On the sulphur chemistry of a super-anoxic fjord, Framvaren, South Norway

The concentrations of total carbonate (C_t), sulphate, sulphide, thiols and oxygen, the ratio between the stable sulphur isotopes ³⁴S and ³²S in sulphate and sulphide, and the density (used to calculate salinity) were determined on samples from the water column of Framvaren, a superanoxic fjord in southern Norway. From a depth of 18m (the oxic-anoxic boundary) the initial sulphate concentration, ([SO₄]_init), as calculated from salinity, is significantly higher than the sum of the measured sulphur species. This is attributed to a loss of sulphur from the water column. The amount of total carbonate produced, corrected for the initial concentration (C_t - 2.4 Sal/35) is found to be proportional to the amount of sulphate consumed, ([SO₄]_init - [SO₄]), according to the following relation C_t- 2.4 Sal/35 = 1.84 ([SO₄]_init - [SO₄]). Isotopic fractionation caused by bacterial sulphate reduction in the anoxic part of the water column produces sulphide with a δ³⁴S 40‰ lower than the δ³⁴S for sulphate at corresponding depths. The isotopic fractionation also results in δ³⁴S value for the remaining sulphate at depths below 80 m being considerably higher than the mean value for ocean water, which is close to + 20‰. The δ³⁴S values for sulphate at depths between 10 and 50 m were lower than + 20‰ which indicates oxidation of sulphide, which follows upon diffusion of sulphide from deeper parts of the water column and inflow of oxygenated seawater over the sill into the anoxic water of the fjord. A conclusive scenario of the Framvaren sulphur chemistry is presented.     

Formation of framboidal iron sulfide in the water of a permanently anoxic fjord - Framvaren, South Norway

Framvaren, a permanently anoxic fjord on the southernmost point of Norway, is geomorphologically the result of glaciation and deglaciation. A barrier of glaciofluvial deposit was formed between the open sea and the landlocked water. Due to the isostatic uplift during the deglaciation period, the landlocked water was isolated from the sea and became a meromictic lake. Around 1850, a channel was cut in the barrier and the lake became a fjord with a sill depth of 2.5m and a basin depth of 180 m. The fjord is now permanently anoxic below 18 m depth. The tidal amplitude is close to 10 cm. Only 100 people live in the catchment area of Framvaren, hence it may be considered as a natural pristine laboratory, ideal for study by marine scientists interested in anoxic systems.     

Chromium(III) — chromium(VI) interconversions in seawater

The stable form of dissolved chromium in oxygenated seawater is Cr(VI). But Cr(III)-species are also present at an analytically significant level. It is shown that Cr(III) is oxidized only slowly by dissolved oxygen, and that manganese oxide is a strong catalyst for such oxidation. However, the low oceanic concentration of suspended MnO₂ impedes the conclusion that the former process is quantitatively less important than the latter one. The distribution of dissolved chromium among Cr(VI)- and Cr(III)-species is probably kinetically controlled.     

The distribution and biomass of phytoplankton and phototrophic bacteria in Framvaren, a permanently anoxic fjord in Norway

The vertical distribution and biomass of phytoplankton and phototrophic bacteria in the permanently anoxic fjord, Framvaren in southern Norway, are described. The distribution of algal and bacterial pigments was studied at different seasons in the period from May 1980 to February 1985. The standing crop of phytoplankton was low in the upper part of the euphotic zone, but increased near the O₂/H₂S interface. An algal plate and a dense plate of phototrophic bacteria, measured as chlorophyll fluorescence and scattering, were detected near the interface. These plates of phototrophic micro-organisms were found to be photosynthetically active. Sharp concentration peaks near the interface were also found for the active biomass measured as adenosine triphosphate (ATP).     

The solubility of calcite in seawater at atmospheric pressure and 35%permil; salinity

The apparent (stoichiometric) solubility product of calcite in artificial seawater of salinity 35‰ was measured by a saturometer technique. The value of the apparent solubility product was found to be (4·59 ± 0·05) × 10⁻⁷ moles/(kilogram of seawater)² at 25°C with a temperature coefficient of −0·0108 × 10⁻⁷/°C between 2 and 25°C. These values are significantly smaller than those found by MacIntyre (1965) and other workers. The effect of these results on the saturation of the oceans with respect to calcite is examined.     

