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Taking µ-HMX particles as the main research subject, a set of microdroplet sphericalization coating technology platforms was designed and constructed to realize the preparation of composite microspheres by sphericalization coating of µ-HMX. The suspension stability of µ-HMX particles and the mechanism of droplet formation were investigated, and the application effect of nanocarbon materials was also analyzed. The results showed that the prepared sample microspheres all showed a better spherical morphology, as well as good dispersibility; the samples with micron-sized particles for spherical coating had a lower thermal decomposition temperature, a higher energy release efficiency, lower mechanical sensibility, and better combustion performance; the incorporation of CNFs changed the combustion mode of the system, which resulted in the microsphere system of µ-HMX having a good safety performance. The stability and feasibility of uniform spheronization when the dispersed phase is a low-concentration particle suspension system in the spheronization encapsulation process by microdroplet technology were verified.

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Nanhu Lake is a red tourist attraction in Jiaxing city and the birthplace of the "Red Boat Spirit."To identify the influence of environmental factors on the distribution of plankton communities after ecological restoration in different regions, the environmental factors and plankton community in areas A, B, C, D, and S of Nanhu Lake were investigated in January 2021 after the completion of the ecological restoration projects. The concentrations of total nitrogen(TN), dissolved total nitrogen (DTN), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total phosphorus (TP), and dissolved total phosphorus (DTP) in the ecological restoration areas were significantly lower, and the content of dissolved oxygen (DO) was significantly higher (P<0.05) than those in the non-restoration area. The main phytoplankton species in the study area belonged to Cyanophyta and Bacillariophyta, and the main zooplankton species were protozoans and rotifers. The phytoplankton biomass in the restored area was lower than that in the unrestored area, and the number of phytoplankton and zooplankton species increased. Clustering and principal coordinate analysis results showed significant differences in plankton communities among the restoration areas (P<0.05), and plankton structures in regions A and B were similar. Redundancy analysis (RDA) showed that the main environmental factors affecting the distribution of phytoplankton communities were DO, NO3--N, pH, and water temperature (WT). The main driving factors of zooplankton community distribution were DO, NO3--N, NH4+-N, and TP. The results clarified the phytoplankton community characteristics and environmental correlation in different regions of Nanhu Lake, which can provide data support and reference for water ecological restoration of the lake.

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Making clear of the background values of different watersheds is an important mission for water resource management and assessment. The background values of the virgin forested watershed with less human activities sometimes have high COD values. In order to investigate this issue, this study take the Tangwang River watershed as a study case, analyzing the monitoring data of COD, BOD, and DO from the year of 2014 to 2018, and taking the water samples in the wet, normal, and dry season of 2019 to make clear the relationships between COD and DOM, the composition, and source of DOM. The non-degradation and terrigenous source DOM contributed to the most of COD values through the fitting analysis. The DOM in the Tangwang River mostly consisted of the humic-like acid and fulvic-like acid. Along with the river, the concentration of DOM had a little decrease, but the composition of DOM did not change obviously, so that the DOM coming from the virgin forest did not degrade in the river, and the river water only had the dilution effect with the tributaries fed in spatially. The organic matters in the virgin forest were easily washed away, so that the DOM concentration had an increase in the wet season temporally. The background COD values of the small virgin forested watershed were usually high as for the leaching effects of the organic matters from the forest, which was worthy noted when conducting the management project of this kind of watershed, in order to adjust measures to local conditions.

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Although the occurrence and distribution of antibiotic resistance genes (ARGs) in various aquatic ecosystems are well explored, understanding of the ecological processes and mechanisms governing the composition and dynamics of bacterial ARGs still remains limited across space and time. Here, we used high-throughput approaches to detect spatial patterns of bacterial ARGs and operational taxonomic units (OTUs) in an urbanizing subtropical watershed, Xiamen, southeast China over a five-year period. At watershed scale, the OTU profiles were undergoing a directional change, but the ARG profiles showed a high stability or stochastic change over time. Compared with the upstream and midstream, the richness, absolute abundance, normalized abundance and diversity of ARGs were significantly higher in the downstream waters. Our results revealed a clear rural-urban disparity in ARG and OTU profiles which were mainly governed by deterministic and stochastic assembly processes, respectively. With the increase of urban building area along the river, the ecological processes of ARG profiles shifted from stochastic to deterministic. In downstream waters, the bacterial ARG profiles were much more stable than bacterial OTUs. Further, our results indicated that both human-dominated environment (e.g., land use) and mobile genetic elements (MGEs) played an important role in shaping the ARG profiles and dynamics. Overall, this was a response to spatially extensive human-landscape interactions that included urban development in the river downstream region, which were common across subtropical coastal cities of China and can alter the ARG profile dynamics along rural-urban gradient. Therefore, watershed management actions aiming at reducing threats posed by ARGs in urbanizing watershed should first consider the surrounding urbanization level and the mode and intensity of human activity. Our findings also imply that due to the decoupling of bacterial function and taxonomy, both aspects should be studied separately.

