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.