Impact of nanoplastic debris on the stability and transport of metal oxide nanoparticles: role of varying soil solution chemistry

The release of metal-based nanoparticles (MNPs) and nanoplastic debris (NPDs) has become ubiquitous in the natural ecosystem. Interaction between MNPs and NPDs may alter their fate and transport in the sub-surface environment and have not been addressed so far. Therefore, the present study has explored the role of NPDs on the stability and mobility of extensively used MNPs, i.e., CuO nanoparticles (NPs) under varying soil solutions (SS) chemistry. In the absence of NPDs, a very high aggregation of CuO NPs observed in SS extracted from black, lateritic, and red soils, which can be correlated with ionic strength (IS) and type of ionic species. The sedimentation rate (k(sed)(1/h)) for CuO NPs was > 0.5 h(-1) in the case of these SS. Interestingly, the stability and sedimentation behavior of CuO NPs varied significantly in the presence of NPDs. The k(sed) for CuO NPs decreased to half and found < 0.25 h(-1) in the presence of NPDs in all SS. C/C-0 values in breakthrough curves increased drastically (black < alluvial < laterite < red) in presence of NPDs. Results suggest that the release of NPDs in the terrestrial ecosystem is a potential threat leading to increased mobility of MNPs in the environment.