THE DECOMPOSITION OF RADIOACTIVE ACETATE IN SOILS: II. THE DISTRIBUTION OF RADIOACTIVITY IN SOIL ORGANIC FRACTIONS

Abstract

Soils incubated with C14-labelled acetate for 6 to 9 hours showed that 22–30% of the acetate was oxidized to CO2. Fractionation of the soil revealed that the radioactivity of the remaining substrate was widely distributed in various fractions. Greatest activity was noted in the acid hydrolyzable humin fraction (50%) with lesser amounts (5–10%) being recovered in the fulvic acid and alcohol extract. Hymatomelanic acid, α-humus, and β-humus contained only traces of activity.Ion-exchange separation of the acid hydrolysate of the humin fraction indicated that a considerable portion of the activity was associated with an unidentified compound which had certain characteristics of itaconic acid. Radioactivity was also found to be present in the 15 amino acids identified.