A technique to assess dispersion

A technique to arrive at conditions congenial to maintaining a stable suspension of fine particles has been described. The technique involves continuous monitoring of apparent loss of weight of a body suspended in settling slurries. Such a technique is useful in fixing the best conditions for gravity separation of fine particles involving Bartles-Mozley concentrators or hydrocyclones.     

A review of the metallogeny and tectonics of the Lachlan Orogen

Future mineral exploration within eastern Australia will be enhanced by resolving the tectonic evolution of the Lachlan Orogen to establish the spatial and temporal terrane distribution of the various mineral deposits. The Lachlan Orogen, from north-eastern Tasmania through to central and eastern New South Wales, is host to a number of major mineral deposit styles—including orogenic gold (e.g. Stawell, Ballarat, Bendigo), volcanic-hosted massive sulphide (e.g. Woodlawn, Currawong), sediment-hosted Cu–Au (e.g. Cobar Basin deposits), porphyry Au–Cu (e.g. Cadia, Parkes, Cowal) and granite-related Sn (e.g. Ardlethan, Beechworth). Each of these mineral deposit styles is a sensitive and diagnostic indicator of the prevalent tectonic environment during their formation. In this review, we briefly summarise the deposit- to large-scale factors that define the diverse metallogenic evolution of the Lachlan Orogen. This overview is intended to “set the scene” for subsequent specialist papers published in this thematic issue on the metallogeny and tectonics of the Lachlan Orogen in south-east Australia.     

A furrow runs through it: An example of sustainable traditional irrigation in Western Cape Province,South Africa

Water and water related matters are important issues in water scarce countries like the Republic of South Africa. This is especially true for the agricultural sector that relies heavily on the availability of water for irrigation to ensure a secure food supply. In South Africa, present day irrigation projects rely on government subsidies and are usually large undertakings beyond the reach of individuals or small communities. The sustainability of such large irrigation projects is still a matter of debate. A 100 years ago a different set of rules applied. Irrigation could only be achieved by hand-dug furrows that supplied water in relatively small quantities to small farming communities. This paper investigated such a small community, the Leeukloof farming community in the Western Cape Province of the Republic of South Africa. For the past 93 years this community has maintained a furrow that supplies water not only to farms bordering the Perdeberg River, which supplies the furrow with water, but also to farms not bordering the river. The authors try to reconstruct the changes in agricultural practices brought about by the furrow, methods of water extraction during each phase, as well as the development and role of the furrow system. The perception by the community of the necessity of this method of water extraction from the river system is also investigated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sediment oxygen profiles in a super-oxygenated antarctic lake

Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.     

Application of VLEACH to Vadose Zone Transport of VOCs at an Arizona Superfund Site

Cleanup standards for volatile organic compounds in thick vadose zones can be based on indirect risk (transport to ground water) when contamination is below depths of significant direct risk. At one Arizona Superfund site, a one-dimensional vadose zone transport model (VLE-ACH) was used to estimate the continued transport of VOCs from the vadose zone to ground water. VLEACH is a relatively simple and readily available model that proved useful for estimating indirect risk from VOCs in the vadose zone at this site. The estimates of total soil concentrations used as initial conditions for VLF.ACH incorporated a variety of data from the site. Soil gas concentrations were found to be more useful than soil matrix data for estimating total soil concentrations at this arid-zone site. A simple mixing cell model was used with the VLEACH-derived mass loading estimates from the vadose zone over time to estimate the resulting changes in ground water concentrations. For this site, the results of the linked VLEACH/mixing cell simulations indicate it is likely that the federal MCI. for TCE will be exceeded in underlying ground water if remedial action on I he vadose zone is not pursued.     

Groundwater quality assessment from a hard rock terrain, Salem district of Tamilnadu, India

A total of 162 groundwater samples for three representative seasons were collected from Salem district of Tamilnadu, India to decipher hydrogeochemistry and groundwater quality for determining its suitability for drinking and agricultural proposes. The water is neutral to alkaline in nature with pH ranging from 6.6 to 8.6 with an average of 8.0. Higher electrical conductivity was observed during post-monsoon season. The abundance of major ions in the groundwater was in the order of $ {\text{Na} > \text{Ca} > \text{Mg} > \text{K} = \text{Cl} > \text{HC}}{{\text{O}}_3}\; > \;{\text{S}}{{\text{O}}_4}\; > \;{\text{N}}{{\text{O}}_3} $ . Piper plot reveals the dominance of geochemical facies as mixed Ca–Mg–Cl, Na–Cl, Ca–HCO₃, Ca–Na–HCO₃, and Ca–Cl type. NO₃, Cl, SO₄, and F exceed the permissible limit during summer and post-monsoon seasons. Sodium adsorption ratio was higher during post-monsoon and southwest monsoon season indicating high and low salinity, satisfactory for plants having moderate salt tolerance on soils. Permeability index of water irrespective of season falls in class I and class II indicating water is moderate to good for irrigation purposes. As per the classification of water for irrigation purpose, water is fit for domestic and agricultural purposes with minor exceptions irrespective of seasons.     

Geology and impact features of Vargeão Dome,southern Brazil

Abstract– Vargeão Dome (southern Brazil) is a circular feature formed in lava flows of the Lower Cretaceous Serra Geral Formation and in sandstones of the Paraná Basin. Even though its impact origin was already proposed in the 1980s, little information about its geological and impact features is available in the literature. The structure has a rim‐rim diameter of approximately 12 km and comprises several ring‐like concentric features with multiple concentric lineaments. The presence of a central uplift is suggested by the occurrence of deformed sandstone strata of the Botucatu and Pirambóia formations. We present the morphological/structural characteristics of Vargeão Dome, characterize the different rock types that occur in its interior, mainly brecciated volcanic rocks (BVR) of the Serra Geral Formation, and discuss the deformation and shock features in the volcanic rocks and in sandstones. These features comprise shatter cones in sandstone and basalt, as well as planar microstructures in quartz. A geochemical comparison of the target rock equivalents from outside the structure with the shocked rocks from its interior shows that both the BVRs and the brecciated sandstone have a composition largely similar to that of the corresponding unshocked lithologies. No traces of meteoritic material have been found so far. The results confirm the impact origin of Vargeão Dome, making it one of the largest among the rare impact craters in basaltic targets known on Earth.     

Radiation exposure and Mission Strategies for Interplanetary Manned Missions (REMSIM)

Cosmic radiation is an important problem for human interplanetary missions. The “Radiation Exposure and Mission Strategies for Interplanetary Manned Missions–REMSIM” study is summarised here. They are related to current strategies and countermeasures to ensure the protection of astronauts from radiation during interplanetary missions, with specific reference to: radiation environment and its variability; radiation effects on the crew; transfer trajectories and associated fluences; vehicle and surface habitat concepts; passive and active shielding concepts; space weather monitoring and warning systems.