Modern influences on chironomid distribution in western Ireland: potential for palaeoenvironmental reconstruction     

Aaron P. Potito  Craig A. Woodward  Michelle McKeown  David W. Beilman 《Journal of Paleolimnology》2014,52(4):385-404

Ireland provides a unique setting for the study of past climates, as its climate is dominated by westerly airflow from the North Atlantic and readily responsive to changes in North Atlantic circulation patterns. Although there has been substantial research on Ireland’s past environments, quantitative palaeolimnological research, especially chironomid-based research, has been lacking. In order to further develop chironomid-based palaeolimnological investigations, a calibration set was constructed to determine the dominant environmental controls on modern chironomids in western Ireland. Chironomid subfossils were collected from surface sediments of 50 lakes. The lakes were characterised with 36 environmental variables, including physical attributes, lake water characteristics, lake sediment characteristics and land cover within each catchment. In this exploratory study, no specific environmental variable was targeted and lakes were chosen to span gradients of latitude, elevation, depth and trophic status. Redundancy analysis showed that six environmental variables—mean July air temperature, lake depth, dissolved organic carbon, and percentage catchment land cover of agriculture, peat bog and scrubland—captured a large and statistically significant portion of the variance in the chironomid data. July temperature and agricultural land cover were the most dominant environmental variables, with July temperature proving the most suitable for inference model development. A classical weighted-averaging model was developed to estimate July air temperature, with a coefficient of determination (r _jack ² ) of 0.60 and root mean square error of prediction (RMSEP) of 0.57 °C. Results suggest that summer temperature is the dominant influence on chironomid distribution across a wide variety of lake types, and the relatively small RMSEP should allow for more accurate reconstructions of Ireland’s relatively subdued Holocene temperature fluctuations.  相似文献   

Raman spectroscopy, vibrational analysis, and heating of buergerite tourmaline     

David A. McKeown 《Physics and Chemistry of Minerals》2008,35(5):259-270

Polarized Raman spectra were collected for single crystal buergerite (NaFe₃Al₆(BO₃)₃Si₆O₁₈(O_0.92(OH)_0.08)₃F) from room temperature to near 1,375°C. Vibrational assignments to features in the room temperature spectra were determined by lattice dynamics calculations, where internal BO₃ motions dominate modes near 1,300 cm⁻¹, internal SiO₄ displacements dominate modes between 900 and 1,200 cm⁻¹, while less localized displacements within the isolated Si₆O₁₈ ring mix with motions within Na, Fe, Al, F, and BO₃ environments for fundamental modes below 780 cm⁻¹. At elevated temperatures, most buergerite Raman features broaden and shift to lower frequencies up to 900°C. Above this temperature, the lattice mode peaks evolve into broad bands, while OH stretch modes near 3,550 cm⁻¹ disappear. According to Raman spectroscopy, X-ray diffraction, differential thermal analysis, and scanning electron microscopy, buergerite undergoes a complex transition that starts near 700°C and extends over a 310°C interval, where initially, Al and Fe probably become disordered within the Y- and Z-sites, and most F and all OH are later liberated. A reversible crystal-to-amorphous transition is seen by Raman for buergerite fragments heated as high as 930°C. Buergerite becomes permanently altered when heated to temperatures greater than 930°C; after cooling to room temperature, these altered fragments are comprised of mullite and Fe-oxide crystals suspended in an amorphous borosilicate matrix.  相似文献   

Long-term sublethal and short-term high dose effects of physically and chemically dispersed oil on accumulation and clearance from various tissues of juvenile coho salmon, Oncorhynchus kisutch     

B. A. McKeown 《Marine environmental research》1981,5(4):295-300

The toxicity of crude oil and the dispersant BP1100X was tested in sea water and in each case was much less than the toxicity to fish in fresh water. Uptake of oil from water, with or without dispersant, was similar after a short exposure to 200 ppm. The oil was cleared from the fish in three weeks. A long-term exposure to oil or oil plus dispersant at a concentration of 5 ppm showed a slow accumulation but significantly above exposure levels. Thus, salmon exposed to oil in sea water can take up the hydrocarbons but appear to cleanse themselves rapidly.  相似文献   

Ne  vii emission lines in the solar EUV spectrum     

McKeown  M.  Keenan  F.P.  Ramsbottom  C.A.  Bell  K.L.  Ryans  R.S.I.  Reid  R.H.G. 《Solar physics》1999,186(1-2):231-242

Recent calculations of electron and proton impact excitation rates in Nevii are used to calculate theoretical emission line ratios involving both n=0 (2–2) and n=1 (2–3) transitions in the 97–895 Å wavelength range. A comparison of these with existing solar observations, obtained by instruments on rocket flights and on the Skylab mission, reveals generally good agreement between theory and observation. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations, and implies that the latter may be applied with confidence to the analysis of solar and stellar spectra from current and future satellite missions.  相似文献   

A model approach to radioactive waste disposal at Sellafield     

R. S. Haszeldine  C. McKeown 《地学学报》1995,7(1):87-95

One of the great environmental problems of our age is the safe disposal of radioactive waste for geological time periods. Britain is currently investigating a potential site for underground burial of waste, near the Sellafield nuclear plant. Future leakage of radionuclides depends greatly on subsurface water flows; these must be understood from the past, to predict hydrogeology 10⁴–10⁵ years into the future. We have taken information from the present-day, published by the government company Nirex, and used a finite-element steady-state fluid flow computer code to examine water flows in the subsurface. We find that flow directions at the planned Repository are persistently upwards, and that geologically significant flow rates could occur. How rates are particularly sensitive to uncertainties of rock permeability (conductivity) measurements made from site investigation boreholes. The hydrogeology at this site needs longer term investigation before a confident and credible prediction can be made.  相似文献   

