Micro-characteristics of soil aggregate breakdown under raindrop action

Raindrop splash is considered to be the first step in soil erosion, and it is also a contribution to such erosion. Aggregate breakdown due to raindrop splash causes crusting and soil erosion. In this study, the micro-characteristics of soil aggregate breakdown under the action of three sizes of raindrops were examined using synchrotron-based X-ray micro-computed tomography (SR-μ CT). The results showed that soil aggregate breakdown was related to the size of raindrops, was mainly caused by large raindrops during a rainfall event, and formed an enrichment zone, transition zone, and dense airtight zone of aggregates in the surface soil. The shape index and the amount of aggregate in the splashed soil was higher than in the un-splashed soil, especially for micro-aggregate fragments (< 25 μm). We confirm that the existence of large amounts of micro-aggregate fragments surrounding large aggregates in a rainfall event is a principle factor in the formation of soil surface seals and the clogging of pores.