Natural Abundance Research Articles

A dataset for 15N natural abundance of soil ammonia volatilization

Investigating the sources of ammonia (NH3) in the atmosphere and the contribution of each source is essential for environmental pollution control. The presented dataset aims to provide 15N natural abundance (δ15N) data collected from different controlled treatments to fill the knowledge gap between insufficient data of soil δ15N-NH3 and accurately identifying atmospheric NH3 source apportionments. Our results showed that the overall δ15N-NH3 values emitted from soil ranged from −46.09 to 10.22‰, with an average of −26.81 ± 11.17‰. The mean δ15N-NH3 values under different nitrogen (N) application rates, N fertilizer types, air temperatures, soil moisture, soil pH, soil types, and land use types were −29.41 ± 10.91, −32.43 ± 6.86, −29.10 ± 10.04, −30.31 ± 6.18, −24.84 ± 13.76, −23.53 ± 7.66, and −14.57 ± 12.54‰, respectively. Significant correlations were observed between δ15N-NH3 values and soil pH, soil NO3−-N concentration, and NH3 volatilization. This unique database provides basic data and evidence for the qualification of atmospheric NH3 source apportionments under different study area conditions.

Nitrite Cycling in Freshwater Ecosystems: A Case Study of an Artificial Reservoir in Eastern China Using Nitrite Dual Isotopes Combined with a Geochemical Model

Reservoirs are hotspots for emissions of the greenhouse gas nitrous oxide; however, the nitrite cycling processes associated with nitrous oxide production therein remain poorly understood, limiting a better assessment of the potential for reservoirs to emit nitrous oxide. Accordingly, this study presents the application of the natural abundance isotope technique combined with a geochemical model to elucidate the nitrite cycling in the freshwater aquaculture and non-aquaculture zones of a large artificial reservoir in eastern China. We employed nitrite dual isotopes to identify nitrite transformation processes. Additionally, a steady-state model was used to estimate the rates of these processes as well as the residence time of nitrite. Our findings indicate that nitrite production in this reservoir may be primarily driven by ammonia oxidation. However, the pathways of nitrite removal differ notably between the aquaculture and non-aquaculture zones, suggesting a significant impact of the aquaculture activities. The steady-state model calculations revealed that nitrification may be more pronounced in the aquaculture zones compared to the non-aquaculture zones, which may be related to the altered balance of competition for substrates between phytoplankton and microbes induced by aquaculture activities. Moreover, we observed a latitude-dependent increase in the significance of nitrite oxidation in natural environments, highlighting potential implications for regional and global nitrogen cycling. Our study highlights the complexity of the nitrite cycle and emphasizes the roles of both natural and anthropogenic factors in shaping nitrogen dynamics within freshwater reservoirs. This understanding contributes to a more accurate assessment of the greenhouse gas emission potential of reservoirs, offering valuable implications for the adoption of sustainable aquaculture practices to mitigate climate impacts and support global sustainable development goals.

A Review on Biomass-Derived Carbon Quantum Dots: Emerging Catalysts for Hydrogenation Catalysis.

The circular economy and the depletion of Earth's resources highlight the need to transform waste into value-added emerging materials like carbon quantum dots (CQDs), which show great promise in energy storage, catalysis, and other applications. The production of catalytically active CQDs from biomass garners significant attention due to their unique advantages, such as ease of availability, natural abundance, renewability, low cost, and environmental friendliness. This review addresses the synthesis of CQDs from biomass, the factors influencing their properties and performance, and their diverse applications in catalytic hydrogenation reactions, selective reduction of nitroaromatic compounds, and azo dyes. Recent studies demonstrate that biomass-derived CQDs exhibit significantly improved catalytic activity, selectivity, and stability, effectively addressing the long-standing challenges of low activity and poor stability in catalysts derived from conventional sources.

