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Swimming pools adopt chlorination to ensure microbial safety. Giardia has attracted attention in swimming pool water because of its occurrence, pathogenicity, and chlorine resistance. To control Giardia concentrations in pool water and reduce the microbial risk, higher chlorine doses are required during disinfection. Unfortunately, this process produces carcinogenic disinfection byproducts that increase the risk of chemical exposure. Therefore, quantitatively evaluating the comparative microbial vs. chemical exposure risks that stem from chlorination inactivation of Giardia in swimming pool water is an issue that demands attention. We simulated an indoor swimming pool disinfection scenario that followed common real-world disinfection practices. A quantitative microbial risk assessment coupled with a chemical exposure risk assessment was employed to compare the Giardia microbial exposure risk (MER) and the trihalomethane chemical exposure risk (CER) to humans. The results demonstrated a 22% decrease in MER- and CER-induced health exposure risk, from 8.45E-5 at 8:00 to 6.60E-5 at 19:00. Both the MER and CER decreased gradually, dropping to 3.26E-5 and 3.35E-5 at 19:00, respectively. However, the CER exceeded the MER after 18:30 and became the dominant factor affecting the total exposure risk. Past the 18 hr mark, the contribution of trihalomethane CER far exceeded the risk aversion from microbial inactivation, leading to a net increase in total exposure risk despite the declining MER. Swimmers may consider swimming after 19:00, when the total exposure risk is the lowest. Lowering water temperature and/or pH were identified as the most sensitive factors to minimize the overall health exposure risk. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) flower-like NiCo 2 O 4 (F-NiCo 2 O 4 ) is synthesized through using graphene oxide (GO) as “designer additives” to induce Ni-Co 1,3,5-benzenetricarboxylate metal-organic framework (Ni-Co-BTC MOF) from nanoparticles to form nanoneedles, and then further self-assembles to a 3D flower-like morphology. A possible process of morphological change is described in detail according to the changing amount of GO and reaction time. The as-prepared unique structure constructed by ultrafine subunits exhibits a high specific surface area (152.8 m 2  g −1 ) and plentiful mesopores. As an anode in lithium-ion battery, F-NiCo 2 O 4 shows a high capacity of 1167 mA h g -1 at a current density of 200 mA g −1 and even maintains 333 mA h g -1 at a high rate of 5000 mA g −1 . Moreover, the 3D flower-like F-NiCo 2 O 4 remains a high capacity of 1067 mA h g -1 at 1000 mA g −1 after 400 cycles. The novel method in this work paves a new way to form 3D structure by using GO to induce MOF aggregation, which may be extended to preparing other metal/metal oxides materials for electrochemical energy-storage systems. [ABSTRACT FROM AUTHOR]

Owing to its combination of superior natural conditions and abundant resources, the Pearl River Delta (PRD), China, is densely populated, with concentrated industry and rapid development. The PRD is also one of the most threatened estuaries in the world, as it has been exposed to an increasing series of crises related to water resources. Water conflict, water pollution, and saltwater intrusion have all increased dramatically in the past few decades, which pose a threat to regional water security and impose constraints on regional development. The goal of this paper is to analyze the causes and impacts of some of the water resource crises faced by estuaries under dramatically changing environments, based on studies in the PRD. The PRD is centered around the Pearl River Estuary (PRE) and is the second most economically active district in China. Rapid economic development and a population boom have resulted in an average annual growth rate of 1.43% in water resource demand, which has further accelerated water pollution by a substantial growth in sewage discharge. Water pollution results in the impairment of the ecological functions of the water, and the standard rate of water function areas in the PRD remains under 50%. Large-scale and uneven sand excavations not only decreased the river discharge from upstream but also allowed more tidal prisms to enter, which triggered severe saltwater intrusion. Meanwhile, sea-level rise and changing wind patterns also contribute to increasingly severe saltwater intrusion, which was characterized by gradual increases in salinity, as well as more prolonged periods of higher salinity that exceeds acceptable thresholds occurring earlier in the year. This study is intended to bring attention to these challenging issues and provide some of the information needed to advance research into sustainability assessment of the water resources. [ABSTRACT FROM AUTHOR]

