The direct measurement of ppm levels of uranium in soils using high-resolution Ge(Li) gamma-ray spectroscopy

The direct determination of ²³⁸U in various soil samples was done by measuring the 63.3-keV transition from the decay of the first daughter ²³⁴Th. Potential errors resulting from the chemical non-equilibrium of ²³⁸U with its daughters are thus avoided. The method sensitivity is 1 ppm compared to the 35 ppm obtainable by employing the 1001-keV gamma ray. A Ge(Li) gamma-ray spectrometer is the only analytical tool required. Examples are offered that demonstrate the usefulness of the technique for routine, inexpensive environmental monitoring of uranium. The technique also has the capability of providing information on the ²³⁸U/²³⁵U isotopic ratio.     

Heavy metals in tissues of stranded short-finned pilot whales.

Selected tissues from four short-finned pilot whales that stranded at Cumberland Island National Seashore were analyzed for total cadmium, mercury and selenium by neutron activation. Cadmium reached a maximum mean wet weight concentration of 31.4 ppm in the kidney tissues. Maximum mean wet weight concentrations of mercury, 230.0 ppm, and selenium, 44.2 ppm, were found in the liver tissues. The lowest concentration of each metal was found in the blubber. Postmortem examination showed that the whales had no food in their stomachs. The whales must have been utilizing metabolic reserves, contaminated with residual concentrations of heavy metals, prior to beaching. This utilization of reserves probably resulted in the high concentrations of cadmium, mercury and selenium found in the liver and kidney tissues. Since the heavy metal concentrations were three to four times greater in the stranded whales, as compared to apparently healthy whales of the same species, it is suggested that heavy metal toxicosis may have been a factor contributing to this particular stranding.     

The economic effect of age and education on the regional flows of Black human capital

This paper quantifies and analyzes the flow of human capital caused by the migration of Blacks within the U.S. over time. Detailed characteristics of migration flows for Blacks moving in and out of each of the nine divisions in the U. S. were determined and multiplied by the appropriate value of human capital (discounted earnings approach). These flows were then summed to determine the aggregate inter-regional flows of Black human capital. The effects of age and education on these flows are analyzed as are the probable effects of such flows on regional economic growth.Results of the study show that there is a significant ageeducation interaction effect for Blacks. In addition, these interregional flows suggest that there is a substantial flow of Black human capital from the South to the North and West, and from the North to the West. Significant losses in Black human capital on the part of the South have several rather important public policy implications.     

Cost-benefit analysis of the use of TBT: the case for a treatment approach

The current climate of hostility towards the use of tributyltin (TBT) as an active ingredient in ship anti-fouling paint appears to be based on a very biased assessment of its environmental impact. While many national and international regulatory agencies are moving towards further restriction, and a complete ban is under active discussion, a number of factors appear to have been ignored. The economic impact of a ban on TBT when no adequate substitute exists could be substantial. Environmentally, consequences would include a substantial increase in the consumption of fossil fuel, with corresponding increases in carbon dioxide and sulphur dioxide emissions; the construction of more vessels; the transfer of ship-building, ship-repairing and ship-breaking activities from well-regulated to unregulated or under-regulated areas in the developing world; and a shift from sea transport to less environmentally acceptable forms of transport. Experience in Europe and other parts of the developed world shows that existing restrictions, where they are properly enforced, are probably adequate to alleviate the environmental damage associated with TBT. Some existing legislation acts to inhibit the search for effective substitutes. The environmental benefits of TBT have been ignored. Little thought has been given to a technical, rather than a legislative solution to controlling TBT inputs to the environment. A method is described for treating TBT-contaminated wastewaters, which has been successfully tested in prototype at full scale. Legislative measures against TBT will do nothing to address the problem of the existing backlog of contaminated material, nor even to permit the IMO proposal for the removal of TBT from all ships by 2008 to be successfully concluded in an environmentally safe manner, since no provision has been made for the disposal of the existing TBT; most probably it will be dumped in environmentally sensitive, unregulated areas in the developing world.     

Elastoplastic finite-element analysis of the bearing capacity of beds of reconstructed entities

A method is presented for determination of the coefficients that take into account the increase in angle of internal friction and specific cohesion of silty-clayey soils in predicting variation in the bearing capacity of beds after the long-term effect of the consolidating service-induced loads. __________ Translated From Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, Pp. 18–21, March–April, 2007.     

