Search

Microplastics (MPs), an emerging pollutant, are of global concern due to their wide distribution and large quantities. In addition to MPs themselves, various additives within MPs (such as plasticizers, flame retardants, antioxidants and heavy metals) may also have harmful effects on the environment. Most of these additives are physically bound to plastics and can therefore be leached from the plastic and released into the environment. Aging of MPs in the actual environment can affect the migration and release of additives, further increasing the ecotoxicological risk of additives to organisms. This work reviews the functions of several commonly used additives in MPs, and summarizes the representative characterization methods. Furthermore, the migration and leaching of additives in the human environment and marine environment are outlined. As aging promotes the internal chain breaking of MPs and the increase of specific surface area, it in turn stimulates the release of additives. The hazards of additive exposure have been elucidated, and various studies from the laboratory have shown that more toxic additives such as phthalates and brominated flame retardants can disrupt a variety of biological processes in organisms, including metabolism, skeletal development and so on. Increase of MPs ecological risk caused by the leaching of toxic additives is discussed, especially under the effect of aging. This study presents a systematic summary of various functional and environmental behaviors of additives in plastics, using weathering forces as the main factor, which helps to better assess the environmental impact and potential risks of MPs.

Traditionally, toxicity of microplastics is ascribed to the chemicals adsorbed on them. However, microplastics can also interact with biomolecules, such as secretory proteins from aquatic organisms, and form protein-coated microplastics corona complex with unknown toxic effects. Here, we investigated the toxic effects of polystyrene microplastics (PS) and bovine serum albumin (BSA) coated PS corona complex (PS + BSA) on adult zebrafish (Danio rerio) intestines. The food intake ratio, accumulation and distribution of microplastics, histopathological changes, and molecular effects related to the antioxidant system in the intestine were studied. For the first time, we observed that PS + BSA aggregated on the inner surface of the zebrafish intestine, whereas PS dispersed. The aggregation of PS + BSA resulted in increased microplastics accumulation and longer residence time in the zebrafish intestine, which inhibited food intake and generated reactive oxygen species (ROS) in the intestine. Furthermore, the functions of the Keap1-Nrf2-ARE antioxidant signaling pathway and the activation of antioxidant enzymes were significantly affected by PS + BSA after a 21-day exposure. Ultimately, a higher accumulation of ROS and stronger inhibition of antioxidants led to more severe intestinal injury. These results suggest that the increased toxicity of protein-coated microplastics corona complex may be affected by oxidative damage and can result in the inhibition of digestion due to their aggregation and longer residence time in the intestine. Therefore, the ecological risk of microplastics may be underestimated owing to the interactive mechanisms of microplastics and protein coronas.

As an emerging pollutant, microplastics (MPs) may interact with dissolved organic matter (DOM) which is prevalent in the aqueous environment. Meanwhile, the aging of MPs in the actual environment increases the uncertainty of their environmental fate. Here, the interaction mechanisms between pristine and aged polypropylene microplastics (PP-MPs) and humic acid (HA) at pH 7.0 were explored. Microstructural changes of HA were examined by fluorescence and Fourier transformation infrared (FT-IR) spectroscopy. Atomic force microscopy coupled with infrared (AFM-IR) and micro-Raman techniques were used to characterize and analyze the interacted PP-MPs. The addition of HA increased the surface roughness of both pristine and aged PP-MPs. Results of AFM-IR and Raman spectra showed that the interaction of PP-MPs with HA accelerated their surface oxidation and enhanced the characteristic signals. XPS spectra showed that the oxygen content ratio of pristine and aged PP-MPs increased by 0.95% and 1.48% after the addition of HA, respectively. PP-MPs after aging interacted more strongly with HA and there was a higher affinity between them. Two-dimensional correlation spectroscopy (2D-COS) combined with FT-IR spectra further elucidated the interaction mechanism at the molecular level. This work will help to evaluate the environmental impact of MPs in ecosystems and understand their interactions with DOM.

Methylmercury (MeHg) is a neurotoxin that bioaccumulates in organisms and it forms strong complexes with reduced sulfur-containing ligands in dissolved organic matter (DOM). In the present study, the influences of solar radiation and sulfide addition reaction of humic acids (HA) on MeHg binding to HA were investigated using synchronous fluorescence and FT-IR two-dimensional correlation spectroscopic (2DCOS) analysis. Results showed that the complexation of fluorescent fractions of HA and sulfur-reacted HA (S-HA) with MeHg was not significantly affected by photoreaction treatments and the affinity of fluorescent fractions followed the order of protein-like fractionshumic-like fractionsfulvic-like fractions for both HA and S-HA. FT-IR 2DCOS analysis showed that the affinity of various binding sites in DOM for MeHg changed under different photoreaction treatments. Under dark treatment, small molecular compounds with low humification degree such as aromatic amino acids may be the site with the strongest binding ability to MeHg in HA, whereas aliphatic amino acids and sulfur-containing groups from sulfide addition reactions play a role in complexing of S-HA and MeHg. Under BS treatment (irradiation of DOM before MeHg binding), aliphatic compounds in HA preferentially bind to MeHg and aliphatic amino acids are the components with the strongest complexing ability; but for S-HA binding to MeHg, unsaturated functional groups and aromatic groups are more sensitive (alkenesalkanes, phenolsalcohols). Under AS treatment (irradiation of DOM after MeHg binding), unsaturated bonds and aromatic compounds in HA preferentially bind to MeHg and aromatic amino acids show the strongest complexing ability; but for S-HA binding to MeHg, aliphatic groups show the strongest complexing ability (alkanes, alkenesaromatics). These findings help us to better understand the complexation mechanisms between MeHg and DOM.

