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Результаты 201-210 из 1,956
Bioaccumulation of perfluoroalkyl carboxylates (PFCAs) and perfluoroalkane sulfonates (PFSAs) by earthworms (Eisenia fetida) in soil Полный текст
2013
Zhao, Shuyan | Zhu, Lingyan | Liu, Li | Liu, Zhengtao | Zhang, Yahui
Earthworms were exposed to artificially contaminated soils with ten perfluoroalkyl substances (PFASs). PFASs with longer perfluorinated carbon chain displayed higher uptake rate coefficients (ku), longer half-life (t1/2) and time to steady-state (tss) but lower elimination rate coefficients (ke) than the shorter ones. Similarly, perfluorosulfonates acids (PFSAs) displayed higher ku, longer t1/2 and tss but lower ke than perflurocarboxylic acids (PFCAs) with the same perfluorinated chain length. All the studied PFASs, including those with seven or less perfluorinated carbons, were bioaccumulated in the earthworms and the biota-to-soil accumulation factors (BSAFs) increased with perfluorinated carbon chain length and were greater for PFSAs than for PFCAs of equal perfluoroalkyl chain length. The BSAFs were found to be dependent on the concentrations of PFASs in soil and decreased as the level of PFASs in soil increased.
Показать больше [+] Меньше [-]Improving local air quality in cities: To tree or not to tree? Полный текст
2013
Vos, Peter E.J. | Maiheu, Bino | Vankerkom, Jean | Janssen, Stijn
Vegetation is often quoted as an effective measure to mitigate urban air quality problems. In this work we demonstrate by the use of computer models that the air quality effect of urban vegetation is more complex than implied by such general assumptions. By modelling a variety of real-life examples we show that roadside urban vegetation rather leads to increased pollutant concentrations than it improves the air quality, at least locally. This can be explained by the fact that trees and other types of vegetation reduce the ventilation that is responsible for diluting the traffic emitted pollutants. This aerodynamic effect is shown to be much stronger than the pollutant removal capacity of vegetation. Although the modelling results may be subject to a certain level of uncertainty, our results strongly indicate that the use of urban vegetation for alleviating a local air pollution hotspot is not expected to be a viable solution.
Показать больше [+] Меньше [-]Biogenic volatile organic compounds from the urban forest of the Metropolitan Region, Chile Полный текст
2013
Préndez, Margarita | Carvajal, Virginia | Corada, Karina | Morales, Johanna | Alarcón, Francis | Peralta, Hugo
Tropospheric ozone is a secondary pollutant whose primary sources are volatile organic compounds and nitrogen oxides. The national standard is exceeded on a third of summer days in some areas of the Chilean Metropolitan Region (MR). This study reports normalized springtime experimental emissions factors (EF) for biogenic volatile organic compounds from tree species corresponding to approximately 31% of urban trees in the MR. A Photochemical Ozone Creation Index (POCI) was calculated using Photochemical Ozone Creation Potential of quantified terpenes. Ten species, natives and exotics, were analysed using static enclosure technique. Terpene quantification was performed using GC-FID, thermal desorption, cryogenic concentration and automatic injection. Observed EF and POCI values for terpenes from exotic species were 78 times greater than native values; within the same family, exotic EF and POCI values were 28 and 26 times greater than natives. These results support reforestation with native species for improved urban pollution management.
Показать больше [+] Меньше [-]Stomata are less responsive to environmental stimuli in high background ozone in Dactylis glomerata and Ranunculus acris Полный текст
2013
Wagg, Serena | Mills, Gina | Hayes, Felicity | Wilkinson, Sally | Davies, William J.
Two mesotrophic grassland species, Ranunculus acris and Dactylis glomerata were exposed to a range of ozone treatments (16.2–89.5 ppb 24 h mean) and two watering regimes under naturally fluctuating photosynthetically active radiation (PAR), vapour pressure deficit (VPD) and temperature. Stomatal conductance was measured throughout the experiments, and the combined data set (>1000 measurements) was analysed for effects of low and high ozone on responses to environmental stimuli. We show that when D. glomerata and R. acris were grown in 72.6–89.5 ppb ozone the stomata consistently lose the ability to respond, or have reduced response, to naturally fluctuating environmental conditions in comparison to their response in low ozone. The maximum stomatal conductance (gmax) was also significantly higher in the high ozone treatment for D. glomerata. We discuss the hypotheses for the reduced sensitivity of stomatal closure to a changing environment and the associated implications for ozone flux modelling.
