Revealing the distribution characteristics and key driving factors of dissolved organic matter in Baiyangdian Lake inflow rivers from different seasons and sources.

The river course is a transitional area connecting the source and receiving water bodies. The dissolved organic matter (DOM) in the river course is an important factor affecting the aquatic environment and ecological health. However, there are shortcomings in studying the differences and quantitative contributions of river DOM in different seasons and sources. In this study, ultraviolet-visible (UV-vis) and three-dimensional fluorescence spectra were used to characterize the optical properties, analyze the spatiotemporal changes, and establish the quantitative relationship between environmental factors and DOM in the inflow rivers of Baiyangdian Lake. The results showed that the relative DOM concentrations in summer and autumn were significantly higher than those in the other seasons (P < 0.001) and that the DOM source (SR < 1) was mainly exogenous. The fluorescence abundance of protein-like substances (C1 + C2 + C3) was the highest in spring, whereas that of humus C4 was the highest in autumn. Moreover, the inflow rivers exhibited strong autogenetic characteristics (BIX > 1) throughout the year. Self-organizing maps (SOM) indicated that the main driving factors of water quality were NO3--N in spring, autumn, and winter and DO, pH, and chemical oxygen demand (COD) in summer. Random forest analysis showed that the fluorescent components (C1-C4) were closely related to the migration and transformation of nitrogen, and pH and nitrogen were the main predictors of each component. The Mantel test and structural equation model (SEM) showed that temperature and NO3--N significantly influenced the DOM concentration, components, and molecular properties in different seasons. Moreover, the river source also affected the distribution mechanism of DOM in the water body. Our study comprehensively analyzed the response of DOM in inflow rivers in different seasons and water sources, providing a basis for further understanding the driving mechanisms of water quality.

[Dynamic Response of Aerobic Denitrification Bacteria to Water Quality in Baiyangdian Lake Under Different Hydrological Scenarios].

In order to explore the evolution law and driving mechanism of aerobic denitrification bacteria in Baiyangdian Lake under different hydrological scenarios, based on water quality survey and high-throughput sequencing technology, this study conducted a water quality factor analysis and aerobic denitrification bacteria α-diversity analysis, species composition, and network analysis. The results showed that the water body of Baiyangdian Lake was weakly alkaline, with the highest T and the lowest DO in the rainy season and the lowest T and the highest DO in the freezing season. There were significant differences between NH4+-N, NO2--N, NO3--N, TN, permanganate index, Fe, and Mn in Baiyangdian water under different hydrological scenarios (P < 0.01), and there was no significant difference in TP under different hydrological scenarios (P > 0.05). The largest category in water bodies under different hydrological scenarios was Proteobacteria, and the genera with a higher relative abundance were Magnetospirillum, Aeromonas, Pseudomonas, Azospirillum, and Bradyrhizobium. In addition, within the aerobic denitrifying bacteria community, there were significant differences in α-diversity (P < 0.001), with the highest abundance of microbial communities occurring during the freezing period, and the highest diversity and evenness of microbial communities during the dry and freezing periods. According to the RDA and Mantel analyses, the water quality driving factors of flora were different under different hydrological scenarios. The water quality driving factors of flora in the dry season were pH, NO3--N, NO2--N, and permanganate index; the driving factors of flora in the rainy season were pH, T, DO, NO2--N, and TP; the driving factors of flora in the normal season were NO2--N, Fe, and permanganate index; and the driving factors of flora in the freezing season were NO3--N and NONO2--N. Network analysis showed that there were temporal differences in species related to water quality driving factors. The genera related to water quality driving factors during the dry season were Magnetospirillum, Aeromonas, and Azoarcus, whereas the genera related to the rainy season were Magnetospirillum, Pseudomonas, and Aeromonas. The genera related to the normal season were Magnetospirillum, Pseudomonas, and Limnohabitans, and the genera related to the freezing period were Magnetospirillum, Azoarcus, and Pseudomonas. The relationship between key water quality factors (mainly T, DO, NO3--N, and permanganate index) and aerobic denitrification flora in different hydrological scenarios was gradually changing with time. In conclusion, the study on the evolution characteristics of aerobic denitrification bacteria in Baiyangdian Lake under different hydrological scenarios and the driving mechanism of environmental factors could provide a basis for understanding the evolution mechanism of aerobic denitrification bacteria in the natural environment.

