Positive ¹⁴C gradients have recently been observed within the surface mixed layer of several continental-margin sediments. The best explanation for these positive ¹⁴C gradients is the occurrence and rapid degradation of labile organic carbon (LOC) in the upper 5–10 cm of the seabed. Based on a two-component model for sedimentary organic matter (i.e., a planktonic labile component and an older refractory component), bulk ¹⁴Corg data were used to determine the abundances of LOC within the surface mixed layers of three cores from the West Antarctic Peninsula (WAP) shelf and one core from San Clemente Basin (California Borderland). LOC contents in surface samples from the four stations varied from 0.5 to 1.1 mg/cm³, comprising 20% (San Clemente Basin) to 80% (WAP, Sta. G) of the total organic carbon. By incorporating a steady state diagenetic model and particle-mixing bioturbation coefficients, the LOC profiles were used to determine LOC turnover times (LOC τ) and LOC e-folding depths. The LOC τ values for the West Antarctic Peninsula sediments varied from 0.09 to 0.59 years, whereas the LOC τ value from the San Clemente Basin core was 63 years. The LOC e-folding depths for the WAP stations varied from 0.8 to 3.4 cm, in contrast to the LOC e-folding depth in San Clemente Basin, which was 4.0 cm. LOC characteristics from the four cores examined in this study were compared to LOC data in the literature as a means of substantiating the overall ¹⁴C_org-based approach and justifying model assumptions.

中文翻译：

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使用放射性碳评估海洋沉积物中不稳定有机碳的丰度、分布和性质

最近在几个大陆边缘沉积物的表面混合层中观察到正的¹⁴ C 梯度。对这些正¹⁴ C 梯度的最佳解释是海床上部 5-10 厘米不稳定有机碳 (LOC) 的发生和快速降解。基于沉积有机质的双组分模型（即浮游不稳定组分和较老的难降解组分），使用大量¹⁴ Corg 数据确定了南极半岛西部三个岩心表面混合层内 LOC 的丰度(WAP) 架子和一个来自圣克莱门特盆地（加利福尼亚边境）的岩心。来自四个站点的地表样品的 LOC 含量从 0.5 到 1.1 mg/cm ^{3 不等}, 占总有机碳的 20% (San Clemente Basin) 至 80% (WAP, Sta. G)。通过结合稳态成岩模型和颗粒混合生物扰动系数，LOC 剖面用于确定 LOC 周转时间 (LOC τ ) 和 LOC e 折叠深度。南极半岛西部沉积物的 LOC τ值从 0.09 到 0.59 年不等，而圣克莱门特盆地核心的 LOC τ值为 63 年。WAP 站点的 LOC e 折叠深度从 0.8 到 3.4 厘米不等，而圣克莱门特盆地的 LOC e 折叠深度为 4.0 厘米。本研究中检查的四个岩心的 LOC 特征与文献中的 LOC 数据进行了比较，作为证实总体¹⁴基于C_组织的方法和证明模型假设的合理性。