Influence of submarine fumaroles on the distribution of mercury in the sediment of Kagoshima Bay,Japan

To estimate the influence of mercury emitted from submarine fumaroles, the horizontal and vertical distribution of mercury in sediment of Kagoshima Bay was studied. The fumaroles are located in the northern bay head area, and the sediment samples had been taken from 52 points throughout the bay with a gravity core sampler. The core samples obtained were cut at a thickness of 1–2 cm and used for measurements. The total concentration of mercury in surface sediment in the northern and central areas of the bay was 51–679 μg kg^− 1 (average 199 μg kg^− 1, n = 22) and 23–100 μg kg^− 1 (average 55 μg kg^− 1, n = 30), respectively. The highest value was obtained in the vicinity of the fumaroles. The mercury concentration in sediment near the fumaroles varied with depth, which may reflect the variation in fumarolic activity. A successive extraction method was applied to the speciation of mercury in the sediment. The results showed that sediment taken in the vicinity of submarine fumaroles contained a higher percentage of mercury bound with organic matter.     

Significance of oxides and particulate organic matter in controlling trace metal partitioning in a contaminated estuary

The sediment–water partitioning of radiolabelled Cd, Hg and Zn has been investigated along an estuarine salinity gradient using samples from the Mersey Estuary, UK. Partitioning was studied using untreated particles, and particles that had been extracted using either a reducing agent (NH₂OH.HCl–HOAc) or an oxidising agent (H₂O₂) in order to qualitatively evaluate the relative roles of Fe–Mn oxides and particulate organic matter (POM), respectively, on metal uptake. The extent of Cd partitioning between sediment and water, parameterised in terms of the distribution coefficient, K_D, exhibited a reduction with increasing salinity, regardless of whether or not particles had been digested. However, the magnitude of K_D decreased significantly following either chemical treatment, suggesting that both oxides and organic matter are important sorbents for Cd. The K_D for Hg in the presence of untreated particles increased with increasing salinity, and chemical reduction of the particles enhanced the uptake of Hg and reinforced this trend. Particle oxidation led to a significant reduction in the K_D for Hg, and uptake by the particles decreased with increasing salinity. These observations suggest that POM is considerably more important than Fe–Mn oxides in the removal of aqueous Hg, and that its presence is a prerequisite for enhanced sorption (or salting out) at elevated salinities. The salinity dependence of K_D for Zn displayed characteristics of both Cd (below salinities of about 5) and Hg (at greater salinities). However, the magnitude of K_D for Zn uptake was relatively insensitive to either chemical treatment, suggesting that oxides, POM, and residual phases contribute to the overall sorption of Zn by estuarine particles. Regression analyses of the metal partition data suggest that sorption to oxides and POM is nonadditive, and that the salinity dependence of metal partitioning results mainly from salinity-controlled interactions between metal and organic matter. Sequential extraction of metals bound to untreated and chemically treated particles in the partitioning experiments indicated that the exchangeability or lability of all metals increased on removal of either oxides or POM. This implies that sorption sites of relatively high energy are destroyed (or become less accessible), or sorption sites of relatively low energy are created (or become more accessible) on chemical treatment. These observations support a conceptual model for the particle surface whose integrity and binding properties are only maintained by the coexistence of and interaction between oxides and organic matter.     

Effect on marine sediment nitrogen fluxes caused by organic matter enrichment with varying organic carbon structure and nitrogen content

Enrichments with five types of organic carbon, differing in nitrogen content and type of organic carbon, were made to a marine sediment in order to study effects on nitrogen fluxes. The enrichments used were Ulva lactuca, Ascophyllum nodosum, Zostera marina, Ceratium spp., lignin, and mixtures of U. lactuca and A. nodosum. Fluxes of ammonium, nitrate, and phosphate were measured in short-term (48 h) microcosm experiments, using a carbon enrichment loading similar to that at the sampling site. Changes in microbial community growth and structure due to three types enrichments were also detected using molecular methods in a microcosm experiment run for 4 days to allow for detection at DNA-level.Ammonium fluxes changed from an efflux in the control to an influx for all enrichments apart from U. lactuca. The change was significantly related to the added material's C:N ratio when Ceratium spp. was excluded. All enrichments induced an influx of nitrate suggesting the formation of anoxic micro zones, but there was no relationship with C:N ratio. Instead, the magnitude of the nitrate influx is suggested to be related to the structure of the organic carbon, where enrichments containing a large pool of cellulose and lignin (Z. marina and lignin) gave rise to a lower influx, compared to algal material with more easily degraded organic matter like lipids and starch, which induced the highest influx of nitrate (Ceratium spp., U. lactuca, and A. nodosum). The occurrence of an ammonium influx together with increased nitrate influx and a lower efflux of phosphate in the enrichments suggests a growth of heterotrophic bacteria. This was also confirmed using molecular methods (PCR-DGGE) where the relative abundance of bacterial species in the enrichments increased.The sum of ammonium and nitrate fluxes showed that total nitrogen removal was enhanced in all enrichments compared to the nonenriched control sediment, but in different ways. Ceratium spp. induced the highest removal followed by A. nodosum, U. lactuca, Z. marina, and lastly, by lignin. The same pattern was observed also in a second experiment. These results indicate that easily degradable organic carbon, together with a lower C:N ratio of the added material, will remove nitrogen from the water phase, making the recycling of nitrogen to the overlying water mass smaller.     

