Multi-instrument remote and in situ observations of the Erebus Volcano (Antarctica) lava lake in 2005: A comparison with the Pele lava lake on the jovian moon Io     

Ashley Gerard Davies  Julie Calkins  Lucas Scharenbroich  R. Greg Vaughan  Robert Wright  Philip Kyle  Rebecca Castańo  Steve Chien  Daniel Tran 《Journal of Volcanology and Geothermal Research》2008

The stable, persistent, active lava lake at Erebus volcano (Ross Island, Antarctica) provides an excellent thermal target for analysis of spacecraft observations, and for testing new technology. In the austral summer of 2005 visible and infrared observations of the Erebus lava lake were obtained with sensors on three space vehicles Terra (ASTER, MODIS), Aqua (MODIS) and EO-1 (Hyperion, ALI). Contemporaneous ground-based observations were obtained with hand-held infrared cameras. This allowed a quantitative comparison of the thermal data obtained from different instruments, and of the analytical techniques used to analyze the data, both with and without the constraints imposed by ground-truth. From the thermal camera data, in December 2005 the main Erebus lava lake (Ray Lake) had an area of ≈ 820 m². Surface colour temperatures ranged from 575 K to 1090 K, with a broad peak in the distribution from 730 K to 850 K. Total heat loss was estimated at 23.5 MW. The flux density was ≈ 29 kW m^− 2. Mass flux was estimated at 64 to 93 kg s^− 1. The best correlation between thermal emission and emitting area was obtained with ASTER, which has the best combination of spatial resolution and wavelength coverage, especially in the thermal infrared. The high surface temperature of the lava lake means that Hyperion data are for the most part saturated. Uncertainties, introduced by the need to remove incident sunlight cause the thermal emission from the Hyperion data to be a factor of about two greater than that measured by hand-held thermal camera. MODIS also over-estimated thermal output from the lava lake by the same factor of two because it was detecting reflected sunlight from the rest of the pixel area. The measurement of the detailed temperature distribution on the surface of an active terrestrial lava lake will allow testing of thermal emission models used to interpret remote-sensing data of volcanism on Io, where no such ground-truth exists. Although the Erebus lava lake is four orders of magnitude smaller than the lava lake at Pele on Io, the shape of the integrated thermal emission spectra are similar. Thermal emission from this style of effusive volcanism appears to be invariant. Excess thermal emission in most Pele spectra (compared to Erebus) at short wavelengths (< 3 μm) is most likely due to disruption of the surface on the lava lake by escaping volatiles.  相似文献   

Relationships among water column toxins,cell abundance and chlorophyll concentrations during Karenia brevis blooms     

Patricia A. Tester  Damian Shea  Steven R. Kibler  Sabrina M. Varnam  Megan D. Black  R. Wayne Litaker 《Continental Shelf Research》2008

The assumptions that Karenia brevis cell abundance and brevetoxin concentrations are proportional and that cell abundance and chlorophyll are related were tested in a 3-year field study off the west coast of Florida. The relationship between K. brevis cell abundance and brevetoxins (PbTx-2+PbTx-3) in whole water samples was strong (R²=0.92). There was no significant difference between the brevetoxin concentrations in whole water and the >0.7 μm particulate fraction. Only 7% of the total brevetoxin concentration was measured in the <0.7 μm (cell free) filtrate. The relationship of K. brevis cell abundance >5000 cells L⁻¹ with chlorophyll for all cruises and at all depths was robust (R²=0.78). These data substantiate the use of chlorophyll as a proxy for K. brevis cell abundance and K. brevis cell abundance as a proxy for brevetoxins during blooms. The ratios of the brevetoxins, PbTx-2:PbTx-3, was significantly higher in surface water than in bottom water. This information in conjunction with K. brevis growth rates may provide a useful indicator for determining the physiological state of the bloom over time.  相似文献   

Subglacial drumlins and englacial fractures at the surge-type glacier,Múlajökull,Iceland     

Andrew Finlayson  Emrys Phillips  Ívar Örn Benediktsson  Lucas K. Zoet  Neal R. Iverson  Jez Everest 《地球表面变化过程与地形》2019,44(1):367-380