Показать больше [+] Меньше [-]Biomonitors of urban air pollution: Magnetic studies and SEM observations of corticolous foliose and microfoliose lichens and their suitability for magnetic monitoring Полный текст
2013
Chaparro, Marcos A.E. | Lavornia, Juan M. | Chaparro, Mauro A.E. | Sinito, Ana M.
This study explored the suitability of available lichen species as air pollution biomonitors and assessed their potential for magnetic monitoring in cities. Several lichens on tree bark were collected in urban and industrial sites from Tandil city, as well as control sites. The results showed that magnetite-like minerals were the main magnetic carriers in all sites and samples. However, the concentration varied between clean and polluted sites. In addition, magnetic-grain size-distribution showed clear differences between sites. Observations by scanning electron microscopy showed different particles in a variety of shapes and grain sizes; moreover, the presence of iron oxides and several toxic elements was detected by energy dispersive spectroscopy analysis. Although eleven lichen species were identified that appeared suitable for use as air-pollution monitors, three of them, Parmotrema pilosum, Punctelia hipoleucites and Dirinaria picta, occurred more frequently in the area, thus constituting appropriate species for future monitoring in the study area.
Показать больше [+] Меньше [-]Polybrominated diphenyl ethers affect the reproduction and development, and alter the sex ratio of zebrafish (Danio rerio) Полный текст
2013
Han, X.B. | Yuen, Karen W.Y. | Wu, Rudolf S.S.
Polybrominated diphenyl ethers (PBDEs) have been commonly used as flame retardants and now become ubiquitous in the global environment. Using zebrafish as a model, we tested the hypothesis that PBDEs may affect the reproduction and development of fish. Zebrafish were exposed to environmentally relevant concentrations of DE-71 (a congener of PBDE commonly found in the environment) throughout their whole life cycle, and the effects of DE-71 on gonadal development, gamete quality, fertilization success, hatching success, embryonic development and sex ratio were investigated. Despite gonadal development was enhanced, reductions in spawning, fertilization success, hatching success and larval survival rate were evident, while significant increases in malformation and percentage of male were also observed in the F1 generation. Our laboratory results suggest that PBDEs may pose a risk to reproductive success and alter the sex ratio of fish in environments highly contaminated with PBDEs.
Показать больше [+] Меньше [-]A method to analyze “source–sink” structure of non-point source pollution based on remote sensing technology Полный текст
2013
Jiang, Mengzhen | Chen, Haiying | Chen, Qinghui
With the purpose of providing scientific basis for environmental planning about non-point source pollution prevention and control, and improving the pollution regulating efficiency, this paper established the Grid Landscape Contrast Index based on Location-weighted Landscape Contrast Index according to the “source–sink” theory. The spatial distribution of non-point source pollution caused by Jiulongjiang Estuary could be worked out by utilizing high resolution remote sensing images. The results showed that, the area of “source” of nitrogen and phosphorus in Jiulongjiang Estuary was 534.42 km2 in 2008, and the “sink” was 172.06 km2. The “source” of non-point source pollution was distributed mainly over Xiamen island, most of Haicang, east of Jiaomei and river bank of Gangwei and Shima; and the “sink” was distributed over southwest of Xiamen island and west of Shima. Generally speaking, the intensity of “source” gets weaker along with the distance from the seas boundary increase, while “sink” gets stronger.
