The role of fluctuations in the interplanetary magnetic field in determining the magnitude of substorm activity

When hourly averages of interplanetary magnetic-field parameters are compared to the AE index, it is found that, although the time-integral of the southward component is important in determining whether there will be a substorm, the magnitude of storm activity as measured by AE is related to the level of the variance of the field. For a given value of the time-integral of the southward component of the interplanetary magnetic field, the AE index increases as the variance increases. For periods immediately following storm sudden commencements, this simple relationship apparently breaks down indicating that a different triggering process or storm-generation mechanism may be at work. These observations imply that although it is impossible to differentiate between substorms at the Earth's surface, it may be possible to differentiate between the conditions in the solar wind that lead to a certain magnitude of magnetic activity.     

A rapid estimation of organic carbon in silty lake sediments

A rapid and convenient method is described for the estimation of active organic carbon in silty lake sediments collected in regional geochemical surveys. The method utilizes measurement of optical density at 500 nm, of a 4 M nitric acid ? 0.1 M hydrochloric acid leach of a sediment sample and has a precision of ± 26% as determined from separate replicate analyses. An attractive feature of the method lies in its use of the same leach solution on which atomic absorption analyses of trace metals may be made.     

A statistical analysis of the low-energy geosynchronous plasma environment—II. Ions

This is the second of two papers which together provide a detailed statistical analysis of the low-energy (1-eV–100-keV) geosynchronous plasma environment. In this paper, data on the ion environment between ～1 eV and 80 keV are statistically analysed. About 50 days of 10-min averages of the first 4 moments of the ion distribution function from the University of California at San Diego low-energy plasma detectors on the ATS-5 and ATS-6 geosynchronous satellites are studied in terms of: occurrence frequency, local time variations, K_p variations, injection events, and intercomparisons among the 4 moments. Variations in the 4 moments can be explained by assuming the existence of 2 dominant plasma populations (the plasmasphere and ring current) upon which are superimposed plasma injection events. In conjunction with this analysis, the accuracy of the 4-moment representation for ions was tested and, unlike that for electrons, found to be limited by the energy band-pass of the instrumentation and by a lack of knowledge of the angular anisotropies and ionic composition. Even so, these limitations are outweighed by the utility and compactness of the method. A technique for correcting the limited energy band-pass of the instrumentation is presented in the Appendix.     

Diel behavior of stable isotopes of dissolved oxygen and dissolved inorganic carbon in rivers over a range of trophic conditions,and in a mesocosm experiment

Rates of diel (24-h) biogeochemical processes in rivers and their effect on daily changes in the concentration of metals and metalloids have been well documented in the literature over the last 20 years. Investigations into the effects of these processes on aquatic systems and the underlying mechanisms that control the processes can significantly improve our understanding of how natural aquatic environments function and will respond to changing environmental conditions and anthropogenic impacts. Daily changes in the rates of biogeochemical processes have, more recently, been shown to influence the stable isotope composition of dissolved oxygen and dissolved inorganic carbon in natural waters. Here we present a comprehensive picture of the persistence and reproducibility of diel cycles of the ¹⁸O composition of dissolved molecular oxygen (δ¹⁸O-DO) and the ¹³C composition of dissolved inorganic carbon (δ¹³C-DIC) across five Montana, USA rivers investigated over a 4-year period. A mesocosm experiment showed the same behavior in δ¹⁸O-DO and δ¹³C-DIC as seen in riverine settings across light and dark periods.A cross plot of δ¹⁸O-DO and δ¹³C-DIC from each stream exhibits a clockwise elliptical pattern which is attributed to the daily changes in the balance of metabolic rates as well as air–water gas exchange. The amplitude of the change in the isotope composition is shown to be directly related to the trophic state of the river and a relationship between net productivity and diel changes in δ¹⁸O-DO and δ¹³C-DIC is presented. This relationship between trophic status with δ¹⁸O-DO, δ¹³C-DIC and production emphasizes the significance of how rates of biogeochemical processes in natural systems can influence the daily changes in the composition of surface waters.     

An occurrence of cadmiferous phosphorite soil concretions in Jamaica

Bauxite exploration drilling revealed the presence of phosphate minerals through the chemical and XRD analysis of recovered drill hole samples at Spitzbergen, in Manchester Parish, Jamaica. A subsequent pit led to the discovery of phosphorite concretions composed of hard competent masses of finely crystalline fluorapatite, with some minor crandallite. The phosphorite contains anomalously high levels of Zn (>5000 mg kg⁻¹), Cd (>1.1%), Ag (>20 mg kg⁻¹), Be (>80 mg kg⁻¹) and, to a lesser extent, U. Textural and geochemical evidence indicates that the phosphorite concretions were most likely formed by the replacement of limestone by secondary deposition proximal to fossil guano deposits, postulated to be Late Miocene or Pliocene sea-bird colonies. Mechanical dispersion of the phosphorite concretions through karst weathering processes has led to their wider spatial distribution than the original guano deposits. Subsequent weathering of the concretions and the admixture of their decomposition products into the bauxitic and Terra Rossa soils is postulated to be the cause of the widespread anomalous levels of Zn, Cd and Be in these soils in central Jamaica, and the elevated levels of P in the bauxite.