10 resultados para C-13 Nmr Calculations
em Publishing Network for Geoscientific
Resumo:
Chloroform extracts of water-soluble organic matter collected in the water column from the surface to the bottom were studied by C-13 and H-1 NMR chromatographic mass spectrometry, and phthalate concentrations were determined by capillary gas-liquid chromatography. More than 14 compounds were found including diethyl phthalate, ethyl butyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, phthalates with normal C4-C12 chains, phthalates partially esterified with methanol, and others, at total concentrations up to 0.4 mg/l. Possible reasons for presence of phthalates in oceans, sometimes in high concentrations, are discussed.
Resumo:
The dataset is based on samples taken during October 2008 in the North-Eastern Aegean Sea. NH4 excretion rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for NH4 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). Samples for the NH4 determination were collected in pre-cleaned 50 ml Duran bottles and analysed onboard immediately after collection. Ammonium concentration was measured on a Perkin Elmer Lambda 25 UV/VIS Spectrometer according to the method of Koroleff (1970). PO4 excretion rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for PO4 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). Samples for the determination of PO4 were collected in pre-cleaned 50 ml polyethylene volumetric tubes and analysed on board immediately after collection. PO4 concentration was measured on a Perkin Elmer Lambda 25 UV/VIS Spectrometer following the protocol of Murphy and Riley (1962). O2 consumption rate: Mesozooplankton is collected by vertical tows within the Black sea water body mass layer in the NE Aegean, using a WP-2 200 µm net equipped with a large non-filtering cod-end (10 l). Macrozooplankton organisms are removed using a 2000 µm net. A few unsorted animals (approximately 100) are placed inside 8 bottles of 350 or 650 ml filled with GF/F or 0.2 µm Nucleopore filtered seawater and then on a wheell at dim light and maintaining the in situ temperature. 4 bottles without animals are used as control. After 24hours bottles are opened and water samples taken for O2 chemical analysis. Then the bottle content is filtered on pre-combusted preweighted CF/F filters, which are then dried at 60 C and weighted. Calculations are made as described by Ikeda et al. (2000). For the dissolved O2 determination, the samples were fixed immediately after collection and analysed with the Winkler method as modified by Carpenter (1965a and 1965b). Carbon specific CO2 respiration rate: O2 consumption rate was converted to CO2 production using a RQ value of 0.87 (Mayzaud et al. 2005). Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass. Carbon specific NH4 excretion rate: Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass. Carbon specific PO4 excretion rate: Conversion of mesozooplankton dry weight to carbon was done using the % of carbon content measured in the same station from the SESAME dataset of zooplankton biomass.
Resumo:
The origin of two acoustic sediment units has been studied based on lithological facies, chronology and benthic stable isotope values as well as on foraminifera and clay mineral assemblages in six marine sediment cores from Kveithola, a small trough west of Spitsbergenbanken on the western Barents Sea margin. We have identified four time slices with characteristic sedimentary environments. Before c. 14.2 cal. ka, rhythmically laminated muds indicate extensive sea ice cover in the area. From c. 13.9 to 14.2 cal. ka, muds rich in ice-rafted debris were deposited during the disintegration of grounded ice on Spitsbergenbanken. From c. 10.3 to 13.1 cal. ka, sediments with heterogeneous lithologies suggest a shifting influence of suspension settling and iceberg rafting, probably derived from a decaying Barents Sea Ice Sheet in the inner-fjord and land areas to the north of Kveithola. Holocene deposition was episodic and characterized by the deposition of calcareous sands and shell debris, indicative of strong bottom currents. We speculate that a marked erosional boundary at c. 8.2 cal. ka may have been caused by the Storegga tsunami. Whilst deposition was sparse during the Holocene, Kveithola acted as a sediment trap during the preceding deglaciation. Investigation of the deglacial sediments provides unprecedented details on the dynamics and timing of glacial retreat from Spitsbergenbanken.
Resumo:
Most Cenozoic nannofossil and many foraminiferal zonal boundaries have been accurately determined and magnetostratigraphically calibrated at five Leg 73 boreholes. The numerical ages of the boundaries were computed by assuming a linear seafloor spreading rate and a radiometric age of 66.5 m.y. for the Cretaceous/Tertiary boundary. Alternative magnetostratigraphic ages (given below in parentheses) were obtained by adopting a 63.5 m.y. age for the Cenozoic. Our data confirm previous determinations of the Pleistocene/Pliocene boundary at 1.8 (1.7) m.y. and of the Pliocene/ Miocene boundary at 5.1 (5.0) m.y. The Miocene/Oligocene boundary is placed within Chron C-6C and has a magnetostratigraphic age of 23.8 to 24.0 (22.7 to 22.9) m.y. The Oligocene/Eocene boundary is also very precisely located within Chron C-13-R, with a magnetostratigraphic age of 37.1 to 37.2 (35.5 to 35.6) m.y. The Eocene/Paleocene boundary should be located within an uncored interval of Chron C-24 and have a magnetostratigraphic age of 59.0 (55.4) +/- 0.2 m.y. The general accord of the magnetostratigraphic and radiometric ages supports the hypothesis that the seafloor spreading rate was linear during the Cenozoic. Two possible exceptions are noted: the middle Miocene radiometric ages are a few million years older, and the early Eocene radiometric ages are several million years younger, than the corresponding magnetostratigraphic ages.