Показать больше [+] Меньше [-]Molecular biomarkers for sources of organic matter in lacustrine sediments in a subtropical lake in China Полный текст
2013
Wang, Yan-Hua | Yang, Hao | Chen, Xia | Zhang, Ji-Xiang | Ou, Jie | Xie, Biao | Huang, Chang-Chun
N-alkanes distributions and stable isotopic compositions (δ13C and δ15N) in the lacustrine sediments of Shijiu lake were measured to assess whether biological source information was recorded in the molecular biomarker. Results showed regular unimodal n-alkanes distribution in range of C16–C33 with strong predominance of odd-numbered n-alkanes, maximizing at C29. The δ15N for SON were uniformly low, ranging from −6.7‰ to 3.8‰ and C/N ratios ranged from 6.6 to 10.0, suggesting that most of organic matter was influenced by terrestrial characteristics of the watershed. The δ13C for C27 to C31n-alkanes and for SOC varied from −32.9‰ to −26.6‰ and −23.4‰ to −21.6‰, respectively, falling within the range of corresponding n-alkanes in leaves mainly from C3 land plants. The values of C/N, CPI, OEP, ACL and C27/C31 exhibit similar temporal changes with the primary production, showing enhanced eutrophication resulted from increased anthropogenic activities in Shijiu lake from 1852 to 2010.
Показать больше [+] Меньше [-]Simulated degradation of biochar and its potential environmental implications Полный текст
2013
Liu, Zhaoyun | Demisie, Walelign | Zhang, Mingkui
A simulated oxidation technique was used to examine the impacts of degradation on the surface properties of biochar and the potential implications of the changes in biochar properties were discussed. To simulate the short- and long-term environmental degradation, mild and harsh degradation were employed. Results showed that after mild degradation, the biochar samples showed significant reductions in surface area and pore volumes. After harsh degradation, the biochar samples revealed dramatic variations in their surface chemistry, surface area, pore volumes, morphology and adsorption properties. The results clearly indicate that changes of biochar surface properties were affected by biochar types and oxidative conditions. It is suggested that biochar surface properties are likely to be gradually altered during environmental exposure. This implies that these changes have potential effects for altering the physicochemical properties of biochar amended soils.
Показать больше [+] Меньше [-]Effects of ozone on stomatal responses to environmental parameters (blue light, red light, CO2 and vapour pressure deficit) in three Populus deltoides × Populus nigra genotypes Полный текст
2013
Dumont, Jenny | Spicher, Fabien | Montpied, Pierre | Dizengremel, Pierre | Jolivet, Yves | Le Thiec, Didier
Effects of ozone on stomatal responses to environmental parameters (blue light, red light, CO2 and vapour pressure deficit) in three Populus deltoides × Populus nigra genotypes Полный текст
2013
Dumont, Jenny | Spicher, Fabien | Montpied, Pierre | Dizengremel, Pierre | Jolivet, Yves | Le Thiec, Didier
The effect of ozone (O3) on stomatal regulation was studied in three Euramerican poplar genotypes (Populus deltoides × Populus nigra: Carpaccio, Cima and Robusta). The impact of O3 on stomatal conductance responses to variations in blue light, red light, CO2 concentration and vapour pressure deficit (VPD) was studied. Upon O3 exposure, a sluggish response of stomatal movements was observed, characterized by slower reactions to increases in blue light intensity, CO2 concentration and VPD, and lower amplitude of the response to variations in light intensity. That sluggish response should be taken into account in stomatal conductance models for phytotoxic ozone dose (PODY) calculations. The speed of the response to variations in environmental parameters appears as a determining factor of genotype-related sensitivity.
Показать больше [+] Меньше [-]Effects of ozone on stomatal responses to environmental parameters (blue light, red light, CO2 and vapour pressure deficit) in three Populus deltoides × Populus nigra genotypes Полный текст
2013
Dumont, Jennifer | Spicher, Fabien | Montpied, Pierre | Dizengremel, Pierre | Jolivet, Yves | Le Thiec, Didier
The effect of ozone (O3) on stomatal regulation was studied in three Euramerican poplar genotypes (Populus deltoides Populus nigra: Carpaccio, Cima and Robusta). The impact of O3 on stomatal conductance responses to variations in blue light, red light, CO2 concentration and vapour pressure deficit (VPD) was studied. Upon O3 exposure, a sluggish response of stomatal movements was observed, characterized by slower reactions to increases in blue light intensity, CO2 concentration and VPD, and lower amplitude of the response to variations in light intensity. That sluggish response should be taken into account in stomatal conductance models for phytotoxic ozone dose (PODY) calculations. The speed of the response to variations in environmental parameters appears as a determining factor of genotyperelated sensitivity.
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