ABSTRACT
Fluorescent polystyrene latex microspheres are utilised widely in biological and medical applications but they also offer potential as tracers of particle movement in the sub-surface. Microspheres, manufactured in a variety of sizes, are available dyed with any one of a number of fluorescent dyes. This allows several differently sized particles to be investigated simultaneously. Comparatively few investigations of their transport through geologic media have been reported but where they have been used they have been enumerated by epifluorescence microscopy to permit the calculation of their concentration in the aqueous phase. This procedure is both laborious and time consuming and provides no information on the disposition of the microspheres filtered or sorbed by the geologic matrix. A method has therefore been developed to allow a much more rapid and sensitive determination of the microsphere content in waters and in solid geologic matrices. It has proved useful in both laboratory column experiments and field investigations concerning migration. Two example applications of microspheres in hydrogeological investigations are described in the paper.
