Stability of Ferrihydrite–Humic Acid Coprecipitates under Iron-Reducing Conditions,Environmental Science & Technology

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Stability of Ferrihydrite–Humic Acid Coprecipitates under Iron-Reducing Conditions
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2018-11-08 , DOI: 10.1021/acs.est.8b03615
Jacqueline Mejia ₁ , Shaomei He _{2,

3} , Yu Yang ₄ , Matthew Ginder-Vogel ₁ , Eric E Roden ₂

Affiliation

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 H₂ or glucose as electron donors for DIR. H₂ 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 H₂-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.

中文翻译：

铁还原条件下水铁矿-腐植酸共沉淀物的稳定性

最近的研究表明，在异化氧化铁还原 (DIR) 过程中可能会释放与氧化铁 (氢) 氧化物结合的有机碳 (OC)。然而，在能够驱动 OC 代谢和 DIR 的天然微生物聚生体存在下，铁（氢）氧化物结合的 OC 的稳定性尚未得到解决。纯水铁矿 (Fhy) 和 Fhy-腐殖酸共沉淀物 (Fhy-HA) 用少量淡水沉积物接种，并在缺氧条件下在存在和不存在 H ₂或葡萄糖作为 DIR 的电子供体的情况下培养。H ₂提升的 DIR 导致了 ca 的释放。1 mM 溶解有机碳 (DOC)。然而，从纯 Fhy 和 Fhy-HA 中释放出相当数量的 DOC，类似于不含矿物质、仅接种物的对照中的 DOC 水平。这些结果表明，在 H ₂促进的 DIR期间观察到的 DOC 释放源自接种物中包含的 OC，而不是 Fhy-HA 中更大的 OC 库（约 38 mM）。因此，与与氧化铁共沉淀的高芳香 OC (HA) 相比，DIR 优先释放吸附的低芳香性 OC（接种物 OC）。我们的发现为 DIR 可能影响缺氧土壤和沉积物中水相/固相 OC 分配的程度和机制提供了新的见解。

更新日期：2018-11-08

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