Publications by authors named "Xiaoyuan Yan"

57 Publications

Nitrogen cascade in the agriculture-food-environment system of the Yangtze Delta, 1998-2018.

Sci Total Environ 2021 Sep 7;787:147442. Epub 2021 May 7.

Center for Material Cycles and Waste Management Research, National Institute for Environmental Studies, Tsukuba 305-8506, Japan.

The nitrogen (N) cascade in rural areas of Changshu County should be measured and evaluated due to the large increase in anthropogenic disturbances in China's Yangtze Delta. Here, we developed a village-scale N flow model using Changshu County and its towns as a case study. The model included four subsystems and was used to describe the driving forces behind the N cascade from agricultural food production and household consumption to the environment (agriculture-food-environment) system. It was found that from 1998 to 2018 the N input increased from 274.63 to 848.65 kg N ha. The cropland N use efficiency (NUEc) decreased by 10.35%, whereas the livestock feed N use efficiency (NUEa) increased by 51.84%. A relatively lower NUE, with a higher N input, was found in Shajiabang Town, which was attributed to hairy crab farming. Changes in dietary patterns led to the food N cost (FNC) being in the range of 4.59-7.74 kg kg. Over the past two decades, the N losses from the agriculture-food-environment system decreased by 45.40% from 12,436.60 t N yr (1998). The contribution of the croplands, livestock-breeding, and household consumption to the N losses were 32.44%, 37.78%, and 29.78%, respectively. About 62.83% of the total N losses entered the water environment. Nitrogen emissions from the croplands accounted for 63.21% of the N losses into the atmosphere. Nitrogen oxide (NO) emissions accounted for 38.50% of the gas emissions, followed by NH (28.36%) and NO (2.81%). The total N losses decreased annually but losses to the water environment increased by 5.10% from 60.16% (1998). The contribution of food production to the total N loss displayed a decreasing trend, while that of food consumption exhibited an increasing trend. Population growth and increased volumes of domestic waste in the Changsu area were the main driving forces for the increased contribution of household food consumption. The significant decline in cropland area and increase in built-up and heavily trafficked areas indicated an overall increase in anthropogenic disturbances, stimulating the N cascade in the Yangtze Delta from 1998 to 2018.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147442DOI Listing
September 2021

Biochar amendment mitigated NO emissions from paddy field during the wheat growing season.

Environ Pollut 2021 Jul 27;281:117026. Epub 2021 Mar 27.

Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China. Electronic address:

Biochar may variably impact nitrogen (N) transformation and N-cycle-related microbial activities. Yet the mechanism of biochar amendment on nitrous oxide (NO) emissions from agricultural ecosystems remains unclear. Based on a 6-year long-term biochar amendment experiment, we applied a dual isotope (N-O) labeling technique with tracing transcriptional genes to differentiate the contribution of nitrifier nitrification (NN), nitrifier denitrification (ND), nitrification-coupled denitrification (NCD) and heterotrophic denitrification (HD) pathway to NO production. Then the field experiment provided quantitative data on dynamic NO emissions, soil mineral N and key functional marker gene abundances during the wheat growing season. By using N-O isotope, biochar decreased NO emission derived from ND (by 45-94%), HD (by 35-46%) and NCD (by 30-64%) compared to the values under N application. Biochar increased the relative contribution of NN to total NO production as evidenced by the increase in ammonia-oxidizing bacteria, but did not influence the cumulative NN-derived NO. The field experiment found that the majority of the NO emissions peaked following fertilization, in parallel with soil NH and nitrite dynamics. Soil NO emissions during the wheat growing stage were effectively decreased (by 38-48%) by biochar amendment. Based on the correlation analyses and random forest analysis in both microcosm and field experiments, the decrease in nitrite concentration (by 62-65%) and increase in NO consumption were mainly responsible for net NO mitigation, as evidenced by the decrease in the ratios of nitrite reductase genes/transcripts (nirS, nirK and fungal nirK) and NO reductase gene/transcripts (nosZI and nosZII). Based on the extrapolation from microcosm to field, biochar significantly mitigated NO emissions by weakening the ND processes, since NCD and HD contributed little during the NO emission "peaks" following urea fertilization. Therefore, emphasis should be put on the ND process and nitrite accumulation during NO emission peaks and extrapolated to all agroecosystems.
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http://dx.doi.org/10.1016/j.envpol.2021.117026DOI Listing
July 2021

Self-powered and high responsivity photodetector based on a n-Si/p-GaTe heterojunction.

Nanotechnology 2021 Feb 26. Epub 2021 Feb 26.

Department of Physics, Zhejiang University, Hangzhou 310027, Hangzhou, CHINA.

