Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions

PubMed Central

Quin, P; Joseph, S; Husson, O; Donne, S; Mitchell, D; Munroe, P; Phelan, D; Cowie, A; Van Zwieten, L

2015-01-01

Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C) – 0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS) – in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O. PMID:26615820

Crystal structure of aqua-1κO-{μ-2-[(2-hydroxy­ethyl)methylamino]ethanolato-2:1κ4 O 1,N,O 2:O 1}[μ-2,2′-(methylimino)diethanolato-1:2κ4 O,N,O′:O]dithiocyanato-1κN,2κN-chromium(III)copper(II)

PubMed Central

Rusanova, Julia A.; Semenaka, Valentina V.; Dyakonenko, Viktoriya V.; Shishkin, Oleg V.

2015-01-01

The title compound, [CrCu(C5H11NO2)(C5H12NO2)(NCS)2(H2O)] or [Cr(μ-mdea)Cu(μ-Hmdea)(NCS)2H2O], (where mdeaH2 is N-methylethanolamine, C5H13NO2) is formed as a neutral heterometal CuII/CrIII complex. The mol­ecular structure of the complex is based on a binuclear {CuCr(μ-O)2} core. The coordination environment of each metal atom involves the N,O,O atoms of the tridentate ligand, one bridging O atom of the ligand and the N atom of the thio­cyanato ligands. The CuII ion adopts a distorted square-pyramidal coordination while the CrIII ion has a distorted octa­hedral coordination geometry completed by the aqua ligand. In the crystal, the binuclear complexes are linked via two pairs of O—H⋯O hydrogen bonds to form inversion dimers, which are arranged in columns parallel to the a axis. In the μ-mdea ligand two –CH2 groups and the methyl group were refined as disordered over two sets of sites with equal occupancies. The structure was refined as a two-component twin with a twin scale factor of 0.242 (1). PMID:26396853

Solubility and diffusivity of N{sub 2}O and CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-1-propanol + water)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, M.H.; Lai, M.D.

1995-03-01

Solutions of amines are frequently used in gas-treating processes to remove acid gases, such as CO{sub 2} and H{sub 2}S, from gas streams in the natural gas and synthetic ammonia industries and petroleum chemical plants. The solubility and diffusivity of N{sub 2}O in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water) were measured at 30, 35, and 40 C and at atmospheric pressure. Six (monoethanolamine + N-methyldiethanolamine + water) and five (monoethanolamine + 2-amino-2-methyl-l-propanol + water) systems were studied. The total amine mass percent in all cases was 30. The solubilities were measured by a solubilitymore » apparatus similar to that of Haimour and Sandall (1984). A wetted wall column absorber was used to obtain the diffusivity of N{sub 2}O in amines. The N{sub 2}O solubilities in amine solutions have been correlated on the basis of the excess Henry constant correlation of Wang et al. (1992). The N{sub 2}O analogy was used to estimate the solubility and diffusivity of CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water).« less

Infrared Spectroscopic Measurements of the Ethane (C2H6) Total Column Abundance Above Mauna Loa, Hawaii: Seasonal Variations

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Goldman, A.; Murcray, F. J.; David, S. J.; Blatherwick, R. D.; Murcray, D. G.

1994-01-01

About 200 i.r. solar spectra recorded at 0.01/ cm resolution on 71 days between November 1991 and July 1993 at the Network for the Detection of Stratospheric Change (NDSC) station at Mauna Loa, Hawaii (latitude 19.53 deg N, longitude 155.58 deg W, elevation 3.459 km) have been analyzed with a nonlinear least-squares spectral fitting technique to study temporal variations in the total column of atmospheric ethane (C2H6) above the site. The results were derived from the analysis of the unresolved nu(sub 7) band (sup P)Q(sub 3) subbranch at 2976.8/cm. A distinct seasonal cycle is observed with a factor of 2 variation, a maximum total column of 1.1 6 x 10(exp 16) mol /sq cm at the end of winter, and a minimum total column of 0.53 x 10(exp 16) mol/sq cm at the end of summer. Our measurements are compared with previous observations and model predictions.

Infrared spectroscopic measurements of the ethane (C2H6) total column abundance above Mauna Loa, Hawaii -- seasonal variations

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Goldman, A.; Murcray, F. J.; David, S. J.; Blatherwick, R. D.; Murcray, D. G.

1994-01-01

About 200 i.r. solar spectra recorded at 0.01/cm resolution on 71 days between November 1991 and July 1993 at the Network for the Detection of Stratospheric Change (NDSC) station at Mauna Loa, Hawaii (latitude 19.53 deg N, longitude 155.58 deg W, elevation 3.459 km) have been analyzed with a nonlinear least-squares spectral fitting technique to study temporal variations in the total column of atmospheric ethane (C2H6) above the site. The results were derived from the analysis of the unresolved nu(sub 7) band (P)Q(sub 3) subbranch at 2976.8/cm. A distinct seasonal cycle is observed with a factor of 2 variation, a maximum total column of 1.16 x 10(exp 16) mol/sq cm at the end of winter, and a minimum total column of 0.53 x 10(exp 16) mol/sq cm at the end of summer. Our measurements are compared with previous observations and model predictions.

Miniaturized Laser Heterodyne Radiometer for Measurements of CO2 in the Atmospheric Column

NASA Technical Reports Server (NTRS)

Wilson, E. L.; Mclinden, M. L.; Miller, J. H.; Allan, G. R.; Lott, L. E.; Melroy, H. R.; Clarke, G. B.

2013-01-01

We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H2O) and nitrous oxide (N2O).

On the production of N2O from the reaction of O/1D/with N2.

NASA Technical Reports Server (NTRS)

Simonaitis, R.; Lissi, E.; Heicklen, J.

1972-01-01

Ozone was photolyzed at 2537 A and at 25 C in the presence of 42-115 torr of O2 and about 880 torr of N2 to test the relative importance of the two reactions O(1D) + N2 + M leading to N2O + M and O(1D) + N2 leading to O(3P) + N2. In this study N2O was not found as a product. Thus from our detectability limit for N2O an upper limit to the efficiency of the first reaction relative to the second of 2.5 times 10 to the -6 power at 1000-torr total pressure was computed.

On the production of N2O from the reaction of O(1 D) with N2

NASA Technical Reports Server (NTRS)

Simonaitis, R.; Lissi, E.; Heicklen, J.

1972-01-01

Ozone was photolyzed at 2537 A and 25 C in the presence of 42-115 torr of O2 and about 880 torr of N2 to test the relative importance of the two reactions: (1) O(1D) + N2 + M yields N2O + M, and (2) O(1D) + N2 yields O(3P) + N2. N2O was not found as a product. Thus from our detectability limit for N2O (0.3 micron), an upper limit to the efficiency of the first reaction relative to the second of 0.0000025 at 1000 torr total pressure was computed. This corresponds to k1/k2 smaller than 0.8 x 10 to the minus 25 power cu cm/particle.

Spatial and Temporal Variability of Ground and Satellite Column Measurements of NO2 and O3 over the Atlantic Ocean During the Deposition of Atmospheric Nitrogen to Coastal Ecosystems Experiment

NASA Technical Reports Server (NTRS)

Martins, Douglas K.; Najjar, Raymond G.; Tzortziou, Maria; Abuhassan, Nader; Thompson, Anne M.; Kollonige, Debra E.

2016-01-01

In situ measurements of O3 and nitrogen oxides (NO + NO2=NOx) and remote sensing measurements of total column NO2 and O3 were collected on a ship in the North Atlantic Ocean as part of the Deposition of Atmospheric Nitrogen to Coastal Ecosystems (DANCE) campaign in July August 2014,100 km east of the mid-Atlantic United States. Relatively clean conditions for both surface in situ mixing ratio and total column O3 and NO2 measurements were observed throughout the campaign. Increased surface and column NO2 and O3 amounts were observed when a terrestrial air mass was advected over the study region. Relative to ship-based total column measurements using a Pandora over the entire study, satellite measurements overestimated total column NO2 under these relatively clean atmospheric conditions over offshore waters by an average of 16. Differences are most likely due to proximity, or lack thereof, to surface emissions; spatial averaging due to the field of view of the satellite instrument; and the lack of sensitivity of satellite measurements to the surface concentrations of pollutants. Total column O3 measurements from the shipboard Pandora showed good correlation with the satellite measurements(r 0.96), but satellite measurements were 3 systematically higher than the ship measurements, in agreement with previous studies. Derived values of boundary layer height using the surface in situ and total column measurements of NO2 are much lower than modeled and satellite-retrieved boundary layer heights, which highlight the differences in the vertical distribution between terrestrial and marine environments.

