Dominance of Tilapia mossambica,an introduced fish species,in three Puerto Rican estuaries     

Joanna Burger  Keith Cooper  Deborah J. Gochfeld  Jorge E. Saliva  Carl Safina  David Lipsky  Michael Gochfeld 《Estuaries and Coasts》1992,15(2):239-245

We compared species presence, abundance, and size characteristics of fish in three brackish, coastal marshes at Humacao, Roosevelt Roads, and Boqueron, Puerto Rico, in February and March 1988. The three marsh ecosystems were similar with respect to the presence of large expanses of open water bordered by emergent vegetation, creeks, and mangroves, and all had some recreational use. We sampled fish using gill nets. Tilapia (Oreochromis) mossambica were the most abundant fish, accounting for 55–79% of the samples at all three marshes. Overall, tilapia were both the largest (North Lagoon) and the smallest (Frontera Creek) at Humacao. Tilapia were most common in open lagoons rather than creeks or bays (except for Mandri Creek), and their distribution seemed unrelated to salinity. Tarpon (Megalops atlantica) were more abundant at low salinities, whereas other fish were more abundant at higher salinities.  相似文献   

Aspects of the statistical analysis of marine ore deposits     

H. Burger  W. Ehrismann  W. Skala 《Mineralium Deposita》1980,15(3):335-350

Geostatistical analyses employed in the prospecting and for exploration of marine mineral resources, must be aimed at particular problems and goals. The quality of navigation, sampling, mining technology and the profitability of the project strongly influence such analyses. The studies presented here, have two main objectives, namely, to estimate the reserves of manganese nodules and to determine in what order the explored areas should be mined. Several geostatistical methods were used. These were designed partly to supplement one another, but mostly to create a sequence of analytical steps which could be applied to any typical marine exploration project.

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Zusammenfassung Sollen im Rahmen von Prospektions- und Explorationsvorhaben auf marine Rohstoffe geostatistische Untersuchungen durchgeführt werden, so haben sich diese an den speziellen Problemen und Zielsetzungen zu orientieren. Dabei spielen Fragen der Navigation, der Probennahme, der Förderungstechnik und der Wirtschaftlichkeit eine wichtige Rolle. Im vorliegenden Falle war das Ziel der Untersuchungen nach der Schätzung der Vorräte an Mangan-Knollen die Erstellung einer Rangordnung der Explorations-Areale für den Abbau. Hierzu wurden verschiedene Verfahren der Geostatistik eingesetzt, die sich zum Teil gegenseitig zu ergänzen haben, im Großen gesehen jedoch eine Methoden-Folge bilden, die als typisch für Explorations-Projekte auf marine Rohstoffe angesehen werden kann.

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Time‐Lapse Electrical Geophysical Monitoring of Amendment‐Based Biostimulation          下载免费PDF全文

Timothy C. Johnson  Roelof J. Versteeg  Frederick D. Day‐Lewis  William Major  John W. Lane Jr. 《Ground water》2015,53(6):920-932

Biostimulation is increasingly used to accelerate microbial remediation of recalcitrant groundwater contaminants. Effective application of biostimulation requires successful emplacement of amendment in the contaminant target zone. Verification of remediation performance requires postemplacement assessment and contaminant monitoring. Sampling‐based approaches are expensive and provide low‐density spatial and temporal information. Time‐lapse electrical resistivity tomography (ERT) is an effective geophysical method for determining temporal changes in subsurface electrical conductivity. Because remedial amendments and biostimulation‐related biogeochemical processes often change subsurface electrical conductivity, ERT can complement and enhance sampling‐based approaches for assessing emplacement and monitoring biostimulation‐based remediation. Field studies demonstrating the ability of time‐lapse ERT to monitor amendment emplacement and behavior were performed during a biostimulation remediation effort conducted at the Department of Defense Reutilization and Marketing Office (DRMO) Yard, in Brandywine, Maryland, United States. Geochemical fluid sampling was used to calibrate a petrophysical relation in order to predict groundwater indicators of amendment distribution. The petrophysical relations were field validated by comparing predictions to sequestered fluid sample results, thus demonstrating the potential of electrical geophysics for quantitative assessment of amendment‐related geochemical properties. Crosshole radar zero‐offset profile and borehole geophysical logging were also performed to augment the data set and validate interpretation. In addition to delineating amendment transport in the first 10 months after emplacement, the time‐lapse ERT results show later changes in bulk electrical properties interpreted as mineral precipitation. Results support the use of more cost‐effective surface‐based ERT in conjunction with limited field sampling to improve spatial and temporal monitoring of amendment emplacement and remediation performance.  相似文献   