Cycling of dissolved and particulate nitrogen and carbon in the Framvaren Fjord, Norway: stable isotopic variations

The reaction pathways of nitrogen and carbon in the Framvaren Fjord (Norway) were studied through stable isotope analysis (δ¹⁵N and δ¹³C) of dissolved inorganic and particulate organic matter (POM). The variations in the isotopic compositions of the various C and N pools within the water column were use to evaluate the historical deposition of material to the sediments. The high δ¹⁵N-NH₄⁺ at the O₂/H₂S interface, as a consequence of microbial uptake between 19 and 25 m, results in extremely depleted δ¹⁵N-particulate nitrogen (PN) of approximately 1‰ within the particulate maximum at approximately 19 m. The carbon isotopic distribution of dissolved inorganic carbon (DIC) and particulate organic carbon (POC) within the interface suggests that the distinct microbial flora (Chromatium sp. and Chlorobium sp.) fractionate inorganic carbon to different degrees. The extremely light δ¹³C-POC within the interface (−31‰) appears to be a result of carbon uptake by Chromatium sp. while δ¹³C-POC of −12‰ is more indicative of Chlorobium sp. Nitrogen isotopic mass balance calculations suggested that approximately 75% of the material sinking to the sediments was derived from the dense particulate maximum between 19 and 25 m. The sediment distribution of nitrogen isotopes varied from 2‰ at the surface to approximately 6‰ at 30 cm. The nitrogen isotopic variations with depth may be an indicator of the depth or position of the O₂/H₂S interface in the fjord. Low sediment δ¹⁵N indicated that the interface was within the photic zone of the water column, while more enriched values suggested that the interface was lower in the water column potentially allowing for less fractionation during biological incorporation of dissolved inorganic nitrogen. Results indicate that the dense layers of photo-autotrophic bacteria in the upper water column impart unique carbon and nitrogen isotopic signals that help follow processes within the water column and deposition to the sediments.     

The effect of pressure on the chemical potentials of seawater components,on ionic species in seawater,and on calcite saturation levels

The activities of most of the major seawater components at 1,001 bars have been estimated, and values for the ions deduced. Equations giving the effect of pressure on the activities of ionic species in seawater ($\text{S = 35‰}$) have been developed. The species covered are: NaSO₄^?, MgSO₄⁰, CaSO₄⁰, H⁺, the free base (NH₃), the HCO₃^?/CO₃² activity ratio and the ion activity product of calcium carbonate. Comparison of the latter with the “ideal” solubility of calcite (pure solid in equilibrium with a mixed electrolyte solution) indicates a degree of saturation compatible with the trends indicated by in situ measurements.     

The solubility of calcite — probably containing magnesium — in seawater

The apparent solubility product of calcite was measured by saturometry as a function of temperature and salinity. Simplified equations for the carbonic-acid dissociation constants of Mehrbach et al., 1973 (Limnol. Oceanogr., 18: 897–907) have been derived from their experimental data and used to calculate apparent solubility product, K′_sp, K′_sp at 25°C and 35‰ salinity, was found to be K′_sp = 4.70 × 10^?7(mol²kgseawater^?2) An equation was fitted to the experimental data, resulting in pK′_sp = 6.5795 ? 3.7159 × 10⁵(TS) + 0.91056(T/S) ? 22.110(1.0/S)The mean activity coefficients, $\text{γ±}\text{CaCO}{}_3$, were calculated at various temperatures and salinities, using the thermodynamic solubility product of Jacobson and Langmuir, 1974 (Geochim. Cosmochim. Acta, 38: 301–318) and the apparent solubility products quoted in their paper. The change in K′_sp at each salinity, as a function of temperature, was used to calculate the apparent enthalpy of dissociation for calcite, ΔH′, and the extrapolated value of ΔH⁰ was in good agreement with that of Jacobson and Langmuir. Finally, this work was used to calculate saturation profiles for oceanic stations and as a basis for comment of the accuracy of in-situ saturometry, as well as the applicability of in-situ K′_sp pressure corrections.     

