Search

Increasing salinisation is occurring over large parts of south-eastern Australia. This has potential to impact severely on the biodiversity of wetlands affected by rising saline groundwater and inundated by saline water discharged to rivers. Investigations have been made into the effect of salinities of 2, 2–6 (increased over 64 days) and 6 g NaCl l−1 on the growth, leaf demography and ion concentrations of three wetland macrophytes, Amphibromus fluitans, Potamogeton tricarinatus and Triglochin procera grown in greenhouse troughs. Potamogeton tricarinatus was the most severely affected showing significantly reduced dry weight and leaf size at 6 g l−1 along with a reduction in leaf appearance rate and an increase in leaf death. Triglochin procera was not as severely effected although leaf size was still reduced in 6 g l−1 treated plants. Amphibromus fluitans was unaffected by salinity. Na+, K+ and Cl− ion contents were determined for leaves of different ages. The three species exhibited very different patterns of ion accumulation. Amphibromus fluitans excluded Na+ and maintained a low concentration of Na+ in younger leaves relative to older leaves. Potamogeton tricarinatus was saturated in uptake of Na+ at all treatment levels. No leaf age effect was observed, with similar Na+ concentrations in all leaves. The absence of a leaf age gradient may be attributable to a capacity to absorb Na+ from the water column directly into the leaves irrespective of age. Na+K+ ratios were lowest for A. fluitans with a strong leaf age gradient of increasing Na+K+ ratio from younger to older leaves. Potamogeton tricarinatus was intermediate in Na+K+ ratio but with no clear leaf age gradient. Whereas Na+K+ ratios ranged from 2 to 8 for A. fluitans and 5 to 15 in P. tricarinatus, T. procera ranged from 5 in the youngest leaves to 35 in the oldest leaves. Triglochin procera like its halophytic relative, Triglochin maritima, had very high Na+K+ ratios. Triglochin procera may be capable of absorbing Na+ into leaf vacuoles which could be balanced by a high concentration of a compatible solute such as proline in the leaf cell cytoplasm.

Crystals of Li2SO4 · H2O irradiated with X-rays for 6 hours at room temperature contain a paramagnetic center identified as LiOH+2. The observed hyperfine structure comes from two types of nuclei, one with I = 3 2 and the other with I = 1. The first is assigned to the lithium and the second to two equivalent hydrogens. From the tensor directions the location and orientation of the center is determined. A positive g-shift indicates a hole-type center.

Heating ammonium sulphate to near its dissociation temperature and then quenching to room temperature produces a stable triplet state center that is identified as NH2+. The symmetry of the EPR spectra indicates that the center is located in two non equivalent sites with each of these sites having slightly different EPR parameters and two measurably differents orientations. Thus the center is apparently occupying the positions of the NH4+ groups in the perfect lattice. A study is made of this center both at room temperature and also well below the ferroelectric phase transition of (NH4)2SO4. It is found that above and below the transition temperature (−50°C) there is very little temperature dependence of the EPR spectra but at the phase transition there is an abrupt change in the spectra. The number of detectable centers doubles below the phase transition indicating that the inversion symmetry of the NH2+ sites is eliminated at the transition temperature.

One of the major objectives of the National Waste Terminal Storage Program is to identify potential geologic sites for storage and isolation of radioactive waste (and possibly irradiated fuel). Potential sites for the storage and isolation of radioactive waste or spent fuel in a geologic rock unit are being carefully evaluated to ensure that radionuclides from the stored waste or fuel will never appear in the biosphere in amounts that would constitute a hazard to the health and safety of the public. The objective of this report is to quantify and present in graphical form the effects of significant geohydrologic and other performance characteristics that would influence the movement of radionuclides from a storage site in a rock unit to the biosphere. The effort in this study was focused on transport by groundwater because that is the most likely method of radionuclide escape. Graphs of the major performance characteristics that influence the transport of radionuclides from a repository to the biosphere by groundwater are presented. The major characteristics addressed are radioactive decay, leach rate, hydraulic conductivity, porosity, groundwater gradient, hydrodynamic dispersion, ion exchange, and distance to the biosphere. These major performance characteristics are combind with each other and with themore » results of certain other combinations and presented in graphical form to provide the interrelationships of values measured during field studies. The graphical form of presentation should be useful in the screening process of site selection. An appendix illustrates the use of these graphs to assess the suitability of a site.« less