[Spectral Characteristics and Sources of Dissolved Organic Matter in Inflow Rivers of Baiyangdian Lake Water in Summer Flood Season].

DOM is the largest reservoir of organic carbon in the world, and it plays a crucial role in the biogeochemical cycles of natural water bodies. A river is a transition area connecting source water and receiving water that controls the DOM exchange between them. Therefore, in this study, ultraviolet visible spectroscopy (UV-vis) and three-dimensional fluorescence spectroscopy (EEMs) combined with parallel factor analysis (PARAFAC) were used to analyze the spectral characteristics and sources of dissolved organic matter in the Fuhe River, Xiaobai River, Baigouyin River, and Puhe River of Baiyangdian. The results showed that a245 and a355 in the Fuhe River and Xiaobai River were significantly higher than those in the Baigouyin River and Puhe River. E2/E3 showed that the DOM relative molecular mass of the inflow river water body was Puhe River > Baigouyin River > Fuhe River > Xiaobai River. Three components, tyrosine-like (C1), terrigenous humus (C2), and tryptophan-like (C3), were determined using three-dimensional fluorescence through PARAFAC. There was no difference among the fluorescence components (P>0.05), but there were differences among the C2 and C3 components (P<0.05). The proportion of easily degradable protein-like components (C1+C3) was higher than that of humus-like components (C2). The autogeny index BIX was greater than 1, and the humification index HIX was less than 4, indicating that the autogeny characteristics of the river bodies were obvious, and the humification degree was weak. The FI index was the highest (1.96±0.25), and the HIX index was the lowest (0.46±0.08), and the self-generated source characteristics gradually strengthened along the direction of the river entering the lake, indicating that the water body of the Fuhe River showed higher endogenous and autogenic characteristics. Based on the correlation analysis of fluorescence components and characteristic parameters of DOM, the correlations between the Fuhe River and Xiaobaihe River and between the Baigouyin River and Puhe River bodies were similar. The correlation between fluorescence components of DOM and water quality parameters of each lake was significantly different, and it was strongly correlated with nitrogen and phosphorus in water. According to multiple linear regression analysis, there was no significant difference among C1 components, but there was a significant difference between C2 and C3 components. In summary, the carbon cycle process of Baiyangdian Lake was further understood through the study on the DOM spectral characteristics and sources of the inflow river waters in the summer flood season.

Characterizing the regional distribution, interaction with microorganisms, and sources of dissolved organic matter for summer rainfall: Insights from spectroscopy, community structure, and back-trajectory analyses.

Dissolved organic matter (DOM) in rainfall participates in many biogeochemical cycles in aquatic environments and affects biological activities in water bodies. Revealing the characteristics of rainfall DOM could broaden our understanding of the carbon cycle. Therefore, the distribution characteristics and response mechanisms of DOM to microorganisms were investigated in different regions of Hebei. The results indicated that the water quality of the northern region was worse than that of the middle and southern regions. The two protein like components (C1, C2) and one humic like component (C3) were obtained; at high molecular weight (MW), the fluorescence intensity is high in the northern region (0.03 ± 0.02 R.U.), while at low MW, the fluorescence intensity is highest in the southern region (0.50 ± 0.18 R.U.). Furthermore, C2 is significantly positively correlated with C1 (P < 0.01), while C2 is significantly negatively correlated with C3 (P < 0.05) was observed. The spectral index results indicated that rainfall DOM exhibited low humification and highly autochthonous characteristics. The southern region obtained higher richness and diversity of microbial species than northern region (P < 0.05). The community exhibits significant spatiotemporal differences, and the Acinetobacter, Enterobacter, and Massilia, were dominant genus. Redundancy and network analyses showed that the effects of C1, C2, and nitrate on microorganisms increased with decreasing MW, while low MW exhibited a more complex network between DOM and microorganisms than high MW. Meanwhile, C1, C2 had a large total effect on ß-diversity and function through structural equation modeling. The backward trajectory model indicates that the sources of air masses are from the northwest, local area, and sea in the northern, middle, and southern regions, respectively. This study broadened the understanding of the composition of summer rainfall DOM and its interactions with microorganisms during rainfall.

