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Samples of cloud and rain water, soil and vegetation were collected from sites at up to 847 m altitude on Great Dun Fell in northern England during the period 2–6 May 1986. Wet deposition is the dominant depositional process for 103Ru and the caesium isotopes, whilst dry deposition is much more important for 131I. The observed deposition velocity for 131I is 3·4 mm s−1. The patchy distribution of activity is related to the convective nature of the rainfall, and there is evidence of direct deposition of contaminated orographic cloud water at the highest site.

The distribution and behavior of Cs in the soil-plant systems at some upland sites in Northeastern Italy, Scotland, and Norway have been investigated. From the limited range of samples taken, there appears to be no dominant physicochemical control on the plant availability of Cs. The presence of micaceous minerals or illitic clays does not significantly inhibit Cs uptake, either because of recycling in the organic surface horizons or because of clay-organic complex formation. Lower plants (bryophytes and lichens) show the highest Cs accumulation. Of the higher plants, ericaceous species take up Cs more than the others.

Radionuclides in the environment come from a wide range of sources, some natural and some artificial. Their biogeochemical behaviour is influenced both by their own physico-chemical properties and by those of the soil with which they interact. The source of the radionuclides is important, as are any changes in physico-chemical characteristics that occur during transport and deposition. Once in the soil further reactions can occur as the radionuclides equilibrate. These include immobilization by ion exchange and precipitation and remobilization by complexing and dissolution. Land management and environmental changes that alter conditions in the soil result in changes in the interactions of radionuclides with the soil and thereby to changes in mobility in the soil.