Heterojunction integrated by two-dimensional (2D)/three-dimensional (3D) materials has shown great potential applications in optoelectronic devices because of its fast response speed, high specific detectivity and broad spectral response. In this work, the vertical n-Si/p-GaTe heterojunction has been designed and fabricated, which shows a high responsivity up to 5.73 A/W and a fast response time of 20 μs at zero bias benifitting from the high efficiency of light absorption, internal photocurrent gain and strong built-in electrical field. A specific detectivity of 1012 Jones and a broad spectral response ranging from 300 nm to 1100 nm can also be achieved. This work provides an alternative strategy for high-performance self-powered optoelectronic devices.
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http://dx.doi.org/10.1088/1361-6528/abea39DOI Listing
February 2021

The effect of long-term biochar amendment on NO emissions: Experiments with N-O isotopes combined with specific inhibition approaches.

Sci Total Environ 2021 May 14;769:144533. Epub 2021 Jan 14.

Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China. Electronic address:

Numerous studies reporting a transient decrease in soil nitrous oxide (NO) emissions after biochar amendment have mainly used short-term experiments. Thus, long-term field trials are needed to clarify the actual impact of biochar on NO emissions and the underlying mechanisms. To address this, both a NO labeling technique and gene analyses were applied to investigate how NO production pathways and microbial mediation were affected by long term biochar amendment in field. Then, 1-octyne and 2-phenyl l-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) were used in combination with potassium chlorate to evaluate the relative contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to potential ammonia oxidation (PAO) and the associated NO production. Acidic and alkaline greenhouse vegetable soils that had each received two separate treatments were collected (control, no biochar amendment; biochar, biochar amended in the field after 2 or 7 years). The results showed that biochar decreased NO emissions by 48% in acidic soils and by 22% in alkaline soils compared to those in control. These results were explained by decreases in nitrifier denitrification- (by 74%) and heterotrophic denitrification-derived NO production (by 58%), as further evidenced by a decrease in NO (by 87%) and the (nirK+nirS+fungal nirK):(nosZ-I + nosZ-II) ratio (by 5%) in both greenhouse vegetable soils. However, biochar increased nitrifier nitrification-derived NO in both soils because of increases in pH and PAO, which were attributed to an increased abundance of AOB rather than AOA. The contribution of AOB to PAO (or NO) exceeded 69% (or 68%) of the total in acidic soil and 88% (or 85%) of the total in alkaline soil after biochar amendment. Our findings demonstrated that the mitigation of NO by biochar is linked to specific NO production pathways.
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http://dx.doi.org/10.1016/j.scitotenv.2020.144533DOI Listing
May 2021

Changes of δN values during the volatilization process after applying urea on soil.

Environ Pollut 2021 Feb 7;270:116204. Epub 2020 Dec 7.

State Key Laboratory of Soil and Sustainable Agriculture, Changshu National Agro-Ecosystem Observation and Research Station, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China. Electronic address:

Ammonia (NH) volatilized from soils plays an important role in N cycle and air pollution, thus it is important to trace the emission source and predict source contributions to development strategies mitigating the environmental harmful of soil NH volatilization. The measurements of N natural abundance (δN) could be used as a complementary tool for apportioning emissions sources to resolve the contribution of multiple NH emission sources to air NH pollution. However, information of the changes of δN-NH values during the whole volatilization process under different N application rates are currently lacking. Hence, to fill this gap, we conducted a 15-day incubation experiment included different urea-N application rates to determine δN values of NH during volatilization process. Results showed that volatilization process depleted N in NH. The average δN value of NH volatilized from the 0, 20, 180, and 360 kg N ha treatment was -16.2 ± 7.3‰, -26.0 ± 5.4‰, -34.8 ± 4.8‰, and -40.6 ± 5.7‰. Overall, δN-NH values ranged from -46.0‰ to -4.7‰ during the whole volatilization process, with lower in higher urea-N application treatments than those in control. δN-NH values during the NH volatilization process were much lower than those of the primary sources, soil (-3.4 ± 0.1‰) and urea (-3.6 ± 0.1‰). Therefore, large isotopic fractionation may occur during soil volatilization process. Moreover, negative relationships between soil NH-N and NH volatilization rate and δN-NH values were observed in this study. Our results could be used as evidences of NH source apportionments and N cycle.
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http://dx.doi.org/10.1016/j.envpol.2020.116204DOI Listing
February 2021

Effect of air-blowing temperature and water storage time on the bond strength of five universal adhesive systems to dentin.

Dent Mater J 2021 Jan 28;40(1):116-122. Epub 2020 Aug 28.

Department of Dental Materials Science, School and Hospital of Stomatology, China Medical University, Liaoning Provincial Key Laboratory of Oral Disease.

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<0.001) and air-blowing temperature (p<0.001) on bond strength to dentin except water-storage time (p=0.145). The interaction within three factors was significantly different (p<0.001). It could be concluded that the μTBS of universal systems to dentin was material-depended. The higher and more stable bonding performance of universal systems on dentin could be achieved by air-blowing at 60±2ºC temperature. In addition, the quantity of voids in the adhesive layer of aceton-based universal adhesive was significantly reduced by higher temperature.
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http://dx.doi.org/10.4012/dmj.2019-280DOI Listing
January 2021

N-type doping of black phosphorus single crystal by tellurium.