Enhanced nitrate removal efficiency and microbial response of immobilized mixed aerobic denitrifying bacteria through biochar coupled with inorganic electron donors in oligotrophic water.

The nitrogen removal characteristics and microbial response of biochar-immobilized mixed aerobic denitrifying bacteria (BIADB) were investigated at 25 °C and 10 °C. BIADB removed 53.51 ± 1.72 % (25 °C) and 39.90 ± 4.28 % (10 °C) nitrate in synthetic oligotrophic water. Even with practical oligotrophic water, BIADB still effectively removed 47.66-53.21 % (25 °C), and 39.26-45.63 % (10 °C) nitrate. The addition of inorganic electron donors increased nitrate removal by approximately 20 % for synthetic and practical water. Bacterial and functional communities exhibited significant temperature and stage differences (P < 0.05), with temperature and total dissolved nitrogen being the main environmental factors. The dominant genera and keystone taxa exhibited significant differences at the two temperatures. Structural equation model analysis showed that dissolved organic matter had the highest direct and indirect effects on diversity and function, respectively. This study provides an innovative pathway for utilizing biochar and inorganic electron donors for nitrate removal from oligotrophic waters.

Micro-pressure promotes endogenous phosphorus release in a deep reservoir by favouring microbial phosphate mineralisation and solubilisation coupled with sulphate reduction.

Deep reservoirs vary in their hydrostatic pressure owing to artificial water level control. The potential migration of phosphorus (P) in reservoir sediments raises the risk of harmful algal blooms. To ascertain the mechanisms of endogenous P release in reservoirs, we characterised aquatic microbial communities associated with coupled iron (Fe), P and sulphur (S) cycling at the sediment-water interface. The responses of microbial communities to hydrostatic pressures of 0.2-0.7 mega pascals (MPa; that is, micro-pressures) were investigated through a 30-day simulation experiment. Our findings unravelled a potential mechanism that micro-pressure enhanced the solubilisation of Fe/aluminium (Al)-bound P caused by microbially-driven sulphate reduction, leading to endogenous P release in the deep reservoir. Although the vertical distribution of labile Fe was not affected by pressure changes, we did observe Fe resupply at sediment depths of 2-5 cm. Metagenomic analysis revealed increased abundances of functional genes for P mineralisation (phoD, phoA), P solubilisation (pqqC, ppx-gppA) and sulphate reduction (cysD, cysC) in sediments subjected to micro-pressure, which contrasted with the pattern of S oxidation gene (soxB). There was a tight connection between P and S cycling-related microbial communities, based on significant positive correlations between labile element (P and S) concentrations and functional gene (phoD, cysD) abundances. This provided strong support that Fe-P-S coupling processes were governed by micro-pressure through modulation of P and S cycling-related microbial functions. Key taxa involved in P and S cycling (for example, Bradyrhizobium, Methyloceanibacter) positively responded to micro-pressure and as such, indirectly drove P release from sediments by facilitating P mineralisation and solubilisation coupled with sulphate reduction.

Identification and relative contributions of environmental driving factors for abundant and rare bacterial taxa to thermal stratification evolution.

The thermal stratification of reservoir affects water quality, and water quality evolution is largely driven by microorganisms. However, few studies have been conducted on the response of abundant taxa (AT) and rare taxa (RT) to thermal stratification evolution in reservoirs. Here, using high-throughput absolute quantitative techniques, we examined the classification, phylogenetic diversity patterns, and assembly mechanisms of different subcommunities during different periods and investigated the key environmental factors driving community construction and composition. The results showed that community and phylogenic distances of RT were higher than AT (P < 0.001), and community and phylogenic distances of the different subcommunities were significantly positively correlated with the dissimilarity of environmental factors (P < 0.001). Nitrate (NO3--N) was the main driving factor of AT and RT in the water stratification period, and Mn was the main driving factor in the water mixing period (MP) based on redundancy analysis (RDA) and random forest analysis (RF). The interpretation rate of key environmental factors based on the selected indicator species in RT by RF was higher than that of AT, and Xylophilus (10.5%) and Prosthecobacter (0.1%) had the highest average absolute abundance in AT and RT during the water stable stratification period (SSP), whereas Unassigned had the highest abundance during the MP and weak stratification period (WSP). The network of RT and environmental factors was more stable than that of AT, and stratification made the network more complex. NO3--N was the main node of the network during the SSP, and manganese (Mn) was the main node during the MP. Dispersal limitation dominated community aggregation, the proportion of AT was higher than that of RT. Structural Equation Model (SEM) showed that NO3--N and temperature (T) had the highest direct and total effects on ß-diversity of AT and RT for the SP and MP, respectively.