Biogenic gas production can be improved by activating coal microorganisms, which is of great significance and application value to increase the production of coalbed methane. However, it remains poorly understood about the biological mechanism of the cultivable bacteria in coals that enhance gas production. In this study, cultivable bacteria in coal were enriched by minimal salts plus yeast medium, and coal was cultured with these medium-removed bacteria cells in minimal salts medium. Metagenomics was used to analyze the differences in the microbial composition and function. The results showed that cultivable bacteria caused large changes in the microbial and functional structure in the coals, and the cultivable bacteria Bacillus dominated in the treated coal (88.74 ± 0.51%). Metagenomics analysis showed that the KEGG Orthologs from four methanogenesis pathways in cultivable bacteria treated coals were detected, these pathways were CO 2 to methane, methanol to methane, acetate to methane, and using methyl-CoM as the terminal methyl carrier. Importantly, the cultivable bacteria mainly increased the functional genes related to the degradation of benzoate, fatty acids, fluorobenzoate, xylene and aromatic compound, and further increased the acetate content. In addition, metagenome-assembled genome analysis showed that the pta and cysK genes mainly originated from Bacillus , which was beneficial to acetate production. And the cultivable bacteria treated coals had a higher methane emission than the control groups. In summary, cultivable bacteria can enhance biogas production by enhancing organic matter degradation and acetate pathway, which is of great importance for increasing coalbed methane production by domestication. [Display omitted] • Bacillus dominated in the coals treated by cultivable bacteria. • Cultivable bacteria treatment increased the organic degradation genes in coals. • Bacillus from cultivable bacteria dominated the acetate production for methanogenesis. [ABSTRACT FROM AUTHOR]

• A sigmoid CO 2 concentration stress function f (Ca) was proposed to reflect ET response. • A process-based transpiration model was extended with the f (Ca) to model total ET. • The model with CO 2 stress is sound and robust to couple water and carbon processes. • The mechanism of CO 2 effect and advantage of a f (Ca) in ET models were discussed. Evapotranspiration (ET) is one of the most difficult hydrologic variables to estimate. In the context of climate change, the rise of CO 2 emissions may improve photosynthesis but depress transpiration thus increasing plant water use efficiency (WUE). Therefore, it is of great importance and necessity to take elevated atmospheric CO 2 concentration (Ca) as a limiting factor for improved assessment of ET and WUE toward a better ecosystem management. In this study, we developed and incorporated a Ca stress function into a modified process-based transpiration model and extended its application from transpiration to total evapotranspiration simulation. The original simplified process-based model (denoted as BTA by combining developers' last name initials), previously modified version with added soil moisture (BTA-θ) and the extended version in this study with CO 2 concentration (BTA-Ca) were tested for daily ET simulation at the Dinghushan forest ecosystem in south China. The results show that eddy covariance based forest ET was well simulated by the models, while the two modified models outperformed the original one. Despite the limited improvement of accuracy, the BTA-Ca model is more superior and meaningful regarding the physical mechanisms. Moreover, we evaluated the biophysical responses of ET and GPP to the major environmental factors, which shows that ET and GPP responded similarly to environmental changes with close linkages between the two. This study proposed a Ca stress function and provides an effective way of coupling water and carbon exchange processes for ET simulations, which can be applied for forest water budget assessment under climate change. [ABSTRACT FROM AUTHOR]

Phycobiliprotein is a homologous family of light-harvesting chromoproteins existing in cyanobacteria, red algae and cryptophytes. Phycobiliprotein is made up of phycobilin and its corresponding apophycobiliprotein, and they are covalently linked by the thioether bond with the bilin lyase. Using the software BLAST, we have found gene slr2049 in Synechocystis sp. PCC6803 homologous to the biliprotein lyase gene cpeS . This paper investigates the protein expressed by gene slr2049 to find the enzymatic activity characteristics. We cloned slr2049 and its related genes cpcB , ho1 , and pcyA which are linked with the synthesis of phycocyanin. Special amino acid mutagenesis was performed on slr2049 to construct eight mutants slr2049 (H21S), slr2049 (L23S), slr2049 (A24S), slr2049 (F25S), slr2049 (W72L), slr2049 (G84S), slr2049 (R107S) and slr2049 (Y124S). These mutants were ligated with vectors pEDFDuet-1 and pET-23a to construct pCDF- cpcB - slr2049 wild-type, pCDF- cpcB - slr2049 mutants and pET- ho1 - pcyA , for the purpose of protein expression and analysis. The results showed that the wild-type and mutants slr2049 (H21S), slr2049 (L23S), slr2049 (F25S), slr2049 (W72L), slr2049 (G84S), and slr2049 (Y124S) can catalyze CpcB to couple on PCB correctly and the products have unique spectral characteristics. However mutants slr2049 (A24S) and slr2049 (R107S) have no spectral characteristics. Thus, it is suggested that alanine at position 24 and arginine at position 107 are the active sites. [ABSTRACT FROM AUTHOR]

