Disinfection by-products and ecotoxicity of ballast water after oxidative treatment – Results and experiences from seven years of full-scale testing of ballast water management systems     

Stephanie Delacroix  Christian VogelsangAugust Tobiesen  Helge Liltved 《Marine pollution bulletin》2013

Since 2005, five different ballast water management systems (BWMSs) based on chlorination treatment have been tested by Norwegian Institute for Water Research (NIVA) according to guidelines from the International Maritime Organization (IMO). 25% and >50% of all the tested discharge samples exhibited acute and chronic toxic effects on algae, respectively. In most cases this toxicity was plausibly caused by a high free residual oxidant (FRO) level (>0.08 mg Cl/l). Of the 22 disinfection by-products (DBPs) that were identified in treated water at discharge, four compounds were at times found at concentrations that may pose a risk to the local aquatic environment. However, there seemed to be no clear indication that the measured DBP concentrations contributed to the observed algal toxicity. The addition of methylcellulose instead of lignin in the test water to comply with IMO requirements seemed to limit the formation of DBP.  相似文献   

Measuring bluff erosion part 2: pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget     

Stephanie S. Day  Karen B. Gran  Patrick Belmont  Tim Wawrzyniec 《地球表面变化过程与地形》2013,38(10):1068-1082

Effectively managing and reducing high suspended sediment loads in rivers requires an understanding of the magnitude of major sediment sources as well as erosion and transport processes that deliver excess fine sediments to the channel network. The focus of this research is to determine the magnitude of erosion from tall bluffs, a primary sediment source in the 2880 km² Le Sueur watershed, Minnesota, USA. We coupled analyses of seven decades of aerial photographs with four years of repeat terrestrial laser scanning (TLS) to determine erosion rates on bluffs. Together, these datasets provide decadal‐scale retreat rates throughout the entire watershed and high‐resolution geomorphic change detection on a subset of bluffs to both constrain erosion rates and document how environmental conditions affect bluff retreat. Erosion rates from aerial photographs and TLS were extrapolated from 243 and 15 measured bluffs, respectively, to all 480 bluffs in the Le Sueur watershed using multiple techniques to obtain estimates of sediment loading from these features at the watershed‐scale. Despite different spatial and temporal measurement scales, the aerial photograph and TLS estimates yielded similar results for bluff retreat rate and total mass of sediment derived from bluffs, with bluffs in the Le Sueur watershed yielding 135 000 ± 39 000 Mg/yr of fine sediment. Comparing this value to the average annual total suspended solids (TSS) load determined from gauging from 2000 to 2010, we determined that bluffs comprise 57 ± 16% of the total TSS load, making bluffs the single most abundant fine sediment source in the basin. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Gas migration through Opouawe Bank at the Hikurangi margin offshore New Zealand     

Stephanie Koch  Henning Schroeder  Matthias Haeckel  Christian Berndt  Joerg Bialas  Cord Papenberg  Dirk Klaeschen  Andreia Plaza-Faverola 《Geo-Marine Letters》2016,36(3):187-196

This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO₂ reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.  相似文献   

Detection of Earth-mass and super-Earth Trojan planets using transit timing variation method     

Nader Haghighipour  Stephanie Capen  Tobias C. Hinse 《Celestial Mechanics and Dynamical Astronomy》2013,117(1):75-89

We have carried out an extensive study of the possibility of the detection of Earth-mass and super-Earth Trojan planets using transit timing variation method with the Kepler space telescope. We have considered a system consisting of a transiting Jovian-type planet in a short period orbit, and determined the induced variations in its transit timing due to an Earth-mass/super-Earth Trojan planet. We mapped a large section of the phase space around the 1:1 mean-motion resonance and identified regions corresponding to several other mean-motion resonances where the orbit of the planet would be stable. We calculated transit timing variations (TTVs) for different values of the mass and orbital elements of the transiting and perturbing bodies as well as the mass of central star, and identified orbital configurations of these objects (ranges of their orbital elements and masses) for which the resulted TTVs would be within the range of the variations of the transit timing of Kepler’s planetary candidates. Results of our study indicate that in general, the amplitudes of the TTVs fall within the detectable range of timing precision obtained from the Kepler’s long-cadence data, and depending on the parameters of the system, their magnitudes may become as large as a few hours. The probability of detection is higher for super-Earth Trojans with slightly eccentric orbits around short-period Jovian-type planets with masses slightly smaller than Jupiter. We present the details of our study and discuss the implications of its results.  相似文献   

