Evidence on enhanced transport and release of silver nanoparticles by colloids in soil due to modification of grain surface morphology and co-transport. (1st May 2021)

• Record Type: Journal Article
• Authors: Liang, Yan; Luo, Yonglu; Lu, Zhiwei; Klumpp, Erwin; Shen, Chongyang; Bradford, Scott A.
• Is Part Of: Environmental pollution. Volume 276(2021)
• Publication Date: 2021-05-01
• Subjects: Soil colloids -- Surface morphology -- AgNPs -- Retention -- Release; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2021.116661
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Natural soils have frequently been considered to decrease the mobility of engineered nanoparticles (NPs) in comparison to quartz sand due to the presence of colloids that provide additional retention sites. In contrast, this study demonstrates that the transport and release of silver nanoparticles (AgNPs) in sandy clay loam and loamy sand soils were enhanced in the presence of soil colloids that altered soil grain surface roughness. In particular, we found that the retention of AgNPs in purified soils (colloid-free and acid-treated) was more pronounced than in raw (untreated) soils or soils treated to remove organic matter (H2 O2 or 600 °C treated). Chemical analysis and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy demonstrated that the grain surfaces of raw and organic matter-removed soils were abundant with metal oxides and colloids compared to purified soil. Column transport and release experimental results, SEM images, and interaction energy calculations revealed that a significant amount of concave locations on purified soils hindered AgNP release by diffusion or ionic strength (IS) reduction due to deep primary energy minima. Conversely, AgNPs that were retained in soils in the presence of soil colloids were more susceptible to release under IS reduction because the primary minimum was shallow on the tops of convex locations created by attached soil colloids. Additionally, a considerable fraction of retained AgNPs in raw soil was released after cation exchange followed by IS reduction, while no release occurred for purified soil under the same conditions. The AgNP release was highly associated with soil colloids and co-transport of AgNPs and soil colloids was observed. Our work is the first to show that the presence of soil colloids can inhibit deposition and facilitate the release and co-transport of NPs in soil by alteration of the soil grain surface morphology and shallow primary minimum interactions. Graphical abstract: Image 1 Highlights: Soil colloids enhance NP transport/release by altering grain surface morphology. Surface roughness dominates over chemical heterogeneity for NP transport/release. Soil colloids promote NP release by grain surface modification and co-transport. NPs release from shallow primary minimum when soil colloids create protrusions. NP retention at valleys on grain is irreversible due to deep primary minimum. Abstract : Transport and release of nanoparticles can be enhanced by soil colloids via modification of grain surface morphology that alters the interaction energy and co-transport.