Abstract: The Modaomen Waterway (MW), a major outlet of the Pearl River Estuary, is a crucial source of water supply for Macao and Zhuhai City in Southern China. This waterway is frequently affected by saltwater intrusion from the South Sea, which has caused serious water shortage in recent years. For the planning and management of water supply at this waterway it is necessary to understand the characteristics of saltwater intrusion particularly in the low flow period of the year. However, as a result of multiple impacts from tide, river discharge, wind, topography, channel bathometry, and some other factors, the saltwater intrusion into this waterway is highly non-linear. In order to account for the non-linear characteristics, the wavelet method was used to analyze the period characteristics of tidal range, river discharge, and salinity and the impact of tidal range and river discharge on the salinity. Results show that the tidal range at Sanzao station and the salinity at Pinggang station both exhibit a stable 14.8-day period and the salinity in the MW is largely impacted by the tidal range during low stream flow periods. River flows from upstream of the waterway don't show any stable period characteristic, it, however, is critical in mitigating the salinity for water supply during saltwater intrusion. A minimum total flow of 2 500 m3/s from upstream at Sanshui and Makou stations has been practiced as a threshold for safe water supply. This study has found that the percent time when salinity is below the maximum permissible salinity of 250 ml/g for water supply increases as the river discharge from upstream increases and up to 50–70% of the time the salinity at water supply pumping station is below 250 mg/l when the upstream flow is greater than 2 500 m3/s. Planning and management of water supply operation at the MW is politically, economically and mostly importantly technically challenging, findings from this study can provide some guidance for operation and further research. For example, the phase lag of average salinity to tidal range was quantified to be 3.4–3.8 days. This phase lag time would suggest that the pumping operation to store freshwater in the backup storages needs to be at least 4–5 days ahead of the spring tide so as to avoid serious impact from saltwater intrusion. Safer water supply strategies can be developed by scheduling reservoir operations to maintain the threshold stream flow and the pumping. [Copyright &y& Elsevier]

[Display omitted] • Mild impact of climate extremes on vegetation was found for Hu Line transect in China. • Latitudinal and altitudinal patterns of vegetation responses to climate were analyzed. • Non-woody plants in the mid-to-high latitudes were more sensitive to climate extremes. • Productivity above 45°N increased with drought severity due to favorable environment. • Policy making suggestions were proposed with emphasis on the identified hotspots. Climate projections infer increasing frequency of extreme events in the future which would alter terrestrial hydrologic functioning and ecosystem services. Understanding the responses of vegetation to extreme events can provide prerequisite knowledge to mitigate climate change impacts. The relationships between climate extremes and vegetation phenology and productivity were examined for a transect along the Hu Line across China during 1988–2014. Results show that high frequency and severity of droughts existed in the mid-latitude regions where happened to be mostly occupied by grassland and cropland with relatively low productivity compared to trees. Prolonged growing seasons (4.3 days/decade) resulted mostly from advanced green-up were observed over the transect. No strong impact of extreme droughts on vegetation was observed for any plant functional types, due to the timing of drought occurrences primarily in pre- and post-growing seasons while water supply was likely not so limited during growth indicated by a drought index. Non-woody plants in the mid-to-high latitudes (37-54°N) were identified more sensitive to climate extremes than woody plants in the low latitudes. Meanwhile, grassland in the relatively low-elevation areas (<1000 m.a.s.l) was more responsive than that in the high-elevation areas. Productivity above 45°N increased with drought severity attributable to an intensified favorable environment during frequent and mild droughts with warmer temperature and increased solar radiation. The results may suggest the generally relative stability of the ecosystems along the Hu Line, however, with further deteriorating climate, the stable relationships between climate and ecosystems may be shifted, likely starting from low-elevation grassland. [ABSTRACT FROM AUTHOR]