Utilisation of nanocellulose from cassava peels in polymer electrolyte membrane fabrication

AbstractIn recent decades, lithium‐ion batteries have become the leading energy storage solution due to their rechargeability, long lifespan, high energy density and lightweight design, although the conventional liquid electrolytes used raise performance and safety concerns, particularly regarding volatility and flammability at high temperatures. This study explores the incorporation of nanocellulose (NC) derived from cassava peels into polymer electrolyte membranes based on poly(ethylene oxide) (PEO). NC serves as a reinforcing agent, enhancing the mechanical properties of the membranes, such as tensile strength, while its natural abundance and biocompatibility offer a sustainable alternative for electrolyte materials. The membranes were prepared via the solution casting method utilising water as the solvent and subsequently characterised using Fourier transform infrared spectroscopy, XRD, a tensile tester, SEM and TGA/differential thermal analysis/DSC. Incorporating NC into the PEO matrix resulted in enhanced tensile strength and reduced strain at break, while negligibly impacting the ionic conductivity of the membrane. The most effective membrane composition was achieved at a PEO to NC ratio of 80:20, with the optimum ionic conductivity of the polymer electrolyte being 1.54 × 10−4 S cm−1, a tensile strength of 34.87 MPa and an elongation at break of 65.6%. This research sheds light on the potential of utilising NC from cassava peels to improve the performance and safety of polymer electrolyte membranes for lithium‐ion batteries. © 2024 Society of Chemical Industry.

Soil organic carbon and 13C changes when annual crops are replaced with perennial biomass crops in southwestern Ontario, Canada

Switchgrass (Panicum virgatum) and miscanthus (Miscanthus spp.) are C4 perennial biomass crops (PBCs) commonly cultivated in Ontario. The 13C natural abundance technique was used to assess the following: i) quantify the proportion of C4-derived soil organic carbon (SOC) stock (Mg C ha-1) within the SOC stocks of the whole soil, ii) determine the C4-derived SOC sequestration rate and iii) quantify C4-derived SOC stocks in soil particle size fractions. This was achieved by analyzing the δ13C values in SOC of both the whole soil and various soil particle size fractions in PBC fields that were converted from agriculture. At Guelph after 11 years of PBC, C4-derived SOC stock as a proportion of SOC stock in the whole soil accounted for 30% in switchgrass and 31% in miscanthus fields, while at Elora it comprised 41% in switchgrass and 50% in miscanthus. However, in Burlington after 4 years, C4-derived SOC represented 10-12% in PBC fields compared to 17% in agriculture fields. The C4 derived SOC sequestration rates were 0.8, 0.7 and 0.4 Mg C ha-1 y-1 in switchgrass, miscanthus and agriculture fields, respectively at the Guelph site. In miscanthus fields, lower C4-derived SOC stock in macro soil particles were observed, yet higher percentages were observed in micro soil particles and the silt plus clay fractions compared to switchgrass and agriculture fields. Agriculture fields had higher C4-derived SOC in macro soil particles, indicating lower SOC stability. Therefore, cultivating PBCs on low-productive agricultural lands could contribute to climate change mitigation practices due to increased SOC stability.

A Review of Synthesis and Therapeutic Applications of Coumarin Derivatives

Coumarins (2H-1-benzopyran-2-ones) are heterocyclic compounds widely distributed in plants, fruits, and vegetables, exhibiting significant pharmacological properties. The coumarin scaffold acts as a good template for drug development due to its structural simplicity and broad spectrum of biological activities. Modern synthetic approaches including gold-catalyzed cyclization, rhodium-catalyzed annulation, palladium-mediated coupling, and green chemistry methods have enabled efficient production of structurally diverse coumarin derivatives. The biological significance of coumarins encompasses anti-inflammatory, anticoagulant, antimicrobial, antiviral, and anticancer properties. Natural coumarins such as imperatorin and osthole show therapeutic effects against inflammation, microbial infections, and cancer. Structure-activity relationship studies have led to the development of synthetic derivatives with enhanced pharmacological profiles. The coumarin nucleus allows strategic modifications at multiple positions, resulting in compounds with improved efficacy and reduced toxicity. Recent synthetic methodologies emphasize sustainable protocols and efficient routes to complex coumarin derivatives. Emerging applications include the development of antidiabetic, neuroprotective, and antituberculosis agents. The low toxicity, natural abundance, and synthetic accessibility of coumarins position them as potential entities for drug discovery and development.

High-field SABRE pulse sequence design for chemically non-equivalent spin systems.

