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Harvesting energy from sunlight is an essential component of thermal load in an outdoor environment. Controlling the solar heating effects is therefore important. Inspired by the tunable coupling of the pigment cells and iridocytes in squid skin, we simulated a design for the tunable coupling of a grating and hyperbolic material. This composite metamaterial possessed thermoregulatory properties. The tiny mechanical action (∼250 nm) can tune the solar absorptive quality from 0.9 to 0.03 while keeping the radiative quality small. Our findings could have applications in dynamic and simply controlled thermoregulatory systems for outdoor structures and other technologies that regulate solar infrared absorption.

Carbon (C) sequestration in terrestrial ecosystems needs to ensure the reactive nitrogen (Nr) supply. However, the organic C:N ratio is rarely considered in both estimates of C sequestration in terrestrial ecosystems and N budget at regional and global scale. Here we propose an approach for extracting Nr sequestrated in terrestrial ecosystems with C (termed as Nrc) from N budget and then assessing the rationality of estimates of C sequestration in terrestrial ecosystems and N budgets by using the sequestrated organic C:N ratio as a criterion. We extracted Nrc from the N budget of IPCC AR5 at global scale and Chinese N budget (Proc Natl Acad Sci (USA) 112:8792, 2015) at regional scale based on the assumptions that there is no net Nr accumulation in agricultural products and no net Nr (except N2O) accumulation in the atmosphere at annual temporal scale, and N2O is not involved in biological processes. By taking the C sequestration in terrestrial ecosystems from C budget of IPCC AR5 (2.1 Pg C/yr during 2000–2009) to assess the N budget from the same report, the organic C:N ratios calculated by the Nrc extracted from both the upper ranges and averages of Nr input and output in global N budgets of IPCC AR5 fell outside the rational range of organic C:N ratio, but the organic C:N ratio (=31) calculated by the Nrc (68.1 Tg N/yr) extracted from the lower ranges of the N budget fell very well into the range of organic C:N ratio in global terrestrial ecosystems. Nrc extracted from Chinese N budget was 11.6 Tg N/yr in 2010, which could be combined with C into Chinese terrestrial ecosystems in a range between 0.14–0.66 Pg C/yr with a robust estimate of 0.36 Pg C/yr by applying the global terrestrial ecosystem sequestrated organic C:N ratio to calculation. The results indicate that the proposed approach for extracting Nrc from N budget works well. Checking the estimated organic C:N ratio in terrestrial ecosystems will help to assess whether the C and/or N budgets are rational or not. Graphical abstract

The effects of land use on riverine N

Information about effects of conversion from rice fields to vegetable fields on denitrification process is still limited. In this study, denitrification rate and product ratio (i.e., N

Molybdenum disulfide (MoS2) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS2 because of its native stubborn n-type conductivity. Substitutional transition metal doping has been proved to be an effective approach to tune their intrinsic properties and enhance device performance. Herein, we report the growth of Nb-doping large-area monolayer MoS2 by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses n-type conductivity in MoS2 and shows an ambipolar transport behavior after annealing under the sulfur atmosphere, which highlights the p-type doping effect via Nb, corresponding to the density functional theory calculations with Fermi-level shifting to valence band maximum. This work provides a promising approach of two-dimensional materials in electronic and optoelectronic applications.

Few-layer black phosphorus generally shows p-type or hole dominated ambipolar transfer characteristics with electron mobility being equal to or nearly zero, and tends to degenerate very quickly under ambient conditions. Herein, we demonstrate an effective surface charge transfer doping and passivation scheme on few-layer black phosphorus through in situ encapsulation by thin layer hexagonal boron nitride and surface modification by HfO2 or MgO. Both HfO2 and MgO can provide an electron doping effect on black phosphorus, resulting in an increase in electron mobility over one order of magnitude up to 65 cm2 V−1 s−1 modified by HfO2 and 305 cm2 V−1 s−1 modified by MgO, respectively. The highest electron mobility achieved approaches the record value in the literature, and the hole mobility of the same sample is also as high as 1150 cm2 V−1 s−1. Thin layer hexagonal boron nitride not only isolates black phosphorus from ambient conditions, but also protects it from destruction by metal oxides' deposition. Our work provides an effective technique to simultaneously realize electron doping and passivation on black phosphorus field effect transistors.

