Quaternary and extant euryhaline Lamprothamnium Groves (Charales) from Australia: Gyrogonite morphology and paleolimnological significance

Charophytes are very common in Australian modern and Quaternary waterbodies, and are quite commonly incorrectly reported as “Chara” sp. or Lamprothamnium papulosum (Wallroth) Groves. This paper is the first attempt at the identification of the widespread euryhaline genus Lamprothamnium in Australia, and its use as a paleoenvironmental indicator. Lamprothamnium is distributed worldwide in all continents, except north and central America. The Australian environment, characterized by increasing aridity during the last 500 ka, has an abundance of saline lakes. We sampled 30 modern lakes and identified extant Lamprothamnium macropogon (A. Braun) Ophel and Lamprothamnium succinctum (A. Braun in Ascherson) Wood. Fossil gyrogonites, from lacustrine sediments ∼65 ka old from Madigan Gulf, Lake Eyre, were identified as Lamprothamnium williamsii sp. nov. We applied statistical analysis (analysis of variance, ANOVA) to the morphometry of the gyrogonites from one fossil and three living Lamprothamnium populations. The ANOVA test suggests all the populations are different, including two separate populations of extant L. macropogon, interpreted in this case as the expression of ecophenotypic variability. Lamprothamnium is a useful paleoenvironmental indicator because it indicates a non-marine environment with varying salinity ranging from fresh (usually 2–3 g l⁻¹) to 70 g l⁻¹, and water bodies holding water for at least 70 consecutive days. Collectively, these parameters provide important information in the study of ephemeral habitats.     

Laboratory Column Experiments Using Polymer Mats to Remove Selected VOCs, PAHs, and Pesticides from Ground Water

Large-scale column experiments were undertaken to evaluate the potential of polymer mats to remove selected volatile organic compounds, polycyclic aromatic hydrocarbons, and pesticides (atrazine and fenamiphos) from ground water and potentially to act as permeable reactive barriers in contaminated ground water environments. The polymer mats, composed of interwoven silicone (dimethylsiloxane) tubes and purged with air, were installed in 2 m long flow-through columns. The polymer mats proved efficient in physically removing (stripping) benzene and naphthalene from contaminated water. Removal efficiencies for both these compounds from an aqueous phase flowing past a polymer mat were 75% or greater. However, for atrazine and fenamiphos, removal efficiencies were 5% or less, probably as a result of their lower Henry's law constants and possibly lower polymer diffusion coefficients.
These experiments indicate that, at least for relatively volatile compounds, polymer mats can provide a remediation technique for the removal of organic compounds from contaminated water. Application of this technique may be well suited as a longer-term, semipassive strategy to remediate contaminated ground water, using natural ground water flow to deliver contaminated ground water to polymer mats engineered as sorption-stripping barriers.
Additional benefits of this technique may include targeted delivery of gaseous chemical amendments, such as oxygen, to enhance aerobic biodegradation and to further reduce any residual concentrations of contaminants.     

The effects of a constant volume deformation on the magnetization of an artificial sediment

Anhysteretic remanent magnetization (DC field = 1 Oe, peak AC field = 1000 Oe) was given to an artificial sediment consisting of a kaolinite matrix and a 0.03% magnetic fraction of needle-shaped magnetite grains. The mean grain size of the clay flakes and the magnetite needles was approximately 0.5 μm. This sediment was subjected to plane strain while maintaining constant volume. The axis of maximum compression was shortened by as much as 331/3%, which produced no significant change in the direction of magnetization with a decrease in intensity of 28%. A continuous deformation model, in which the magnetite needles are embedded in a plastically deforming linearly homogeneous medium, failed to explain these results. A discontinuous deformation model was more successful. In this model, deformation occurs mainly in shear zones bounding blocks which translate along the shears. Only those magnetite grains in the shear zones rotate, and from symmetry considerations no net change in the direction of magnetization is predicted. Because magnetite grains rotate in opposite directions in complementary sets of shears, the model predicts a decrease in intensity comparable to that which was observed.     

