Department of Civil and Environmental Engineering , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.
Department of Geoscience , University of Wisconsin-Madison , Madison , Wisconsin 53706 , United States.
Environ Sci Technol. 2018 Nov 20;52(22):13174-13183. doi: 10.1021/acs.est.8b03615. Epub 2018 Nov 8.
Recent studies have suggested the potential for release of iron (hydr)oxide-bound organic carbon (OC) during dissimilatory iron oxide reduction (DIR). However, the stability of iron (hydr)oxide-bound OC in the presence of a natural microbial consortium capable of driving both OC metabolism and DIR has not been resolved. Pure ferrihydrite (Fhy) and Fhy-humic acid coprecipitates (Fhy-HA) were inoculated with a small quantity of freshwater sediment and incubated under anoxic conditions in the presence and absence of H or glucose as electron donors for DIR. H promoted DIR led to release of ca. 1 mM dissolved organic carbon (DOC). However, comparable amounts of DOC were released from both pure Fhy and Fhy-HA, similar to DOC levels in mineral-free, inoculum-only controls. These results suggest that the observed DOC release during H-promoted DIR originated from OC contained in the inoculum as opposed to the much larger pool (ca. 38 mM) of OC in the Fhy-HA. Thus, DIR preferentially released sorbed OC with low aromaticity (inoculum OC) versus highly aromatic OC (HA) coprecipitated with iron oxide. Our findings provide new insight into the extent and mechanisms by which DIR is likely to influence aqueous/solid-phase OC partitioning in anoxic soils and sediments.
最近的研究表明，在异化氧化铁还原（DIR）过程中，可能会释放出铁（氢）氧化物结合的有机碳（OC）。然而，在能够驱动 OC 代谢和 DIR 的天然微生物联合体存在的情况下，铁（氢）氧化物结合的 OC 的稳定性尚未得到解决。将少量淡水沉积物接种到纯水铁矿（Fhy）和 Fhy-腐殖酸共沉淀物（Fhy-HA）中，并在无氧条件下孵育，存在或不存在 H 或葡萄糖作为 DIR 的电子供体。H 促进 DIR 导致约 1mM 溶解有机碳（DOC）的释放。然而，从纯 Fhy 和 Fhy-HA 中释放出的 DOC 量相当，与无矿物质、仅接种物对照中的 DOC 水平相似。这些结果表明，在 H 促进的 DIR 过程中观察到的 DOC 释放源自接种物中的 OC，而不是 Fhy-HA 中更大的 OC 池（约 38mM）。因此，DIR 优先释放与氧化铁共沉淀的具有低芳香度（接种物 OC）的吸附 OC，而不是高度芳香的 OC（HA）。我们的研究结果为 DIR 可能影响缺氧土壤和沉积物中固/液相间 OC 分配的程度和机制提供了新的见解。
