is deposited annually, then the total Sr* on the ground and in the air above Milford Haven, due to explosions since 1954, will be given very nearly by: X= 6.9 +52 (6) m It follows that the mean rate of injection over the past three years will be given by X) where: Xp = %4 (6.9 + 2.3/2) (7) If this rate of injection continues, the ground level concentration at a time t years after 1954 will be given by: Xp = 9 (1 — eM) X X — team U7e a VtAm)t ™) (8) The equilibrium value of X, to be reached in about 100 years time will be: Xy dh If X, _2.3+6.9 Am At+AM 3x(A + Am) m = 0.12, the equilibrium deposit of Sr®® derived from equation (9) is 290 mc/km/?. Tne rate of deposition at a time t after the beginning of 1954 is given by the expression: iagsetiaps ste which rises to an equilibrium value of AmX)/(A + Am). If Am = 0.12, the equilibrium value of 7.2 mc/km?/year will be reached in about twenty years time. It should perhaps be pointed out that this model is really only applicable to long-term extrapolation Since it is not consistent in detail with the observed pattern of deposition throughout the years 1954-1957. “ade 248