In order to study the influencing factors of cross-cultural communicative competence of English majors under mobile Internet, firstly, we made an empirical study on cross-cultural communication teaching for English majors. Then, we performed a comparative experiment between the mobile Internet-assisted high school English cross-cultural communication teaching model and the traditional teacher culture teaching-based teaching model. Finally, through questionnaires, informal interviews, and teachers’ observation of the teaching process, this paper aims to make an empirical study on the feasibility and effectiveness of mobile Internet assisted foreign language teachers in cultivating students’ awareness and ability of cross-cultural communication, so as to provide a basis for the follow-up research of cross-cultural communication teaching for English majors. The experimental results show that 93.4% of the students are satisfied with the mobile network-assisted English cross-cultural communication teaching model, and the integration of mobile network technology into English cross-cultural communication teaching has brought great changes to the teaching process. Compared with the traditional teaching mode of “chalk and blackboard,” multimedia organically integrates text, pictures, audio, video, and network, which greatly attracts the attention of teachers and students.

A highly ordered surface enhanced Raman spectroscopy substrate based on TiO2-Ag nanotubes was prepared using simple and rapid electrochemical method. Its enhancement factor was measured up to 1.5 × 109 using rhodamine 6G probe.

Microplastics (MPs, < 5 mm) in the environment have attracted worldwide attention due to their wide distribution and difficulty in handling. Aging processes such as UV irradiation, biodegradation, physical abrasion and chemical oxidation can affect the environmental behavior of MPs. This review article summarizes different aging processes of MPs and subsequent effects on the adsorption of pollutants, the leaching of additives, and the toxicity of MPs. In addition, the formation process of biofilm on the surface of MPs and the interactions between biofilm and aged MPs are revealed. MPs can accumulate different environmental pollutants (organic pollutants, heavy metals, microorganisms, etc.) through surface adsorption, pore filling and distribution. Moreover, the aging of MPs affects their adsorption performance toward these pollutants due to a series of changes in their specific surface area and oxygen-containing functional groups. The release of some toxic additives such as phthalates after aging can enhance the toxic effects of MPs. Aging also changes the shape and size of MPs, which can affect the eating habits of the organisms and further increase the potential toxicity of MPs. This article conducts a systematical analysis and summary of the environmental behavior and physicochemical properties of MPs as well as the changes due to MPs aging, which helps to better understand the impact of aging on MPs in the environment. Future research on MPs aging should reduce the knowledge gap between laboratory simulation and actual conditions and increase the environmental relevance.

The binding interactions between Hg and dissolved organic matter (DOM) affect the fate and transport of Hg in the aquatic environment. Here, we investigate the effects of photo-irradiation on the binding characteristics of dissolved organic matter with Hg(II) using FT-IR and synchronous fluorescence two-dimensional correlation spectroscopy (2D-COS). Results showed that the binding of Hg(II) onto humic acid (HA) followed the order of humic-like fraction > fulvic-like fraction > protein-like fraction and photo-irradiation did not affect this order. The binding affinity of each site within the fluorescent fraction was affected by the photoreaction patterns. Pre-irradiation of HA before Hg(II) binding changed its structures and binding ability. UV irradiation showed a more obvious effect on Hg(II)-HA complexes than solar irradiation, and UV irradiation enhanced the reactivity of aromatic groups of HA. The amine or amide N–H of HA played a leading role in binding with Hg(II) in the dark, whereas the aromatic amine C–N became dominant after UV irradiation. In fulvic acid (FA), the aromatic hydrogen C–H played a leading role in Hg(II) binding in the dark, but solar irradiation promoted the binding ability of polysaccharide C–O and the carboxyl C O became dominant after UV irradiation. The response sensitivity of the fulvic-like fraction to Hg(II) was higher than that of the protein-like fraction in FA. Multiple types of sites binding to Hg(II) were verified in the fulvic-like fraction and protein-like fraction of FA. These findings provide new insight into photo-induced structural changes of DOM upon Hg binding.

