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An in - situ partial conversion strategy is proposed and employed to successfully synthesize a lead-free halide perovskite-based S-scheme heterojunction of Cs 3 Bi 2 Br 9 /BiOBr, which exhibits swift transfer and separation of photogenerated carriers and thus significant improvement in photocatalytic N 2 reduction activity compared to traditional electrostatic self-assembled heterojunction. [Display omitted] The judicious construction of interfaces with swift charge communication to enhance the utilization efficiency of photogenerated carriers is a viable strategy for boosting the photocatalytic performance of heterojunctions. Herein, an in-situ partial conversion strategy is reported for decorating lead-free halide perovskite Cs 3 Bi 2 Br 9 nanocrystals onto BiOBr hollow nanotube, resulting in the formation of an S-scheme heterojunction Cs 3 Bi 2 Br 9 /BiOBr. This unique in-situ growth approach imparts a closely contacted interface to the Cs 3 Bi 2 Br 9 /BiOBr heterojunction, facilitating interfacial electron transfer and spatial charge separation compared to a counterpart (Cs 3 Bi 2 Br 9 :BiOBr) fabricated via traditional electrostatic self-assembly. Additionally, the establishment of an S-scheme charge transfer pathway preserves the robust redox capability of photogenerated carriers. Furthermore, the free electron transfer from Cs 3 Bi 2 Br 9 to BiOBr promotes the activation of the N N bond and diminishes the energy barrier associated with the rate-determining step in the N 2 reduction process. Consequently, the Cs 3 Bi 2 Br 9 /BiOBr heterojunction exhibits highly selective photocatalytic N 2 reduction to NH 3 (nearly 100 %) at a rate of 130 μmol g−1 h−1 under simulated sunlight (100 mW cm−2), surpassing BiOBr, Cs 3 Bi 2 Br 9 , and Cs 3 Bi 2 Br 9 :BiOBr by factors of 6, 4, and 2, respectively. [ABSTRACT FROM AUTHOR]

Carbon catalysts have shown promise as an alternative to the currently available energy-intensive approaches for nitrogen fixation (NF) to urea, NH3, or related nitrogenous compounds. The primary challenges for NF are the natural inertia of nitrogenous molecules and the competitive hydrogen evolution reaction (HER). Recently, carbon-based materials have made significant progress due to their tunable electronic structure and ease of defect formation. These properties significantly enhance electrocatalytic and photocatalytic nitrogen reduction reaction (NRR) activity. While transition metal-based catalysts have solved the kinetic constraints to activate nitrogen bonds via the donation-back-π approach, there is a problem: the d-orbital electrons of these transition metal atoms tend to generate H-metal bonds, inadvertently amplifying unwanted HER. Because of this, a timely review of defective carbon-based electrocatalysts for NF is imperative. Such a review will succinctly capture recent developments in both experimental and theoretical fields. It will delve into multiple defective engineering approaches to advance the development of ideal carbon-based electrocatalysts and photocatalysts. Furthermore, this review will carefully explore the natural correlation between the structure of these defective carbon-based electrocatalysts and photocatalysts and their NF activity. Finally, novel carbon-based catalysts are introduced to obtain more efficient performance of NF, paving the way for a sustainable future. [ABSTRACT FROM AUTHOR]

Stream ecosystems exhibit high degrees of spatial heterogeneity at nested scales from microhabitats to regions. This heterogeneity may facilitate the co-occurrence of biogeochemical processes that are favored under incompatible environmental conditions, like dinitrogen (N2 gas) fixation and denitrification. We hypothesized that environmental variation at the patch scale (1–10’s m) would facilitate the co-occurrence of N2 fixation and denitrification through the formation of hot spots. We measured rates of N2 fixation and denitrification and relative abundances of nifH and nirS (genes that encode for the enzymes nitrogenase and nitrite reductase, respectively) in patches determined by channel geomorphic units and substratum type in seven streams encompassing a gradient of N and P concentrations. We found hot spots, where rates of N2 fixation and denitrification were 1–4 times higher than reach-average rates, in all study streams. Most N2 fixation hot spots were in patches with rock substrata, while denitrification rates and relative abundances of nifH and nirS were higher in patches with fine sediment. Yet, in one of the streams, the same patches hosted rates in the top 25% of all patches for both denitrification and N2 fixation. Across all streams and patches, organic matter and dissolved oxygen concentrations were important predictors of rates of N2 fixation, denitrification, and nifH relative abundance, while P concentration was important to N2 fixation and denitrification. Our results demonstrate that understanding the spatial ecology of microbially driven nutrient cycling is required to characterize nutrient fluxes more completely in stream ecosystems. [ABSTRACT FROM AUTHOR]

The solutions for environmental remediation and renewable energy generation have intensified the exploration of efficient photocatalytic materials. Recently, the composites of g-C3N4 and MXene have gained considerable interest for their potential applications in photocatalysis. In the g-C3N4-MXene composite, the g-C3N4 possesses unique physical, chemical, and optical properties to increase visible light absorption. At the same time, MXene improves conductivity, adsorption of reactant molecules or the active sites, and charge transfer properties. Combining the unique physico-chemical properties of MXene and g-C3N4, the resulting composite exhibits superior photo-responsive behavior and is critical in photocatalytic reactions. Furthermore, the g-C3N4-MXene composite exhibits stability and recyclability, making it a promising candidate for sustainable and scalable photocatalytic material in environmental remediation. This review offers an in-depth analysis of the development and design of g-C3N4-MXene composites through diverse synthesis procedures and a comprehensive analysis of their application in carbon dioxide (CO2) reduction, photocatalytic degradation, water splitting processes, mainly hydrogen (H2) generation, H2O2 production, N2 fixation, and NO x removal. The charge transfer mechanism of g-C3N4-MXene composite for photocatalytic application has also been discussed. This review provides insights into the photocatalytic capabilities of g-C3N4-MXene composites, showing their potential to address current environmental challenges and establish a robust foundation for sustainable energy conversion technologies. [ABSTRACT FROM AUTHOR]

Air contains carbon, hydrogen, oxygen, and nitrogen elements that are essential for the constitution of amino acids. Converting the air into amino acids, powered with renewable electricity, provides a green and sustainable alternative to petrochemical‐based methods that produce waste and pollution. Here, taking glycine as an example, we demonstrated the complete production chain for electrorefining amino acids directly from CO2, N2, and H2O. Such a prospective Scheme was composed of three modules, linked by a spontaneous C−N bond formation process. The high‐purity bridging intermediates, separated from the stepwise synthesis, boosted both the carbon selectivity from CO2 to glycine of 91.7 % and nitrogen selectivity from N2 to glycine of 98.7 %. Under the optimum condition, we obtained glycine with a partial current density of 160.8 mA cm−2. The high‐purity solid glycine product was acquired with a separation efficiency of 98.4 %. This work unveils a green and sustainable method for the abiotic creation of amino acids from the air components. [ABSTRACT FROM AUTHOR]

