Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA.
Environ Sci Technol. 2010 Jan 1;44(1):34-40. doi: 10.1021/es901577q.
Reductive dissolution of redox-sensitive minerals such as manganese (Mn) oxides in natural sediments is an important mechanism for trace element mobilization into groundwater. A gel probe sampler has been constructed to study in situ reductive dissolution of Mn oxides. The gel consists of a polyacrylamide polymer matrix doped with hydrous Mn oxide (HMO). Gel slabs are mounted into a probe, which is designed to be inserted into the sediments. The amount of Mn released from the gel by reductive dissolution is determined by comparing the amount of Mn initially embedded into the gel with the amount remaining in the gel after exposure to conditions in the sediments or, in laboratory studies, to reducing agents. In this laboratory study, the performance of the gel probes was examined using the model reductant ascorbate and the Mn-reducing bacteria Shewanella oneidensis strain MR-1. In addition, a 1-D model was used to relate the reaction rates observed for HMO embedded in gels to those for HMO in suspension. One limitation of the HMO-doped gels for assessing microbial reduction rates is that the gels prevent direct contact between the microbes and the HMO and hence preclude enzymatic reduction at the cell surface. Nonetheless, the HMO-doped gel probes offer the possibility to establish a lower bound for Mn-reduction capacity in sediments.
在自然沉积物中，氧化还原敏感矿物（如锰氧化物）的还原溶解是微量元素向地下水迁移的重要机制。已经构建了凝胶探针采样器来研究原位锰氧化物的还原溶解。该凝胶由掺杂水合锰氧化物 (HMO) 的聚丙烯酰胺聚合物基质组成。凝胶片被安装到探针中，该探针旨在插入沉积物中。通过比较初始嵌入凝胶中的锰量与暴露于沉积物条件或在实验室研究中与还原剂后的凝胶中剩余的锰量，可以确定凝胶还原溶解释放的锰量。在这项实验室研究中，使用模型还原剂抗坏血酸和锰还原细菌 Shewanella oneidensis 菌株 MR-1 检查了凝胶探针的性能。此外，还使用一维模型将嵌入凝胶中的 HMO 的观察到的反应速率与悬浮 HMO 的反应速率相关联。用于评估微生物还原率的 HMO 掺杂凝胶的一个限制是，凝胶阻止微生物与 HMO 直接接触，从而排除了细胞表面的酶还原。尽管如此，HMO 掺杂凝胶探针还是有可能确定沉积物中锰还原能力的下限。
