In this paper an extensive study of the presence of natural radionuclides in a marshland area located in the vicinity of a phosphoric acid production complex in southwestern Spain is presented. This marsh is a natural reservation where significant biological activity takes place. The marsh is highly affected by the inflow of water from the Odiel river which is enhanced with natural radionuclides from industries which use phosphate rocks as raw material for fertilizer production. Sediment samples, collected from the intertidal zone, showed that wastes from the phosphate industries have resulted in enhanced radioactivities in the marsh.European Union (UE) FI3P-CT92003