Formation of symbioses with eukaryotic organisms is one of the major strategies for evolution of bacteria, accompanied by pronounced changes in their genetic organization. Eukaryotes provide their micropartners with nutrients and ecological niches, while bacteria perform trophic or protective functions useful for their hosts. Acquisition of the ability for symbiosis is associated with formation of specialized sym gene systems, which is often accompanied by structural modifications of the bacterial genome. Nodule bacteria (rhizobia) are N2-fixing symbionts of leguminous plants; most of them are α-proteobacteria of order Hyphomicrobiales. In this group, symbiogenic genome modifications vary depending on the taxonomic position. In the evolutionarily primary rhizobia of family Bradyrhizobiaceae, which emerged directly from free-living N2 fixers, transition to symbiosis was accompanied by a significant (by 1.5–2 times) increase in the genome size. However, their genomes have retained a unitary structure: most Bradyrhizobium strains carry more than 95% of genes in their chromosomes. Secondary rhizobia of the family Phyllobacteriaceae (Mesorhizobium, Phyllobacterium), which emerged by transfer of sym genes into soil bacteria, demonstrate various stages of multipartite genome formation where a significant part of genes is located in extrachromosomal elements (ECEs): plasmids and chromids. The multipartite genome structure is the most pronounced in members the family Rhizobiaceae (Rhizobium, Sinorhizobium, Neorhizobium): the total size of ECEs containing sym genes can exceed the size of the chromosome. In these bacteria, the transfer from tropical to temperate ecosystems was accompanied by a narrowing of the host specificity. However, modification of the genome structure was revealed only in members of Sinorhizobium, with proportion of ECEs reaching up to 52% of the total genome. Similar genome structure is observed in associative (rhizospheric or endophytic) N2 fixers of the genus Azospirillum, in which ECEs comprise up to 60% of a genome. Rhizobia can also form bacteroids: irreversibly differentiated N2-fixing cellular forms included into symbiosomes, temporary organelles that can be considered as precursors of N2-fixing organelles found in some protists. Construction of such organelles in crop plants represents a promising direction in plant bioengineering research. [ABSTRACT FROM AUTHOR]

Undoubtedly, electrochemical ammonia synthesis without carbon footprint will be an anticipated alternative to the Haber-Bosch N2-fixation process which is energy-intensive. Herein, the durian shell derived carbon was designed as the electrocatalyst precursor, and its graphene-like morphology features and unique hierarchic pore structure obtained by controlling calcination condition was used to trap the N2 molecules firmly and convert them. Furthermore, the NH3 synthesis properties with N, S doping and co-doped were systematically tested. Detailed investigations shown the synergistic effect brought by N and S atom double doping strategy was efficient promote the increase of electrochemical active sites and thus enhanced the electrocatalytic performance. The NH3 yield of 32.05 µgNH3mgcat. −1 h− 1 was obtained by double-doped strategy, which enriched the application of biomass derived carbon materials. [ABSTRACT FROM AUTHOR]

Ocean temperature, redox state, circulation, and nutrient levels regulate the marine nitrogen (N) cycle, yet their specific impacts during greenhouse intervals remain poorly understood. Here, we examined the Smithian–Spathian hyperthermal event (∼250.5 Ma) during the Early Triassic greenhouse using stable N isotopes (δ15N) from sedimentary records in the Nanpanjiang Basin and Northern Yangtze Basin of South China. The δ15N profiles in both basins reveal consistent trends that correspond to fluctuations in temperature across the Smithian–Spathian transition. The Smithian hyperthermal interval exhibited low δ15N values (mostly <+2‰), indicating N deficiency and enhanced biological N 2 fixation. Bacterial blooms and the release of the potent greenhouse gas N 2 O, enhanced by high temperatures, may have triggered positive feedback mechanisms that sustained the warming and contributed to the late Smithian extinction. During subsequent cooling across the Smithian–Spathian transition, δ15N increased to a range of +3‰ to +7‰, likely reflecting signals of partial denitrification based on reconstruction of the NO 3 − inventory associated with oceanic cooling and oxygenation. The prevailing increases in sedimentary TOC/TN ratios signify heightened deamination (removal of amino groups) and N recycling across the Smithian–Spathian boundary. This transition is likely attributed to cooling-driven amelioration of seawater stratification and anoxia from the Smithian to the Spathian, which resulted in increased nitrate availability in the photic zone. Eukaryotic algae thrived while prokaryotes declined during the Spathian, evidenced by elevated δ15N and Δ13C carb-org (the difference between carbonate and organic carbon isotopes). The proliferation of eukaryotic algae had a positive impact on environmental conditions and facilitated biotic recovery due to more efficient burial of organic particles. A notable latitudinal gradient in the N cycle response was observed, with low-latitude regions showing a more pronounced response to cooling compared to mid-latitude areas. This significant gradient may suggest that the rapid recovery of nutrient cycles, despite relatively small decline in high temperature, was a key factor in the amelioration of climate and recovery of life in low latitudes. These findings highlight that the marine N cycle is highly sensitive to temperature changes, particularly in low-latitude regions, and that changes in N cycle under high-temperature conditions may be a critical life-limiting factor. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fixation by moss-cyanobacteria associations has been recognized as an important N input pathway in many ecosystems from arctic tundra to tropical forests. However, the transfer of fixed N2 from mosses to the soil as well as the effects of rainfall frequency and volume on this N transfer has hardly been studied – even though mosses can leach nutrients upon rewetting. In this study, we investigated the transfer of fixed N2 by moss-cyanobacteria associations in one month under four watering regimes with a combination of high and low volume and frequency. For this, we used two morphologically similar moss species collected from ecosystems with different climate and N availability (subarctic - Hylocomium splendens; and tropical - Thuidium delicatulum). Acetylene reduction assays were conducted as a measure of N2 fixation rates in mosses, and 15N-N2 tracing was used to follow the fixed N2 from moss to the underlying substrate. Nitrogen fixation rates were higher in T. delicatulum than in H. splendens, but rainfall volume and frequency did not show strong effects on N2 fixation rates. Nonetheless, the extent of N leached from mosses was more sensitive to an increase in rainfall volume than to an increase in frequency, and more N was lost from T. delicatulum under high volume precipitation than from H. splendens. Both total nitrogen and 15N enrichment results demonstrate that the fixed N2 was mostly stored in moss tissues with less than 1 % leached to the substrate. Our results show that both moss species retain almost all fixed N2 within their tissues under small rainfall disturbances within one month, while increased N availability under higher precipitation volume renders some moss species an important N source for the soil.

