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1.
PM Ross RM Fairweather DP Culliford S Park CA Pilditch CN Battershill 《新西兰海洋与淡水研究杂志》2016,50(1):56-69
ABSTRACTTo investigate the uptake and depuration of polycyclic aromatic hydrocarbons associated with the Rena oil spill we sampled the surf clam Paphies subtriangulata at two open coast locations (6?km apart) just prior to oil coming ashore (7 October 2011), then at 1–3 week intervals for the next 4 months. Total polycyclic aromatic hydrocarbons (tPAH) increased at both sites from 1 to 96–124?µg?kg?1 (wet weight) by 18 October before declining to low levels (<4?µg?kg?1) by February 2012. Ongoing sampling throughout 2012–2014 included three additional sites to the north east (up to 30?km away) and a site 5?km to the south east revealing tPAH levels generally <10?µg?kg?1 except in October 2013 where levels ranged between 39–45?µg?kg?1 at all sites. A comparison of PAH component profiles with oil-contaminated beach sediment indicated that the high levels observed in surf clams between October–December 2011 were clearly associated with the Rena spill. However, the October 2013 peak had a PAH profile inconsistent with weathered Rena oil, suggesting an alternative source of contamination. Our results highlight the potential for P. subtriangulata as a PAH monitoring tool but recognise more study is needed to better quantify baseline levels and uptake and depuration dynamics. 相似文献
2.
The organic composition and organic‐inorganic interaction in paper mill sludge (PS) solvent extracts (hexane, ethyl acetate, acetone and ethanol) and humic fractions, humic acid (HA) and humin (HU) were studied by electron paramagnetic resonance spectroscopy (EPR), proton and carbon‐13 nuclear magnetic resonance spectroscopy (1H NMR; 13C NMR), Fourier‐transformed infrared spectroscopy (FTIR), and ultraviolet‐visible spectroscopy (UV‐vis). The strategy of fractionating the PS, sequentially, with organic solvents of increasing polarity is a reliable analytical procedure for humic substance sample separation because it results in more purified fractions. FTIR, 1H NMR and 13C NMR results showed that hexane extract consisted mainly of aliphatic hydrocarbon structures. Their contents in the extracts decreased as the polarity of the extracting solvent increased and the content of oxygen functional groups increased. Carboxylic and carboxylate functional groups were found in the acetone extract, and ester and ether functions were predominantly found in the ethanol extract. EPR spectra revealed some Fe3+ complexes with rhombic structure (g1 = 4.3; g2 = 9.0) in the humic fractions and in all solvent extracts, except hexane. Quasi‐octahedral Fe3+ complexes (g = 2.3; ΔHpp ≤ 400 G) were found in the HU fraction and in the acetone extract. The organic free radical content in the HA fraction was higher than the non‐fractionated PS sample and HU fraction. 相似文献
3.
