A COMPARATIVE-STUDY OF NEUTRON-ACTIVATION ANALYSIS AND PROTON-INDUCEDX-RAY-EMISSION ANALYSIS FOR THE DETERMINATION OF HEAVY-METALS IN ESTUARINE SEDIMENTS

Our work on heavy metals in the estuarine environment has involved the use of two multielement techniques: neutron activation analysis (NAA) and proton-induced X-ray emission (PIXE) analysis. As PIXE is essenti ally a surface analytical technique problems may arise due to sample i nhomogeneity and surface roughness. In order to assess the contributio n of these effects we have compared the results from PIXE analysis wit h those from a technique which analyzes a larger bulk sample rather th an just the surface. An obvious method was NAA. A series of sediment s amples containing particles of variable diameter were compared. Pellet s containing a few mg of sediment were prepared from each sample and a nalyzed by the PIXE technique using both an absolute and a comparitive method. For INAA the rest of the sample was then irradiated with ther mal neutrons and element concentrations determined from analyses of th e subsequent gamma-ray spectrum. Results from the two methods are disc ussed.