As a promising layered material for electronic, optical and thermoelectric applications, black phosphorus nanoribbons have attracted much attention. Herein, single crystal black phosphorus nanoribbons have been successfully grown by chemical vapor transport. The microstructure characterization results clearly reveal that the zigzag direction is the preferential growth direction of the nanoribbons. The performance of FETs shows the good electrical properties of black phosphorus. Our research provides an economical method for growing high quality BPNRs, offering more possibilities for experimental research and their applications.

Surface functionalization of layered transition metal dichalcogenides is of fundamental significance to a wide range of electronic and optoelectronic applications. Here, using density functional theory calculations, the n-type surface functionalization of a MoS2 monolayer using Arg and Lys amino acids was successfully predicted. Air stability and effective electron doping of the system have been demonstrated using Raman spectroscopy, photoluminescence spectroscopy, and the performance of field-effect transistors based on the MoS2 monolayer. The long-term stability in air and reversibly controllable doping properties make Arg and Lys amino acids an attractive option for modulating electronic and optoelectronic devices using a simple and effective route.

Elevated atmospheric carbon dioxide (eCO

A 15 N tracing study was conducted with soils from a long-term nitrogen (N) fertilization experiment to quantify the concurrent gross N transformation rates in soil and the underlying mechanisms for crop yield and N2O emission variability. The treatments were chemical fertilization (NPK, NP, PK, NK), organic fertilization (OF), half chemical/organic fertilization (HOF), and no fertilization (control, CK). The results showed that 30 years of repeated organic or chemical N applications significantly stimulated gross rates of N mineralization and autotrophic nitrification compared with CK. In addition, gross rates of N mineralization (except NP) and autotrophic nitrification (except CK, PK) in all treatments were significantly higher in 2019 (30 years) than in 2007 (18 years). However, the immobilization of mineral N decreased significantly (near to zero) after 30 years of repeated N applications compared to CK or the results of 18 years. The highest maize yields were observed in NPK, but they were not significantly different from HOF yields. The OM yields significantly increased with the duration of the experiment and reached values comparable to NPK yields after more than 12 years of repeated N applications. There was a logarithmic positive relationship between maize yields and gross N mineralization rates (p

To ensure global food security, agriculture must increase productivity while reducing environmental impacts associated with chemical nitrogen (N) fertilisation. This necessitates towards more sustainable practices such as recycling organic waste to substitute chemical fertiliser N inputs. However, hitherto how such strategy controls the succession of microbial communities and their relationship with crop yields and environmental impacts have not been comprehensively investigated. We conducted a field experiment with vegetable production in China examining partial substitution (25–50%) of chemical fertiliser with organic forms (pig manure or municipal sludge compost) considering key sustainability metrics: productivity, soil health, environmental impacts and microbial communities. We demonstrate that partial organic substitution improved crop yields, prevented soil acidification and improved soil fertility. Treatments also reduced detrimental environmental impacts with lower N2O emission, N leaching and runoff, likely due to reduced inorganic nitrogen surplus. Microbial communities, including key genes involved in the N cycle, were dynamic and time-dependent in response to partial organic substitution, and were also important in regulating crop yields and environmental impacts. Partial organic substitution increased bacterial diversity and the relative abundance of several specific microbial groups (e.g. Sphingomonadales, Myxococcales, Planctomycetes, and Rhizobiales) involved in N cycling. Additionally, partial organic substitution reduced the number of bacterial ammonia oxidizers and increased the number of denitrifiers, with the proportion of N2O-reducers being more pronounced, suggesting a mechanism for reducing N2O emissions. Comprehensive economic cost-benefit evaluation showed that partial organic substitution increased economic benefit per unit area by 37–46%, and reduced agricultural inputs and environmental impacts per unit product by 22–44%. Among them, 50% substitution of pig manure was the most profitable strategy. The study is crucial to policy-making as it highlights the potential advantages of shifting towards systems balancing chemical and organic fertilisers with economic benefits for farmers, reduced environmental damage and an efficient way for organic waste disposal.

