Nuclide migration and the environmental radiochemistry of Florida phosphogypsum
Nuclide migration and the environmental radiochemistry of Florida phosphogypsum
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DOI：
10.1016/s0265-931x(00)00164-8
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发表时间：
2001-01-01
影响因子：
2.3
通讯作者：
Elzerman, AW
中科院分区：
文献类型：
--
作者：
Burnett, WC;Elzerman, AW
磷石膏是湿法磷酸生产过程中产生的一种废副产品，是佛罗里达州磷酸盐工业目前面临的最严重问题之一。这种副产品石膏在硫酸与磷矿的反应中沉淀下来，以每年约4000万吨的速度储存在佛罗里达州中部和北部的几个堆中。与这种材料有关的主要问题是天然铀系列放射性核素和其他杂质含量相对较高，可能对环境产生影响并妨碍其商业用途。我们通过以下方式研究了磷石膏可能释放的放射性核素：(i)分析与石膏堆有关的堆液、地下水和土壤；（二）地球化学模拟。观察到堆液中溶解铀和Pb-210的含量很高，只有中等浓度的Ra-226。下伏土壤倾向于富集U和Pb-210，表明酸性堆积流体进入缓冲环境时发生降水。模拟结果显示，放射性核素与硫酸盐和磷酸盐的配合物显著增加，导致堆内相对流动的不带电或带负电荷的溶液种类，随着堆下pH值的增加，可能会沉淀出多组分固体。因此，我们的证据表明，虽然磷石膏堆确实含有大量溶解的放射性核素，但去除机制似乎阻止了放射性核素大规模迁移到下面的含水层。2001爱思唯尔科学有限公司版权所有。
Phosphogypsum, a waste by-product derived from the wet process production of phosphoric acid, represents one of the most serious problems facing the phosphate industry in Florida today. This by-product gypsum precipitates during the reaction of sulfuric acid with phosphate rock and is stored at a rate of about 40 million tons per year on several stacks in central and northern Florida. The main problem associated with this material concerns the relatively high levels of natural uranium-series radionuclides and other impurities which could have an impact on the environment and prevent its commercial use. We have studied the potential release of radionuclides from phosphogypsum by: (i) analysis of stack fluids, groundwaters, and soils associated with gypsum stacks; and (ii) geochemical modeling. Stack fluids were observed to be very high in dissolved uranium and Pb-210 With only moderate concentrations of Ra-226. Underlying soils tend to be enriched in U and Pb-210 indicating precipitation when acidic stack fluids enter a buffered environment. Modeling results showed significant increases in radionuclide complexes with sulfate and phosphate, resulting in relatively mobile uncharged or negatively charged solution species within the stacks with likely precipitation of multicomponent solids with increasing pH below the stack. Our evidence thus suggests that, while phosphogypsum stacks do contain significant quantities of dissolved radionuclides, removal mechanisms appear to prevent large-scale migration of radionuclides to the underlying aquifer. (C) 2001 Elsevier Science Ltd. All rights reserved.