The interaction between drumlins and overriding glacier ice is not well studied, largely due to the difficulty of identifying and accessing suitable active subglacial environments. The surge-type glacier Múlajökull, in central Iceland, overlies a known field of actively forming drumlins and therefore provides a rare opportunity to investigate the englacial structures that have developed in association with ice flow over the subglacial drumlins. In this study detailed ground-penetrating radar surveys are combined with field observations to identify clear sets of up-glacier and down-glacier dipping fractures at Múlajökull's margin. These are interpreted as conjugate shear planes or P- and R-type Reidel shears that developed and filled with saturated sediment derived from the glacier bed, during a previous surge. The fracture sets exhibit focused spatial distributions that are influenced by the subglacial topography. In particular, down-glacier dipping fractures are strongly focused over drumlin stoss slopes. These fractures, although well developed at depth, were mostly unable to transmit basal water and sediment up to the glacier surface during the surge cycle. In contrast, up-glacier dipping fractures formed over drumlin lee sides and in more gently sloping swales, and more frequently connected to the glacier surface, providing a pathway for the evacuation of basal water and water-saturated sediment. The study suggests that the subglacial drumlins under Múlajökull's margin have influenced the nature and distribution of englacial fractures, which could potentially contribute to spatial variations in basal water pressure during a surge. BGS © UKRI 2018  相似文献   

Pesticides from the EU First and Second Watch Lists in the Water Environment     

Damian Pietrzak  Jaros&#x;aw Kania  Grzegorz Malina  Ewa Kmiecik  Katarzyna W&#x;tor 《洁净——土壤、空气、水》2019,47(7)

  相似文献   

Mineralogy and Geochemistry of Rural Road Dust and Nearby Mine Tailings: A Case of Ignored Pollution Hazard from an Abandoned Mining Site in Semi-arid Zone     

Del Rio-Salas  Rafael  Ayala-Ramírez  Yessi  Loredo-Portales  René  Romero  Francisco  Molina-Freaner  Francisco  Minjarez-Osorio  Christian  Pi-Puig  Teresa  Ochoa–Landín  Lucas  Moreno-Rodríguez  Verónica 《Natural Resources Research》2019,28(4):1485-1503

Natural Resources Research - Abandoned mine tailings are considered as one of the main sources of potentially toxic elements. Because of the lack of supervision, particularly from small-scale or...  相似文献   

Towards semantic‐aware multiple‐aspect trajectory similarity measuring     

Lucas May Petry  Carlos Andres Ferrero  Luis Otavio Alvares  Chiara Renso  Vania Bogorny 《Transactions in GIS》2019,23(5):960-975

The large amount of semantically rich mobility data becoming available in the era of big data has led to a need for new trajectory similarity measures. In the context of multiple‐aspect trajectories, where mobility data are enriched with several semantic dimensions, current state‐of‐the‐art approaches present some limitations concerning the relationships between attributes and their semantics. Existing works are either too strict, requiring a match on all attributes, or too flexible, considering all attributes as independent. In this article we propose MUITAS, a novel similarity measure for a new type of trajectory data with heterogeneous semantic dimensions, which takes into account the semantic relationship between attributes, thus filling the gap of the current trajectory similarity methods. We evaluate MUITAS over two real datasets of multiple‐aspect social media and GPS trajectories. With precision at recall and clustering techniques, we show that MUITAS is the most robust measure for multiple‐aspect trajectories.  相似文献   

Progress towards instrument miniaturisation for mid-IR long-baseline interferometry     

Lucas Labadie  Stefano Minardi  Guillermo Martín  Robert R. Thomson 《Experimental Astronomy》2018,46(3):433-445

We report recent results on passive mid-infrared integrated optics from the project “Advanced Laser-writing for Stellar Interferometry” and shortly describe the perspectives of their hybridisation with active components for the benefit of the spectro-interferometry technique.  相似文献   

Palaeomagnetism and magnetostratigraphy of uppermost Permian strata, southeast New Mexico, USA: correlation of the Permian–Triassic boundary in non-marine environments     

Roberto S. Molina Garza  John W. Geissman  & Spencer G. Lucas 《Geophysical Journal International》2000,141(3):778-786