Nanotechnology 2020 Jul 22;31(31):315605. Epub 2020 Apr 22.

Department of Physics, Zhejiang Province Key Laboratory of Quantum Technology and Device & State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China.

Black phosphorus has many potential applications in optoelectronic devices because of its unique properties. Adjusting its performance by doping is an important issue of research. In this paper, we synthesized high-quality Te-doped crystals by the chemical vapor transport method. Tellurium doping with an atomic ratio of 0.1% was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and energy dispersive X-ray analysis. The performance of field effect transistors devices shows that the hole mobility of Te-doped black phosphorous (BP) is significantly improved compared with that of undoped-BP. The highest hole mobility at room temperature is 719 cm V s, and the electron mobility is 63 cm V s. Te-doped BP field effect transistors show an obvious bipolar behavior.
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http://dx.doi.org/10.1088/1361-6528/ab8c08DOI Listing
July 2020

P-type Doping in Large-Area Monolayer MoS by Chemical Vapor Deposition.

ACS Appl Mater Interfaces 2020 Feb 28;12(5):6276-6282. Epub 2020 Jan 28.

Department of Physics, Zhejiang Province Key Laboratory of Quantum Technology and Device & State Key Laboratory of Silicon Materials , Zhejiang University , Hangzhou 310027 , P. R. China.

Molybdenum disulfide (MoS) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS 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 MoS by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses n-type conductivity in MoS 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.
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http://dx.doi.org/10.1021/acsami.9b19864DOI Listing
February 2020

Simultaneous quantification of N , NH and N O emissions from a flooded paddy field under different N fertilization regimes.

Glob Chang Biol 2019 Dec 12. Epub 2019 Dec 12.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China.

Gaseous nitrogen (N) emissions, especially emissions of dinitrogen (N ) and ammonia (NH ), have long been considered as the major pathways of N loss from flooded rice paddies. However, no studies have simultaneously evaluated the overall response of gaseous N losses to improved N fertilization practices due to the difficulties to directly measure N emissions from paddy soils. We simultaneously quantified emissions of N (using membrane inlet mass spectrometry), NH and nitrous oxide (N O) from a flooded paddy field in southern China over an entire rice-growing season. Our field experiment included three treatments: a control treatment (no N addition) and two N fertilizer (220 kg N/ha) application methods, the traditional surface application of N fertilizer and the incorporation of N fertilizer into the soil. Our results show that over the rice-growing season, the cumulative gaseous N losses from the surface application treatment accounted for 13.5% (N ), 19.1% (NH ), 0.2% (N O) and 32.8% (total gaseous N loss) of the applied N fertilizer. Compared with the surface application treatment, the incorporation of N fertilizer into the soil decreased the emissions of NH , N and N O by 14.2%, 13.3% and 42.5%, respectively. Overall, the incorporation of N fertilizer into the soil significantly reduced the total gaseous N loss by 13.8%, improved the fertilizer N use efficiency by 14.4%, increased the rice yield by 13.9% and reduced the gaseous N loss intensity (gaseous N loss/rice yield) by 24.3%. Our results indicate that the incorporation of N fertilizer into the soil is an effective agricultural management practice in ensuring food security and environmental sustainability in flooded paddy ecosystems.
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http://dx.doi.org/10.1111/gcb.14958DOI Listing
December 2019

Design of a two-layer structure to significantly improve the performance of zinc oxide resistive memory.

Nanotechnology 2020 Mar 20;31(11):115209. Epub 2019 Nov 20.

Department of Physics, Zhejiang Province Key Laboratory of Quantum Technology and Device & State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China.

Resistive random access memory (RRAM) is considered to be one of the important candidates for the next generation of memory devices. Zinc oxide resistive memory has also been studied for many years, but there are still some controversial topics and problems. Herein, an unusual resistance state has been observed in devices following the measurement and analysis of ZnO resistive memories with different thicknesses, a middle resistance state was speculated to explain the instability of ZnO RRAM. According to this speculation, a two-layer structure ZnO RRAM has been designed to significantly increase the device performance with the introduction of an HfO layer and the enhancement has also been explained based on the results of first-principles calculations.
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http://dx.doi.org/10.1088/1361-6528/ab597bDOI Listing
March 2020

Biochar-enriched soil mitigated NO and NO emissions similarly as fresh biochar for wheat production.

Sci Total Environ 2020 Jan 2;701:134943. Epub 2019 Nov 2.

Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China. Electronic address:

Biochar amendment has been recommended as a potential strategy to mitigate nitrous oxide (NO) and nitric oxide (NO) emissions for wheat production, but its mechanism and effective duration are not well understood. The 1-octyne and 2-pheny l-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) in combination with potassium chlorate were used to evaluate the relative contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to potential ammonia oxidation (PAO) and NO and NO production as affected by biochar. Acidic and alkaline soils were collected during wheat-growing season, and four treatments were installed in each soil type: CK, urea alone; BE, biochar-enriched soil for 2-6 years; FB, fresh biochar added to CK; and AB, aged biochar added to CK. The results showed that octyne and PTIO efficiently assessed AOB and AOA activities in soil incubation. The AOB-driven PAO in acidic soil was largely enhanced by increased soil pH in BE and FB treatments, whereas AOA-driven PAO was not. And the contribution of AOB to PAO exceeded 80% in alkaline soil. The NO and NO production were positively correlated with PAO in both soils. BE treatment decreased the direct NO and NO production in alkaline soil, while both BE and FB treatments decreased the NO and NO yields in acidic soil, indicating that biochar mitigated soil NO and NO emissions for wheat production. The lack of differences between AB and CK treatments indicated that aged biochar lost its initial effects on PAO, while the biochar-enriched soil amended with biochar years earlier still functioned similarly as fresh biochar.
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http://dx.doi.org/10.1016/j.scitotenv.2019.134943DOI Listing
January 2020

Improvement in the quality of black phosphorus by selecting a mineralizer.

Nanoscale 2019 Nov 15;11(42):20081-20089. Epub 2019 Oct 15.

Department of Physics, Zhejiang Province Key Laboratory of Quantum Technology and Devices & State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, P. R. China. and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China.

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 cm V s at room temperature and electron mobility of up to 28 cm V s.
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http://dx.doi.org/10.1039/c9nr06583kDOI Listing
November 2019

Effects of triclosan and triclocarban on denitrification and NO emissions in paddy soil.

Sci Total Environ 2019 Dec 7;695:133782. Epub 2019 Aug 7.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address:

Triclosan (TCS) and triclocarban (TCC) are two common antimicrobial compounds, which are widely used as ingredients in pharmaceuticals and personal care products. They occur ubiquitously in soil due to biosolid application as agricultural fertilizers, but their influence on microbially mediated soil biogeochemical processes is poorly understood. We tested the effects of varying concentrations of TCS and TCC applied both individually and together on denitrification and NO emissions in paddy soil. We also quantified denitrification functional gene abundances by q-PCR to elucidate the microbial mechanisms of TCS and TCC's effects. Our results showed that TCS and TCC exposure both individually and together significantly (p < 0.05) inhibited denitrification (7.0-36.7%) and NO emissions (15.4-86.4%) except for the 0.01 mg kg TCC treatment in which denitrification was slightly but significantly (p < 0.05) stimulated. The inhibitory effects of TCS and TCC exposure were mainly attributed to their negative net effects on denitrifying bacteria as suggested by the decrease in abundances of 16S rRNA, narG, nirK and clade I nosZ genes in the TCS and TCC treatments. Overall, we found that TCS and TCC exposure in paddy soil could substantially alter nitrogen cycling in rice paddy ecosystems by inhibiting denitrification and NO emissions. These effects should be taken into consideration when evaluating the environmental impacts of TCS and TCC.
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http://dx.doi.org/10.1016/j.scitotenv.2019.133782DOI Listing
December 2019

Influence of the geophagous earthworm Aporrectodea sp. on fate of bisphenol A and a branched 4-nonylphenol isomer in soil.

Sci Total Environ 2019 Nov 23;693:133574. Epub 2019 Jul 23.

State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163 Xianlin Avenue, 210046 Nanjing, China. Electronic address:

Large amounts of endocrine disrupting chemicals (EDCs) including bisphenol A (BPA) and nonylphenol (NP) are released into the soil due to the application of biosolids. Earthworms are the predominant biomass in many terrestrial ecosystems and profoundly influence the physico-chemical and biological properties of soils. However, information about the effects of earthworm activities on the behaviors of EDCs in soil is still limited. Here, the effects of earthworms on mineralization, degradation, and bound residue formation of BPA and NP were investigated using the C tracer technique. The results showed that earthworms did not affect mineralization of BPA, but significantly inhibited bound residue formation of BPA and changed the size distribution of BPA residues within humic substances. Regarding NP, earthworms significantly inhibited mineralization and bound residue formation, and thus significantly promoted the degradation of NP and NP's metabolites in soil. After nine days of incubation, 75% and 46% of the initially applied C-BPA and C-NP were already present in bound residues, respectively, indicating that the major route of degradation of BPA and NP in soil was bound-residue formation. Among total C-BPA or C-NP residues accumulated in earthworms, bound residues were also predominant (>50%), implying that risk assessment of EDCs based on their concentrations of free form in earthworms might be significantly underestimated. Taken together, our results suggest that fate of EDCs in soil not only depended on their physico-chemical properties but also was intensively affected by earthworm activities, underlining that effects of earthworms should be considered when evaluating environmental behavior and potential risk of EDCs in soil.
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http://dx.doi.org/10.1016/j.scitotenv.2019.07.380DOI Listing
November 2019

Variable responses of nitrification and denitrification in a paddy soil to long-term biochar amendment and short-term biochar addition.

