Enhancement of natural radioactivity in the surrounding of a phosphate fertilizer complex in Santos basin, Brazil

Phosphate deposits are generally characterised by enhanced radionuclides concentration compared to average natural levels. Mining and processing of phosphate ore redistribute radionuclides into final products, by-products and solid waste (phosphogypsum). The phosphate fertiliser complex located in Santos Basin, Southwest Brazil, produces approximately 2000 tons of phosphogypsum per day, which are stockpiled and presents a potential threat to the environment. The radiological environmental impact is mainly due to the presence of 226Ra, 228Ra and 210Pb. This study aims to determine these radionuclides in 13 sediment samples from Santos estuarine system in the surrounding of phosphate plants. As the organic debris is a good adsorbent of radionuclides, total organic carbon was also determined. 226Ra, 228Ra and 210Pb were measured by gamma spectrometry using a hiperpure Ge detector. The activity concentrations varied from 6±2 to 44±5 Bq/kg for 226Ra, from 8±3 to 77±6 Bq/kg for 228Ra and from