Geology Department, Trier University, Campus II (Geozentrum), Behringstraße 21, 54296, Trier, Germany.
Soil Science Department, Trier University, Campus II (Geozentrum), Behringstraße 21, 54296, Trier, Germany.
Sci Rep. 2023 Feb 16;13(1):2818. doi: 10.1038/s41598-023-29727-1.
Redox-driven biogeochemical cycling of iron plays an integral role in the complex process network of ecosystems, such as carbon cycling, the fate of nutrients and greenhouse gas emissions. We investigate Fe-(hydr)oxide (trans)formation pathways from rhyolitic tephra in acidic topsoils of South Patagonian Andosols to evaluate the ecological relevance of terrestrial iron cycling for this sensitive fjord ecosystem. Using bulk geochemical analyses combined with micrometer-scale-measurements on individual soil aggregates and tephra pumice, we document biotic and abiotic pathways of Fe released from the glassy tephra matrix and titanomagnetite phenocrysts. During successive redox cycles that are controlled by frequent hydrological perturbations under hyper-humid climate, (trans)formations of ferrihydrite-organic matter coprecipitates, maghemite and hematite are closely linked to tephra weathering and organic matter turnover. These Fe-(hydr)oxides nucleate after glass dissolution and complexation with organic ligands, through maghemitization or dissolution-(re)crystallization processes from metastable precursors. Ultimately, hematite represents the most thermodynamically stable Fe-(hydr)oxide formed under these conditions and physically accumulates at redox interfaces, whereas the ferrihydrite coprecipitates represent a so far underappreciated terrestrial source of bio-available iron for fjord bioproductivity. The insights into Fe-(hydr)oxide (trans)formation in Andosols have implications for a better understanding of biogeochemical cycling of iron in this unique Patagonian fjord ecosystem.
铁的氧化还原生物地球化学循环在生态系统的复杂过程网络中起着不可或缺的作用，如碳循环、养分命运和温室气体排放。我们研究了南巴塔哥尼亚安第斯土壤酸性表土中流纹质火山灰中铁（氢）氧化物（转化）途径，以评估陆地铁循环对这一敏感峡湾生态系统的生态相关性。我们使用批量地球化学分析结合对单个土壤团聚体和火山灰浮岩的微观尺度测量，记录了从玻璃质火山灰基质和钛磁铁矿斑晶中释放铁的生物和非生物途径。在频繁的水文干扰控制下的连续氧化还原循环中，富铁水铁矿-有机质共沉淀物、磁赤铁矿和赤铁矿的（转化）与火山灰风化和有机质转化密切相关。这些铁（氢）氧化物在玻璃溶解后通过与有机配体络合，通过磁赤铁矿化或从亚稳前体溶解-再结晶过程形成，随后在玻璃溶解后形成。最终，赤铁矿代表在这些条件下形成的最热力学稳定的铁（氢）氧化物，并在氧化还原界面物理积累，而水铁矿共沉淀物代表了峡湾生物生产力中至今尚未被充分认识的陆地生物可利用铁源。对安第斯土壤中铁（氢）氧化物转化的认识对更好地理解这种独特的巴塔哥尼亚峡湾生态系统中铁的生物地球化学循环具有重要意义。