Chemosphere 2019 Nov 13;234:558-567. Epub 2019 Jun 13.

State Key Laboratory of Soil and Sustainable Agriculture, Changshu National Agro-Ecosystem Observation and Research Station, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.

Biochar-mediated change in soil N transformations has gained much attention. Biochar properties undergo changes through ageing process that may impact variably on N cycling, yet the degree to which soil N transformations may be impacted by biochar ageing process on long-time scale remains unclear. Here, we compared the effects on nitrification, denitrification and N/NO gas flux of short-term fresh biochar addition with long-term biochar amendment over six consecutive years in a paddy soil under identical amounts of soil organic C contents. We found that short-term treatments elicited a stronger effect on nitrification than long-term treatments, due to more positive effects on soil pH and ammonia monooxygenase gene (amoA) abundance of ammonia oxidizing bacterial (AOB). However, there were contrasting effects on soil denitrification and total N gas loss for two types of biochar addition, where the long-term treatments limited availability of C and N, and decreased net NO reduction and total N gas (NO + N) losses by up to 55.5% and 25%. Short-term biochar addition increased dissolved organic C, nutrient content and soil pH, enhanced net NO reduction by 88.7%, also reduced the ratio of nitrite reductase genes (nirS and nirK) and nitrous oxide reductase gene (nosZ) and NO emissions, but increased total N gas loss by 0.2-1.2 times. Our study quantified the differences in nitrification and denitrification capacity in response to short-term biochar addition and long-term biochar amendment and bridged the knowledge-gaps of fresh and aged biochar-mediated N transformation.
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http://dx.doi.org/10.1016/j.chemosphere.2019.06.038DOI Listing
November 2019

HfO-passivated black phosphorus field effect transistor with long-termed stability and enhanced current on/off ratio.

Nanotechnology 2019 Aug 8;30(34):345208. Epub 2019 May 8.

Department of Physics, Zhejiang Province Key Laboratory of Quantum Technology and Devices & State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China.

Enhanced on/off ratio, obvious threshold voltage left shift, newly emerging bipolar field effect performance and most importantly, excellent stability in ambient condition have been reported for the HfO-passivated black phosphorus field effect transistors . Both Raman spectra and x-ray photoelectron spectroscopy (XPS) show a thickness reduction effect after HfO passivation, XPS further demonstrates that the formation of P-Hf and P-O chemical bonds contributes to the thinning of layered black phosphorus (BP), in which P-Hf bonds also provide chemical protection for BP flakes from degradation. Atomic force microscopy measures the thickness of the passivation layer and also verifies the stability of the passivated BP flakes.
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http://dx.doi.org/10.1088/1361-6528/ab1ffeDOI Listing
August 2019

Indirect NO emissions from groundwater under high nitrogen-load farmland in eastern China.

Environ Pollut 2019 May 13;248:238-246. Epub 2019 Feb 13.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Changshu Agro-ecological Experimental Station, Chinese Academy of Sciences, Changshu, 215555, China. Electronic address:

Current estimates of global indirect NO emissions are based on a relatively small dataset and remain a major source of uncertainly in the global NO budget. Nitrogen (N)-enriched groundwater from agricultural fields may act as an important source of indirect NO emissions as it discharges to adjacent watershed areas. During 2015-2017, dissolved NO concentrations in groundwater were measured and indirect NO emission factors (EF) calculated under three typical high-N land-use types (vineyard, vegetable field and paddy field) in eastern China. The average dissolved NO concentrations in groundwater were 58.1 ± 40.4, 18.5 ± 11.5 and 0.72 ± 0.27  μg N L for vineyard, vegetable field and paddy field, respectively. The dissolved NO was over-saturated and was therefore a net source of NO to the atmosphere. The indirect NO emission factors (EF) 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 NO emissions from the underlying groundwater. In contrast, the EF of the paddy field (0.0019) was slightly lower than the default EF proposed by IPCC (2006) and contributed minimal indirect NO emissions to the atmosphere. However, the current IPCC method may have overestimated the contribution of groundwater NO to the global N cycle because it took residual but not initial groundwater NO-N concentration into account when calculating EF. Therefore, we proposed the adoption of an improved method for calculating the EF 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 EF.
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http://dx.doi.org/10.1016/j.envpol.2019.02.027DOI Listing
May 2019

Toward a Generic Analytical Framework for Sustainable Nitrogen Management: Application for China.

Environ Sci Technol 2019 02 28;53(3):1109-1118. Epub 2019 Jan 28.

School of Agriculture and Food , The University of Melbourne , Melbourne , Victoria 3010 , Australia.