Astrophysically relevant radiation hydrodynamics experiment at the National Ignition Facility     

C. C. Kuranz  H.-S. Park  B. A. Remington  R. P. Drake  A. R. Miles  H. F. Robey  J. D. Kilkenny  C. J. Keane  D. H. Kalantar  C. M. Huntington  C. M. Krauland  E. C. Harding  M. J. Grosskopf  D. C. Marion  F. W. Doss  E. Myra  B. Maddox  B. Young  J. L. Kline  G. Kyrala  T. Plewa  J. C. Wheeler  W. D. Arnett  R. J. Wallace  E. Giraldez  A. Nikroo 《Astrophysics and Space Science》2011,336(1):207-211

The National Ignition Facility (NIF) is capable of creating new and novel high-energy-density (HED) systems relevant to astrophysics. Specifically, a system could be created that studies the effects of a radiative shock on a hydrodynamically unstable interface. These dynamics would be relevant to the early evolution after a core-collapse supernova of a red supergiant star. Prior to NIF, no HED facility had enough energy to perform this kind of experiment. The experimental target will include a 340 ??m predominantly plastic ablator followed by a low-density SiO₂ foam. The interface will have a specific, machined pattern that will seed hydrodynamic instabilities. The growth of the instabilities in a radiation-dominated environment will be observed. This experiment requires a ??300?eV hohlraum drive and will be diagnosed using point projection pinhole radiography, which have both been recently demonstrated on NIF.  相似文献   

Alteration of crystalline zircon solid solutions: a case study on zircon from an alkaline pegmatite from Zomba–Malosa, Malawi     

Aneesh Soman  Thorsten Geisler  Frank Tomaschek  Marion Grange  Jasper Berndt 《Contributions to Mineralogy and Petrology》2010,160(6):909-930

A natural, altered zircon crystal from an alkaline pegmatite from the Zomba–Malosa Complex of the Chilwa Alkaline Province in Malawi has been studied by a wide range of analytical techniques to understand the alteration process. The investigated zircon shows two texturally and chemically different domains. Whereas the central parts of the grain (zircon I) appear homogeneous in backscattered electron images and are characterised by high concentrations of trace elements, particularly Th, U, and Y, the outer regions (zircon II) contain significantly less trace elements, numerous pores, and inclusions of thorite, ytttrialite, and fergusonite. Zircon II contains very low or undetectable concentrations of non-formula elements such as Ca, Al, and Fe, which are commonly observed in high concentrations in altered radiation-damaged zircon. U–Pb dating of both zircon domains by LA-ICPMS and SHRIMP yielded statistically indistinguishable U–Pb weighted average ages of 119.3 ± 2.1 (2σ) and 118 ± 1.2 (2σ) Ma, respectively, demonstrating that the zircon had not accumulated a significant amount of self-irradiation damage at the time of the alteration event. Electron microprobe dating of thorite inclusions in zircon II yielded a Th–U-total Pb model age of 122 ± 5 (2σ) Ma, supporting the age relationship between both zircon domains. The hydrothermal solution responsible for the alteration of the investigated zircon was alkaline and rich in CO₃ ²⁻, as suggested by the occurrence of REE carbonates and CO₂-bearing fluid inclusions. The alteration of the crystalline, trace element-rich zircon is explained by an interface-coupled dissolution-reprecipitation mechanism. During such a process, the congruent dissolution of the trace element-rich parent zircon I was spatially and temporally coupled to the precipitation of the trace element-poor zircon II at an inward moving dissolution-precipitation front. The driving force for such a process was merely the difference between the solubility of the trace element-rich and -poor zircon in the hydrothermal solution. The replacement process and the occurrence of mineral inclusions and porosity in the product zircon II is explained by the thermodynamics of solid solution-aqueous solution systems.  相似文献   

