Abstract
The usefulness of Instrumental Neutron Activation Analysis (INAA) when applied in bioenvironmental studies, has been demonstrated. Reactor neutrons were used for the activation of the samples involved. A number of methods for measuring the elemental concentrations, in a variety of materials, are available, but the comparative method has most often been employed by previous workers due to it's simplicity and the relatively low errors involved. Reference materials play an important role in the accuracy of the comparative method. When the elements of interest are not present with certified concentration values in the reference material involved while using the comparative method, other methods for the measurement of the elemental concentrations have to be adopted. Three other methods the absolute, the mono-standard and the K0- method, have been employed for determining the elemental concentrations in a variety of materials and their accuracies and associated errors have been compared with the comparative method. The usefulness of cyclic neutron activation analysis (CNAA) in determining short-lived radionuclides has also been demonstrated by measuring low levels of fluorine in human diet samples in the presence of major interfering elements. Significantly better precision and detection limits were achieved through CNAA as compared with the conventional irradiation method. Precise and accurate measurement of various elements by INAA require a sample size which is representative of the material to be analysed. The representative mass of a typical material can be evaluated by determining it's elemental sampling factors. The representative masses for a number of bioenvironmental materials have been evaluated. The benefits of mass fractionation in INAA of materials with large representative masses have also been explored. A significant improvement in the precision and detection limits for various elements was observed by using mass fractionation for the material to be analysed. An air pollution study was carried out in the industrial city of Lagos, Nigeria as a part of an EEC Linkage program on 'environmental monitoring and health impact assessment'. The elemental analysis of the air particulates, collected from three different locations in Lagos, was carried out by using INAA. Elemental characterization of the airborne particulates during the Harmattan season at two locations in Nigeria (Kano and Ife) has also been performed by using INAA. The sampling of air particulates from Kano, Ife and Lagos was carried out with the help of a cascade impactor air sampler, which made it possible to study the distribution of elemental concentrations with particle size. Scanning electron microscopy was also employed in order to study the shape and size distribution of the air particulates collected from Kano, Ife and Lagos. Twenty two elements were determined in Lagos air particulates and results have been compared with other industrial cities, Bombay and Toronto. Concentration values for twenty four elements determined in Harmattan dust are also presented. Calculation of enrichment factors and cluster analysis was applied to carry out source attribution.