Interstitial water chemistry in the sediments of Saanich Inlet

Measurements of nutrients and trace metals are used to examine the processes controlling their distributions in the interstitial waters of Saanich Inlet. Samples were collected using both in situ and squeezing techniques with excellent agreement. Additional measurements of porosity, organic carbon and sedimentation rate by ²¹⁰Pb are used in conjunction with the nutrient measurements to test the equation for the diagenesis of organic matter in fine-grained, organic-rich and rapidly-accumulating sediments.Organic carbon and sulfate decrease with depth in the sediment whereas ammonia and alkalinity increase. In the zone of sulfate reduction (0–20 cm) the rate constants for sulfate reduction ($\text{k}{}_{\mathrm{s}}$), ammonia production ($\text{k}{}_{\mathrm{N}}$) and organic carbon decomposition ($\text{k}{}_{\mathrm{c}}$) agree within a factor of two. Our calculations indicate, however, that this is fortuitous since the observed decrease in paniculate organic carbon is insufficient to account for the sulfate consumption. Sulfate must also be consumed by reaction with methane diffusing up from the underlying sediments. The rate constant for sulfate reduction using particulate organic carbon is lower than a modelled rate encompassing all organic species, including methane.The rate constant for ammonia production ($\text{k}{}_{\mathrm{N}}$) decreases by an order of magnitude when sulfate is completely depleted and methane production dominates.Thermodynamic calculations suggest that the interstitial waters are saturated or supersaturated with respect to all forms of iron ‘monosulfides’, apatite and rhodochrosite.     

A numerical study of damping

Diagonal damping matrices were computed for three systems which have non-proportional damping matrices. These diagonal damping matrices were computed on three bases, as follows: 1. After normalizing the equations of motion by the modal matrix, the diagonal terms are retained ignoring the non-diagonal terms. 2. Diagonal damping matrix is established by the optimization algorithm which minimizes the mean square error of the frequency response. 3. Diagonal damping is determined from the normalized differential equation by matching the peaks of the coupled and uncoupled system. The frequency responses for the three cases of one of the three systems are presented together with a comparison of the energy dissipation.     

The formation of pyrite from hydrated iron oxide in aqueous solution at 20°C

Experiments are described in which pyrite is synthesized at room temperature and atmospheric pressure from hydrated iron oxides and hydrogen sulphide under conditions similar to those expected in the natural environment. This synthesis differs from earlier work in that oxygen was rigorously excluded from the system and the pH was 5.6. During a later ageing period a reaction appears to take place in which iron monosulphide is converted to pyrite at pH 5.85.

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Zusammenfassung Versuche zur Synthese von Pyrit bei Raumtemperatur unter atmosphärischem Druck, ausgehend von Eisenhydroxiden und Schwefelwasserstoff und somit unter gleichen Verhältnissen, wie in natürlicher Umgebung, werden beschrieben.Die Synthese unterscheidet sich von früheren Arbeiten durch den strengen Ausschluß von Sauerstoff und den pH-Wert von 5.6. In einer darauffolgenden Alterungsperiode scheint eine Reaktion einzusetzen, in der Eisenmonosulfid bei pH 5.85 zu Pyrit umgewandelt wird.

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Published with the approval of the Director; Bureau of Mineral Resources, Geology and Geophysics.     

A note on the historical industrial production of carbon dioxide

The historical record of CO₂ emissions from industrial activity is reexamined. The overall annual growth rate has been about 3.5% but with wide variations due to economic fluctuations. It is unlikely that the total CO₂ production would have been greatly different had the major wars of the Twentieth Century been avoided.     

Sterane distribution of solid bitumen pyrolyzates. Changes with biodegradation of crude oil in the Ouachita Mountains,Oklahoma

Solid bitumens (grahamite and impsonite) of southeastern Oklahoma have been shown to originate from near-surface alteration of crude oil (Curiale, 1981; Curiale and Harrison, 1981). Pyrolysis of these solids has been employed to compare the sterane distribution of geographically proximate oils to that of the bitumens. The ratio of rearranged to regular steranes is higher in the pyrolyzates than in the oils, a finding consistent with a bitumen origin due to biodegradation of oil. The remaining presence of steranes, particularly regular steranes, in the bitumens suggests that sterane occlusion may have occurred prior to or during the alteration process, thus removing tetracyclic compounds from the influence of microbial attack. These data suggest that pyrolysis-$\text{GC}\text{MS}$ offers a viable approach to correlation problems involving solid bitumens.     

Geotechnical properties of lower trench inner-slope sediments

Geotechnical property analyses on sediments recovered by DSDP drilling within select convergent margins were integrated to determine the variability in these properties along the trench inner-slope and to delineate the effects of convergence on these properties. Consolidation states range from very underconsolidated to highly overconsolidated, with preconsolidation pressures exceeding 46,000 kPa in Quaternary sediments. Underconsolidated sediments are attributed to:

1. (1) high sedimentation rates.

2. (2) low sediment permeability relative to the length of the drainage path; (3) laterally applied stresses; and (4) induced pore water pressures resulting from the subduction of pelagic sediments with high water content. Factors contributing to the state of overconsolidation include: (1) tectonically induced overpressures; (2) removal of overburden by mass movement processes.

3. (3) low sediment accumulation rates.

4. (4) age.

Vertical gradients of index properties also vary greatly with the maximum gradient associated with overconsolidated sediments. Values of porosity generally exceed 30% at all margins studied, suggesting this porosity represents the minimum attainable solely by the effects of convergence.Geotechnical property results and site-specific parameters suggest two end members should be considered in the general geotechnical property model for convergent margin sediments. Clastic dominated margins form the basis for the initial geotechnical property model. These margins are characterized by thick trench sediment sequences which are folded and faulted and become progressively more deformed upslope. Convergence rates are low, and no well-developed faults or hrst and graben structures are evident on the downbending oceanic plate. Highly overconsolidated sediments and index property values which change rapidly with depth result from the slow progressive deformation of trench and lower slope sediments. Examples of clastic-dominated margins include the Nankai Trough, Aleutian Trench, and Washington continental margin.Pelagic-dominated margins have significantly different geotechnical properties and site-specific parameters. These margins are characterized by thin clastic trench sediment sequences overlying pelagic sediments on a rapidly converging oceanic plate. Well-developed faults and/or hrst and graben structures are evident on the downbending oceanic plate. Sediment deformation along the trench and lower slope appears limited. These sediments are underconsolidated and index property values change gradually but often irregularly with depth. Japan Trench and Middle America Trench-Guatemala margins are considered pelagic-dominated. Middle America Trench-Mexico appears to represent an intermediate case having characteristics of both margin types.