A Public Health Review into Two Decades of Domestic Trampoline Injuries in Children within Queensland, Australia.

Trampolining as an activity brings enjoyment and many health benefits, but at the same time it carries an injury risk. Most domestic trampoline users are children who are developing in skill, cognition, risk perception, physical strength and resilience to injury. Several common patterns of child trampoline injuries have been identified and countermeasures outlined in standards have been taken to reduce higher risk injury mechanisms, such as entrapment and falls from the trampoline through design, product and point of sale labelling. In Australia, the first national trampoline standard was published in 2003 which introduced improvements in trampoline design and requirements for labelling and padding. This work investigated the potential impact of these and subsequent changes based on almost two decades of emergency department trampoline injury data collected in Queensland, Australia. These data describe the changing representative proportion and pattern of trampoline injuries in Queensland over time by age, mechanism, gender, severity and nature of injury of injured persons up to the age of 14 years. The interrelationships between different injury characteristics were also analysed to propose the main factors influencing injury occurrence and severity. These findings seem to indicate that safety evolution in the form of enclosure nets, frame impact attenuation and entrapment protection have likely improved domestic trampoline safety. Other factors, such as adult supervision, minimum age and avoidance of multiple users, could further reduce injury but are harder to influence in the domestic setting.

Spatial and temporal dynamic response of abundant and rare aerobic denitrifying bacteria to dissolved organic matter in natural water: A case study of Lake Baiyangdian, China.

Revealing the responses of abundant and rare aerobic denitrifying bacteria to dissolved organic matter (DOM) composition is essential for understanding the aquatic N cycle ecosystems. In this study, fluorescence region integration and high-throughput sequencing techniques were used to investigate the spatiotemporal characteristics and dynamic response of DOM and aerobic denitrifying bacteria. The DOM compositions were significantly different among the four seasons (P < 0.001) without spatial differences. Tryptophan-like substances (P2, 27.89-42.67%) and microbial metabolites (P4, 14.62-42.03%) were the dominant components, and DOM exhibited strong autogenous characteristics. Abundant (AT), moderate (MT), and rare taxa (RT) of aerobic denitrifying bacteria showed significant and spatiotemporal differences (P < 0.05). The responses of α-diversity and niche breadth of AT and RT to DOM differed. The DOM explanation proportion for aerobic denitrifying bacteria exhibited spatiotemporal differences based on redundancy analysis. Foliate-like substances (P3) had the highest interpretation rate of AT in spring and summer, while humic-like substances (P5) had the highest interpretation rate of RT in spring and winter. Network analysis showed that RT networks were more complex than AT networks. Pseudomonas was the main genus associated with DOM in AT on a temporal scale, and was more strongly correlated with tyrosine-like substances (P1), P2, and P5. Aeromonas was the main genus associated with DOM in AT on a spatial scale and was more strongly correlated with P1 and P5. Magnetospirillum was the main genus associated with DOM in RT on a spatiotemporal scale, which was more sensitive to P3 and P4. Special operational taxonomic units were transformed between AT and RT with seasonal changes, but not between the two regions. To summarize, our results revealed that bacteria with different abundances utilized DOM components differently, and provides new insight on the spatiotemporal response of DOM and aerobic denitrifying bacteria in aquatic ecosystems of biogeochemical significance.

Response of dissolved organic matter to thermal stratification and environmental indication: The case of Gangnan Reservoir.

