Distribution and effects of microplastics as carriers of heavy metals in river surface sediments.

There are few studies on microplastics (MPs) in urban river sediments compared to oceans, soils, and even rivers. In this study, the seasonal abundance of MPs, as well as their influencing factors on heavy metal adsorption in river sediments of the Ancient Canal of Zhenjiang City, China, were investigated for the first time. Through on-site sampling, microscopic observation, Raman spectroscopy, scanning electron microscopy, and high-temperature digestion, the abundance, shape, color, particle size, type, and surface characteristics of MPs in Ancient Canal sediments in different seasons, as well as the influencing factors of MPs as heavy metal carriers in different seasons, were analyzed. The results showed that the average abundance of MPs is 2049.09 ± 883.78 and 2216.36 ± 826.21 items kg-1 dry sediments in summer and winter, respectively, and different sites change significantly. In addition, particle sizes, types, colors, and shapes of MPs exhibited seasonal variations. Four MPs shapes were mainly observed: fibers, fragments, particles, and films. Among them, MPs in summer sediments are mainly fiber, and MPs in winter sediments are mainly particles. In the sediment in summer and winter, transparent MPs and small-size (<0.5 mm) MPs are the main ones, where the abundance of MPs decreased with increasing MPs size. The main MPs species are polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene (PE), with PP being the predominant MPs in the sediments in different seasons. Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) revealed that the surfaces of the MPs were characterized by rough, porous, cracked, and torn, with the attachment of various heavy metal elements, and all of the heavy metal elements accumulated to different degrees on the MPs. There was a significant positive correlation (p < 0.05) between the Mn content in the MPs and the Mn content in the sediments in winter, suggesting that the Mn in the MPs in winter may be derived from the sediments. In addition, the type, shape, size, and color of MPs affect the adsorption capacity of heavy metals. Most of the adsorption of MPs on Pb showed a significant negative correlation, and the adsorption of MPs on Cr, Zn, Cu, Cd, and Mn showed a significant positive correlation. MPs can be used as carriers of heavy metals, which will further enhance the hazards of living organisms and pose a potential threat to the safety of the urban river environment.

B, N Co-Doping Sequence: An Efficient Electronic Modulation of the Pd/MXene Interface with Enhanced Electrocatalytic Properties for Ethanol Electrooxidation.

Improving the electrocatalytic properties by regulating the surface electronic structure of supported metals has always been a hot issue in electrocatalysis. Herein, two novel catalysts Pd/B-N-Ti3C2 and Pd/N-B-Ti3C2 are used as the models to explore the effect of the B and N co-doping sequence on the surface electronic structure of metals, together with the electrocatalytic properties of ethanol oxidation reaction. The two catalysts exhibit obviously stratified morphology, and the Pd nanoparticles having the same amount are both uniformly distributed on the surface. However, the electron binding energy of Ti and Pd elements of Pd/B-N-Ti3C2 is smaller than that of Pd/N-B-Ti3C2. By exploring the electrocatalytic properties for EOR, it can be seen that all the electrochemical surface area, maximum peak current density, and antitoxicity of the Pd/B-N-Ti3C2 catalyst are much better than its counterpart. Such different properties of the catalysts can be attributed to the various doping species of B and N introduced by the doping sequence, which significantly affect the surface electronic structure and size distribution of supported metal Pd. Density functional theory calculations demonstrate that different B-doped species can offer sites for the H atom from CH3CH2OH of dehydrogenation in Pd/B-N-Ti3C2, thereby facilitating the progress of the EOR to a favorable pathway. This work provides a new insight into synthesizing the high-performance anode materials for ethanol fuel cells by regulating the supported metal catalyst with multielement doping.

[Distribution Characteristics and Pollution Evaluation of Nitrogen and Organic Matter in Overlying Water and Sediment of Guyun River and Jinshan Lake in Zhenjiang City].

