‰) influenced by bedrock composition. Comparison with speleothem records from the same location demonstrate replication, albeit offset in isotopic value due to groundwater storage. Using EA-IRMS, tree ring archives form a valuable resource for understanding local- to regional-scale sulphur pollution dynamics.
اظهر المزيد [+] اقل [-]Maternal transfer and embryonic assimilation of trace elements in freshwater turtles after remediation of a coal fly-ash spill النص الكامل
2014
Van Dyke, James U. | Steen, David A. | Jackson, Brian P. | Hopkins, William A.
Oviparous vertebrates maternally transfer elements to their offspring during egg production. Maternal transfer occurs because elements mimic, or are incorporated into, nutrients allocated to eggs, but likely differs among species depending on the quantities of specific nutrients allocated to eggs. Developing embryos are often assumed to assimilate all of the elements allocated to eggs, but this assumption has rarely been tested. We tested the hypothesis that maternal transfer and embryonic assimilation of trace elements differed between two species of freshwater turtles exposed to a recently-remediated coal fly-ash spill. Sternotherus odoratus transferred As, Se, and Zn, while Trachemys scripta transferred As, Hg, Se, Sr, and Zn. Logarithmic non-linear relationships between hatchling and egg concentrations indicated that turtles partially assimilated elements present in eggs. In systems contaminated with multiple trace elements, our data show that maternal transfer and embryonic assimilation are element- and species-specific, and may be inconsistent even among closely-related species.
اظهر المزيد [+] اقل [-]Residential exposure to volatile organic compounds and lung function: Results from a population-based cross-sectional survey النص الكامل
2014
Cakmak, Sabit | Dales, Robert E. | Liu, Ling | Kauri, Lisa Marie | Lemieux, Christine L. | Hebbern, Christopher | Zhu, Jiping
Exposure to residential volatile organic compounds (VOCs) is ubiquitous in homes, and may influence respiratory health with important public health implications. To investigate the association between VOCs measured in residential indoor air and lung function in the Canadian population Cycle 2 of the Canadian Health Measures Survey – a population based cross-sectional survey designed to be representative of the Canadian population – was carried out between 2009 and 2011. Of the 84 VOCs measured, 47 were detectable in at least 50% of homes and ten were negatively associated with lung function: decanal, 2-furancarboxaldehyde, hexanal, nonanal, octanal, benzene, styrene, α-pinene, 2-methyl-1,2-butadiene and naphthalene. Differences were observed between males and females, as well as by age, and significant associations were most frequent in those under 17 years. These results provide evidence that some VOCs measured indoors are negatively associated with lung function in the Canadian population.
اظهر المزيد [+] اقل [-]Impact of urbanization level on urban air quality: A case of fine particles (PM2.5) in Chinese cities النص الكامل
2014
Han, Lijian | Zhou, Weiqi | Li, Weifeng | Li, Li
We examined and compared PM2.5 concentrations in urban and the surrounding regions, and further investigated the impact of urbanization on urban PM2.5 concentrations at the Chinese prefectures. Annual PM2.5 concentrations in most prefectures were greater than 10 μg/m3, the air quality guideline of the World Health Organization. Those prefectures were mainly distributed along the east coast and southeast of Sichuan province; The urban PM2.5 concentrations (UrbanPM2.5) in 85 cities were greater than (>10 μg/m3) those in the surrounding area. Those cities were mainly located in the Beijing–Sichuan and Shanghai–Guangxi belts. In addition, UrbanPM2.5 was less than (<0 μg/m3) that in surrounding areas in only 41 prefectures, which were located in western China or nearby mega cities; Significant positive correlations were found between UrbanPM2.5 and urban population (R2 = 0.99, P < 0.05), and between UrbanPM2.5 and urban second industry fraction (R2 = 0.71, P < 0.05), suggesting that urbanization had considerable impact on PM2.5 concentrations.
اظهر المزيد [+] اقل [-]Assessment of floating plastic debris in surface water along the Seine River النص الكامل
2014
Gasperi, Johnny | Dris, Rachid | Bonin, Tiffany | Rocher, Vincent | Tassin, Bruno
This study is intended to examine the quality and quantity of floating plastic debris in the River Seine through use of an extensive regional network of floating debris-retention booms; it is one of the first attempts to provide reliable information on such debris at a large regional scale. Plastic debris represented between 0.8% and 5.1% of total debris collected by weight. A significant proportion consisted of food wrappers/containers and plastic cutlery, probably originating from voluntary or involuntary dumping, urban discharges and surface runoff. Most plastic items are made of polypropylene, polyethylene and, to a lesser extent, polyethylene terephthalate. By extrapolation, some 27 tons of floating plastic debris are intercepted annually by this network; corresponding to 2.3 g per Parisian inhabitant per year. Such data could serve to provide a first evaluation of floating plastic inputs conveyed by rivers.
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