Connection between Hill stability and weak stability in the elliptic restricted three-body problem

This paper provides a study on the connection between Hill stability and weak stability in the framework of the spatial elliptic restricted three-body problem. We determine a necessary condition for weak stability by giving an upper and a lower bound of qualitative measure of the Hill stability. The sufficient condition for weak stability and the symmetry of weak stable regions around the planets of the Solar System is also investigated.     

Inclusion of adsorption in the modelling of early diagenesis

A general one-dimensional diagenetic equation is derived which expresses the effect of the following processes upon the depth and time distribution of a dissolved species in a modern subaqueous sediment: adsorptive or ion exchange equilibrium between pore water and grain surfaces; slower chemical or radiogenic reactions in the pore solution and on the grain surfaces; diffusion in solution and on grain surfaces; advection of grains due to depositional burial; and advection of water due both to burial and to flow past the grains. It is shown that the effects of equilibrium adsorption can be expressed in terms of a lowered diffusion coefficient only in the special case where there is negligible flow of water relative to grains, adsorption is described by a simple linear isotherm, and there is nochemical reaction occurring in the sediment (i.e. only radioactive decay or no reaction at all). Consideration of a commonly used special case of the general equation indicates that if equilibrium adsorption is strong, the depositional term in the resulting diagenetic equation may become quantitatively as important as the terms for diffusion and chemical reaction. Thus, when modelling diagenesis, deposition often cannot be ignored. A coupled pair of differential equations are also derived which express the steady state depth distribution for two ions exhibiting equilibrium ion exchange while undergoing chemical reaction, diffusion, and deposition.     

A closure study of sub-micrometer aerosol particle hygroscopic behaviour

The hygroscopic properties of sub-micrometer aerosol particles were studied in connection with a ground-based cloud experiment at Great Dun Fell, in northern England in 1995. Hygroscopic diameter growth factors were measured with a Tandem Differential Mobility Analyser (TDMA) for dry particle diameters between 35 and 265 nm at one of the sites upwind of the orographic cloud. An external mixture consisting of three groups of particles, each with different hygroscopic properties, was observed. These particle groups were denoted less-hygroscopic, more-hygroscopic and sea spray particles and had average diameter growth factors of 1.11–1.15, 1.38–1.69 and 2.08–2.21 respectively when taken from a dry state to a relative humidity of 90%. Average growth factors increased with dry particle size. A bimodal hygroscopic behaviour was observed for 74–87% of the cases depending on particle size. Parallel measurements of dry sub-micrometer particle number size distributions were performed with a Differential Mobility Particle Sizer (DMPS). The inorganic ion aerosol composition was determined by means of ion chromatography analysis of samples collected with Berner-type low pressure cascade impactors at ambient conditions. The number of ions collected on each impactor stage was predicted from the size distribution and hygroscopic growth data by means of a model of hygroscopic behaviour assuming that only the inorganic substances interacted with the ambient water vapour. The predicted ion number concentration was compared with the actual number of all positive and negative ions collected on the various impactor stages. For the impactor stage which collected particles with aerodynamic diameters between 0.17–0.53 μm at ambient relative humidity, and for which all pertinent data was available for the hygroscopic closure study, the predicted ion concentrations agreed with the measured values within the combined measurement and model uncertainties for all cases but one. For this impactor sampling occasion, the predicted ion concentration was significantly higher than the measured. The air mass in which this sample was taken had undergone extensive photochemical activity which had probably produced hygroscopically active material other than inorganic ions, such as organic oxygenated substances.     

Geochemical,mineralogical and magnetic characteristics of vertical dust deposition in urban environment

Studies on composition and distribution of dust deposition are necessary for the risk assessment of dust to atmospheric quality. We studied the vertical distribution pattern of dust and metal (Cu, Fe, Pb, Zn) deposition up to 33 m height in urban environment. Integrated geochemical, mineralogical and magnetic study of the seasonally sampled dust helped to specify our knowledge on the use of magnetic susceptibility for tracking its deposition. Harmful dust and metal deposition may occur even at great heights and at the low-traffic side of buildings. Re-suspension of local surface materials dominates the dust deposition primarily in summer and spring due to weather conditions, and it may overwrite the influence of recent anthropogenic activities on dust composition. The accepted air-flow models should be modified by taking the local conditions (weather, morphology, etc.) into account. All studied metals showed strong enrichment in the dust and could be characterized by similar vertical deposition pattern to dust. The total susceptibility was found to be much more useful proxy for tracking dust and metal deposition than mass-specific susceptibility. Using the former, potential errors arising from sampling practice of settled dust could be eliminated. The most important heavy-metal-bearing phases were iron oxides and clay minerals. Their different behavior during the dust deposition is reflected by the vertical metal distribution patterns. Clay minerals originate primarily from re-suspension and may be one of the most important sources of potentially mobile heavy metals in such materials.     

