A field experiment on Rn flux from reclaimed uranium mill tailings.

Design and construction techniques are described for a 1.6 ha experimental reclamation plot consisting of a 1-m-thick slab of uranium mill tailings covered with various depths of overburden. A passive, activated charcoal device was developed and used for measurements of Rn flux at the soil surface. Observations on Rn flux vs overburden depth indicated that tailings covered with 1.5 m of revegetated or 0.3 m of bare overburden had Rn exhalation rates comparable to background. Vegetated subplots exhibited a significantly higher (often an order of magnitude) flux than the bare subplots. A positive correlation was observed between precipitation quantities and Rn flux.