Use of Pb/Pb ratios to investigate the surface integrity of peat cores used to study the recent depositional history and geochemical behaviour of inorganic elements in peat bogs

The well characterised temporal trend in the ²⁰⁶Pb/²⁰⁷Pb atom ratio of atmospheric lead deposition in Scotland during the 20th century was used to investigate the surface integrity of several cores collected by different methods from Flanders Moss ombrotrophic peat bog, central Scotland, during 1996–2001. Based on ²⁰⁶Pb/²⁰⁷Pb profile comparisons, in conjunction with identified ²¹⁰Pb radionuclide inventory deficits for two of the cores, it was deduced that 25 ± 7 yrs worth of material was missing from the more seriously affected core. After allowing for an appropriate vertical offset based on ²⁰⁶Pb/²⁰⁷Pb profile matching, the subsequent matching of profiles of titanium, lead, sulfur, arsenic, iron, phosphorus and manganese in three cores for which total concentration data were available was excellent. Without such offset correction, erroneous conclusions could have been drawn concerning the recent historical record of anthropogenic lead and arsenic deposition, the position of the redox boundary, which controls geochemical cycling and enrichment of iron, and the nutrient recycling status of manganese and phosphorus in the near-surface vegetation. Topographic, vegetative and coring (both device and operator) influences may have been responsible, thus endorsing the use of reliable, multiple core sampling and the use of lead isotope ratio profiles, supplemented by appropriate radionuclide data, in both assessing and ensuring the surface integrity of peat cores.     

Stability field and phase transition pathways of hydrous ferric sulfates in the temperature range 50 °C to 5 °C: Implication for martian ferric sulfates

We report the results from a systematic laboratory investigation on the fundamental properties of hydrous ferric sulfates. The study involves 150 experiments with duration of over 4 years on the stability field and phase transition pathways under Mars relevant environmental conditions for five ferric sulfates: ferricopiapite [Fe_4.67(SO₄)₆(OH)₂·20H₂O], kornelite [Fe₂(SO₄)₃·7H₂O], a crystalline and an amorphous pentahydrated ferric sulfate [Fe₂(SO₄)₃·5H₂O], and rhomboclase [FeH(SO₄)₂·4H₂O]. During the processes of phase transitions, we observed the phenomena that reflect fundamental properties of these species and the occurrence of other common hydrous ferric sulfates, e.g. paracoquimbite [Fe₂(SO₄)₃·9H₂O]. Based on the results of this set of experiments, we have drown the boundaries of deliquescence zone of five hydrous ferric sulfates and estimated the regions of their stability field in temperature (T) – relative humidity (RH) space. Furthermore, we selected the experimental parameters for a next step investigation, which is to determine the location of the phase boundary between two solid ferric sulfates, kornelite [Fe₂(SO₄)₃·7H₂O] and pentahydrated ferric sulfate [Fe₂(SO₄)₃·5H₂O]. The experimental observations in ferricopiapite dehydration processes were used to interpret the observed spectral change of Fe-sulfate-rich subsurface soils on Mars after their exposure by the Spirit rover to current martian atmospheric conditions.     

Intramolecular carbon isotopic analysis of acetic acid by direct injection of aqueous solution

We report an improved method for determining the intramolecular carbon isotopic composition of acetate using direct injection of aqueous samples. The system builds upon prior work that established pyrolytic conditions for online analysis and represents a significant advance in that it requires minimal preparation for samples containing as little as 1 mM sodium acetate in aqueous solution. The technique is applicable for analysis of oilfield brines, culture samples, biological samples and natural porewaters. We demonstrate its accuracy by use of a stable isotope dilution series. We also show that addition of a base and cryogenic preconcentration may induce an isotopic effect on the carboxyl carbon. This isotopic fractionation does not appear to extend to the measured methyl carbon isotope value although it can significantly alter the measured isotopic composition of the whole molecule. Our preconcentration experiments demonstrate that the method is suitable for carbon isotopic measurements of acetate methyl carbon in natural samples at concentrations as low as 90 μM, considerably broadening potential applications.     

Comet Tago-Sato-Kosaka 1969 IX: Tail structure 25 December 1969 to 12 January 1970

On photographs taken between 25 December 1969 and 12 January 1970 with the Michigan Curtis Schmidt on Cerro Tololo and the Hamburg Schmidt at the Boyden Observatory, Comet 1969 IX is seen projected on planes nearly perpendicular to its orbit. During this period the Type I tail was free of major structural disturbances, and the faintness of the Type II tail facilitated study of the Type I tail near the lead. Characteristics of the main Type I tail are described in Part II. A classification of the tail forms according as the tail had the form of a fan of rays or a wedge, the orientation of the tail axis, and the angular width of the tail are discussed in Section IIA. In Section IIB the structure of the tail from 26 to 31 December, a period within which a disconnection of the tail took place, is viewed as the possible result of the passage across the comet of an interplanetary magnetic sector boundary, as proposed by Niedner and Brandt (1977, Bull. Amer. Astron. Soc. 4). In Sections IIC and IID waves in rays and the onset of turbulence are considered. Section IIIA is devoted to unusually long and bright off-axis rays; data on longitudinal forms, closing rate to the axis, and photometry of a ray are presented. In Section IIIB the structure of a “plume” of seven nearly parallel rays is related to the configuration of magnetic field lines predicted by Schmidt and Wegmann (1976, IPP Report 6/147). The orientations of the plume rays are consistent with those of the calculated field lines; the inferred rate of generation of the rays is about 1/hr.