• High volume precipitation does not translate into increased moss-associated nitrogen (N) fixation rates. • N fixation increased more in a tropical moss compared to a subarctic moss under all rainfall regimes. • Less than 1 % of fixed N was leached from mosses within a 1-month period. • N leaching from mosses was more sensitive to watering volume than frequency. Nitrogen (N) fixation by moss-cyanobacteria associations has been recognized as an important N input pathway in many ecosystems from arctic tundra to tropical forests. However, the transfer of fixed N 2 from mosses to the soil as well as the effects of rainfall frequency and volume on this N transfer has hardly been studied – even though mosses can leach nutrients upon rewetting. In this study, we investigated the transfer of fixed N 2 by moss-cyanobacteria associations in one month under four watering regimes with a combination of high and low volume and frequency. For this, we used two morphologically similar moss species collected from ecosystems with different climate and N availability (subarctic - Hylocomium splendens ; and tropical - Thuidium delicatulum). Acetylene reduction assays were conducted as a measure of N 2 fixation rates in mosses, and 15N-N 2 tracing was used to follow the fixed N 2 from moss to the underlying substrate. Nitrogen fixation rates were higher in T. delicatulum than in H. splendens , but rainfall volume and frequency did not show strong effects on N 2 fixation rates. Nonetheless, the extent of N leached from mosses was more sensitive to an increase in rainfall volume than to an increase in frequency, and more N was lost from T. delicatulum under high volume precipitation than from H. splendens. Both total nitrogen and 15N enrichment results demonstrate that the fixed N 2 was mostly stored in moss tissues with less than 1 % leached to the substrate. Our results show that both moss species retain almost all fixed N 2 within their tissues under small rainfall disturbances within one month, while increased N availability under higher precipitation volume renders some moss species an important N source for the soil. [Display omitted] [ABSTRACT FROM AUTHOR]

Trichodesmium plays a key role in the biogeochemical cycling of carbon, nitrogen and phosphorus in the Tropical Atlantic Ocean. A complex interplay of physicochemical factors control the growth of Trichodesmium. However, owing to the large spatial and temporal variability, the relative influence of these factors in controlling Trichodesmium distribution and abundance remains unclear. In this study, we examined the basin‐scale distribution pattern of Trichodesmium in the upper 200 m water column of the Atlantic Ocean (25°N–30°S and 70°W–20°E) using a large data set (n = 33,235) and tried to constrain the distribution based on various physicochemical parameters. We suggest that the combined effect of warm temperatures and phosphate (PO43−) availability determines the zonal spatial extent and the abundance of Trichodesmium in the Tropical North Atlantic Ocean. However, the availability of dissolved iron, along with high sea surface temperatures and meteorological parameters such as the wind direction and precipitation, likely govern the meridional distribution of Trichodesmium across the Atlantic Ocean. Excess PO43− at the surface rules out the possibility of PO43− limitation in regulating the meridional distribution of the Trichodesmium. Depth‐integrated nitrogen fixation rates, based on a multiple linear regression, vary from 0.07 to 306 μmol N m−2 d−1. The presence of Trichodesmium colonies down to a depth of 200 m and the depth‐integrated nitrogen fixation rates reflect the pivotal role of Trichodesmium in the nitrogen budget of this region. Plain Language Summary: Microbial nitrogen fixation is the key to carbon sequestration in the ocean. Trichodesmium, being the ubiquitous nitrogen fixing microbe in the Tropical Atlantic Ocean, contributes significantly to nitrogen inputs. Limited availability of data, however, restricts our understanding of environmental parameters in controlling the distribution and abundance of Trichodesmium. To address this, we conducted a comprehensive analysis using large‐scale field‐based data of Trichodesmium abundance to investigate the role of various physical, chemical, and meteorological parameters on the distribution and abundance of Trichodesmium along the zonal and meridional transects of the Tropical Atlantic Ocean. We conclude that Trichodesmium distribution is governed by a complex interplay of environmental factors. Along the zonal transect, Trichodesmium abundance is primarily governed by the availability of PO43− and high sea surface temperatures. Conversely, the inter‐hemispheric variability seems to be influenced by dust deposition (a proxy for iron inputs) and high sea surface temperatures. Furthermore, our estimation of high modeled depth‐integrated nitrogen fixation rates based on Trichodesmium underscores its crucial role in the nitrogen budget. These findings provide valuable insight into the role of environmental factors driving Trichodesmium abundance and its significance toward the global nitrogen budget. Key Points: Trichodesmium distribution across the east‐west continuum in the Tropical North Atlantic Ocean is governed by the availability of phosphate and elevated sea surface temperaturesThe interhemispheric variability in Trichodesmium distribution in the Atlantic Ocean is regulated by the cumulative effect of high temperature and dust depositionTrichodesmium niche may have been overlooked in the past, potentially leading to underestimation of associated N2 fixation rates [ABSTRACT FROM AUTHOR]

This study conducted sensitive and precise analyses of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) concentrations and trace concentrations of nitrate and nitrite (N+N) and soluble reactive phosphorus (SRP) in seawater. The methods were applied to investigate the distributions and controls of N+N, SRP, DON, and DOP in the oligotrophic Kuroshio Current (KC) area off eastern Taiwan during warm seasons. The water in the studied area was classified into four major types: typical Kuroshio water (KW), KW influenced by the East China Sea water, KC influenced by the South China Sea (SCS) water, and KW influenced by the SCS water and river plumes, which is confined to the coastal zone. Nutrient distributions in KC revealed very low N+N (0.002-0.40 mM) and SRP (0.015-0.125 mM) concentrations but high DON (<8 mM) and DOP (<0.3 mM) concentrations above the nutricline depth, which accounted for >80% of TDN and TDP, respectively; theses concentrations can primarily be attributed to strong, permanent surface stratification. Among the water types, KW had the lowest N+N, SRP, DON, and DOP concentrations but greatest chlorophyll maximum depth and nutricline depth, except for in locations influenced by island-induced upwelling. The concentrations of all nutrients increased by various degrees in the other water types, which was attributed to the exchange and mixing of different water masses and coastal uplift of subsurface waters. KW was not only highly oligotrophic but also N+N-limited reflected from very low [N+N]/[SRP] ratio (0.02-0.15) in the mixed layer (ML). Overall, the N+N limitation and high nitrate anomaly value (N*: 2.47 ± 0.16 mM) above the nutricline depth strongly indicate prevailing N2 fixation at the surface of KW. Very high DON/DOP ratio in KW (16.9-69.1) probably resulted from the release of N-rich organic nutrients from phytoplankton including N2 fixers at the surface and faster recycling of DOP than DON in deep waters. Persistent coastal uplift of subsurface water occurs everywhere over the shore-side region of the KC, resulting in increasing surface concentrations of nutrients and chlorophyll a. Overall, the aforementioned physical and biogeochemical processes determined the upper-ocean distributions of nutrient species in warm seasons. [ABSTRACT FROM AUTHOR]

