Investigation of Possible Contamination of Shallow Ground Water by Deeply Injected Liquid Industrial Wastes

The objective of this study was to assess the possible impact of deep well disposal operations, conducted between 1958 and 1974, on the ground water quality in a shallow fresh water aquifer beneath Sarnia, Ontario, Canada. Because of the breakout of formation fluids in Sarnia and Port Huron, Michigan, in the early 1970s, it had been hypothesized that liquid waste from the disposal zone in bedrock had leaked through numerous abandoned oil, gas, and salt wells in the area up to the shallow fresh water aquifer and from there to the surface.
A monitoring well network of 29 5cm (2 inch) diameter piezometers was established in the thin sand and shale aquifer system, which exists between 30 and 70m (100 and 230 feet) below ground surface. In addition, a 300m (1000 foot) deep borehole was drilled and instrumented with a Westbay multilevel casing, which permitted sampling of the disposal zone.
Ground water samples from the shallow monitoring wells and the Westbay multilevel casing were analyzed for volatiles by GC/MS. Those volatile aromatics that were conspicuously present in the deep disposal zone, e.g., ethyl toluenes and trimethyl benzene, were not detected in the shallow monitoring wells. Thus, if contaminants from the disposal zone did indeed migrate to the shallow aquifer, contamination was not widespread and probably consisted mostly of displaced chloride-rich formation waters.     

Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry

With the objective of investigating the windwind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9 III+B1 III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50° i 70°.     

A finite difference method for earthquake sequences in poroelastic solids

Induced seismicity (earthquakes caused by injection or extraction of fluids in Earth’s subsurface) is a major, new hazard in the USA, the Netherlands, and other countries, with vast economic consequences if not properly managed. Addressing this problem requires development of predictive simulations of how fluid-saturated solids containing frictional faults respond to fluid injection/extraction. Here, we present a finite difference method for 2D linear poroelasticity with rate-and-state friction faults, accounting for spatially variable properties. Semi-discrete stability and accuracy are proven using the summation-by-parts, simultaneous-approximation-term (SBP-SAT) framework for discretization and boundary condition enforcement. Convergence rates are verified using the method of manufactured solutions and comparison to the analytical solution to Mandel’s problem. The method is then applied to study fault slip triggered by fluid injection and diffusion through high-permeability fault damage zones. We demonstrate that in response to the same, gradual forcing, fault slip can occur in either an unstable manner, as short-duration earthquakes that radiate seismic waves, or as stable, aseismic, slow slip that accumulates over much longer time scales. Finally, we use these simulation results to discuss the role of frictional and elastic properties in determining the stability and nature of slip.     

Late Silurian (Ludlow–Přídolí) microfossils and sedimentation in the Welsh Basin near Clun,Shropshire

The base of the Clun Forest Formation at Clun, Shropshire, has previously been taken to correlate with the base of the Downton Castle Sandstone Formation (Přídolí Series, upper Silurian) on the basis of brachiopod, bivalve, gastropod and ostracod faunas. The detailed distribution of microfossils (acritarchs, chitinozoans, conodonts and ostracods) is documented at Nantyrhynau Quarry, Clun, Shropshire, to test this correlation. Three new species of chitinozoans, Eisenackitina clunensis, Eisenackitina kerria and Angochitina paucispinosa, are described from the quarry. Macrofossil and ostracod distributions suggest that the correlation is correct. However, a typical Ludlow acritarch flora is present throughout the section and suggests that the basal part of the Clun Forest Formation is Ludlow in age. The mixture of characteristic Ludlow and Přídolí microfossils at Nantyrhynau Quarry may be the result of differing environmental conditions between the Ludlow (shelf) and Clun (basinal) areas at this time. Alternatively, the strata exposed at Nantyrhynau Quarry may represent a period towards the end of the Ludlow Series when there are no strata represented in corresponding shelf sections due to non-deposition or erosion. © 1997 John Wiley & Sons, Ltd.     

Crabs,leeches and trypanosomes: an unholy trinity?

The red king crab Paralithodes camtschaticus was deliberately introduced to the Barents Sea in the 1960s and 1970s from its native area in the North Pacific. The carapace of these crabs is a favoured substrate for the leech Johanssonia arctica to deposit its eggs, and the leech is a vector for a trypanosome blood parasite of marine fish, including cod. We examined cod for trypanosome infections during annual cruises along the coast of Finnmark in North Norway over three successive years from stations along a gradient of over 1000 km. In every year the level of trypanosome infection in cod was significantly highest in the area with the greatest density of king crabs. We propose the hypothesis that the burgeoning population of red king crabs in this area is indirectly responsible for increased transmission of trypanosomes to cod by promoting an increase in the population of the leech vector.     

