Soils are being extensively exposed to nanoparticles (NPs) due to their increasing use in many commercial products. The transport mechanisms of NPs in soil and their adverse effect of NPs microorganisms have been reported in various eco-physico-chemical studies by using different experimental systems, such as columns, microcosms, mesocosms or field lysimeters. Despite the increasing environmental realism in the experimental design, the assessment of toxic effects of NPs in soil still suffers a lack of ecological relevance for soil exposure. It is mainly based on acute exposures although chronic exposures are more likely to occur. This study aims at i) characterizing the mechanisms of NPs transport in columns of 6 highly contrasted naturel soils, ii) assessing the influence of single and multiple applications on the transfer of TiO 2 -NPs through an original exposure approach using soil columns and iii) comparing the effect of single and repeated exposures to TiO 2 -NPs in soil on the abundance and activity of soil nitrifying microbial community. The results permitted to evidence quite contrasted transport levels between the two types of NPs and also between soils. The NPs mobility and impact observed on soil microorganisms were shown to be controled by both the exposure route (concentration, dynamic injection, time between injections) and frequency of applications (single or repated injections). By simulating acute and chronic exposures of soil to NPs dynamically injected, we showed that successive applications of NPs are more damaging for the functionning soil microbiological than an acute exposure. This highlights the importance of considering both doses and exposure conditions for environmental risk assessment of manufactured NPs in soil.