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  • 1
    Publication Date: 2024-04-20
    Description: The manganese crust was retrieved from station 1052 during the 14th cruise of the R/V Dmitry Mendeleev. The station is located in Hess Deep in the axis of the Galapagos Spreading Center, just east of its junction with the East Pacific Rise. It consists of 16 mm of ferromanganese material encrusting fresh basaltic glass (see illustration). Analyses were performed by instrumental neutron activation analysis except for Cu and Ni which were determined by atomic absorption. Microprobe analyses of the underlying glass reveal typical ocean theolitic composition with low alkalis and a SiO2 content of about 50%. They are compared to other published data from the Galapagos Spreading Center, the Mid-Atlantic Ridge and the flank of the East Pacific Rise.
    Keywords: Atomic absorption spectroscopy; Cobalt; Copper; Deposit type; Distance; Distance, maximum; Distance, minimum; DM14; DM14-1052; Dmitry Mendeleev; Elevation of event; Event label; Geochemistry; Grab; GRAB; Identification; Image; Iron; Latitude of event; Longitude of event; Manganese; manganese micronodule; manganese nodule; Neutron activation analysis; Nickel; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; ocean; sediment; Southeast Pacific; Zinc
    Type: Dataset
    Format: text/tab-separated-values, 12 data points
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  • 2
    Publication Date: 2022-06-07
    Description: A complex approach in characterisation of submarine groundwater discharge (SGD) off south-eastern Sicily comprising applications of radioactive and non-radioactive tracers, direct seepage measurements, geophysical surveys and a numerical modelling is presented. SGD fluxes in the Donnalucata boat basin were estimated by direct seepage measurements to be from 4 to 12 L s 1, which are comparable with the total SGD flux in the basin of 17 L s 1 obtained from radon measurements. The integrated SGD flux over the Donnalucata coast estimated on the basis of Ra isotopes was around 60 m3 s 1 per km of the coast. Spatial variations of SGD were observed in the Donnalucata boat basin, the average 222Rn activity concentration in seawater varied fromw0.1 kBq m 3 to 3.7 kBq m 3 showing an inverse relationship with salinity. The continuous monitoring carried out at the site closest to the coast has revealed an inverse relationship of 222Rn activity concentration on the tide. The 222Rn concentrations in seawater varied from 2.3 kBq m 3 during high tides to 4.8 kBq m 3 during low tides, thus confirming an influence of the tide on submarine groundwater discharge. Stable isotopes (d2H and d18O) showed that SGD samples consist up to 50% of groundwater. Geo-electrical measurements showed a spatial variability of the salt/ fresh water interface and its complex transformation in the coastal zone. The presented results imply that in the studied Donnalucata site there are at least two different sources of SGD, one superficial, represented by mixed fresh water and seawater, and the second one which originates in a deeper limestone aquifer.
    Description: Published
    Description: 81-101
    Description: JCR Journal
    Description: reserved
    Keywords: Submarine groundwater discharge ; Groundwater ; Seawater ; Radioactive and stable isotopes; ; Seepage measurement ; Geophysical survey ; Numerical modelling ; Mediterranean Sea ; 03. Hydrosphere::03.02. Hydrology::03.02.03. Groundwater processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 254 (1975), S. 42-44 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Index and core location map showing general bathymetry in the 12S region of the Nazca plate. The Bauer Deep, located between the East Pacific Rise and a fossil spreading centre, the Galapagos Rise8, is an area of sediment accumulation rich in metals (Fig. 1). This sediment may originate ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 302 (1983), S. 601-603 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Phosphatic limestone occurs on the continental margin off South Africa and Namibia in a broad (75 km wide) nearly continuous pavement on the southern and eastern Agulhas Bank (Fig. 1), in a narrow zone (25 km wide) near the shelf-break on its southwestern margin and in extensive but discontinuous ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    GeoJournal 4 (1980), S. 423-435 
    ISSN: 1572-9893
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract Phosphate trade in the Pacific Basin is dominated by imports from outside the region. The principal suppliers within the area have been Nauru and Christmas Islands and the now depleted supplies of Makatea and Ocean Islands. Rapidly dwindling reserves on these islands coupled with expectations of a four to five fold increase in demand of phosphate fertilizer by the end of this century place considerable stress on the phosphate supply system in the Pacific. Anticipated developments in production from inactive deposits in Australia, Peru, and possibly Baja California, Mexico may eventually hold a major share in the Pacific markets. Other possibilities in the region include contributions from new discoveries and utilization of submarine deposits, especially those of the Chatham Rise and Baja California areas. Increased interest in small-scale mining for use in local agricultural operations may result in increased utilization of smaller deposits found throughout the Pacific.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 235 (1998), S. 173-178 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Although potentially very useful as a screening tool, currently-applied “gross” alpha/beta analyses are often considered unreliable by the environmental monitoring community. We describe here an alternative approach based on direct counting of pressed soil “wafers” to estimate total alpha/beta activities. The system was calibrated using a series of natural soils and sediment standards with total α/β activities estimated by use of a combination of available certified values, equilibrium assumptions, and our own measurements. A set of 10 such standards that span a wide range of activities were prepared by thoroughly mixing several grams of selected NIST and IAEA natural matrix standards together with reagent grade cellulose in a 4∶1 sample-to-binder ratio and pressing in a 40-mm stainles steel die. The resulting wafers, assumed to be at infinite thickness for expected radionuclides, were counted in a gas flow proportional counter set for simultaneous α/β counting. Both the alpha and beta count rates increased in a linear, systematic manner with increasing total estimated activities. This technique should prove to be an inexpensive, simple, and waste-free approach for screening total radioactivity in soil samples.