Micro- and nanoplastic-mediated phototransformation and bioaccessibility of fluorinated liquid crystal monomer in aquatic environments

Abstract

Micro- and nanoplastics are emerging pollutants that have attracted significant attention due to their potential to concentrate and transport coexisting organic pollutants in aquatic environments. Fluorinated liquid-crystal monomers (FLCMs) have also emerged as contaminants of concern, given their frequent occurrence, potential toxic effects, and propensity to co-occur with plastics in the environment. However, the influence of plastics on the environmental fate of FLCMs remains unclear yet. To address this knowledge gap, we investigated the accumulation of a key FLCM, 4-cyano-3-fluorophenyl 4-ethylbenzoate (CEB-F), on three common plastics, and examined the effects of nanoplastics on the phototransformation of CEB-F and its acute toxicity to Daphnia magna (D. magna). Our findings revealed that the adsorption capacity of CEB-F on different plastic materials followed the order: polystyrene (PS) < mixed cellulose ester (MCE) < polyamide (PA). The adsorption processes of CEB-F on the three plastics aligned more closely with the pseudo-first-order kinetic model and the Langmuir isotherm model, suggesting that the adsorption is primarily governed by physical diffusion. Theoretical calculations indicated that the adsorption of CEB-F on PS plastics is mainly driven by hydrophobic interactions. Additionally, PS nanoplastics (PSNPs) significantly enhanced the UV degradation of CEB-F, although the types of degradation intermediates did not change substantially, suggesting a limited impact on the degradation process and mechanism. Acute toxicity tests showed that PSNPs increased the toxicity of CEB-F to D. magna at lower concentrations, while the toxicity was reduced at higher concentrations. The obtained findings are of great significance to unraveling the plastic-mediated environmental fate and aquatic toxicity of FLCMs in natural waters.