A conceptual framework is proposed for understanding the relationship between temperature and biological N 2 fixation (BNF) across levels of biological organization from enzymes to ecosystems on land and in the ocean. Global compilations of measured N 2 fixation rates reveal a temperature dependence that is broadly similar in marine and terrestrial systems, including a common thermal optimum at ~25°C, suggesting an overarching enzymatic constraint. Rate–temperature relationships also reveal features unique to marine and terrestrial domains, including greater heat tolerance of terrestrial BNF, suggesting the presence of, and adaptation to, distinct thermal and ecological niches. Climate warming is projected to reduce N 2 fixation in the tropics while increasing it in higher latitudes in terrestrial and marine ecosystems, a spatial shift that would impact productivity and N cycling, unless modulated by other environmental factors and physiological adaptations. Biological N 2 fixation sustains the global inventory of nitrogenous nutrients essential for the productivity of terrestrial and marine ecosystems. Like most metabolic processes, rates of biological N 2 fixation vary strongly with temperature, making it sensitive to climate change, but a global projection across land and ocean is lacking. Here we use compilations of field and laboratory measurements to reveal a relationship between N 2 fixation rates and temperature that is similar in both domains despite large taxonomic and environmental differences. Rates of N 2 fixation increase gradually to a thermal optimum around ~25°C, and decline more rapidly toward a thermal maximum, which is lower in the ocean than on land. In both realms, the observed temperature sensitivities imply that climate warming this century could decrease N 2 fixation rates by ~50% in the tropics while increasing rates by ~50% in higher latitudes. We propose a conceptual framework for understanding the physiological and ecological mechanisms that underpin and modulate the observed temperature dependence of global N 2 fixation rates, facilitating cross-fertilization of marine and terrestrial research to assess its response to climate change. [ABSTRACT FROM AUTHOR]

The effect of environmental factors on the proportion of the nitrogen (N) derived from the atmosphere (Ndfa) in soybean [Glycine max (L.) Merril] have been traditionally approached individually given their intrinsic complexity. Alternatively, a more in-depth investigation of such complex interactions can be pursued by delimiting environments where Ndfa is uniform. Thus, the aim of this study was to define environments on 24 sites by extensively characterizing weather, plant, and Ndfa-related traits to find discriminant variables defining three Ndfa classes (low, medium, and high). The Ndfa was determined at the beginning of the seed filling (R5 growth stage) using the 15N natural abundance method. Twenty environmental variables were utilized to categorize Ndfa in low (< 57%), medium (57–66%), and high (≥ 66%) classes via implementation of discriminant multivariate analysis. The Ndfa averaged 60%, lower to previous values reported for Brazil (ranging from 69 to 94%). Mean air temperature, associated to SOM and soil N, was the most important variable related to low Ndfa, while improving soil fertility (soil pH, base saturation, exchangeable Ca and Mg, and available P) was critical for high Ndfa and, consequently, seed yield. The high contribution of those factors highlight the importance of implementing strategies to improve soil fertility, to promote better plant growth, and thus enhancing Ndfa contribution to crop N uptake. [ABSTRACT FROM AUTHOR]

Aims: Nitrogen deficiency in eco-engineered technosol from iron (Fe) ore tailings limits the productivity of colonising soil microbes and pioneer plants, which are critical to further development of the technosol. Symbiotic biological N2 fixation may be a strategy to supply N in the moderately alkaline early technosols since native legumes such as Acacia auriculiformis are tolerant of saline and alkaline soil conditions as those in the technosol. It is hypothesized that tolerant native legume A. auriculiformis could form functional nodules to fix N2 when grown in early eco-engineered technosols. Methods: A. auriculiformis growth and root nodulation in the early tailing technosols were investigated using a glasshouse experiment, and plant N2 fixation was evaluated using the 15 N natural abundance isotope method. Key factors influencing root nodulation and N2 fixation have also been evaluated, including water supply and phosphorous nutrition. Results: The results indicated that A. auriculiformis grew well in the tailing technosols and naturally formed nodules with rhizobia. The nodules were functional in N2 fixation, leading to improved plant N nutrition. The nodulation and N2 fixation were severely limited by water deficiency stress. Improved phosphorous supply favoured nodulation and N2 fixation by A. auriculiformis plants under water deficiency stress. Conclusions: These findings suggested that A. auriculiformis could grow in early tailings technosols and fixed N2, and proper water and phosphorous fertilizer management could improve Acacia plant's performance and N2 fixation functions. It is possible to introduce tolerant native legumes such as A. auriculiformis to improve N supply in the early technosols. [ABSTRACT FROM AUTHOR]

Intercropping legumes with cereals can lead to increased overall yield and optimize the utilization of resources such as water and nutrients, thus enhancing agricultural efficiency. Legumes possess the unique ability to acquire nitrogen (N) through both N2 fixation and from the available N in the soil. However, soil N can diminish the N2 fixation capacity of legumes. It is postulated that in intercropping, legumes uptake N mainly through N2 fixation, leaving more soil N available for cereals. The latter, in turn, has larger root systems, allowing it to explore greater soil volume and absorb more N, mitigating its adverse effects on N2 fixation in legumes. The goal of this study was to evaluate how the supply of N affects the intercropping of faba beans (Vicia faba L.) and peas (Pisum sativum L.) with wheat under varying plant densities and N levels. We measured photosynthetic traits, biomass production, the proportion of N derived from air (%Ndfa) in the shoot of the legumes, the N transferred to the wheat, and the land equivalent ratio (LER). The results revealed a positive correlation between soil N levels and the CO2 assimilation rate (An), chlorophyll content, and N balance index (NBI) in wheat. However, no significant effect was observed in legumes as soil N levels increased. Transpiration (E) increased in wheat intercropped with legumes, while stomatal conductance (gs) increased with N addition in all crops. Water use efficiency (WUE) decreased in faba beans intercropped with wheat as N increased, but it showed no significant change in wheat or peas. The shoot dry matter of wheat increased with the addition of N; however, the two legume species showed no significant changes. N addition reduced the %Ndfa of both legume species, especially in monoculture, with peas being more sensitive than faba beans. The intercropping of wheat alleviated N2 fixation inhibition, especially at high wheat density and increased N transfer to wheat, particularly with peas. The LER was higher in the intercropping treatments, especially under limited N conditions. It is concluded that in the intercropping of wheat with legumes, the N2 fixation inhibition caused by soil N is effectively reduced, as well as there being a significant N transfer from the legume to the wheat, with both process contributing to increase LER. [ABSTRACT FROM AUTHOR]

