Understanding colloid mobilization and transport in soils is a major concern for environmental protection and water resources management: They can act as vectors for sorbing pollutants, transporting them farther and faster through the vadose zone towards the water table than pollutants simply dissolved in water. Additionally, the existence of preferential flow paths in the soil such as cracks or invertebrate burrows is known to lead to an even faster breakthrough of the colloids. Some column or field scale undisturbed soil studies have identified the factors favouring/disfavouring particle mobilization, such as ionic strength, pH, initial soil moisture, trapping at air water interfaces or rainfall intensity. It appears however that one potentially important factor has been overlooked: the influence of the irrigation pattern undergone during the soil history. As a first step toward the study of this parameter, we carried out a series of infiltration-drainage experiments to investigate systematically the effects of periods without rain (pauses) on autochtonous particle mobilization in undisturbed soil columns. We showed that pause duration effect on mobilization is significant: the cumulative mass of particles eluted with the first 120ml of effluent is fifteen times higher when pause duration lasts 200 hours than when it lasts 1 hour. This variation occurs mainly during the transient stage of the flow (see figure). We found that this behavior is correlated with soil mean water content and proposed a mobilization mechanisms based on our observations. In a second experimental step we compare pause duration and ionic strength effects in term of mobilization efficiency. For this purpose we performed a new series of infiltration drainage-experiments keeping the pause duration constant, but changing the ionic strength of infiltration water from 10-5 to 10-1 M. We will discuss the outcome of this comparison, and highlight the practical impacts of our findings on an engineering and policy making point of view.