Field loss of activity from foliage

Field-loss rates have also been measured after dry deposition of particulate activity. Witherspoon Taylor (1970, 1971) and Peters Witherspoon (1972) used silicaceous particles, labelled with 134Cs, in three size ranges, 1-44 fim, 44-88 nm and 88-175 fim. Millard et al. (1983) used submicrometre particles labelled with 141Ce or 134Cs. All reported field loss as showing an initial rapid phase lasting a few days, followed by one or more slow phases. In the period from a few days to about five weeks after application of the activity, the values of XG were in the range 0.02-0.06 d-1, with no obvious correlation with particle size, or with the incidence of rainfall. 

Crop Nuclide No. of exps. Period of exps. (d) mean S.E. mean S.E. Reference 

If fallout of activity continues daily at a constant rate, the transfer factor from fallout to herbage, termed the Normalised Specific Activity by Chamberlain (1970), is 

If the simple relation between p and p (equation (2.7)) is assumed to hold, and the effect of dilution by growth of foliage is neglected 

more realistically, the biomass of the crop is assumed to increase linearly with time for T0 days, and fallout is constant over that period, then it is easily shown (Chamberlain, 1970) that 

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