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  • Marine Geosciences and Applied Geophysics  (2)
  • Adsorption maxima  (1)
  • 1
    ISSN: 1573-5036
    Keywords: Adsorption maxima ; Buffer capacity ; Quantity/intensity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Adsorption of zinc in rice soils was studied to define the functional relationship between quantity, intensity and buffering capacity factors of soil zinc to the growth and zinc uptake of rice crop. A supply parameter integrating the quantity, intensity and buffering capacity factors into a single unifying term was computed from the data on Zn adsorption in these soils. A green house experiment was conducted with three soils providing a matrix of different values of supply parameter of Zn to determine the optimum value of this parameter for the proper growth and zinc nutrition of rice crop. Results indicated that a value of this parameter around unity is optimum for sustaining proper growth and zinc nutrition of rice in these soils. The variations in dry matter yield and zinc uptake of rice in different soils may be related to the differences in the physical and chemical properties of the soils.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-06-23
    Description: Deep sea pockmarks underlain by chimney-like or pipe structures that contain methane hydrate are abundant along the Norwegian continental margin. In such hydrate provinces the interaction between hydrate formation and fluid flow has significance for benthic ecosystems and possibly climate change. The Nyegga region, situated on the western Norwegian continental slope, is characterized by an extensive pockmark field known to accommodate substantial methane gas hydrate deposits. The aim of this study is to detect and delineate both the gas hydrate and free gas reservoirs at one of Nyegga's pockmarks. In 2012, a marine controlled-source electromagnetic (CSEM) survey was performed at a pockmark in this region, where high-resolution 3-D seismic data were previously collected in 2006. 2-D CSEM inversions were computed using the data acquired by ocean bottom electrical field receivers. Our results, derived from unconstrained and seismically constrained CSEM inversions, suggest the presence of two distinctive resistivity anomalies beneath the pockmark: a shallow vertical anomaly at the underlying pipe structure, likely due to gas hydrate accumulation, and a laterally extensive anomaly attributed to a free gas zone below the base of the gas hydrate stability zone. This work contributes to a robust characterization of gas hydrate deposits within subseafloor fluid flow pipe structures.
    Keywords: Marine Geosciences and Applied Geophysics
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 3
    Publication Date: 2016-10-09
    Description: The Arctic continental margin contains large amounts of methane in the form of methane hydrates. The west Svalbard continental slope is an area where active methane seeps have been reported near the landward limit of the hydrate stability zone. The presence of bottom simulating reflectors (BSRs) on seismic reflection data in water depths greater than 600 m suggests the presence of free gas beneath gas hydrates in the area. Resistivity obtained from marine controlled source electromagnetic (CSEM) data provides a useful complement to seismic methods for detecting shallow hydrate and gas as they are more resistive than surrounding water saturated sediments. We acquired two CSEM lines in the west Svalbard continental slope, extending from the edge of the continental shelf (250 m water depth) to water depths of around 800 m. High resistivities (5–12 m) observed above the BSR support the presence of gas hydrate in water depths greater than 600 m. High resistivities (3–4 m) at 390–600 m water depth also suggest possible hydrate occurrence within the gas hydrate stability zone (GHSZ) of the continental slope. In addition, high resistivities (4–8 m) landward of the GHSZ are coincident with high-amplitude reflectors and low velocities reported in seismic data that indicate the likely presence of free gas. Pore space saturation estimates using a connectivity equation suggest 20–50 per cent hydrate within the lower slope sediments and less than 12 per cent within the upper slope sediments. A free gas zone beneath the GHSZ (10–20 per cent gas saturation) is connected to the high free gas saturated (10–45 per cent) area at the edge of the continental shelf, where most of the seeps are observed. This evidence supports the presence of lateral free gas migration beneath the GHSZ towards the continental shelf.
    Keywords: Marine Geosciences and Applied Geophysics
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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