Use of radiotracers in the study of the distribution of manganese and zinc in the ultrafiltrate fractions of fresh waters

Abstract

The distribution of manganese and zinc in the ultrafiltrate fractions of natural waters can be determined by spiking samples with radioisotopes prior to ultrafiltration, and determining the activity of the filtrate by gamma counting. This technique is very powerful when coupled with other methods of trace analysis. A comparison of the results obtained by gamma counting with those obtained by atomic absorption spectrometry showed that the optimum time interval between spiking and ultrafiltration was 2 h, indicating that this was the time required for equilibration between the stable and radioisotopes. This optimum time interval was unaffected by either chemical or physico-chemical transformations due to prior ageing. Sorption equilibria at the outer surface of natural colloids were considered to be the predominant processes determining the radioisotope and trace metal distributions.