The Sensitivity of the Phanerozoic Inorganic Carbon System to the Onset of Pelagic Sedimentation

The onset of pelagic sedimentation attending the radiation of pelagic calcifiers during the Mesozoic was an important divide in Earth history, shifting the locus of significant carbonate sedimentation from the shallow shelf environments of the Paleozoic to the deep sea. This shift would have impacted the CO₂ cycle, given that decarbonation of subducted pelagic carbonate is an important return flux of CO₂ to the atmosphere. Coupled with the fact that the mean residence time of continental platform and basin sedimentary carbonate exceeds that of the oceanic crust, it thus becomes unclear whether carbon cycling would have operated on a substantially different footing prior to the pelagic transition. Here, we examine this uncertainty with sensitivity analyses of the timing of this transition using a coupled model of the Phanerozoic atmosphere, ocean, and shallow lithosphere. For purposes of comparison, we establish an age of 250 Ma (i.e., after the Permo-Triassic extinctions) as the earliest opportunity for deposition of extensive biogenic pelagic carbonate on the deep seafloor, an age that predates known occurrences of pelagic calcifiers (and intact seafloor). Although an approximate boundary, we do show that attempts to shift this datum either significantly earlier or later in time produce model results that are inconsistent with observed trends in the mass–age distribution of the rock record and with accepted trends in seawater composition as constrained by proxy data. Significantly, we also conclude that regardless of the timing of the onset of biogenic pelagic carbonate sedimentation, a carbon sink involving seawater-derived dissolved inorganic carbon played a critical role in carbon cycling, particularly in the Paleozoic. This CaCO₃ sink may have been wholly abiogenic, involving calcium derived either directly from seawater (thus manifest as a direct seafloor deposit), or alternatively from basalt–seawater reactions (represented by precipitation of CaCO₃ in veins and fissures within the basalt). Despite the uncertainty in the source and magnitude of this abiogenic CaCO₃ flux, it is likely a basic and permanent feature of global carbon cycling. Subduction of this CaCO₃ would have acted as a basic return circuit for atmospheric CO₂ even in the absence of biogenically derived pelagic carbonate sedimentation. Lastly, model calculations of the ratio of dissolved calcium to carbonate ion (Ca²⁺/CO₃ ^2?) show this quantity underwent significant secular evolution over the Phanerozoic. As there is increasing recognition of this ratio’s role in CaCO₃ growth and dissolution reactions, this evolution, together with progressive increases in nutrient availability and saturation state, may have created a tipping point ultimately conducive to the appearance of pelagic calcifiers in the Mesozoic.     

Estimation of an upper limit on prehistoric peak ground acceleration using the parameters of intact speleothems in Hungarian caves

The examination of speleothems in the Hajnóczy and Baradla caves (northeastern Hungary) allows estimating an upper limit for horizontal peak ground acceleration generated by paleoearthquakes. The density, the Young’s modulus and the tensile failure stress of the samples originating from a broken speleothem have been measured in a laboratory, whereas the natural frequency of intact speleothems was determined by in situ observations. The value of horizontal ground acceleration resulting in failure, the natural frequency and the inner friction coefficient of speleothems were assessed by theoretical calculations. The ages of the samples taken from a stalagmite 5.1 m in height (Baradla cave) have been determined by inductively coupled plasma mass spectrometry analysis and alpha spectrometry. The measured ages fall between 140,000 and 70,000 years; therefore, we assume the speleothem has not been changed since the end of this time interval. According to our modeling results, this speleothem has not been excited by a horizontal acceleration higher than 0.05 g during the last 70,000 years.     

An Earth Systems Diagram for the Global Cycles of Carbon and Phosphorus and Their Effects on Atmospheric CO2 and O2

A complex cause–effect type earth systems diagram is presented that represents the interrelation of the global carbon and phosphorus cycles over geological time. It demonstrates how a lot of information can be represented in an extremely compact manner and how relatively unrecognized positive and negative feedbacks are revealed by tracing paths on the diagram. Emphasis is on how the C and P cycles affect the levels of atmospheric CO₂ and O₂, often via rather indirect paths.     

Temporal variations in arsenic concentration in the groundwater of Murshidabad District,West Bengal,India

Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in both space and time are scarce for most parts of West Bengal (India). Hence, this study has been undertaken to investigate the extent of As pollution and its temporal variability in parts of Murshidabad district (West Bengal, India). Water samples from 35 wells were collected during pre-monsoon, monsoon and post-monsoon seasons and analyzed for various elements. Based on the Indian permissible limit for As (50 μg/L) in the drinking water, water samples were classified into contaminated and uncontaminated category. 18 wells were reported as uncontaminated (on average 12 μg/L As) and 12 wells were found contaminated (129 μg/L As) throughout the year, while 5 wells could be classified as either contaminated or uncontaminated depending on when they were sampled. Although the number of wells that alternate between the contaminated and uncontaminated classification is relatively small (14%), distinct seasonal variation in As concentrations occur in all wells. This suggests that investigations conducted within the study area for the purpose of assessing the health risk posed by As in groundwater should not rely on a single round of water samples. In comparison to other areas, As is mainly released to the groundwater due to reductive dissolution of Fe-oxyhydroxides, a process, which is probably enhanced by anthropogenic input of organic carbon. The seasonal variation in As concentrations appear to be caused mainly by dilution effects during monsoon and post-monsoon. The relatively high concentrations of Mn (mean 0.9 mg/L), well above the WHO limit (0.4 mg/L), also cause great concern and necessitate further investigations.     

Beloc, Haiti, revisited: multiple events across the KT boundary in the Caribbean

Examination of new expanded K/T boundary sections near Beloc, Haiti, reveals deposition of a glass spherule-rich deposit (SRD) and two (PGE) anomalies (one Ir-dominated and one Pd-dominated) during the early Danian Parvularugoglobigerina eugubina Zone [Pla(l)]. The presence of the Haiti SRD within the early Danian is interpreted as being due to reworking. Ir is only slightly elevated within the SRD but forms an anomaly at the top of the SRD extending into the overlying pelagic limestones. It is unclear at present whether this Ir anomaly results from mechanical reworking of an impact at the K/T boundary, or an additional impact event in the early Danian. The second PGE anomaly upsection is dominated by Pd and Pt and is more compatible with a magmatic origin. This suggests a multi-event scenario consistent with one (and possibly two) impact(s), followed by a PGE-enriched volcanic event in the Caribbean.