Saueia C H R, Mazzilli B P
Laboratório de Radiometria Ambiental, Instituto de Pesquisas Energéticas e Nucleares, CEP 05508 000, São Paulo, Brazil.
J Environ Radioact. 2006;89(3):229-39. doi: 10.1016/j.jenvrad.2006.05.009. Epub 2006 Jul 18.
The Brazilian phosphate fertilizer is obtained by wet reaction of igneous phosphate rock with concentrated sulphuric acid, giving as final product, phosphoric acid and dehydrated calcium sulphate (phosphogypsum) as by-products. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP) and diammonium phosphate (DAP). The phosphate rock used as raw material presents in its composition radionuclides of the U and Th natural series. Taking this into account, the main aim of this paper is to evaluate the fluxes of natural radionuclides and radioactive disequilibria involved in the Brazilian industrial process of phosphoric acid production; to determine the content of radioactivity in several commercial fertilizers produced by this industry; to estimate their radiological impact in crop soils and the long term exposure due to their application. Radiological characterization of phosphate rock, phosphogypsum and phosphate fertilizers was performed by alpha and gamma spectrometry. The fertilizer samples, which are derived directly from phosphoric acid, MAP and DAP, presented in their composition low activity concentrations for 226Ra, 228Ra and 210Pb. As for U and Th, the concentrations found in MAP and DAP are more significant, up to 822 and 850Bqkg(-1), respectively. SSP and TSP, which are obtained by mixing phosphoric acid with different amounts of phosphate rock, presented higher concentrations of radionuclides, up to 1158Bqkg(-1) for (238)U, 1167Bqkg(-1) for (234)U, 1169Bqkg(-1) for 230Th, 879Bqkg(-1) for 226Ra, 1255Bqkg(-1) for 210Pb, 521Bqkg(-1) for 232Th, 246Bqkg(-1) for 228Ra and 302Bqkg(-1) for 228Th. Long term exposure due to successive fertilizer applications was evaluated. Internal doses due to the application of phosphate fertilizer for 10, 50 and 100 years were below 1mSvy(-1), showing that the radiological impact of such practice is negligible.
巴西磷肥是通过火成磷矿石与浓硫酸的湿法反应制得的，最终产品为磷酸，副产品是脱水硫酸钙（磷石膏）。磷酸是生产重过磷酸钙（TSP）、过磷酸钙（SSP）、磷酸一铵（MAP）和磷酸二铵（DAP）的起始原料。用作原料的磷矿石在其成分中含有天然铀系和钍系放射性核素。考虑到这一点，本文的主要目的是评估巴西磷酸生产工业过程中涉及的天然放射性核素通量和放射性不平衡；确定该行业生产的几种商业肥料中的放射性含量；估计它们对作物土壤的放射性影响以及由于施用这些肥料而导致的长期暴露。通过α和γ能谱法对磷矿石、磷石膏和磷肥进行了放射性表征。直接由磷酸、MAP和DAP制成的肥料样品，其成分中226Ra、228Ra和210Pb的活度浓度较低。至于铀和钍，在MAP和DAP中发现的浓度更高，分别高达822和850Bqkg(-1)。通过将磷酸与不同量的磷矿石混合而获得的SSP和TSP，其放射性核素浓度更高，238U高达1158Bqkg(-1)，234U高达1167Bqkg(-1)，230Th高达1169Bqkg(-1)，226Ra高达879Bqkg(-1)，210Pb高达1255Bqkg(-1)，232Th高达521Bqkg(-1)，228Ra高达246Bqkg(-1)，228Th高达302Bqkg(-1)。评估了连续施肥导致的长期暴露。因施用磷肥10年、50年和100年而产生的内照射剂量低于1mSvy(-1)，表明这种做法的放射性影响可以忽略不计。
Zotero 插件