Managing reactive nitrogen (N) 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 N between countries, and improvement of N 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 N management strategies. We identify four critical factors for N management to achieve the sustainable development goals: N use efficiency (NUE), N 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 N. We demonstrate how other countries can also benefit from the application our framework, in order to include sustainable N management under future challenges of growing population, hence contributing to the achievement of some key sustainable development goals (SDGs).
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http://dx.doi.org/10.1021/acs.est.8b06370DOI Listing
February 2019

Overestimation of NO mitigation potential by water management in rice paddy fields.

Proc Natl Acad Sci U S A 2018 11 16;115(48):E11204-E11205. Epub 2018 Nov 16.

Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, Tsukuba, Ibaraki 305-8604, Japan.

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http://dx.doi.org/10.1073/pnas.1816208115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6275473PMC
November 2018

Potential for mitigating global agricultural ammonia emission: A meta-analysis.

Environ Pollut 2019 Feb 5;245:141-148. Epub 2018 Nov 5.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China. Electronic address:

Ammonia (NH) 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 NH emission from agricultural systems, the effectiveness of these measures is highly variable. Furthermore, the integrated assessment of measures to reduce NH 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 NH emission from agricultural systems. Most of the studied mitigation strategies were effective in reducing NH 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 NH 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 reducingNH emission. The use of ammonium nitrate, controlled release fertilizer (CRF), and deep placement of fertilizers could reduce NH emission by 88.3, 56.8, and 48.0%, respectively. Choosing a proper fertilizer is critical for decreasing NH emission from cropping systems. We conclude that carefully planned and adopted strategies suited for local conditions are promising for minimizing NH 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.
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http://dx.doi.org/10.1016/j.envpol.2018.10.124DOI Listing
February 2019

Effects of fertilizer application schemes and soil environmental factors on nitrous oxide emission fluxes in a rice-wheat cropping system, east China.

PLoS One 2018 14;13(8):e0202016. Epub 2018 Aug 14.

School of Resources and Environment, Anhui Agricultural University, Hefei, China.

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with agricultural soils representing its largest anthropogenic source. However, the mechanisms involved in the N2O emission and factors affecting N2O emission fluxes in response to various nitrogenous fertilizer applications remain uncertain. We conducted a four-year (2012-2015) field experiment to assess how fertilization scheme impacts N2O emissions from a rice-wheat cropping system in eastern China. The fertilizer treatments included Control (CK), Conventional fertilizer (CF), CF with shallow-irrigation (CF+SI), CF with deep-irrigation system (CF+DI), Optimized fertilizer (OF), OF with Urease inhibitor (OF+UI), OF with conservation tillage (OF+CT) and Slow-release fertilizer (SRF). N2O emissions were measured by a closed static chamber method. N2O emission fluxes ranged from 0.61 μg m-2 h-1 to 1707 μg m-2 h-1, indicating a significant impact of nitrogen fertilizer and cropping type on N2O emissions. The highest crop yields for wheat (3515-3667 kg ha-1) and rice (8633-8990 kg ha-1) were observed under the SRF and OF+UI treatments with significant reduction in N2O emissions by 16.94-21.20% and 5.55-7.93%, respectively. Our findings suggest that the SRF and OF+UI treatments can be effective in achieving maximum crop yield and lowering N2O emissions for the rice-wheat cropping system in eastern China.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0202016PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6091932PMC
January 2019

Tetracycline and sulfamethazine alter dissimilatory nitrate reduction processes and increase NO release in rice fields.

Environ Pollut 2018 Nov 17;242(Pt A):788-796. Epub 2018 Jul 17.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address:

Effects of antibiotics on the transformation of nitrate and the associated NO release in paddy fields are obscure. Using soil slurry experiments combined with N 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 NO 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 < 0.05) reduced, which were mainly attributed to the inhibitory effects of the antibiotics on nitrate-reducing microbes. However, the NO release rates were significantly (p < 0.05) stimulated by the antibiotic treatments (0.6-6000 μg kg soil dry weight), which were caused by the different inhibition effects of antibiotics on NO production and NO reduction as suggest by the changes in abundance of nirS (nitrite reduction step) and nosZ (NO reduction to N step) genes. Antibiotic resistance gene (tetA, tetG, sulI, and sulIII) abundances were significantly (p < 0.05) increased under high antibiotic exposure concentrations (>600 μg kg 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.
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http://dx.doi.org/10.1016/j.envpol.2018.07.061DOI Listing
November 2018

Fabrication of controllably variable sub-100  nm gaps in silver nanowires by photothermal-induced stress.

