A circumpolar study of surface zooplankton biodiversity of the Southern Ocean based on eDNA metabarcoding.

Under pressure from climate change and fishing, the Southern Ocean ecosystems have been changing. Zooplankton plays a vital role in the food web of the Southern Ocean and is crucial for maintaining ecosystem stability. Investigating the circumpolar-scale species composition and biodiversity of zooplankton is crucial for ensuring ecosystem-based conservation and management of the Southern Ocean in a changing climate. Here, we utilized eDNA metabarcoding to assess the biodiversity of zooplankton in the surface seawater surrounding the Antarctica based on samples collected during two expeditions spanning from 2021 to 2022. The main purpose of this paper is to provide more baseline information about circumpolar zooplankton biodiversity based on the emerging eDNA metabarcoding tool. This comprehensive approach led to the identification of over 300 distinct zooplankton species, forming a diverse community dominated by Jellyfish, Mollusca and Polychaete. Surprisingly, common dominant taxonomic groups such as krill and copepods in the Southern Ocean did not show high relative abundance (reads) in surface seawater. The results of redundancy analysis (RDA) and correlation analysis highlighted that water temperature and chlorophyll a had the most significant impact on the reads and diversity of zooplankton. Notably, the influence of water temperature on zooplankton seemed to be primarily indirect, potentially mediated by its effects on primary productivity. Increasing in primary production might lead to lower zooplankton biodiversity in the Southern Ocean in future. This research underscores the effectiveness of eDNA metabarcoding as a valuable tool for monitoring zooplankton diversity in open seas. Given the ongoing changes in temperature, sea ice extent and their impact on primary production, our findings lay a crucial foundation for using eDNA techniques to establish long-term biodiversity monitoring programs across extensive marine ecosystems in the future.

Constructing 2D/2D ultrathin Ti3C2/SnS2 Schottky heterojunctions toward efficient tetracycline degradation.

In this article, a novel 2D/2D ultrathin Ti3C2/SnS2 Schottky heterojunctions have been prepared via a facile hydrothermal process. The properties of the heterojunction were fully characterized. The photocatalytic degradation performance of composites was examined by photo-degradation of tetracycline hydrochloride (TC-HCL) under visible light irradiation. Compared with single SnS2, 3% Ti3C2/SnS2 displayed the better performance, the removal rate of TC-HCL reached 87.7% and the kinetic rate constant (k) of the optimal 3% Ti3C2/SnS2 composite was about 2.7 times of that of bare SnS2. The improved photocatalytic activity of Ti3C2/SnS2 is ascribed to the formation of 2D/2D Schottky heterojunction, which promotes the spatial charge separation and increases the surface reactive sites.

Preparation of Si-Mn/biochar composite and discussions about characterizations, advances in application and adsorption mechanisms.

A novel Si-Mn binary modified biochar composite material (SMBC) was prepared after being sintered 450 °C for 2 h. The crystal structure, surface functional groups, surface morphology and element composition, specific surface area and pore structure were characterized by XRD, FTIR, XPS, SEM + EDS and BET etc. The results showed that the surface of SMBC was rough and loose, and the specific surface area increased to 35.4284 m2/g. Si and Mn were uniformly attached to the surface of biochar in the form of SiO2, MnOx, MnSiO3. Batch adsorption experiments showed that SMBC had a higher removal efficiency (139.06 mg/g, above 98%) for Cu(II) when the dosage was 2 g/L and pH = 6. The cycle experiments showed that SMBC had good reusability, and its regeneration efficiency still reached 80.24%. The leaching amount of Mn (0.65 mg/L) was greatly reduced and avoid second-pollution resulted from ion exchange, which was attributed to the existence of Si-O-Mn bonds, and they could help Mn adhere to the surface of biochar more stable. The adsorption process was dominated by single-layer chemical adsorption and mainly occurred in the membrane diffusion stage. Cu(II) mainly formed -COOCu, -OCu, Cu(OH)2, Cu(OH)2CO3, Si-O-Cu, Mn-O-Cu by the mechanisms such as precipitation (4.74%), ion exchange (13.81%), complexation and physical adsorption (total 81.45% of the two mechanisms). Among them, complexation was dominant in the adsorption process.

