Retention of detonation nanodiamonds by soil: usage of tritium labeled nanoparticles and a key role for water-extractable Fe and Si

As the production of engineered nanomaterials (ENMs) expands, so might the potential for their release into the environment. Accurate risk assessment of ENMs in the environment is important for sustainable development and application of nanotechnologies. Nanodiamonds (NDs) occupy a special niche among ENMs and are ENMs at high risk of entering the environment. We evaluated interactions between NDs and a broad range of soils (retisols, phaeozems, chernozems, kastanozems, and solonetz) using tritium-labeled nanoparticles. The retention of NDs by the soils due to both binding to the solid phase of the soil and aggregation in the presence of soil solutes varied from 9.6 to 87.1 mg kg−1. Additionally, the effect of soil water-extractable components on NDs was studied in terms of alleviation of their size and ζ-potential. An increase in hydrodynamic diameter and a decrease in absolute value of the ζ-potential were observed in all cases except for solonetz where ζ-potential decreased from −22 to −34 mV. Data on deposition of NDs and their colloidal characteristics in the presence of soil solutes were statistically analyzed, which revealed leading factors governing retention of NDs by soil – ζ-potential of NDs in soil water-extracts and the presence of water-extractable Fe and Si. An abnormally low retention of NDs in solonetz was discovered and we hypothesize a key role of sodium as a peptizing agent.