ABSTRACT

For the purpose of the nondestructive measurements of hazardous heavy-element-containing substances in soil samples, the emerging technique, triple-exposure X-ray computed tomography (CT), is proposed. The use of triple exposure (i.e. three different acceleration voltages for the X-ray tube) improves the accuracy of the identification of the atomic number of a heavy element. With lead as the target element, virtual X-ray microtomography simulations utilizing a polychromatic X-ray source accelerated at 70, 100, and 140 kV were performed. CT images for the three voltages were reconstructed on a computer for clayey soil samples with heavy-element-containing natural minerals, namely galena (PbS), witherite (BaCO₃), stibnite (Sb₂S₃), sphalerite (ZnS), and magnetite (Fe₃O₄). Quantitative analysis of the reconstructed CT images was performed to obtain the following results. (i) Galena can be distinguished from other heavy minerals (i.e. witherite, stibnite, sphalerite, and magnetite). (ii) The lead content in the clayey soil can be estimated with reasonable accuracy. These successful results demonstrate that the triple-exposure CT technique is promising for the nondestructive characterization of soil samples contaminated with hazardous heavy elements such as lead.

摘要

为了对土壤样品中的有害重元素物质进行无损测量，提出了一种新兴技术，即三次曝光 X 射线计算机断层扫描 (CT)。使用三次曝光（即 X 射线管的三种不同加速电压）提高了重元素原子序数识别的准确性。以铅为目标元素，利用在 70、100 和 140 kV 下加速的多色 X 射线源进行虚拟 X 射线显微断层扫描模拟。三种电压的 CT 图像在计算机上重建，用于含重元素天然矿物的粘土样品，即方铅矿 (PbS)、毒重石 (BaCO ₃ )、辉锑矿 (Sb ₂ S ₃)、闪锌矿 (ZnS) 和磁铁矿 (Fe ₃ O ₄ )。对重建的 CT 图像进行定量分析以获得以下结果。(i) 方铅矿可以与其他重矿物（即毒重石、辉锑矿、闪锌矿和磁铁矿）区分开来。(ii) 粘土中的铅含量可以合理准确地估计。这些成功的结果表明，三次曝光 CT 技术有望用于对受铅等危险重元素污染的土壤样品进行无损表征。