Characterisation of the microbial biomass in lignite-containing mine soilsby radiocarbon measurements

A method of sample preparation is presented which allows for the characteri sation of the soil microbial biomass by C-14 activity measurements at natur al abundance of C-14. By the use of freeze-drying instead of chloroform for the disruption of microbial cells, the possible contamination of the sampl e by C-14 is avoided. Our data show a close relationship between the two me thods. After extraction by CaCl2 the C-14 activity of the freeze-dried labi le carbon was recorded by accelerator mass spectrometry. Our data for ligni te-containing mine soils indicate that lignite carbon which does not show C -14 activity is incorporated in the soil microbial biomass. The method can thus be used to follow microbial degradation of fossil carbon (e.g. lignite ) in soil. (C) 2001 Elsevier Science Ltd. All rights reserved.