engleski

Adsorption of pesticides on UV-aged microplastics; Mechanism and toxicity evaluation

Microplastics (MPs) are defined as polymer particles smaller than 5 mm, and due to their potentially harmful effects on the environment and human health are included in the list of persistent organic pollutants. One of the negative aspects of MPs is adsorption/desorption capacity regarding different organic pollutants, such as pesticides. Weathering of plastic material is one of the main sources of microplastic in the environment, leading to changes in color, size, crystallinity, chain scissions [1]. The aim of this work was to establish the correlation between the properties of MPs and the adsorption capacity for the investigated pollutants as well as toxicity effects on tested organisms. For that matter, we investigated the interactions of pristine and UV-aged polypropylene (PP) MPs with pesticides atrazine (ATZ) and alachlor (ALC) in aquatic media, while the concentration of the pesticides was monitored by High Performance Liquid Chromatography coupled with Photodiode Array Detector. Morphological changes in aged-microplastic samples were investigated using Fourier Transformation Infrared Spectroscopy and Differential Scanning Calorimetry. The interaction energies were further studied by density functional theory (DFT) to clarify the nature of the adsorption and the bonding types. Aquatic toxicity was assessed by exposing the MPs samples to green microalgae Selenastrum capricornutum (Pseudokirchneriella subcapitata) according to the standard procedure ISO 8692:2012. The adsorption isotherms of ALC and ATZ on both pristine and aged PP showed the best fit for the Freundlich model which indicates that the sorption is monolayered. Aged MP showed higher adsorption capacity than pristine MPs. Also, toxicity effects are more enhanced in the case of UV-aged MPs, which is noticed as an increase in the dilution factor of such samples.

microplastics, pesticides, DFT, adsorption, toxicity

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