The production of nitrous oxide (N2O) is a widespread trait in fungi and is of interest because denitrifying fungi lack the N2O reductase gene (nosZ) that regulates N2O reduction to nitrogen gas (N2). The adaptive ability of soil fungi is better than that of bacteria in acidic soils. We investigated the N2O reduction potential, described by the N2O product ratio (RN2O), N2O/(N2O+N2), in soils of different types of fields under crop cultivation with different fertilizer inputs and a bare fallow field with no fertilization as a control. The fungi-to-bacteria abundance ratio (RF/B) was negatively correlated (P

Two-dimensional molybdenum disulfide (MoS2) shows a great potential for optoelectronic devices due to its unique electronic, optical, photo-catalytic properties. While the bi-layer MoS2 via direct grown or mechanical exfoliation shows poor photoelectric effect due to its indirect band gap. In this work, we build bi-layer MoS2 via two-step PMMA transfer method, which shows the monolayer Raman characteristics. More importantly, the PL intensity of the built bi-layer MoS2 area shows four-to eight-fold increase compared that of the monolayer MoS2 area, indicating that the bottom monolayer MoS2 plays a role as a substrate and effectively separates the impurities of the SiO2 substrate from the upper monolayer MoS2. We believe that the residue PMMA between monolayers prevents the formation of interlayer coupling and results in the upper monolayer MoS2 suspending in some areas of the twisted bi-layer area. Our results provide a method to enhance the photoluminescence of the monolayer MoS2 by constructing the homogeneous MoS2 structure.

Chemical nitrogen fertilizer application in the peri-urban zone has benefited food supply, but excess nitrogen input has altered multiple ecosystem services and caused an array of ecosystem dis-services that have degraded air and water quality. Using sewage sludge compost and pig manure to partially substitute chemical fertilizer nitrogen may promote sustainable ecosystem services. However, few studies have been conducted to evaluate the values of associate ecosystem services with a unified standard. To comprehensively understand the effect of partial organic substitution on ecosystem services (supporting vegetable production and sequestering soil organic carbon) and ecosystem dis-services (greenhouse gas emissions and reactive nitrogen release), we attempted to evaluate the ecosystem service from the perspective of economic assessment. A field experiment was conducted in a peri-urban zone in eastern China, including the following six treatments at equal total nitrogen application rates: (1) no fertilizer nitrogen applied; (2) 25% sewage sludge compost substitution; (3) 25% pig manure substitution; (4) 50% sewage sludge compost substitution; (5) 50% pig manure substitution and (6) chemical fertilizer nitrogen only. The results showed that partial organic substitution significantly increased annual vegetable yield by 27.8%–35.3% and annual soil organic carbon sequestration rate by 129.2%–213.8%. Moreover, greenhouse gas emissions (methane and nitrous oxide) were significantly decreased by 28.6%–43.2%; nitrogen leaching and runoff were significantly decreased by 39.0%–49.5% and 26.8%–62.0%, respectively; and ammonia volatilization was increased by 2.4%–27.8%. Overall, partial substitution with organic fertilizer decreased total reactive nitrogen losses by 19.9%–39.8% compared with the 100% chemical fertilizer nitrogen treatment. Although additional labor and higher input costs were required, partial organic substitution could obtain a higher net economic benefit of 25198–90670 ¥ ha−1 yr−1 compared with the sole application of chemical fertilizer nitrogen. The results suggest that partial substitution of chemical fertilizer with organic fertilizer can sustain ecosystem services and reduce ecosystem dis-services in the peri-urban zone and increase economic profits for farmers.

The impacts of biochar addition with nitrogen fertilizer (Urea-N) on greenhouse gas (GHG) fluxes and grain yields are not comprehensively understood. Therefore, we designed a field experiment in an intensive rice–wheat cropping system located in the Taihu Lake region of China and measured CH4 and N2O emissions for 2 consecutive years to examine the impacts of biochar combined with N-fertilizer on rice production and GHG flux. Three field experimental treatments were designed: (1) no N-fertilizer application (N0); (2) 270 kg N ha−1 application (N270); and (3) 270 kg N-fertilizer ha−1 plus 25 t ha−1 biochar application (N270 + C). We found that, compared with urea application alone, biochar applied with Urea-N fertilizer increased N use efficiency (NUE) and resulted in more stable growth of rice yield. In addition, biochar addition increased CH4 emissions by 0.5–37.5% on average during the two consecutive rice-growing seasons, and decreased N2O–N loss by ~ 16.7%. During the first growing season, biochar addition did not significantly affect the global warming potential (GWPt) or the greenhouse gas intensity (GHGI) of rice production (p > 0.05). By contrast, during the second rice-growing season, biochar application significantly increased GWPt and GHGI by 28.9% and 18.8%, respectively, mainly because of increased CH4 emissions. Our results suggest that biochar amendment could improve grain yields and NUE, and increased soil GWPt, resulting in a higher potential environmental cost, but that biochar additions enhance exogenous carbon sequestration by the soil, which could offset the increases in GHG emissions.