Dissolved Organic Matter (DOM), an important part of the carbon cycle in reservoir ecosystems, has a great impact on aquatic environment to recognize the conversion process of different media DOM. The distribution, spectral characteristics, and sources of DOM in Gangnan Reservoir during thermal stratification were analyzed using ultraviolet-visible absorption spectroscopy and excitation-emission matrix spectroscopy. Three humic-like components (C2, C3, and C4) and two protein-like components (C1 and C5) were identified. The proportions of the humic-like components increased with the progression of thermal stratification (C2 and C3 were dominant), whereas the protein-like components decreased in proportion, and the trend in the interstitial water was constant (C3 and C4 were dominant). The proportion of the humic-like components in the sediments was highest during the stationary period of thermal stratification (C2 and C3 were dominant). C2 and C3 were significantly correlated in the water body and interstitial water (P < 0.001), while C1 and C5 were correlated in the sediment (P < 0.05). In the water body, C2 and C3 were negatively correlated during the formative period of thermal stratification (slope = -1.85; R2 = 0.52), strongly positively correlated during the stationary period (slope = 0.76; R2 = 0.94), and positively correlated during the weakening period of thermal stratification (slope = 0.46; R2 = 0.30). With the progression of thermal stratification, the relative contribution of endogenous substances decreased gradually, whereas the humification degree increased in the water body and interstitial water. The protein-like components and key physicochemical factors (Fe, Mn, TN, TP, and CODMn) were significantly correlated during the formative period (P < 0.05), and humic-like components and key physicochemical factors (NO2--N and TN) were significantly correlated during the stationary and weakening periods (P < 0.05). C1, C4, and C5 indicated NO3--N during the formative period; C2 and C3 indicated NO3--N during the stationary period; and C2 and C4 indicated NO3--N during the weakening period in the water body. These findings enhance the understanding the mutual transformation processes of DOM in reservoir ecosystems and could guide water quality management.

Efficient nitrate removal of immobilized mixed aerobic denitrifying bacteria and community dynamics response to temperature and low carbon/nitrogen polluted water.

The denitrification performance of immobilized mixed aerobic denitrifying bacteria (IMADB) was investigated. IMADB displayed strong temperature adaptability under low Carbon/Nitrogen conditions. At 5, 15, and 25 °C, the nitrate removal efficiencies of volcanic rock and polyester fiber sponge immobilized system reached 83.95%-98.25% and 89.71%-98.14%, respectively. The nitrate content removed by the carrier accounted for 41.18%-82.47% of the nitrate content removed by the immobilized system at different temperature, and played a major role in nitrate removal. The lower the temperature, the greater the role of the carrier. At the same temperature, carrier had a relatively higher richness, diversity, and evenness. Network analysis revealed that carrier species, which were positively correlated with nitrate removal efficiency, had the largest OTUs and abundance. Meanwhile, carrier had the widest niche. The total nitrogen removal efficiency of IMADB reached 56.10%-62.31% in the natural water system, highlighting a promising application prospect.

Investigating the Knuckleball Effect in Soccer Using a Smart Ball and Training Machine.

The term knuckleball in sporting jargon is used to describe a ball that has been launched with minimal spin, resulting in a trajectory that is erratic and unpredictable. This phenomenon was first observed in baseball (where the term originated) and has since been observed in other sports. While knuckleball has long fascinated the scientific community, the bulk of research has primarily focused on knuckleball as it occurs in baseball. Following the changes in the design of the soccer ball after the 2006 World Cup, knuckleball and ball aerodynamics were exploited by soccer players. This research examined the properties of a knuckleball in the sport of soccer. We designed and evaluated a system that could reproduce the knuckleball effect on soccer balls based on previous theories and characteristics outlined in our literature review. Our system is comprised of the Adidas miCoach Smart Ball, a companion smart phone app for data collection, a ball-launching machine with programmable functions, and a video-based tracking system and Tracker motion analysis software. The results from the testing showed that our system was successfully able to produce knuckleball behaviour on the football in a highly consistent manner. This verified the dynamic models of knuckleball that we outline. While a small portion of the data showed some lateral deviations (zig-zag trajectory), this erratic and unpredictable trajectory was much smaller in magnitude when compared to examples seen in professional games. The sensor data from the miCoach app and trajectory data from the Tracker motion analysis software, showed that the knuckleballs were consistently reproduced in-line with theoretical dynamics.

