579 resultados para 855
Resumo:
Concentrations of sulfide, S°, and thiosulfate were determined in waters of the Baltic Sea. Microquantities of these compounds were observed in oxic waters. Concentration levels of reduced sulfur compounds in Baltic oxic waters were very close to levels of the Black Sea oxic zone. Thiosulfate and S° were predominate compounds in oxic water whereas sulfide was a predominant compound of Baltic waters high in hydrogen sulfide. Conclusion was made that during sedimentation in oxic waters anaerobic microorganisms along with aerobic bacteria take part in mineralization of organic matter. They exist on surfaces and in microniches of particles of organic detritus.
Resumo:
In this paper, modernized shipborne procedures are presented to collect and process above-water radiometry for remote sensing applications. A setup of five radiometers and a bidirectional camera system, which provides panoramic sea surface and sky images, is proposed for the collection of high-resolution radiometric quantities. Images from the camera system can be used to determine sky state and potential glint, whitecaps, or foam contamination. A peak in the observed remote sensing reflectance RRS spectra between 750-780 nm was typically found in spectra with relatively high surface reflected glint (SRG), which suggests this waveband could be a useful SRG indicator. Simplified steps for computing uncertainties in SRG corrected RRS are proposed and discussed. The potential of utilizing "unweighted multimodel averaging," which is the average of four or more common SRG correction models, is examined to determine the best approximation RRS. This best approximation RRS provides an estimate of RRS based on various SRG correction models established using radiative transfer simulations and field investigations. Applying the average RRS provides a measure of the inherent uncertainties or biases that result from a user subjectively choosing any one SRG correction model. Comparisons between inherent and apparent optical property derived observations were used to assess the robustness of the SRG multimodel averaging ap- proach. Correlations among the standard SRG models were completed to determine the degree of association or similarities between the SRG models. Results suggest that the choice of glint models strongly affects derived RRS values and can also influence the blue to green band ratios used for modeling biogeochemical parameters such as for chlorophyll a. The objective here is to present a uniform and traceable methodology for determining ship- borne RRS measurements and its associated errors due to glint correction and to ensure the direct comparability of these measurements in future investigations. We encourage the ocean color community to publish radiometric field measurements with matching and complete metadata in open access repositories.
Resumo:
We correlated Miocene d18O increases at Ocean Drilling Program Site 747 with d18O increases previously identified at North Atlantic Deep Sea Drilling Project Sites 563 and 608. The d18O increases have been directly tied to the Geomagnetic Polarity Time Scale (GPTS) at Site 563 and 608, and thus our correlations at Site 747 provide a second-order correlation to the GPTS. Comparison of the oxygen isotope record at Site 747 with records at Sites 563 and 608 indicates that three as-yet-undescribed global Miocene d18O increases may be recognized and used to define stable isotope zones. The d18O maxima associated with the bases of Zones Mila, Milb, and Mi7 have magnetochronologic age estimates of 21.8, 18.3, and 8.5 Ma, respectively. The correlation of a d18O maximum at 70 mbsf at Site 747 to the base of Miocene isotope Zone Mi3 (13.6 Ma) provides a revised interpretation of four middle Miocene normal polarity intervals observed between 77 and 63 mbsf at Hole 747A. Oxygen isotope stratigraphy indicates that the reversed polarity interval at 70 mbsf, initially interpreted as Chronozone C5AAr, should be C5ABr. Instead of a concatenated Chronozone C5AD-C5AC with distinct Chronozones C5AB, C5AA, and C5A (as in the preliminary interpretation), d18O stratigraphy suggests that these normal polarity intervals are Chronozones C5AD, C5AC, and C5AB, whereas Chronozones C5AA-C5A are concatenated. This interpretation is supported by the d13C correlations. The upper Miocene magnetostratigraphic record at Hole 747A is ambiguous. Two upper Miocene d18O events at Site 747 can be correlated to the oxygen isotope records at Site 563 and 608 using the magnetostratigraphy derived at Hole 747B. Our chronostratigraphic revisions highlight the importance of stable isotope stratigraphy in attaining an integrated stratigraphic framework for the Miocene.
Resumo:
Investigations of bottom sediments from the central and northern parts of the Norwegian Sea including study regions at the Storegga landslide, the Haakon Mosby mud volcano, and Knipovich Ridge were carried out. Concentration of n-alkanes in bottom sediments from these regions ranges from 0.53 to 22.1 µg/g of dry sediments that corresponds to 0.02-1.97% of Corg. Molecular composition of hydrocarbons indicates mixed allochtonous-authochtonous genesis of total organic matter (TOC) formed by hydrobiota and residuals of terrestrial plants. Terrigenous organic mater dominates in bottom sediments. Active redox, microbial and thermolytic processes of organic matter transformation take place in the sedimentary mass. Special character of chromatographic spectra of n-alkane distribution in both low and high-molecular ranges, as well as increased naphtene contents can be interpreted as a sign of oil hydrocarbon generation from maternal organic matter as a result of thermocatalytic reactions within sedimentary mass and their displacement into the upper sedimentary layers. Molecular compositions and concentrations of phenols and lignin were determined in core samples from the Norwegian Sea. Total concentration of phenols in the cores ranges from 8.1 to 101.8 (µg/g of dry sediments that corresponds to 0.15-1.15% of TOC. Lignin concentration was estimated at 21.0-459.0 µg/g of dry sediments (0.59-7.9% of ?org. Phenol compounds of p-hydroxybenzoic, vanillin, syringyl and cinnamyl families as basic components of lignin macromolecules were identified. It was found that sea currents and aerosols are the main contributors of lignin into the abyssal part of the Norwegian Sea.