Optimization of CO2 Surface Flux using GOSAT Total Column CO2: First Results for 2009-2010

NASA Astrophysics Data System (ADS)

Basu, S.; Houweling, S.

2011-12-01

Constraining surface flux estimates of CO2 using satellite measurements has been one of the long-standing goals of the atmospheric inverse modeling community. We present the first results of inverting GOSAT total column CO2 measurements for obtaining global monthly CO2 flux maps over one year (June 2009 to May 2010). We use the SRON RemoTeC retrieval of CO2 for our inversions. The SRON retrieval has been shown to have no bias when compared to TCCON total column measurements, and latitudinal gradients of the retrieved CO2 are consistent with gradients deduced from the surface flask network [Butz et al, 2011]. This makes this retrieval an ideal candidate for atmospheric inversions, which are highly sensitive to spurious gradients. Our inversion system is analogous to the CarbonTracker (CT) data assimilation system; it is initialized with the prior CO2 fluxes of CT, and uses the same atmospheric transport model, i.e., TM5. The two major differences are (a) we add GOSAT CO2 data to the inversion in addition to flask data, and (b) we use a 4DVAR optimization system instead of a Kalman filter. We compare inversions using (a) only GOSAT total column CO2 measurements, (b) only surface flask CO2 measurements, and (c) the joint data set of GOSAT and surface flask measurements. We validate GOSAT-only inversions against the NOAA surface flask network and joint inversions against CONTRAIL and other aircraft campaigns. We see that inverted fluxes from a GOSAT-only inversion are consistent with fluxes from a stations-only inversion, reaffirming the low biases in SRON retrievals. From the joint inversion, we estimate the amount of added constraints upon adding GOSAT total column measurements to existing surface layer measurements.

Validation of GOME-2/Metop total column water vapour with ground-based and in situ measurements

NASA Astrophysics Data System (ADS)

Kalakoski, Niilo; Kujanpää, Jukka; Sofieva, Viktoria; Tamminen, Johanna; Grossi, Margherita; Valks, Pieter

2016-04-01

The total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde observations and global positioning system (GPS) retrievals. The validation is performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The time periods for the validation are January 2007-July 2013 (GOME-2A) and December 2012-July 2013 (GOME-2B). The radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by the National Climatic Data Center (NCDC). The ground-based GPS observations from the COSMIC/SuomiNet network are used as the second independent data source. We find a good general agreement between the GOME-2 and the radiosonde/GPS data. The median relative difference of GOME-2 to the radiosonde observations is -2.7 % for GOME-2A and -0.3 % for GOME-2B. Against the GPS, the median relative differences are 4.9 % and 3.2 % for GOME-2A and B, respectively. For water vapour total columns below 10 kg m-2, large wet biases are observed, especially against the GPS retrievals. Conversely, at values above 50 kg m-2, GOME-2 generally underestimates both ground-based observations.

New insights into the column CH2O/NO2 ratio as an indicator of near-surface ozone sensitivity

NASA Astrophysics Data System (ADS)

Schroeder, Jason R.; Crawford, James H.; Fried, Alan; Walega, James; Weinheimer, Andrew; Wisthaler, Armin; Müller, Markus; Mikoviny, Tomas; Chen, Gao; Shook, Michael; Blake, Donald R.; Tonnesen, Gail S.

2017-08-01

Satellite-based measurements of the column CH2O/NO2 ratio have previously been used to estimate near-surface ozone (O3) sensitivity (i.e., NOx or VOC limited), and the forthcoming launch of air quality-focused geostationary satellites provides a catalyst for reevaluating the ability of satellite-measured CH2O/NO2 to be used in this manner. In this study, we use a 0-D photochemical box model to evaluate O3 sensitivity and find that the relative rate of radical termination from radical-radical interactions to radical-NOx interactions (referred to as LROx/LNOx) provides a good indicator of maximum O3 production along NOx ridgelines. Using airborne measurements from NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relative to Air Quality (DISCOVER-AQ) deployments in Colorado, Maryland, and Houston, we show that in situ measurements of CH2O/NO2 can be used to indicate O3 sensitivity, but there is an important "transition/ambiguous" range whereby CH2O/NO2 fails to categorize O3 sensitivity, and the range and span of this transition/ambiguous range varies regionally. Then, we apply these findings to aircraft-derived column density measurements from DISCOVER-AQ and find that inhomogeneities in vertical mixing in the lower troposphere further degrades the ability of column CH2O/NO2 to indicate near-surface O3 sensitivity (i.e., the transition/ambiguous range is much larger than indicated by in situ data alone), and we hypothesize that the global transition/ambiguous range is sufficiently large to make the column CH2O/NO2 ratio unuseful for classifying near-surface O3 sensitivity. Lastly, we present a case study from DISCOVER-AQ-Houston that suggests that O3 sensitivity on exceedance days may be substantially different than on nonexceedance days (which may be observable from space) and explore the diurnal evolution of O3 sensitivity, O3 production, and the column CH2O/NO2 ratio. The results of these studies suggest that

N2O production by nitrifier denitrification in the Benguela Upwelling System

NASA Astrophysics Data System (ADS)

Frame, C. H.; Hou, L.; Lehmann, M. F.

2014-12-01

The Benguela upwelling system off the coast of southwestern Africa is an important zone of marine N2O production whose upwelling rates vary seasonally. Here we present N2O stable isotopic and isotopomeric data collected during a period of high upwelling (September 2013) and low upwelling (January 2014). During both periods, 15N-nitrite and 15N-ammonium tracer inucbation experiments were used to investigate N2O production by ammonia oxidizing microorganisms in the top 150m of the water column. N2O production from 15N-ammonium was not measurable during these incubations. However, we detected N2O production from 15N-nitrite, suggesting that nitrifier denitrification is a source of shallow N2O in this region. Furthermore, decreasing the pH of the incubation water enhanced the amount of N2O produced, suggesting that upwelling of CO2-rich/low-pH deep water may enhance N2O production in this region. Finally, we present our incubation data in the larger context of the N2O and nitrite isotopic and concentration profiles, with an eye toward comparing incubation-based N2O production rates with profile-based estimates.

Observed and simulated time evolution of HCl, ClONO2, and HF total columns

NASA Astrophysics Data System (ADS)

Ruhnke, Roland; Geomon, Ndacc Infrared, Modelling Working Group

2010-05-01

Institute of Technology (KIT), IMK-IFU, Garmisch-Partenkirchen, Germany, (16) University of Denver, Dept. of Physics and Astronomy, Denver, CO, USA, (17) National Center for Atmospheric Research (NCAR), Boulder, CO, USA, (18) NASA Langley Research Center, Hampton, VA, USA, (19) Karlsruhe Institute of Technology (KIT), Steinbuch Centre for Computing, Karlsruhe, Germany Total column abundances of HCl and ClONO2, the primary components of the stratospheric inorganic chlorine (Cly) budget, and of HF have been retrieved from ground-based, high-resolution infrared solar absorption spectra recorded at 17 sites of the Network for the Detection of Atmospheric Composition Change (NDACC) located at latitudes between 80.05°N and 77.82°S. These data extend over more than 20 years (through 2007) during a period when the growth in atmospheric halogen loading has slowed in response to the Montreal Protocol (and ammendments). These observed time series are interpreted with calculations performed with a 2-D model, the 3-D chemistry-transport models (CTMs) KASIMA and SLIMCAT, and the 3-D chemistry-climate models (CCMs) EMAC and SOCOLv2.0. The observed Cly and in particular HCl column abundances decreases significantely since the end of the nineties at all stations, which is consistent with the observed changes in the halocarbon source gases, with an increasing rate in the last years. In contrast to Cly, the trend values for total column HF at the different stations show a less consistent behaviour pointing to the fact that the time development of the HF columns is peaking. There is a good overall qualitative agreement regarding trends between models and data. With respect to the CTMs the agreement improves if simulation results for measurement days only are used in the trend analysis instead of simulation results for each day.