Investigation into the Trampoline Dynamic Characteristics and Analysis of Double Bounce Vibrations.

Double bounce is an unusual and potentially very hazardous phenomenon that most trampoline users may have experienced, yet few would have really understood how and why it occurs. This paper provides an in-depth investigation into the double bounce. Firstly, the static and dynamic characteristics of a recreational trampoline are analysed theoretically and verified through experiments. Then, based on the developed trampoline dynamic model, double bounce simulation is conducted with two medicine balls released with different time delays. Through simulation, the process of double bounce is presented in detail, which comprehensively reveals how energy is transferred between users during double bounce. Furthermore, the effect of release time delay on double bounce is also presented. Finally, we conducted an experiment which produced similar results to the simulation and validated the reliability of the trampoline dynamic model and double bounce theoretical analysis.

Effectively compound the heterojunction formed by flower-like Bi2S3 and g-C3N4 to enhance photocatalytic activity.

In this study, the flower-shaped Bi2S3/g-C3N4-2.6 heterojunction obtained by solvothermal method and its photocatalytic degradation efficiency of rhodamine B (RhB) and tetracycline (TC) in aqueous solution within 40 min is as high as 98.8% and 94.6%. For RhB degradation, the photocatalytic reaction rate constant (k) of Bi2S3/g-C3N4-2.6 is approximately 1.8 and 45.5 times that of Bi2S3 and g-C3N4. For TC, k is 3.1 and 2.4 times that of Bi2S3 and g-C3N4, respectively. The key to determining the high catalytic activity of Bi2S3/g-C3N4 lies in the formation of a good heterojunction between Bi2S3 and g-C3N4, which accelerates the electron transfer rate between the heterojunction interface and effectively avoids electron-hole recombination. The effects of catalyst dosage, different pH values, inorganic anions, and capture agents on the photodegradation performance of RhB were investigated. The results show that the catalyst dosage is 1.33 g/L, and the solution pH is in the range of 5-9, which has the best removal effect on pollutants, and the isolation of holes (h+) with strong oxidizing ability promotes the collapse of pollutant molecules. Combined with electrochemical tests, a possible degradation mechanism was advised.

[Temporal and Spatial Distribution Characteristics and Driving Factors of Denitrification Bacterial Community Structure from Landscape Water in Hebei Province: Taking Shijiazhuang as Example].

Landscape water is an important part of urban water systems, and excessive nitrogen affects its ecological functions. This study aimed to investigate the temporal and spatial distribution characteristics and driving factors of the community structure of denitrifying bacteria from landscape water. The functional gene nirS was used as a functional marker to explore the community of denitrifying bacteria in the water and sediment of landscape water. Based on parameters of the water and sediment, the temporal and spatial distribution characteristics and driving factors of the community of denitrifying bacteria were studied. The results showed significant seasonal differences in water parameters and spatial differences in sediment nitrogen (P<0.001). No significant difference (P>0.05) was observed in α-diversity; the EC and SOEF-NH4+-N were important factors affecting the α-diversity of the water and sediment. Denitrifying bacteria mainly belonged to the phylum Proteobacteria and the genera Dechloromonas, Rhodocyclaceae, Pseudomonas, Rhodobacter, and Thauera. Principal coordinate analysis revealed that the community of denitrifying bacteria in the water and sediment exhibited significant spatial differences (P<0.001); keystone denitrifying bacteria in the water also exhibited significant spatial differences (P<0.001). RDA and RF analysis showed that the permanganate index and TP were the main environmental factors affecting the total and keystone denitrifying bacteria in the water; SOEF-NH4+-N, IEF-NH4+-N, and WAEF-NO3--N were the main environmental factors affecting the total and keystone denitrifying bacteria in the sediment. These findings could serve as a reference to understand the interaction mechanism between nitrogen and denitrification bacterial communities in landscape water.

