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71.
Experiments were carried out on the toxicity of a fuel oil to developing embryos and juveniles of two marine amphipods. Parhyale hawaiensis eggs were able to develop from early germinal disc stage (early eggs) to juvenile form in concentrations of 10 (2 ppm) up to 40% (8 ppm) WSF, but deleterious effects were evident in hatching success of eggs and survival of juveniles at concentrations ≥ 10% WSF. The juveniles that hatched from those eggs in higher WSFs had greater mortality than the juveniles that hatched from the eggs exposed to lower WSFs. Survival of juveniles from late eggs (cephalic region differentiated) was also greater than those from early eggs. Amphithoe valida eggs were more sensitive to the WSF of fuel oil than the eggs of P. hawaiensis; < 10% of the test eggs hatched in the 4 ppm WSF compared with 66% of P. hawaiensis eggs at the same concentration. The toxicity of fuel oil to the two amphipod eggs is therefore dependent on the concentration and duration of exposure on the one hand, and on the developmental stages and probably the nature of the egg case on the other. 相似文献
72.
Silvana Arreghini Laura de Cabo Rafael Seoane Nicolás Tomazin Roberto Serafini Alicia Fabrizio de Iorio 《GeoJournal》2007,70(4):281-288
The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at identifying the dynamics of
water quality in an area with low or “background” concentrations of pollutants within the Reconquista River system in order
to better define levels of pollution in the main system. In order to describe the dynamics of water quality in the background
area, we propose a methodology based on flow estimation with the instantaneous unit hydrograph model and on measurements of
physical and chemical water variables under different hydrological conditions. Because of high dissolved oxygen and low ammonium
and o-phosphate concentrations, the Arroyo Durazno, a tributary stream of the Reconquista River, is defined as a background area. When a storm event begins, the concentration
of nitrates and the electrical conductivity diminish. An increase in dissolved organic carbon suggests an important input
of carbon from hillslope runoff. The proportion of fulvic and humic acids also increases. On the receding limb of the hydrograph,
nitrate concentration was lower than during maximum flow and organic carbon concentration remained high. This behavior, known
as the “flushing effect”, suggests that the soluble material accumulated in the drainage area during dry periods is transported
to the stream by leaching or “lixiviation” and surface runoff, thus raising solute concentrations during the first few hours
of the storm. Water quality changes rapidly, even in background areas, due to its dependence on the flow. The methodology
followed in this paper can also be applied to other basins with similar characteristics. Due to the difficulty in defining
baseline areas for surface waters, a knowledge of background water quality and its dynamics is essential for understanding
pollution trends and anthropogenic impacts on rivers. 相似文献
73.
Bruce A. Firth Andrew R. Swanson Stuart K. Nicol 《International Journal of Mineral Processing》1979,5(4):321-334
A number of flotation circuits for the recovery of a poorly floating coal were investigated by laboratory batch testing. Analysis of the size and ash distributions of the products and tailings showed that the circuits which would allow an equitable distribution of collector between the coarse and fine size fractions were superior. These circuits were two-stage reagent addition, reflotation of classified tailings and split feed flotation. The reflotation of classified tailings circuit not only gave the best metallurgical performance, it also was the least affected by pulp density variations and imperfect size classification. 相似文献
74.
We reconstructed a chronology of glaciation spanning from the Late Pleistocene through the late Holocene for Fish Lake valley in the north‐eastern Alaska Range using 10Be surface exposure dating and lichenometry. After it attained its maximum late Wisconsin extent, the Fish Lake valley glacier began to retreat ca. 16.5 ka, and then experienced a readvance or standstill at 11.6 ± 0.3 ka. Evidence of the earliest Holocene glacial activity in the valley is a moraine immediately in front of Little Ice Age (LIA) moraines and is dated to 3.3–3.0 ka. A subsequent advance culminated at ca. AD 610–900 and several LIA moraine crests date to AD 1290, 1640, 1860 and 1910. Our results indicate that 10Be dating from high‐elevation sites can be used to help constrain late Holocene glacial histories in Alaska, even when other dating techniques are unavailable. Close agreement between 10Be and lichenometric ages reveal that 10Be ages on late Holocene moraines may be as accurate as other dating methods. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
75.
J.P. Milesi S.F. Toteu Y. Deschamps J.L. Feybesse C. Lerouge A. Cocherie J. Penaye R. Tchameni G. Moloto-A-Kenguemba H.A.B. Kampunzu N. Nicol E. Duguey J.M. Leistel M. Saint-Martin F. Ralay C. Heinry V. Bouchot J.C. Doumnang Mbaigane V. Kanda Kula F. Chene J. Monthel P. Boutin J. Cailteux 《Journal of African Earth Sciences》2006,44(4-5):571
This paper is prepared within the frameworks of IGCP Project 470 and the associated BRGM scientific project “Africa 1999–2004” to accompany the 1:4,000,000 scale map “Geology and major ore deposits of Central Africa, presented at the 20th Colloquium of African Geology in Orleans in June 2004. It incorporates geological and metallogenic data from eight countries in Central Africa (Angola, Cameroon, Chad, Central African Republic, Congo Brazzaville, Democratic Republic of Congo (DRC), Equatorial Guinea and Zambia). The map is a harmonised and geo-referenced preliminary map, based on a GIS at 1:2,000,000 scale, and focusses on the spatial and temporal distribution of selected major deposits. 相似文献
76.
Nicolás Federico Guillén Antoine Patalano Carlos Marcelo García Juan Carlos Bertoni 《Natural Hazards》2017,87(1):383-394
The probability of the occurrence of urban flash floods has increased appreciably in recent years. Scientists have published various articles related to the estimation of the vulnerability of people and vehicles in urban areas resulting from flash floods. However, most published works are based on research performed using numerical models and laboratory experiments. This paper presents a novel approach that combines the implementation of image velocimetry technique (large-scale particle image velocimetry—LSPIV) using a flash flood video recorded by the public locally and the estimation of the vulnerability of people and vehicles to high water velocities in urban areas. A numerical one‐dimensional hydrodynamic model has also been used in this approach for water velocity characterization. The results presented in this paper correspond to a flash flood resulting on November 29, 2012, in the city of Asunción in Paraguay. During this flash flood, people and vehicles were observed being carried away because of high water velocities. Various sequences of the recorded flash flood video were characterized using LSPIV. The results obtained in this work validate the existing vulnerability criterion based on the effect of the flash flood and resulting high water velocities on people and vehicles. 相似文献
77.
Fonseca Diego Luiz Marroig Patrícia Cunha Carneiro Juliane Castro Gallo Marcos Nicolás Vinzón Susana Beatriz 《Ocean Dynamics》2019,69(1):51-57
Ocean Dynamics - At the nautical bottom approach, part of the fluid mud layers can be included in the available depth if they present favorable rheology. As it is difficult to perform in situ... 相似文献
78.
Journal of Geographical Systems - This paper contributes to the existing literature on the explanation of housing prices. First, our proposed methodology accounts for cross-sectional dependence,... 相似文献