Magnetic cleansing of weathered/tarry oiled feathers--the role of pre-conditioners

Iron powder has previously been demonstrated to be effective in the removal, via magnetic harvesting, of a wide variety of oil contaminants from feathers and plumage. This study investigates the efficacy of magnetic cleansing for the removal from feathers of tarry contamination that has been allowed to weather. Clusters of feathers from Mallard duck (Anas platyrhnchos) and Little Penguin (Eudyptula minor) were completely immersed in a tarry contaminant and allowed to weather from one to fourteen days. The contaminant was removed using a magnetic cleansing protocol and the removal efficacy assessed gravimetrically. For one, seven and fourteen days of weathering, a final removal (after fourteen treatments) of more than 99% and 97% was achieved for duck feathers and penguin feathers, respectively. Repeating the experiments (for a seven-day weathering period) for both duck and penguin feathers, with the judicious application of a pre-conditioner (olive oil), further improved removal efficacy. A convenient method to screen for improved pre-conditioning agents is suggested.     

The development of the SCAT process for the assessment of oiled shorelines

The Shoreline Cleanup Assessment Team (SCAT) process is a tool to assess oiled shorelines and is now an integral component of spill response operations. The key element of a SCAT survey is a systematic documentation using standard terms and definitions of the shoreline in the areas affected by an oil spill. SCAT programs were initially established to provide objective and accurate shoreline oiling information directly to cleanup operations. The role of the SCAT program has since expanded and the information generated by the field teams is used now by planners and decision-makers and to develop shoreline treatment recommendations, to select appropriate treatment techniques, and to establish the level or degree of treatment that is appropriate. This latter point is an integral part of establishing shoreline treatment criteria or standards and treatment end points.     

Physical basis for magnetic deep sounding models

The purpose of this note is to point out how recent advances in our understanding of mantle conductivity, especially in transition regions, can be applied to the construction of physically realistic models for use in magnetic deep sounding.     

地壳磁异常的全球模型

从全球磁场减去地核主磁场和变化磁场及其感应磁场后,就得到岩石圈磁场,又称地壳磁场,或地磁异常.地壳磁场是地磁场的重要组成部分,对导航、通信、地球物理勘探等有重要意义.本文简要综述近年来在地壳磁场基本信息获取方面取得的重大进展,特别是Oersted、CHAMP等卫星磁侧的最新成果,介绍在此基础上建立的全球磁异常模型,展望地壳磁场研究的发展趋势和应用前景.     

Gravimetric determination of water-repellancy in rehabilitated oiled seabirds

After removing oil, the aim of oiled seabird rescue operations is to restore the water-repellancy of the birds plumage. Non-waterproof penguins absorb more water onto the plumage than waterproof penguins, measured gravimetrically. We suggest that oiled seabird rescue stations use this difference to test for readiness for release of cleaned birds.     

Dynamo models with magnetic diffusivity-quenching

Abstract

The magnetic influence on a turbulent plasma also produces a complicated structure of the eddy diffusivity tensor rather than a simple and traditional quenching of the eddy diffusivity. Dynamo models in plane (galaxy) and spherical (star) geometries with differential relation are developed here to answer the question whether the dynamo mechanism is still yielding stable configurations. Magnetic saturation of the dynamos is always found—at magnetic energies exceeding the energy-equipartition value.

We find that the effect of magnetic back-reaction on the turbulent diffusivity depends highly on whether the dynamo is oscillatory or not. The steady modes are extremely influenced. They saturate at field strengths strongly exceeding its turbulence-equipartition value. Subcritical excitation is even found for strong seed fields. The oscillating dynamos, however, only provide a small effect. Hence, the strong over-equipartition of the internal solar magnetic fields revealed by studies of flux-tube dynamics cannot be explained with the theory presented. Also the run of the cycle frequency with the dynamo number is too smooth in order to explain observations of stellar chromospheric activity.     

Scale-to-scale stabilization of the magnetic field in the dynamo models

The three-dimensional dynamo model in the fast-rotating plane layer heated from below is considered. The transition from the linear generation of the magnetic field to the nonlinear generation is studied. With the use of the wavelet analysis, it is demonstrated how the spatial spectra of the kinetic and magnetic energies, as well as the hydrodynamic, magnetic, cross-, and current helicity, vary in time. The scenarios of the suppression of α-effect (α-quenching) by the magnetic field are suggested.     