Carbon flux in the northwest Mediterranean estimated from microbial production

Spring profiles of microbial production derived from the dark incorporation of tritiated leucine and tritiated thymidine in the northwest Mediterranean show an exponential decline with depth. Assuming this to represent a steady-state balance between microbial respiration and the downward flux of carbon, the downward flux is estimated as (1−/)p/b, where p is the microbial production, their gross growth efficiency and b the coefficient of exponential decline with depth. Summer profiles, ranging over about 3° of latitude and 4° of longitude, were well fitted by a two-component exponential decline, suggesting two distinct microbial substrates. Values of b for the more rapidly declining component varied between 0.01 and 0.06 m⁻¹ according to location. In the case of the slower component, b was estimated as 0.002 m⁻¹, and did not vary significantly over the region. Estimated fluxes of carbon at the surface are 123–335 mg m⁻² d⁻¹ for the fast and 95 mg m⁻² d⁻¹ for the slow component. Below about 200 m, carbon flux is dominated by the slow component. Flux estimates are compatible with flux estimates from sediment traps in the same region. The observed changes between the spring and summer profiles, combined with the horizontal homogeneity of the summer profiles below 200 m, are consistent with a downward transport of about 5–10 m d^–1, implying a significant dispersive component to the observed fluxes.     

广饶盐田有机地球化学的初步研究

样品于1992年采自山东广饶盐场，用气相色谱和气质联用等方法对样品进行有机分析。结果表明，盐田表层上（包括藻席）中存在大量的烷烃和芳烃类生物标志物，低Pr／Ph比值（＜0．25）反映植烷存在于姥鲛烷之前，大量不饱和化合物的存在显示了有机质演化的初始状态，也反映了表层土的氧化还原性质。不同层位样品中烷烃和芳烃的含量变化很大，同一剖面烷烃含量最大变幅为：1.73×10-5（表层藻垫）至4.10×10-5（表层下3．5－8.5cm土样），说明有机质在常温常压下即开始了演化过程。大量常见生物标志物的存在，说明生物有机质的最初演化是比较容易的。研究生物有机质在常压常温条件下的演化，也许对生物标志物的研究和油气的地质成因有重要意义。     

A mechanistic study of the high-temperature oxidation of organic matter in a carbon analyzer

This study examines the mechanism of oxidation of dissolved organic matter (DOM) in a high-temperature combustion (HTC) carbon analyzer. The HTC analyzer, which is commonly used to measure the concentration of dissolved organic carbon (DOC) in seawater, is still largely empirical in its operation, and little information is yet available on the chemical and physical mechanisms responsible for oxidation of DOM. To examine the role of water, which has been hypothesized to be a source of reactive oxidants in HTC analyzers, several experiments were conducted using gaseous hexane samples and several wet/dry carrier gases. Because the quantity of O₂(g) needed to oxidize an injected sample of DOM is quite small, a substantial effort has been made to exclude O₂(g) from the combustion furnace of the HTC instrument. In this modified, “air-tight” instrument, the efficiency of conversion of hexane into CO₂ was greatest in dry O₂ and slightly lower in moist O₂. Hexane was only slightly oxidized in dry N₂, but it was largely converted into CO₂ when moist N₂ was used as the carrier gas. These experiments confirm that water provides reactive oxidizing species (perhaps hydroxyl radical) that rapidly convert hexane into CO₂ in the combustion tube of a carbon analyzer. Additional experiments with aqueous solutions of potassium hydrogen phthalate and a variety of carrier gases support this basic hypothesis.     

Tracing the inputs and fate of marine and terrigenous organic matter in Arctic Ocean sediments: A multivariate analysis of lipid biomarkers

An understanding of the carbon cycle within arctic sediments requires discrimination between the terrigenous and marine components of organic carbon, insight into the removal mechanisms for labile carbon during burial and appreciation of shelf-to-basin processes. Using a large data set of multiple molecular organic markers (alkanes, alkanols, sterols, saturated and unsaturated fatty acids, dicarboxylic acids), we apply (1) principal components analysis (PCA) to obtain a robust comparison of biomarker compositions in Arctic Ocean sediments, (2) geometric mean (GM) linear regression of the PCA variables to estimate the relative contributions of labile/marine and stable/terrigenous sources to each biomarker and (3) the slope of the GM regression of each biomarker with TOC to provide a novel measure of the removal rate of each biomarker relative to phytol. The PCA- and TOC-based indices generally increase together: biomarkers with very high TOC-based removal rates such as the saturated and unsaturated n-alkanoic acids generally have a high labile/marine content from PCA, while the sterols have low removal rates, but exhibit a range of labile/marine content values and the n-alkanes and n-alkanols have low values for both. A dominant feature of all PCA models examined is a progressive decrease in the autochthonous/marine biomarkers with each increase in sediment core depth, which points to a universal diagenetic alteration of organic carbon with depth in the cores. The PCA model also displays a shelf to basin trend that is non-diagenetic and implies the ongoing (centuries or more) delivery of long-chain n-alkanes, n-alcohols and n-alkanoic acids in a matrix that is pre-formed and well-preserved within the sediments. Terrigenous biomarker distributions within the PCA model suggest that atmospheric transport of plant waxes in aerosols and the water borne transport of very fine plant macerals likely have significant roles in the export of these vascular plant biomarkers to the basins. Biomarker ratios and profiles of the PCA-based labile/marine content with core depth indicate that the PCA model is more strongly influenced by the biomarker lability than the marine content, while increases in the marine content are largely responsible for the shifts in composition for near-surface core sections.     