Facile preparation of SiO2/TiO2 composite monolithic capillary column and its application in enrichment of phosphopeptides.

PubMed

Wang, Shao-Ting; Wang, Meng-Ya; Su, Xin; Yuan, Bi-Feng; Feng, Yu-Qi

2012-09-18

A novel SiO(2)/TiO(2) composite monolithic capillary column was prepared by sol-gel technology and successfully applied to enrich phosphopeptides as a metal oxide affinity chromatography (MOAC) material. For the monolith preparation, tetramethoxysilane (TMOS) and tetrabutoxytitanium (TBOT) were used as silica and titania source, respectively, and glycerol was introduced to attenuate the activity of titanium precursor, which provided a mild synthetic condition. The prepared monolith was characterized by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results revealed an approximate 1/2 molar ratio of titanium to silica as well as an atom-scale homogeneity in the framework. The scanning electron microscopy (SEM) results demonstrated an excellent anchorage between the column and the inner capillary wall, and nitrogen adsorption-desorption experiments showed a bimodal porosity with a narrow mesopore distribution around 3.6 nm. The prepared monolith was then applied for selective enrichment of phosphopeptides from the digestion mixture of phosphoproteins and bovine serum albumin (BSA) as well as human blood serum, nonfat milk, and egg white using an in-tube solid phase microextraction (SPME) system. Our results showed that SiO(2)/TiO(2) composite monolithic capillary column could efficiently enrich the phosphopeptides from complex matrixes. To the best of our knowledge, this is the first attempt for preparing the silica-metal composite monolithic capillary column, which offers the promising application of the monolith on phosphoproteomics study.

N2O emissions from a nitrogen-enriched river

USGS Publications Warehouse

McMahon, P.B.; Dennehy, K.F.

1999-01-01

Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994- 1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2 x 1013-6 x 1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal wastewater treatment processes in the United States (1). Results from this study indicate that N-enriched rivers could be important anthropogenic sources of N2O to the atmosphere. However, N2O emission measurements from other N-enriched rivers are needed to better quantify this source.Nitrous oxide (N2O) emissions from the South Platte River in Colorado were measured using closed chambers in the fall, winter, and summer of 1994-1995. The South Platte River was enriched in inorganic N (9-800 ??M) derived from municipal wastewater effluent and groundwater return flows from irrigated agricultural fields. River water was as much as 2500% supersaturated with N2O, and median N2O emission rates from the river surface ranged from less than 90 to 32 600 ??g-N m-2 d-1. Seventy-nine percent of the variance in N2O emission rates was explained by concentrations of total inorganic N in river water and by water temperature. The estimated total annual N2O emissions from the South Platte River were 2??1013-6??1013 ??g-N yr-1. This amount of annual N2O emissions was similar to the estimated annual N2O emissions from all primary municipal

Site-specific 15N isotopic signatures of abiotically produced N2O

NASA Astrophysics Data System (ADS)

Heil, Jannis; Wolf, Benjamin; Brüggemann, Nicolas; Emmenegger, Lukas; Tuzson, Béla; Vereecken, Harry; Mohn, Joachim

2014-08-01

Efficient nitrous oxide (N2O) mitigation strategies require the identification of the main source and sink processes and their contribution to total soil N2O production. Several abiotic reactions of nitrification intermediates leading to N2O production are known, but their contribution to total N2O production in soils is uncertain. As the site preference (SP) of 15N in N2O is a promising tool to give more insight into N2O production processes, we investigated the SP of N2O produced by different abiotic reactions in a laboratory study. All reactions involved the nitrification intermediate hydroxylamine (NH2OH) in combination with nitrite (NO2-), Fe3+, Fe2+ and Cu2+, reactants commonly or potentially found in soils, at different concentrations and pH values. N2O production and its four main isotopic species (14N14N16O, 15N14N16O, 14N15N16O, and 14N14N18O) were quantified simultaneously and online at high temporal resolution using quantum cascade laser absorption spectroscopy. Thereby, our study presents the first continuous analysis of δ18O in N2O. The experiments revealed the possibility of purely abiotic reactions over a wide range of acidity (pH 3-8) by different mechanisms. All studied abiotic pathways produced N2O with a characteristic SP in the range of 34-35‰, unaffected by process conditions and remaining constant over the course of the experiments. These findings reflect the benefit of continuous N2O isotopic analysis by laser spectroscopy, contribute new information to the challenging source partitioning of N2O emissions from soils, and emphasize the potentially significant role of coupled biotic-abiotic reactions in soils.

N2O and CH4 emissions from N-fertilized rice paddy soil can be mitigated by wood vinegar application at an appropriate rate

NASA Astrophysics Data System (ADS)

Sun, Haijun; Feng, Yanfang; Ji, Yang; Shi, Weiming; Yang, Linzhang; Xing, Baoshan

2018-07-01

To understand the impacts of wood vinegar (WV), a by-product of biochar production, on N2O and CH4 emissions and their total global warming potential (GWPt) from N-fertilized rice paddy soil, a soil column experiment was conducted using three treatments: 240 kg urea-N ha-1 accompanied with 0, 5, and 10 t WV ha-1, respectively. Results showed that N2O and CH4 emission flux patterns were dominated by water regime of rice growth cycle, which was independent with WV application. The total N2O, CH4 emission loads and GWPt over rice season of three N received treatments were 6.41-8.85 kg ha-1, 127.7-405.0 kg ha-1, and 5.24-12.03 t CO2-e ha-1, respectively. Rice seasonal N2O and CH4 emissions were synchronously mitigated by 22.4% and 36.4%, respectively, when WV was applied at 5 t ha-1. Consequently, 5 t ha-1 WV treatment reduced 31.5% of GWPt compared with the urea treatment. In addition, 10 t ha-1 WV treatment exerted a more positive effect on suppressing N2O with 27.6% reduction. However, it increased GWPt by 57.2% because its CH4 emission load was increased by 101.8%. In conclusion, WV amendment applied at an appropriate rate (5 t ha-1) or combination with other CH4 control technologies were suggested to reduce both N2O and CH4 emissions and thereby the GWPt in N-fertilized rice paddy soil.

40 CFR 1065.275 - N2O measurement devices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... for interpretation of infrared spectra. For example, EPA Test Method 320 is considered a valid method... and length to achieve adequate resolution of the N2O peak for analysis. Examples of acceptable columns....550(b) that would otherwise apply. For example, you may perform a span gas measurement before and...

40 CFR 1065.275 - N2O measurement devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... for interpretation of infrared spectra. For example, EPA Test Method 320 is considered a valid method... and length to achieve adequate resolution of the N2O peak for analysis. Examples of acceptable columns....550(b) that would otherwise apply. For example, you may perform a span gas measurement before and...

Stratospheric N2O5, CH4, and N2O profiles from IR solar occultation spectra

NASA Technical Reports Server (NTRS)

Camy-Peyret, C.; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

1993-01-01

Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur l'Adour, France (44 N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/cm band. Assuming a total intensity of 4.32 x 10 exp -17 cm/molecule/sq cm independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv, interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated 1-sigma uncertainty including the error in the total band intensity. The retrieved profiles are compared with previous measurements and photochemical model results.

Analysis of Satellite-Derived Arctic Tropospheric BrO Columns in Conjunction with Aircraft Measurements During ARCTAS and ARCPAC

NASA Technical Reports Server (NTRS)

Choi, S.; Wang, Y.; Salawitch, R. J.; Canty, T.; Joiner, J.; Zeng, T.; Kurosu, T. P.; Chance, K.; Richter, A.; Huey, L. G.;

Stratospheric N2O5, CH4, and N2O Profiles from IR Solar Occultation Spectra

NASA Technical Reports Server (NTRS)

Peyeret, C. Camy; Flaud, J.-M.; Perrin, A.; Rinsland, C. P.; Goldman, A.; Murcray, F. J.