Zur Inaktivierung von Erregern übertragbarer Krankheiten in Gewässern     

G. Burger 《洁净——土壤、空气、水》1990,18(6):667-671

Germs of infectious diseases are not adapted to the environment of waters but to their hosts. Therefore, as allochthonous elements they survive there only for a short time for the most part; individual germs, however, are much more resistant under these environmental conditions, in dependence on their species or type. At a higher initial germ content the period of survival in general is longer than at a lower one. For inactivation in waters e.g. the following causes may be responsible: nutrient deficiency, unfavourable water temperature, redox potential, saprobity, chemical constituents, including metabolic products of aquatic organisms, solar light osmotic pressure, settling material and suspended solids, bacteriophages.  相似文献   

Carbon dioxide photoelectron energy peaks at Mars     

R.A. Frahm  J.D. Winningham  J.R. Scherrer  A.J. Coates  D.O. Kataria  S. Barabash  H. Andersson  A. Grigoriev  T. Säles  W. Schmidt  J.U. Kozyra  E.C. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-A. Sauvaud  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):371-382

The ELectron Spectrometer (ELS) from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) flown on the Mars Express spacecraft has an 8% energy resolution, combined with the capability to oversample the martian electron distribution. This makes possible the resolution and identification of electrons generated as a result of the He 304 Å ionization of CO₂ at the martian exobase on the dayside of the planet. Ionospheric photoelectrons were observed during almost every pass into the ionosphere and CO₂ photoelectron peaks were identified near the terminator. Atmospherically generated CO₂ photoelectrons are also observed at 10,000 km altitude in the martian tail near the inner magnetospheric boundary. Observations over a wide range of spacecraft orbits showed a consistent presence of photoelectrons at locations along the inner magnetospheric boundary and in the ionosphere, from an altitude of 250 to 10,000 km.  相似文献   

Plasma intrusion above Mars crustal fields—Mars Express ASPERA-3 observations     

M. Fränz  J.D. Winningham  E. Roussos  S. Barabash  M. Holmström  M. Yamauchi  R.A. Frahm  J.R. Scherrer  Y. Soobiah  D.O. Kataria  T. Säles  W. Schmidt  J. Kozyra  E. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-A. Sauvaud  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  K. Asamura 《Icarus》2006,182(2):406-412

Using data of the ASPERA-3 instrument on board the European Mars Express spacecraft we investigate the effect of the martian crustal fields on electrons intruding from the magnetosheath. For the crustal field strength we use published data obtained by the Mars Global Surveyor MAG/ER instrument for a fixed altitude of 400 km. We use statistics on 13 months of 80-100 eV electron observations to show that the electron intrusion altitude determined by a probability measure is approximately linearly dependent on the total field strength at 400 km altitude. We show that on the dayside the mean electron intrusion altitude describes the location of the Magnetic Pile-Up Boundary (MPB) such that we can quantify the effect of the crustal fields on the MPB. On the nightside we quantify the shielding of precipitating electrons by the crustal fields.  相似文献   

Europa's neutral cloud: morphology and comparisons to Io     

Matthew H. Burger  Robert E. Johnson 《Icarus》2004,171(2):557-560

Ground based observations of sodium escaping from Europa suggest the presence of an extended cloud of neutrals orbiting Jupiter. Using a Monte Carlo model we show that the large scale morphology differs from the sodium cloud at Io. At Europa, the trailing cloud is brighter and more extended than the leading cloud. We then use our results to consider the morphology of Europa's oxygen cloud.  相似文献   

