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Variations in precipitation and atmospheric N deposition affect water and N availability in desert and thus may have significant effects on desert ecosystems. Haloxylon ammodendron is a dominant plant in Asian desert, and addressing its physiological acclimatization to the changes in precipitation and N deposition can provide insight into how desert plants adapt to extreme environments by physiological adjustment. Carbon isotope ratio ( δ13 C) in plants has been suggested as a sensitive long-term indicator of physiological acclimatization. Therefore, this study evaluated the effect of precipitation change and increasing atmospheric N deposition on δ13 C of H. ammodendron. Furthermore, H. ammodendron is a C 4 plant; whether its δ13 C can indicate water use efficiency (WUE) has not been addressed. In the present study, we designed a field experiment with a completely randomized factorial combination of N and water and measured δ13 C and gas exchange of H. ammodendron. Then we calculated the degree of bundle-sheath leakiness ( φ ) and WUE of the assimilating branches of H. ammodendron. δ13 C and φ remained stable under N and water supply, while N addition, water addition and their interaction affected gas exchange and WUE in H. ammodendron. In addition, δ13 C had no correlation with WUE. These results were associated with the irrelevance between δ13 C and the ratio of intercellular to ambient CO 2 concentration ( ci / ca ), which might be caused by a special value (0.37) of the degree of bundle-sheath leakiness ( φ ) or a lower activity of carbonic anhydrase (CA) of H. ammodendron. In conclusion, δ13 C of H. ammodendron is not sensitive to global change in precipitation and atmospheric N deposition and cannot be used for indicating its WUE.

Reducing ammonia (NH3) volatilization from croplands while satisfying the food demand is strategically required to mitigate haze pollution. However, the global pattern of NH3 volatilization remains uncertain, primarily because of the episodic nature of NH3 volatilization rates and the high variation of fertilization practices. Here, we improve a global estimate of crop-specific NH3 emissions at a high spatial resolution using an updated data-driven model with a survey-based dataset of the fertilization scheme. Our estimate of the globally averaged volatilization rate (12.6% ± 2.1%) is in line with previous data-driven studies (13.7 ± 3.1%) but results in one-quarter lower emissions than process-based models (16.5 ± 3.1%). The associated global emissions are estimated at 14.4 ± 2.3 Tg N, with more than 50% of the total stemming from three stable crops or 12.2% of global harvested areas. Nearly three-quarters of global cropland-NH3 emissions could be reduced by improving fertilization schemes (right rate, right type, and right placement). A small proportion (20%) of global harvested areas, primarily located in China, India, and Pakistan, accounts for 64% of abatement potentials. Our findings provide a critical reference guide for the future abatement strategy design when considering locations and crop types.

Temperate desert soils are an important source of atmospheric nitrous oxide (N2O). However, it is uncertain how N2O emissions respond to warming, increased rainfall and nitrogen (N) addition in such soils. A multifactorial field manipulation study was carried out in the Gurbantunggut Desert, China's second largest desert, to investigate how these factors influence desert soil N2O emissions and to assess inter‐year variation. In our 3‐year study, under current climatic conditions, the annual flux of N2O in this temperate desert soil was 0.13 ± 0.02 kg N ha−1 yr−1, with the period of no plant growth contributing 43% of the annual emission. Surprisingly, there was no significant change in annual N2O flux under warming (+1°C) or increased precipitation (30%, +60 mm yr−1). In contrast, N2O emissions were significantly affected by extreme drought followed by precipitation. Additional N input, at 30 or 60 kg N ha−1 yr−1, greatly elevated annual N2O emission by 55–133%. The combined impact of N deposition and increasing rainfall on N2O emission was greater than that of any single factor, except for N deposition. This suggests that N2O emissions in this desert are driven primarily by soil available N content and are less sensitive to variations in soil temperature and moisture.