The saltwater intrusion seriously threatens the water supply security of estuaries, while the existing salty blocking measures (e.g., gates and dams) are rude and the dynamic mechanism is not fully considered. In order to investigate countermeasures to reduce the risk of the saltwater intrusion, as well as enrichment blocking methods, in this paper, the salt-inhibiting properties of air curtain under tidal action was investigated based on a long-distance physical flume with dual tidal-salinity control capability. Experimental results indicate that air curtains significantly diminish distance of saltwater into estuaries. The bubble plumes, on the one hand, promote vertical mixing, elevating high-salinity water from the depths to the surface, thereby disrupting the vertical circulation structure of salt wedge. On the other hand, the energy dissipation and barrier effect produced by bubble bursting can significantly reduce the momentum of the invading saltwater. Meanwhile, the research emphasizes that the salt intrusion length is negatively correlated with the airflow discharge, whereas the salty-blocking effect prefer better of the weakly-mixed estuary than the strongly-mixed. Most importantly, the air curtain mixing coefficient k a were proposed at the first time to quantify the salty blocking effect. The mixing coefficient k a is the function of airflow discharge Q a and tidal current u t , demonstrating a direct proportionality to Q a and u t − 1. Moreover, a quantitative relationship between k a and Q a / u t was obtained from experimental results. The research results would help inform the flexible salt-inhibiting measures of estuarine air curtain. • The effect and influencing factors of air curtain salinity inhibition under runoff-tidal condition was explored. • The salt-inhibiting mechanism and application conditions of air curtain are proposed. • The air curtain mixing coefficient k a was proposed, and the quantitative relationship between k a , Q a and u t was derived. [ABSTRACT FROM AUTHOR]

• A powder-scale high precision multi-physics model is developed to depict the DED-LB process. • The single-track Inconel 718 alloy DED-LB experiments are used to validate the powder scale model and GPR model results. • The physically based-data driven agent model is developed to rapidly and accurately predict the geometry and dilution rate. • The DED-LB PS-ML model for optimal process maps is developed to achieve process parameter optimization using a comparatively small accurate data. The major challenge faced is the definition of optimal process variables for rich quality of fabricated parts in laser-based directed energy deposition (DED-LB) processes. However, predicting the optimal process scheme using machine learning models is still challenging owing to the need for a large amount of training experimental data with high costs in DED-LB. In view of this, a physical simulation (PS)-machine learning (ML) model using a relatively small accurate data set of 31 simulation data for optimal process schemes is proposed in DED-LB process in this study. Firstly, a powder-scale high precision phenomenon model incorporating the mass transfer, phase transformations and heat transfer and using Lagrangian particle model to add mass is developed to depict the DED-LB process. Then, a Gaussian process regression (GPR) agent model is established to rapidly and accurately predict the geometry and dilution rate of deposition tracks under different manufacturing parameters based on the high precision simulation results. Finally, a PS-ML model for process parameter optimization is developed using the particle swarm algorithm (PSO), and the optimized parameters are experimentally validated. The results show that the developed powder-scale model and GPR model results are consistent with the Inconel 718 alloy experimental results. The proposed PS-ML model can increase the accuracy of the ML models even with a small simulation data set. None of PS-ML model optimization results has a relative error of more than 3% to the experimental results, and the dilution rate is reduced by up to 61.66% compared to the experimental design parameters without optimization. The proposed physical simulation-machine learning model in this study enables inexpensive and accurate optimization of DED-LB process parameters. [ABSTRACT FROM AUTHOR]

Studies have shown that Sacubitril/valsartan (Sac/Val) can reduce myocardial inflammation in myocarditis mice, in addition to its the recommended treatment of heart failure. However, the underlying mechanisms of Sac/Val in myocarditis remain unclear. C-type natriuretic peptide (CNP), one of the targeting natriuretic peptides of Sac/Val, was recently reported to exert cardio-protective and anti-inflammatory effects in cardiovascular systems. Here, we focused on circulating levels of CNP in patients with acute myocarditis (AMC) and whether Sac/Val modulates inflammation by targeting CNP in experimental autoimmune myocarditis (EAM) mice as well as LPS-induced RAW 264.7 cells and bone marrow derived macrophages (BMDMs) models. Circulating CNP levels were higher in AMC patients compared to healthy controls, and these levels positively correlated with the elevated inflammatory cytokines IL-6 and monocyte count. In EAM mice, Sac/Val alleviated myocardial inflammation while augmenting circulating CNP levels rather than BNP and ANP, accompanied by reduction in intracardial M1 macrophage infiltration and expression of inflammatory cytokines IL-1β, TNF-α, and IL-6. Furthermore, Sac/Val inhibited CNP degradation and directly blunted M1 macrophage polarization in LPS-induced RAW 264.7 cells and BMDMs. Mechanistically, the effects might be mediated by the NPR-C/cAMP/JNK/c-Jun signaling pathway apart from NPR-B/cGMP/NF-κB pathway. In conclusion, Sac/Val exerts a protective effect in myocarditis by increasing CNP concentration and inhibiting M1 macrophages polarization. [Display omitted] [ABSTRACT FROM AUTHOR]