菲律宾及其邻近地区的地磁场模型研究

根据2001~2007年期间在菲律宾境内测量的74个点的地磁场数据,利用球冠谐和、泰勒多项式两种方法建立了2005.0菲律宾及周边地区地磁基本场模型,得到了菲律宾地区X、Y、Z、D、I、H、F七个分量的分布.两种模型反映的同一地区的地磁场分布形态基本类似,只在拐点的舒缓度、等值线平滑度等方面存在区别.在8°N左右,X、H、F出现系统的拐点,同纬度的X、H、F东低西高.D、Y零线分布于8°N左右呈东西展布,北侧为负,南侧为正,等值线沿经度分布的同时,在纬度上有不同程度的小起伏.Z、I空间分布呈现更加规则均匀的东西向分布特征.零线分布在7.5°N左右,零线北部是正值区域,南部是负值区域.两种模型与IGRF的差值的分布形态有很大的不同,球冠谐模型与IGRF模型差值的正负异常区域呈现正负异常相间的分布特征,且各分量的正负异常最大值分布在低纬度地区.而泰勒多项式与IGRF差值的正负异常分布却相对完整.     

Birds oiled during the Amoco Cadiz incident—An interim report

Over 4500 oiled birds were collected from beaches in Northwest France and the Channel Islands following the oil spillage from the AMOCO CADIZ in March 1978. Auks were the most abundant casualties: 1391 puffins Fratercula arctica, 978 razorbills Alca torda and 731 guillemots Uria aalge, but there were also 126 divers Gavia spp. A total of 33 bird species were recorded oiled. A corpse drift experiment suggested that after 30 March at least 3450 seabirds died off north Finistère alone; the total mortality in the first fortnight of the incident was probably considerably larger.     

Temperature and the seasonal and geographical occurrence of oiled birds on west European beaches

Oiled birds appear to be a commoner aspect of oil pollution where it occurs with cold water-temperatures, whereas the formation of tar-balls becomes more prominent with warm ones, possibly because liquid oil becomes reduced to inert solid residues comparatively harmless to birds more rapidly at higher temperatures.     

磁层磁场模式的研究进展

磁场模式是表述空间磁场的一种有效工具,对于研究磁层大尺度电流系的发展变化和辐射带粒子具有重要意义.本文介绍了三种主要的磁层磁场模式,即经验模式、抛物面模式和事件导向模式,结合模式的原理和特点,对模式的改进情况和性能检验进行了详细论述,并对三种模式进行了对比分析.三种模式都能对暴时磁场进行动态模拟.最近的Tsyganenko模式考虑了太阳风的历史作用,每个磁场源都有自己的松弛时间尺度及驱动函数;抛物面模式A01中增加了场向电流及窄尾流效应;事件导向模式G03增加了非对称环电流和局地窄尾流片效应.     

Mercury levels in feathers of Magellanic penguins

Feathers are useful to determine mercury (Hg) contamination. We evaluated the mercury concentration in feathers of Magellanic penguins (Spheniscus magellanicus) age 1.5 years to 25 years at Punta Tombo, Argentina before and during their molt. Mercury ranged between <1.4 and 367 ng/g dry weight, with three extreme high values (8996 ng/g, 3011 ng/g and 1340 ng/g) all in young adults. The median concentration was lowest for juveniles and significantly higher for adults but with high variation among older adults. Males and females had similar mercury loads. Compared with other penguin species, concentrations in Magellanic penguins were low. Mercury levels for Magellanic penguins in the Southwest Atlantic for older adults averaged 206±98 ng/g, and serve as a baseline for biomonitoring and/or ecotoxicological studies.     

Time asymmetry of magnetic field variations in dynamo models

We considered two types of magnetic field time asymmetry related to the inverse influence of the magnetic field on the currents in the dynamo models and observations. The first type includes variations in which the total time that the time derivative is positive is different from the time that this derivative is negative. In a monochromatic wave, this corresponds to a failure of symmetry with respect to the point at which the wave has an extremum. The second class includes the time signals at which another failure of antisymmetry appears relative to the mean value of the signal. None of these types of symmetry can be recorded by the methods of the Fourier or wavelet analysis. We use the Parker’s dynamo model in a thin layer and a threedimensional model in a flat rotating layer when heated from below and present estimates of the failure of the symmetry data. It was shown that in the paleo-variations the model time of field increase is smaller than the time of its decrease.     

