明确盐沼土壤有机碳汇的稳定性对于科学评估海岸带“蓝碳”的碳汇潜力具有重要意义，而土壤有机质的结构组成与土壤有机碳汇的稳定性密切相关。选择长江口崇明岛东部4个成陆年代迥异的围垦区，利用固态¹³C核磁共振技术研究钻探取得的埋藏盐沼以及钻孔周边的林地表层土壤样品的有机质结构特征，揭示土壤有机质更新过程中有机质结构组成的变化。结果表明：\mathrm{①}不同年代围垦区土壤有机碳官能团由表层到深层的变化特征类似，自表层的林地土壤样品至埋藏的盐沼样品，烷基碳与芳香碳的含量增加，而烷氧碳与羰基碳的含量降低。埋藏盐沼样品的烷基碳/烷氧碳含量值、芳香度与疏水碳/亲水碳含量值均大于钻孔周边林地表层土壤样品。随着埋藏深度增加，土壤有机质化学结构稳定性增强。\mathrm{②}自西向东林地表层土壤样品烷基碳/烷氧碳含量值、芳香度、疏水碳/亲水碳含量值均小于1，呈逐渐增长趋势；脂肪族/芳香族含量的值则逐渐降低。自西向东林地表层土壤样品有机质整体分解程度较低，但呈逐渐提高趋势，有机质稳定性逐渐增强。这与树木种植时间由西向东逐渐变早，表层土壤发育时间变长有关。\mathrm{③}自东向西，埋藏盐沼样品有机碳官能团含量与比值的变化表明，随着成陆时间延长土壤有机质稳定性不断增强。综上所述，随着成土时间延长，盐沼土壤有机质分解程度不断提高，有机质中结构稳定的组分所占的比例不断增加，易分解组分的比例不断降低，土壤有机质的稳定性不断提高。运用固态¹³C核磁共振技术研究长江口不同年代围垦区土壤有机质化学结构组成的变化，为揭示土壤碳汇稳定性的时间趋势及其化学机制提供了重要依据。

Clarifying the stability of salt marsh soil organic carbon sinks is of great significance when scientifically evaluating the carbon sink potential of “blue carbon” in coastal zones. The chemical structure and composition of Soil Organic Matter (SOM) are closely related to the stability of soil organic carbon sinks. This study focused on four reclamation areas with different construction times in the eastern part of Chongming Island, China. Solid-state ¹³C Nuclear Magnetic Resonance (¹³C NMR) was used to investigate the characteristics of SOM chemical structures in buried salt marsh samples obtained by drilling and topsoil samples acquired from woods around the drilling cores (CM2, CM4, CM5, and CM6). The purpose of this study was to elucidate the variations in the chemical structure of SOM during its turnover. The results showed that \mathrm{①} the variations in soil organic carbon functional groups from the surface to the deep layers exhibited similar trends for the four reclamation areas, despite different construction times. The alkyl carbon and aromatic carbon proportions showed an increasing trend whereas those of alkoxy carbon and carbonyl carbon showed a decreasing trend from the topsoil samples to the buried soil samples. The alkyl carbon/alkoxy carbon, aromaticity, and hydrophobic carbon/hydrophilic carbon of the buried salt marsh soil samples were greater than those of the topsoil samples in the woods around the drilling cores. The stability of the SOM chemical structure increased with burial depth. \mathrm{②} From west to east, alkyl carbon/alkoxy carbon, aromaticity, and hydrophobic carbon/hydrophilic carbon were all less than 1 and showed a gradually increasing trend, but aliphatic carbon/aromatic carbon gradually decreased in the topsoil samples in the woods around the drilling cores. The overall decomposition degree of organic matter in topsoil samples from the woods was low and showed a gradually increasing trend from west to east, which meant that SOM stability gradually improved. This was because the planting time for trees gradually became earlier and the development time for topsoil became longer in the woods from west to east. \mathrm{③} From east to west, the proportions and ratios of organic carbon functional groups in buried salt marsh samples showed that SOM stability increased with reclamation time. In summary, along with soil development, the decomposition degree of salt marsh SOM continued to improve, with an increasing proportion of refractory SOM components and a decreasing proportion of labile SOM components. In addition, SOM stability continued to increase. The changes in the chemical structure and composition of SOM in the reclamation areas, constructed in different years along the Yangtze River estuary, were studied using solid-state ¹³C NMR and the results improve understanding about the temporal trend and chemical mechanism underlying soil carbon sink stability.