Zhenjiang City is located in the intersection of the Yangtze River and the Beijing-Hangzhou Grand Canal, which is the most important water transportation hub in China, with abundant water resources and a dense river network. In recent years, the water quality in this region has declined with the rapid development of the economy and enhanced anthropogenic activity. Therefore, it is crucial to understand the state of water and sediment pollution in rivers and lakes of Zhenjiang City, which can provide important basic data for improving the water environment quality for this region. In total, 21 sampling sites (including 10 sites from Jinshan Lake and 11 sites from the ancient canal) in Zhenjiang City were selected, and overlying water and sediment samples were sampled in winter and summer, respectively. In addition, the physical and chemical parameters of overlying water and sediment samples were determined, respectively, and the organic index as well as organic nitrogen index were analyzed in order to evaluate the degree of sediment contamination in this region. Results showed that ① The TN concentration of overlying water changed from 1.95 mg·L-1 to 15.71 mg·L-1 in the winter and from 0.64 mg·L-1 to 12.09 mg·L-1 in the summer, with mean values of 4.01 mg·L-1 and 4.07 mg·L-1, respectively, which are higher than those of the surface water Ⅴ class standard. In addition, the ranked order of NH4+-N was as follows:winter < summer and river > lake; ② the TN content in the sediment samples ranged from 394.61 mg·kg-1 to 3288.09 mg·kg-1 and from 869.21 mg·kg-1 to 3598.04 mg·kg-1, respectively, with the mean values of 1928.58 mg·kg-1 and 2068.40 mg·kg-1. The ranked order of TN, NH4+-N, NO3--N, and Org-N was as follows:winter > summer for lake sediment samples. For river sediment samples, the ranked order of TN was winter < summer, whereas those of NH4+-N and NO3--N were winter > summer, indicating more complicated seasonal distribution for river sediment. In addition, the NO3--N content was higher in lake sediment than in river sediment, whereas that of NH4+-N was higher in river sediment than in lake sediment. The C/N ratio results indicated that the organic matter in sediments primarily resulted from endogenous pollution in this region; ③ Results of organic nitrogen index confirmed that 60% sediment samples from the lake in winter and the river in summer belong to the Ⅳ pollution level, indicating that organic nitrogen pollution existed in these samples. The results of organic index confirmed that 70% and 54.55% sediments samples belong to the Ⅱ pollution level, indicating that the sediments were not severely polluted in rivers and lakes of Zhenjiang City. The results demonstrate that sediments in rivers and lakes of Zhenjiang City are mainly polluted by nitrogen. Our findings provide important basic data for nitrogen control schemes in river water and sediment in Zhenjiang City.

Fe-doped H3PMo12O40 immobilized on covalent organic frameworks (Fe/PMA@COFs): a heterogeneous catalyst for the epoxidation of cyclooctene with H2O2.

Covalent organic frameworks (COFs) have arisen as one kind of devisable porous organic polymer that has attracted immense attention in catalytic applications. In this work, we prepared cost-effective imine-based COFs (COF-300, COF-LZU1 and CIN-1) via a reaction kettle operated in place of a traditional sealed Pyrex tube. Then, phosphomolybdic acid (PMA) and iron ions were immobilized on the COF supports by impregnation; the resulting frameworks were denoted as Fe/PMA@COFs (Fe/PMA@COF-LZU1, Fe/PMA@CIN-1 and Fe/PMA@COF-300). A series of characterization results demonstrated that the PMA and iron ions were uniformly dispersed on the surface/cavities of the COFs. The catalytic properties of the obtained Fe/PMA@COFs were investigated in the epoxidation of cyclooctene with H2O2 as the oxidant. The experimental results show that the Fe/PMA@CIN-1 composite can act as an efficient heterogeneous catalyst for the epoxidation of cyclooctene. The intramolecular charge transfer between the COFs and the dual sites (PMA and Fe ions), the spatial structure and the nitrogen content of the COFs played critical roles in dispersing and stabilizing the active species, which are closely connected with the activity and stability of the catalysts. A novel efficient heterogeneous catalyst for the epoxidation of olefins via a simple and cost-effective process is provided, and this experiment demonstrates the notable application prospects of the covalent organic skeleton as a catalyst support.