Key Laboratory of Groundwater Quality and Health (China University of Geosciences), Ministry of Education, Wuhan 430078, China.
School of Environmental Studies, China University of Geosciences, Wuhan 430078, China.
Environ Sci Technol. 2024 Jun 4;58(22):9840-9849. doi: 10.1021/acs.est.4c01135. Epub 2024 May 22.
The biogeochemical processes of iodine are typically coupled with organic matter (OM) and the dynamic transformation of iron (Fe) minerals in aquifer systems, which are further regulated by the association of OM with Fe minerals. However, the roles of OM in the mobility of iodine on Fe-OM associations remain poorly understood. Based on batch adsorption experiments and subsequent solid-phase characterization, we delved into the immobilization and transformation of iodate and iodide on Fe-OM associations with different C/Fe ratios under anaerobic conditions. The results indicated that the Fe-OM associations with a higher C/Fe ratio (=1) exhibited greater capacity for immobilizing iodine (∼60-80% for iodate), which was attributed to the higher affinity of iodine to OM and the significantly decreased extent of Fe(II)-catalyzed transformation caused by associated OM. The organic compounds abundant in oxygen with high unsaturation were more preferentially associated with ferrihydrite than those with poor oxygen and low unsaturation; thus, the associated OM was capable of binding with 28.1-45.4% of reactive iodine. At comparable C/Fe ratios, the mobilization of iodine and aromatic organic compounds was more susceptible in the adsorption complexes compared to the coprecipitates. These new findings contribute to a deeper understanding of iodine cycling that is controlled by Fe-OM associations in anaerobic environments.
碘的生物地球化学过程通常与有机质（OM）和含水层系统中铁（Fe）矿物的动态转化有关，而有机质与 Fe 矿物的结合进一步调节了这些过程。然而，有机质在碘在 Fe-OM 结合物上的迁移中的作用仍知之甚少。基于批吸附实验和随后的固相特征描述，我们研究了在厌氧条件下，不同 C/Fe 比的 Fe-OM 结合物对碘酸盐和碘化物的固定和转化。结果表明，C/Fe 比（=1）较高的 Fe-OM 结合物对碘具有更大的固定能力（碘酸盐约为 60-80%），这归因于碘对 OM 的更高亲和力和相关 OM 显著降低的 Fe(II)催化转化程度。与富氧、高不饱和的有机化合物相比，贫氧、低不饱和的有机化合物更优先与水铁矿结合；因此，结合的 OM 能够结合 28.1-45.4%的活性碘。在可比的 C/Fe 比下，与共沉淀相比，吸附复合物中碘和芳香族有机化合物的迁移更易发生。这些新发现有助于深入了解受厌氧环境中 Fe-OM 结合物控制的碘循环。