[Spatial and Temporal Distribution of Aerobic Denitrification Bacterial Community in Sediments of Gangnan Reservoir].

In order to study the spatial and temporal distribution characteristics of aerobic denitrification bacteria in the sediments of Gangnan Reservoir, the aerobic denitrification bacterial community was analyzed using a MiSeq high-throughput sequencing technique based on the napA gene. Moreover, the composition, diversity, difference, and network analysis of the aerobic denitrification bacterial community were investigated. The results showed higher α-diversity (Chao1 index, Observed species index, and Shannon index) in autumn and winter than that in spring and summer; that is, the richness and diversity of sampling sites in autumn and winter were higher. In terms of spatial distribution, the Chao1 index, Observed species index, Shannon index, and Simpson index of the bacterial community in the sampling sites in the transition zone were higher than those in the sampling sites in the inflow area and the main reservoir area, indicating that the richness and diversity of the bacterial community in the sampling sites in the transition zone were the highest. The aerobic denitrifying bacteria in the sediments of Gangnan Reservoir mainly belong to Protebacteria. The first dominant class was ß-Proteobacteria, and the first dominant genus was Thauera. A Venn diagram analysis indicated that the community of aerobic denitrification bacteria exhibited significant spatial and temporal differences. At the spatial level, there were higher numbers of different species based on LEfSe analysis than that at the seasonal level. Among the marker species screened by random forest analysis, Comamonas had the highest contribution in all spatial sampling sites, whereas Pectobacterium had the highest contribution in all seasonal sampling sites. Network analysis showed that there were nine modules, including 565 edges of 297 nodes; 47 keystone species were obtained based on the indicator OTUs analysis and network analysis. The principal co-ordinates analysis revealed that keystone species in the spatial distribution exhibited significant differences (Adonis, P<0.001). The results of this study provide scientific basis for the separation and identification of efficient aerobic denitrifying bacteria.

A Measurement of 'Walking-the-Wall' Dynamics: An Observational Study Using Accelerometry and Sensors to Quantify Risk Associated with Vertical Wall Impact Attenuation in Trampoline Parks.

This study illustrates the application of a tri-axial accelerometer and gyroscope sensor device on a trampolinist performing the walking-the-wall manoeuvre on a high-performance trampoline to determine the performer dynamic conditions. This research found that rigid vertical walls would allow the trampolinist to obtain greater control and retain spatial awareness at greater levels than what is achievable on non-rigid vertical walls. With a non-rigid padded wall, the reaction force from the wall can be considered a variable force that is not constrained, and would not always provide the feedback that the trampolinist needs to maintain the balance with each climb up the wall and fall from height. This research postulates that unattenuated vertical walls are safer than attenuated vertical walls for walking-the-wall manoeuvres within trampoline park facilities. This is because non-rigid walls would provide higher g-force reaction feedback from the wall, which would reduce the trampolinist's control and stability. This was verified by measuring g-force on a horizontal rigid surface versus a non-rigid surface, where the g-force feedback was 27% higher for the non-rigid surface. Control and stability are both critical while performing the complex walking-the-wall manoeuvre. The trampolinist experienced a very high peak g-force, with a maximum g-force of approximately 11.5 g at the bottom of the jump cycle. It was concluded that applying impact attenuation padding to vertical walls used for walking-the-wall and similar activities would increase the likelihood of injury; therefore, padding of these vertical surfaces is not recommended.

[Spatial Distribution Characteristics of the Spectrum, Source Analysis, and Nitrogen Response of Dissolved Organic Matter in Summer Rainfall in the Hebei Province].

