Wastewater treatment plants (WWTPs) are considered as one of the important sources of microplastics (MPs) in the marine environment. In this paper, the characteristics of MPs in the effluent discharged from five WWTPs in Qingdao, China, in winter and summer were analyzed. The results showed that only fibers and fragments were observed, with fibers as a dominant part. Rayon was the most domain polymer type, followed by Polyethylene terephthalate (PET) and chlorinated polyethylene (CPE). The average sizes of fiber MPs were 1010 ± 924 µm and 610 ± 691 µm in winter and summer, respectively. The contents of rayon were higher in summer than in winter. More small and transparent MPs were observed in summer. Rayon abundances ranged from 4.1 to 19.9 items/L and 33.3 to 116.7 items/L, with 12.3 ± 5.6 items/L and 67.6 ± 30.6 items/L as the average value in winter and in summer, respectively. The abundances of other polymer type MPs were 7.23~19.65 items/L with average value of 12.7 ± 4.7 items/L in winter and 12.0~20.0 items/L with 16.8 ± 4.7 items/L in summer. The daily emissions were estimated as 8.38 × 10⁹~4.25 × 10¹⁰ items (9.2~27.8 kg) for rayon and 8.0 × 10⁹~1.2 × 10¹⁰ items (7.6~5.3 kg) discharged for the other polymer type MPs from the five WWTPs. The results indicated that the seasonal variation of characteristics and emission of MPs in the effluent from WWTPs was mainly caused by increasing discharge of rayon, which may relate to people’s living habits and tourism activities.

MoS₂ quantum dots (QDs) functionalized g-C₃N₄ nanosheets (MoS₂@CNNS) were prepared through a protonation-assisted ion exchange method, which were developed as a highly efficient biomimetic catalyst. Structural analysis revealed that uniformly-dispersed MoS₂ QDs with controllable size and different loading amount grew in-situ on the surface of CNNS, forming close-contact MoS₂@CNNS nanostructures and exhibiting distinct surface properties. Compared to MoS₂ QDs and CNNS, the MoS₂@CNNS nanocomposites exhibited a more than four times stronger peroxidase-like catalytic activity, which could catalyze the oxidation of 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H₂O₂ to generate a blue oxide. Among the MoS₂@CNNS nanocomposites, MoS₂@CNNS(30) was verified to present the best intrinsic peroxidase-like performance, which could be attributed to the more negative potential and larger specific surface area. A simple, rapid and ultrasensitive system for colorimetric detection of H₂O₂ was thus successfully established based on MoS₂@CNNS, displaying nice selectivity, reusability, and stability. The detection limit of H₂O₂ could reach as low as 0.02 μM. Furthermore, the kinetic and active species trapping experiments indicated the peroxidase-like catalytic mechanism of MoS₂@CNNS. This work develops a novel, rapid, and ultrasensitive approach for visual assay of H₂O₂, which has a potential application prospect on clinical diagnosis and biomedical analysis.

The global outbreak of Corona Virus Disease 2019 (COVID-19) has led to an extreme increase in the use of disposable masks. If the used disposable masks are not appropriately disposed of, they will enter the natural environment and lead to environmental pollution. In order to understand the impacts of disposable masks after being disposed of into the natural environment, aging experiments with simulated natural conditions were performed on the outer, inner, and middle layers of the masks to verify the aging characteristics of disposable masks. We analyzed the mechanical behavior, surface morphology, and Fourier Transform Infrared Spectroscopy (FT-IR) spectra of disposable masks treated with different levels of UV irradiation to understand the possible changes in the masks under UV. Results showed that the elongation at break, tensile strength, and maximum force of all three polypropylene (PP) mask layers decreased after UV irradiation, indicating chemical bond breakage. In the process of photoaging, each layer of the disposable masks showed a different degree of microscopic surface changes after UV irradiation, and these changes gradually intensified with the extension of UV exposure time. FT-IR results showed that functional groups, such as hydroxyl and carbonyl groups increased in each layer after UV irradiation. The results of this study support that, although the different layers of the disposable masks are all made of PP, they age differently in the environment. With the ever-increasing number of disposable masks in the environment, we need to further study the aging and degradation of disposable masks to better understand their potential impacts on the environment in the future.