A framework to measure the availability of engineered nanoparticles in soils: Trends in soil tests and analytical tools

•Studies on role of ENPs in soils are much sparser than in aquatic systems.•Specific surface and size-related properties affect the behaviour of ENPs in soil.•Availability of ENPs in soil is not fully explained by soil–solution equilibrium.•Separation techniques for analysis of ENPs in soil need development and validation.