近平衡状态海水中方解石和文石沉淀速率及动力学研究

利用"freedrift"开放反应系统,研究人工海水中近沉淀平衡状态时二氧化碳分压(p(CO2))的变化对方解石、文石沉淀速率及其动力学方程的影响.反应在恒定的温度(25.0℃±0.2℃)、p(CO2)环境下进行,通过实验得到了不同p(CO2)环境下,方解石和丈石的沉淀速率及动力学方程.研究发现:(1)晶体类型和碳酸盐...     

Petroleum retention in the Mandal Formation,Central Graben,Norway

Upper Jurassic organic matter-rich, marine shales of the Mandal Formation have charged major petroleum accumulations in the North Sea Central Graben including the giant Ekofisk field which straddles the graben axis. Recent exploration of marginal basin positions such as the Mandal High area or the Søgne Basin has been less successful, raising the question as to whether charging is an issue, possibly related to high thermal stability of the source organic matter or delayed expulsion from source to carrier.The Mandal Formation is in part a very prolific source rock containing mainly Type II organic matter with <12 wt.-% TOC and HI < 645 mg HC/g TOC but Type III-influenced organofacies are also present. The formation is therefore to varying degrees heterogeneous. Here we show, using geochemical mass balance modelling, that the petroleum expulsion efficiency of the Mandal Formation is relatively low as compared to the Upper Jurassic Draupne Formation, the major source rock in the Viking Graben system. Using maturity series of different initial source quality from structurally distinct regions and encompassing depositional environments from proximal to distal facies, we have examined the relationship between free hydrocarbon retention and organic matter structure. The aromaticity of the original and matured petroleum precursors in the Mandal source rock plays a major role in its gas retention capacity as cross-linked monoaromatic rings act on the outer surface of kerogen as sorptive sites. However, oil retention is a function of both kerogen and involatile bitumen compositions. Slight variations in total petroleum retention capacities within the same kerogen yields suggest that texture of organic matter (e.g. organic porosity) could play a role as well.     

INMARSAT — satellite communications

The International Maritime Satellite Organization (INMARSAT) has come into being as a result of conferences by the Inter-governmental Maritime Consultative Organisation (IMCO). Its administration has been set up in London, and the organization has called for tenders for the satellites and ground stations required, and as an interim measure is arranging to use a share of the facilities of existing satellite systems. Its aim is to improve telecommunications facilities for the world's shipping and thus to reduce risks to life and property at sea, increase the efficiency of ship management, and to provide a satellite service, owned by the participating governments, that has been long in demand.     

Pollution — a French perspective

A summary of the various forms of pollution control discussed at an international Anti-Pollution Course held at the French Merchant Marine School in Marseilles on 13–25 June 1977.     

The distributions of uranium, radium and thorium isotopes in two anoxic fjords: Framvaren Fjord (Norway) and Saanich Inlet (British Columbia)

Depth profiles of the naturally-occurring radionuclides ²³⁸U, ²³⁴U, ²²⁶Ra, ²²⁸Ra and ²²⁸Th were obtained in two diverse anoxic marine environments; the permanently anoxic Framvaren Fjord in southern Norway and the intermittently anoxic Saanich Inlet in British Columbia. Concentrations of total H₂S were over three orders of magnitude greater in the anoxic bottom waters of Framvaren Fjord compared to those in Saanich Inlet.In Framvaren Fjord, the O₂/H₂S interface was located at 17 m. While dissolved ²³⁸U behaved conservatively throughout the oxic and anoxic water columns, concentrations based on the ²³⁸U/salinity ratio in oxic oceanic waters were almost 30% lower. Dissolved ²²⁶Ra displayed a sharp maximum just below the O₂/H₂S interface, coinciding with dissolved Mn (II) and Fe (II) maxima in this zone. It is suggested that reductive dissolution of Fe-Mn oxyhydroxides remobilizes ²²⁶Ra in this region.In Saanich Inlet, the O₂/H₂S interface was located at 175 m. Dissolved ²³⁸U displayed a strongly nonconservative distribution. The depth profiles of dissolved ²²⁶Ra and ²²⁸Th correlated well with the distribution of dissolved Mn (II) in the suboxic waters above the O₂/H₂S interface, suggesting that reduction of particulate Mn regulates the behavior of ²²⁶Ra and ²²⁸Th in this region.Removal residence times for dissolved ²²⁸Th in the surface oxic waters of both systems are longer than those generally reported for particle-reactive radionuclides in coastal marine environments. In the anoxic waters of Framvaren Fjord and Saanich Inlet, however, the dissolved ²²⁸Th removal residence times are quite similar to values reported for dissolved ²¹⁰Pb in the anoxic waters of the Cariaco Trench and the Orca Basin. This implies that the geochemistries of Th and Pb may be similar in anoxic marine waters.     

