Transport of particulate matter in natural waters — modelling and in situ-measurements

The significant processes controlling the fate of particulates are convection an dispersion on one hand, and sedimentation on the other hand. Due to inteparticulated reactions, larger aggregates can be formed from smaller units thus changing the sedimentation characteristics. These phenomena are summarized in a mathematical model whereby hydrodynamic effects as well as the control mechanisms of the dissolved phase are included. A relationship was derived on the basis of energy considerations leading to the formulation of a critical sedimentation velocity of the suspensa, which determines the transport capacity of the flowing system. The sedimentation term is calculated from the above discussed transport capacity, hydro-dynamic parameters and suspending media properties. Aggregation effects are taken into account as an increase of sedimentation velocities of the particles. The equations are solved in a particular computational routine such that the horizontal distribution of suspended solids in a natural system can be describe as function of the above discussed phenomena. The model was tested with in situ-measurements. It was found that the observed processes are described satisfactorily by this model.     

Managing the urban environment in a developing country: The Ogunpa river channelization scheme in Ibadan City,Nigeria

A disastrous flood in Ibadan City, Nigeria in April 1978 aroused public interest in the Ogunpa river channelization scheme which had earlier been embarked upon by government. A questionnaire survey of 399 residents near the river was designed to examine three issues: (a) the losses sustained and the people's reaction to and perception of the causes of the flood; (b) their perception of the present and future uses of the river; and (c) their perception of the prospects of the channelization scheme.The results show that about 75% of the respondents were affected by the flood; 41% each lost property worth about N2960.00. Yet, many could not hope to move out of the flood zone mainly because of shortage of residential accomodation in the city. The factors given as being responsible for the flood were poor drainage, heavy rains, refuse disposal in the river, shallowness of the river channel and the unplanned layout of streets and buildings. Indeed, the major use of the river has been as a refuse dump, so that it is heavily polluted. Many respondents would like the river to be reclaimed to alleviate some of the socioeconomic problems confronting them. Recreational use of the river was not much considered. Majority of respondents thought the channelization scheme would bring some benefit. But, they are sceptical about its lasting impact unless it is done within the framework of a comprehensive programme of urban land management and protection and the improvement of living conditions in the city.     

Quality control in low-level radionuclide analysis. Results of recent intercomparisons and programmes for 1979/80 of the international atomic energy agency

The results of recent IAEA intercomparison programs are reviewed.     

NATURAL GAS PROSPECTS IN DEVELOPING COUNTRIES AND THE ROLE OF LNG TRANSPORTATION

Natural gas may provide a major contribution to the world energy supply during the next few decades. The developing countries command about 50 per cent of the world proved natural gas reserves, with gas accounting for only 6 per cent of commercial primary energy production. The challenging task of expanding gas production and utilization in the developing countries, especially through effective use of gas associated with petroleum deposits and transportation of gas in liquefied form (LNG), will require long-term technical co-operation policy commitments with regard to investment, manpower and the transfer of technology. The article is intended to analyse the basic factors involved in these problems. Au cours des prochaines décennies, le gaz naturel peut constituer un apport considérable à l'approvisionnement énergétique mondial. Les pays en développement détiennent approximativement 50 pour cent des réserves mondiales prouvées de gaz naturel, le gaz représentant seulement 6 pour cent de la production d'énergie primaire commerciale. Le défi lancé par la production et l'utilisation croissantes de gaz dans les pays en développement, particulièrement par l'utilisation efficace du gaz lié aux gisements de pétrole et le transport du gaz liquéfié (GNL), requiert des engagements à long terme en matière de politique de coopération technique dans le domaine des investissements, de la main-d'oeuvre et du transfert de technologie. Cet article a pour but d'analyser les facteurs fondamentaux à prendre en considération lorsqu'on traite de ces problèmes. El gas natural podría representar una gran contribucíon a la oferta mundial de energía dentro de las próximas décadas. Los países en desarrollo poseen cerca del 50 porciento de la reserva provada mundial de gas y solamente el 6 porciento de la producción primaria de energía comercial proviene del gas. La tarea de expandir la producción y utilización de gas en los países en desarrollo, especialmente ia utilización efectiva en forma líquida (LNG) de gas asociado al petróleo, requiere de compromisos de cooperación técnica a largo plazo en lo referente a inversiones, recursos humanos y transferencia de tecnología. Este artículo intenta analizar los factores básicos pertinentes a dicha tarea.