Nanoplastics (NPs), small plastic particles less than 100 nanometers in size, have raised growing environmental concerns due to their persistence and potential toxicity. Natural organic matter (NOM), a diverse mixture of organic compounds, is vital to the functioning of aquatic ecosystems, influencing microbial activity, contaminant retention, and carbon cycling. The interactions between NPs and NOMs are key to understanding how these substances behave in the environment, yet the structural complexity of NOMs and the surface properties of aged NPs have made it challenging to pinpoint their binding and aggregation mechanisms. This research responds to that challenge, offering critical insights into their molecular-level interactions.
Published (DOI: 10.1016/j.eehl.2024.08.004) in Eco-Environment & Health on September 11, 2024, the study was conducted by researchers from Northwest A&F University and South China Agricultural University, who employed molecular dynamics (MD) simulations and density functional theory (DFT) calculations to explore the interaction mechanisms between NPs (polyethylene, polyvinyl chloride, and polystyrene) and NOM. Their findings reveal how these materials form supramolecular assemblies through a combination of intermolecular forces such as hydrophobic interactions, hydrogen bonding, and cation bridging.
The research team simulated both pristine and aged NPs interacting with NOM, revealing key differences in aggregation behavior. Pristine NPs were found to aggregate primarily through hydrophobic forces, while aged NPs, with enhanced polarity, formed aggregates through a mix of hydrogen bonding and cation bridging. The team also visualized the electrostatic and van der Waals potentials of NP monomers, showing that aged NPs exhibit greater polarity, strengthening their interactions with NOMs. A notable discovery was the role of calcium ions (Ca²⁺) in bridging the negatively charged carboxyl groups of NOMs and aged NPs, leading to the formation of stable aggregates. Additionally, π-π stacking interactions were found to be pivotal in the binding of polystyrene NPs to NOMs, providing a comprehensive picture of these molecular interactions.
“This study represents a significant leap forward in understanding the molecular interactions between NPs and NOM,” said Dr. Hanzhong Jia, one of the study’s lead authors. “By combining MD simulations and DFT, we have uncovered the detailed mechanisms behind these interactions, which are crucial for assessing the environmental impact of NPs.”
The study’s findings have profound implications for environmental science and pollution control. A deeper understanding of how NPs and NOM aggregate can help predict their behavior in aquatic ecosystems, informing strategies to mitigate their impact on the environment. Furthermore, these insights could pave the way for the development of new materials or technologies aimed at capturing or degrading NPs in water systems. The research also highlights the importance of considering the aging process of plastics, as aged NPs interact with NOMs in ways that differ significantly from their pristine counterparts. Ultimately, this work contributes to a broader understanding of the global carbon cycle and the ecological risks posed by NPs.
###
References
DOI
10.1016/j.eehl.2024.08.004
Original Source URL
https://doi.org/10.1016/j.eehl.2024.08.004
Funding information
This work was supported by the National Natural Science Foundation of China (Grants No. 42107263).
About Eco-Environment & Health (EEH)
Eco-Environment & Health (EEH) is an international and multidisciplinary peer-reviewed journal designed for publications on the frontiers of the ecology, environment and health as well as their related disciplines. EEH focuses on the concept of "One Health" to promote green and sustainable development, dealing with the interactions among ecology, environment and health, and the underlying mechanisms and interventions. Our mission is to be one of the most important flagship journals in the field of environmental health.