Dissolved organic matter(DOM) is an important component of the organic matter in the environment. This study explored the characteristics of DOM. The components and spectral characteristics of rainwater DOM were measured using Ultraviolet-visible absorption spectrum(UV-vis) and three-dimensional fluorescence spectrum in the Hebei province. The results showed significant differences for DOM molecular weight in the northern, central, and southern region; the DOM of the northern region exhibited the lowest molecular weight. Two humic-like(C1 and C4), one protein-like(C2) and one fulvic-like(C3) components were identified by parallel factor(PARAFAC) analysis. Component C2 had a significant positive correlation with components C3 and C4(P<0.001), which may have similar sources. The C2(protein-like substances) accounted for the major proportion of DOM with the average abundance 40.59%. The DOM components based on PARAFAC exhibited significantly difference between city and country regions without spatial difference, which was consistent with the result of fluorescence regional integration(FRI). The protein-like substances based on FRI were the main components, which accounted for 61.59%-89.01%. Redundancy analysis(RDA) showed that total nitrogen, nitrate, and ammonia were the main environmental factors determining the distribution of DOM. Spectral indices presented a significant difference between city and country regions. High fluorescence(FI) and biological(BIX) and low humification(HIX) values showed that summer rain exhibited the strong autochthonous and low humification characteristics, and country region have stronger autochthonous characteristics than city region. The regression analysis demonstrates that the prediction accuracy of rainwater quality parameters in city region is high. From all the results, rainwater DOM, showing strong autogenous characteristics, exhibited significant differences between city and country regions without spatial difference in Hebei. Meanwhile, it can also provide technical support for rainwater nitrogen concentration prediction based on DOM components.

[Structure of Aerobic Denitrification Bacterial Community in Response to Dissolved Organic Matter in Baiyangdian Lake During the Water Delivery Period].

Dissolved organic matter (DOM) plays an important role in the evolution of microbial communities. Meanwhile, ecological water delivery is an important feature of Baiyangdian Lake. To explore how the structure of the aerobic denitrification bacteria community responds to DOM during the water delivery period, the DOM components of water were examined and high-throughput sequencing of aerobic denitrification bacteria was performed. The results showed significant differences in DOM concentration in Baiyangdian Lake, with the estuary area exhibiting lower DOM concentrations. The water exhibited strong autogenous source, while DOM in the estuary area had a higher molecular weight and degree of humification. Three protein-like substances (C1, C2, and C4) and one humic-like substance (C3) were identified through PARAFAC. The protein-like substances accounted for the major proportion of DOM, which was consistent with the results of fluorescence regional integration (FRI). The genera of the water body were mainly in the Protebacterice phylum, including Cupriavidus, Aeromonas, Thauera, Shewanella, and Pseudomonas. Meanwhile, Cupriavidus, Thauera, Shewanella, Agrobacterium, and Pseudomonas were the main indicator species, according to random forest (RF) analysis. Through network analysis, 35 key nodes of the network were obtained, belonging to Thauera, Cupriavidus, and Unclassified_bacteria, respectively. Redundancy analysis (RDA) showed that a humic-like substance was the main environmental factor regulating the whole structure of the aerobic denitrification bacterial community, while protein-like substances played important roles in changes to the indicator species and key nodes of the community. Overall, protein-like substances could provide an important reference for selecting carbon sources during the screening of efficient and cold resistance aerobic denitrification bacteria that are adapted to actual water bodies.

[Temporal and Spatial Evolution Characteristics of DOM Spectra in Sediment Interstitial Water in Typical Zones of Baiyangdian Lake].

The sources and distribution of dissolved organic matter (DOM) in the interstitial water of Baiyangdian Lake sediments were analyzed using the ultraviolet-visible absorption spectrum (UV-vis) method and three-dimensional excitation emission matrix fluorescence spectroscopy-parallel factor analysis (EEM-PARAFAC). Results showed that the DOM concentrations and molecular weight were significantly higher in summer than in spring and autumn, based on a254 and E2/E3 values. Three protein-like substance (C1, C2, and C3) and two humic-like substances (C4, C5) were identified with the PARAFAC model. Moreover, protein-like substances accounted for the majority of DOM, reaching (63.56±16.07)%. Total DOM fluorescence intensity, the fluorescence intensity of each component, and the relative abundance exhibited significant spatial variation among the different functional zones in Baiyangdian Lake. Protein-like substances were mainly found in the breeding area, whereas humic-like substances mainly occurred in the natural area. The high BIX, FI, ß:α, and low HIX indicated that DOM in sediment interstitial water exhibited low humification and highly autochthonous characteristics. Moreover, the perfect regression equations between water quality and the fluorescent components could provide a useful reference for managers aiming to protect the ecosystem of Baiyangdian Lake.