Opt Lett 2018 May;43(10):2422-2425

A technique to fabricate nanogaps with controllably variable gap width in silver (Ag) nanowires (NWs) by photothermal-induced stress utilizing a focused continuous-wave laser (532 nm) is presented. For the case of an Ag NW on gold thin film, a gap width starting from ∼20  nm is achieved with a critical minimum power (CMP) of about 160 mW, whereas in the case of an Ag NW placed on top of a zinc oxide NW, the attained gap width is as small as a few nm (<10  nm) with a CMP of only ∼100  mW. In both cases, the CMP is much lower as compared to the required CMP (∼280  mW) for an Ag NW placed on a bare silica substrate. The photothermal-induced stress combined with Rayleigh instability, melting, and sublimation of Ag aids in breaking the Ag NW. In particular, the former one plays a key role in attaining an extremely narrow gap. This technique to fabricate sub-100 nm nanogaps in metal NWs can be extensively implemented in fabrication and maintenance of nanomechanical, nanoplasmonic, and nanoelectronic devices.
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http://dx.doi.org/10.1364/OL.43.002422DOI Listing
May 2018

Effects of long-term pig manure application on antibiotics, abundance of antibiotic resistance genes (ARGs), anammox and denitrification rates in paddy soils.

Environ Pollut 2018 Sep 9;240:368-377. Epub 2018 May 9.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address:

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 h) and denitrification (1.5-29.05 nmol N g h) 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.
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http://dx.doi.org/10.1016/j.envpol.2018.04.135DOI Listing
September 2018

Determining δN-NO values in soil, water, and air samples by chemical methods.

Environ Monit Assess 2018 May 10;190(6):341. Epub 2018 May 10.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing, 210008, People's Republic of China.

Soil, water, and air NO pollution is a major environmental problem worldwide. Stable isotope analysis can assess the origin of NO because different NO sources carry different isotope signatures. Hence, using appropriate chemical methods to determine the δN-NO values in different samples is important to improve our understanding of the N-NO pollution and take possible strategies to manage it. Two modified chemical methods, the cadmium-sodium azide method and the VCl-sodium azide method, were used to establish a comprehensive inventory of δN-NO values associated with major NO fluxes by the conversion of NO into NO. Precision and limit of detection values demonstrated the robustness of these quantitative techniques for measuring δN-NO. The standard deviations of the δN-NO values were 0.35 and 0.34‰ for the cadmium-sodium azide and VCl-sodium azide methods. The mean δN-NO values of river water, soil extracts, and summer rain were 8.9 ± 3.3, 3.5 ± 3.5, and 3.3 ± 2.1‰, respectively. The δN-NO values of low concentration samples collected from coal-fired power plants, motor vehicles, and gaseous HNO was 20.3 ± 4.3, 5.6 ± 2.78, and 5.7 ± 3.6‰, respectively. There was a good correlation between the δN-NO compositions of standards and samples, which demonstrates that these chemical reactions can be used successfully to assess δN-NO values in the environment.
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http://dx.doi.org/10.1007/s10661-018-6712-5DOI Listing
May 2018

Detection and attribution of nitrogen runoff trend in China's croplands.

Environ Pollut 2018 Mar 21;234:270-278. Epub 2017 Dec 21.

Sino-France Institute of Earth Systems Science, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, PR China.

Reliable detection and attribution of changes in nitrogen (N) runoff from croplands are essential for designing efficient, sustainable N management strategies for future. Despite the recognition that excess N runoff poses a risk of aquatic eutrophication, large-scale, spatially detailed N runoff trends and their drivers remain poorly understood in China. Based on data comprising 535 site-years from 100 sites across China's croplands, we developed a data-driven upscaling model and a new simplified attribution approach to detect and attribute N runoff trends during the period of 1990-2012. Our results show that N runoff has increased by 46% for rice paddy fields and 31% for upland areas since 1990. However, we acknowledge that the upscaling model is subject to large uncertainties (20% and 40% as coefficient of variation of N runoff, respectively). At national scale, increased fertilizer application was identified as the most likely driver of the N runoff trend, while decreased irrigation levels offset to some extent the impact of fertilization increases. In southern China, the increasing trend of upland N runoff can be attributed to the growth in N runoff rates. Our results suggested that increased SOM led to the N runoff rate growth for uplands, but led to a decline for rice paddy fields. In combination, these results imply that improving management approaches for both N fertilizer use and irrigation is urgently required for mitigating agricultural N runoff in China.
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http://dx.doi.org/10.1016/j.envpol.2017.11.052DOI Listing
March 2018

Metal-assisted exfoliation of few-layer black phosphorus with high yield.

Chem Commun (Camb) 2018 Jan;54(6):595-598

Department of Physics & State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, People's Republic of China.

We introduce a metal-assisted exfoliation method to produce few-layer black phosphorus with the lateral size larger than 50 μm and the area 100 times larger than those exfoliated using the normal "scotch-tape" technique. Using a field effect transistor it was found the hole mobility is 68.6 cm V s and the current on/off ratio can reach about 2 × 10.
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http://dx.doi.org/10.1039/c7cc08488aDOI Listing
January 2018

Global analysis of agricultural soil denitrification in response to fertilizer nitrogen.

