School of Environmental Studies, China University of Geosciences (Wuhan), 388 Lumo Road, Wuhan 430000, PR China; Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo N2L3G1, Ontario, Canada.
Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo N2L3G1, Ontario, Canada.
Sci Total Environ. 2019 Apr 20;662:915-922. doi: 10.1016/j.scitotenv.2019.01.148. Epub 2019 Jan 15.
A previous long-term microcosm experiment showed mercury (Hg) in the aqueous phase of contaminated sediment was effectively stabilized through the addition of biochar. The present study focuses on the application of synchrotron-related methods to evaluate the distribution and speciation of Hg in the biochar particles reacted for 235, 387, and 1030 days. The study provided more information on Hg stabilization mechanisms in addition to the information obtained by the previous studies. Confocal micro-X-ray fluorescence imaging (CMXRFI) and micro-X-ray fluorescence (micro-XRF) maps show that mercury co-exists with S, Cu, Fe, Mn, and Zn on the surface and inside the particles of biochar. Extended X-ray absorption fine structure (EXAFS) modeling shows that Hg is in an oxide form on the surface of an iron (hydro)oxide particle from fresh sediment and in Hg-sulfide forms in biochar samples. S X-ray absorption near-edge structure (XANES) analyses show that sulfide is present within the biochar particles. After amendment with biochars, a fraction of the Hg originally present in unstable forms (dissolvable, HgO, colloidal, nano, etc.) in the sediment was likely stabilized as less soluble Hg-sulfide phases on the surface or within the biochar particle. These results suggest Hg accumulation by the biochar particles renders it less potential for transport and bioavailability.
先前的长期微宇宙实验表明，通过添加生物炭可以有效地稳定污染沉积物水相中汞（Hg）。本研究重点应用同步辐射相关方法来评估反应 235、387 和 1030 天后生物炭颗粒中 Hg 的分布和形态。该研究除了提供先前研究获得的信息外，还提供了更多关于 Hg 稳定机制的信息。共焦微 X 射线荧光成像（CMXRFI）和微 X 射线荧光（micro-XRF）图谱表明，汞与 S、Cu、Fe、Mn 和 Zn 一起存在于生物炭颗粒的表面和内部。扩展 X 射线吸收精细结构（EXAFS）建模表明，Hg 在新鲜沉积物中铁（氢）氧化物颗粒的表面呈氧化物形式，在生物炭样品中呈 Hg-硫化物形式。S X 射线吸收近边结构（XANES）分析表明，硫化物存在于生物炭颗粒内。在添加生物炭后，沉积物中原先以不稳定形式（可溶解的、HgO、胶体、纳米等）存在的一部分 Hg 可能在表面或生物炭颗粒内稳定为更难溶解的 Hg-硫化物相。这些结果表明，生物炭颗粒对 Hg 的积累使其更不易迁移和具有生物利用性。