Desert soils are a significant global sink for methane (CH4). However, it remains unclear how CH4 uptake in temperate deserts could respond to elevated precipitation, nitrogen (N) deposition and warming. An in situ field experiment was conducted to investigate these effects on CH4 uptake in the Gurbantunggut Desert, northwest China, from September 2014 to August 2017. This desert was a weak sink for CH4 (0.83 kg C ha−1 year−1) over this period, with the non-growing season (November–March) accounting for 30.5% of the annual CH4 uptake. Pulse CH4 uptake was found to result from increased water addition (by 30% or 60 mm year−1) and low N deposition (30 kg N ha−1 year−1) which enhanced annual CH4 uptake by 62.3 and 52.6%, respectively. However, no significant impact of high N deposition (60 kg N ha−1 year−1) was found. Warming in open topped chambers (OTCs) had a variable effect on CH4 uptake, which mainly depended on variation in soil moisture. The response in CH4 uptake to the interaction between water and N addition was less than that for the individual factors, except under conditions of warming. In addition, CH4 uptake was significantly positively correlated to water-filled pore space (WFPS), differing from observations in forest and grassland ecosystems. Structural equation modeling indicated that CH4 uptake was significantly enhanced by soil moisture and the underground biomass of ephemerals. Overall, the CH4 sink of this desert was significantly enhanced by increasing precipitation and low N deposition, rather than warming, which may become a feedback for future climate.

Ascorbic acid (AA) is one of the most important vitamins and serves many physiological activities in the body. In this work, we propose a simple colorimetric sensor for the rapid detection of AA through the redox reaction between CoOOH nanoflakes and ascorbic acid with the 2, 2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) as a colorimetric signal indicator. CoOOH nanoflakes could catalytically oxidize colorless ABTS to produce green oxidized ABTS (ox ABTS) with an absorption band at 412 nm in UV–vis spectra. The presence of AA could induce the oxidation of ABTS, resulting in a significant color fading and decrease of the absorbance at 412 nm. Thus quantitative detection of AA is realized. Under the optimal experimental conditions, the linear range is obtained from 0.5 to 15 μM with a lower detection limit of 0.16 μM (S/N = 3). Particularly, this colorimetric assay is capable of detecting AA in different vitamins C tablet and fresh kiwi fruit samples. Hence, the fast response, high sensitivity and easy operation of the proposed colorimetric sensor make it suitable for further application in bioassay.

Croplands are the single largest anthropogenic source of nitrous oxide (N2O) globally, yet their estimates remain difficult to verify when using Tier 1 and 3 methods of the Intergovernmental Panel on Climate Change (IPCC). Here, we re-evaluate global cropland-N2O emissions in 1961–2014, using N-rate-dependent emission factors (EFs) upscaled from 1206 field observations in 180 global distributed sites and high-resolution N inputs disaggregated from sub-national surveys covering 15593 administrative units. Our results confirm IPCC Tier 1 default EFs for upland crops in 1990–2014, but give a ∼15% lower EF in 1961–1989 and a ∼67% larger EF for paddy rice over the full period. Associated emissions (0.82 ± 0.34 Tg N yr–1) are probably one-quarter lower than IPCC Tier 1 global inventories but close to Tier 3 estimates. The use of survey-based gridded N-input data contributes 58% of this emission reduction, the rest being explained by the use of observation-based non-linear EFs. We conclude that upscaling N2O emissions from site-level observations to global croplands provides a new benchmark for constraining IPCC Tier 1 and 3 methods. The detailed spatial distribution of emission data is expected to inform advancement towards more realistic and effective mitigation pathways.