Signal amplification by reversible exchange (SABRE) employs the non-equilibrium spin order of parahydrogen as a source of strong nuclear magnetic resonance (NMR) signal enhancement, with the objective of increasing NMR sensitivity. In SABRE, a parahydrogen molecule and a substrate form a transient polarization transfer complex. Performed within the high magnetic field of an NMR spectrometer, SABRE enables the hyperpolarization of nuclear spins without additional polarizers. Nevertheless, it requires thorough pulse sequence design. The high-field polarization transfer strategy strongly depends on the type of the spin system formed by the parahydrogen-nascent protons in the SABRE complex: chemically equivalent or non-equivalent. SABRE hyperpolarization in chemically equivalent spin systems has been the subject of considerable attention, even after being relevant only for a limited number of substrates. Efficient hyperpolarization in chemically non-equivalent complexes remained a key challenge, hindering the full potential of high-field SABRE and the ability to polarize a broader range of SABRE substrates. This work reports the multinuclear 1H-15N pulse sequence for efficient 15N hyperpolarization in chemically non-equivalent SABRE complexes. This approach relies on the simultaneous 1H and 15N radiofrequency excitation of the complex-bound nuclei with weak continuous wave magnetic fields. The proposed pulse sequence enabled the hyperpolarization of the 15N nuclei in a mixture of the antimicrobial drugs containing a 5-nitroimidazol moiety at their natural 15N isotopic abundance (0.76% of 15N polarization). Furthermore, it permitted the precise assignment of the SABRE complexes responsible for the polarization transfer.

Plant functional groups modulate the effects of landscape diversity on natural predators

In agricultural landscapes, pests and natural predators are collectively influenced by crop structures, landscape composition, and landscape configuration. While the independent effects of these factors on pests and their natural enemies have been investigated, their interactive effects remain unclear. This study was performed in 15 heterogeneous landscapes centered on mango orchards, with surrounding habitats (forest, rubber, areca, longan, and farmland) sampled to assess their role as sources and habitats for pests and predators. We characterized the landscape composition (habitat cover and landscape diversity) and configuration (patch density). Orchards with and without understory plants were selected using paired designs within each landscape. We measured the abundances of pests (thrips) and predators (lacewings) in the orchards and their surrounding habitats. The independent and interactive effects of landscape composition, configuration, and understory plants on pests and predators were analyzed. Additionally, we explored how the functional groups of understory plants (linear-leaved and nonlinear-leaved) influenced the abundance of pests and predators. Landscape diversity, forest presence, and understory plants showed insignificant effects on thrips but significantly affected lacewing abundance. Specifically, lacewing abundance in orchards was significantly higher in landscapes with forest presence than in those without forest presence. Orchards with understory plants showed significantly higher lacewing abundance than orchards lacking such vegetation. Landscape diversity was negatively correlated with lacewing abundance; however, this effect was only observed in forested landscapes. More importantly, understory plants mitigated the adverse effects in landscapes with forests on lacewing abundance mainly because understory nonlinear-leaved plants, rather than linear-leaved plants, promoted natural predator abundance. This study provides evidence that the effects of landscape diversity are co-dependent on forest presence, plant functional groups, and species identity. We recommend preserving forest in agricultural landscapes and retaining understory nonlinear-leaved plants to collectively address the negative impacts of landscape diversity on natural predators.

Investigating Interaction Dynamics of an Enantioselective Peptide‐Catalyzed Acylation Reaction

Modern nuclear magnetic resonance (NMR) methods like carbon relaxation dispersion in the rotating frame (13C‐R1ρ) and proton chemical exchange saturation transfer (1H‐CEST) are key methods to investigate molecular recognition in biomacromolecules and to detect molecular motions on the µs to s timescale, revealing transient conformational states. Changes in kinetics can be linked to binding, folding, or catalytic events. Here, we investigated whether these methods allow detection of changes in the dynamics of a small, highly selective peptide catalyst during recognition of its enantiomeric substrates. The flexible tetrapeptide Boc‐l‐(π‐Me)‐His‐AGly‐l‐Cha‐l‐Phe‐OMe, used for the monoacetylation of cycloalkane‐diols, is probed at natural abundance using 13C‐R1ρ and 1H‐CEST. Indeed, we detected differences in dynamics of the peptide upon interaction with the diol. Importantly, these differ depending on the enantiomer of the substrate used. These enantiospecific influences of the substrates on the dynamics of the peptide are rationalized using computational techniques. We find that even though one enantiomer reacts faster, as confirmed by reaction monitoring, the other is more tightly bound in DCM (as confirmed by 1H‐saturation transfer difference (STD) measurements). These findings provide insights into the recognition of the substrates and explain the selectivity differences observed between the solvents toluene and DCM.