Are increased nutrient inputs responsible for more outbreaks of crown-of-thorns starfish? An appraisal of the evidence

The cause(s) of primary outbreaks of the coral-eating crown-of-thorns starfish (Acanthaster planci) are still subject to scientific controversy. The possibility of primary outbreaks being linked to terrestrial runoff has been postulated a number of times, suggesting that enhanced nutrient supply is critical for enhanced A. planci larval development. This paper examines the evidence for such a cause, focussing particularly on the Great Barrier Reef (GBR). Nutrient discharges from rivers have increased at least four-fold in the central GBR over the last century, and concentrations of large phyto-plankton (>2 microm) of the inshore central GBR shelf in the wet season when A. planci larvae develop, is double that of other places and times. Larval development, growth and survival increase almost ten-fold with doubled concentrations of large phyto-plankton. This and other lines of evidence suggest that frequent A. planci outbreaks on the GBR may indeed be a result of increased nutrient delivery from the land.     

The PROWQM physical–biological model with benthic–pelagic coupling applied to the northern North Sea

PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59°20′N 1°00′E) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN's benthic and pelagic biology.The physical sub-model of PROWQM implicitly solves turbulence closure equations forced by climatological, or realistic high-frequency, meteorological and tidal data. The pelagic biological sub-model 2MPPD includes a ‘diatomy’ microplankton (mp1) and a ‘flagellatey’ (or microbial loop) microplankton (mp2), the cycling of silicon and nitrogen, slow-sinking detritus, and fast-sinking phytodetritus. Phytodetritus is formed by shear-driven aggregation of particulate material, using a simple algorithm for bulk processes that is derived by considering the interactions of single cells. The microplankton compartments include heterotrophic bacteria and protozoa as well as phytoplankton, and most microplankton rates are specified with the aid of a ‘heterotroph fraction’ parameter, which was 0.125 for mp1 and 0.6 for mp2. The microbiological system is closed by mesozooplankton grazing pressures imposed as time varying series determined from observed zooplankton abundance. The benthic boundary sub-model includes a superficial fluff layer and a nutrient element reservoir in the consolidated sediment. Particulate material in the fluff layer can be resuspended (in response to bed stress by near-bed flows), mineralised or carried by bioturbation into the underlying, consolidated, sediment, where it is mineralised and its nutrients returned to the water-column at rates mainly dependent on (implicit) macrobenthic pumping. Benthic denitrification can occur when mineralisation rates exceed oxygen supply.Verification of the PROWQM numerical implementation used test cases and checks for nutrient element conservation. Simulations with realistic forcing, for a range of parameter values, were compared with historic observations in the NOWESP data set and during FLEX76, and with those made during the PROVESS cruises in autumn 1998. PROWQM provided a good simulation of the seasonal succession from a diatom-dominated spring bloom to summer dominance by small flagellates. The simulations included sedimentation of organic matter from the spring bloom, and qualitatively realistic behaviour of the fluff layer, but decay rates were too slow and there was almost no denitrification. The simulated surface mixed layer was too shallow during the summer. Simulated annual net microplankton primary production was in between 59 and 91 g C m⁻² y⁻¹. A large proportion of mineralisation, 28–47% of nitrogen and 40–67% of silicon mineralisation, took place as a result of the decay of sinking and resuspended detritus whilst in the water column.PROWQM is discussed in relation to other models that have been used to simulate this part of the North Sea, in particular the simpler ECOHAM1 and the more complex ERSEM, and in relation to PROWQM's evolution from COHERENS.     

Sedimentary C/S relationships in a large tropical estuary: Evidence for refractory carbon inputs from mangroves

Mud islands in the Fly River estuary were deposited under dominantly brackish conditions. Changes in C/S ratio with depth in sediment cores reflect geomorphic development of islands and/or changes in location of river channels. An unusual feature of the C/S relationships is positive carbon-axis intercepts, indicating the presence of an organic phase that is resistant to decomposition. Nonzero intercepts mean that the slope of the C/S plot, and not individual C/S values, must be used to determine paleoenvironments. Moreover, a nonzero intercept may be useful for indicating proximity to a source of refractory carbon, such as mangroves.