Methodological development for combined analysis of S and 35S in a Scots pine forest study

A study of sulphur movement through a Scots pine forest involved the analysis of S and 35S in rainfall, throughfall and stem flow solutions, and aqueous extracts of needles and soil, together with measurement of total levels in soil and needles. Solution preparation procedures were developed so that the solutions could be used for liquid scintillation counting, ion chromatography and ICP/OES instrumental methods, ie., it was possible to analyse stable and radioactive sulphur fractions on the same sample solutions. Counting efficiency of the beta radiation from 35S in the study solutions ranged from 10 to 80%, with the greatest quenching occurring in soil nitric acid digestion solutions. A single non‐linear mathematical relationship was applied to correct the beta counts for energy quenching in all solutions with minimal bias when compared to the values derived from using separate factors for each solution type.