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71.
Rosas Pérez I Serrano J Alfaro-Moreno E Baumgardner D García-Cuellar C Martín Del Campo JM Raga GB Castillejos M Colín RD Osornio Vargas AR 《Chemosphere》2007,67(6):1218-1228
Previous studies have used particle mass and size as metrics to link airborne particles with deleterious health effects. Recent evidence suggests that particle composition can play an important role in PM-toxicity; however, little is known about the specific participation of components (individually or acting in groups) present in such a complex mixture that accounts for toxicity. This work explores relationships among PM(10) components in order to identify their covariant structure and how they vary in three sites in Mexico City. Relationships between PM(10) with cell toxicity and geographical location were also explored. PM(10) was analyzed for elemental composition, organic and elemental carbon, endotoxins and the induction of inhibition of cell proliferation, IL-6, TNFalpha and p53. PM(10) variables were evaluated with principal component analysis and one-way ANOVA. The inhibition of cell proliferation, IL-6 and TNFalpha were evaluated with factorial ANOVA and p53 with the Welch test. The results indicate that there is heterogeneity in particle mass, composition and toxicity in samples collected at different sites. Multivariate analysis identified three major groups: (1) S/K/Ca/Ti/Mn/Fe/Zn/Pb; (2) Cl/Cr/Ni/Cu; and (3) endotoxins, organic and elemental carbon. Groups 1 and 3 showed significant differences among sites. Factorial ANOVA modeling indicated that cell proliferation was affected by PM concentration; TNFalpha and IL-6 by the interaction of concentration and site, and p53 was different by site. Radial plots suggest the existence of complex interactions between components, resulting in characteristic patterns of toxicity by site. We conclude that interactions of PM(10) components determine specific cellular outcomes. 相似文献
72.
Stable isotopes of carbon and nitrogen (delta(13)C and delta(15)N) have been determined in wild and farmed gilthead sea bream (Sparus aurata) samples of white and red muscle, liver, gills and gonads. First, delta(13)C and delta(15)N values were determined in samples with and without lipid removal to check the possible effect of lipid content on the stable isotope values of the different tissues studied. Differences were found for delta(13)C in all tissues studied apart from white muscle of wild fish, the tissue with the lowest lipid content. For delta(15)N values no differences were found in wild fish tissues. Liver from farmed fish showed lower delta(15)N value after lipid removing. Further conclusions were based on results obtained from lipid-free samples. delta(13)C of cultured fish tissues showed a mean depletion of 2.9+/-0.4 per thousand compared to wild specimens, suggesting different sources of carbon in the diet, probably due to the feed used during sea-cage culture. Cultured gilthead sea bream tissues were significantly more enriched in nitrogen than wild specimens by an average of 1.5+/-0.2 per thousand in white muscle, indicating a slight increase in the trophic level. Determination of stable isotope signatures of gilthead sea bream tissues allows clear discrimination between wild and cultured sea bream, and characterisation of differences in diet and feeding conditions in any tissue studied. 相似文献
73.
The possibility of transforming waste plastics into valuable hydrocarbons via catalytic cracking and reforming is attracting
increasing interest. Pyrolysis coupled with Gas Chromatographic separation and Mass Spectrometry detection (Py-GC/MS) has
been used in this work to study the product selectivity of various catalysts in the conversion of pure and residual polyethylene
samples into hydrocarbon products. Five acid solids of comparable aluminium contents but different textural and acid properties
were tested as catalysts, including three zeolites (standard ZSM-5, nanocrystalline n-ZSM-5 and Beta) and two mesostructured
solids (Al-MCM-41 and Al-SBA-15). Thermal cracking of the pure and residual polymers generated a similar range of products
to each other, with a high proportion of linear paraffins and olefins of varying lengths. The presence of zeolitic materials
resulted in complete elimination of heavy linear products, an increase in the light hydrocarbon fraction and a marked selectivity
towards the formation of single-ring aromatic species, particularly benzene, toluene and xylene. Aromatic formation was particularly
notable with the small crystal size n-ZSM-5 (aromatic selectivity up to 53.9%) and less marked in the case of standard ZSM-5
(up to 36.4%) and Beta zeolite (up to 35.0%). Mesostructured catalysts like Al-MCM-41 and Al-SBA-15 favoured the production
of light C2–C5 hydrocarbons (up to 57.9%) while the formation of aromatic products was significantly lower than with zeolitic materials.
The paper examines the extent and the causes for this product selectivity and discusses its connection with the acid and textural
properties of each catalyst. It was also observed that, under the experimental conditions employed, the products generated
were not significantly affected by the nature and origin of the polymers employed. 相似文献
74.
J. Aguado D. P. Serrano G. Vicente N. Sánchez 《Journal of Polymers and the Environment》2006,14(4):375-384
The thermal cracking of HDPE in presence of different amounts of decalin was studied and compared with the reaction carried out in the absence of solvent. The decalin favours the mass and heat transfer during the reaction. In addition, it modifies the thermal degradation mechanism, which facilitates the formation of specific products. The use of decalin substantially increases the C5–C32 yield in comparison with the solventless reaction. In all cases, linear hydrocarbons such as n-paraffins, α-olefins and α,ω-dienes were detected. Increasing the decalin/plastic ratio led to enhanced α-olefin and n-paraffins yields, but the increase was more significant in the case of α-olefins, which are valuable compounds useful as raw chemicals. A reaction mechanism was proposed to explain the results obtained in presence of decalin. In these reactions, intramolecular radical transfer, secondary radical β-scission and hydrogen transfer from both decalin to intermediate radicals and from the polymer chain to regenerate the decalin play a significant role in determining the plastic conversion and the relative amounts of each product. 相似文献
75.