The aim of this study was to develop carbonaceous materials hybridized with anatase TiO2 composed of Activated Carbon-TiO2 (AC-TiO2), Olive Pits-TiO2 (OP-TiO2) and Wood Shaving-TiO2 (WS-TiO2) by ultrasonic-assisted sol-gel process for the photocatalytic Cr(VI) reduction under UV and narrow visible light. The morphology, crystal structure, surface chemistry and optical properties of the as-prepared and bare-TiO2 were investigated by SEM-EDS, XRD, FTIR, BET, UV-DRS, XPS and photo-current measurements. Unlike bare-TiO2, these composite photocatalysts exhibited an enhanced absorption in visible-light. The band gap energies were found to be 3.20 eV, 2.89 eV, 2.81 eV and 2.95 eV for bare-TiO2, AC-TiO2, OP-TiO2 and WS-TiO2, respectively. On the other hand, as-prepared photocatalysts showed significantly improved photocatalytic Cr(VI) reduction performances under UV and visible light illumination compared to bare-TiO2. A total reduction of 10 ppm of Cr(VI) was obtained after 30 min, 50 min and 130 min under visible light (>420) for AC-TiO2, OP-TiO2 and WS-TiO2, respectively at pH: 3 and in the presence of 10 ppm tartaric acid as hole scavenger, while no reduction was detected for bare-TiO2 under visible light (>420). The efficient photocatalytic reduction of Cr(VI) under visible light by AC-TiO2, OP-TiO2 and WS-TiO2 was mainly due to (i): the narrow band gap of TiO2 nanoparticle deposited in carbonaceous materials, (ii): self-photo-sensitizer role of carbonaceous materials via Ti O C bonds and (iii): the electron transfer from TiO2 to carbonaceous materials.

In this study, in situ sulfur-doped carbon nitride nanosheets (S-g-C3N4 NSs) are used as the signal readout for the sensitive and selective sensing of L-cysteine (L-Cys) in human serum samples based on the competitive coordination chemistry of Cu2+ between L-Cys and S-g-C3N4 NSs. S-g-C3N4 NSs are prepared by using trithiocyanuric acid as a precursor for the first time, which exhibits stronger electrogenerated chemiluminescence (ECL) intensity compared with pristine graphitic carbon nitride nanosheets (g-C3N4 NSs). The ECL signals of the S-g-C3N4 NSs can be quenched by Cu2+ and the subsequent presence of L-Cys can recover the ECL signals of the S-g-C3N4 NSs. These changes are ascribed to the higher coordination ability between Cu2+ and L-Cys than that between Cu2+ and the S-g-C3N4 NSs. On the basis of this, the concentration of L-Cys can be quantitatively determined. Under optimized conditions, the ECL intensity recovery shows a linear relationship with the L-Cys concentration range from 30 nM to 0.2 mM with a lower detection limit of 5 nM (S/N = 3). The proposed method is highly sensitive and selective and is thus particularly useful for fast and simple clinical diagnosis of diseases, such as Alzheimer's disease and cardiovascular disease.

Abnormal concentration of hydrogen peroxide (H2O2) in blood plasma and cells may lead to several diseases. Thus, it is important to develop a selective and sensitive method to monitor H2O2. In the present work, a novel nonenzymatic H2O2-sensing platform based on cobalt oxyhydroxide (CoOOH)/reduced graphene oxide (RGO) nanocomposite was fabricated. CoOOH nanoflakes were firstly synthesized via soft chemistry routes and then assembled on the surface of RGO. A series of characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy demonstrated that hexagonal CoOOH nanoflakes were well distributed on the surface of RGO. The nanocomposite exhibited excellent electrochemical performance for H2O2 detection. Two linear ranges of 6–200 μM and 200–1500 μM were obtained, and the detection limit was 0.01 μM (signal-to-noise ratio was 3). The good performance was attributed to more exposed catalytic active sites of CoOOH nanoflakes compared with zero-dimensional nanoparticles and outstanding conductivity of RGO as well as their synergistic effect. Moreover, the nanocomposite was used to detect H2O2 from human serum and HeLa cells with satisfactory results.

A simple and economical colorimetric probe for the detection of uric acid (UA) based on redox reaction of 3,3ʹ,5,5ʹ-tetramethylbenzidine (TMB) with HAuCl4 was designed. A novel chromogenic reaction was primarily demonstrated based on the reaction between HAuCl4 and TMB, which produces many color responses from red to blue in the resulting solutions. In this method, the colorless TMB can be oxidized by HAuCl4 to generate oxidized TMB (oxTMB) and induce a blue color solution which corresponding to the absorption peak at 652 nm. However, HAuCl4 would be reduced in the presence of UA, which inducing a blue color diminishing of HAuCl4-TMB system and decrease of the absorbance at 652 nm because the content of HAuCl4 was declined in the solution. Based on this phenomenon, we proposed a method to detect UA which does not require nanomaterials or organic probes. The detection conditions, pH value, incubation time and the concentration of HAuCl4 and TMB were optimized. The probe displayed a linear response in the range of 0.001–8.0 μM and 8.0–80.0 μM, with a detection limit of 0.67 nM (S/N = 3). This method has been successfully applied to the determination of uric acid in human urine samples.