Current estimates of global indirect N2O emissions are based on a relatively small dataset and remain a major source of uncertainly in the global N2O budget. Nitrogen (N)-enriched groundwater from agricultural fields may act as an important source of indirect N2O emissions as it discharges to adjacent watershed areas. During 2015–2017, dissolved N2O concentrations in groundwater were measured and indirect N2O emission factors (EF5g) calculated under three typical high-N land-use types (vineyard, vegetable field and paddy field) in eastern China. The average dissolved N2O concentrations in groundwater were 58.1 ± 40.4, 18.5 ± 11.5 and 0.72 ± 0.27 μg N L−1 for vineyard, vegetable field and paddy field, respectively. The dissolved N2O was over-saturated and was therefore a net source of N2O to the atmosphere. The indirect N2O emission factors (EF5g) of vineyard (0.0091) and vegetable (0.0092) fields were much higher than the current Intergovernmental Panel on Climate Change (IPCC) default value of 0.0025 which indicated that these land-uses may have led to indirect N2O emissions from the underlying groundwater. In contrast, the EF5g of the paddy field (0.0019) was slightly lower than the default EF5g proposed by IPCC (2006) and contributed minimal indirect N2O emissions to the atmosphere. However, the current IPCC method may have overestimated the contribution of groundwater N2O to the global N cycle because it took residual but not initial groundwater NO3−-N concentration into account when calculating EF5g. Therefore, we proposed the adoption of an improved method for calculating the EF5g and compared it to the current IPCC (2006) method using data from the present study and other published data. The results of the comparison showed that the improved method was more scientifically appropriate measurement for calculating EF5g.

Ammonia (NH3) emission from agricultural sources has contributed significantly to air pollution, soil acidification, water eutrophication, biodiversity loss, and declining human health. Although there are numerous strategies for reducing NH3 emission from agricultural systems, the effectiveness of these measures is highly variable. Furthermore, the integrated assessment of measures to reduce NH3 emission both from livestock production and cropping systems based on animal and crop type is lacking. Therefore, we conducted a global meta-analysis and integrated assessment of measures to reduce NH3 emission from agricultural systems. Most of the studied mitigation strategies were effective in reducing NH3 emission. In the livestock production system, dietary additive, urease inhibitor (UI), manure acidification and deep manure placement have the highest mitigation potential relative to other mitigation strategies, with reduction ranges of 35.1-54.2%, 24.3-68.7%, 88.8-95.0%, and 93.8-99.7%, respectively, relative to the control, while manure storage management could significantly reduce NH3 emission by 70.0-82.1%. In the cropping system, fertilizer source, use of enhanced efficiency fertilizers, and method of field application are most effective for reducingNH3 emission. The use of ammonium nitrate, controlled release fertilizer (CRF), and deep placement of fertilizers could reduce NH3 emission by 88.3, 56.8, and 48.0%, respectively. Choosing a proper fertilizer is critical for decreasing NH3 emission from cropping systems. We conclude that carefully planned and adopted strategies suited for local conditions are promising for minimizing NH3 emission from agricultural systems on a global scale, while possible effects of those mitigation measures on the emission of greenhouse gases should be studied in the future.

A better understanding of gross nitrogen (N) transformation rates in agroforestry systems is crucial for testing the land use management effects on soil N retention. In this study, gross N transformation rates in forest and adjacent agricultural soils in two agroforestry systems, hedgerow and shelterbelt, located near Edmonton, Alberta, Canada were investigated using the 15N labeled technique and a numerical model, FLUAZ. Gross N mineralization rates in the forested land use were higher than that in the agricultural land use for hedgerow and shelterbelt agroforestry system, and the pattern was the same for gross N immobilization rates. However, gross nitrification rates in the forested land use were lower than that in the agricultural land use for both agroforestry systems. The ratios of gross nitrification to ammonium immobilization rates and the ratios of gross N mineralization to immobilization rates in the agricultural land use were higher than that in the forested land use irrespective of the type of agroforestry system studied. Our study suggested that the agricultural land use had a lower potential to conserve N, posing a higher risk of N loss, whereas mineralization and immobilization processes were tightly coupled in the forested land use, leaving less N available for nitrification and subsequent N loss to the environment.

