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Eukaryotic phytoplankton play a major role in the circulation of material and energy in a lake's ecosystem. The acquisition of information on the eukaryotic phytoplankton community is extremely significant for handling and regulating the ecosystems of lakes. In this study, samples were collected from the western half of Chaohu Lake in the summer and winter periods. Analyses revealed that the eukaryotic phytoplankton in this region comprised 70 genera, 34 orders, and 7 phyla. There were 61 genera, 29 orders, and 7 phyla in summer, and 25 genera, 14 orders, and 5 phyla in winter. The dominant genus was Chlamydomonas of Chlorophyta in summer. In contrast, the dominant genus was Mychonastes of Chlorophyta in winter. The diversity index analysis revealed that the eukaryotic phytoplankton community exhibited greater fluctuation in the summer than in the winter. Moreover, analysis of the physiochemical properties of the water samples showed considerable spatial and temporal differences in the water quality. This paper focusses primarily on analysing the influence of the physiochemical properties of water on the eukaryotic phytoplankton community. In particular, the effects of the major physicochemical properties of water on the community evolution of eukaryotic phytoplankton classes were evaluated using the redundancy analysis method. The findings demonstrated that total phosphorus (TP), PO4−-P, NH4+-N, and total nitrogen (TN) were the primary influencing factors in summer, whereas NO3−-N, DO, and water temperature (WT) were the major influencing factors in winter. Subsequently, the Mantel test revealed that the phylum level of the eukaryotic phytoplankton community was significantly correlated with WT, DO, NH4+-N, TN, TP, and Chlorophyll a. Variance partitioning analysis indicated that seasonal factors accounted for a large proportion of the variation in the eukaryotic phytoplankton community, reaching 48.4%. Subsequently, co-occurrence network analysis demonstrated that most families of eukaryotic phytoplankton were facilitated mutually, with the proportion of promotion being 94.1%. This study provides insight into the crucial factors that influence the phytoplankton communities and a reasonable control direction for the positive evolution of the eukaryotic phytoplankton community in the western half of Chaohu Lake. [ABSTRACT FROM AUTHOR]

Human activity factors have a significant impact on changes in ammonia nitrogen (NH3-N) content in rivers. Existing research mainly focuses on human activity factors as type factors, and lacks research on the key factors affecting river NH3-N among human activity factors. Therefore, this paper aims to study the key factors affecting human activities on NH3-N in the Huaihe River through various statistical analysis methods. The study found that changes in NH3-N content in the Huaihe River are mainly affected by land use patterns in the basin. There are two different ways in which land use affects NH3-N in rivers: direct effects and indirect effects. We also studied the main pathways through which changes in key factors in human activities affect NH3-N in the Huaihe River by constructing a structural equation model. The results showed that crop sowing area and afforestation area have a significant direct effect on NH3-N in the Huaihe River. In addition, crop sowing area and afforestation area can also affect river NH3-N by regulating the amount of nitrogen fertilizer and human excrement. This study is of great significance for understanding how human activities regulate NH3-N content in rivers. [ABSTRACT FROM AUTHOR]

As a crucial hydrolytic enzyme, urease plays a vital role in anaerobic biological treatment. It is well-known that manganese ions are abundant in landfill leachate, but their concentration fluctuates significantly. However, few studies have investigated the effect and mechanism of different concentrations of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate. This paper aimed to investigate the effects and mechanisms of different concentrations of Mn2+ on urease activity. The results showed that an appropriate amount of Mn2+ could significantly enhance urease activity, while a high concentration of Mn2+ could inhibit it. Insight into the mechanisms behind this phenomenon, various methods such as Zeta potential, particle size, ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and statistical analysis were employed in our study. Research suggested that, on one hand, Mn2+ may form hydrogen bonds with the side chain amino or carboxyl groups of urease amino acid residues, affecting the structure of urease through hydrogen bonding. Additionally, Mn2+ also binds to urease through hydrophobic interactions. On the other hand, the C–OH and C-N functional groups in urease have a strong affinity for Mn2+, and changes in these functional groups can greatly enhance the activity of urease. Furthermore, under the action of high concentrations of Mn2+, while the structure of urease becomes more stable, there is also a steric hindrance phenomenon that affects the substrate from entering the catalytic center. Therefore, studying the mechanism of Mn2+ affecting urease activity has significant biological significance and provides a new perspective for exploring the impact of metals on anaerobic bioprocessing of landfill leachate. [ABSTRACT FROM AUTHOR]

Considering the difficulty in recovering powder materials and the low photocatalytic efficiency, we have developed a series of Fe-MOFs (MIL-53(Fe), NH2-MIL-53(Fe), MIL-101(Fe), NH2-MIL-101(Fe) and MIL-100(Fe)) on pure iron mesh. In this study, the growth of Fe@MILs on the iron mesh was confirmed through SEM, XRD, and FT-IR characterizations. Among the photocatalytic experiments, Fe@NH2-MIL-53(Fe) and Fe@NH2-MIL-101(Fe), which are amine-functionalized, showed improved photocatalytic activity. This improvement is believed to be due to the combination of NH2 functionality and electron transfer to the Fe–O cluster centre, resulting in dual excitation pathways. Furthermore, Fe@MIL-100(Fe) showed the highest performance for the removal of Cr(VI), with over 92% of Cr(VI) being removed in the fifth photocatalytic cycle. The mechanism indicated the close connection between the compact structure of Fe-MOFs and effective electron migration. Additionally, sacrificial reagent experiments identified two important species for Cr(VI) reduction: electrons (e−) and superoxide radicals (˙O2−). The photocatalytic recovery tests showed a 97% recovery rate of Cr(VI). This work offers a novel solution for the treatment of water sources contaminated with Cr(VI). [ABSTRACT FROM AUTHOR]

Using Illumina high-throughput sequencing technology, the effects of heavy metal pollution on microbial community structure in the sediments of Hangbu River, Paihe River and Nanfei River intakes in the western half of Chaohu Lake Basin were analyzed. The results showed that Zn, Pb, Cr, Ni and Cd at the entrance of the Hangbu River were significantly higher than those at the entrance of the South Feihe River and the Paihe River (P<0.05), and Cd was moderately polluted at the entrance of the Hangbu River, posing a large ecological risk. The comprehensive potential pollution risk of heavy metals in the sediments of the three entrance lakes was low. In Chaohu Lake, Proteobacteria, Acidobacteriota, Bacteroidota and Chloroflexi are the main bacteria groups entering the three lake inlets. Proteobacteria, Acidobacteriota and Nitrospirota are high in the entrance of the lake from the Hangzhou River. The analysis of microbial-diversity showed that the diversity and richness of the entering estuary of Hangbu River was higher than that of Nanfei River and Paihe River. Redundancy analysis showed that the heavy metal content in the three lake intakes was strongly negatively correlated with most microorganisms, such as Bacteroidota and Chloroflexi, while positively correlated with some other bacteria, such as Myxococcota, Acidobacteriota and Nitrospirota. The sampling points and heavy metal redundancy analysis diagram show that heavy metals have a great influence on the sediment samples at the inlet of the lake. This study can provide a biological strategy for assessing the ecological stress of heavy metals and in situ bioremediation of heavy metal polluted sediments at different intakes of Chaohu Lake. [ABSTRACT FROM AUTHOR]