“…The 238 U decay-series may be uniformly distributed throughout the lattice structure of PG or can be bounded in separate, distinct mineral phases. Attempts have been made to identify the modes of occurrence of radionuclides in PG, in order to evaluate the availability of radionuclides ( 226 Ra, 210 Pb and 232 Th), rare-earth elements and Ba to the aquatic system under the influence of the stacks and its source materials based on sequential extraction methods (Tessier et al, 1979;Miller and Sutcliffe, 1984;Rutherford et al, 1995b;Boliver et al, 1996;Burnett et al, 1999;Santos et al, 2006). Their conclusion, however, cannot be confirmed clearly, since the phosphate rock and the chemical process vary for different industries.…”