Limited information is available in Mexico regarding the use of Lupinus angustifolius L. as a green manure. This study aimed to assess the effectiveness of six Lupinus angustifolius varieties as green manure in terms of above-ground biomass production, expressed as dry matter (DM), and total nitrogen (N) accumulation at successive harvest dates. Additionally, the study aimed to estimate N2 fixation 110 days after sowing (DAS). The varieties Haags Blaue, Boregine, Borlu, Probor, Sonate, and Boruta were sown during the winter season of 2018-2019 using a randomized block factorial design. The N difference method was employed to estimate N2 fixation, with wheat serving as the reference crop. Data on above-ground biomass production, N concentration, and total N accumulation were recorded at different harvest times: 80, 95, and 110 DAS. The biomass yield of all varieties significantly increased from the first to the last harvest, with the highest yield observed at the final harvest (ranging from 7,632 to 10,200 kg ha-1). The highest total N accumulation from biomass was recorded at the last harvest. On average, the Borlu, Boregine, Haags Blaue, and Boruta varieties accumulated 195.4 kg ha-1 of total N (ranging from 195.6 to 221.2 kg ha-1). The proportion of N derived from the atmosphere (%Ndfa) through N2 fixation averaged 80.09% (ranging from 72% to 93%), resulting in an average N fixation of 160 kg ha-1 (ranging from 106 to 185 kg ha-1) in above-ground biomass. All six varieties demonstrated potential as green manure, considering their above-ground biomass production, total N accumulation, and ability to fix N2.

The simultaneous degradation of organic pollutants and generation of value-added compounds like ammonia and hydrogen energy has recently gained considerable attention in photocatalysis. The present study deals with successful preparation of novel AgVO 3 nanowire@rGO-tetrahedral Ag 3 PO 4 (110) (AGA) heterojunction and utilized for enhanced generation of NH 3 and H 2 from N-containing antibiotic sulfamethoxazole (SMX) under visible light. The prepared catalyst was well characterized by XRD, SEM, TEM and XPS to confirm the formation of heterojunction. The results indicated that the composite exhibited 546.0 μmol g−1 of hydrogen evolution rate, which is approximately 3.6 (153.6 μmol g−1) and 5.1 (108.7 μmol g−1) times higher than the pure AgVO 3 and Ag 3 PO 4 respectively after 6 h. Similarly, 38.3 mg L−1g−1 of NH 3 generation was observed during 6 h of SMX degradation, which is about 1.9 and 2.8 times higher than the pure AgVO 3 (20.1 mg L−1g−1) and Ag 3 PO 4 (13.7 mg L−1g−1) respectively. The formation of heterojunction between AgVO 3 and Ag 3 PO 4 not only promotes the transfer of electron but also prevents the recombination which eventually enhances the catalytic conversion of N-element to NH 3 and for H 2 generation during water splitting. Furthermore, the plausible degradation pathway in SMX was proposed and the results revealed that the SMX was mineralized by the composite further converted to NH 3 and generates H 2 during the degradation process. Thus, our study provides new insights into novel photocatalytic treatment methodologies for simultaneous degradation of SMX to produce NH 3 and H 2 as value-added compounds from antibiotic wastewaters during water treatment process. • A facile dual functional hybrid composite was prepared. • H 2 and NH 3 has been generated during photocatalytic degradation of SMX. • Heterojunction significantly enhanced SMX degradation and H 2 generation. • N-containing SMX molecule was utilized as a nitrogen source for ammonia. [ABSTRACT FROM AUTHOR]

Aiming to improve the photocatalytic activity in N2 fixation to produce ammonia, herein, we proposed a photochemical strategy to fabricate defects, and further deposition of Ru single atoms onto UiO‐66 (Zr) framework. Electron‐metal‐support interactions (EMSI) were built between Ru single atoms and the support via a covalently bonding. EMSI were capable of accelerating charge transfer between Ru SAs and UiO‐66, which was favorable for highly‐efficiently photocatalytic activity. The photocatalytic production rate of ammonia improved from 4.57 μmol g−1 h−1 to 16.28 μmol g−1 h−1 with the fabrication of defects onto UiO‐66, and further to 53.28 μmol g−1 h−1 with Ru‐single atoms loading. From the DFT results, it was found that d‐orbital electrons of Ru were donated to N2 π✶‐antibonding orbital, facilitating the activation of the N≡N triple bond. A distal reaction pathway was probably occurred for the photocatalytic N2 reduction to ammonia on Ru1/d‐UiO‐66 (single Ru sites decorated onto the nodes of defective UiO‐66), and the first step of hydrogenation of N2 was the reaction determination step. This work shed a light on improving the photocatalytic activity via feasibly anchoring single atoms on MOF, and provided more evidences to understand the reaction mechanism in photocatalytic reduction of N2. [ABSTRACT FROM AUTHOR]

Experiments conducted under controlled conditions can be poor predictors of the field performance of rhizobial inoculants. In this study, five field experiments were conducted over 2 years to evaluate the symbiotic performance of 12 previously identified strains isolated from Australia and Myanmar soils that had potential to improve chickpea productivity through symbiotic N2 fixation. Strains collected from Australian soils had more than double the survival on seed and up to three times the nodulation at some experimental sites, compared with strains isolated from Myanmar soils. Generally, the newly isolated strains did not perform better than the current Australian commercial strain, Mesorhizobium ciceri CC1192. Although Myanmar strains had poor nodulation of chickpea plants (below nodule rating 1 in most cases) under Australian field conditions, the plant traits related to growth and symbiosis, such as shoot dry weight (SDW), yield and N fixation, were improved and sometimes equal to the plants inoculated with the Australian strains. Partial correlations showed that plants inoculated with Myanmar strains had greater associations with N fixation measurements (7 plant traits) than nodule number (1 trait), while a symbiotic effectiveness measure of the ratio between N fixation and nodule mass indicated that Myanmar strains are more than 75% more symbiotically efficient compared with the Australian strains. Better seed and soil survival of the Myanmar strains may increase plant nodulation and may lead to a highly effective inoculant strain. This study is one of the first to report increased symbiotic efficiency of N fixation of novel strains compared to a widely utilised commercial chickpea-nodulating strain, on a per nodule basis. [ABSTRACT FROM AUTHOR]

In order to achieve efficient photocatalytic N2 reduction activity for ammonia synthesis, a photochemical strategy was used in this work. UiO-66 was prepared through the solvothermal method and further loaded with Au nanoparticles (Au NPs) onto the UiO-66 (Zr) framework. The experimental results verified that there were metal–support interactions between Au NPs and UiO-66; this could facilitate charge transfer among Au NPs and UiO-66, which was beneficial to enhance the photocatalytic activity. The best N2 fixation effect of Au/UiO-66 with a loading of 1.5 wt% was tested, with a photocatalytic yield of ammonia of 66.28 μmol g−1 h−1 while maintaining good stability. The present work provides a novel approach to enhancing photocatalytic N2 fixation activity by loading NPs onto UiO-66. [ABSTRACT FROM AUTHOR]