Managing reactive nitrogen (Nr) to achieve a sustainable balance between production of food, feed and fiber, and environmental protection is a grand challenge in the context of an increasingly affluent society. Here, we propose a novel framework for national nitrogen (N) assessments enabling a more consistent comparison of the uses, losses and impacts of Nr between countries, and improvement of Nr management for sustainable development at national and regional scales. This framework includes four key components: national scale N budgets, validation of N fluxes, cost-benefit analysis and Nr management strategies. We identify four critical factors for Nr management to achieve the sustainable development goals: N use efficiency (NUE), Nr recycling ratio (e.g., ratio of livestock excretion applied to cropland), human dietary patterns and food waste ratio. This framework was partly adopted from the European Nitrogen Assessment and now is successfully applied to China, where it contributed to trigger policy interventions toward improvements for future sustainable use of Nr. We demonstrate how other countries can also benefit from the application our framework, in order to include sustainable Nr management under future challenges of growing population, hence contributing to the achievement of some key sustainable development goals (SDGs).

This paper studies the selective maintenance problem for a multi-state system (MSS) performing consecutive production missions with scheduled intermission breaks. To improve the reliability of the system successfully performing the next mission, all maintenance actions need to be carried out during maintenance breaks. However, it may not be feasible to repair all components due to the limited maintenance resources (such as time, costs, and manpower). Hence, a selective maintenance model was established to identify a subset of maintenance actions to perform on the repairable components. We extend the original model in several ways. First, we consider the role of degradation interaction in determining the state transition probability of each component. Back-propagation (BP) neural network is employed to predict the transition matrix since it is not practicable to analyze the degradation processes of all components using the traditional probability model. Second, a selective maintenance optimization model for an MSS is established based on the prediction results of the BP neural network and solved by a genetic algorithm (GA). Finally, an example is illustrated to verify the effectiveness and superiority of the proposed method.

Service processes in modern logistic systems tend to be highly specialized and intellectualized. However, some casual and unexpected behavior may occur, causing specific dynamic interactions among their many constituents. As such, the optimization and modeling of complex problems have become increasingly tough. Besides, technicians typically need to possess appropriate skills that match assigned tasks. Faced with real service scenarios, however, employees inevitably suffer from an increasing level of fatigue attributed to continuous work, resulting in a gradual decrease in the efficiency of workers over time. In this situation, the service time for a given task can no longer be treated as a constant, but instead, it should be treated as dynamic. Moreover, highly skilled technicians are usually paid higher than the junior ones with basic or lower skill level, which introduces new challenges in the optimization of service task schedules' problem. In this paper, we first present the skill vehicle routing problem considering dynamic service times and time-skill-dependent costs, in which the efficiencies of the workers are dynamically affected by their fatigue levels, and the costs, i.e., salaries paid to the employees, are related to skill levels and continuous work time. Furthermore, we develop a comprehensive and general mixed-integer linear programming dynamic-based model to formulate the proposed problem, which is directly solvable by MIP solvers for small-sized problems. We also initiate an iteratively dynamic neighborhood search (IDNS) algorithm that combines iterative partial optimization with dynamic neighborhood search to efficiently solve large-sized problems with near-optimal solutions. The comprehensive computational experiments were performed on the problems of different sizes to test the effectiveness and efficiency of the proposed model and solution approach. Some useful managerial insights were obtained from the computational results that can help decision-makers to determine cost-effective service routes and schedules in complex transportation-related issues.

The low-cost synthesis of high-quality black phosphorus (BP) has always been a challenge. Herein, we selected different mineralizers to synthesize high-crystallinity BP by the chemical vapor transport (CVT) method and demonstrated that the use of Pb instead of Sn can lead to higher purity BP. Residual Sn in Sn-BP was confirmed by X-ray photoelectron spectroscopy (XPS), but no mineralizer impurity was observed in Pb-BP. The performance of FET devices showed that the hole mobility of Pb-BP was significantly higher than that of Sn-BP. On the other hand, the Pb-BP devices exhibited good bipolarity with the highest hole mobility of 523 cm2 V-1 s-1 at room temperature and electron mobility of up to 28 cm2 V-1 s-1.

