Environmental Factors Contributing to the Development and Demise of a Toxic Dinoflagellate (<Emphasis Type="Italic">Karlodinium veneficum</Emphasis>) Bloom in a Shallow,Eutrophic, Lagoonal Estuary

A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes, coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter). By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary.     

A Numerical Simulation of Residual Circulation in Tampa Bay. Part II: Lagrangian Residence Time

Lagrangian retention and flushing are examined by advecting neutrally buoyant point particles within a circulation field generated by a numerical ocean model of Tampa Bay. Large temporal variations in Lagrangian residence time are found under realistic changes in boundary conditions. Two 90-day time periods are examined. The first (P1) is characterized by low freshwater inflow and weak baroclinic circulation. The second (P2) has high freshwater inflow and strong baroclinic circulation. At the beginning of both time periods, 686,400 particles are released uniformly throughout the bay. Issues relating to particle distribution and flushing are examined at three different spatial scales: (1) at the scale of the entire bay, (2) the four major regions within the bay, and (3) at the scale of individual model grid cells. Two simple theoretical models for the particle number over time, N(t), are fit to the particle counts from the ocean model. The theoretical models are shown to represent N(t) reasonably well when considering the entire bay, allowing for straightforward calculation of baywide residence times: 156 days for P1 and 36 days for P2. However, the accuracy of these simple models decreases with decreasing spatial scale. This is likely due to the fact that particles may exit, reenter, or redistribute from one region to another in any sequence. The smaller the domain under consideration, the more this exchange process dominates. Therefore, definitions of residence time need to be modified for “non-local” situations. After choosing a reasonable definition, and removal of the tidal and synoptic signals, the residence times at each grid cell in P1 is found to vary spatially from a few days to 90 days, the limit of the calculation, with an average residence time of 53 days. For P2, the overall spatial pattern is more homogeneous, and the residence times have an average value of 26 days.     

Sediment Organic Carbon in Todos Santos Bay, Baja California, Mexico

Sediment grain size and organic carbon (OC) data collected over the past 50 years, together with δ¹³C values of OC in recently collected samples, were analyzed to improve understanding of sediment OC distribution and abundance in Todos Santos Bay. Sediments in the submarine canyon at the mouth of the bay and in quiet-water locations along the shore are fine grained, high in OC, and have generally low δ¹³C values; sediments in high-energy environments are low in OC and have high δ¹³C values. A bivariate isotopic mixing model indicates that none of the sediments contain >50% terrigenous OC (average ~30%), and that the terrigenous OC content of the sediments is a small proportion of the OC content of local soils. Sediment OC composition is apparently controlled by energy-related sorting and deposition, oxidation of much of the original terrigenous OC, and replacement of some terrigenous OC by marine OC.     

A combined mathematical geophysical model for prediction of pyrite oxidation and pollutant leaching associated with a coal washing waste dump

The waste produced by coal washing process produces many environmental problems. In this study, the pollution problems associated with the waste produced by Alborz Sharghi Coal Washing Plant was investigated by mathematical modeling. The study area is located at 11 km. to Razmjah coal region and 45 km. to Tehran-Mashhad road in the north part od Iran. To achieve the goal, a few samples were taken from different depths at three points on the waste dump in order to investigate pyrite oxidation and pollution generation. The samples were then analysed, using an AA-670 Shimadzu atomic absorption to determine the fraction of pyrite remained within the waste particles. A numerical finite volume model using Phoenics package has been developed to simulate pyrite oxidation and pollution generation from the Alborz Sharghi coal washing waste dump. The pyrite oxidation reaction is described by the shrinking-core model. Gaseous diffusion is the main mechanism for the transport of oxygen through the waste. The results of numerical modelling were compared with the field observations and close agreement was achieved. A simple mathematical model incorporating advection and hydrodynamic dispersion processes was also presented in order to verify the results of geophysical time-laps method showing transportation of the pollutants through the downstream of the waste dump. Both mathematical model and geophysical time-laps method are agreed in the identification of pollutant transport emanated from the waste dump. The results of such investigations can be used for designing an effective environmental management program.     

