Amorphous iron oxides protect aggregate-associated organic carbon from microbial utilization and decomposition evidenced from the natural abundance of 13C
Amorphous iron oxides protect aggregate-associated organic carbon from microbial utilization and decomposition evidenced from the natural abundance of 13C
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DOI：
10.1016/j.still.2022.105623
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发表时间：
2023-03
影响因子：
6.5
通讯作者：
Yu Tian;Shenggao Lu
中科院分区：
文献类型：
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作者：
Yu Tian;Shenggao Lu
氧化铁在通过吸附或共沉淀促进有机碳固存中起着关键作用。然而，氧化铁类型对团聚体相关有机碳稳定化的影响仍然知之甚少。研究了红壤（Ferrisol）土壤团聚体组分中结晶氧化铁（Fec）、无定形氧化铁（Feo）、δ13C和铁结合OC的分布。结果表明：微团聚体和粉砂+粘土组分的δ13C值显著低于宏团聚体和中团聚体（p< 0.05）；微团聚体和粉土+粘土组分中Feo和Fe-bound OC含量显著高于宏团聚体和小团聚体（p< 0.05）， Fec含量随团聚体粒径的增大而增加。在各团聚体组分中，Feo的摩尔比均高于Fec。FTIR光谱分析表明，多糖的OC官能团比例最高，且随团聚体粒径的增加而增加。芳香型碳/脂肪型碳的比值也随着骨料粒径的增大而增大。微团聚体和粉土+粘土组分中Feo和fe结合OC与δ13C值均呈显著负相关，而Fec与所有团聚体组分的δ13C值均无显著相关。此外，在所有团聚组分中，铁结合OC和铁结合OC与Feo呈正相关，与Fec呈负相关。本研究强调了Feo在团聚体相关有机碳固持中的重要性，并证实了微团聚体和粉土+粘土中的有机碳由于Feo的保护而较少被微生物利用的假设，从而限制了SOM的分子结构复杂性和芳香性。
Iron oxides play a critical role in promoting organic carbon sequestration through adsorption or co-precipitation. However, the effects of iron oxide types on the stabilization of aggregate-associated organic carbon are still poorly understood. We investigated the distribution of crystalline iron oxides (Fec), amorphous iron oxides (Feo), δ13C and Fe-bound OC in soil aggregate fractions of red earth (Ferrisol). The results showed that the δ13C values in microaggregate and silt+clay fractions were significantly lower than macro- and mesoaggregate (p< 0.05). The contents of Feo and Fe-bound OC in the microaggregate and silt+clay fractions were significantly higher than macro- and masoaggregate fractions (p< 0.05), while the content of Fec increased with the increase of aggregate size. The OC: Fe molar ratio of Feo was higher than Fec in all aggregate fractions. The FTIR spectroscopy analyses showed that polysaccharides had the highest proportion of all OC functional groups and increased with the increase of aggregate size. Likewise, the ratio of aromatic-C/aliphatic-C increased with the increase of aggregate size. Both Feo and Fe-bound OC had a significant negative correlation with δ13C values in microaggregate and silt+clay fractions, while Fec had no significant correlation with δ13C values in all aggregate fractions. Furthermore, the Fe-bound OC andfFe-bound OCwere positively correlated with Feo and negatively correlated with Fec in all aggregate fractions. This study highlighted the importance of Feo in the sequestration of aggregate-associated organic carbon and confirmed the hypothesis that the SOC in microaggregates and silt+clay underwent less cycles of microbial utilization due to the protection of Feo, thereby limiting the molecular structure complexity and aromaticity of SOM.