Oxygen Flux: Field Measurement Using a Polarographic Recorder

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Abstract
O2 flux in waterlogged forest soils can be measured using the Pt microcathode technique. By automatically scanning a predetermined voltage range applied to each set of up to 24 microcathodes in turn, the instrument produces a set of polarograms from which a flux-derived current can be unambiguously determined. Examples of different types of polarogram are given and the degree of desaturation is indicated by the shape of the polarogram. The robust microcathodes are made of a hard Pt-Ir alloy cased in resin-impregnated glass fiber, the whole instrument being rugged, portable and capable of running unattended in adverse environments. Applied potential and scanning rate can be preselected, usually 0 to -500 mV at 33 mV min-1. Difficulty in extrapolating transient to steady state diffusion and the uncertainty associated with the exact cathodic process involved are discussed.