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Microplastics (MPs) accumulation in sediments has posed a huge threat to freshwater ecosystems. However, it is still unclear the effect of MPs on riparian sediment structures and contaminant adsorption under different hydrological processes. In this study, three concentrations of polyamide (PA) MPs-treated sediments (0.1%, 1%, and 10%, w/w) were subjected to natural (NA) exposure, dry-wet (DW) cycles, and freeze-thaw (FT) cycles. The results indicated that PA MPs-added sediment increased the micro-aggregates by 10.1%−18.6% after FT cycles, leading to a decrease in aggregate stability. The pH, OM, and DOC of sediments were significantly increased in DW and FT treatments. In addition, the increasing concentration of PA MPs showed an obvious decrease in aromaticity, humification, and molecular weight of sediment DOM in FT treatments. Also, high level of MPs was more likely to inhibit the formation of humic-like substances and tryptophan-like proteins. For DW and FT cycles, 0.1% and 1% PA MPs-treated sediments slightly increased the adsorption capacity of Cd(II), which may be ascribed to the aging of MPs. Further correlation analysis found that DW and FT altered the link between DOM indicators, and aggregate stability was directly related to the changes in sediment organic carbon. Our findings revealed the ecological risk of MPs accumulating in riparian sediments under typical hydrological processes. [Display omitted] • Macro-aggregate and aggregate stability significantly reduced by combined FT cycles and MPs. • DW and FT cycles showed an obvious increase in sediment properties. • The aromaticity and humification degree of DOM were significantly decreased in 10% MPs-treated sediment. • DW and FT cycles slightly increased the Cd(II) adsorption onto 0.1% and 1% MPs-treated sediments. • There was a relationship between aggregate stability and sediment organic carbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Introduing N defects over g-C 3 N 4 significantly increased photocatalytic activity. • An IEF was built to further strengthened the transport of photoexcited carriers. • The excellent O 2 adsorption capacity promoted H 2 O 2 production via 2e− ORR. • A possible H 2 O 2 generation pathway formed via 1O 2 was proposed. The development of photocatalysts for the efficient generation of hydrogen peroxide (H 2 O 2) and degradation of antibiotic pollutants is a mutual-beneficial solution to the chemical resource demands and environmental remediation. Herein, efficient visible-light-driven H 2 O 2 production and antibiotic degradation are achieved by using nitrogen-deficient modified polymeric carbon nitride (g-C 3 N 4) to facilitate the reduction of dioxygen. The N defects modified g-C 3 N 4 reached an excellent H 2 O 2 generation rate of 623.5 μmol g−1h−1 without O 2 bubbling. The structural features and entire photocatalytic conversion process were systematically studied via experiments and theoretical calculations. It was found that the N defects in the framework constructed a giant internal electric field (IEF), which effectively inhibited carrier recombination. Revealed the neglected H 2 O 2 production via 1O 2 pathway, which effectively promoting the selective 2e− oxygen reduction reaction (ORR). More interestingly, the N defects structure greatly improved the O 2 adsorption ability and O 2 production ability of the material, while inhibiting the in situ generated H 2 O 2 from being decomposed and maintaining high efficiency of H 2 O 2 production under air conditions. This study thoroughly revealed the synergistic effects of the terminal cyano group and nitrogen vacancies over g-C 3 N 4 for efficient H 2 O 2 photogeneration photosynthesis. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota , Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments. [Display omitted] • The adsorption capacity of sediment for Pb(II) decreased with the content of MPs. • The changes in sediment enzyme activities and DOC structures varied with MPs concentration. • High doses of MPs increased the bioavailability of Pb in sediments. • MPs had a greater impact on bacterial community in Pb-contaminated sediments. [ABSTRACT FROM AUTHOR]

In this study, the adsorption behavior of Pb(II) on natural-aged and virgin microplastics in different electrolyte solutions was investigated. The results demonstrated that natural-aged microplastics exhibited higher adsorption capacity for Pb(II) compared to virgin ones, and the addition of CaCl 2 strongly inhibited the adsorption amount of Pb(II). The adsorption kinetics of Pb(II) adsorption were better fitted by the pseudo-second order model and Elovich equation, and were slowed down greatly at higher ionic strength. The rate-limiting steps of adsorption process were dominated by intra-particle diffusion. The adsorption isotherm of Pb(II) onto microplastics affected by salt ions can be well described by Freundlich model, the greater adsorption efficiency of natural-aged microplastics proved that adsorption process was multilayer and heterogeneous. In addition, pH significantly influenced the adsorption of Pb(II) due to the changes electrostatic interactions. The effect of fulvic acid in the electrolyte solutions was also revealed and attributed to the complexation with Na+ and Ca2+. Furthermore, the higher pH and ionic strength in different environmental water dramatically decreased adsorption capacity onto microplastics. Finally, it's confirmed that the adsorption mechanisms affected by salt ions mainly involve electrostatic interaction, surface complexation, and ionic exchange. These findings indicate that salt ions exert an important influence on the adsorption of heavy metals for MPs, which should be further concerned. [Display omitted] • The adsorption capacity of Pb(II) on natural-aged microplastics was higher than virgin ones. • Divalent Ca2+ markedly inhibited the sorption of Pb(II) compared to monovalent Na+. • The pH and fulvic acid affected the Pb(II) sorption in different electrolyte solutions. • Competition and complexation interactions played great roles in the adsorption process. [ABSTRACT FROM AUTHOR]

• Properties of biochars derived from common agriculture wastes were characterized. • Bamboo, coconut shell and sawdust-coal biochar have better performance. • Specific surface area of biochar played an important role on adsorption capacity. • Adsorption capacity increased with increasing in concentration and temperature. • The adsorption mechanism was discussed in detail. Biochar has acquired increasing attention in waste utilization and the treatment of environmental pollutants. In this study, the physicochemical properties of five types of biochars include straw biochar (SWB), coconut shell biochar (CSB), sawdust-coal biochar (SCB), bamboo biochar (BOB), rice husk biochar (RHB), and their adsorption of epoxiconazole (EPC) is discussed. The effects of initial concentration of EPC, solution temperature and pH level to these biochars were investigated. Besides, this work also analyzed the adsorption kinetics, adsorption isotherm, and thermodynamics of EPC removal in five biochar. Freundlich isotherm shows that the adsorption capacity decreased in the order SCB > BOB > CSB > SWB > RHB. The removal efficiency of EPC by SCB, BOB and CSB are much higher than SWB and RHB, and SCB has the best performance in EPC removal. The adsorption capacity of SCB is 19.0 g/kg, and its removal rate is nearly 97 %. The adsorption capacity of RHB is only 10.8 g/kg, with the removal rate of about 51 %. According to the characterization results of BET, SEM, XRD, and FT-IR, it is speculated that the adsorption capacity of five biochars to EPC is closely related to the total pore volume and specific surface area (SSA). [ABSTRACT FROM AUTHOR]