Kim C S, Brown G E, Rytuba J J
Department of Geological & Environmental Sciences, Stanford University, CA 94305-2115, USA.
Sci Total Environ. 2000 Oct 16;261(1-3):157-68. doi: 10.1016/s0048-9697(00)00640-9.
Mining of mercury deposits located in the California Coast Range has resulted in the release of mercury to the local environment and water supplies. The solubility, transport, and potential bioavailability of mercury are controlled by its chemical speciation, which can be directly determined for samples with total mercury concentrations greater than 100 mg kg(-1) (ppm) using X-ray absorption spectroscopy (XAS). This technique has the additional benefits of being non-destructive to the sample, element-specific, relatively sensitive at low concentrations, and requiring minimal sample preparation. In this study, Hg L(III)-edge extended X-ray absorption fine structure (EXAFS) spectra were collected for several mercury mine tailings (calcines) in the California Coast Range. Total mercury concentrations of samples analyzed ranged from 230 to 1060 ppm. Speciation data (mercury phases present and relative abundances) were obtained by comparing the spectra from heterogeneous, roasted (calcined) mine tailings samples with a spectral database of mercury minerals and sorbed mercury complexes. Speciation analyses were also conducted on known mixtures of pure mercury minerals in order to assess the quantitative accuracy of the technique. While some calcine samples were found to consist exclusively of mercuric sulfide, others contain additional, more soluble mercury phases, indicating a greater potential for the release of mercury into solution. Also, a correlation was observed between samples from hot-spring mercury deposits, in which chloride levels are elevated, and the presence of mercury-chloride species as detected by the speciation analysis. The speciation results demonstrate the ability of XAS to identify multiple mercury phases in a heterogeneous sample, with a quantitative accuracy of +/-25% for the mercury-containing phases considered. Use of this technique, in conjunction with standard microanalytical techniques such as X-ray diffraction and electron probe microanalysis, is beneficial in the prioritization and remediation of mercury-contaminated mine sites.
对位于加利福尼亚海岸山脉的汞矿进行开采，已导致汞释放到当地环境和供水系统中。汞的溶解度、迁移性和潜在生物有效性受其化学形态控制，对于总汞浓度大于100 mg kg⁻¹（ppm）的样品，可使用X射线吸收光谱法（XAS）直接测定其化学形态。该技术具有对样品无损、元素特异性、在低浓度下相对灵敏且所需样品制备最少等额外优点。在本研究中，收集了加利福尼亚海岸山脉多个汞矿尾矿（煅烧物）的Hg L(III)边扩展X射线吸收精细结构（EXAFS）光谱。所分析样品的总汞浓度范围为230至1060 ppm。通过将来自异质、焙烧（煅烧）尾矿样品的光谱与汞矿物和吸附汞络合物的光谱数据库进行比较，获得了形态数据（存在的汞相及其相对丰度）。还对已知的纯汞矿物混合物进行了形态分析，以评估该技术的定量准确性。虽然发现一些煅烧样品仅由硫化汞组成，但其他样品含有额外的、更易溶的汞相，这表明汞释放到溶液中的可能性更大。此外，在热泉汞矿床的样品（其中氯化物含量升高）与形态分析检测到的汞 - 氯物种的存在之间观察到了相关性。形态分析结果表明，XAS能够识别异质样品中的多种汞相，对于所考虑的含汞相，定量准确性为±25%。将该技术与标准微分析技术（如X射线衍射和电子探针微分析）结合使用，有利于对汞污染矿区进行优先排序和修复。