经验和抛物面模式模拟暴时磁场的误差特性研究

利用两种不同的磁场模式,协同GOES10/12、Polar及Geotail的实测资料,本文对3种不同强度磁暴的磁层磁场进行了详细分析,从而检验了两种不同磁场模式的可靠性,给出了模式间的性能对比.我们采用Tsyganenko经验模式及Alexeev抛物面模式,分别模拟了2004年4月、7月和11月的磁暴,3个磁暴过程中最强Dst指数分别达到-110 nT,-150 nT以及-289 nT.结果发现:T01模式对于中等磁暴时磁场模拟准确,而由于建立模式的数据库中强磁暴资料少,模式中不包含亚暴效应,T01对于强磁暴磁场模拟的误差增大,磁场分量远远偏离观测值;A2000模式缺少部分环电流及Ⅱ区场向电流,模式对于近地点Polar轨道上的磁场扰动模拟不足,对强磁暴时亚暴效应的过高模拟使其模拟的磁场分量偏高;T01模式对于中等磁暴时磁场的模拟效果明显好于A2000模式,随着磁层扰动的增强,T01与A2000模式的总体性能相当.     

Two pedogenic models for paleoclimatic records of magnetic susceptibility from Chinese and Siberian loess

The magnetic susceptibility (MS) of Chinese loess showing a general proportional relationship to pedogenic grade has been widely recognized and used for reconstruction of paleoclimate by Quaternary scientists. The in-situ pedogenic enhancement of ferrimagnetic content is normally believed to be the main reason for the increase of susceptibility in soil units. However, this pattern of high magnetic susceptibility in palaeosols, and low values in loess, are not replicated in some loess deposits. Siberian loess deposits display a completely opposite susceptibility behavior: high values in loess and low values in palaeosols. This inverse relationship has been explained by the idea that magnetic susceptibility is reflecting the magnitude of an aeolian ferrimagnetic component of consistent mineralogy, the grain size of which is related to average wind velocity. Our magnetic study of Siberian samples in this paper suggests that there are notable differences in magnetic properties between Siberian loess and developed palaeosols, not only in magnetic grain-size and concentration but also in magnetic mineralogy. This evidence is difficult to explain fully through variation in wind strength alone, but implies that the low magnetic susceptibility values in the Siberian paleosol units are a reflection, at least in part, of the alteration of the ferrimagnetic content by post-depositional processes. The Loess Plateau is a very arid area where potential evaporation is always higher than precipitation; pedogenesis occurs under dry oxidising conditions. The Siberian Kurtak region is located on the edge of the tundra where it is always wet and saturation during interglacials will lead to a reducing pedogenic environment. Ferrimagnetic minerals under this condition will be destroyed, resulting in lower magnetic susceptibility. Therefore, great care should be taken when using susceptibility values for paleoclimatic reconstruction.     

A regularized Wiener–Hopf filter for inverting models with magnetic susceptibility

For a magnetic target, the spatial magnetic signal can be expressed as a convolutional integral over Green's function of an assumed model with susceptibility as its parameter. A filter can be used to obtain the susceptibility by minimizing the mismatch between observed and the computed magnetic anomalies. In this perspective, we report the development of an advanced digital filter, which is efficient and can be used to map rock susceptibility from the acquired magnetic data. To design the new filter, we modified the space‐domain standard Wiener–Hopf filter by imposing two different constraints: (i) the filter energy constraint; and (ii) normalization of the filter coefficients. These constraints make it capable to characterize source bodies from their produced magnetic anomalies. We assume that the magnetic data are produced by induced magnetization only and interpretation can be as good as the subsurface model. Our technique is less sensitive to the data noise, which makes it efficient in enhancing the interpretation model. The modified filter demonstrates its applicability over the synthetic data with additive white Gaussian noise. In order to check the efficacy and adaptivity of this tool in a more realistic perspective, it is also tested on the real magnetic data acquired over a kimberlitic district adjoining to the western margin of the Cuddapah Basin in India to identify the source bodies from the anomalies. Our result shows that the modified Wiener–Hopf filter with the constraint for the magnetic data is more stable and efficient than the standard Wiener–Hopf filter.     

Density and magnetic models of the lithosphere along CELEBRATION 2000 profile CEL01

The paper presents 2D density and magnetic models of the crust and upper mantle along the DSS line profile of the CELEBRATION 2000 project that crosses the most important geological units in Central Europe. These are the Alps-Carpathians-Pannonian (ALCAPA) region, the SE part of the Paleozoic Platform (PLZ), the Trans-European Suture Zone (TESZ) and a fragment of the SW portion of the East European Craton (EEC). The density and magnetic models were constructed on the basis of a 2D model of P-wave velocity converted into density model, geological data as well as geothermal data and the results of integrated geophysical modelling for the lithosphere-asthenosphere boundary.