ESTIMATING AND ACCOUNTING FOR CS-137 SOURCE BURIAL THROUGH IN-SITU GAMMA-SPECTROMETRY IN SALT-MARSH ENVIRONMENTS

The use of in-situ gamma rag, spectrometry provides a means of rapidly estimating environmental radioactivity inventories. However, one of t he principal limitations of this technique has been the influence of v ariations in vertical activity distribution on the observed photon flu ence. This paper demonstrates that the quantification of the forward s cattered ratio of the spectrum (Q) can be used to. (i) estimate the me an mass depth (beta) of the vertical activity distribution within sedi ment profiles, and (ii) provide a calibration correction coefficient f or in-situ gamma spectrometry in environments which exhibit variable a nd non-exponential activity distributions, such as salt marshes around the Irish Sea. This paper presents a successful application of a spec trally derived calibration correction coefficient to insitu spectra fr om a salt marsh at Caerlaverock, Dumfries, SW Scotland, improving the correlation between soil core and in-situ derived activity estimates f rom r(2) = 0.097 (uncorrected) to r(2) = 0.801 (corrected). The scope for extending this approach to a wider, range of environments, to airb orne gamma spectrometry and to measurements of sedimentation rates is considered. Copyright (C) 1996 Elsevier Science Limited