Latest Caledonian to Present tectonomorphological development of southern Norway

The regional resultant stress field of the northeastern North Atlantic has shifted significantly throughout the Phanerozoic. In Fennoscandian parts of the Caledonian orogen, mountain building, which was characterized by NW-SE contraction (reference to present North), was followed by a collapse with transport both parallel and transverse to the mountain chain. The Late Palaeozoic – Mesozoic saw several stages of E-W to NW-SE extension, varying in time and position. Local episodes of inversion are traceable in some cases, particularly in connection with deep-seated and long-lived zones of weakness. The Cenozoic has to a larger degree been affected by compression, including folding and basin inversion. Again some of the more pronounced effects of local inversion are related to pre-existing fault systems. Neogene uplift of the western mountainous area in Scandinavia can be unravelled by potential field study, AFT data and reflection seismic sections. Assuming that the region is close to isostatic equilibrium, the uplifted areas must be supported at depth by substantial volumes of low-density material within the crust or the mantle, close to the crust/mantle interface or close to the lithosphere/asthenosphere interfaces.     

Local community training and education in southern Tanzania—a case study

Local coastal communities are highly dependent upon the marine environment not only for protein but also as a primary source of income. In addition, there are growing economic opportunities offered within the coastal zone. As populations increase in these areas there is an increasing demand on coastal resources. This in turn requires effective management initiatives at regional, national and local levels.The Marine Education and Training Programme in Mtwara, southern Tanzania was a small scale capacity building project that incorporated two elements; a primary schools field day education programme and a marine coastal resources course for fishermen and women from the Mtwara District. The programme ran for a period of 1 year and during that time 14 schools, 198 children, 34 fishermen, 2 women and 14 villages participated. Results from preliminary evaluation indicated that such education is not only welcome by the local government offices, teachers, village chairmen and fishermen as an expansion of the knowledge base, but is also an important and valuable stepping stone for the local communities to become active in issues regarding the management of coastal resources.     

The interaction of manganese(II) with the surface of calcite in dilute solutions and seawater

The interaction of Mn²⁺ with the surface of calcite in aqueous solutions is complex. In dilute solutions the Mn²⁺ is rapidly absorbed, MnCO3₃ nucleates on the calcite surface and then grows by a first order reaction with respect to the initial Mn²⁺ concentration. At higher ionic strengths in NaCl solutions, the rate of these processes is slower, but the same general pattern persists. In solutions containing Mg²⁺, at the concentration of seawater and in seawater, the nucleation phase of the uptake process does not appear to occur. The long-term uptake rate of Mn²⁺ on the surface of calcite in seawater is first order with respect to the dissolved Mn²⁺ concentration. The rate constant is over three orders of magnitude smaller than that found in dilute Mg²⁺-free solutions. A probable explanation for the slower growth rate in seawater is that MnCO₃ is not nucleated on the calcite surface due to the presence of high Mg²⁺ concentrations. The Mg²⁺, through site competition, prevents enough Mn²⁺ from being adsorbed to reach a critical concentration for MnCO₃ nucleation. This behavior is similar to that found for orthophosphate with calcite surfaces in dilute solutions and seawater. It indicates that rhodochrosite cannot nucleate in carbonate-rich recent sediments unless the Mg²⁺ concentration is lowered below that of seawater.Measurements of the solubility of rhodochrosite in seawater gave results from an undersaturation approach to equilibrium in excellent agreement with those found in previous studies in dilute solutions. When equilibrium was approached from supersaturation, approximately fifty times more calcium was precipitated than Mn²⁺. The measured solubility was over twice that determined from undersaturation. It is possible that a Mn—calcite containing 25 to 30 mol% MnCO₃ formed on the rhodochrosite from the supersaturated solutions. Consequently, it is doubtful that pure rhodochrosite controls the concentration of Mn²⁺ even in calcium carbonate-poor marine environments.