Impact of soil water erosion processes on catchment export of soil aggregates and associated SOC

- Erosive events occurred in short duration and high intensity rainfall events.
- The sediments contained more fine and less coarse aggregates than the source soils.
- SOC content differed among different sizes aggregate fractions in the sediments.
- Soil erosion processes impact the aggregate size distribution and SOC enrichment.

Soil erosion is a complex process which causes loss of soil mineral material together with soil organic carbon (SOC). Little is known about the impact of soil water erosion on catchment exports of soil aggregates and associated SOC, especially at a small agricultural catchment. SOC delivered from a small catchment located in Northeast China was assessed for three erosive rainfall events in 2011. The quantity and size of the exported soil aggregates and their concentration of SOC were assessed along with runoff rate, sediment loss and rainfall characteristics to further the understanding of SOC erosion and its potential fate. Aggregate size distribution in sediments was different from that in source soil and was significantly correlated to sediment concentration in runoff. Fine size aggregate fractions in the sediments were the most abundant. The SOC was enriched in the sediments and indicated a high selectivity of the erosion processes. The SOC concentration differed among different sizes of aggregate fractions with coarse size aggregate fractions generally having the largest concentration. We concluded that the soil water erosion processes impact the aggregate size distribution and SOC enrichment in the delivered sediment, which subsequently influence the catchment exports of SOC. Additional measurements over several rainy seasons are required to further quantify the impact of soil water erosion on catchment exports of soil aggregates and associated SOC.