Mashal Kholoud, Harsh James B, Flury Markus, Felmy Andrew R, Zhao Hongting
Department of Crop and Soil Sciences, Center for Multiphase Environmental Research, Washington State University, Pullman, Washington 99164-6420, USA.
Environ Sci Technol. 2004 Nov 1;38(21):5750-6. doi: 10.1021/es0349709.
Solutions of high pH, ionic strength, and aluminum concentration have leaked into the subsurface from underground waste storage tanks atthe Hanford Reservation in Washington State. Here, we test the hypothesis that these waste solutions alter and dissolve the native minerals present in the sediments and that colloidal (diameter < 2 microm) feldspathoids form. We reacted Hanford sediments with simulated solutions representative of Hanford waste tanks. The solutions consisted of 1.4 or 2.8 mol/kg NaOH, 0.125 or 0.25 mol/kg NaAlO4, and 3.7 mol/kg NaNO3 and were contacted with the sediments for a period of 25 or 40 days at 50 degrees C. The colloidal size fraction was separated from the sediments and characterized in terms of mineralogy, morphology, chemical composition, and electrophoretic mobility. Upon reaction with tank waste solutions, native minerals released Si and other elements into the solution phase. This Si precipitated with the Al present in the waste solutions to form secondary minerals, identified as the feldspathoids cancrinite and sodalite. The solution phase was modeled with the chemical equilibrium model GMIN for solution speciation and saturation indices with respect to sodalite and cancrinite. The amount of colloidal material in the sediments increased upon reaction with waste solutions. At the natural pH found in Hanford sediments (pH 8) the newly formed minerals are negatively charged, similar to the unreacted colloidal material present in the sediments. The formation of colloidal material in Hanford sediments upon reaction with tank waste solutions is an important aspect to consider in the characterization of Hanford tank leaks and may affect the fate of hazardous radionuclides present in the tank waste.
高pH值、离子强度和铝浓度的溶液已从华盛顿州汉福德保留地的地下废物储存罐渗入地下。在此，我们检验以下假设：这些废溶液会改变并溶解沉积物中存在的原生矿物，并形成胶体（直径<2微米）似长石。我们将汉福德沉积物与代表汉福德废物罐的模拟溶液进行反应。这些溶液由1.4或2.8摩尔/千克的氢氧化钠、0.125或0.25摩尔/千克的偏铝酸钠以及3.7摩尔/千克的硝酸钠组成，并在50摄氏度下与沉积物接触25或40天。从沉积物中分离出胶体尺寸部分，并对其矿物学、形态、化学成分和电泳迁移率进行表征。与罐式废溶液反应后，原生矿物将硅和其他元素释放到溶液相中。这种硅与废溶液中存在的铝沉淀，形成次生矿物，鉴定为似长石钙霞石和方钠石。使用化学平衡模型GMIN对溶液相进行建模，以确定溶液形态以及相对于方钠石和钙霞石的饱和指数。与废溶液反应后，沉积物中胶体物质的量增加。在汉福德沉积物中发现的天然pH值（pH 8）下，新形成的矿物带负电荷，类似于沉积物中未反应的胶体物质。汉福德沉积物与罐式废溶液反应后形成胶体物质，这是表征汉福德罐泄漏时需要考虑的一个重要方面，可能会影响罐式废物中存在的危险放射性核素的归宿。