In order to study the temperature distribution and thermal stress of femtosecond pulsed laser interacting with energetic materials, in this paper, a femtosecond pulse laser loading system combined with an infrared thermal imager was used to experimentally study the temperature of the material when the femtosecond pulse laser irradiated Al/PTFE reactive material. Scanning electron microscope (SEM) was used to analyze the ablation morphology of laser ablated Al/PTFE. The theoretical model of the interaction between laser and Al/PTFE reactive material was established and the numerical calculation was carried out. The thermal stress was calculated and analyzed by using the material temperature measured by the experiment according to the thermoelastic theory. The following conclusions are obtained. The material is melted and vaporized under laser irradiation and ablation marks appear. The material temperature and ablation depth in the experiment and numerical simulation have a certain consistency. The heat released by the exothermic reaction in the laser irradiation area of the material has little effect on the surrounding materials. The radial thermal stress generated during laser irradiation is compressive stress, and the circular stress along the radius of the light spot changes from compressive stress to tensile stress. The greater the laser repetition frequency and the longer the laser action time are, the greater the thermal stress is. The maximum radial compression stresses are 2.54 MPa and 4.52 MPa when the laser repetition frequencies are 500 Hz and 1000 Hz, respectively.

Iron oxychloride (FeOCl) is a known effective iron-based catalyst and has been used in advanced oxidation processes (AOPs). This study intends to achieve more facile free radicals generation from peroxymonosulfate (PMS) activation by exploring the Fe(III)/Fe(II) cycle of FeOCl in the presence of hydroxylamine (HA). With 0.2 g/L FeOCl, 1.5 mM PMS, and 1 mM HA, the PMS/FeOCl/HA system could effectively achieve 98.88% of the oxidative degradation of 5 mg/L ciprofloxacin (CIP) in 15 min and quickly inactivate 99.99% of E. coli (108 CFU/mL) in 5 min at near-neutral pH. HA played an important role in promoting the Fe(III)/Fe(II) cycle, thereby greatly improving the oxidation activity of the system. The reactive oxygen species (ROS) such as HO, SO4- and O2- were identified as the dominated free radicals produced in the system. The intermediate products of CIP detected by liquid chromatograph-mass spectrometer (LC-MS) and three possible degradation pathways of CIP were proposed. The presence of common anions in the PMS/FeOCl/HA system, including HCO3-, Cl-, SO42-, and NO3-, enhanced the degradation efficiency of CIP to varying degrees at the concentrations of 10 mM. Moreover, FeOCl maintained a high degradation capability for CIP after several recycles. This work offers a new promising means of catalyzing the PMS-based AOPs in the degradation of refractory organics.

The late Ordovician was an important transition interval between the mid-Ordovician biological radiation and end-Ordovician extinction. Marine red beds (MRB) of Late Ordovician are distributed worldwide, including in the Americas, South Africa, England, and China. Among them, the conditions that contributed to the widespread Katian MRB was a combination of terrigenous input, cool-water settings, sediment oxidation, volcanic material input, and seasonal aridity. In contrast, Hirnantian MRB have a more limited distribution, and their occurrence might be related to regional tectonic settings and icehouse conditions. Sandbian MRB are distributed worldwide, but are relatively poorly studied. Even though Sandbian MRB are very similar in some characteristics to the Katian MRB, we don't know which factors were important to their formation and how these were related to marine environmental change and tectonic evolution. The Dawangou section near Kalping in the Tarim Basin of northwest China is an important global reference section for the auxiliary GSSP of the Middle–Late Ordovician boundary and for Sandbian through early Katian biostratigraphy and chronostratigraphy. Diffuse reflection spectroscopy, major and trace element analysis, rare earth element analysis, and sedimentology were employed to study the interval of Sandbian MRB in the Kanling Formation (within the N. gracilis graptolite zone) relative to underlying and overlying deposits. The red-colored strata have elevated total Fe and hematite contents, whereas the grey and grey-green samples have much a lower total Fe and a significant lack of hematite and goethite. The total Fe content for strata within the Sandbian MRB varies with the clay content. The Al Fe correlation within the Sandbian MRB is 0.9, whereas it is 0.6 for the non-red sediments. The Th/U ratio is much higher in the red-colored beds (averaging 7.0) relative to the underlying and overlying sediments (averaging 4.4). However, a redox proxy of Ni/Co ratios does not exhibit a significant difference between the underlying and overlying sediments (averages of 2.6 and 2.8) and the reddish Sandbian MRB interval (average of 2.6). The results indicated that the Sandbian marine red beds of the Tarim were formed during conditions of marine oxygenation that helped form and preserve the iron oxide. However, the regional distribution and aspects of the sediment geochemistry imply that another essential process for the formation of these Sandbian MRB was the influx of terrestrial iron-rich sediments from the exposed uplifts into the mixed shelf regions; and that this influx was partly governed by the regional patterns of southward subduction of the South Tianshan ocean and of northward subduction of the Altyn to the margins of the Tarim block.