The role of microorganisms on the mineralogical and geochemical characteristics of the Parnassos-Ghiona bauxite deposits,Greece

The Parnassos-Ghiona bauxite deposits of Greece are hosted within carbonate rocks and have been formed during different geological ages. The most economically important deposits occur in the B3 bauxite horizon, which is developed over long distance as a continuous layer of 1–10 m in thickness, within Cretaceous limestones. Due to intense tectonics, a significant (approximately 30 vol.%) bauxite ores along and near their contact with faults show a brittle deformation and change in the color from red to black-gray, in a distance of tens of meter. Commonly gray to whitish bauxites are aluminum-enriched (> 65 wt.% Al₂O₃) and iron depleted.     

Potential source rocks, organic geochemistry and thermal maturation in the southern depocenter (Kipourio–Grevena) of the Mesohellenic Basin, central Greece

The study area is the southern depocenter (depth > 4200 m) of the Mesohellenic Basin which extends between Kipourio and Grevena, central Greece. The Mesohellenic Basin is a Middle-Tertiary intramontane basin developed within the Hellenide orogen. Previous studies have focused on the depositional environments, configuration and hydrocarbon potential of the basin. In this paper we present additional geochemical and petrographic data from outcrop samples of the basin's southern depocenter, which is considered the most promising area, in terms of hydrocarbon prospectivity. A total number of thirty six samples were analysed: Rock-Eval pyrolysis, maceral analysis, vitrinite reflectance and thermal alteration index, bitumens extraction, liquid chromatography, and GC-MS. The samples were collected from deltaic deposits and submarine fan sediments of Late Eocene to Late Oligocene age. The TOC values of the analysed samples range between rich and very rich and the organic matter consists mainly of type III kerogen and the organic matter consider to be predominately gas prone. The thermal maturity assessed from T_max and vitrinite reflectance shows an immature stage of the organic matter along with the presence of layers having reached the very early mature stage. Vitrinite reflectance measurements and maturity calculations (applying the Lopatin modeling), reveal that the lower part of the depocenter sediments falls within the ‘oil window’. The extractable organic matter (EOM) (mg bitumens/g TOC) indicate the existence of samples (from deltaic deposits) with high ratio of transformation (EOM) (> 100 mg bitumen/g TOC). The GC and GC-MS analyses of the biomarkers indicate mainly the occurrence of terrestrial organic matter reflecting oxidizing conditions and both immature and very early mature stages. The results of the Rock-Eval pyrolysis and the distribution of the isoprenoids support the assumption of the input of an organic matter mixture.     

Comparative studies of organic matter petrography of the late palaeozoic black shales from Southwestern Poland

There are at least two sapropelic units associated with Late Palaeozoic black shales in Central Europe. The older unit, of Late Carboniferous age, is the lower part of the Anthracosia Shales in the Intrasudetic Basin, and the younger one is the well-known Zechstein Kupferschiefer in both the Foresudetic Monocline and the Northsudetic Basin. The first unit is of lacustrine origin, while the second one represents deposition in a shallow marine depositional environment. Both units contain high amounts of organic matter, thus being typical black shales.The organic matter dispersed in these shales was studied petrographically. In general, the vitrinite reflectance of the shales studied indicates variable, but moderate organic matter maturity (0.68–1.25%), equivalent to the oil window. Detailed microscopic studies of the organic material dispersed in the lower unit of the Anthracosia Shales showed that liptinite, especially alginite is the most abundant component. Secondary altered organic matter, i.e. solid hydrocarbons, rarely occurs. Organic components together with mineral matter constitute a lacustrine sapropelic association, a humic (terrestrial) association and an intermediary association. The character and predominance of alginite and lacustrine sapropelic association are indicative of an open-lacustrine depositional environment. In general, this organic composition is typical of type I kerogen.Microscopic analysis of the Kupferschiefer revealed a mixture of liptinite, vitrinite and inertinite macerals, and other organic components such as amorphous sapropelic mass (ASM) and solid bitumens. The most common organic components are liptinite macerals. Bituminite and alginite predominate, and are diagnostic macerals of this unit. The amount of bituminite locally exceeds 85 vol.%. Other liptinite macerals such as sporinite and liptodetrinite, are present in significantly lower amounts, one exception being ASM, which may be present in higher amounts. Humic constituents (vitrinite and inertinite) are rare, present in small amounts in the Kupferschiefer beds. The organic matter composition points to type II kerogen for this unit.