Sci Total Environ 2018 Mar 28;616-617:908-917. Epub 2017 Oct 28.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China. Electronic address:

Terrestrial soil denitrification is of great importance for closing the nitrogen (N) cycle, yet the current understanding of soil denitrification response to N fertilization remains uncertain. While there has been a focus on factors controlling NO fluxes from agricultural soils because of its global warming effect, much less is known about factors controlling total denitrification losses, yet these can be sufficiently large to affect N use efficiency. Here, we collated 353 observations from 74 papers and conducted a global-scale meta-analysis to explore the effects of N fertilization on agricultural soil denitrification (NO+N) where the acetylene inhibition technique was used. Relative to the control, N fertilization significantly increased soil denitrification by an average of 174%, although the magnitude of this increase differed significantly across environmental and soil conditions. Soil denitrification was more responsive to N fertilization in grasslands than in croplands. The changes in soil denitrification increased exponentially when the rates of synthetic N fertilizer application≤250kgNha, but above this threshold, there were no further increases. The responses of soil denitrification to N fertilization were negatively correlated with soil clay content, C:N ratio, and bulk density. The comparable responses of soil NO emissions (165%) and denitrification to N fertilization resulted in a small insignificant decrease of the NO:N ratio. Organic fertilizer applied with and without synthetic N fertilizer can contribute to lower NO emissions probably by facilitating the last step of soil denitrification to N production. Taken together, we conclude that these findings can provide important insights on regulating soil denitrification, which might contribute to improvement of N use efficiency and elimination of its negative impacts in agro-ecosystems.
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http://dx.doi.org/10.1016/j.scitotenv.2017.10.229DOI Listing
March 2018

Arabidopsis KHZ1 and KHZ2, two novel non-tandem CCCH zinc-finger and K-homolog domain proteins, have redundant roles in the regulation of flowering and senescence.

Plant Mol Biol 2017 Dec 26;95(6):549-565. Epub 2017 Oct 26.

State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.

Key Message: The two novel CCCH zinc-finger and K-homolog (KH) proteins, KHZ1 and KHZ2, play important roles in regulating flowering and senescence redundantly in Arabidopsis. The CCCH zinc-finger proteins and K-homolog (KH) proteins play important roles in plant development and stress responses. However, the biological functions of many CCCH zinc-finger proteins and KH proteins remain uncharacterized. In Arabidopsis, KHZ1 and KHZ2 are characterized as two novel CCCH zinc-finger and KH domain proteins which belong to subfamily VII in CCCH family. We obtained khz1, khz2 mutants and khz1 khz2 double mutants, as well as overexpression (OE) lines of KHZ1 and KHZ2. Compared with the wild type (WT), the khz2 mutants displayed no defects in growth and development, and the khz1 mutants were slightly late flowering, whereas the khz1 khz2 double mutants showed a pronounced late flowering phenotype. In contrast, artificially overexpressing KHZ1 and KHZ2 led to the early flowering. Consistent with the late flowering phenotype, the expression of flowering repressor gene FLC was up-regulated, while the expression of flowering integrator and floral meristem identity (FMI) genes were down-regulated significantly in khz1 khz2. In addition, we also observed that the OE plants of KHZ1 and KHZ2 showed early leaf senescence significantly, whereas the khz1 khz2 double mutants showed delayed senescence of leaf and the whole plant. Both KHZ1 and KHZ2 were ubiquitously expressed throughout the tissues of Arabidopsis. KHZ1 and KHZ2 were localized to the nucleus, and possessed both transactivation activities and RNA-binding abilities. Taken together, we conclude that KHZ1 and KHZ2 have redundant roles in the regulation of flowering and senescence in Arabidopsis.
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http://dx.doi.org/10.1007/s11103-017-0667-8DOI Listing
December 2017

The counter-balance between ammonia absorption and the stimulation of volatilization by periphyton in shallow aquatic systems.

Bioresour Technol 2018 Jan 21;248(Pt B):21-27. Epub 2017 Jul 21.

Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address:

Ammonia (NH) volatilization is one of the main pathways of nitrogen (N). The aim of this work was to investigate the determinants of NH volatilization, and characterize how the overlying water, sediment, and periphyton interact to regulate the rates of NH volatilization in shallow aquatic systems. Two types of structural equation modeling (SEM) methods ('elements' and 'components' models) were evaluated to examine the complex multivariate response of NH volatilization. The N components and the pH in the 'elements' models exerted significant and positive effects on NH volatilization. The water column accounted for the greatest variation of NH volatilization in a favorable pH environment and high NH-N concentrations according to the 'components' models. Although periphyton biofilm prohibited the direct flow of NH gas, this was counter-balanced by its indirect stimulation effects that positively affected the NH-N and DOC concentrations and the pH in both the overlying water and the sediment.
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http://dx.doi.org/10.1016/j.biortech.2017.07.100DOI Listing
January 2018
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