Aging and salinity jointly control the co-transport mechanisms of nanoplastics and 4-nonylphenol in estuarine soils: Multi-scale insights from molecular interaction to pore network evolution
Zhang, X.; Guo, W.; Du, L.; Huo, S.; Li, J.; Gao, Y. (2026). Aging and salinity jointly control the co-transport mechanisms of nanoplastics and 4-nonylphenol in estuarine soils: Multi-scale insights from molecular interaction to pore network evolution. Wat. Res. 300: 125961. https://dx.doi.org/10.1016/j.watres.2026.125961
In: Water Research. Elsevier: Oxford; New York. ISSN 0043-1354; e-ISSN 1879-2448, meer
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| Author keywords |
Nanoplastics;4-nonylphenol;Co-transport;Micro-CT;Saltwater intrusion;polystyrene nanoplastics;salt intrusion;river estuary;aggregation;microplastics;transport;toxicity |
| Auteurs | | Top |
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- Huo, S.
- Li, J.
- Gao, Y., meer
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| Abstract |
Coastal estuaries are key hotspots for the accumulation of nanoplastics and hydrophobic organic pollutants, yet the co-transport of these contaminants under coupled salinity fluctuations and plastic aging remains poorly understood. This study integrated microcosm soil column experiments, micro-computed tomography (Micro-CT), and molecular dynamics (MD) simulations to elucidate the co-transport of pristine/aged polymethyl methacrylate nanoplastics (PMN) and 4-nonylphenol (4-NP) in saturated estuarine soils along salinity gradients. Pristine PMN inhibited 4-NP migration through co-deposition, whereas aged PMN acted as a source of dynamic release, facilitating its continuous breakthrough migration. Notably, 4-NP exerted a bidirectional feedback effect on PMN migration. Although it enhanced the migration efficiency of pristine PMN by 3.8-22.9% through electrostatic repulsion and site competition, it acted as a molecular bridge to trigger heterogeneous aggregation, thereby impeding the transport of aged PMN and reducing its recovery to as low as 10.3% at 5 PSU. Salinity further amplified these aging-related interactions, increasing aggregate size by 6.3-14.8% and enhancing attachment efficiency by a factor of 1.6-3.2 within the range of 0.5 to 5 PSU. MD simulations indicated that oxygen-containing functional groups on the surface of aged PMN provided high affinity binding sites for 4-NP by enhancing hydrogen bonding. Micro-CT visualisation and pore network modelling further confirmed that high salinity narrowed pore size distribution and reduced connectivity, increasing the fraction of low-connectivity pores from 4.3% to 6.2%, thereby forming hydrodynamic dead zones that enhanced the retention of enlarged PMN/4-NP hetero-aggregates within them. These findings provide multi-scale insights into the fate of composite pollutants and inform strategies for assessing pollution risks in salinized farmlands and coastal groundwater systems. |
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