The detrimental impact of human activity on the global ecological situation has resulted in the active exploration and development of alternative energy sources. Efficient solar energy utilization can significantly contribute to resolving the current energy crisis, because approximately 1.36 kW m−2 of solar radiation reaches the Earth's surface, and this can be used to satisfy the global energy requirements. Among various prevalent sunlight conversion technologies, photocatalytic materials are potentially useful for hydrogen production and other relevant applications. Existing technologies for the production and use of photocatalysts do not sufficiently address the target characteristics owing to the low solar conversion efficiency and service life in addition to high costs. However, recent advances in SrTiO 3 -based heterostructures indicate that photocatalysts can potentially compete with modern solar energy technologies in terms of their practical application. In this review, we systematically consider the advancement in the production and application of SrTiO 3 -based photocatalysts in various fields. The methods for obtaining complex heterostructures with different classes of nanomaterials are comprehensively discussed. The aim of this review is to highlight the advantages and limitations of using SrTiO 3 -based photocatalytic systems. Finally, the future prospects of using SrTiO 3 -based photocatalysts are considered from the perspective of their practical applications. [Display omitted] • The main strategies to overcome the limitations of SrTiO 3 based photocatalysts in various applications are presented. • The synthesis methods of composites based on SrTiO 3 for photocatalytic applications were discussed. • The potential applications of SrTiO 3 -based composites in solving environmental and energy-related problems are explored. [ABSTRACT FROM AUTHOR]

Great Lakes coastlines are mosaics of wetland, stream, and lake habitats, characterized by a high degree of spatial heterogeneity that may facilitate the co-occurrence of seemingly incompatible biogeochemical processes due to variation in environmental factors that favor each process. We measured nutrient limitation and rates of N2 fixation and denitrification along transects in 5 wetland–stream–lake ecotones with different nutrient loading in Lakes Superior and Huron. We hypothesized that rates of both processes would be related to nutrient limitation status, habitat type, and environmental characteristics including temperature, nutrient concentrations, and organic matter quality. We found that median denitrification rates (914 μg N m−2 h−1) were 166 × higher than N2 fixation rates (5.5 μg N m−2 h−1), but the processes co-occurred in 48% of 83 points measured across all 5 transects and habitat types. N2 fixation occurred on sediment and macrophyte substrate, while denitrification occurred mostly in sediment. Nutrient-diffusing substrate experiments indicated that biofilm chlorophyll-a was limited by N and/or P at 55% and biofilm AFDM was limited at 26% of sample points. N2 fixation and denitrification rates did not differ significantly with differing nutrient limitation. Predictive models for N2 fixation and denitrification rates both included variables related to the composition of dissolved organic matter, while the model for N2 fixation also included P concentrations. These results demonstrate the potential for heterogeneity in habitat characteristics, nutrient availability, and organic matter composition to lead to biogeochemical complexity at the local scale, despite overall N removal at broader scales. [ABSTRACT FROM AUTHOR]

The development of a long-term and sustainable energy economy is one of the most significant technological challenges facing humanity. Photoelectrochemical (PEC) technology is considered as the most attractive route for converting solar energy into chemical energy. However, the slow reaction kinetics of PEC oxidation and reduction greatly hinder its practical application. To address this issue, engineering photoelectrodes with various defects can significantly improve their catalytic performance, which can not only regulate catalyst electronic structure but also promote charge transfer/separation by serving as an active/adsorption/energy storage site. Herein, the defect engineering strategies for photoelectrodes are systematically summarized, focusing on the latest progress in defective photocathode for energy conversion. First, an overview of defect types, basic principles of photocathode, and the positive role of defects in the photocathode are provided. Second, the construction strategies and characterization methods of defective photocathode are summarized. Then, the progress of typical energy conversion applications, including hydrogen production, CO2 reduction, and nitrogen reduction over defective photocathode, is reviewed, highlighting the crucial role of defects in high catalytic performance. Finally, the challenges and future prospects of defective photocathode are discussed, aiming to bring new opportunities for the development of photocathode through defect engineering. [ABSTRACT FROM AUTHOR]

Non-cyanobacterial diazotrophs (NCDs) are widespread and active in marine waters. The carbon and low-oxygen (O2) conditions required for their N2 fixation may be encountered on marine particles, while a putative role of light remains uninvestigated. This study explored factors that regulate N2 fixation in Rhodopseudomonas sp. BAL398--a anoxygenic phototrophic bacterium isolated from low-salinity surface waters. Light (250 µmol photons m-2 s-1) and anoxia (0 µM O2) stimulated growth and N2 fixation; however, diazotrophy in light was dependent on high organic carbon levels (35 mM, glucose:succinate). Immunolabeling revealed that cellular nitrogenase levels increased with light, decreasing inorganic nitrogen (N) and ambient O2 (250 µM). Light and O2 stimulated motility and biofilm formation on surfaces, and N2 fixation rates increased compared to the control treatment. N2 fixation rates were positively correlated with the formation of rosette-like cellular structures, and an increased concentration of nitrogenase was observed toward the center of these structures, which increased their occurrence 600 times when cultures reached maximum N2 fixation rates vs when they had low rates. Interestingly, N2 fixation was not completely inhibited under oxic conditions and was accompanied by increased formation of capsules and cysts. Rosettes, as well as capsules and cysts, may thus serve as protection against O2. Our study reveals the physiological adaptations that underlie N2 fixation in an anoxygenic phototroph, emphasizing the significance of biofilm formation for utilizing light and fixing N2 under oxic conditions, and underscores the need for deciphering the importance of light for marine NCDs. IMPORTANCE The contribution of non-cyanobacterial diazotrophs (NCDs) to total N2 fixation in the marine water column is unknown, but their importance is likely constrained by the limited availability of dissolved organic matter and low O2 conditions. Light could support N2 fixation and growth by NCDs, yet no examples from bacterioplankton exist. In this study, we show that the phototrophic NCD, Rhodopseudomonas sp. BAL398, which is a member of the diazotrophic community in the surface waters of the Baltic Sea, can utilize light. Our study highlights the significance of biofilm formation for utilizing light and fixing N2 under oxic conditions and the role of cell plasticity in regulating these processes. Our findings have implications for the general understanding of the ecology and importance of NCDs in marine waters. [ABSTRACT FROM AUTHOR]

