Derivation of a grain-size proxy to aid the modelling and prediction of radionuclide activity in salt marshes and mud flats of the eastern Irish Sea

Analyses of radionuclide activity, particle size distribution, elemental composition and magnetic properties of saltmarsh and mudflat sediments from the eastern Irish Sea were undertaken in order to identify potential grain-size proxies which could aid long-term modelling of radionuclide activity in this area. Am-241 and Cs-137 concentrations were found to be highly dependent upon the presence of sediment finer than 5 phi, highlighting the need to utilize this fraction in preference to conventional normalization procedures which refer to the abundance of sediment finer than 4 phi. Analyses of potential grain-size proxies for radionuclide activity highlighted a similar grain-size association with respect to sediment magnetic properties. This was linked to the influence of organic carbon on microbial populations responsible for mineral magnetism. Regression analysis was employed to derive a method whereby radionuclide concentration can be predicted using magnetic data as a grain-size proxy, thereby facilitating the identification of spatial and temporal trends in activity data. (C) 1999 Academic Press.