Microbial activity and distribution during enhanced contaminant dissolution from a NAPL source zone

Laboratory experiments were conducted to assess microbial reductive dechlorination in one-dimensional sand columns containing a 10 cm long source zone of uniformly distributed residual tetrachloroethene (PCE) nonaqueous phase liquid (NAPL), a 10 cm long transition zone directly down-gradient of the source zone containing some nonuniformly distributed NAPL ganglia, and a 40 cm long plume region down-gradient of the transition zone. The activity and distribution of Sulfurospirillum multivorans, a PCE-to-1,2-cis-dichloroethene (cis-DCE) dechlorinating bacterium, was evaluated in columns containing either a mixed-NAPL (0.25 mol/mol PCE in hexadecane) or pure PCE-NAPL. Significant dechlorination of PCE to cis-DCE was observed in the mixed-NAPL column, resulting in 53% PCE-NAPL mass recovery in the effluent with PCE-NAPL dissolution enhanced by up to 13.6-fold (maximum) and 4.6-fold (cumulative) relative to abiotic dissolution. Quantitative real-time PCR targeting pceA, the PCE reductive dehalogenase gene of S. multivorans, revealed that S. multivorans cells were present in the NAPL source zone, and increased in numbers (i.e., grew) throughout the source and transition zones. In contrast, minimal reductive dechlorination and microbial growth were observed in the column containing pure PCE-NAPL, where aqueous-phase PCE concentrations reached saturation. These results demonstrate that microbial growth within NAPL source zones is possible, provided that contaminant concentrations remain below levels toxic to the dechlorinating organisms, and that microbial growth can result in significant bioenhanced NAPL dissolution.     

The characterisation of friction stir welding process effects on stiffened panel buckling performance

The introduction of advanced welding methods as an alternative joining process to riveting in the manufacture of primary aircraft structure has the potential to realise reductions in both manufacturing costs and structural weight. However, welding processes can introduce undesirable residual stresses and distortions in the final fabricated components, as well as localised loss of mechanical properties at the weld joints. The aim of this research is to determine and characterise the key process effects of friction stir welding assembly methods on stiffened panel static strength performance. Utilising experimentally validated finite element modelling methods, it is demonstrated that welding induced residual stresses have a significant influence, and that collapse behaviour is less sensitive to advanced process effects and process effect magnitudes than panel initial buckling behaviour.     

Review of toxicity test results submitted in support of pesticide tolerance petitions.

A long term-low level exposure (LLE) experiment was conducted on rats to determine the metabolic patterns for realistic environmental dietary levels of cadmium. Male rats fed with 61 ppb of cadmium ad libitum, 50 labelled with ¹⁰⁹Cd radiotracer as cadmium chloride via drinking mineral water and 11 unlabelled via food for 2 years. The diet was characterized in its metal content by neutron activation analysis to obtain the total dietary intake of different elements.The kidney was found to be the tissue with the major concentration of cadmium which accumulated continuously during the experiment.The variation of the accumulation pattern of Cd concentration in the liver and intestine indicated an initial rapid increase of Cd during the first 100 days. After this period an apparent equilibrium was attained in both these tissues until the end of the study.The intracellular distribution of cadmium in kidneys, liver, intestine and pancreas were similar, the cytosol fractions containing about 80% of the cellular cadmium. Dialysis experiments indicated that significant amounts of cadmium were able to be associated with cellular organelles, the mitochondria representing the most important organelle capable of binding cadmium.The cytoplasmatic Cd-profiles obtained at various stages of the experiment showed that the metal was only bound to a low-molecular-weight component, cadmium-binding protein (CdBP), which represents the specific cellular-binding component for cadmium under the long term-low level exposure (LLE) conditions.No significant variations in the concentrations of the elements in different organs were observed in animals supplemented with ¹⁰⁹Cd in respect to ¹⁰⁹Cd untreated controls.     

Shifting balances in U.S. metropolitan and nonmetropolitan area growth

"This paper assesses some of the recent attempts to explain the perceived growth reversal between metropolitan and nonmetropolitan areas in the United States during the 1970s. The paper argues that the reversal in population trends was not a one-time, radical shift in settlement trends, but rather the result of more continuous underlying industrial trends. Indeed, since 1979, population growth has again become faster in metropolitan than nonmetropolitan areas." The paper includes three sections. Regional and area population and industrial earnings growth patterns are first summarized for the 1960s, 1970s, and 1980s. Theories of polarization and polar reversal are then evaluated and found to be inadequate. Finally, a reconstruction of the neoclassical model is proposed.     

Reaction processes effecting the analysis of chloroform by direct aqueous injection gas chromatography

Several important reaction processes which influence the analysis of chloroform by direct aqueous injection (DAI) gas chromatography have been identified through an investigation of the chlorination reactions of humic acid and a series of simple polyhydroxyaromatic and diketone model compounds in dilute solution. The reaction of chlorine with each substrate system was studied over the pH range 2–12. Gas chromatographic analysis by the DAI and organic solvent liquid-liquid extraction (LLE) procedures gave different measurements for the yield of CHCl₃ depending on the pH of the reaction solution and the chemical structure of the substrate. Under acidic and neutral conditions, a variety of trichloromethyl-substituted intermediates were identified at high concentrations in addition to chloroform by GC/MS. Chloral hydrate, trichloroacetic acid, pentachloroacetone and hexachloroacetone undergo hydrolysis and/or decarboxylation to form CHCl₃ at the high injection port temperatures employed in aqueous injection GC analysis. The results obtained in the current study indicate that the decomposition of these and structurally-related species accounts for differences previously observed upon application of the DAI and either the LLE or purge-and-trap techniques for the determination of CHCl₃ in chlorinated natural waters.