A highly sensitive and selective colorimetric assay is proposed for the detection of mercury ions (Hg2+), cadmium ions (Cd2+) and ascorbic acid (AA) using trithiocyanuric acid (TMT) functionalized gold nanoparticles (TMT-AuNPs). TMT-AuNPs are dispersed in 40 mM NaCl solution, while the presence of Hg2+ and Cd2+ can induce TMT-AuNPs aggregate due to the strong interaction of Hg2+ and Cd2+ with TMT. Then the quantitative detection of Hg2+ and Cd2+can be realized in the linear range from 5 × 10−9 to 1 × 10−6 M and 1 × 10−8 to 3 × 10−7 M, with a lower detection limit of 2.8 nM for Hg2+ and 3.5 nM for Cd2+ (S/N = 3), respectively. To distinguish Hg2+ from Cd2+, a reductive biological small molecule ascorbic acid (AA) was used based on the different redox interaction of AA with Hg2+ and Cd2+. When the mixture of AA and Hg2+ was added into TMT-AuNPs solution, the state of TMT-AuNPs was still dispersed because Hg2+ was reduced by AA. On the contrary, when the mixture of AA and Cd2+ was added into TMT-AuNPs solution, the TMT-AuNPs was aggregated and the color of the solution has no obvious change compared to the system of Cd2+-TMT-AuNPs since the weak interaction between AA and Cd2+. Thus, AA could be detected. A linear correlation exists between the ratio of A640/A520 and the concentration of AA in the range from 1 × 10−8 to 1 × 10−6 M with a detection limit of 4.8 nM (S/N = 3). Importantly, it has been successfully applied to determine Hg2+, Cd2+ in lake water and AA in vitamins C tablet.

Mitigating soil nitrous oxide (N2O) emissions is essential for staying below a 2 °C warming threshold. However, accurate assessments of mitigation potential are limited by uncertainty and variability in direct emission factors (EFs). To assess where and why EFs differ, we created high-resolution maps of crop-specific EFs based on 1,507 georeferenced field observations. Here, using a data-driven approach, we show that EFs vary by two orders of magnitude over space. At global and regional scales, such variation is primarily driven by climatic and edaphic factors rather than the well-recognized management practices. Combining spatially explicit EFs with N surplus information, we conclude that global mitigation potential without compromising crop production is 30% (95% confidence interval, 17–53%) of direct soil emissions of N2O, equivalent to the entire direct soil emissions of China and the United States combined. Two-thirds (65%) of the mitigation potential could be achieved on one-fifth of the global harvested area, mainly located in humid subtropical climates and across gleysols and acrisols. These findings highlight the value of a targeted policy approach on global hotspots that could deliver large N2O mitigation as well as environmental and food co-benefits. Estimating the global cropland N2O mitigation potential is limited by the uncertainty and variability of direct emission factors (EFs). Here, using a data-driven approach with 1,507 chamber-based field observations of EFs, the study shows that EF variation is primarily driven by climatic and edaphic factors. Two-thirds of the mitigation potential could be achieved on one-fifth of the global harvested area, mainly located in humid subtropical climates and across gleysols and acrisols.

In desert ecosystems, nitrogen (N) deposition can alter the soil N pools (soil available N or total N) or plant N uptake while rarely changing other nutrient contents. In this chapter, we reviewed the effects of N deposition on China’s desert ecosystems based on experimental results. Acidification of the soil and toxic effects on the microbes often occur under high N addition. Soil enzyme activities in response to N additions depended on the N applied rates and the specific enzyme types, with oxidative enzymes more stable than hydrolytic enzymes. Soil microbial biomass N was usually increased by N addition, while the responses of microbial biomass carbon depended on shrub existence. The soil microbial community structure was generally not affected by N addition, although increased soil bacterial phospholipid fatty acid (PLFA) and non-changes in soil fungal PLFAs were observed. For the greenhouse gas emission, N addition cannot shift the soil respiration except under high moisture condition. Positive effects of N input on nitrous oxide emission with no or negative methane uptake were found. The growth and biomass allocation of vascular plants under N addition depended on life-forms/species in desert ecosystems. The increased individual growth under N addition was not always observed in productivity because of changes in the community structure. With the increase in N added rates, abundance, richness, and density usually decreased, and the effects were affected by the years exposed to N addition. More water supply can expand the N effects on plant growth and diversity in desert ecosystems. Lower levels of N addition also stimulated growth of nonvascular plants (biocrusts), while higher levels exhibited negative effects.