Natural Increases in Parasitoid and Predator Abundances and a Shift in Species Dominance Point to Improved Suppression of the Sorghum Aphid Since Its Invasion into North America

Melanaphis sorghi (Theobald) (Hemiptera: Aphididae), commonly called the sorghum aphid, is an invasive pest of sorghum (Sorghum bicolor) (L.) in North America. It was first observed in 2013 along the Gulf Coastal Plains ecoregion of Texas, Louisiana (USA), and Mexico, where it quickly established itself as an economically important pest within a few years. This ecoregion contains an established complex of aphid natural enemies, including both predators and parasitoids. In the decade since its invasion, indicators of increased suppression observed across six years and five locations from south to north Texas were as follows: (1) aphid abundances trending downwards across the years, (2) overall natural enemy abundances trending upwards during the same time period, and (3) a key parasitoid and coccinellid species increasing in dominance. Two key taxa, Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae) and six species of coccinellids (Coleoptera: Coccinellidae), were likely responsible for the majority of the pest’s suppression. In light of these findings, the importance of monitoring and stewarding natural enemies of invasive insect pests is discussed as part of a comprehensive strategy to measure and reduce the impact of a pest invasion in large-scale agroecosystems.

Natural Abundance 195Pt-13C Correlation NMR Spectroscopy on Surfaces Enabled by Fast MAS Dynamic Nuclear Polarization

Surface organometallic chemistry has developed as an effective strategy for the rational design and synthesis of well-defined, single-site Pt-based heterogeneous catalysts. Given its high sensitivity to changes in electronic structure, 195Pt solid-state NMR spectroscopy offers a unique approach to investigate the chemical structure and local environment of Pt surface sites, providing invaluable insights for establishing structure-activity relationships. However, this approach is typically hindered by severe sensitivity issues, due to the low loading of Pt sites and the often-encountered large 195Pt chemical shift anisotropies. To overcome this limitation, 195Pt NMR signature of surface metal centers can be indirectly detected through protons. Indirect detection on 13C spins, has also been demonstrated to be feasible by combining isotopic labeling with dynamic nuclear polarization (DNP). Here, we extend this methodology to a supported Pt complex at natural abundance. The material was prepared by grafting (COD)PtMeOSi(OtBu)3 (COD = 1,5-cyclooctadiene, Me = methyl and tBu = tert-butyl) onto partially dehydroxylated silica. DNP enhanced two-dimensional through-bond 13C{195Pt} heteronuclear correlation experiments were successfully implemented at fast magic angle spinning. They enabled the detection of the 0.37% NMR-responsive surface species, thereby showcasing the remarkable sensitivity of this approach and its broad applicability. Key bonding information was obtained by measuring the correlated 13C and 195Pt isotopic chemical shifts as well as 1J(13C-195Pt) coupling constants, confirming directly the coordination structure of the surface Pt sites.

In situ growth of MnO2 on graphitized cellulose nanocrystal: A novel coaxial heterostructures with unblocked conductive networks as advanced electrode materials for supercapacitor

Manganese dioxide (MnO2) with high theoretical capacitance and natural abundance has attracted great attention but is still challenging for use in supercapacitors, due to the limited conductivity and lower electron and ion migration. Here, a facile in situ growth strategy is developed to prepare heterostructural graphitized cellulose nanocrystal (GCNC)/MnO2 with unblocked conductive networks through a hydrothermal reaction. The GCNC with highly ordered graphitic carbon layers as conductive support framework solves the agglomeration problem of MnO2 and increases effective specific surface areas in contact with electrolyte ions. Meanwhile, the stable connection of MnOC covalent bonds enhances the interface bonding, which effectively reduces the contact resistance at the interface of heterostructural GCNC/MnO2 and enhances the interface firmness. The resulting GCNC/MnO2 electrode shows a remarkable specific capacitance of 528.2 F g−1 at 0.5 A g−1. Furthermore, the symmetric supercapacitor based on GCNC/MnO2-15 mM exhibits high rate capability and excellent cycle stability of 100 % capacitance retention after 3000 cycles. This work provides a new path to designing high performance electrode material for sustainable energy technologies.