Intercropping may improve the use of environmental resources in low-input agricultural systems compared to sole crops and it is possible that risk may be reduced in intercropping, leading to more stable yields and weed control. The aim of the present study was to determine the effect of seeding rate of a normal leafed cultivar and a semileafless pea cultivar (Pisum sativum L.) grown as sole crops, cultivar mixture, and in double and triple intercrops with spring wheat (Triticum aestivum L.) on competitive dynamics, yield and use of nitrogen sources from soil, and symbiotic N2 fixation. A randomized complete blocks experiment design was used. The differences between the treatments were not significant for total grain yield. Land equivalent ratios for grain yield varied between 1.04 (80P/20W) and 1.40 (80D/20W), which showed that plant growth factors are used more efficiently by the intercrops than by the sole crops for grain production. Nitrogen accumulation was higher in pea sole crops compared to pea component crops in the intercrops, due to the decreased pea density and decreased pea growth caused by interspecific competition from wheat. The amount of N2 fixed in pea in the intercrops at the flowering harvest was less than the in the pea sole crop also due to competition from wheat for other growth factors than nitrogen, probably by shading. It was concluded that pea-wheat intercropping can use N resources more efficiently compared to sole crops in sustainable cropping systems. [ABSTRACT FROM AUTHOR]

Heterocytous cyanobacteria are important players in the carbon and nitrogen cycle. They can fix dinitrogen by using heterocytes, specialized cells containing the oxygen-sensitive nitrogenase enzyme surrounded by a thick polysaccharide and glycolipid layer which prevents oxygen diffusion and nitrogenase inactivation. Heterocyte glycolipids can be used to detect the presence of heterocytous cyanobacteria in present-day and past environments, providing insight into the functioning of the studied ecosystems. However, due to their good preservation throughout time, heterocyte glycolipids are not ideal to detect and study living communities, instead methods based on DNA are preferred. Currently cyanobacteria can be detected using untargeted genomic approaches such as metagenomics, or they can be specifically targeted by, for example, the use of primers that preferentially amplify their 16S rRNA gene or their nifH gene in the case of nitrogen fixing cyanobacteria. However, since not all cyanobacterial nitrogen fixers are heterocytous, there is currently no fast gene-based method to specifically detect and distinguish heterocytous cyanobacteria. Here, we developed a PCR-based method to specifically detect heterocytous cyanobacteria by designing primers targeting the gene (hglT) encoding the enzyme responsible for the last step in the biosynthesis of heterocyte glycolipid (i.e., a glycosyltransferase). We designed several primer sets using the publicly available sequences of 23 heterocytous cyanobacteria, after testing them on DNA extracts of 21 heterocyte-forming and 7 non-heterocyte forming freshwater cyanobacteria. The best primer set was chosen and successfully used to confirm the presence of heterocytous cyanobacteria in a marine environmental sample. [ABSTRACT FROM AUTHOR]

Intercropping of cotton and legume plants offers long‐term crop productivity while saving agricultural resources and improving soil health. However, the use of nitrogen (N) in cotton/legume intercropping systems requires further evaluation. In this study, three N fertilization rates (cotton/soybean: 160/20, 320/40 and 480/80 kg N ha−1) incorporating three root barrier systems (complete, semi and no root barrier between the crops) under cotton/soybean intercropping systems were conducted to assess interactions between N supply and N transfer, recovery and residue using the 15N isotope dilution method. The results show that cotton was a stronger competitor for N than soybean plants. The 320/40 kg N ha−1 treatment with no root barrier system inhibited the growth of soybean, while the growth, productivity and N uptake for cotton were maximized. The N fixation rate (%NDFA) in soybean and N transfer rate (%NTFS) from soybean to cotton decreased with the increasing N fertilizer application rate, whereas the intercropping system with no root barrier increased %NDFA and %NTFS. The higher N fertilization rate increased the N residue on the side of cotton, whereas the intercropping with no root barrier increased N utilization rate (%NUR) and reduced N residue rate (%NRR). The N transfer amount (NTA) was positively correlated with cotton yield, dry matter (DM) and N uptake, while NTA was negatively correlated with these indicators for soybean. Overall, cotton/soybean intercropping adapted to the 320/40 kg N ha−1 condition and intercropping with no root barrier system by balancing growth, changing N uptake and regulating N fixation transfer, mitigating the issue of N residue. [ABSTRACT FROM AUTHOR]

Limited information is available in Mexico regarding the use of Lupinus angustifolius L. as a green manure. This study aimed to assess the effectiveness of six Lupinus angustifolius varieties as green manure in terms of above-ground biomass production, expressed as dry matter (DM), and total nitrogen (N) accumulation at successive harvest dates. Additionally, the study aimed to estimate N2 fixation 110 days after sowing (DAS). The varieties Haags Blaue, Boregine, Borlu, Probor, Sonate, and Boruta were sown during the winter season of 2018-2019 using a randomized block factorial design. The N difference method was employed to estimate N2 fixation, with wheat serving as the reference crop. Data on above-ground biomass production, N concentration, and total N accumulation were recorded at different harvest times: 80, 95, and 110 DAS. The biomass yield of all varieties significantly increased from the first to the last harvest, with the highest yield observed at the final harvest (ranging from 7,632 to 10,200 kg ha-1). The highest total N accumulation from biomass was recorded at the last harvest. On average, the Borlu, Boregine, Haags Blaue, and Boruta varieties accumulated 195.4 kg ha-1 of total N (ranging from 195.6 to 221.2 kg ha-1). The proportion of N derived from the atmosphere (%Ndfa) through N2 fixation averaged 80.09% (ranging from 72% to 93%), resulting in an average N fixation of 160 kg ha-1 (ranging from 106 to 185 kg ha-1) in above-ground biomass. All six varieties demonstrated potential as green manure, considering their above-ground biomass production, total N accumulation, and ability to fix N2. [ABSTRACT FROM AUTHOR]

Erratic climatic conditions, inherent low fertility and nutrient depletion are among the most important biophysical constraints of food crops production in semi-arid African regions. This study aimed to elucidate the impact of different crop spatial arrangements associated with different levels of Phosphorus on the performance of maize-bean intercropping in Tanzania. The experiment was laid in a complete randomized design of factorial-split arrangement and three factors in different levels. Sowing patterns were randomly assigned to all experimental plots whereas Phosphorus rates were randomly assigned within a specific sowing pattern one after another. Data were subjected to statistical analysis using GenStat software of a generalized treatment structure in a randomized design. Results of the interaction between cropping pattern and the P-rates on beans and maize at a 5% level of significance indicated that grain yield, pods/plant, and biological yield did not differ significantly (P>0.05) while plant height, leaf area index, and plants per plot differed significantly (P

