160 Ra and U isotopes determination in phosphogypsum leachates by alpha-particle spectrometry J.L. Aguado a,* , J.P. Bolívar a , E.G. San Miguel a , R. García-Tenorio b a Departamento de Física Aplicada, Universidad de Huelva, Facultad de Ciencias Experimentales, 21007 Huelva, Spain b Departamento de Física Aplicada, Universidad de Sevilla, E.T.S. Arquitectura, Avda Reina Mercedes 2, 41012 Sevilla, Spain On-site studies have shown the radiological impact on the Tinto and Odiel rivers (SW of Spain) by the phosphogypsum produced as wastes in several phosphoric-acid industries lo- cated in this area. Leaching of natural radionuclides ( 226 Ra, 210 Po, 234 U, 238 U) from phospho- gypsum piles formed on the bank of the Tinto river has been identified as one of the main routes of radiological impact. The aim of this work was to study the 226 Ra and U-isotope leaching behaviour from phosphogypsum for a better understanding of the radiological im- pact caused in these aquatic systems. 1. Introduction Several factories located in Huelva (SW of Spain) are devoted to the production of phosphoric acid from sedimentary phosphate rocks by the so-called “wet process”: (1) Ca 10 (PO 4 ) 6 F 2 + 10H 2 SO 4 + 20H 2 O = 6H 3 PO 4 + 10CaSO 4 2H 2 O + 2HF. As a result of this process, the significant natural radioactivity associated with the phosphate rock (∼ 1000 Bq kg −1 of 238 U with its decay products) is fractionated between the phosphoric acid and the waste of the process, phosphogypsum. In fact, it has been estimated that 90% of the radium and polonium is fractionated to the phosphogypsum, while the majority of the uranium (> 60%) could be found in the phosphoric acid [1]. Since the middle of the 1960s, the phosphogypsum produced in these factories was man- aged as follows: the major part of the gypsum (80%) was transported from the factories with * E-mail address: aguado@uhu.es (J.L. Aguado). RADIOACTIVITY IN THE ENVIRONMENT © 2005 Elsevier Ltd. VOLUME 7 ISSN 1569-4860/DOI 10.1016/S1569-4860(04)07018-4 All rights reserved.