Mixed biochar obtained by the co-pyrolysis of shrimp shell with corn straw: Co-pyrolysis characteristics and its adsorption capability.

The co-pyrolysis characteristics of shrimp shell (SS) with corn straw (CS) were investigated by comprehensive characterization to reveal the synergistic effects and further discuss the adsorption capability. TGA results showed that pyrolysis behavior and reactivity were improved with the increase of heating rate and doping ratio of CS. Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) indicated that co-pyrolysis can effectively reduce energy consumption and promote the decomposition of CaCO3. TG-FTIR and Py-GC/MS analysis indicated that the release of CH4, CO2, CO and NH3 at the doping ratio of 25% CS (75SS+25CS) was higher than that at other doping ratios, and the relative proportions of N-heterocyclics and oxygenates were lower, which was conducive to the development of pore structure for mixed biochar and effectively alleviated the pollution during co-pyrolysis process. The structure of mixed biochar was improved, confirmed by the characterizations of BET, SEM, FTIR and XRD. The mixed biochar prepared at 800 °C (75SS+25CS800) exhibited optimal porosity, aromatization and the most thorough CaCO3 decomposition. Batch adsorption experiment showed that the removal rate of 50 mg/L Cu(II) by 75SS+25CS800 was close to 100% under the dosage of 1 g/L and pH = 3-6. The adsorption process was well described by Langmuir, pseudo-second-order and Webber-Morris model, illustrating diffusion monolayer chemisorption was the main adsorption mechanism of Cu(II) on 75SS+25CS800. The maximum adsorption capacity of 75SS+25CS800 for Cu(II) was 79.77 mg/g at 35 °C. In short, this study provided a reference in optimizing the preparation process and improving the adsorption performance of mixed biochar.

Modification of biochar with silicon by one-step sintering and understanding of adsorption mechanism on copper ions.

Novel salt-based biochar was prepared by loading silicon (Si) on cornstalk biomass with "one-step sintering" technique. Manganese (Mn) was also used to modify biochar with the same method as a control. Surface morphology, elemental composition, crystal structure and surface area of "salt-based biochars" were analyzed by SEM + EDS, XRD, FTIR and BET, and the effects of the dosage of absorbent and pH of solution on the adsorption process were explored. Si and Mn could be successfully attached on the biochar surface as oxide forms. SiBC exhibited a dense and agglomerated surface, while MnBC was a kind of porous and rough materials. The optimal adsorption capability would realize when putting 2 g/L of biochar composites at pH = 5-6. Adsorption isotherms, adsorption kinetics, combine with FTIR and XPS were carried out to help to elaborate the adsorption mechanisms. The maximum adsorption capacity of Cu (II) was 152.61 mg/g on SiBC and it could reach at 97% of removal rate within 10 min when the concentration was 100 mg/L, while MnBC had to take 500 min to achieve the same adsorption effect, and reached 187.76 mg/g of maximum adsorption capacity. Langmuir model and pseudo-second-order model were more suitable for both SiBC and MnBC, which meant the monolayer and chemical adsorption were dominated. Surface complexation and precipitation was attributed to SiBC. Specialistic adsorption, ion exchange and intra-particle diffusion was put it down to MnBC.

AgCl/Ag/g-C3N4 Hybrid Composites: Preparation, Visible Light-Driven Photocatalytic Activity and Mechanism.

The ternary plasmonic AgCl/Ag/g-C3N4 photocatalysts were successfully fabricated by a modified deposition-precipitation method, through which Ag/AgCl nanoparticles (5-15 nm in size) were evenly dispersed on the surface of g-C3N4. The AgCl/Ag/g-C3N4 composites exhibited higher photocatalytic activity than Ag/AgCl and g-C3N4. The enhanced photocatalytic performance could be attributed to an efficient separation of electron-hole pairs through a Z-scheme mechanism, in which Ag nanoparticles acted as charge separation centers.