Phylogeny of the Sepia officinalis species complex in the eastern Atlantic extends the known distribution of Sepia vermiculata across the Benguela upwelling region     

AJE Healey  NJ McKeown  WM Potts  CL de Beer  W Sauer  PW Shaw 《African Journal of Marine Science》2017,39(3):307-313

Accurate species identification and biogeographic characterisation are fundamental for appropriate management of expanding cephalopod fisheries. This study addresses this topic within the common cuttlefish Sepia officinalis species complex (S. officinalis, S. hierredda and S. vermiculata), with an emphasis on occurrence in African waters. Tissue samples from the currently presumed distributions of S. vermiculata and S. hierredda (from South Africa and Ghana/Angola, respectively) were sequenced for the cytochrome c oxidase subunit I (COI) and the cytochrome b (cytb) genes of the mitochondrial genome and then compared to existing S. officinalis sequences. Three highly divergent and reciprocally monophyletic clades, corresponding to S. officinalis, S. hierredda and S. vermiculata, were resolved, representing the first molecular confirmation of the distinct species status of S. hierredda and S. vermiculata. The sequences also revealed that, contrary to expectations based on presently published information, all samples from southern Angola were S. vermiculata. These results indicate that the range of S. vermiculata extends beyond the currently described northern limit and that S. hierredda and S. vermiculata may be indiscriminately harvested in Angolan waters. Finer-scale patterns within S. vermiculata phylogeography also indicate that the Benguela Current System and/or other environmental factors serve to isolate northern and southern stocks.  相似文献   

Detection of oil-water interfaces in sunken oil tankers     

McKeown  D. George  K. Young  S. 《Oceanic Engineering, IEEE Journal of》1980,5(4):225-228

A nondestructive method of measuring in situ the oil-water interface in a sunken oil barge is described. The method makes use of the different acoustic absorption properties of water and BunkerCoil to detect the oil-water interface and can be implemented using a standard 200-kHz echo sounder. An electrically driven bottom-crawling remotely controlled vehicle used to carry out field tests on a sunken oil barge is described, and samples of the sounder records obtained are presented. Results indicate the method is feasible for tanks of simple geometry that have distinct layers of liquids with sufficiently different acoustic absorption properties.  相似文献   

Aluminum X-ray absorption near-edge spectra of some oxide minerals: Calculation versus experimental data     

David A. McKeown 《Physics and Chemistry of Minerals》1989,16(7):678-683

Al X-ray absorption K-edge spectra were calculated for atom clusters which simulate Al surrounded by oxygens in tetrahedral and octahedral environments in five minerals, and are compared with experimental Al K-edge spectra from the same minerals. The experimental data show simple edges, for Al tetrahedra, that are shifted to lower energy by 2 eV compared with more complicated edges for Al octahedra. The calculated edge itself is due to a strong 1s to 3p resonance in the μ₀ for Al. The shifting of the calculated edges is due to different molecular potentials used and different types of atomic scattering. The calculated edge features for tetrahedral Al are all similar, and are due primarily to single scattering from the tetrahedral oxygens. Calculated edge features for octahedral Al are more complicated and are dominated by multiple scattering. The calculated edge features resemble the experimental data, but are much larger in amplitude than their experimental counterparts.  相似文献   

Vibrational analysis of dioptase Cu6Si6O18 · 6(H2O) and its puckered six-membered ring     

David A. McKeown  Charles C. Kim  Michael I. Bell 《Physics and Chemistry of Minerals》1995,22(3):137-144

The normal modes of vibration and their frequencies are calculated for dioptase, a mineral whose crystal structure (space group R or C _3i ² ) consists of puckered six-membered silicate rings (Si₆O₁₈) linked by Cu²⁺ ions and H₂O groups. The calculation employs a valence force potential consisting of central interactions between nearest neighbors and bond-bending interactions centered at the Si⁴⁺ and Cu²⁺ ions. The force constants are determined by fitting the calculated frequencies to values obtained by measuring the single-crystal Raman spectra. The calculated frequencies are in reasonable agreement with experiment, permitting assignment of normal modes to the observed spectral frequencies. Considerable mixing of Cu and H₂O motions with those of the ring is found for the Raman-active modes below 430 cm^-1. The normal modes and frequencies of the hypothetical isolated ring with C _3i symmetry are determined by neglecting all interactions between the rings and the surrounding Cu and H₂O. The identification of normal modes characteristic of the puckered six-membered silicate rings and the effect of the environment on these modes may prove useful in the interpretation of the Raman spectra of amorphous silicates.  相似文献   

Landslide databases in the Geological Surveys of Europe     

Gerardo Herrera  Rosa María Mateos  Juan Carlos García-Davalillo  Gilles Grandjean  Eleftheria Poyiadji  Raluca Maftei  Tatiana-Constantina Filipciuc  Mateja Jemec Auflič  Jernej Jež  Laszlo Podolszki  Alessandro Trigila  Carla Iadanza  Hugo Raetzo  Arben Kociu  Maria Przyłucka  Marcin Kułak  Michael Sheehy  Xavier M. Pellicer  Charise McKeown  Graham Ryan  Veronika Kopačková  Michaela Frei  Dirk Kuhn  Reginald L. Hermanns  Niki Koulermou  Colby A. Smith  Mats Engdahl  Pere Buxó  Marta Gonzalez  Claire Dashwood  Helen Reeves  Francesca Cigna  Pavel Liščák  Peter Pauditš  Vidas Mikulėnas  Vedad Demir  Margus Raha  Lídia Quental  Cvjetko Sandić  Balazs Fusi  Odd Are Jensen 《Landslides》2018,15(2):359-379

Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km² landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm² (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.  相似文献