In this work, Ag/Bi5O7I nanocomposite was prepared and firstly applied in piezo/photocatalytic reduction of N2 to NH3 and methyl orange (MO) degradation. Bi5O7I was synthesized via a hydrothermal-calcination method and shows nanorods morphology. Ag nanoparticles (NPs) were photo deposited on the Bi5O7I nanorods as electron trappers to improve the spatial separation of charge carriers, which was confirmed via XPS, TEM, and electronic chemical analyses. The catalytic test indicates that Bi5O7I presents the piezoelectric-like behavior, while the loading of Ag NPs can strengthen the character. Under ultrasonic vibration, the optimal Ag/Bi5O7I presents high efficiency in MO degradation. The degradation rate is determined to be 0.033 min−1, which is 4.7 folds faster than that of Bi5O7I. The Ag/Bi5O7I also presents a high performance in piezocatalytic N2 fixation. The piezocatalytic NH3 generation rate reaches 65.4 μmol L−1 g−1 h−1 with water as a hole scavenger. The addition of methanol can hasten the piezoelectric catalytic reaction. Interestingly, when ultrasonic vibration and light irradiation simultaneously act on the Ag/Bi5O7I catalyst, higher performance in NH3 generation and MO degradation is observed. However, due to the weak adhesion of Ag NPs, some Ag NPs would fall off from the Bi5O7I surface under long-term ultrasonic vibration, which would greatly reduce the piezoelectric catalytic performance. This result indicates that a strong binding force is required when preparing the piezoelectric composite catalyst. The current work provides new insights for the development of highly efficient catalysts that can use multiple energies.

[Display omitted] Electrocatalytic nitrogen reduction reaction (NRR) for artificial ammonia synthesis under mild conditions has been considered as a promising alternative to the conventional Haber–Bosch method. The highly desired efficient NRR still faced with the mulriple challenges of adsorption and activation of N 2 and limited Faraday efficiency. Here, Fe-doped Bi 2 MoO 6 nanosheets fabricated by one step synthesis exhibits high NH 3 yield rate of 71.01 μg·h−1·mg−1 and Faraday Efficiency of 80.12%. The decreased electron density of Bi in collaboration with Lewis acid active sites on Fe-doped Bi 2 MoO 6 , jointly enhance the adsorption and activation of Lewis basic N 2. Benefited from surface texture optimization and the superior ability of N 2 adsorption and activation, the increasing density of effective active sites greatly improve the NRR behavior. This work provides new opportunities for developing efficient and highly selective catalysts for NH 3 synthesis via NRR. [ABSTRACT FROM AUTHOR]

Biological dinitrogen (N2) fixation is meagerly explored in the Bay of Bengal (Bay). Stratified, warm, oligotrophic (but relatively high iron and phosphate) and oxygen minimum zone (OMZ) waters of the Bay might be a niche for diazotrophs. Therefore, we conducted N2 fixation rate measurements during the spring inter‐monsoon in the euphotic zone, the OMZ and below the OMZ down to 1,500 m depth near the coastal and in the central Bay. We further assessed primary production and cyanobacterial community composition along with their potential environmental controlling parameters. N2 fixation rates in the euphotic zone were low (0.02–0.38 nmol N L−1 d−1) and their contribution to primary production was small (<2%). Despite conducive conditions for diazotrophy in the Bay, the reason for the relatively low euphotic zone and OMZ N2 fixation rates remained unclear and enigmatic. Interestingly, significantly higher N2 fixation rates occurred below the OMZ (>600 m depth), ranging from 0.06 to 0.11 nmol N L−1 d−1 where oxygen concentrations ranged between 0.5 and 1.6 mL L−1, rather than within the OMZ where rates ranged from 0.02 to 0.08 nmol N L−1 d−1 and oxygen concentrations were ≤0.5 mL L−1. Euphotic zone N2 fixation showed seasonality in the Bay with increasing rates from spring to summer season, perhaps owing to increasing Fe flux as the summer monsoon approaches its peak. Plain Language Summary: The growth of marine phytoplankton is primarily limited by the reactive forms of nitrogen. Dinitrogen‐fixing organisms (termed "diazotrophs") supplement this need by providing a natural fertilizer—ammonium. Diazotrophs prefer phosphate and iron‐rich, but reactive nitrogen‐deficit waters. Therefore, the oligotrophic Bay of Bengal (the northeastern Indian Ocean) with excess phosphate relative to reactive nitrogen and high iron input could be a potential niche for diazotrophy. However, our results indicate that N2 fixation rates were low and supported less than 2% of organic matter formation in the Bay of Bengal during the spring inter‐monsoon. Surprisingly, N2 fixation rates were higher below the oxygen minimum zone than within it. Thus, our study provides additional evidence that N2 fixation is feasible (low but persistent) in dark marine places with abundant oxygen in conjunction with surface ocean. Key Points: Despite most prerequisites available for diazotrophic activity, N2 fixation rates are low in the Bay of BengalThe seasonality in N2 fixation in the Bay of Bengal is attributed to the Fe flux through dust depositionHigher N2 fixation rates occurred below rather than within the oxygen minimum zone [ABSTRACT FROM AUTHOR]

The development of solar-driven transfer of atmospheric nitrogen into ammonia is one of the green and sustainable strategies in industrial ammonia production. Nickel-titanium-layered double hydroxide (NiTi-LDH) was synthesised using the soft-chemical process for atmospheric nitrogen fixation application under photocatalysis in an aqueous system. NiTi-LDH was investigated using advanced characterisation techniques and confirmed the potential oxygen vacancies and/or surface defects owing to better photocatalytic activity under the solar spectrum. It also exhibited a bandgap of 2.8 eV that revealed its promising visible-light catalytic activities. A maximum of 33.52 µmol L−1 aqueous NH3 was obtained by continuous nitrogen (99.9% purity) supply into the photoreactor under an LED light source. Atmospheric nitrogen supply (≈78%) yielded 14.67 µmol L−1 aqueous NH3 within 60 min but gradually reduced to 3.6 µmol L−1 at 330 min. Interestingly, in weak acidic pH, 20.90 µmol L−1 NH3 was produced compared to 11.51 µmol L−1 NH3 in basic pH. The application of NiTi-LDH for visible-light harvesting capability and photoreduction of atmospheric N2 into NH3 thereby opens a new horizon of eco-friendly NH3 production using natural sunlight as alternative driving energy. [ABSTRACT FROM AUTHOR]

The spatial distribution of marine di-nitrogen (N2) fixation informs our understanding of the sensitivities of this process as well as the potential for this new nitrogen (N) source to drive export production, influencing the global carbon (C) cycle and climate. Using geochemically-derived δ15N budgets, we quantified rates of N2 fixation and its importance for supporting export production at stations sampled near the southwest Pacific Tonga-Kermadec Arc. Recent observations indicate that shallow (