Microplastics threat ecosystems health. Scientists have risen concerns on the implication of microplastics accumulation in soils. They have theorized that direct human activities rank first among the pathways microplastics traverse to enter soils. However, the lack of soil tests for microplastics detection and quantification hampers scientists attempts to validate their theories. The PhD thesis aims to contribute to the growing body of evidence that identifies and understands the sources and dynamics of microplastics in terrestrial ecosystems. It intends to shed light on the occurrence of microplastics across different land uses and to reveal major pollution sources. To embrace its endeavour, it proposes in the first chapters the development of novel soil tests to quantify and identify microplastics in soils. In the last two chapters, it deploys the methods to collect evidence on human influence on soil microplastic pollution at different temporal and spatial resolutions.