Geochemistry of magmatic rocks of the Koksharovka alkaline-ultrabasic massif,primorye, and results of trace-element modeling

New geochemical data are presented on the magmatic rocks of the Late Jurassic Koksharovka alkaline-ultrabasic massif, which is associated with deposits of vermiculite, apatite, V-bearing titanomagnetite, and placer isoferroplatinum. The REE geochemistry and strontium, oxygen, and carbon isotopic composition of carbonatites and related ijolites and pyroxenites, together with geological observations, point to the magmatic origin of the Koksharovka carbonatites. The origin of associated magmatic rocks is discussed. Trace element modeling of partial melting of mantle sources was conducted to decipher the genesis of the melts of the Koksharovka carbonatites and host titanite-kaersutite pyroxenites.     

Inversely-Mapped Analytical Solutions for Flow Patterns around and within Inclined Elliptic Inclusions in Fluid-Saturated Rocks

In this paper, an inverse mapping is used to transform the previously-derived analytical solutions from a local elliptical coordinate system into a conventional Cartesian coordinate system. This enables a complete set of exact analytical solutions to be derived rigorously for the pore-fluid velocity, stream function, and excess pore-fluid pressure around and within buried inclined elliptic inclusions in pore-fluid-saturated porous rocks. To maximize the application range of the derived analytical solutions, the focal distance of an ellipse is used to represent the size of the ellipse, while the length ratio of the long axis to the short one is used to represent the geometrical shape of the ellipse. Since the present analytical solutions are expressed in a conventional Cartesian coordinate system, it is convenient to investigate, both qualitatively and quantitatively, the distribution patterns of the pore-fluid flow and excess pressure around and within many different families of buried inclined elliptic inclusions. The major advantage in using the present analytical solution is that they can be conveniently computed in a global Cartesian coordinate system, which is widely used in many scientific and engineering computations. As an application example, the present analytical solutions have been used to investigate how the dip angle of an inclined elliptic inclusion affects the distribution patterns of the pore-fluid flow and excess pore-fluid pressure when the permeability ratio of the elliptic inclusion is of finite but nonzero values.     

On the use of gravity and magnetic anomalies for locating probable areas of metallic mineralization in South Sinai, Egypt

The present study deals with processing and interpreting the potential gravity and magnetic data in order to locate promising sites for metallic mineral occurrences in the basement rocks of South Sinai. Two promising sites were anticipated by combining the geophysical results and the available geological information. Each site was profiled and interpreted to the nearly approximated subsurface feature model, and the geometrical parameters of the expected subsurface structures may form mineralized bodies such as depth, thickness, width, dipping, density contrast, and magnetic susceptibility contrast could be delineated. Detailed ground Very Low Frequency (VLF) and Vertical Magnetic Gradient (VMG) methods were carried out in the site A2, eight VLF and VMG anomalies were determined, and their depths were calculated.     

The gravitational field of topographic-isostatic masses and the hypothesis of mass condensation II-the topographic-isostatic geoid

In Part I we focussed on a convergent representation of the gravitational potential generated bytopographic masses on top of the equipotential surface atMean Sea Level, thegeoid, and by those masses which compensate topography. Topographic masses have also been condensated, namely represented by a single layer. Part II extends the computation of the gravitational field of topographic-isostatic masses by a detailed analysis of itsforce field in terms ofvector-spherical harmonic functions. In addition, the discontinuous mass-condensated topographic gravitational force vector (head force) is given. Once we identify theMoho discontinuity asone interface of isostatically compensated topographical masses, we have computed the topographic potential and the gravitational potential which is generated by isostatically compensated masses atMean Sea Level, the geoid, and illustrated by various figures of geoidal undulations. In comparison to a data oriented global geoid computation ofJ. Engels (1991) the conclusion can be made that the assumption of aconstant crustal mass density, the basic condition for isostatic modeling, does not apply. Insteaddensity variations in the crust, e.g. betweenoceanic and continental crust densities, have to be introduced in order to match the global real geoid and its topographic-isostatic model. The performed analysis documents that thestandard isostatic models based upon aconstant crustal density areunreal.     

