Rate-Temperature Curves as an Unambiguous Indicator of Biological Activity in Soil

Experiments are described in which we used a mass spectrometer to monitor O 2 uptake of enclosed soil samples as a function of temperature. We found that an Arrhenius plot of the rate of O 2 uptake showed pronounced local maxima attributable to biological activity, whereas similar plots of rates obtained with abiotic soils yielded straight lines. This procedure thus provides a basis for distinguishing biological from chemical activity for reactions, such as O 2 uptake, that can occur via either biological or chemical pathways.