Late Pleistocene terrace deposits at Beckford,Worcestershire, England     

D. J. Briggs  G. R. Coope  D. D. Gilbertson 《Geological Journal》1975,10(1):1-16

The Pleistocene deposits in the area of the village of Beckford, in the Carrant Valley, Worcestershire are described. A radio-carbon date of 27,650±250 years B.P. has been obtained from plant material in the terrace deposits in the valley. Detailed studies have been made of the terrace sediments and of the remains of Mollusca and Coleoptera in fossiliferous layers. Frost structures are described and their stratigraphy considered. The nature of the local environment and regional climate in the final stages of the Upton Warren Interstadial period is reconstructed in detail. The terrace appears to have aggraded in a periglacial environment, dominated initially by solifluction processes. Extensive solifluction may have led to local diversions of drainage. In time, the climate deteriorated, becoming cooler and somewhat less continental with the onset of the main Devensian glaciation. This latter stage was characterised by extensive ice-wedge growth, aeolian activity and, subsequently, by river incision.  相似文献   

Skeletal Biomineralization: Patterns,Processes and Evolutionary Trends,Volumes I,and II (Atlas & Index) edited by Joseph G. Carter,Van Nostrand Reinhold,New York, 1990. No. of pages: 832 (Vol. I); 101 + 200 plates (Vol. II). Price £65.00 (2 volume set). ISBN 0–442–00620-9 (Vol. I); 0–442–00666-7 (Vol. II)     

D. E. G. Briggs  M. J. Weedon 《Geological Journal》1992,27(1):92-93

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Use of archaeology to date liquefaction features and seismic events in the New Madrid seismic zone,Central United States     

Martitia P. Tuttle  Robert H. Lafferty  Margaret J. Guccione  Eugene S. Schweig  Neal Lopinot  Robert F. Cande  Kathleen Dyer-Williams  Marion Haynes 《Geoarchaeology》1996,11(6):451-480

Prehistoric earthquake-induced liquefaction features occur in association with Native American occupation horizons in the New Madrid seismic zone. Age control of these liquefaction features, including sand-blow deposits, sand-blow craters, and sand dikes, can be accomplished by extensive sampling and flotation processing of datable materials as well as archaeobotanical analysis of associated archaeological horizons and pits. This approach increases both the amount of carbon for radiocarbon dating and the precision dating of artifact assemblages. Using this approach, we dated liquefaction features at four sites northwest of Blytheville, Arkansas, and found that at least one significant earthquake occurred in the New Madrid seismic zone between A.D. 1180 and 1400, probably about A.D. 1300 ± 100 yr. In addition, we found three buried sand blows that formed between 3340 B.C. and A.D. 780. In this region where very large to great earthquakes appear to be closely timed, archaeology is helping to develop a paleoearthquake chronology for the New Madrid seismic zone. © 1996 John Wiley & Sons, Inc.  相似文献   

Identification of Atlantic water inflow on the north Svalbard shelf during the Holocene     

Marion Peral  William E. N. Austin  Riko Noormets 《第四纪科学杂志》2022,37(1):86-99

Nordaustlandet is located in the northeastern part of the Svalbard archipelago, within the northernmost reach of the West Spitsbergen Current. This current transports Atlantic water to the Arctic Ocean along the western and northern Svalbard margins. This region is well-suited for reconstructing the history of changing Atlantic water inflow to the Arctic Ocean. We studied the marine sediment core HH12-04-GC from Rijpfjorden. Benthic foraminiferal assemblages and sedimentological data are combined to reconstruct the palaeoenvironment of the fjord from the end of the last local deglaciation to the late Holocene. The local deglaciation, between 11.3 and 10.6 cal ka bp , was dominated by active glacier calving processes, associated with a strong inflow of Atlantic water. This led to the establishment of glaciomarine conditions. The Holocene was initially characterised by a relatively stable and warm environment associated with a strong contribution of Atlantic water. Glaciomarine influence progressively decreases after 9.7 cal ka bp and the Atlantic water contribution increases. The late Holocene displayed a similar environment to today, with the influence of glaciomarine conditions and limited Atlantic water inflow. These results confirm that Atlantic water inflows made a continuous contribution to northern Nordaustlandet throughout the postglacial period.  相似文献