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Bacterial antibiotic resistance genes (ARGs), a kind of emerging environmental pollutants, greatly threat human health through pathogenic bacteria. High-throughput quantitative PCR (HT-qPCR) and metagenomic approaches are two popular tools applied in aquatic environmental ARGs monitoring. However, current poor knowledge of different ARG profiling approaches' impacts on the understanding of the ARGs in aquatic environments greatly limit the further field application of these two approaches. For filling such knowledge gap, this study simultaneously employed these two approaches to examine and compare the ARGs in a freshwater reservoir across space and time. We found metagenomic approach detected more ARG subtypes and much higher bacitracin resistance genes' abundances than HT-qPCR. In general, HT-qPCR and metagenomics analyses both revealed similar ARG dynamic patterns and co-occurrence patterns between ARGs and bacterial taxa as well as the relationships between ARGs and environmental factors. Our results indicated the impacts of different ARG profiling approaches on the understanding of bacterial ARGs might be minor or negligible. HT-qPCR approach has the superiorities of time-saving, absolute quantification, low requirement for bioinformatics skills but also has some drawbacks including higher PCR amplification & primer bias, higher primer dependency and relative lower ARG subtype quantification capability compared to metagenomic approach. We suggest HT-qPCR approach can be employed for routine aquatic environmental monitoring, and metagenomic approach could be applied in comprehensive surveys for getting more ARG subtype information. Our data can be a useful reference for choosing right ARG profiling approaches for bacterial ARGs monitoring and risk assessment in aquatic environments.

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Although seasonality is a key driver of environmental fluctuation in aquatic ecosystems, there exists limited knowledge on the factors controlling the distribution of antibiotic resistance genes (ARGs) across seasons at a watershed scale. Here we used high-throughput quantitative PCR to quantify 285 ARGs conferring resistance to most major classes of antibiotics, reveal their spatial and seasonal distribution patterns, and depict the underlying mechanisms in a subtropical riverine ecosystem under low and high human pressures, in Xiamen city, southeast China. Our results showed that spatial differences in ARG richness and abundance overwhelmed their seasonal variations, with only ARGs that confer resistance to sulfonamide and vancomycin being significantly different across seasons. Only a few abundant ARGs (19 ARGs) could contribute to >70% of the total ARGs abundance and were found in all seasons. The significantly higher number of ARGs in the summer rainy period than other seasons coincided with high number of significant edges in ARG co-occurrence networks. Summer rainfall had strong dilution effect on ARGs in upstream waters and enrichment effect in downstream waters. The variance partitioning analysis indicated that the environment explained larger variance of ARG profiles than mobile genetic elements (MGEs), spatial predictors and the rainfall. Nevertheless, strong and significant correlations between transposase gene absolute abundance and aminoglycoside, chloramphenicol, MLS, multidrug and tetracycline classes of resistance genes inferred the role of MGEs on ARG distribution. Overall, our results imply that the modelling and management of ARGs in highly dynamic ecosystems could be better implemented by considering priority genes that dominate at spatial and seasonal gradients.

