Combined effects of photoaging and natural organic matter on the colloidal stability of nanoplastics in aquatic environments

Photo-oxidation of Micro- and Nanoplastics: Physical, Chemical, and Biological Effects in Environments

“…32,33,78 However, as opposed to HA, the inhibitory effect of bovine serum albumin (BSA) on the aggregation of PS NPs was strengthened after photo-oxidation due to stronger hydrogen bonding and electrostatic attraction between O-containing functional groups on aged NPs with amide groups of BSA. 33 Dissolved black carbon (DBC) was reported to enhance the aggregation of PS NPs in monovalent cationic solutions as the strong interaction between aromatic constituents of DBC and PS NPs partially screened negative charges of PS NPs; the photo-oxidation decreased the interaction between DBC and PS NPs, and decreased the promoting effect of DBC on the aggregation of PS NPs. 78 Photo-oxidation can also alter the interaction between natural minerals and NPs, affecting their aggregation and sedimentation in environments.…”

“…33 However, light irradiation induced the flocculation of BSA molecules that wrapped and integrated NPs, resulting in the formation of large aggregates. 33 Giri et al observed a significant increase in the hydrodynamic diameter when NPs were photo-oxidized (48 h) with microalgae extracellular polymeric substances (EPS), compared to the case that NPs were aged in the lake water medium alone (without EPS), which was explained by the formation of EPS layer on NPs during the photo-oxidation process. 95 Although the mechanism was not mentioned, the increased particle size might contribute to the heteroaggregation between NPs and photoflocculated EPS.…”

“…In addition to influencing the homoaggregation of individual NPs, photo-oxidation can also affect the interaction or heteroaggregation of NPs with other environmental colloids. Adsorption of environmental and biological macromolecules on NP surfaces is well-studied to enhance the stability of NPs in monovalent cationic solutions due to steric repulsion. , The photo-oxidation of NPs were reported to reduce their adsorption capacity toward organic molecules (e.g., HA, lysozyme, and alginate) and the thickness of adsorption layer, thereby decreasing the inhibitory effect of steric repulsion on subsequent aggregation of NPs. ,, However, as opposed to HA, the inhibitory effect of bovine serum albumin (BSA) on the aggregation of PS NPs was strengthened after photo-oxidation due to stronger hydrogen bonding and electrostatic attraction between O-containing functional groups on aged NPs with amide groups of BSA . Dissolved black carbon (DBC) was reported to enhance the aggregation of PS NPs in monovalent cationic solutions as the strong interaction between aromatic constituents of DBC and PS NPs partially screened negative charges of PS NPs; the photo-oxidation decreased the interaction between DBC and PS NPs, and decreased the promoting effect of DBC on the aggregation of PS NPs …”

“…95 Although the mechanism was not mentioned, the increased particle size might contribute to the heteroaggregation between NPs and photoflocculated EPS. 33,96 3.3. Transport Behavior in Porous Media.…”

“…These natural colloids may undergo phototransformation or affect the photooxidation of NPs, and subsequently affect the stability of NPs. For example, HA might compete with NPs for photons and undergo photodegradation, and the destruction of adsorbed HA increased (in NaCl) or decreased (in CaCl 2 ) the aggregation of NPs 33. However, light irradiation induced the flocculation of BSA molecules that wrapped and integrated NPs, resulting in the formation of large aggregates 33.…”