Marine water pollution affects many recreational sites around the world. It has impacts not only on recreational activities but also on health risks for those who come into direct contact with the water. Few economic studies have explicitly considered the health risks of bathing in polluted marine waters and none have attempted to separate health benefits from other benefits of marine water quality improvements. This paper uses stated preference techniques to separately evaluate the multiple benefits of improving the quality of marine recreational waters at the Estoril Coast in Portugal. The results indicate that health risk reductions are only a small fraction of the total social benefits of water quality improvements. 相似文献
76.
Matthew D. Shawkey Branislav Igic Svana Rogalla Jonathan Goldenberg Susana Clusella-Trullas Liliana D’Alba 《Die Naturwissenschaften》2017,104(9-10):78
The visible spectrum represents a fraction of the sun’s radiation, a large portion of which is within the near infrared (NIR). However, wavelengths outside of the visible spectrum that are reflected by coloured tissues have rarely been considered, despite their potential significance to thermal effects. Here, we report the reflectivity from 300 to 2100 nm of differently coloured feathers. We measured reflectivity across the UV-Vis-NIR spectra of different (a) body parts, (b) colour-producing mechanisms and (c) sexes for 252 individuals of 68 sunbird (family: Nectariniidae) species. Breast plumage was the most reflective and cap plumage the least. Female plumage had greater reflectivity than males. Carotenoid-based colours had the greatest reflectivity, followed by non-iridescent and iridescent melanin-based colours. As ordered arrays of melanin-filled organelles (melanosomes) produce iridescent colours, this suggests that nanostructuring may affect reflectance across the spectrum. Our results indicate that differently coloured feathers consistently vary in their thermal, as well as obvious visual, properties. 相似文献
77.
Joshua M. Allen Amy A. Cuthbertson Hannah K. Liberatore Susana Y. Kimur Anurag Manth Marc A. Edwards Susan D. Richardson 《环境科学学报(英文版)》2017,29(8):271-284
Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water (Lake Huron) with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal, reports of skin rashes have sparked questions surrounding tap water in some Flint homes. This study investigated the presence of contaminants, including disinfection by-products (DBPs), in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water. Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible. 相似文献
78.
In this paper we compute the genuine savings indicators for the Republic of Ireland over the period 1995-2005. We expand and improve existing World Bank's estimates by: a) using data collected from official Irish sources; b) employing the net present value method to assess resource depreciation; c) including external costs from SO(2) and NOx emissions; and d) estimating human capital accumulation using the returns to education. We also perform a sensitivity analysis to check the robustness of our estimates to different assumptions and parameters. Our estimates are consistently smaller than the World Bank's and negative in the first years of the period considered. 相似文献
79.
There is a consensus that Marine Protected Area (MPA) performance needs regular evaluation against clear criteria, incorporating
counterfactual comparisons of ecological and socio-economic performance. However, these evaluations are scarce at the global
level. We compiled self-reports from managers and researchers of 78 coral reef-based MPAs world-wide, on the conservation
and welfare improvements that their MPAs provide. We developed a suite of performance measures including fulfilment of design
and management criteria, achievement of aims, the cessation of banned or destructive activities, change in threats, and measurable
ecological and socio-economic changes in outcomes, which we evaluated with respect to the MPA’s age, geographical location
and main aims. The sample was found to be broadly representative of MPAs generally, and suggests that many MPAs do not achieve
certain fundamental aims including improvements in coral cover over time (in 25% of MPAs), and conflict reduction (in 25%).
However, the large majority demonstrated improvements in terms of slowing coral loss, reducing destructive uses and increasing
tourism and local employment, despite many being small, underfunded and facing multiple large scale threats beyond the control
of managers. However spatial comparisons suggest that in some regions MPAs are simply mirroring outside changes, with demonstrates
the importance of testing for additionality. MPA benefits do not appear to increase linearly over time. In combination with
other management efforts and regulations, especially those relating to large scale threat reduction and targeted fisheries
and conflict resolution instruments, MPAs are an important tool to achieve coral reef conservation globally. Given greater
resources and changes which incorporate best available science, such as larger MPAs and no-take areas, networks and reduced
user pressure, it is likely that performance could further be enhanced. Performance evaluation should test for the generation
of additional ecological and socio-economic improvements over time and compared to unmanaged areas as part of an adaptive
management regime. 相似文献
80.
Ruth Fernández Susana García-Tiscar M. Begoña Santos Alfredo López Jose A. Martínez-Cedeira Jason Newton Graham J. Pierce 《Marine Biology》2011,158(5):1043-1055
Skin and muscle from 43 bottlenose dolphins (38 juveniles/adults, 5 calves) stranded in NW Spain were analysed to determine
whether stable isotope ratios (δ13C and δ15N) could be used to assess dietary variation, habitat segregation and population substructure. Results were compared with
published stomach contents data. Stable isotope ratios from 17 known prey species were also determined. Isotope ratios of
the main prey (blue whiting, hake) varied significantly in relation to fish body size. Dolphin calves showed significant heavy
isotope enrichments compared to adult females. Excluding calves, δ15N decreased with increasing dolphin body size, probably related to an ontogenetic shift in diet towards species at lower trophic
levels, e.g. on blue whiting as suggested by stomach content results. Bottlenose dolphins were divided into two putative populations
(North, South) based on previous genetic studies, and values of δ13C and δ15N differed significantly between these two groups, confirming the existence of population structuring. 相似文献