Manifactured TiO2 nanoparticles availability and behavior in soil

The increase in applications of nanostructured materials and consequently their industrial production lead to an uncontmlled release of nanaparticies into the environment. The knowledge of the impact of nanoparticles, their availability or how they may alter terrestrial or aquatic ecosystems is limited. Nanomaterials containaining (TiO2-NPs) are usefull for a wide range of applications and at the end of life-cycle they could become nano-wastes, thus the need of understanding their transport and diffusion in terrestrial ecosystems (Sigma-Aldrich, anatase 25 nm) suspended with three Italian soils. Aliquots of soil suspensions with and without TiO2-NPs were periodically collected, and monitored for aggregate size distribution (Mastersizer2000_Malvern) and Ti concentration (ICP-OES Varian). Soils analysis showed huge differences in particle size distribution and organic matter content, where the cationic exchange capacity was higher in soils richer in clay and in organic carbon, and the values of electrical conductivity suggests ionic strength higher in the sandy soils suspension and lower in in the clayey one. TiO2-NPs are particularly influenced by the dissolved organic matter as well as the ionic strength. From day 6 ail soils suspensions and their mixture with TiO2-NPs showed size distribution similar to that of TiO2-NPs alone however differences in Ti concentration were found. TiO2-NPs suspended in soil richer in organic carbon showed higher Ti concentrations indicating a stabilization of TiO2-NPs aggregates probably due to a sterically stabilized system formed by the dissolved organic matter. In sandy soil suspension. the lowest Ti concentration could be attributed to the higher ionic strength despite of the expected lower adsorption capacity of this soil.