1993-01-01

Stratospheric volume mixing ratio profiles of N2O5, CH4, and N2O have been retrieved from a set of 0.052/ cm resolution (FWHM) solar occultation spectra recorded at sunrise during a balloon flight from Aire sur I'Adour, France (44 deg N latitude) on 12 October 1990. The N2O5 results have been derived from measurements of the integrated absorption by the 1246/ cm band. Assuming a total intensity of 4.32 x 10(exp 17)cm(exp -1) molecule sq cm(exp -2) independent of temperature, the retrieved N2O5 volume mixing ratios in ppbv (parts per billion by volume, 10(exp -9)), interpolated to 2 km height spacings, are 1.64 +/- 0.49 at 37.5 km, 1.92 +/- 0.56 at 35.5 km, 2.06 +/- 0.47 at 33.5 km, 1.95 +/- 0.42 at 31.5 km, 1.60 +/- 0.33 at 29.5 km, 1.26 +/- 0.28 at 27.5 km, and 0.85 +/- 0.20 at 25.5 km. Error bars indicate the estimated I-sigma uncertainty including the error in the total band intensity (+/- 20% has been assumed). The retrieved profiles are compared with previous measurements and photochemical model results.

Total photoelectron yield spectroscopy of energy distribution of electronic states density at GaN surface and SiO2/GaN interface

NASA Astrophysics Data System (ADS)

Ohta, Akio; Truyen, Nguyen Xuan; Fujimura, Nobuyuki; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

2018-06-01

The energy distribution of the electronic state density of wet-cleaned epitaxial GaN surfaces and SiO2/GaN structures has been studied by total photoelectron yield spectroscopy (PYS). By X-ray photoelectron spectroscopy (XPS) analysis, the energy band diagram for a wet-cleaned epitaxial GaN surface such as the energy level of the valence band top and electron affinity has been determined to obtain a better understanding of the measured PYS signals. The electronic state density of GaN surface with different carrier concentrations in the energy region corresponding to the GaN bandgap has been evaluated. Also, the interface defect state density of SiO2/GaN structures was also estimated by not only PYS analysis but also capacitance–voltage (C–V) characteristics. We have demonstrated that PYS analysis enables the evaluation of defect state density filled with electrons at the SiO2/GaN interface in the energy region corresponding to the GaN midgap, which is difficult to estimate by C–V measurement of MOS capacitors.

Investigation of Seasonal Cycles of CO, CH4, N2O, and O3 in the High Arctic at Eureka, Canada and Barrow, Alaska using Infrared Emission Spectroscopy

NASA Astrophysics Data System (ADS)

Tran, S.; Mariani, Z.; Conway, S. A.; Lutsch, E.; Rowe, P. M.; Kasai, Y.; Strong, K.

2015-12-01

The High Arctic experiences prolonged periods of total darkness in the winter and continuous daylight in the summer, influencing the atmosphere and its composition in ways that are still not fully understood. Making atmospheric measurements in this remote region is challenging, particularly during polar night when solar-viewing instruments are not operational. By using infrared emission spectroscopy, which is independent of sunlight, we are able to document year-round the total column abundances of carbon monoxide (CO), methane (CH4), nitrous oxide (N2O), and ozone (O3). Measurements made at two Arctic sites are presented in this study: the Polar Environment Atmospheric Research Laboratory (PEARL, Eureka, Nunavut, Canada, 80.05°N, 86.42°W) and the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) facility on the North Slope of Alaska (NSA, Barrow, Alaska, 71.19°N, 156.36°W). At both sites, Extended-range Atmospheric Emitted Radiance Interferometers (E-AERIs), are used to measure the absolute downwelling infrared emission from the atmosphere between 400 and 3000 cm-1. The E-AERI has a moderate resolution of 1 cm-1 and provides information about trace gases columns with high sensitivity to the lower troposphere. At PEARL, the instrument was installed in October 2008. In addition, a similar instrument, the University of Idaho's Polar AERI (P-AERI) was installed at PEARL from March 2006 to June 2009. At NSA, the E-AERI has been operating since February 1998. Total columns of CO, CH4, N2O and O3 have been retrieved from 2006 to 2015 at PEARL and from 1998 to 2014 at NSA using the SFIT4 algorithm. These two datasets will be compared along with measurements made by high-resolution solar-viewing infrared spectrometers located at PEARL and at Poker Flat, Alaska (65.12°N, 147.47°W) to validate our results. These measurements will be used to present the annual, seasonal and diurnal variabilities of trace gases in the high Arctic at two different

Comparison of TOMS, SBW & SBUV/2 Version 8 Total Column Ozone Data with Data from Groundstations

NASA Technical Reports Server (NTRS)

Labow, G. J.; McPeters, R. D.; Bhartia, P. K.

2004-01-01

The Nimbus-7 and Earth Probe Total Ozone Mapping Spectrometer (TOMS) data as well as SBUV and SBUV/2 data have been reprocessed with a new retrieval algorithm (Version 8) and an updated calibration procedure. An overview will be presented systematically comparing ozone values to an ensemble of Brewer and Dobson spectrophotometers. The comparisons were made as a function of latitude, solar zenith angle, reflectivity and total ozone. Results show that the accuracy of the TOMS retrieval has been improved when aerosols are present in the atmosphere, when snow/ice and sea glint are present, and when ozone in the northern hemisphere is extremely low. TOMS overpass data are derived from the single TOMS best match measurement, almost always located within one degree of the ground station and usually made within an hour of local noon. The Version 8 Earth Probe TOMS ozone values have decreased by an average of about 1% due to a much better understanding of the calibration of the instrument. N-7 SBUV as well as the series of NOAA SBUV/2 column ozone values have also been processed with the Version 8 algorithm and have been compared to values from an ensemble of groundstations. Results show that the SBW column ozone values agree well with the groundstations and the datasets are useful for trend studies.

The structure, stability, and infrared spectrum of B 2N, B 2N +, B 2N -, BO, B 2O and B 2N 2.

NASA Astrophysics Data System (ADS)

Martin, J. M. L.; François, J. P.; Gijbels, R.

1992-05-01

The structure, infrared spectrum, and heat of formation of B 2N, B 2N -, BO, and B 2O have been studied ab initio. B 2N is very stable; B 2O even more so. B 2N, B 2N -, B 2O, and probably B 2N + have symmetric linear ground-state structures; for B 2O, an asymmetric linear structure lies about 12 kcal/mol above the ground state. B 2N +, B 2N - and B 2O have intense asymmetric stretching frequencies, predicted near 870, 1590 and 1400 cm -1, respectively. Our predicted harmonic frequencies and isotopic shifts for B 2O confirm the recent experimental identification by Andrews and Burkholder. Absorptions at 1889.5 and 1998.5 cm -1 in noble-gas trapped boron nitride vapor belong the BNB and BNBN ( 3Π), respectively; a tentative assignment of 882.5 cm -1 to BNB + is proposed. Total atomization energies Σ De (Σ D0) are computed (accuracy ±2 kcal/mol) as: BO 193.1 (190.4), B 2O 292.5 (288.7), B 2N 225.0 (250.3) kcal/mol. The ionization potential and electron affinity of B 2N are predicted to be 8.62±0.1 and 3.34±0.1 eV. The MP4-level additivity approximations involved in G1 theory results in errors on the order of 1 kcal/mol in the Σ De values.

Year-round N2O production by benthic NOx reduction in a monomictic south-alpine lake

NASA Astrophysics Data System (ADS)

Freymond, C. V.; Wenk, C. B.; Frame, C. H.; Lehmann, M. F.

2013-12-01

Nitrous oxide (N2O) is a potent greenhouse gas, generated through microbial nitrogen (N) turnover processes, such as nitrification, nitrifier denitrification, and denitrification. Previous studies quantifying natural sources have mainly focused on soils and the ocean, but the potential role of terrestrial water bodies in the global N2O budget has been widely neglected. Furthermore, the biogeochemical controls on the production rates and the microbial pathways that produce benthic N2O in lakes are essentially unknown. In this study, benthic N2O fluxes and the contributions of the microbial pathways that produce N2O were assessed using 15N label flow-through sediment incubations in the eutrophic, monomictic south basin of Lake Lugano in Switzerland. The sediments were a significant source of N2O throughout the year, with production rates ranging between 140 and 2605 nmol N2O h-1 m-2, and the highest observed rates coinciding with periods of water column stratification and stably anoxic conditions in the overlying bottom water. Nitrate (NO3-) reduction via denitrification was found to be the major N2O production pathway in the sediments under both oxygen-depleted and oxygen-replete conditions in the overlying water, while ammonium oxidation did not contribute significantly to the benthic N2O flux. A marked portion (up to 15%) of the total NO3- consumed by denitrification was reduced only to N2O, without complete denitrification to N2. These fluxes were highest when the bottom water had stabilized to a low-oxygen state, in contrast with the notion that stable anoxia is particularly conducive to complete denitrification without accumulation of N2O. This study provides evidence that lake sediments are a significant source of N2O to the overlying water and may produce large N2O fluxes to the atmosphere during seasonal mixing events.