Resumo:
A detailed dinoflagellate cyst investigation of the almost continuous Middle Miocene through Pliocene of Ocean Drilling Program Hole 907A in the Iceland Sea has been conducted at 100-kyr resolution. The investigated section is well constrained by magnetostratigraphy, providing for the first time an independent temporal control on a succession of northern high-latitude dinoflagellate cyst bioevents. Based on the highest/lowest occurrences (HO/LO) and highest common occurrence (HCO) of 20 dinoflagellate cyst taxa and one acritarch species, 26 bioevents have been defined and compared with those recorded at selected DSDP, ODP, and IODP sites from the North Atlantic and contiguous seas, and in outcrops and boreholes from the onshore and offshore eastern U.S.A., and the North Sea and Mediterranean basins. Comparisons reveal near-synchronous HOs of the dinoflagellate cysts Batiacasphaera micropapillata (3.8-3.4 Ma, mid-Pliocene) and Reticulatosphaera actinocoronata (4.8-4.2 Ma, Lower Pliocene) across the Nordic Seas and North Atlantic, highlighting their value on a supraregional scale. This probably applies also to Hystrichosphaeropsis obscura (upper Tortonian), when excluding ODP Hole 907A where its sporadic upper stratigraphic range presumably relates to cooling in the early Tortonian. Over a broader time span within the upper Tortonian, the HO of Operculodinium piaseckii likely also permits correlation across the Nordic Seas and North Atlantic, and the HO of Labyrinthodinium truncatum appears useful in the Labrador and Nordic Seas. Biostratigraphic markers useful for regional rather than supraregional correlation are the HOs of Batiacasphaera hirsuta (c. 8.4 Ma, upper Tortonian) and Unipontidinium aquaeductus (c. 13.6-13.9 Ma, upper Langhian), the HCO of the acritarch Decahedrella martinheadii (c. 6.7-6.3 Ma, Messinian), and possibly the LO of Cerebrocysta irregulare sp. nov. (c. 13.8 Ma, uppermost Langhian) across the Nordic Seas. Since Habibacysta tectata, B. micropapillata, R. actinocoronata and D. martinheadii have been observed in the Arctic Ocean, they are potentially useful for high latitude correlations in the polar domain. The LOs of Habibacysta tectata and Unipontidinium aquaeductus suggest a mid- to late Langhian age (15.1-13.7 Ma) for deposits at the base of Hole 907A, thus providing new constraints on the age of basalts at the base of ODP Hole 907A. The stratigraphically important dinoflagellate cysts Cerebrocysta irregulare sp. nov., and Impagidinium elongatum sp. nov. are formally described.
Resumo:
This publication presents results of microbiological and biogeochemical studies in the White Sea. Material was obtained during a series of expeditions in 1999-2002. The studies were carried out in the open part of the White Sea, in the Onega, Dvina and Kandalaksha Bays, as well as in the intertidal zone of the Kandalaksha Bay. Quantitative characteristics of activity of microbial processes in waters and bottom sediments of the White Sea were obtained. The total number of bacteria was equal to 150000-800000 cells/ml, and intensity of dark CO2 assimilation was equal to 0.9-17 µg C/l/day. Bacterial sulfate reduction was equal to 3-150 mg S/m**2/day, and methane formation and oxidation was equal to 13-6840 and 20-14650 µl CH4/m**2/day, respectively. Extremely high values of intensity of all principal microbial processes were found in intertidal sediments rich in organic matter: under decomposing macrophytes, in local pits at the lower intertidal boundary, and in the mouth of a freshwater brook. Average hydrogen sulfide production in highly productive intertidal sediments was 1950-4300 mg S/m**2/day, methane production was 0.5-8.7 ml CH4/m**2/day, and intensity of methane oxidation was up to 17.5 ml CH4/m**2/day. Calculations performed with account for areas occupied by microlandscapes of increased productivity showed that diurnal production of H2S and CH4 per 1 km**2 of the intertidal zone (August) was estimated as 60.8-202 kg S/km**2/day and 192-300 l CH4/km**2/day, respectively.
Resumo:
The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.