The distribution of particulate iodine in the Atlantic Ocean

The iodine content of marine suspended matter obtained from thirteen stations in the Atlantic between 75°N and 55°S has been measured. The concentration of particulate iodine is high in the surface, up to 127 ng/kg of seawater being observed. Below the euphotic zone, it drops sharply to 1–2 ng/kg. The iodine-containing particles are probably biogenic. A simple box-model calculation shows that only 3% of the particulate iodine produced in the surface water may reach the deep sea and that the residence time of these particles in the surface water is about 0.1 year.     

U234U238 Ratios in limestone cave seepage waters and speleothem from West Virginia

Speleothem from West Virginia, ranging in age from 2000 to 200,000 yr B.P. contains uranium with $\text{U}{}^{234}\text{U}{}^{238}$ ratios significantly greater than unity. This ratio varies from one speleothem to another, as does average U content. Initial ratios, corrected for age, are remarkably constant for a given speleothem. By contrast, $\text{U}{}^{234}\text{U}{}^{238}$ ratios in seepage waters vary significantly from month to month at a given drip site, and their average values differ from that of the speleothem which they are depositing. This discrepancy is attributed either to long-term averaging-out of fluctuations, or fractional precipitation on the speleothem of a chemical species of uranium with a more constant ratio. Constancy of initial $\text{U}{}^{234}\text{U}{}^{238}$ ratios from $\text{Th}{}^{230}\text{U}{}^{234}$. datable portions of speleothems should permit $\text{U}{}^{234}\text{U}{}^{238}$-dating of older portions of the same speleothem, back to about 10⁶ yr B.P., with estimated precision of ±5 per cent.     

Release ofRa from uranium mill tailings by microbial Fe(III) reduction

Uranium mill tailings were anaerobically incubated in the presence of H₂ with Alteromonas putrefaciens, a bacterium known to couple the oxidation of H₂ and organic compounds to the reduction of Fe(III) oxides. There was a direct correlation between the extent of Fe(III) reduction and the accumulation of dissolved²²⁶Ra. In sterile tailings in which Fe(III) was not reduced, there was negligible leaching of²²⁶Ra. The behavior of Ba was similar to that of Ra in inoculated and sterile systems. These results demonstrate that under anaerobic conditions, microbial reduction of Fe(III) may result in the release of dissolved²²⁶Ra from uranium mill tailings.     

Distribution and abundance of large floating plastic in the north-central Gulf of Mexico

Aerial surveys were conducted in the north-central Gulf of Mexico from June 1988 to May 1989. Sightings of marine debris and specifically large floating plastics were recorded during these surveys. Five study areas off the Louisiana coast were monitored and seasonal distribution and densities were estimated. Each study area contained plastic throughout the year. The estimated densities of plastic were largest in the offshore areas (4 & 5) and smallest in the inshore areas (1 & 3). Seasonally, density of plastic was smallest in the summer and largest in the fall. The reasons for the differences in seasons and study areas are not apparent but the amount of plastic in each area and season could be affected by variations in currents, winds, discharge from rivers, and human activity.     

Discussion. Denudational isostatic rebound of intraplate highlands: The Lachlan river valley,Australia

Episodic terrace cutting cannot be a complex response to the steady isostatic rebound forecast by an elastic flexure model because three terraces match epiphreatic passage levels in nearby caves. There is also some doubt about how fluvial incision rates should be extrapolated to catchment-wide rates. At the local scale of the Lachlan River highlands, active tectonic compression may be more important than flexure, which is more important at a regional scale.     

Single grain argon laser probe dating of phengites from the blueschist to greenschist transition on Sifnos (Cyclades,Greece)

Measurements of ⁴⁰Ar/³⁹Ar age spectra on single white mica crystals of Tertiary age is a new means of obtaining detailed geochronological information of Alpine blueschists. Internal consistency of the data set, as well as excellent agreement with previous conventional K–Ar results, demonstrates that this new technique can be used with confidence to obtain information on the thermal evolution of young metamorphic belts.As mineral grains can be dated individually with this technique, problems related to multiple generations of mica occurring side in the rock can be addressed, potentially yielding much information which cannot be obtained easily by other dating techniques. Ages decrease from 41.7±0.3 Ma in the fresh blueschists and eclogites in northern Sifnos to ca 30 Ma in the more severely overprinted greenschists of central Sifnos. It is argued that this decreasing trend appears gradual, rather than stepwise. This gradual character of the age trend is taken to indicate that it may be caused by differential uplift and cooling, rather than by tectonic juxtaposition of different rock units. In addition, the rocks of central Sifnos contain mica with a plateau age of 18.9±0.3 Ma. This latter age is younger than previous estimates for the age of greenschist overprinting, and more in line with the age of high temperature metamorphism and granite emplacement elsewhere in the Cyclades.     

Applied social area analysis: Defining and evaluating areas for urban neighbourhood councils

Urban neighbourhood councils, neither statutorily established nor widely initiated in England, are seen to possess a number of advantages over existing forms of representative participation in relation to the equitable distribution of resources. In Portsmouth a community area perception survey and principal components analysis of census data were undertaken to produce synthesised ‘best fit’ social sub-areas upon which to base neighbourhood councils. These areas were then analysed in terms of their relevance and appropriateness, terms specifically defined, along four scale dimensions. An original contention that for maximum effectiveness neighbourhood councils should be established to cover all urban residential areas was confounded by the manifest irrelevance of the neighbourhood council concept in certain socio-spatial contexts.