Continental red sandstone and siltstone rocks of the Dewey Lake (Quartermaster) Formation at Maroon Cliffs, near Carlsbad, New Mexico, are characterized by two components of magnetization with partially overlapping laboratory unblocking temperature spectra. Both magnetizations display high coercivities (>100 mT), probably residing in haematite. A north-directed magnetization with steep positive inclination unblocks between 100 and 650 °C, isolating a predominantly northwest-directed magnetization, with shallow inclination, of near uniform normal polarity and maximum unblocking temperatures of 680 °C.
We collected samples from 24 palaeomagnetic sites (i.e. individual beds) from a ~60 m thick section of flat-lying strata disconformably overlying carbonate and evaporite rocks of the Rustler Formation. The upper member of the Rustler Formation contains a Late Permian (early Changxingian) marine invertebrate and conodont fauna. Of the sampled sites, four yield only steep magnetizations, interpreted to be recent overprints. Eight sites did not yield well-grouped site means and were excluded from the final calculations. The formation mean (dec = 337.7°, inc = 9.2°; k = 31.6, α ₉₅ = 7.8°, N = 12 sites) defines a palaeomagnetic pole located at 55.2°N, 117.5°E, in good agreement with other Late Permian North American cratonic poles.
Correlation of the short polarity sequence of this section of Dewey Lake strata is unambiguous. Compared with the polarity stratigraphy of marine sections in Asia, and supported by isotopic age determinations on a widespread bentonite bed in Dewey Lake strata in west Texas (approximately 251 Ma) and fossil data for the underlying Rustler Formation, the magnetostratigraphy is consistent with deposition of the Dewey Lake Formation during the latest Changxingian (Late Permian) stage.  相似文献   

Comparative reproductive biology of two southwestern Atlantic populations of the hermit crab Pagurus exilis (Crustacea: Anomura: Paguridae)     

Mariana Terossi  Lucas S. Torati  Ivana Miranda  Marcelo A. Scelzo  Fernando L. Mantelatto 《Marine Ecology》2010,31(4):584-591

Pagurus exilis (Benedict, 1892) is an endemic South Atlantic hermit crab with a distribution ranging from Rio de Janeiro State, Brazil, to Buenos Aires Province, Argentina. The present study analyzed the reproduction of two populations at the extremes of this geographical distribution, and compared their reproductive period, fecundity, and changes in egg size and egg volume during the incubation period in order to assess the variability over this latitudinal range. Hermit crabs were collected monthly over a 2‐year period. In total, 108 females were analyzed for Brazil (44 non‐ovigerous and 64 ovigerous), and 141 for Argentina (87 non‐ovigerous and 54 ovigerous). Reproduction in Brazil occurs year‐round, with peaks in the fall and winter seasons; in Argentina reproduction occurs only in spring and summer. The Brazilian ovigerous females were significantly larger than the Argentina ones (Brazil: SL = 5.33 ± 1.45 mm; Argentina: SL = 4.15 ± 0.52 mm; P < 0.001). The fecundity was 1447 ± 831 eggs (317 to 2885) in Brazil and 987 ± 711 eggs (114 to 2665) in Argentina, with a trend towards higher fecundity in Brazil. Eggs in the Argentina population were larger than those in Brazil for all the three stages investigated, and no changes in egg volume were found during egg development for both populations. The reproductive traits of the two populations showed some important differences, which may reflect adaptations to local environmental conditions, demonstrating a high plasticity of reproductive features of the species in Brazilian and Argentine waters. The strategy adopted by the Argentina population involves a lower production of larger eggs compared to the population in Brazil; this lower production is associated with reproduction in cold‐water regions.  相似文献   

Tracing of dissolved organic matter from the Sepetiba Bay (Brazil) by PARAFAC analysis of total luminescence matrices   总被引：2，自引：0，他引：2  

Luciani X  Mounier S  Paraquetti HH  Redon R  Lucas Y  Bois A  Lacerda LD  Raynaud M  Ripert M 《Marine environmental research》2008,65(2):148-157

Fluorescent excitation-emission matrices (FEEM) of the fluorescent dissolved organic matter (FDOM) are widely used for DOM characterization and tracing. In this work, a set of FEEM from sampling campaigns in the Sepetiba Bay (Brazil) was decomposed into independent components using the parallel factor analysis (PARAFAC) algorithm. Four independent components were extracted describing the total fluorescence of the FDOM. The well described peaks A, C, M, B and T were found, and a new peak, A', linked to the C peak, was detected. Relative contribution of each of four components to the total fluorescence confirms that the coastal water has DOM of terrestrial origin, except for the 275Ex/400-500Em range (nm), which primarily occurs in marine waters.  相似文献