• Coal chemical components and structures affected by acidification and THF are studied. • Effect of successive treatments of acidification and THF on pore fractal features is analyzed. • Relationship between SSA, average pore size and fractal parameters are discussed. • Successive treatments of acidification and THF could well improve pore development. Chemical solvents could change coal components and effectively enhance conductivity of coal reservoir, which is beneficial to efficient methane extraction. Relationship between coal chemical structure parameters and main functional groups variations affected by acidification and tetrahydrofuran (THF) is investigated through infrared spectroscopy tests and curve peak fitting. Meanwhile, variations in fractal dimensionality and pore structure characteristics are studied by adopting low-temperature nitrogen adsorption tests and Frenkel-Halsey-Hill (FHH) fractal model. Main results are: (1) After extracting raw coal and acidified coal using THF with varying concentrations, absorbance of aromatic hydrocarbon –CH surface and aromatic methyl bond become weaker. While the proportion of substituted aromatic hydrocarbons increases in acidified coal than in raw coal. Acidification treatment could reduce strength of C-O-C absorption peak. Proportion of CH 2 and CH 3 in raw coal decreases with increasing THF concentration, indicating that THF could react with aliphatic structure to reduce CH 2 and CH 3 content. Extraction with THF dissolves aromatic structure, lowering C = C content in coal to different degrees. (2) Acidification pretreatment could produce more micropores in coal samples. Micropore contents of acidified coal after THF extraction are all lower than coal sample S, while transition pores and mesopores contents are both higher than those in coal sample S. (3) Fractal dimension D 1 of raw coal indicates a relatively linear relationship with specific surface area, while the D 1 of acidified coal is less correlated with specific surface area. The factor D 2 shows a linear relationship with average pore size. After treatment of THF, average pore size of raw coal increases with D 2 , while that of acidified coal varies in different degrees with uneven distribution of pore sizes. [ABSTRACT FROM AUTHOR]

Abstract Floods introduced by rainfall events are responsible for tremendous economic and property losses. It is important to delineate flood prone areas to minimize flood damages and make mitigation plans. Recently, there has been recognition of the need to understand the risk from groundwater flooding caused by the emergence of groundwater at the ground surface. Mapping groundwater flood risk is more challenging compared to river flooding, especially in karst systems, where subsurface preferential flowpaths can affect groundwater flow. We developed a coupled surface-subsurface modelling framework resolving spatial information and hydrologic data to assess the groundwater flood risk at a karstic watershed: Koiliaris River Basin, Greece. The simulated groundwater table was used to delineate groundwater flooding. Modelled results revealed the role of faults in groundwater flooding generation. We anticipate the coupled surface-subsurface approach to be a starting point for more sophisticated flooding risk assessment, including magnitude and temporal duration of groundwater flooding. Highlights • Coupled surface-subsurface modelling of a mountainous watershed. • Modelling result explicitly shows spatial-temporal dynamics of groundwater flooding. • Faults increase the area of groundwater flooding and reduce response time. • Groundwater flooding causes more than 10 times higher agricultural loses than river flooding. • This study has highlighted the value of coupled hydrologic models in groundwater flooding assessment. [ABSTRACT FROM AUTHOR]

Fluorescent dissolved organic matter (FDOM) in surface water has broad implications on water quality research and operations. Solid phase extraction (SPE) is the most widely used technique to extract FDOM. However, fluorescent elution preferences by common solvents and content of quantifiable chromophores in waste fraction remain largely unknown, both quantitatively and qualitatively. In this work, the preferential selection of various types of FDOM captured by and lost from SPE as characterized by the fluorescence excitation-emission matrix (EEM) were investigated. Three elution solvents (methanol, acetone, and dichloromethane) were adopted to elute the DOM that was enriched on a typical SPE sorbent. Results revealed that high polarity (methanol) and medium polarity (acetone) solvents eluted the highest variety and quantity of humic acid-like substances (Region V), while the low polarity (dichloromethane) elution solvent was more suitable for eluting tyrosine (Region I) and tryptophan (Region II). Compared to eluting only with methanol, sequential elution and recombination using the three aforementioned solvents demonstrated a significant increase in not only DOC recovery (by 7%), but fluorescence integral values and fluorescence characteristics covering collectively much larger fluorescence regions that more closely resembled raw water. For the first time, the fluorescence EEM of waste after loading the sample revealed a previously overlooked FDOM loss of 20%, caused by ineffective adsorption onto the solid phase resin. Substantial carbonaceous and nitrogenous FDOM were present in this fraction (the fluorescence intensity of aromatic protein in waste exceeds 20% of that in raw water), indicating possible underestimations of FDOM-related research in areas such as disinfection byproduct and toxicity work. The results of this study provide both a qualitative and quantitative characterization of the elution and lost products of SPE in capturing FDOM. [Display omitted] • 20% of DOM was ineffectively adsorbed by HLB during sample loading stage. • Common elution solvent methanol performed best for DOM elution on HLB. • Selective enrichment of fluorophores was realized following elution solvent preference for FDOM. [ABSTRACT FROM AUTHOR]

