Transport of polyethylene and polypropylene microplastics under the action of agricultural chemicals: Role of pesticide adjuvants and neonicotinoid active ingredients

Understanding the impact of various agricultural chemical components on the fate and transport of microplastics (MPs) in the subsurface is essential. In this study, column experiments on saturated porous media were conducted to explore the influence of the coexistence environment of pesticide adjuvants (surfactants) and active ingredients (neonicotinoids) on the transport of polyethylene (PE) and polypropylene (PP) MPs. An anionic surfactant (sodium dodecyl sulfate (SDS)), a nonionic surfactant (nonylphenol ethoxylate (NP-40)), and three neonicotinoid insecticides (acetamiprid, dinotefuran, and nitenpyram) could independently increase MP migration by 8.90%-60.75% by improving the hydrophilicity. Acetamiprid or dinotefuran reduced the adhesion work of the binary system by competing with SDS for adsorption sites, thereby inhibiting PE mobility. However, nitenpyram in the mixture was not easily adsorbed on the surface of PE MPs together with SDS because of nitenpyram's high hydrophilicity. Neonicotinoid molecules could not reduce the hydrophilic modification of SDS on PP MPs by competing for adsorption sites. Owing to their weak charge and adhesion work of nonionic surfactants (-4.80 mV and 28.45 kT for PE and -8.21 mV and 17.64 kT for PP), neonicotinoids tended to occupy the adsorption sites originally belonging to NP-40. The long molecular chain of NP-40 made it difficult for high-concentration neonicotinoids to affect the adhesion on MPs. In addition, NP-40 was harder to peel off from the MP surface than SDS, leading to a larger MP transport ability in the sand column.

S. aureus and E. coli change the force and work of adhesion between P- and E-selectins of endothelial cells and ligands of neutrophil granulocytes

Thanks to the modification of the force spectroscopy method, when a neutrophil is fixed on the tip, and an endotheliocyte culture is grown on the substrate, the exact indicators of the adhesion force and adhesion work between cells have been investigated. The high variability of adhesion contacts in different donors associated with different expression profiles of neutrophils. It was found by flow cytometry that the EA.hy926 cell line actively expresses VCAM-1, as well as P- and E-selectin under the Staphylococcus aureus influence after 60 min of co-incubation. At the same time, the integral indicators of the adhesion force and adhesion work in the "neutrophil - endothelial cell" interaction were significantly inhibited by S. aureus in all studied donors. Since the VCAM-1 receptor is not involved in the adhesion bonds between neutrophils and endothelial cells, the suppression of the interaction is associated with the inhibition of P- and E-selectins, but direct receptors removal from the endothelial cells surface of the EA.hy926 cell line does not occur. Escherichia coli causes multidirectional effects in the system of interaction "neutrophil - endothelial cell", depending on the expression profile of the donor's neutrophils. However, the cumulative effect of interaction from all donors shows that in general, under the influence of E. coli, there is an increase in adhesion force and a suppression of adhesion work.

Thermodynamic method for establishment of relationship between icephobicity/superhydrophobicity and microstructure-Based on computing for adhesion work

Superhydrophobic surfaces (SHS) have potential in solving the icing of aircraft, high-voltage overhead transmission lines, and other power network devices exposed to the air. For this reason, we wish to establish the relationship between microstructure and the adhesion work by thermodynamic method, also for analysis of the relationship between the hydrophobicity and icephobicity (or anti-icing). Therefore, respectively considering Cassie-Baxter and Wenzel states, such relationship was theoretically established based on one/two-step surface model, enlightened by natural and artificial SHS. Among it, how to obtain the adhesion work of icing per unit ice-solid interface is the key to this study. Followed by it, hydrothermal experiment, chemical deposition, and etching methods were performed to verify our theoretical results.

•

How to model for the SHS based on the natural and artificial SHS;

•

Computation for adhesion work (w_aw) per unit area of a water droplet–SHS interface;

•

Computation for adhesion work (w_ai) per unit area of a frozen water droplet–SHS interface;

•

Computation for reduced adhesion work (w_a2) after icing;

•

Hydrothermal experiment, chemical deposition and etching methods were used for validation of modeling.