Mechanisms of long-term nanoplastic release in soil and their interaction with soil colloids

Authors: LI, JINYU - Guangxi University; LIANG, YAN - Guangxi University; SHEN, CHONGYANG - China Agricultural University; LV, XIAOYAN - Guangxi University; Bradford, Scott

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2026
Publication Date: 6/18/2026
Citation: Li, J., Liang, Y., Shen, C., Lv, X., Bradford, S.A. 2026. Mechanisms of long-term nanoplastic release in soil and their interaction with soil colloids. Environmental Science and Technology. 60(25):18154-18166. https://doi.org/10.1021/acs.est.6c01978.
DOI: https://doi.org/10.1021/acs.est.6c01978

Interpretive Summary: Degradation of plastic waste create small particles that poses a potential risk to plant growth and microbial communities. Experiments were designed to better understand and quantify the long-term mobility and release of small plastic particles in soils under various environmental conditions. Results shows that the fate of plastic particles are sensitive to many factors including velocity, solution composition (e.g., ionic strength, cation type, pH, and plastic concentration), and interactions with soil colloids such as clays. Plastic particles were released in association with soil colloids with decreases in ionic strength, especially following cation exchange, but they were released without soil colloids under constant chemistry conditions and with increasing pH. This information will be of interest to scientists, health care professionals, and government regulators that are concerned about risks associated with plastic wastes.

Technical Abstract: The quantification of nanoplastic retention in soils and their release mechanisms with soil colloids remains challenging. This study used palladium-labeled nanoplastics (Pd-NPs) in column experiments to investigate their retention and potential long-term release, focusing on interactions with soil colloids. Pd-NPs were primarily immobilized through low energy barriers related to blocking, ripening, charge reversal, and cation bridging, particularly at sites with charge heterogeneity or nanoscale roughness. These interactions limited particle release under steady-state conditions or flow interruptions. However, transient changes in solution chemistry (e.g., increased pH and reduced ionic strength, IS) lowered energy barriers to detachment, facilitating remobilization of reversibly retained Pd-NPs. Cation exchange and IS reduction further promote particle release by decreasing charge heterogeneity and weakening cation bridging. Released Pd-NPs were mainly associated with soil colloids in the 0.1–2 µm range under reduced IS conditions via co-transport or hetero-aggregation. In contrast, release under increased pH occurred independently of soil colloid release. Long-term Pd-NP release was enhanced by soil colloid detachment. Additionally, Pd-NPs bound to stable solid surfaces in deep primary minima were irreversibly retained, preventing detachment. This study underscores the importance of understanding the interaction of Pd-NPs with soil colloids for accurate assessment of long-term environmental risks, particularly groundwater contamination.