Soil organic carbon (SOC) could be enriched in sediments for rain-induced overland flow. However, the features of the enriched SOC distribution in each size of sediment particles and the effect of aggregate breakdown on SOC enrichment features have not been completely investigated. Thus, the SOC concentration of different sizes of sediment aggregates was tested for all samples obtained for 27 simulated rainfall experiments conducted with 5°, 10°, and 15° gradients at rainfall intensities of 45, 90, and 120 mm h⁻¹, respectively. The changes of SOC composition in aggregates from the original soil to sediments were estimated through the ratios of the variation percentage of the effective and dispersed each size of class sediment particle to that of the original soil particles (Ap). The contribution percentage of aggregate breakdown to the SOC enrichment in sediments (Ca) was also quantified. Results showed that Ca was above 50 % even when under an extremely high rainfall intensity of 120 mm h⁻¹ on a 15° slope, but Ca decreased with the increase in overall rainfall intensity and slope. When the soil erosion rate is not high enough, Ca decreases with time because of the increase in the soil erosion rate. The absolute values of Aps of all size class particles were increased with the rainfall intensity and slope. However, the absolute values of Aps of clay- or fine silt-sized class particles changing between 0.11 and 0.68 were generally lower than those of coarse silt, fine sand, and coarse sand changing from −3.11 to 1.38, −0.35 to 0.06, and −1.3 to 0, respectively. This result indicates that 0.05–0.25-mm aggregates were more easily broken than other size particles, and the different sizes of particulate organic carbon chippings were more preferred transport than clay/silt-bonded aggregate fragments. The preferred transport of large amounts of 0.25–2-mm-size particulate organic carbon resulted in higher SOC enrichment ratios (ERocs) of 2.58 in 0.25–2-mm particle size class than others. The preferred transport of light particles, for example, mineral-associated and particulate organic carbon chippings exposed by aggregate stripping, caused the uneven enrichment of SOC in sediments. Last, a significantly negative correlation is observed among the mean weight diameter, the enrichment ratio (Er) of each size class particles in sediments, and Ca and ERocs of sediments (P < 0.05). If the rainfall intensity and slope are small, then many aggregates will be broken, and the uneven enrichment of SOC will be enhanced. Overall, our research provides an important reference to further understand the SOC loss mechanisms of soil aggregate induced by water erosion.

土壤有机碳（SOC）可能会因降雨引起的陆上径流而富集在沉积物中。然而，尚未完全研究沉积物中每种尺寸的富集SOC的分布特征以及聚集体分解对SOC富集特征的影响。因此，不同大小的沉积物聚集体的SOC浓度用于与5进行27个模拟降雨实验获得的所有样品测试°，10°，和在45，90降雨强度15°的梯度，和120毫米高^-1分别。通过有效和分散的各类沉积物颗粒大小与原始土壤颗粒（Ap）的变化率之比，估算了聚集体中SOC从原始土壤到沉积物的变化。）。还确定了聚集体分解对沉积物中SOC富集的贡献百分比（Ca）。结果表明，即使在15°坡度下120mm h ^-1的极高降雨强度下，Ca仍高于50％，但是Ca随着总降雨强度和坡度的增加而降低。当水土流失速率不够高时，由于水土流失速率的增加，Ca随时间减少。随着降雨强度和坡度的增加，各种粒径颗粒的Aps绝对值均增加。但是，Aps的绝对值在0.11到0.68之间变化的粘土或细粉尘大小的颗粒通常分别低于从-3.11到1.38，-0.35到0.06和-1.3到0的粗粉砂，细砂和粗砂的颗粒。该结果表明，与其他尺寸的颗粒相比，0.05-0.25-mm的聚集体更容易破碎，并且与粘土/淤泥粘结的聚集体碎片相比，不同尺寸的有机碳碎屑更易于运输。优先运输大量0.25–2毫米大小的颗粒状有机碳会导致更高的SOC富集率（ERocs）在0.25–2毫米粒度等级中为2.58）。轻质颗粒的首选运输方式，例如通过骨料剥离暴露的矿物相关颗粒有机碳碎片，导致沉积物中SOC的富集不均匀。最后，在平均重量直径，沉积物中每个尺寸类别颗粒的富集率（Er）与沉积物的Ca和ERocs之间观察到显着的负相关（P <0.05）。如果降雨强度和坡度较小，则许多聚集体将破碎，并且SOC的不均匀富集将增强。总体而言，我们的研究为进一步了解水蚀引起的土壤团聚体的SOC损失机理提供了重要参考。