Nitrated nonylphenols (NNPs) are main metabolites of the endocrine-disrupting nonylphenols in soil, yet their fate is unknown. Here, using four NNP isomers (NNP111, NNP112, NNP65, and NNP38), the degradation pattern of NNPs was investigated in an oxic soil for 266 days. Specifically, NNP111 was 14C-labeled to facilitate investigating its degradation, transformation, and non-extractable residue (NER) formation. NNPs degradation was isomer-specific with the decreasing order of half-life: NNP111 (126 days) > NNP112 (76 days) > NNP65 (14 days) > NNP38 (8.4 days), providing direct evidence of the greater persistence of NNPs in soil than their parent NPs. At the end of the incubation, 8.5 %, 7.3 %, and 39.9 % of 14C-NNP111 was mineralized, transformed to 2-amino-NP111, and formed NERs in active soil, respectively. In contrast, NERs in sterilized soils were significantly lower, amounting to 15.1 % and 17.3 % in autoclaved and γ-irradiated soil, respectively. The majority of the NERs (>70 %) were in humin fraction, in which type I NER was the predominant (>90 %) mode for NER formation. Our results provide comprehensive knowledge on the fate of NNPs in soil, demonstrating that isomer-specific behavior, transformation products of NNPs, and NER formation should be considered when evaluating environmental fate and risks of NNPs.

To reduce the utilization of chemical fertilisers, which cause substantial nitrogen loss and widespread nonpoint source pollution, the application of organic manure has become an increasingly popular alternative in rice agriculture. It plays key roles in improving soil quality and maintaining rice yields, but its integrated impacts on trace gas emissions and heavy metal contents in rice grains remain poorly documented. We conducted a three-year field experiment with two application ratios (25% and 50%) of sewage sludge compost (S) and pig manure compost (P) during the rice season in eastern China. The emissions of methane (CH

Crop residue amendment in conjunction with synthetic nitrogen (N) fertilization is a common agricultural practice that increases soil fertility and crop yield. However, such a practice may also change soil denitrification process. Here, we conducted an incubation experiment with a robotized continuous flow N-2 free incubation system (using helium (He) and oxygen (O-2)1 and measured fluxes of N2O and N, at a high resolution in an intensively managed soil to examine the interaction effect of straw amendment and N fertilization on soil denitrification. Four treatments were set consisting of (a) a nonamended treatment (Control); (b) a Straw treatment (2 g straw kg(-1) dry soil); (c) a KNO3 treatment (KNO3, 15 mM KNO3); and (d) a Straw + KNO3 treatment (2 g straw kg(-1) dry soil and 15 mM KNO3). During the oxic phase (80% He plus 20% 0 2 ) of the experiment (initial 2 days), flux rates of N2O were 0.54 and 0.38 kg N/ha day(-1) in the Control and KNO3 treatments, respectively. Meanwhile, straw amendment triggered N2O fluxes immediately after the onset of treatments, which was more evident in the Straw + KNO3 treatment. During the anoxic phase (100% He), both N2O and N-2 emissions increased in all treatments, with the effect being more pronounced in the Straw and Straw + KNO3 treatments. In line with the observed differences in gas fluxes, the abundances of nirK, nirS, and nosZ genes increased clearly in these treatments. Overall, the mean N2O/(N2O + N-2) ratio (0.69 +/- 0.03) in the Control treatment was significantly lower compared to the KNO3 treatment (18.8%) and higher than the straw-amended soils (31.9% and 17.4% compared to the Straw and Straw + KNO3 treatments, respectively). Taken together, our results suggest straw amendment significantly altered N2O and N-2 fluxes by decreasing the N2O/(N2O + N-2) ratio; however, the effects of straw amendment depended on soil nitrate content.

Biochar may variably impact nitrogen (N) transformation and N-cycle-related microbial activities. Yet the mechanism of biochar amendment on nitrous oxide (N

Numerous studies reporting a transient decrease in soil nitrous oxide (N

Ammonia (NH

The purpose of this study was to evaluate the air-blowing temperature and water storage time on the micro-tensile bond strength (μTBS) of five universal adhesive systems to dentin. The bond strength with two different air-blowing temperatures (60±2oC and 23±2oC) was measured after water storage at 37oC for 24 h and 100 days respectively. The fracture surface on dentin side was observed by scanning electron microscope (SEM). Three-way ANOVA revealed a significant effect of universal system (p