In the present work, 2­-aminobenzothiazole and 2-­amino­-4-­thiazoleacetic acid functionalized graphene decorated with fluorine, chlorine and iodine@SnO2 nanoparticles were prepared by hydrothermal synthesis method, respectively. The morphology and structure of these obtained nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction analysis and X-ray photoelectron spectrum (XPS). Results of cyclic voltammetry (CV) demonstrated that thiazole derivatives functionalized graphene decorated with fluorine@SnO2 had superior performance for detection of Cu2+ than others. Electrochemical sensor based on this nanocomposite was constructed for detection of Cu2+ and a wider linear range was obtained from 2 to 1000 nM with a detection limit of 0.3 nM (S/N = 3). Moreover, simultaneous detection of Cd2+, Cu2+ and Hg2+ was realized with high sensitivity and selectivity by the sensor owing to synergetic effects of thiazole derivatives, fluorine@SnO2 and graphene. Finally, the sensor was applied to real sample analysis with a satisfactory result.

Macrophorins are representative examples of isoprenoid epoxycyclohexenones containing cyclized drimane moieties. We located and characterized the biosynthetic gene cluster of macrophorin from Penicillium terrestris. MacJ encoded by this cluster was characterized to be the first example of a membrane-bound type-II terpene cyclase catalyzing the cyclization of meroterpenoids via direct protonation of the terminal olefinic bond in acyclic yanuthones. The late-stage functionalization and substrate promiscuity of MacJ make it a potential biocatalyst for the synthesis of macrophorin analogues.

The nanocomposite of polyamidoamine (PAMAM) modified gold nanoparticles (pAuNPs)/SnO 2 /graphene sheets (GNs) was prepared by a new method. That is, the well dispersed AuNPs were prepared in the presence of PAMAM and resembled on the surface of 5,10,15,20-tetrakis (4-sulonatophenyl) porphyrin (H 4 TPPS 2– ) modified graphite oxide (GO) by electrostatic interaction. Then the well-distributed SnO 2 was obtained from SnCl 2 with the aid of GO and GO was reduced to graphene by hydrazine hydrate. The synthesized nanocomposite was characterized by Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). Cyclic voltammetry (CV) experiment demonstrated that the nanocomposite exhibited excellent electrochemical performance for the detection of dopamine (DA). Then the quantitative detection of DA was carried out by differential pulse voltammetry (DPV) in the presence of ascorbic acid (AA). A linear range of 0.03–10 μM was obtained with a correlation coefficient of 0.9970. The detection limit was as low as 8 nM (S/N = 3). Moreover, the proposed method was applied for the determination of DA in real serum samples.

In the present work, polydopamine (PDA) modified reduced graphene oxide (pRGO)/SnO2/Au nanoparticles (NPs) were synthesized. SnO2/AuNPs were prepared through the redox reaction between reductive stannous(II) ions and oxidative auric(III) ions without any other reagents, and then the as-prepared graphene oxide (GO) was reduced and stabilized with the help of DA followed by decorating with SnO2/AuNPs. The morphology and structure of the hybrid nanomaterials were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. Then we constructed electrochemical sensors based on the hybrid nanomaterials for the determination of dopamine (DA). Cyclic voltammetry (CV) results showed that the hybrid nanomaterials had better sensing performance than pRGO/AuNPs and pRGO. Differential pulse voltammetry (DPV) showed that the separation of oxidation peak potentials for ascorbic acid (AA)–DA, uric acid (UA)–DA and UA–AA was about 200 mV, 100 mV and 300 mV, respectively. The linear range for the detection of DA was from 0.008 μM to 20 μM with a coefficient of 0.9986. The detection limit was 5 nM (S/N = 3). These indicate the selective and sensitive detection of DA. Finally, the constructed sensors were also applied to detect DA in human real samples.

