CaCO3, organic carbon, and nitrogen at DSDP Hole 93-603B

Contents of organic carbon and carbonate carbon were determined on the same set of Cretaceous samples from DSDP Hole 603B in three different laboratories in order to assess the degree of comparability of organic carbon and carbonate values obtained by different labs using the same or different methods. We report the results of analyses for organic carbon using two different CHN analyzers, LECO, and Rock-Eval II and for carbonate carbon by CHN (total C minus C after acidification), the carbonate bomb technique, and CaCO3 calculated on the basis of total calcium obtained from X-ray fluorescence and induction-coupled plasma techniques. In addition, total nitrogen was obtained by two different labs using a CHN analyzer, but different bases for calculation were used. The various techniques for organic carbon analysis yielded comparable results, with the exception of those obtained by one of the CHN analyses of acid-treated samples. The calculation of organic carbon values and comparison on a whole-rock basis is very sensitive to errors in determination of carbonate contents, and this factor explains most, but not all, of the disparities between the data sets. The carbonate bomb technique gives CaCO3 values that correspond well with those calculated from total calcium concentrations (XRF and ICP analyses), whereas the CaCO3 calculated from CHN total carbon minus acid-soluble carbon consistently overestimated CaCO3. Total nitrogen and C/N results from the two different CHN analyses are not comparable and are subject to more error than the factor related to error in estimation of CaCO3.

(Table 1) Carbon and carbonate at DSDP Leg 71 Holes

Leg 71 sediments were analyzed for total carbon and acid-insoluble (organic) carbon, using the Leco WR-12 analyzer, according to the standard technique outlined below. The 3 cm**3 sediment samples were first dried and ground into a homogeneous powder. The ground sediment was redried at 105 to 110°C, and two samples, a 0.1 g and a 0.5 g sample, were weighed into Leco clay crucibles. The 0.5 g sample was acidified with 10% hydrochloric acid and washed with distilled water. The sample was then dried and analyzed for acid-insoluble carbon. The 0.1 g sample was analyzed for total carbon without further treatment. If the sample contained less that 10% CaCO3, an additional 0.5 g sample was analyzed for greater accuracy. The calcium carbonate percentages were calculated as follows: (% total C - % organic C) x 8.33 = % CaCO3. Although other carbonates may be present, all acid-soluble carbon was calculated as calcium carbonate.

Chemical composition and rate of accumulation of manganese nodules in the western North Pacific

The major and some of the minor constituents and the rate of accumulation of manganese nodules in the western North Pacific were determined. Manganese concentration in the nodules ranged from 20 to 30 per cent in the acid soluble fraction. As to the rare earth concentration, enrichment of cerium was observed in the manganese nodule as compared with that in shales or sea water. Thorium to uranium ratio in the nodule ranged from 9.4 to 14.3, which was very much higher than that in sea water. From the distribution of excess ionium, excess protactinium and Io/Th ratio, a rate of accumulation of 7 mm per million years was obtained with the surface layer of several mm in thickness of the JEDS-4-E4 nodule.

Biogeochemical and physico-chemical characteristics in the gulf of Trieste, Italy

In this paper we investigated, for two years and with a bi-monthly frequency, how physical, chemical, and biological processes affect the marine carbonate system in a coastal area characterized by high alkalinity riverine discharge (Gulf of Trieste, northern Adriatic Sea, Mediterranean Sea).

Lignin, phenols, and some chemical elements in aerosols and bottom sediments from the Tropical North Atlantic

A study of composition of biomarkers (lignin and phenols) in aerosols and bottom sediments from the Tropical North Atlantic was carried out. It was shown that organic matter of aerosols was mostly composed of products of terrestrial plants (arboreal fibers, pollen, and spores). Biomarker composition in the aerosols and in the bottom sediments was practically similar, which proved delivery of terrigenous organic matter to the ocean via the atmosphere.

n-Alkanes and lignin in bottom sediments of the West European Basin (area of the battleship Bismark wreck site)

Three bottom sediment cores were collected from the top, slope, and foot of a small topographic high located near the West European continental rise within the Porcupine abyssal plain at the battleship Bismark wreck site. Using high-efficient gas chromatography technique we determined content and examined molecular composition of n-alkane fraction of hydrocarbons and phenol compounds of lignin. n-Alkane and phenol concentrations in bottom sediments of all three cores were low both in values per unit mass of sediments and in organic matter composition that is typical for pelagic deposits of the World Ocean. They vary from 0.07 to 2.01 µg/g of dry sediment and from 0.0001 to 0.01% of TOC; phenol ranges are from 1.43 to 11.1 µg/g and from 0.03 to 0.6%. Non-uniform supply of terrigenous matter to the bottom under conditions of changes in sedimentation environment in different geological epochs is the principal reason for significant variations in n-alkane and lignin concentrations with depth in the cores. Lignin and its derivatives make the main contribution to formation of organic matter composition of the region in study. With respect to n-alkane and lignin concentrations organic matter of deposits of the West European Basin is composed of remains of higher plants and of autochtonous organic matter of marine flora; they have mixed terrigenous-autochtonous (terrigenous-planktonogenic) origin.

Lignin and chemical elements in the surface layer of bottom sediments from the Kandalaksha Bay of the White Sea

Chemical composition of the upper layer of sediments (0-1 cm) in the Kolvits and Knazhaya inlets, and also in the deep-water part of the Kandalaksha Bay is considered. It is shown that silts are richer in Fe, TOC, and heavy metals, than sands. The highest concentration of these elements is found in sediments under mixing zones of riverine and sea waters. Correlations of P, Zn, Cd, and Cu with iron are high, and correlations of Pb and Cu with organic carbon are also high. Very high concentration of Pb in the Kandalaksha Bay indicate technogenic pollution of sediments. Lignin makes significant contribution to formation of organic matter in the sediments. Composition of lignin in bottom sediments of the Kandalaksha Bay is defined by composition of lignin in soils and aerosols. Vanillin and syringyl structures prevail in molecular composition of lignin in bottom sediments. Their sources are coniferous vegetations, soils, and mosses. Ratios of certain types of phenol compounds indicate pollution of the upper layer of sediments by technogenic lignin. Lead and copper correlate well with this technogenic lignin.

n-Alkanes and lignin in bottom sediments of the Norwegian Sea

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.

Impacts of groundwater discharge at Myora Springs (North Stradbroke Island, Australia) on the phenolic metabolism of eelgrass, Zostera muelleri, and grazing by the juvenile rabbitfish, Siganus fuscescens

Myora Springs is one of many groundwater discharge sites on North Stradbroke Island (Queensland, Australia). Here spring waters emerge from wetland forests to join Moreton Bay, mixing with seawater over seagrass meadows dominated by eelgrass, Zostera muelleri. We sought to determine how low pH / high CO2 conditions near the spring affect these plants and their interactions with the black rabbitfish (Siganus fuscescens), a co-occurring grazer. In paired-choice feeding trials S. fuscescens preferentially consumed Z. muelleri shoots collected nearest to Myora Springs. Proximity to the spring did not significantly alter the carbon and nitrogen contents of seagrass tissues but did result in the extraordinary loss of soluble phenolics, including Folin-reactive phenolics, condensed tannins, and phenolic acids by ?87%. Conversely, seagrass lignin contents were, in this and related experiments, unaffected or increased, suggesting a shift in secondary metabolism away from the production of soluble, but not insoluble, (poly)phenolics. We suggest that groundwater discharge sites such as Myora Springs, and other sites characterized by low pH, are likely to be popular feeding grounds for seagrass grazers seeking to reduce their exposure to soluble phenolics.