Chao Chai

During the COVID-19 pandemic, a substantial quantity of disposable face masks was discarded, consisting of three layers of nonwoven fabric. However, their improper disposal led to the release of microplastics (MPs) and nanoplastics (NPs) when they ended up in aquatic environments. To analyze the release kinetics and size characteristics of these masks, release experiments were performed on commercially available disposable masks over a period of 7 days and micro- and nanoplastic releases were detected using fiber counting and nanoparticle tracking analysis. The study’s findings revealed that there was no significant difference (p > 0.05) in the quantity of MPs released among the layers of the masks. However, the quantity of NPs released from the middle layer of the mask was 25.9 ± 1.3 × 10⁸ to 81.3 ± 5.3 × 10⁸ particles/piece, significantly higher than the inner and outer layers (p < 0.05). The release process of micro/nanoplastics (M/NPs) from each layer of the mask followed the Elovich equation and the power function equation, indicating that the release was divided into two stages. MPs in the range of 1–500 µm and NPs in the range of 100–300 nm dominated the release from each layer of the mask, accounting for an average of 93.81% and 67.52%, respectively. Based on these findings, recommendations are proposed to reduce the release of M/NPs from masks during subsequent use.

This study investigated the photodegradation of microplastics (MPs) by α-Fe₂O₃/g-C₃N₄. The effects of α-Fe₂O₃/g-C₃N₄ on MPs' surface were investigated through various techniques. With the addition of α-Fe₂O₃/g-C₃N₄ and under visible light irradiation, cracks and folds were observed on the MP films and particles. Compared to the treatment without photocatalyst addition, the mass loss of MPs increased with irradiation time when α-Fe₂O₃/g-C₃N₄ was added. Specifically, polystyrene films and particles in water showed 9.94% and 7.81% increased mass loss, respectively. The degradation of MPs using α-Fe₂O₃/g-C₃N₄ demonstrated the behavior consistent with the pseudo-first-order kinetic model. The presence of α-Fe₂O₃/g-C₃N₄ led to an increase in surface oxygen-containing functional groups and crystallinity while decreasing the average molecular weight of MPs. After 30 days of irradiation, the characteristic tensile bands of MPs with α-Fe₂O₃/g-C₃N₄ significantly increased, and the detection of carboxyl bands indicated the formation of carboxylic acid, ketones, and lactones as degradation products.

The combined effects of degrading bacteria (Paracoccus sp. LXC), humic acid (HA), and soil amendments, including chicken manure, biochar, and wormcast, were investigated through 84 d of incubation in order to improve the remediation of polycyclic aromatic hydrocarbon (PAH) in aged contaminated agricultural soil. PAH concentrations and dissipation kinetics were analyzed, and the biomass and communities of microorganisms and soil enzyme activities were examined to clarify the possible mechanism. The highest removal efficiency of PAHs was 42.1% when treated with Paracoccus sp. LXC combined with biochar and HA. PAH dissipation was consistent with the first-order kinetics model and the half-life of PAHs decreased from 2323.3 d in the natural attenuation to 103–277 d in the amended microcosms. Soil amendments and HA promoted the development of PAH-degrading bacteria and diversity of bacterial communities in soil but not that of fungi. The removal efficiency of PAHs was positively correlated with the density of PAH-degrading bacteria and soil urease (Ure), dehydrogenase (Deh), and manganese-dependent peroxidase (Mnp) activities (r = 0.824–0.941, p < .01). The Paracoccus sp. LXC apparently removed 2–4-ring PAHs, and biochar and wormcast were effective in removing 2–4-ring and 5–6-ring PAHs, respectively. The combined bioremediation strategy using degrading bacteria with soil amendments and HA has high potential for PAH removal in aged contaminated agricultural soil and the possible mechanism was the combination of bioaugmentation with Paracoccus sp. LXC and biostimulation with HA and soil amendments.