Molybdenum disulfide (MoS

In this study, soil-borne N2, NO, and N2O emissions induced by land use conversion and water management were investigated in intact soil cores under a helium/oxygen atmosphere by a robotized incubation system in combination with the N2O 15N site preference signature and molecular-based microbial analysis. The experiment consisted of five treatments: i) paddy-flooded (PF); ii) orchard-wet (OW, 70% WFPS); iii) orchard-dry (OD, 43% WFPS); iv) vegetable-wet (VW, 70% WFPS); and v) vegetable-dry (VD, 43% WFPS). The vessels of each treatment received 200 mg urea-nitrogen (N) (equivalent to 210 kg of urea-N ha−1), and soil moisture in the OW and VW treatments was adjusted to a higher constant moisture to simulate a scenario after irrigation or rainfall. The results showed that total gaseous N losses during the incubation period were 25.33 ± 0.33 kg N ha−1 in the PF treatment, whereas smaller losses were recorded in the OD and VD treatments (4.28 ± 2.04 and 9.75 ± 3.75 kg N ha−1, respectively). The potential contribution of bacterial denitrification to N2O emissions in the OD and VD treatments was 11.1% and 15.4% higher, respectively, than that in the PF treatment (58.8% ± 0.5%). Furthermore, the corresponding N2O/(N2O + N2) ratio in the OD and VD treatments decreased by 50% and 73.8%, respectively, relative to the ratio in the PF treatment (0.42 ± 0.01). Such changes indicated the crucial role of altered soil properties caused by land use conversion in regulating the production and consumption of N2O. Relative to the normal moisture (dry) condition, enhanced soil moisture increased total gaseous N losses in the orchard and vegetable soils by 386.9% and 67.4%, accompanied by a higher N2O/(N2O + N2) product ratio, but decreased the share of bacterial N2O by 11.1% and 15.4%, respectively. The changes in the abundance and community composition of soil denitrifiers caused by land use conversion from rice paddies to orchards and vegetable fields could partly explain the differences in gaseous N loss therein. These findings highlight the influence of land use conversion on soil gaseous N emissions and demonstrate that increased moisture in upland soils reduced the dominance of bacterial denitrification in N2O production.

The low value of nitrogen use efficiency (NUE) (around 30%) of crop production in China highlights the necessity to adopt reasonable N managements in national scale. After the implementation of ‘National Soil Testing and Formulated Fertilization’ program in 2005, many field experiments have reported an increase of NUE for crop productions in China. This has prompted discussion regarding the extent to which NUE in crop production has been improved. Here, we analyzed the temporal and spatial changes in NUE (crop N uptake/total N input) and cumulative synthetic and non-synthetic N fertilizer recovery efficiency of crop production in China during 1980–2014, and evaluated the relationship between NUE and economic growth (purchasing power parity, PPP) at national and provincial scale. The results showed that the overall NUE of crop production in China clearly increased from 35 to 42% during 2003–2014, and an increase in NUE was further evidenced by increases in cumulative recovery efficiency of both synthetic and non-synthetic N fertilizer. The relationship between NUE and PPP can be described by an environmental Kuznets curve at the national scale, with NUE first decreasing then increasing with PPP. However, this relationship exhibited large spatial variation: 1) In economically developed (e.g., Guangdong and Zhejiang) and undeveloped provinces (e.g., Yunnan and Guizhou), NUE generally decreased and then remained at low levels (20–35%) as PPP increased. 2) In major agricultural provinces with high (e.g., Shandong and Jiangsu) or intermediate levels (e.g., Hunan and Hebei) of economic development, a pronounced increasing trend in NUE with PPP was observed. These results highlight the necessity of developing region-oriented N management strategies to further increase the NUE of crop production in China, particularly in the economically developed and undeveloped provinces.

Effects of antibiotics on the transformation of nitrate and the associated N2O release in paddy fields are obscure. Using soil slurry experiments combined with 15N tracer techniques, the influence of tetracycline and sulfamethazine (applied alone and in combination) on the denitrification, anaerobic ammonium oxidation (anammox), dissimilatory nitrate reduction to ammonium (DNRA) and N2O release rates in the paddy soil were investigated, while genes related to nitrate reduction and antibiotic resistance were quantified to explore the microbial mechanisms behind the antibiotics’ effects. The potential rates of denitrification, anammox, and DNRA were significantly (p 600 μg kg−1 soil dry weight). Our results suggest that the widespread occurrence of antibiotics in paddy soils may pose significant eco-environmental risks (nitrate accumulation and greenhouse effects) by altering nitrate transformation processes.