Maria Giovanna Durante Luigi Di Sarno George Mylonakis Colin A. Taylor Armando Lucio Simonelli 《地震工程与结构动力学》2016,45(7):1041-1061
An effective way to study the complex seismic soil‐structure interaction phenomena is to investigate the response of physical scaled models in 1‐g or n‐g laboratory devices. The outcomes of an extensive experimental campaign carried out on scaled models by means of the shaking table of the Bristol Laboratory for Advanced Dynamics Engineering, University of Bristol, UK, are discussed in the present paper. The experimental model comprises an oscillator connected to a single or a group of piles embedded in a bi‐layer deposit. Different pile head conditions, that is free head and fixed head, several dynamic properties of the structure, including different masses at the top of the single degree of freedom system, excited by various input motions, e.g. white noise, sinedwells and natural earthquake strong motions recorded in Italy, have been tested. In the present work, the modal dynamic response of the soil–pile–structure system is assessed in terms of period elongation and system damping ratio. Furthermore, the effects of oscillator mass and pile head conditions on soil–pile response have been highlighted, when the harmonic input motions are considered. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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M. Maugeri A. L. Simonelli A. Ferraro S. Grasso A. Penna 《Bulletin of Earthquake Engineering》2011,9(1):157-179
On April 6, 2009 a ML = 5.8 earthquake hit the city of L’Aquila on the Apennine chain in central Italy. Notwithstanding the moderate-size event
the L’Aquila city and several small villages along the Aterno river valley suffered severe damage, because of the unusual
strong motions, mainly due to proximity to the fault (estimated hypocentral depth of about 10 km). In this paper the main
features of the recorded motion are discussed. Four accelerometric stations were located within the surface projection of
the fault and recorded peak values ranging from 0.4 to 0.6 g. The recorded motions were characterised by short durations and
high peak accelerations both in the horizontal and vertical directions. The strong portions of vertical and horizontal motions
occurred almost simultaneously due to the short travel paths of P and S waves from the fault to the ground surface near the
fault area. Hence site response analyses were performed for the sites where recording stations were located. The geotechnical
subsoil model was derived by boreholes, in situ dynamic tests (D-H and SDMT) and by laboratory tests (RCT). One-dimensional
numerical analyses were carried out employing the well known computer code EERA. The numerical model was calibrated, in the
linear equivalent range, by comparing numerical results with the horizontal acceleration recorded components. 相似文献
6.
Stefania Sica Angelo Dello Russo Federica Rotili Armando Lucio Simonelli 《Natural Hazards》2014,71(3):1913-1935
Subsurface cavities or stiff inclusions represent mechanical discontinuities for seismic waves propagating in soils. They modify the propagation pattern of seismic waves and alter soil response in correspondence to the ground level or building foundations. In the literature, different analytical and numerical solutions have been proposed to account for the effect of underground cavities or inclusions on the motion generated by P, S or R waves. In these former studies, the subsoil was assimilated to a homogeneous, isotropic and linear elastic halfspace containing one or more cavities. In the present study, the effect of subsurface cavities on ground motion amplification has been analysed accounting for soil stiffness degradation and associated damping increase with increasing levels of shear strains, a fundamental aspect of soil behaviour under earthquakes. The analysed model was inspired to a real case represented by the village of Castelnuovo (Italy), which during the 2009 Abruzzo earthquake suffered huge damage. The main shock (6 April 2009) caused the collapse of 50 % of the whole built environment. The historical centre of Castelnuovo rises on a hill. In its subsoil, there are many cavities with roofs 2–3 m below the ground level. The longitudinal NW–SE section of the hill has been investigated by 2D nonlinear site response analyses. A preliminary site response analysis was performed without modelling cavities, to identify ground motion amplification due to mere stratigraphic and topographic factors. The numerical model was later refined inserting: (1) a single cavity below the hilltop, (2) multiple cavities placed below the ground surface of the hill and (3) multiple cavities filled with concrete (inclusions). The performed study highlights the important role exerted by underground cavities on the ground motion computed at the hill surface. This effect should be properly considered for both microzonation studies and the correct determination of the seismic actions on specific buildings. 相似文献
7.
Both foreign and domestic pelagic longline fishing vessels operate in South Africa’s Exclusive Economic Zone and adjacent international waters where they kill hundreds of seabirds each year as bycatch. To update assessments of the impact of the pelagic longline fishery on seabirds off South Africa, information on necropsied seabirds and national fisheries observer bycatch records were summarised for 2006–2013. Foreign-flagged (Asian) vessels had 100% observer coverage throughout the study period, whereas only 6% of the fishing effort by South African-flagged vessels was observed (with no coverage in 2011–2013). Vessels with observers caught seabirds at a rate of 0.132 birds per 1 000 hooks, resulting in an estimated mortality of 2 851 individuals (356 per year) comprising 14 species. Extrapolation of the observed fishing sets to the unobserved fishing sets by the South African domestic longline fleet suggested that approximately 750 additional birds were likely killed during the study period, therefore a combined 450 birds were killed per year. White-chinned petrel Procellaria aequinoctialis was the most frequently killed species (66%), followed by ‘shy-type’ albatrosses Thalassarche cauta/steadi (21%), black-browed albatross T. melanophris (7%), Indian yellow-nosed albatross T. carteri (3%), and Cape gannet Morus capensis (2%). The seabird bycatch rates were lower than in 1998–2005. Nationality of the vessel, time of line-setting, moon phase, year, season, fishing area, and seabird bycatch mitigation measures all influenced seabird mortality. Concurrent with 100% observer coverage, significant reductions in the seabird bycatch rate occurred in the Asian fleet in the latter years of the study, and these rates now approximate the national target (0.05 birds per 1 000 hooks). However, seabird bycatch rates remained high in the South African fleet, where no observers were deployed during 2011–2013, highlighting the need for independent observer programmes in fisheries—a matter of global interest. Suggestions are made as to how seabird bycatch by pelagic longline fisheries off South Africa may be further reduced. 相似文献
8.