Cobalt‐Based Materials in Supercapacitors and Batteries: A Review

Energy demand has become a persistent concern and high‐performance energy storage systems have increasingly undergone development. Supercapacitors and batteries pose great impact on energy storage and garner a great deal of attention from technologies and researchers alike. The performance of energy saving devices is primarily determined by the electrode material in terms of high specific capacitance, excellent conductivity, remarkable natural abundance, and unique electrochemical qualities, also large surface area. Cobalt (Co)‐based materials are unique electrode materials widely used in energy storage devices. Nevertheless, a combination of Co and ferrite materials such as nickel, zinc, and copper, or Co/nonferrite materials like metal–organic frameworks and layered double hydroxides has improved their ultimate efficiency. This review deals with energy storage applications of Co‐based materials, categorizing ferrites, their electrochemical characterization, performance, also design and manufacturing intended to supercapacitors and batteries applications. Summarizing the main outcomes of the literature on batteries and supercapacitors, energy storage systems comprising Co‐based materials combined with carbon nanotubes, graphene, silica, copper, zinc, nickel, cadmium, ferrous, and lanthanum are reviewed and discussed. Lithium‐ion batteries are investigated specifically, and perspectives on Co‐based ferrite development for future generations of supercapacitors and batteries are outlined.

Expanding the Toolset of Biomolecular NMR with Efficient and Cost-Effective 17O-Labeling via Bacterial Expression.

Oxygen plays a central role in biomolecular structures and functions, with 17O NMR emerging as a powerful tool for elucidating biomolecular properties. However, the low natural abundance of the NMR-active isotope, 17O (0.0373 %), presents a significant hurdle to its widespread application. Here, we introduce a rapid and cost-effective approach for amino acid-specific 17O-labeling of recombinant proteins. Using a common bacterial expression system and with a 30-minute rapid synthesis protocol of 17O-labeled amino acids via mechanochemical saponification, we have generated Leu- and Phe-specific 17O-labeled recombinant proteins derived from diverse organisms, including CrgA and FtsQ from Mycobacterium tuberculosis and E protein from SARS-CoV-2 virus, demonstrating the applicability of our technique for amino acids known to be isotopically labeled without scrambling. We have acquired magic-angle-spinning 17O NMR of these proteins to confirm the successful 17O labeling and illustrate the sensitivity of 17O NMR to the protein's local structural environments. Our work significantly broadens the accessibility of 17O-NMR, empowering researchers to delve deeper into protein biophysics and biochemistry. This approach opens new avenues for understanding cellular processes at the molecular level by providing an effective tool for investigating oxygen-related interactions and chemistry within biomolecules.

Efficient Development of Nanobody-Based Affinity Chromatography for AAV8 Purification

Adeno-associated virus serotype 8 (AAV8) is a highly effective vector for gene therapy. However, its purification remains challenging due to its low natural abundance and stringent purity requirements. This study aimed to develop an affinity chromatography resin utilizing nanobodies (Nbs) to enhance AAV8 purification efficiency. An AAV8-specific Nb library was constructed, leading to the identification of Nb9 as the most promising candidate based on its high binding affinity, stability and yield. Nb9 was expressed in Pichia pastoris, resulting in high yield and exceptional purity. Two types of agarose resins, Epoxy activated Bestarose 6B and PabPur SulfoLink Beads 4FF, were employed for Nb9 conjugation. Epoxy activated Bestarose 6B resin exhibited a significantly higher ligand density (9.12 mg/mL). Binding capacity assessments of the LQ01 resin demonstrated optimal performance at pH 7.0, with diminishing efficacy at lower and higher pH levels. Different NaCl concentrations influenced the binding efficiency, providing critical insights for refining purification conditions. Purification trials exhibited high specificity, purity and consistent VP protein ratio, as evidenced by SDS-PAGE analysis, confirming effective AAV8 capture and elution. Furthermore, the resin demonstrated robust performance across repeated cycles, retaining 71.9% of its initial binding capacity after 20 uses and maintaining stability with only a 6% reduction after 7 days at 37°C. These findings highlight LQ01's potential for scalable and cost-effective AAV8 purification, while demonstrating the broader applicability of Nbs in affinity chromatography and biotechnological processes.

Clay-Based Materials for Heavy Metals Adsorption: Mechanisms, Advancements, and Future Prospects in Environmental Remediation

Given the severe threats posed by heavy metal pollution to ecological environments and human health, developing effective remediation technologies is of paramount importance. This review delves into the mechanisms, recent advancements, and future prospects of clay mineral-based materials in the adsorption of heavy metals. Clay minerals such as kaolinite, montmorillonite, and bentonite have demonstrated immense potential for the removal of heavy metals from water and soil due to their natural abundance, low cost, and high efficiency. This article summarizes the latest advancements in the adsorption of heavy metals like chromium, copper, lead, cadmium, arsenic and hydrargyrum by clay minerals, while examining how chemical and physical modifications can enhance the adsorption capacity, selectivity, and stability of these minerals. Furthermore, this review discusses how factors such as pH, temperature, and ionic strength affect adsorption efficiency and outlines challenges and future research directions for optimizing clay-based adsorbents in environmental applications.