Carbon nanofibers were widely utilized to improve microwave absorption properties since they are a promising lightweight candidate. Adjustable conductive nanostructures of carbon nanofibers were synthesized by electrospinning technique. The conductive network is controlled by the polyvinyl pyrrolidone (PVP) content due to the special hygroscopicity of PVP. The increased adhesive contacts of nanofibers provide more transmission paths for electrons to reduce the effect of air dielectric. Satisfactorily, the carbon nanofibers that carbonized from the polyacrylonitrile (PAN) and PVP (the mass ratio is 6:4) show excellent microwave absorption performance. The minimum reflection loss (RL) value is −51.3 dB at 15.2 GHz and the maximum effective absorption frequency width (

An experiment was conducted to investigate the effect of precipitation and N deposition on N2O and CH4 fluxes and soil respiration (Rs) in the Gurbantunggut Desert from September 2014 to August 2015. The desert was a weak sink for CH4 (−0.92 kg C ha−1 yr−1) and a small source of N2O (+0.13 kg N ha−1 yr−1) and the annual rate of Rs was 874 kg C ha−1. Our work confirmed a relatively strong sink for CH4 in desert soils. Significant impacts on N2O, CH4 fluxes and Rs were found by increasing precipitation, with pulses of CH4 uptake and Rs accounting for 79.1% and 33.2% of annual CH4 uptake and Rs, respectively. N2O and CH4 fluxes were significantly enhanced by 7.8–109.6% by N addition, but it had no significant effect on Rs. Statistical significant interactions of precipitation and N addition on N2O and CH4 fluxes were found, and on Rs was lower than any single factor. Our results indicate that the Gurbantunggut Desert is a weak sink for CH4 and a small source of N2O, and is sensitive to elevated precipitation and N deposition.

It's a major challenge to explore highly active and stable electrocatalysts for efficient hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). In this work, we report a new hybrid electrocatalyst: iron-cobalt decorated nitrogen doped carbon/reduced graphene oxide-700 °C (Fe-Co-CN/rGO-700). The catalyst shows an excellent electrocatalytic performance toward HER and OER in alkaline solution, which has lower overpotentials of 0.215 V and 0.308 V at the current density 10 mA cm−2, respectively, and this catalyst has an outstanding durability (after 45 h). The excellent activity mainly benefit from the highly dispersed iron/cobalt species, sheet structure with high porosity, the improvement of electronic structures with nitrogen-doped carbon and high conductivity of rGO. Combined with the density function theory (DFT) calculations, the improvement of the HER and OER performance were also attributed to the balance of adsorption/desorption of the hydrogen and oxygen-containing intermediates, and the increased electronic states density near the Fermi level. The proposed work provides a novel and simple strategy to synthesize a porous carbon electrocatalyst material using metal-organic frameworks (MOFs) as precursor with high activity and strong stability for HER and OER.

In this paper, a sensitive and selective electrochemical sensor was constructed for nickel (II) detection by employing the electrode material of zeolitic imidazolate framework-8@dimethylglyoxime/β-cyclodextrin/reduced graphene oxide (ZIF-8@DMG/β-CD/RGO). The material was characterized and analyzed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Nitrogen adsorption-desorption isotherms in detail. In these composite, ZIF-8 served as the supporting material of DMG which was the selective complexing agent to Ni (II), RGO employed conductivity while β-CD prevented the aggregation of RGO sheets. With these features, the sensor showed a wide linear range of 0.01–1.0 μM and a low detection limit of 0.005 μM (S/N = 3). Interferences of diethanol, citric acid, humic acid, Triton X-100 and some common metal ions can be ignored to some extent. Finally, the sensor was applied to Ni (II) detection in real water sample.

