Leachable 226Ra in Philippine phosphogypsum and its implication in groundwater contamination in Isabel, Leyte, Philippines.

Phosphogypsum (PG), the major waste material in phosphate fertilizer processing, has been known to contain enhanced levels of naturally-occurring radionuclides especially (226)Ra. The lack of radioactivity data regarding Philippine phosphogypsum and its environmental behavior in the Philippine setting has brought concern on possible contamination of groundwater beneath the phosphogypsum ponds in Isabel, Leyte, Philippines. The radioactivity of Philippine phosphogypsum was determined and the leaching of (226)Ra from phosphogypsum and through local soil was quantified. Level of (226)Ra in groundwater samples in Isabel, Leyte, Philippines was also quantified to address the primary concern. It was found that the (226)Ra activity in Philippine phosphogypsum is distributed in a wide range from 91.5 to 935 Bq/kg. As much as 5% of (226)Ra can be leached from Philippine PG with deionized water. In vitro soil leach experiments suggest that the soil in the phosphate fertilizer plant area would be able to deter the intrusion of (226)Ra into the water table. Compared to reported values of natural groundwater levels of (226)Ra, the concentration of this radionuclide in Isabel, Leyte groundwater suggest that there is no (226)Ra intrusion brought about by the presence of phosphogypsum ponds in the area.