Natural resource abundance, digitalization and institutional governance: The critical challenges towards net-zero transformation

Amidst the efforts to balance economic growth and climate change concerns, natural resource consumption accounts for environmental degradation. The current study deliberates on ecological sustainability by examining how natural resource consumption, digitalization, and institutional governance impact environmental degradation in natural resource-dependent economies. Our econometric findings from CS-ARDL report that natural resource consumption and economic growth lead to environmental deterioration, while digitalization developments and institutional governance safeguard environmental sustainability. Similar findings are endorsed by robustness analysis to help propose novel environmental policy frameworks.

Comparative Analysis of Community Energy Projects: Policy Lessons for Kenya from the United Kingdom

Assuming a scope for policy learning across jurisdictions, this paper compared policies relevant to community energy projects (CEPs) in a developed country where they have been adopted (i.e. the UK), against policies in an emerging country where CEPs are scarce (i.e. Kenya). Through comparative analysis, successes and failures in the policies’ landscapes were examined, with the aim of distilling lessons that could enhance CEPs adoption in Kenya. Both countries have some similar core functional mechanisms in their policies, e.g. Feed-in-Tariffs, energy auctions, and grid access. These are demand-side in nature and create a market for CEPs while derisking investments to local communities. However, key differences exist, reflecting the levels of maturity in the energy mix and policy-making in either country. The UK has more demand-side and ‘implementation oriented’ policies, compared to Kenya. For Kenya, key lessons include incentives prioritising appropriate grant programs, Feed-in-Tariffs targeting CEPs, adopting Smart Export Guarantee, implementing grid connection agreements, and fostering centres for data and knowledge exchange. However, these require a laser-focus to make them bespoke to the Kenyan context. Our recommendations envisaged a carefully calibrated confluence of pull-push policy factors, involving: a CEPs-friendly policy landscape, CEPs targets under a long-term strategy, natural abundance of different RE sources, and, Kenya’s appetite for using different policy solutions for different needs. Two key areas for relevant research are worth mentioning: exploring where the equilibrium for cost-effective energy mix integrating CEPs lies, in Kenya’s future, and; empirically exploring systems-wide analyses to reveal the inter-dependencies and inter-relations of the various contextual and policy factors, aimed at CEPs as an outcome.

Soil nitrogen biogeochemistry and hydrological characteristics shape the nitrate levels in a river.

The high levels of nitrate (NO3-) in the surface water have contributed to eutrophication and other eco-environmental damages worldwide. Although the excessive NO3- concentrations in rivers were often attributed to anthropogenic activities, some undisturbed or slightly disturbed rivers also had high NO3- levels. This study utilized multi-pronged approaches (i.e., river natural abundance isotopes, 15N-labeling techniques, and qPCR) to provide a comprehensive explanation of the reason for the high NO3- levels in a river draining forest-dominated terrene. The river natural abundance isotopes (δ15N/δ18O-NO3-) indicated that the soil source (i.e., soil organic nitrogen-SON and chemical fertilizer-CF) were the primary contributors to the NO3-, and the NO3- removal was probably prevalent in the basin scale. The 15N-labeling techniques quantitatively showed that denitrification and anammox were stronger than nitrification in the soils and sediments. Structural equation models suggested that nitrification in the soils was regulated by NH4+-N contents, which, in turn, were closely related to fertilization in spring. Denitrification and anammox were largely controlled by elevation and functional gene abundances (i.e., nirK and hzsB, respectively). The hydrological isotopes (i.e., δD/δ18O-H2O) indicated that the transport of NO3- from soil to the river was related to the intensity of runoff leaching to the soil, In contrast, the riverine NH4+ was largely from point sources; thus, increasing runoff led to a dilution effect. This study clearly showed that soil biogeochemistry and hydrological condition of a river basin jointly shaped the high NO3- levels in the almost undisturbed river.

Comparison of natural abundance and enriched 15N methods to quantify nitrogen fertilizer recovery in maize under field conditions

Comparison of natural abundance and enriched 15N methods to quantify nitrogen fertilizer recovery in maize under field conditions