B.J. Buratti C. Sotin M.D. Hicks J.A. Mosher R. Jaumann P.D. Nicholson D.P. Simonelli 《Planetary and Space Science》2006,54(15):1498-1509
Cassini observations of the surface of Titan offer unprecedented views of its surface through atmospheric windows in the 1-5 μm region. Images obtained in windows for which the haze opacity is low can be used to derive quantitative photometric parameters such as albedo and albedo distribution, and physical properties such as roughness and particle characteristics. Images from the early Titan flybys, particularly T0, Ta, and T5 have been analyzed to create albedo maps in the 2.01 and 2.73 μm windows. We find the average normal reflectance at these two wavelengths to be 0.15±0.02 and 0.035±0.003, respectively. Titan's surface is bifurcated into two albedo regimes, particularly at 2.01 μm. Analysis of these two regimes to understand the physical character of the surface was accomplished with a macroscopic roughness model. We find that the two types of surface have substantially different roughness, with the low-albedo surface exhibiting mean slope angles of ∼18°, and the high-albedo terrain having a much more substantial roughness with a mean slope angle of ∼34°. A single-scattering phase function approximated by a one-term Henyey-Greenstein equation was also fit to each unit. Titan's surface is back-scattering (g∼0.3-0.4), and does not exhibit substantially different backscattering behavior between the two terrains. Our results suggest that two distinct geophysical domains exist on Titan: a bright region cut by deep drainage channels and a relatively smooth surface. The two terrains are covered by a film or a coating of particles perhaps precipitated from the satellite's haze layer and transported by eolian processes. Our results are preliminary: more accurate values for the surface albedo and physical parameters will be derived as more data is gathered by the Cassini spacecraft and as a more complete radiative transfer model is developed from both Cassini orbiter and Huygens Lander measurements. 相似文献
9.
Stefania Sica George Mylonakis Armando Lucio Simonelli 《Soil Dynamics and Earthquake Engineering》2011
The dynamic response of piles to seismic loading is explored by means of an extensive parametric study based on a properly calibrated Beam-on-Dynamic-Winkler-Foundation (BDWF) model. The investigated problem consists of a single vertical cylindrical pile, modelled as an Euler–Bernoulli beam, embedded in a subsoil consisting of two homogeneous viscoelastic layers of sharply different stiffness resting on a rigid stratum. The system is subjected to vertically propagating seismic S waves, in the form of a transient motion imposed on rock outcrop. Several accelerograms recorded in Italy are employed as input motions in the numerical analyses. The paper highlights the severity of kinematic pile bending in the vicinity of the interface separating the two soil layers. In addition to factors already investigated such as layer stiffness contrast, relative soil–pile stiffness, interface depth and intensity of ground excitation, the paper focuses on additional important factors, notably soil material damping, stiffness of Winkler springs and frequency content of earthquake excitation. Existing predictive equations for assessing kinematic pile bending at soil layer interfaces are revisited and new regression analyses are performed. A synthesis of findings in terms of a set of simple equations is provided. The use of these equations is discussed through examples. 相似文献
10.
Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations
As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions. 相似文献