排序方式： 共有67条查询结果，搜索用时 15 毫秒
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Long-term monitoring of fish farms: application of Nematode/Copepod index to oligotrophic conditions
Riera R Sanchez-Jerez P Rodríguez M Monterroso O Ramos E 《Marine pollution bulletin》2012,64(4):844-850
Interannual variability (2003-2008) of meiofaunal assemblages were analyzed in sediments beneath fish cages (Impact group) and in areas not affected by aquaculture activities (Control group). Organisms responded with spatial and seasonal variation in meiofauna assemblages, with an abrupt increase of abundances in locations beneath fish cages throughout the study period. This increase was greater during the last sampling year (2008) and mainly due to high abundances of nematodes. Univariate analyses showed differences between control and impacted sites at both sites, however, only significant variations were found in Los Gigantes, which are consistent with seasonal meiofauna variations throughout the study period. These results are partially explained by differences in current velocity between both sampling areas. The Ne/Co index showed the same trend and it seems to be a reliable index in sediment slightly affected by aquaculture wastes. This index is especially recommended in oligotrophic areas (e.g. Canary Islands) where meiofaunal assemblages are poorly represented in terms of abundances. 相似文献
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Xin Wei Myriam Duc Mahdia Hattab Thierry Reuschlé Said Taibi Jean-Marie Fleureau 《Acta Geotechnica》2017,12(1):47-65
The goal in this research was to analyze the effects of decompression and suction on the formation of cracks in a clay rock from the Andra (French National Radioactive Waste Management Agency) site at Bure (Meuse–Haute-Marne, France). The article investigates the relationship between the changes in the hydromechanical properties and the changes in microstructure and porosity. Concerning the effect of decompression, at the macroscopic scale, the study highlighted an important effect on the elastic modulus and permeability, but little effect at the microscopic scale except an evolution of mineralogy related to the oxidation of pyrite often present in layers where cracks develop. Concerning the effect of suction, at the macroscopic level, the results showed that, on drying path, the change in the properties of the material was very small, whereas, on wetting path, a large decrease in tensile strength and gas permeability was observed. At the microscopic level, observations with SEM and ESEM, and measurements with MIP, highlighted the evolution of microstructural organization as a function of suction, and the propagation and enlargement of cracks on wetting path, rather than on drying path. 相似文献
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Myriam Andrea Rada Torres Vincenzo Costanzo-Álvarez Milagrosa Aldana Nery Suárez Corina Campos Maria Magdalena Mackowiak-Antczak María Carmela Brandt 《Studia Geophysica et Geodaetica》2011,55(4):717-736
Rock magnetic, petrographic and dielectric analyses were carried out, in a number of archeological ceramic potsherds, in order
to characterize the different manufacturing techniques used by Prehistoric Venezuelan Amerindian potters. Samples were excavated
in 7 Venezuelan islands and ascribed to distinct cultural groups on purely stylistic grounds (i.e. Valencioide, Ocumaroide,
Dabajuroide and Unknown). Mean coercivity values were determined through a direct signal analyses (DSA) applied to isothermal
remanent magnetization (IRM) acquisition curves. Logarithmic plots of these mean coercivities are the best quantitative means
to classify diverse ceramics. The mean coercivity values seem to group the samples according to the manufacturing development.
These values also seem to discriminate the samples provenance, indeed, this plot displays a good grouping of data for samples
presumably manufactured by the same culture but excavated at different locations. Thermomagnetic cycles supply helpful information
about original ceramic firing conditions. The irreversibility parameter (IP) for thermomagnetic curves (heating and cooling),
serves as an indicator of the amount of organic matter burnt during original pottery firing. The IP for a number of pottery
samples from Venezuelan islands and mainland, with ages ranging between 300 BC to 1500 AD, might suggest a possible increasing
trend in time towards the complete reversibility line of IP = 0. Most samples, independently of age and cultural group, have
IP values that suggest that most open fires, used by primitive Venezuelan Amerindian potters, had enough ventilation and oxidizing
atmospheres. A scatter plot of maximum current depolarization temperatures versus natural remanent magnetization (NRM) suggests
a complex non-linear relationship between these two parameters most likely due to the fact that both, dielectric and rock
magnetic data, are linked to pore-related features. 相似文献
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Wainer Ilana Prado Luciana F. Khodri Myriam Otto-Bliesner Bette 《Climate Dynamics》2021,56(1-2):109-122
Climate Dynamics - The South Atlantic subtropical dipole (SASD) has an impact on South American rainfall particular during its negative phase when continental precipitation in the northern part of... 相似文献
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The purpose of the present study is to ascertain the extent of the effect that phosphate fertilizer industrial waste has on the surface and bottom sediments of the Ghannouch-Gabes coast, off the Tunisian Mediterranean Sea. To achieve this, 44 surface sediments and 3 core sediments were studied for mineralogy, trace metals (Cd, Cu, Pb, and Zn), F, CaO, and SO3. For all the analyzed elements, the spatial distribution in surface sediments showed that the area located between the commercial and the fishing port of Gabes is the most polluted zone. The ranking of metal contents was found to be Zn > Cd > Cu > Pb. The vertical distribution of trace metals indicated that the highest levels were found in the uppermost segment of the sediment cores compared to the lower depth subsurface due to a continuous input of phosphogypsum (PG) release and confirmed that the area between the two harbors suffered from several types of pollutants compared to reference core C1, collected from other non-industrialized areas. This spatial and vertical distribution is probably due to the harbor piers which acted as barriers and limited the dispersion of PG discharge. The contamination factor, the geoaccumulation index, and the pollution load index were determined. The results obtained confirm the anthropogenic impact on the levels of metal, on the fluorine, calcium, and sulfate concentrations in the area, located between the commercial harbor of Ghannouch and the fishing harbor of Gabes, whereas the concentrations of elements analyzed tends to decrease on both sides of this sector. Statistical analyses (principal component analysis) showed trace metals, fluoride, sulfate, and a large amount of calcium resulting from the same anthropogenic source. 相似文献
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Kougkoulos Ioannis Merad Myriam Cook Simon J. Andredakis Ioannis 《Natural Hazards》2021,109(2):1959-1980
France experiences catastrophic floods on a yearly basis, with significant societal impacts. In this study, we use multiple sources (insurance datasets, scientific articles, satellite data, and grey literature) to (1) analyze modern flood disasters in the PACA Region; (2) discuss the efficiency of French public policy instruments; (3) perform a SWOT analysis of French flood risk governance (FRG); and (4) suggest improvements to the FRG framework. Despite persistent government efforts, the impacts of flood events in the region have not lessened over time. Identical losses in the same locations are observed after repeated catastrophic events. Relative exposure to flooding has increased in France, apparently due to intense urbanization of flood-prone land. We suggest that the French FRG could benefit from the following improvements: (1) regular updates of risk prevention plans and tools; (2) the adoption of a build back better logic; (3) taking undeclared damages into account in flood risk models; (4) better communication between the actors at the different steps of each cycle (preparation, control, organization, etc.); (5) better communication between those responsible for risk prevention, emergency management, and disaster recovery; (6) an approach that extends the risk analysis outside the borders of the drainage basin; and (7) increased participation in FRG from local populations.
相似文献59.
Ying Zi Cui Yu-Jun Duc Myriam Benahmed Nadia Bessaies-Bey Hela Chen Bo 《Acta Geotechnica》2021,16(4):1101-1111
Acta Geotechnica - Previous studies stated that, with increasing salinity, the decreased liquid limit for expansive soils was attributed to the shrinkage of diffuse double layer, while the... 相似文献
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