Effect of N-fertilization on N2 and N2O flux rates in relation to the structure of the denitrifying bacterial community in fen soil

NASA Astrophysics Data System (ADS)

Augustin, J.; Behrendt, U.; Ulrich, A.

2009-04-01

Drained fen peatlands of north-east Europe managed by different agricultural regimes constitute an important source for emissions of nitrous oxide (N2O) into the atmosphere. The strength of N2O fluxes showed a high variability in time and space influenced by complex interactions of formation and transfer processes with environmental parameters which makes prediction of emissions uncertain. This applies particularly to the denitrification. This is one of the microbial processes with special interest for N2O production in the context of frequently varying soil-moisture content of fen soils that favouring anaerobic conditions. Moreover, denitrification may result in the production of both N2O and N2 in varying proportions. However, not only the knowledge about the effect of soil chemical and physical properties, climate, vegetation, and management on the actual N2O and N2 fluxes is very incomplete at fen soils. There are also no information about the role of structure and activity of denitrifying microbial communities in this context either. The experiments presented in this study aim at addressing this subject matter. Relatively undisturbed soil columns (250 cm3) from a long-term N-fertilization experiment on a fen grassland (over a period of 45 years) were used for measurement of the current N2 and N2O fluxes followed by processing the soil sample for microbiological analysis immediately to investigate the influence of N-fertilization on these parameters. The direct measurement of N2 and N2O fluxes was performed by a helium atmosphere incubation technique in the lab. Results showed a strong influence of N-fertilization and soil moisture on the emission of N2 and N2O. Shifts in the total microbial community were estimated by phospholipid fatty acid analysis, a fingerprint focused on active organisms. Results showed that seasonal effects interfered the influence of N-fertilization on shifts of the total microbial community composition. To characterise the denitrifying

Do natural biofilm impact nZVI mobility and interactions with porous media? A column study.

PubMed

Crampon, Marc; Hellal, Jennifer; Mouvet, Christophe; Wille, Guillaume; Michel, Caroline; Wiener, Anke; Braun, Juergen; Ollivier, Patrick

2018-01-01

Nanoparticles (NP) used as remediation agents for groundwater treatment may interact with biofilms naturally present, altering NP mobility and/or reactivity and thereby NP effectiveness. The influence of the presence of a multi species biofilm on the mobility of two types of zero-valent iron NP (nZVI; NANOFER 25S and optimized NANOFER STAR, NanoIron s.r.o. (Czech Republic)) was tested in laboratory experiments with columns mimicking aquifer conditions. Biofilms were grown in columns filled with sand in nitrate reducing conditions using groundwater from an industrial site as inoculum. After two months growth, they were composed of several bacterial species, dominated by Pseudomonas stutzeri. Biofilm strongly affected the physical characteristics of the sand, decreasing total porosity from ~30% to ~15%, and creating preferential pathways with high flow velocities. nZVI suspensions were injected into the columns at a seepage velocity of 10mday - 1 . Presence of biofilm did not impact the concentrations of Fe at the column outlet nor the amount of total Fe retained in the sand, as attested by the measurement of magnetic susceptibility. However, it had a significant impact on NP size sorting as well as on total Fe distribution along the column. This suggests nZVI-biofilm interactions that were confirmed by microscopic observations using SEM/STEM coupled with energy-dispersive X-ray spectroscopy. Our study shows that biofilm modifies the water flow velocity in the porous media, favoring the transport of large aggregates and decreased NP mobility due to physical and chemical interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Overlap corrections for emissivity calculations of H2O-CO2-CO-N2 mixtures

NASA Astrophysics Data System (ADS)

Alberti, Michael; Weber, Roman; Mancini, Marco

2018-01-01

Calculations of total gas emissivities of gas mixtures containing several radiatively active species require corrections for band overlapping. In this paper, we generate such overlap correction charts for H2O-CO2-N2, H2O-CO-N2, and CO2-CO-N2 mixtures. These charts are applicable in the 0.1-40 bar total pressure range and in the 500 K-2500 K temperature range. For H2O-CO2-N2 mixtures, differences between our charts and Hottel's graphs as well as models of Leckner and Modak are highlighted and analyzed.

Estimating surface NO2 and SO2 mixing ratios from fast-response total column observations and potential application to geostationary missions.

PubMed

Knepp, T; Pippin, M; Crawford, J; Chen, G; Szykman, J; Long, R; Cowen, L; Cede, A; Abuhassan, N; Herman, J; Delgado, R; Compton, J; Berkoff, T; Fishman, J; Martins, D; Stauffer, R; Thompson, A M; Weinheimer, A; Knapp, D; Montzka, D; Lenschow, D; Neil, D

Total-column nitrogen dioxide (NO 2 ) data collected by a ground-based sun-tracking spectrometer system (Pandora) and an photolytic-converter-based in-situ instrument collocated at NASA's Langley Research Center in Hampton, Virginia were analyzed to study the relationship between total-column and surface NO 2 measurements. The measurements span more than a year and cover all seasons. Surface mixing ratios are estimated via application of a planetary boundary-layer (PBL) height correction factor. This PBL correction factor effectively corrects for boundary-layer variability throughout the day, and accounts for up to ≈75 % of the variability between the NO 2 data sets. Previous studies have made monthly and seasonal comparisons of column/surface data, which has shown generally good agreement over these long average times. In the current analysis comparisons of column densities averaged over 90 s and 1 h are made. Applicability of this technique to sulfur dioxide (SO 2 ) is briefly explored. The SO 2 correlation is improved by excluding conditions where surface levels are considered background. The analysis is extended to data from the July 2011 DISCOVER-AQ mission over the greater Baltimore, MD area to examine the method's performance in more-polluted urban conditions where NO 2 concentrations are typically much higher.

Production of N2O/+/ by reaction of metastable O2/+/ ions with N2

NASA Technical Reports Server (NTRS)

Ajello, J. M.; Rayermann, P.

1975-01-01

Photoionization mass spectrometry examination of the production of N2O(+) was undertaken to determine whether N2(+) or O2(+) ions are responsible for onset of N2O(+). It appears that the N2(+) ion does not contribute significantly to the production of N2O(+) in this experiment. Therefore, it is clear that excited O2(+) is responsible for the formation of N2O(+) near the appearance potential of these ions.

Nanoscale Titanium Dioxide (nTiO2) Transport in Water-Saturated Natural Sediments: Influence of Soil Organic Matter and Fe/Al Oxyhydroxides

NASA Astrophysics Data System (ADS)

Fisher-Power, L.; Cheng, T.

2017-12-01

Transport of engineered nanoparticles (ENP) in subsurface environments has important implications to water quality and soil contamination. Although extensive research has been conducted to understand the effects of water chemistry on ENP transport, less attention has been paid to influences from the transport medium/matrix. The objective of this research is to investigate the effects of natural organic matter (NOM) and Fe/Al oxyhydroxides in a natural sediment on ENP transport. A sediment was collected and separated into four portions, one of which was unmodified, and the others treated to remove specific components (organic matter, Fe/Al oxyhydroxides, or both organic matter and Fe/Al oxyhydroxides). Transport of nanoscale titanium dioxide (nTiO2) in columns packed with quartz sand and each of the four types of the sediment under water-saturated conditions was studied. Our results showed that nTiO2 transport was strongly influenced by pH and sediment composition. When influent pH = 5, nTiO2 transport in all the sediments was low, as positively-charged nTiO2 was attracted to negatively charged NOM, quartz, and other minerals. nTiO2 transport was slightly enhanced in columns packed with untreated sediment or Fe/Al oxyhydroxides removed sediment due to dissolved organic matter generated by the partial dissolution of NOM, which adsorbed onto nTiO2 surface and reversed its zeta potential to negative. When influent pH = 9, nTiO2 transport was generally high since negatively-charged nTiO2 was repelled by negatively charged transport medium. However, in columns packed with the organic matter removed sediment or the Fe/Al oxyhydroxides removed sediment, nTiO2 transport was low. This was attributable to pH buffering by the sediment, which decreased pore water pH in the column, resulting in zeta potential change and electrostatic attraction between Fe/Al oxyhydroxides and nTiO2. This research demonstrates that electrostatic forces between nTiO2 and mineral/organic components

Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Column

EPA Science Inventory

Distinct effects of humic acid (HA, 0 – 10 mg L-1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3 – 200 mM NaCl, pH 5.7 and 9.0). Specifical...

Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Columns

EPA Science Inventory

The distinct effects of humic acid (HA, 0−10 mg L−1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3−200 mM NaCl, pH 5.7 and 9.0). Specifically, the tra...

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

NASA Astrophysics Data System (ADS)

Werner, C.; Reiser, K.; Dannenmann, M.; Hutley, L. B.; Jacobeit, J.; Butterbach-Bahl, K.

2014-11-01

Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N2O), nitric oxide (NO) and dinitrogen (N2) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N2O, NO and carbon dioxide (CO2). Furthermore, the release of N2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N2O emissions were very low (<7.0 ± 5.0 μg NO-N m-2 h-1; <0.0 ± 1.4 μg N2O-N m-2 h-1) or in the case of N2O, even a net soil uptake was observed. Substantial NO (max: 306.5 μg N m-2 h-1) and relatively small N2O pulse emissions (max: 5.8 ± 5.0 μg N m-2 h-1) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N2 emissions (82.4-99.3% of total N lost), although NO emissions contributed almost 43.2% to the total atmospheric nitrogen loss at 50% SM and 30 °C ST incubation settings (the contribution of N2 at these soil conditions was only 53.2%). N2O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N2O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha-1 yr-1 (N2O), 0.68 kg N ha-1 yr-1 (NO) and 6.65 kg N ha-1 yr-1 (N2). The analysis of long-term SM and ST records makes it clear that extreme soil saturation that can lead to high N2O and N2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events

Tungsten Bronze Barium Neodymium Titanate (Ba(6-3n)Nd(8+2n)Ti(18)O(54)): An Intrinsic Nanostructured Material and Its Defect Distribution.

PubMed

Azough, Feridoon; Cernik, Robert Joseph; Schaffer, Bernhard; Kepaptsoglou, Demie; Ramasse, Quentin Mathieu; Bigatti, Marco; Ali, Amir; MacLaren, Ian; Barthel, Juri; Molinari, Marco; Baran, Jakub Dominik; Parker, Stephen Charles; Freer, Robert

2016-04-04

We investigated the structure of the tungsten bronze barium neodymium titanates Ba(6-3n)Nd(8+2n)Ti(18)O(54), which are exploited as microwave dielectric ceramics. They form a complex nanostructure, which resembles a nanofilm with stacking layers of ∼12 Å thickness. The synthesized samples of Ba(6-3n)Nd(8+2n)Ti(18)O(54) (n = 0, 0.3, 0.4, 0.5) are characterized by pentagonal and tetragonal columns, where the A cations are distributed in three symmetrically inequivalent sites. Synchrotron X-ray diffraction and electron energy loss spectroscopy allowed for quantitative analysis of the site occupancy, which determines the defect distribution. This is corroborated by density functional theory calculations. Pentagonal columns are dominated by Ba, and tetragonal columns are dominated by Nd, although specific Nd sites exhibit significant concentrations of Ba. The data indicated significant elongation of the Ba columns in the pentagonal positions and of the Nd columns in tetragonal positions involving a zigzag arrangement of atoms along the b lattice direction. We found that the preferred Ba substitution occurs at Nd[3]/[4] followed by Nd[2] and Nd[1]/[5] sites, which is significantly different to that proposed in earlier studies. Our results on the Ba(6-3n)Nd(8+2n)Ti(18)O(54) "perovskite" superstructure and its defect distribution are particularly valuable in those applications where the optimization of material properties of oxides is imperative; these include not only microwave ceramics but also thermoelectric materials, where the nanostructure and the distribution of the dopants will reduce the thermal conductivity.

Selective Encaging of N2O in N2O-N2 Binary Gas Hydrates via Hydrate-Based Gas Separation.

PubMed

Yang, Youjeong; Shin, Donghoon; Choi, Seunghyun; Woo, Yesol; Lee, Jong-Won; Kim, Dongseon; Shin, Hee-Young; Cha, Minjun; Yoon, Ji-Ho

2017-03-21

The crystal structure and guest inclusion behaviors of nitrous oxide-nitrogen (N 2 O-N 2 ) binary gas hydrates formed from N 2 O/N 2 gas mixtures are determined through spectroscopic analysis. Powder X-ray diffraction results indicate that the crystal structure of all the N 2 O-N 2 binary gas hydrates is identified as the structure I (sI) hydrate. Raman spectra for the N 2 O-N 2 binary gas hydrate formed from N 2 O/N 2 (80/20, 60/40, 40/60 mol %) gas mixtures reveal that N 2 O molecules occupy both large and small cages of the sI hydrate. In contrast, there is a single Raman band of N 2 O molecules for the N 2 O-N 2 binary gas hydrate formed from the N 2 O/N 2 (20/80 mol %) gas mixture, indicating that N 2 O molecules are trapped in only large cages of the sI hydrate. From temperature-dependent Raman spectra and the Predictive Soave-Redlich-Kwong (PSRK) model calculation, we confirm the self-preservation of N 2 O-N 2 binary gas hydrates in the temperature range of 210-270 K. Both the experimental measurements and the PSRK model calculations demonstrate the preferential occupation of N 2 O molecules rather than N 2 molecules in the hydrate cages, leading to a possible process for separating N 2 O from gas mixtures via hydrate formation. The phase equilibrium conditions, pseudo-pressure-composition (P-x) diagram, and gas storage capacity of N 2 O-N 2 binary gas hydrates are discussed in detail.

Monitoring N2O Production Using a cNOR Modeled Active Site

NASA Astrophysics Data System (ADS)

Griffiths, Z. G.; Hegg, E. L.; Finders, C.; Haslun, J. A.

2017-12-01

Nitrous oxide (N2O) is a potent greenhouse gas with a 100-year global warming potential 265-296 times greater than carbon dioxide (CO2). It is the leading contributor to ozone depletion and can persist in the stratosphere for approximately 114 years. Hence, understanding the sources of atmospheric N2O emissions is critical to remediating the effects of climate change. Agricultural activities are the largest contributor to N2O emissions in the U.S. with microbial nitrification and denitrification as the dominating soil processes. The enzyme cytochrome c nitric oxide reductase (cNOR) is involved in bacterial denitrification. It is often difficult to study the enzymes involved in biotic N2O production, hence, model enzymes are a useful tool. The enzyme I107EFeBMb, a sperm whale myoglobin derivative, models the active site of cNOR and was used to simulate the anaerobic reduction of NO to N2O by cNOR. Dithionite was used to induce the catalytic activity of I107EFeBMb by reducing the enzyme. However, dithionite is a strong reductant that is capable of reducing NO to N2O directly. Therefore, the dithionite-enzyme mixture was passed through a size-exclusion column to isolate the reduced enzyme. This reduced and purified enzyme was then utilized to investigate N2O production from NO. This project will provide both an enzymatic and abiotic model to study N2O production.

Carbon availability and the distribution of denitrifying organisms influence N2O production in the hyporheic zone

NASA Astrophysics Data System (ADS)

Farrell, T. B.; Quick, A. M.; Reeder, W. J.; Tonina, D.; Benner, S. G.; Feris, K. P.