• Actinobacterial diversity and copy number were closely related to methanogenic potential. • Propionibacterium was the biggest contributor to methanogenic potential. • Actinobacteria indirectly affect methanogenic potential by controlling negative cohesion. Microorganisms are the core drivers of coal biogeochemistry and are closely related to biological coalbed methane. However, the Actinobacterial taxa in coals and their roles in the context of biological coalbed methane remain poorly understood. In this study, 16S rRNA gene sequencing and quantitative PCR were used to analyze the Actinobacterial taxa and abundance in coals from different regions of China. The results indicated that Proteobacteria was the predominant bacterial phylum, and Actinobacteria accounted for only 1.64 % of the coal bacterial communities. However, Actinobacteria was the largest contributor to methanogenic potential, followed by Firmicutes and Cyanobacteria. The Shannon diversity, structure and absolute abundance of Actinobacteria were closely related to methanogenic potential. In addition, widely detected genera included Propionibacterium , Corynebacterium , Brevibacterium , Arthrobacter , Micrococcus , Phycicoccus and Brachybacterium , all of which belong to the order Actinomycetales. Among them, Propionibacterium was the most important genus contributing to the methanogenic potential, followed by Corynebacterium and Phycicoccus. In the microbial co-occurrence network, actinobacterial-related nodes and links accounted for 18.29 % and 33.16 % of the total nodes and links, respectively, and actinobacterial OTUs belonging to the genera Propionibacterium , Corynebacterium , Arthrobacter , Dietzia , Phycicoccus , Rhodococcus and Micrococcus were identified as connectors. Furthermore, partial least squares path modeling indicated that Actinobacteria can affect methanogenic potential indirectly by controlling community negative cohesion. In summary, Actinobacteria appear to play important roles in maintaining the microbial co-occurrence network and regulating coal biological methanogenic potential, which is help to understand the coal microbial ecology and geochemical processes. [ABSTRACT FROM AUTHOR]

Asymbiotic nitrogen fixation in the subsurface of mine soils is often neglected despite it playing an important role in the ecological restoration of mine soils. Here, we examined the effect of artificial root exudates on the community structure of asymbiotic diazotrophs in the subsurface of mine soils by simulating the oxygen conditions in the root zone of mine soils via application of three artificial root exudates under two oxygen states (oxygen deficiency with 10% oxygen and anaerobic) in microcosm experiments and 16S rRNA and nifH mRNA transcript analysis. The results showed that the three artificial root exudates significantly increased the nitrogen fixation ratio in mine soils under both the anaerobic and oxygen deficiency conditions, and the mine soils treated with the same artificial root exudates showed a higher nitrogen fixation ratio in the oxygen deficiency condition than in the anaerobic condition. The effects of different artificial root exudates on the bacterial and diazotrophic α-diversity indexes were significantly different. In addition, artificial root exudates can change the structures of bacterial and diazotrophic communities. Furthermore, artificial root exudates significantly increased the abundance of Clostridium , which are not the dominant bacteria responsible for asymbiotic nitrogen fixation in subsurface mine soils. In parallel, artificial root exudates mainly stimulated sulfate-reducers and uncultured bacteria for nitrogen fixation. This study is of great importance to strengthen our understanding of the nitrogen fixation dynamics in the ecological restoration of abandoned mining lands. • Selective effect of root exudates on diazotrophs was found in different oxygen conditions. • Artificial root exudates stimulated the sulfate-reducers for nitrogen fixation. • A higher nitrogen fixation ratio in oxygen deficiency condition [ABSTRACT FROM AUTHOR]