The origin of young mare basalts inferred from lunar meteorites Northwest Africa 4734, 032, and LaPaz Icefield 02205     

Stephen M. Elardo  Charles K. Shearer Jr.  Amy L. Fagan  Lars E. Borg  Amy M. Gaffney  Paul V. Burger  Clive R. Neal  Vera A. Fernandes  Francis M. McCubbin 《Meteoritics & planetary science》2014,49(2):261-291

Northwest Africa (NWA) 4734 is an unbrecciated basaltic lunar meteorite that is nearly identical in chemical composition to basaltic lunar meteorites NWA 032 and LaPaz Icefield (LAP) 02205. We have conducted a geochemical, petrologic, mineralogic, and Sm‐Nd, Rb‐Sr, and Ar‐Ar isotopic study of these meteorites to constrain their petrologic relationships and the origin of young mare basalts. NWA 4734 is a low‐Ti mare basalt with a low Mg* (36.5) and elevated abundances of incompatible trace elements (e.g., 2.00 ppm Th). The Sm‐Nd isotope system dates NWA 4734 with an isochron age of 3024 ± 27 Ma, an initial ε_Nd of +0.88 ± 0.20, and a source region ¹⁴⁷Sm/¹⁴⁴Nd of 0.201 ± 0.001. The crystallization age of NWA 4734 is concordant with those of LAP 02205 and NWA 032. NWA 4734 and LAP 02205 have very similar bulk compositions, mineral compositions, textures, and ages. Their source region ¹⁴⁷Sm/¹⁴⁴Nd values indicate that they are derived from similar, but distinct, source materials. They probably do not sample the same lava flow, but rather are similarly sourced, but isotopically distinct, lavas that probably originate from the same volcanic complex. They may have experienced slightly different assimilation histories in route to eruption, but can be source‐crater paired. NWA 032 remains enigmatic, as its source region ¹⁴⁷Sm/¹⁴⁴Nd definitively precludes a simple relationship with NWA 4734 and LAP 02205, despite a similar bulk composition. Their high Ti/Sm, low (La/Yb)_N, and Cl‐poor apatite compositions rule out the direct involvement of KREEP. Rather, they are consistent with low‐degree partial melting of late‐formed LMO cumulates, and indicate that the geochemical characteristics attributed to urKREEP are not unique to that reservoir. These and other basaltic meteorites indicate that the youngest mare basalts originate from multiple sources, and suggest that KREEP is not a prerequisite for the most recent known melting in the Moon.  相似文献   

Zur Verringerung des Bakteriengehaltes kontaminierten Wassers durch Wasserpflanzen     

G. Burger  H. Nagel  G. Weise 《洁净——土壤、空气、水》1979,7(2):273-276

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Photographs of the Sun in the XUV-region     

M. Burger  J. H. Dijkstra 《Solar physics》1972,24(2):395-404

X-ray photographs obtained with a zone plate camera on October 3, 1967 in the wavelength band 49.5–52.5 Å have been investigated photometrically.The most intense X-ray emission corresponds with active regions in H and Ca ii. About one quarter of the total solar flux is emitted by the three brightest X-ray sources (A, E and J). X-ray emission from quiet regions is also observed. Limb brightening is found, also at the poles, which indicates a higher electron density at the poles than during solar minimum.The brightest X-ray regions have a very small core of the order of 20. No relation to magnetic field strengths of sunspots has been found. However, a correlation with active prominences cannot be ruled out. X-ray source A is related either to prominence activity or to flare activity. One X-ray region (J) is probably related to flare activity.Assuming an electron temperature of 3 × 10⁶K to 5 × 10⁶K for coronal active regions an emission measure of a few times 10⁴⁹ cm^–3 is derived, which yields an electron density of a few times 10¹⁰ cm^–3.  相似文献