The UV-Visible Absorption Cross-Sections and Atmospheric Photolysis Rate of HOI

The UV-visible absorption cross-sections of HOI have been recorded over the wavelength range 278-494 nm and at 298 K following generation of HOI in the gas phase using laser flash photolysis. The gas phase reaction of OH with I₂ was used to produce HOI, and the absorption spectrum of HOI was calibrated relative to the consumption of I₂. The HOI spectrum recorded exhibits 2 broad absorption maxima of = 3.99 × 10^-19 cm² and = 2.85 × 10^-19 cm², centred at 338.4 nm and 404.8 nm respectively. The spectrum is adequately described by a parameterisation consisting of two semi-logarithmic Gaussian distribution functions. The HOI spectrum is more intense than that recorded in previous work of Jenkin, but is in good agreement with more recent work by Bauer et al. The parameterised HOI absorption spectrum recorded in this work was used in a radiative model to calculate the atmospheric photolysis rate (J-value) of HOI. These results indicate that, under most sunlit conditions, HOI has a lifetime with respect to solar photolysis of the order of minutes. Experiments attempting to generate HOI by the reaction of O atoms with C₂H₅I led to complex absorption spectra containing a negative contribution to the absorption from the photolytic removal of an unidentified species. In addition, evidence was found for adsorption and desorption of an iodine-containing species in the reaction vessel. This behaviour is rationalised in terms of the disproportionation of HOI to I₂O, and an uncalibrated spectrum tentatively attributed to I₂O has been recorded.     

Photochemical aspects of tropospheric iodine behaviour

The I-atom sensitised decomposition of ozone in air at 1 atm pressure and ambient temperature has been investigated. Iodine atoms were produced by photolysis of I₂ using visible light or of CH₃I using ultraviolet light. In both cases, the quantum yield for O₃ decomposition was 1.25 (±0.11) per I atom. An important role is proposed for the self-reaction of IO radicals leading to higher oxides of iodine, IO+IO(+M)I₂O₂(+M)higher oxides, which predominated over the bimolecular reaction leading to regeneration of I atoms, IO+IO2I+O₂, with k _2a/k _2b4. Simple computer modelling calculations indicate that reaction (2a) may be important in determining the fate of photolabile iodine species in the atmosphere. The consequences for the behaviour of radioiodine releases are also discussed.     

Li,Sr, Mg,and Na in foraminiferal calcite shells from laboratory culture,sediment traps,and sediment cores

Constant-temperature laboratory culture experiments of the planktonic foraminiferal species Globigerinoides sacculifer (Brady) suggest that the ratios of Li and Sr to Ca in the shells are a function of these ratios in the culture solutions. $\text{Mg}\text{Ca}$ and $\text{Na}\text{Ca}$ in the shells did not vary with changes of these ratios in the culture solution. These are the first direct determinations of the relationship between foraminiferal shell chemistry and solution composition.The possibility of temperature dependence for the minor elemental composition of foraminiferal shells was also investigated in the laboratory and by analysis of several planktonic and one benthic foraminiferal species from sediment trap and sediment core samples. The $\text{Sr}\text{Ca}$, $\text{Mg}\text{Ca}$, and $\text{Na}\text{Ca}$ ratios in the natural samples roughly correlate with calcification temperature, whereas differences in the Li/Ca ratios are small and not systematically related to temperature. However, laboratory culture experiments at 20°C and 30°C showed no variation in the $\text{Li}\text{Ca}$, $\text{Sr}\text{Ca}$, $\text{Mg}\text{Ca}$, and $\text{Na}\text{Ca}$ ratios with calcification temperature for the planktonic foraminifera G. sacculifer and Orbulina universa. Therefore, observed differences in the $\text{Sr}\text{Ca}$, $\text{Mg}\text{Ca}$, and $\text{Na}\text{Ca}$ ratios for the sediment trap and core foraminiferal samples cannot be ascribed to direct effects of calcification temperature, but may be due to some other environmental factor which is correlated with temperature.     

Talc paragenesis in some siliceous dolomitic rocks,and its sedimentologic significance

Thin (0.5–4 mm), contorted stringers of talc, associated with apatite and minor pyrite, are containdy Formation in eastern Alabama. The form, position and lithologic distribed within generally saccharoidal dolomite-quartz marbles of the Cambrian Shaution of the stringers strongly suggest an algalstromatolitic origin, with interlaminar trapped dolomitic muds. Metamorphic formation of talc plus apatite proceeded only within the stringers, whereas surrounding marble remained as unreacted dolomite plus quartz. Talc generation is best explained by the reaction $${\text{dolomite}} + {\text{silica}} + {\text{water}} + {\text{P}}_{\text{2}} {\text{O}}_{\text{5}} = {\text{talc}} + {\text{apatite}} + {\text{CO}}_{\text{2}}$$ in which the phosphate was supplied to the reaction from organic matter contained within the stromatolitic layers. The system was probably open to CO₂ during metamorphism, and \(P_{{\text{CO}}_{\text{2}} }\) remained relatively low.