Fate and transport of radioactive gypsum stack water entering the Floridan aquifer due to a sinkhole collapse.
Fate and transport of radioactive gypsum stack water entering the Floridan aquifer due to a sinkhole collapse.
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DOI：
10.1038/s41598-018-29541-0
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发表时间：
2018-07-30
影响因子：
4.6
通讯作者：
Wang D
中科院分区：
文献类型：
--
作者：
Sandhu D;Singh A;Duranceau SJ;Nam BH;Mayo T;Wang D
地下水含水层是饮用水的重要来源，必须加以保护以免受到污染。来自磷矿加工的磷石膏堆含有少量的放射性核素，如226Ra。2016年9月，位于佛罗里达州中部碳酸盐岩溶地形下的磷石膏堆下的一个天坑坍塌，该地区的含水层主要受到限制，引发了对附近地区水质的担忧。监测和模拟污染羽流的运输对于确保达到饮用水标准和改进有关处理的决策至关重要。为了实现这一目标，使用PHREEQC软件进行地球化学建模，根据水力和水文条件研究羽流的轨迹。模拟了吸附作为一种可以进一步降低烟羽强度的去除机制。通过模拟多种情景，包括可变的放射性核素泄漏量，对含水层对坍塌堆中污染水释放的反应进行了量化。结果表明，放射性核素浓度可能需要11-17年的时间和5.2 - 8.3公里的距离才能降低到以前的水平。佛罗里达含水层中矿物（如水合铁、碳酸盐）的吸附效应可以将放射性核素迁移时间缩短到9-16年，距离天坑泄漏点4.3 - 7.8公里。它还可以缩短降低放射性核素浓度所需的距离，尽管效果并不显著。此外，由于土壤化学的复杂性，地下水修复的重要性被强调。
Groundwater aquifers are an essential source of drinking water, and must be protected against contamination. Phosphogypsum stacks originating from the processing of phosphate rock contain small amounts of radionuclides, such as 226Ra. In September 2016, a sinkhole located beneath a phosphogypsum stack collapsed under central Florida’s carbonate karst terrain, where the aquifer is mostly confined, raising concern over water quality in the regions nearby. Monitoring and modeling the transport of the contaminated plume is vital to ensure drinking water criteria are met and to improve decision making regarding treatment. To achieve this, a geochemical modeling using PHREEQC software was employed to investigate the trajectory of the plume based on hydraulic and hydrologic conditions. Adsorption was simulated as a removal mechanism that could further reduce the intensity of the plume. The aquifer’s response to the release of contaminated water from the collapsed stack was quantified by simulating a number of scenarios, including variable radionuclide leakage quantities. Results suggest that it may take between 11–17 years and between 5.2 to 8.3 km from the sinkhole leak to reduce radionuclide concentrations to previous levels. Coupling the adsorption effect by minerals in Floridan aquifer (e.g. ferrihydrite, carbonate) can reduce radionuclide migration time to 9–16 years and distances between 4.3 to 7.8 km from the sinkhole leak. It can also reduce the distance needed to lower radionuclide concentrations, though not significantly. Additionally, due to the complexities of soil chemistry, the importance of groundwater remediation is emphasized.
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