Using real time particle tracking to understand soil particle movements during rainfall events

•Real time tracing of soil particles under simulated rainfall conditions•Sub-second and sub-millimeter accuracy in particle location•Visual and numerical data interpretation toolkit developed in Python

Very little is known about how individual soil particles move over a soil surface as a result of rainfall. Specifically there is virtually no information about the pathway a particle takes, the speed at which it travels and when it is in motion. Here we present a novel technique that can give insight into the movement of individual soil particles. By combining novel fluorescent videography techniques with custom image processing and a fluorescent soil tracer we have been able to trace the motion of soil particles under simulated rainfall in a laboratory soil flume. The system is able track multiple sub-millimeter particles simultaneously, establishing their position 50 times a second with sub-millimeter precision. An analysis toolkit has been developed enabling graphical and numerical analysis of the data obtained. For example, we are able to visualise and quantify parameters such as distance and direction of travel. Based on our observations we have created a conceptual model (Stop, hop, roll) which attempts to present a unified model for the movement of soil particles across a soil surface. It is hoped that this technology will open up new opportunities to create, parameterise and evaluate soil models as the motion of individual soil particles can now be easily monitored.