Residues of norfloxacin (NF) in environment caused public concerns for its side effects and the presence of bacteria resistance. Developing novel method for selective and sensitive determination of NF is important. In the present work, an electrochemical sensing method was proposed by employing the electrode material composed of graphitized carbon supported Ni/NiO clusters (Ni/NiO/C) and β-Cyclodextrin modified reduced graphene oxide (β-CD/RGO). These materials were characterized and analyzed by Fourier transform infrared (FT-IR), Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM) in detail. β-CD/RGO as electrode modification material with the ability to adsorb more guest molecules and promote electron transfer had been reported. Herein, electrochemical test demonstrated that Ni/NiO/C can catalyze NF oxidation and showed similar conductivity with β-CD/RGO. Benefited from the synergy effect between Ni/NiO/C and β-CD/RGO, the proposed method showed a wide linear range of 0.4 to 80 μM and a low detection limit of 0.01 μM (S/N = 3) for NF detection. Additionally, the proposed method was also applied to detect NF added in water sample with good recoveries obtained.

Overuse of urea, low nitrogen (N) utilization, and large N losses are common in maize production in North China Plain (NCP). To solve these problems, we conducted two field experiments at Shangzhuang and Quzhou in NCP to test the ability of a newly developed urease inhibitor product Limus® to decrease NH3 volatilization from urea applied to maize. Grain yield, apparent N recovery efficiency (REN) and N balance when using urea applied with or without Limus were also measured over two maize growing seasons. Cumulative NH3 loss in the two weeks following urea application without Limus ranged from 9–108 kg N ha−1, while Limus addition significantly decreased NH3 loss by a mean of 84%. Urea with Limus did not significantly increase maize yields (P N with Limus was observed at QZ. The use of urea-N plus Limus would permit a reduction in N applications of 55–60% compared to farmers’ practice and/or further 20% N saving compared with optimized urea-N rate (150 kg N ha−1, based on N requirement by target yield of 7.5 t ha−1), and would achieve the same maize yields but with significantly decreased NH3 loss and increased N utilization.

Selective and sensitive determination of nitrite is of great importance in practical application. In the present work, a novel nitrite sensing platform was built based on the fabrication of nitrogen-doped-carbon-coated hexagonal cobalt oxyhydroxide (CN@CoOOH) on reduced graphene oxide (RGO) using zeolitic imidazolate framework (ZIF)-67 as a precursor. The CN@CoOOH/RGO nanocomposite was confirmed by UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectrum, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. We applied the nanocomposite to detect nitrite selectively and sensitively through amperometry for the first time. The anodic current values increased with the addition of nitrite. Therefore, the concentrations of nitrite were quantitatively detected using a CN@CoOOH/RGO based sensor. A wider linear range of 0.1 to 7000 μM was obtained with a lower detection limit of 10 nM (S/N = 3). The proposed method was also applied to detect nitrite released from normal liver cells and human hepatoma cells.

Nitrous oxide (N2O) is an important greenhouse gas and a precursor of ozone depletion in the upper atmosphere, thus contributing to climate change and biological safety. The mechanisms and response characteristics of N2O emission in desert soils to precipitation and nitrogen (N) deposition are still unclear. To further elucidate this, an in-situ experiment was conducted in the Gurbantunggut Desert, a temperate desert in China, between June and September 2015 and 2016. The response in N2O flux to water addition (equivalent to 5 mm precipitation) was very transient in summer, only lasting one to two days. This was attributed to the rapid decrease in soil moisture following the water addition, due to the high temperature and drought conditions, and there was no significant change in N2O emission or in the abundance of N-related key functional genes. In contrast, N2O emissions increased significantly in response to N addition. This was associated with an increase in functional gene abundances of amoA (ammonia oxidizing bacteria (AOB)) and ammonia-oxidizing archaea (AOA), which responded positively to increasing soil NH4+-N content, but were inhibited by increasing soil NO3−-N content. The abundance of the nirS (nitrate reductase) gene was significantly increased by increasing soil NO3−-N content. Interestingly, the indirect effect of increased soil moisture in enhancing N2O emission by increasing the abundance of AOA was offset by a direct effect of soil moisture in inhibiting soil N2O emission. Overall, N2O emissions were mainly controlled by AOA rather than AOB in summer, and were more sensitive to soil available N than to soil moisture in this temperate desert.