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Antibiotic resistance genes (ARGs) are widespread in aquatic environments, but we know little about their biogeographical distribution and occurrence at national scales. Here we analyzed the patterns of ARGs from 42 natural waterbodies (natural lakes and reservoirs) across China using high-throughput approaches. The major ARGs were multidrug genes and the main resistance mechanism was the efflux pump. Although the absolute abundance of ARGs (gene copies/L) in the south/central waterbodies was similar to the northern waterbodies, the normalized abundance of ARGs (ARGs/16S rRNA gene copy number) was higher in the south/central waterbodies than in the north (mainly because of the aminoglycoside and multidrug resistance genes). Human activities strongly correlated with the normalized abundance of ARGs. The composition of ARGs in the waterbodies of south/central China was different from that in the north, and ARGs showed a distance-decay relationship. Anthropogenic factors had the most significant effects on this spatial distribution of ARG composition, followed by the spatial, bacterial and physicochemical factors. These indicate that the ARGs exhibited biogeographical patterns and that multiple ecological mechanisms - such as environmental selection (human activities and local physicochemical parameters) and dispersal limitation - influence distribution of ARGs in these waters. In general, our results provide a valuable ecological insight to explain the large-scale dispersal patterns in ARGs, thereby having potential applications for both public health and environmental management.

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Microbial fuel cell (MFC) is regarded as a promising alternative for enhancing the removal of antibiotic pollutants. In this study, oxytetracycline served as an electron donor in the anode chamber of MFCs, and after continuous operation for 330 days, the efficiency of removal of 10 mg/L oxytetracycline in MFCs increased to 99.00% in 78 h, whereas removal efficiency of only 58.26% was achieved in microbial controls. Compared to microbial controls, higher ATP concentration and persistent electrical stimulation mainly contributed to bioelectrochemical reactions more rapidly to enhance oxytetracycline removal in MFCs. In addition, the analysis of bacterial communities revealed that Eubacterium spp.-as the main functional bacterial genus responsible for oxytetracycline biodegradation-flourished starting from merely 0.00%-91.69% ±â€¯0.27% (mean ±â€¯SD) in MFCs. High-throughput quantitative PCR showed that the normalized copy numbers of total antibiotic resistance genes (ARGs) and mobile genetic elements in MFCs were 1.7364 and 0.0065 copies/cell respectively, which were markedly lower than those in the microbial controls. Furthermore, there was no significant correlation between oxytetracycline concentration in the influent and abundance of ARGs in effluent from MFCs. Nevertheless, Tp614, a transposase gene, was found to be enriched in both MFCs and microbial reactors, suggesting that it may be a common challenge for different biological processes for wastewater treatment. This study therefore showed a lower probability of upregulation and transmission of ARGs in MFCs when compared to a traditional anaerobic microbial treatment.

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In freshwater systems, both antibiotic resistance genes (ARGs) and cyanobacterial blooms attract global public health concern. Cyanobacterial blooms can greatly impact bacterial taxonomic communities, but very little is known about the influence of the blooms on antibiotic resistance functional community. In this study, the ARGs in both free-living (FL) and particle-attached (PA) bacteria under bloom and non-bloom conditions were simultaneously investigated in a subtropical reservoir using high-throughput approaches. In total, 145 ARGs and 9 mobile genetic elements (MGEs) were detected. The most diverse and dominant of which (68.93%) were multidrug resistance genes and efflux pump mechanism. The richness of ARGs in both FL and PA bacteria was significantly lower during the bloom period compared with non-bloom period. The abundance of ARGs in FL bacteria was significantly lower under bloom condition than in the non-bloom period, but the abundance of ARGs in PA bacteria stayed constant. More importantly, the resistant functional community in PA bacteria was more strongly influenced by the cyanobacterial bloom than in the FL bacteria, although >96% ARGs were shared in both FL and PA bacteria or both bloom and non-bloom periods. We also compared the community compositions between taxonomy and function, and found antibiotic resistant communities were highly variable and exhibited lower similarity between bloom and non-bloom periods than seen in the taxonomic composition, with an exception of FL bacteria. Altogether, cyanobacterial blooms appear to have stronger inhibitory effect on ARG abundance in FL bacteria, and stronger influence on antibiotic resistant community composition in PA bacteria. Our results further suggested that both neutral and selective processes interactively affected the ARG composition dynamics of the FL and PA bacteria. However, the antibiotic resistant community of FL bacteria exhibited a higher level of temporal stochasticity following the bloom event than PA bacteria. Therefore, we emphasized the bacterial lifestyles as an important mechanism, giving rise to different responses of antibiotic resistant community to the cyanobacterial bloom.

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