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 193 (1995), S. 281-290 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A simple technique for measurement of the soil-atmosphere radon flux has been developed by fastening a charcoal canister inside a PVC cylindrical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister and measurement of the radon daughter activity on a NaI detector, the radon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of charcoal canisters to226Ra-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the222Rn generated during radium decay, it forms a useful “flux standard.” The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or “accumulator” method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were based on single overnight deployments. The experiment was repeated 5 times at two different sites and the two techniques generally agreed within a 95% confidence interval.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The analysis of environmental samples for low levels of U, Pu, Am and other actinide elements is often hampered by sample-dependent problems involving the composition and/or mineralogy of specific samples. While relatively small samples (1–2 g of soil or 1–2 of water) are required to reach the extremely low detection limits occasionally mandated for environmental monitoring. One approach to avoid the troublesome and often inexplicable problems collectively referred to as “matrix effects” is to pre-concentrate actinides into a common form that would then behave uniformly and predictably during a subsequent separation scheme. Recently, a new extraction chromatographic resin based on diphosphonate chemistry was developed at Argonne National Laboratory. This resin commercialized as Eichrom's Actinide Resin, exhibits extremely high affinity for actinide elements even in the presence of high concentrations of salts. We have measured the uptake of actinides by the Dipex® extractant from natural waters and natural matrix soil standards. Water samples have been analyzed for gross α-activities and gave results that compared favorably to the traditional approach. In addition, we have obtained good recoveries and excellent separations for soil samples as judged by resolution on the α-spectra and the complete absence of interfering energies.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 236 (1998), S. 247-253 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Determination of sedimentary fluxes of222Rn via diffusion was required as an input for a mass balance model of radon in a freshwater lake. We obtained these fluxes by: (1) direct measurement in the laboratory using a simulated sediment bed and water column; (2) a “sediment equilibration” technique; and (3) porewater modeling. The first method, analogous to an in situ benthic chamber approach, uses direct observation of the increasing222Rn activity in water overlying a sediment bed packed in plastic columns. This allows one to directly measure the fluxes and determine the effective wet bulk sediment diffusion coefficient (D s). Radon flux estimates using these three techniques agreed to within approximately 10–15%.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2018-03-08
    Description: Submarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes and nutrients. SGD intercomparison exercises were carried out to validate the various approaches used to measure SGD including radium and radon measurements, seepage rate measurements using manual and automated meters, sediment bulk conductivity and salinity surveys. SGD measurements using benthic chambers placed on the floor of the Flic-en-Flac Lagoon showed discharge rates up to 500 cm/day. Large variability in SGD was observed over distances of a few meters, which were attributed to different geomorphological features. Deployments of automated seepage meters captured the spatial and temporal variability of SGD with a mean seepage rate of 10 cm/day. The stable isotopic composition of submarine waters was characterized by significant variability and heavy isotope enrichment and was used to predict the contribution of fresh terrestrially derived groundwater to SGD (range from a few % to almost 100%). The integrated SGD flux, estimated from seepage meters placed parallel to the shoreline, was 35 m3/m day, which was in reasonable agreement with results obtained from a hydrologic water balance calculation (26 m3/m day). SGD calculated from the radon inventory method using in situ radon measurements were between 5 and 56 m3/m per day. Low concentrations of radium isotopes observed in the lagoon water reflected the low abundance of U and Th in the basalt that makes up the island. High SGD rates contribute to high nutrients loading to the lagoon, potentially leading to eutrophication. Each of the applied methods yielded unique information about the character and magnitude of SGD. The results of the intercomparison studies have resulted a better understanding of groundwater–seawater interactions in coastal regions. Such information is an important pre-requisite for the protection and management of coastal freshwater resources. Highlights ► Large fluctuations in SGD fluxes from 0 to 360 cm/day were observed. ► The integrated shoreline SGD fluxes were between 5 and 56 m3/m day. ► The groundwater contribution in SGD varied from a few % to almost 100%. ► The observed high SGD rates contributed to high nutrients loading to the lagoon.
    Type: Article , PeerReviewed
    Format: text
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