SOILS AS SOURCE AND SINK OF PHOSPHINE

The evolution of free phosphine from soil samples collected from seven different areas in Germany was observed in laboratory experiments. Ph osphine emissions increased after additions of manure, glucose, format e, pyrogallol and sulphide, revealing a potential influence of microbi al activity on the liberation of phosphine. However, the concentration s decreased as time progressed. Soil samples exposed to phosphine remo ved the gas according to an exponential relationship. When Fe(III) was added to soil samples, phosphine removal was accelerated. The release of phosphine from soils to the atmosphere was concluded to be depende nt on a balance of natural generation and depletion processes. At ever y time ''matrix-bound'' phosphine, which constitutes a trace of this b alance, can be liberated by acid digestion of the soils. (C) 1997 Else vier Science Ltd.