2013-12-01

It has been estimated that 10% of greenhouse gas N2O emissions take place within river networks, with the majority of these processes occurring in the hyporheic zone (HZ). These emissions are the result of microbially-mediated nitrogen transformations (i.e. nitrification and denitrification) and yet the role of microbial distribution and function in this complex system is not well understood. We hypothesized that the concentration and availability of organic carbon influences the production of redox gradients, DIN (via mineralization, nitrification, and loss of DIN via denitrification), and ultimately N2O production in the HZ by controlling the distribution and activity of denitrifying microbial communities. Further, we hypothesized that by linking the distribution of denitrifying microbial communities and their associated functional genes (i.e. the relative abundance of N2O vs. N2 producing genetic elements) to flow dynamics and biogeochemical processes, we can begin to better understand what controls N2O production in hyporheic networks. To address these hypotheses we performed a series of column experiments designed to determine the influence of carbon concentration on redox gradient development and N2O flux along a one-dimensional flow path. Intact sediment cores were amended with 0.01%, 0.05%, 0.15%, and 0.5% dry mass riparian vegetation (>90% Populus sp.) to serve as an endogenous particulate organic matter (POM) source. During quasi-steady state conditions dissolved oxygen (DO), NH4+, NO3-, and N2O levels were measured. As predicted, a positive relationship between the level of POM amendment and development of a gradient of oxic and anoxic conditions was observed. There was negligible N2O production within columns inoculated with 0.01% and 0.05% DOC likely because these POC treatments were too low to create anoxic conditions necessary to stimulate denitrification. Maximum N2O flux was observed with the 0.15% POC treatment. Both oxic and anoxic conditions

Estimating 40 years of nitrogen deposition in global biomes using the SCIAMACHY NO2 column

USGS Publications Warehouse

Lu, Xuehe; Zhang, Xiuying; Liu, Jinxun; Jin, Jiaxin

2016-01-01

Owing to human activity, global nitrogen (N) cycles have been altered. In the past 100 years, global N deposition has increased. Currently, the monitoring and estimating of N deposition and the evaluation of its effects on global carbon budgets are the focus of many researchers. NO2 columns retrieved by space-borne sensors provide us with a new way of exploring global N cycles and these have the ability to estimate N deposition. However, the time range limitation of NO2 columns makes the estimation of long timescale N deposition difficult. In this study we used ground-based NOx emission data to expand the density of NO2columns, and 40 years of N deposition (1970–2009) was inverted using the multivariate linear model with expanded NO2 columns. The dynamic of N deposition was examined in both global and biome scales. The results show that the average N deposition was 0.34 g N m–2 year–1 in the 2000s, which was an increase of 38.4% compared with the 1970s’. The total N deposition in different biomes is unbalanced. N deposition is only 38.0% of the global total in forest biomes; this is made up of 25.9%, 11.3, and 0.7% in tropical, temperate, and boreal forests, respectively. As N-limited biomes, there was little increase of N deposition in boreal forests. However, N deposition has increased by a total of 59.6% in tropical forests and croplands, which are N-rich biomes. Such characteristics may influence the effects on global carbon budgets.

Isotopic Monitoring of N2O Emissions from Wastewater Treatment: Evidence for N2O Production Associated with Anammox Metabolism?

NASA Astrophysics Data System (ADS)

Harris, E. J.; Wunderlin, P.; Joss, A.; Emmenegger, L.; Kipf, M.; Wolf, B.; Mohn, J.

2015-12-01

Microbial production is the major source of N2O, the strongest greenhouse gas produced within the nitrogen cycle, and the most important stratospheric ozone destructant released in the 21st century. Wastewater treatment is an important and growing source of N2O, with best estimates predicting N2O emissions from this sector will have increased by >25% by 2020. Novel treatment employing partial nitritation-anammox, rather than traditional nitrification-denitrification, has the potential to achieve a neutral carbon footprint due to increased biogas production - if N2O production accounts for <0.5-1% of total nitrogen turnover. As a further motivation for this research, microbial pathways identified from wastewater treatment can be applied to our understanding of N cycling in the natural environment. This study presents the first online isotopic measurements of offgas N2O from a partial-nitritation anammox reactor 1. The measured N2O isotopic composition - in particular the N2O isotopic site preference (SP = δ15Nα - δ15Nβ) - was used to understand N2O production pathways in the reactor. When N2O emissions peaked due to high dissolved oxygen concentrations, low SP showed that N2O was produced primarily via nitrifier denitrification by ammonia oxidizing bacteria (AOBs). N2O production by AOBs via NH2OH oxidation, in contrast, did not appear to be important under any conditions. Over the majority of the one-month measurement period, the measured SP was much higher than expected following our current understanding of N2O production pathways 2. SP reached 41‰ during normal operating conditions and achieved a maximum of 45‰ when nitrite was added under anoxic conditions. These results could be explained by unexpectedly strong heterotrophic N2O reduction despite low dissolved organic matter concentrations, or by an incomplete understanding of isotopic fractionation during N2O production from NH2OH oxidation by AOBs - however the explanation most consistent with all

O2 Herzberg State Reaction with N2: A Possible Source of Stratospheric N2O

NASA Technical Reports Server (NTRS)

Slanger, Tom G.; Copeland, Richard A.

1997-01-01

The goal of this one-year investigation was to determine whether N2O is formed in atmospherically significant quantities by the reaction of vibrationally excited levels of the O2((A3 Sigma(sub u)(sup +)) state with nitrogen. O2(A3 Sigma(sub u)(sup +)) is made throughout the upper stratosphere in considerable amounts by solar photoabsorption, and only a very small reactive yield is necessary for this mechanism to be a major N2O source. By long-term 245-252 nm irradiation of O2/N2 mixtures on- and off-resonance with absorption lines in the O2(A3 Sigma(sub u)(sup +) - X3 Sigma(sub g)(sup -)) transition, followed by N2O analysis by frequency-modulated diode laser absorption spectroscopy, we determined an upper limit for the N2O yield of the candidate reaction. This limit, 3 x 10(exp -5), eliminates O2(A3 Sigma(sub u)(sup +)) + N2 as a significant channel for the generation of stratospheric N2O. In further measurements, we established that N2O is stable under our photolysis conditions, showing that the small amounts of ozone generated from the reaction of O2(A) and O2 do not indirectly lead to destruction of N2O.

Method for measuring changes in the atmospheric O2/N2 ratio by a gas chromatograph equipped with a thermal conductivity detector

NASA Astrophysics Data System (ADS)

Tohjima, Yasunori

2000-06-01

We present a method for measuring changes in the atmospheric O2/N2 ratio based on data from a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). In this method, O2 and N2 in an air sample are separated on a column filled with molecular sieve 5A with H2 carrier gas. Since the separated O2 includes Ar, which has a retention time similar to that of O2, the (O2+Ar)/N2 ratio is actually measured. The change in the measured (O2+Ar)/N2 ratio can be easily converted to that in the O2/N2 ratio with a very small error based on the fact that the atmospheric Ar/N2 ratio is almost constant. The improvements to achieve the high-precision measurement include stabilization of the pressure at the GC column head and at the outlets of the TCD and the sample loop. Additionally, the precision is improved statistically by repeating alternate analyses of sample and a reference gas. The standard deviation of the replicate cycles of reference and sample analyses is about 18 per meg (corresponding to 3.8 parts per million (ppm) O2 in air). This means that the standard error is about 7 per meg (1.5 ppm O2 in air) for seven cycles of alternate analyses, which takes about 70 min. The response of this method is likely to have a 2% nonlinearity. Ambient air samples are collected under pressure in glass flasks equipped with two stopcocks sealed by Viton O-rings at both ends. Pressure depletion in the flask during the O2/N2 measurement does not cause any detectable change in the O2/N2 ratio, but the O2/N2 ratio in the flask was found to gradually decrease during the storage period. We also present preliminary results from air samples collected at Hateruma Island (latitude 24°03'N, longitude 123°49') from July 1997 through March 1999. The observed O2/N2 ratios clearly show a seasonal variation, increasing in spring and summer and decreasing in autumn and winter.

Daytime O/N2 Retrieval Algorithm for the Ionospheric Connection Explorer (ICON)

NASA Astrophysics Data System (ADS)

Stephan, Andrew W.; Meier, R. R.; England, Scott L.; Mende, Stephen B.; Frey, Harald U.; Immel, Thomas J.

