The influence of biofilms on the mobility of bare and capped zinc oxide nanoparticles in saturated sand and glass beads

Abstract

Biofilms are a common constituent of the subsurface and are known to influence contaminant transport; however only a few studies to date have addressed microbial controls on nanoparticle mobility in porous media. The impact of a 3-day Pantoea agglomerans biofilm on the mobility of zinc oxide (ZnO) nanoparticles was studied in column experiments containing sand and glass beads at near-neutral pH and constant ionic strength. Bare ZnO nanoparticles (bZnO-NPs) and ZnO nanoparticles capped with tri-aminopropyltriethoxysilane (cZnO-NPs) were used in the experiments. Breakthrough curves demonstrate that the biofilm particularly slowed nanoparticle migration of bZnO-NPs in glass bead columns and cZnO-NPs in sand columns. With the exception of bZnO-NPs in sand columns, biofilm-coated porous media retained more nanoparticles than those of controls without biofilm. The biofilm may bear an impact on the surface charge of the porous medium, nullifying porous medium-specific effects. Although viable cell counts (VCCs) decreased after the introduction of electrolyte and before nanoparticle transport experiments, SEM and CLSM imaging of porous medium samples taken from columns after nanoparticle transport experiments, as well as total organic carbon (TOC) measurements reveal that biofilm was present in the columns throughout the experiments. Hence, it can be concluded that even a thin amount of biofilm can hinder nanoparticle migration in small-scale porous medium experiments. Moreover, nanoparticle mobility is dependent on the binding capacity of biofilms, rather than the type of porous media.

<i>Pantoea agglomerans</i>: a mysterious bacterium of evil and good. Part IV. Beneficial effects

“…Besides significant chemical effects, Pantoea agglomerans may prevent penetration of harmful industrial contaminants into deeper parts of soil on a physicochemical basis. Kurlanda-Witek et al [166] have experimentally demonstrated that even a thin layer of a biofilm formed by P. agglomerans can hinder the migration of zinc oxide nanoparticles downwards porous media. The authors postulated that such biofilms could be used as a potential remediation strategy against the migration of nanoparticle contaminants in heterogeneous aquifers [166].…”

How Microbial Biofilms Control the Environmental Fate of Engineered Nanoparticles?

“…It was also observed in column transport experiments where retention of ENPs increases in presence of these microbial structures: latex NPs and CdSe/ZnS quantum dots (QDs) (Tripathi et al, 2012), zerovalent Fe-NPs (Lerner et al, 2012;Crampon et al, 2018), nano-ZnO (Jiang et al, 2013), biogenic nano-Se (Wang et al, 2019), nano-Ag (Xiao and Wiesner, 2013). This increased retention in column experiments is generally explained by changes in roughness, surface charge and hydrophobicity at the surface of aquifer grains (Donlan, 2002;Kurlanda-Witek et al, 2015) in addition to the intrinsic accumulation properties of these microbial structures.…”

Activities of Microplastics (MPs) in Agricultural Soil: A Review of MPs Pollution from the Perspective of Agricultural Ecosystems

“…60 Spherical and granular microplastics are more likely to migrate to deeper soils. 61 Leaching also has a significant positive effect on the vertical motion of microplastics. Soil organic carbon (SOC) and clay have important effects on the adsorption and migration of polystyrene microplastics.…”

“…O’Connor et al reported the mobility of five different MPs, which consisted of polyethylene (PE) and polypropylene (PP) particles of various sizes and densities, and observed that small-sized PE MPs (21 μm) had the greatest movement potential . Spherical and granular microplastics are more likely to migrate to deeper soils . Leaching also has a significant positive effect on the vertical motion of microplastics.…”