Human activities have greatly increased the emission of reactive nitrogen (N) to the atmosphere, leading to large increases in N deposition in sensitive ecosystems. However, few have measured both the wet and dry deposition of individual N species in southeast China and their impact on surface water quality. We investigated wet and dry deposition of N, including gaseous NH3, NO2 and HNO3, and particulate NH4+-N and NO3−-N in both the atmosphere and precipitation during a two-year period at three sites in the Taihu Lake region in southeast China. The total N deposition in this region was 64.8 kg N ha−1 yr−1 (range: 59.1–70.5 kg N ha−1 yr−1). On an annual basis, the ratio of reduced to oxidized N deposition was 1.7, suggesting that the reduced form of N dominates N deposition. Of the annual N deposition, 45.5% was deposited via precipitation, with the remaining via dry deposition. The total gaseous and particulate N deposition was 24.9 and 10.4 kg N ha−1 yr−1, respectively. The high N loading in this region has resulted in the reduction of water quality in Taihu Lake. Atmospheric N deposition accounted for 33.3 and 27.5% of the total N loading in Taihu Lake and in water bodies in the region, respectively. We conclude that dry deposition of N is one of the most important sources of surface water pollution and should be taken into account when developing strategies for mitigating water pollution.

Previous studies of long-term manure applications in paddy soil mostly focused on the effects on denitrification, occurrence of antibiotics and antibiotic resistance genes (ARGs) without considering the effects on anaerobic ammonium oxidation (anammox). Here, we investigated the potential rates of anammox and denitrification, occurrence of antibiotics and AGRs in response to three fertilization regimes (C, no fertilizer; N, mineral fertilizer; and NM, N plus pig manure) in six long-term paddy experiment sites across China. The potential rates of anammox (0.11-3.64 nmol N g-1 h-1) and denitrification (1.5-29.05 nmol N g-1 h-1) were correlated with the abundance of anammox genes (hzsB) and denitrification functional genes (narG, nirK, nirS and nosZ), respectively. The anammox and denitrification rates were affected by soil organic carbon (SOC) and significantly (p < 0.05) increased in NM treatments relative to those in N treatments. Although pig manure application increased antibiotic concentrations and abundance of ARGs compared with N treatments, the increased antibiotics did not directly affect the anammox and denitrification rates. Our results suggested that long-term pig manure application significantly increased antibiotic concentrations, abundance of ARGs, and rates of anammox and denitrification, and that the effects of pig manure-derived antibiotics on anammox and denitrification were marginal. This is the first report that investigates the effects of long-term pig manure application on anammox in paddy soils. More attention should be paid to the potential ecological risk of increased ARGs caused by pig manure application in paddy soils.

Rice cultivation has long been known as one of the dominant anthropogenic contributors to methane (CH4) emissions, yet there is still uncertainty when estimating its emissions at the global or regional scale. An increasing number of rice field measurements have been conducted globally, which allow us to reassess the major variables controlling CH4 emissions and develop region- and country-specific emission factors (EFs). The results of our statistical analysis show that the CH4 flux from rice fields was closely related to organic amendments, the water regime during and before the rice-growing season, soil properties and agroecological conditions. The average CH4 fluxes from fields with single and multiple drainage were 71 % and 55 % that of continuously flooded rice fields. The CH4 flux from fields that were flooded in the previous season were 2.4 and 2.7 times that of fields previously drained for a short and long season, respectively. Rice straw applied at 6 t ha−1 in the preseason can decrease CH4 emissions by half when compared to that applied shortly before rice transplanting. The global default EF was estimated to be 1.19 kg CH4 ha−1 day−1 with a 95 % confidence interval of 0.80 to 1.76 kg CH4 ha−1 day−1 for continuously flooded rice fields without organic amendment and with a preseason water status of short drainage. The lower EFs were found in countries from South Asia (0.85 kg CH4 ha−1 day−1) and North America (0.65 kg CH4 ha−1 day−1) relative to other regions, indicative of geographical variations at sub-regional and country levels. In conclusion, these findings can provide a sound basis for developing national inventories and mitigation strategies of CH4 emission from rice fields.