LREE distribution in perovskite,apatite and titanite from South West Ugandan xenoliths and kamafugite lavas

Summary In-situ microprobe LREE analyses of perovskite and titanite (La, Ce, Nd), and apatite (La, Ce), from SW Ugandan clinopyroxenite xenoliths and kamafugite lavas indicate that LREE distribution in these minerals is determined by a number of factors related to their different parageneses: In particular LREE content is affected by whether the LREE-bearing minerals have crystallised from metasomatic carbonate or from silicate (i.e. metasomatic or magmatic) melts in the mantle. In this situation LREE partition favours carbonate over silicate melts. Distribution of LREE in perovskite and apatite crystallised from magmatic mantle melts or mantle-derived lavas is chiefly determined by preference of LREE for perovskite > apatite > titanite. LREE zoning in perovskite is influenced by changes in melt structure: increasing melt polymerisation enhancing mineral_LREE/melt_LREE partition into perovskite rims in magmatic xenoliths; decreasing melt polymerisation depleting LREE in lava perovskite rims. This zoning is reinforced by perovskite competition with apatite for LREE: perovskite (cores/rims) co-crystallising with apatite is reduced in LREE. There are 37 instances of perovskitewith Ce below detection while La and Nd levels are normal. These occur in both xenoliths and lavas; in grain zones or whole grains. Likewise Ce alone of the LREE is below detection in six out of ten titanite analyses. These observations are interpreted as evidence for increased f_{O 2}, Ce⁴ + being excluded from these mineral structures. Recognition of these various processes can elucidate the interpretation of bulk rock and bulk mineral LREE signatures in kamafugite volcanism.

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LREE Verteilung in Perovskit, Apatit und Titanit aus Xenolithen und kamafugitischen Laven Südwest-Ugandas

Zusammenfassung In-situ LREE Analysen von Perovskit und Titanit (La, Ce, Nd) und Apatit (La, Ce) aus Klinopyroxenit-Xenolithen und kamafugitischen Laven Südwest-Ugandas zeigen, daß die LREE Verteilung in diesen Mineralen durch eine Vielzahl von Faktoren, die mit Unterschieden in den Paragenesen zusammenhängen, bestimmt wird: Der LREE-Gehalt wird im besonderen davon bestimmt, ob die LREE-führenden Minerale aus metasomatischen Karbonat- oder aus (metasomatischen oder magmatischen) Silikatschmelzen im Mantel auskristallisierten. Dabei erfolgt die LREE Fraktionierung zu Gunsten der Karbonatschmelzen. Die LREE-Verteilung von Perovskit und Apatit, die aus magmatischen Mantelschmelzen oder -laven kristallisierten, wird vorrangig durch den bevorzugten Einbau der LREE in Perovskit > Apatit > Titanit kontrolliert. Der LREE Zonarbau von Perovskit wird durch die Änderungen der Schmelzstruktur beinflußt: Verstärkte Schmelzpolymerisation führt zu verstärkter Mineral_LFEE/Schmelze_LREE Fraktionierung in den Perovskiträndern magmatischer Xenolithe, eine Abnahme der Schmelzpolymerisation hingegen resultiert in einer Abreicherung der LREE in den Perovskiträndern. Diese Art der Zonierung wird durch den Wettbewerb von Perovskit mit Apatit um die LREE verstärkt. Perovskit (Kerne/Ränder), der mit Apatit gemeinsam auskristallisierte, ist ärmer an LREE. 37 Fälle, in denenCe nicht nachweisbar war, La und Nd aber in normaler Konzentration auftreten, wurden sowohl in den Xenolithen als auch in den Laven gefunden; und zwar entweder in Kornbereichen oder in ganzen Körnern. Vergleichsweise liegt Ce nur in sechs von zehn Titanitproben unterhalb der Nachweisgrenze. Diese Beobachtungen werden als Hinweise auf erhöhte SauerstoffFugazitäten, bei denen Ce^4– aus der Mineralstruktur ausgeschlossen wird, angesehen.Ein Verständnis dieser verschiedenen Prozesse kann zur besseren Interpretation von LREE Gesamtgesteins- und Gesamtmineral-Signaturen in Kamafugiten beitragen.

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With 3 Figures