2018-02-01

The NASA Ionospheric Connection Explorer Far-Ultraviolet spectrometer, ICON FUV, will measure altitude profiles of the daytime far-ultraviolet (FUV) OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) band emissions that are used to determine thermospheric density profiles and state parameters related to thermospheric composition; specifically the thermospheric column O/N2 ratio (symbolized as ΣO/N2). This paper describes the algorithm concept that has been adapted and updated from one previously applied with success to limb data from the Global Ultraviolet Imager (GUVI) on the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission. We also describe the requirements that are imposed on the ICON FUV to measure ΣO/N2 over any 500-km sample in daytime with a precision of better than 8.7%. We present results from orbit-simulation testing that demonstrates that the ICON FUV and our thermospheric composition retrieval algorithm can meet these requirements and provide the measurements necessary to address ICON science objectives.

Characterization of remote O2-plasma-enhanced CVD SiO2/GaN(0001) structure using photoemission measurements

NASA Astrophysics Data System (ADS)

Truyen, Nguyen Xuan; Ohta, Akio; Makihara, Katsunori; Ikeda, Mitsuhisa; Miyazaki, Seiichi

2018-01-01

The control of chemical composition and bonding features at a SiO2/GaN interface is a key to realizing high-performance GaN power devices. In this study, an ∼5.2-nm-thick SiO2 film has been deposited on an epitaxial GaN(0001) surface by remote O2-plasma-enhanced chemical vapor deposition (O2-RPCVD) using SiH4 and Ar/O2 mixture gases at a substrate temperature of 500 °C. The depth profile of chemical structures and electronic defects of the O2-RPCVD SiO2/GaN structures has been evaluated from a combination of SiO2 thinning examined by X-ray photoelectron spectroscopy (XPS) and the total photoelectron yield spectroscopy (PYS) measurements. As a highlight, we found that O2-RPCVD is effective for fabricating an abrupt SiO2/GaN interface.

A Novel Triple-Pulsed 2-micrometer Lidar for Simultaneous and Independent CO2 and H2O Column Measurement

NASA Technical Reports Server (NTRS)

Yu, Jirong; Singh, Upendra; Petros, Mulugeta; Refaat, Tamer

2015-01-01

The study of global warming needs precisely and accurately measuring greenhouse gases concentrations in the atmosphere. CO2 and H2O are important greenhouse gases that significantly contribute to the carbon cycle and global radiation budget on Earth. NRC Decadal Survey recommends a mission for Active Sensing of Carbon Dioxide (CO2) over Nights, Days and Seasons (ASCENDS). 2 micron laser is a viable IPDA transmitter to measure CO2 and H2O column density from space. The objective is to demonstrate a first airborne direct detection 2 micron IPDA lidar for CO2 and H2O measurements.

Infrared spectra of N2O-(ortho-D2)N and N2O-(HD)N clusters trapped in bulk solid parahydrogen.

PubMed

Lorenz, Britney D; Anderson, David T

2007-05-14

High-resolution infrared spectra of the clusters N2O-(ortho-D2)N and N2O-(HD)N, N=1-4, isolated in bulk solid parahydrogen at liquid helium temperatures are studied in the 2225 cm-1 region of the nu3 antisymmetric stretch of N2O. The clusters form during vapor deposition of separate gas streams of a precooled hydrogen mixture (ortho-D2para-H2 or HDpara-H2) and N2O onto a BaF2 optical substrate held at approximately 2.5 K in a sample-in-vacuum liquid helium cryostat. The cluster spectra reveal the N2O nu3 vibrational frequency shifts to higher energy as a function of N, and the shifts are larger for ortho-D2 compared to HD. These vibrational shifts result from the reduced translational zero-point energy for N2O solvated by the heavier hydrogen isotopomers. These spectra allow the N=0 peak at 2221.634 cm-1, corresponding to the nu3 vibrational frequency of N2O isolated in pure solid parahydrogen, to be assigned. The intensity of the N=0 absorption feature displays a strong temperature dependence, suggesting that significant structural changes occur in the parahydrogen solvation environment of N2O in the 1.8-4.9 K temperature range studied.

Development of an OClO Slant Column Product for the GOME-2 Sensors

NASA Astrophysics Data System (ADS)

Richter, Andreas; Wittrock, Folkard; Burrows, John P.

2016-04-01

Stratospheric ozone depletion by catalytic reactions involving halogens is one of the most prominent examples of anthropogenic impacts on the atmosphere. In spite of the rapid and successful international action to reduce emissions of CFCs and other ozone depleting substances leading to the Montreal Protocol and its amendments, ozone depletion in polar spring is still observed in both hemispheres on a regular basis. For the coming years, slow ozone recovery is expected but individual years will still see very low ozone columns depending on meteorology and possible interactions with climate change. Monitoring of both ozone and ozone depleting substances in the stratosphere remains a priority to ensure that the predicted reduction in halogen levels and recovery of ozone columns is taking place as predicted. One way to observe stratospheric chlorine activation is by measurements of OClO which can be detected by UV/visible remote sensing from the ground and from satellite. While the link between OClO levels and chlorine activation is complicated by the fact that a) OClO is not directly involved in ozone depletion but is produced by reaction of BrO and ClO and b) is rapidly photolysed at daylight, the long existing data series from both ground-based and satellite observations makes it an interesting tracer of chlorine activation. The GOME-2 instruments on the MetOp series of satellites are nadir viewing UV/vis spectrometers having the spectral coverage and resolution needed for Differential Optical Absorption Spectroscopy retrievals of OClO. With their combined lifetime of more than 15 years, they can provide a long-term data set. However, previous attempts to create an OClO product for GOME-2 suffered from large scatter in the OClO data and time-dependent offsets. Here we present an improved OClO slant column retrieval for the two instruments GOME2-A and GOME2-B. The data is shown to be of similar quality as for earlier instruments such as SCIAMACHY, and is consistent

Vibrational spectroscopy of NO + (H2O)n: Evidence for the intracluster reaction NO + (H2O)n --> H3O + (H2O)n - 2 (HONO) at n => 4

NASA Astrophysics Data System (ADS)

Choi, Jong-Ho; Kuwata, Keith T.; Haas, Bernd-Michael; Cao, Yibin; Johnson, Matthew S.; Okumura, Mitchio

1994-05-01

Infrared spectra of mass-selected clusters NO+(H2O)n for n=1 to 5 were recorded from 2700 to 3800 cm-1 by vibrational predissociation spectroscopy. Vibrational frequencies and intensities were also calculated for n=1 and 2 at the second-order Møller-Plesset (MP2) level, to aid in the interpretation of the spectra, and at the singles and doubles coupled cluster (CCSD) level energies of n=1 isomers were computed at the MP2 geometries. The smaller clusters (n=1 to 3) were complexes of H2O ligands bound to a nitrosonium ion NO+ core. They possessed perturbed H2O stretch bands and dissociated by loss of H2O. The H2O antisymmetric stretch was absent in n=1 and gradually increased in intensity with n. In the n=4 clusters, we found evidence for the beginning of a second solvation shell as well as the onset of an intracluster reaction that formed HONO. These clusters exhibited additional weak, broad bands between 3200 and 3400 cm-1 and two new minor photodissociation channels, loss of HONO and loss of two H2O molecules. The reaction appeared to go to completion within the n=5 clusters. The primary dissociation channel was loss of HONO, and seven vibrational bands were observed. From an analysis of the spectrum, we concluded that the n=5 cluster rearranged to form H3O+(H2O)3(HONO), i.e., an adduct of the reaction products.

Bis(acesulfamato-kappaO4)diaquabis(3-methylpyridine-kappaN)nickel(II).

PubMed

Dege, Necmi; Içbudak, Hasan; Adiyaman, Elif

2007-01-01

In the crystal structure of the title compound [systematic name: diaquabis(6-methyl-2,2-dioxo-1,2,3-oxathiazin-4-olato-kappaO4)bis(3-methylpyridine-kappaN)nickel(II)], [Ni(C4H4NO4S)2(C6H7N)2(H2O)2], the Ni(II) centre resides on a centre of symmetry and has a distorted octahedral geometry. The basal plane is formed by two carbonyl O atoms of two monodentate trans-oriented acesulfamate ligands and two trans aqua ligands. The axial positions in the octahedron are occupied by two N atoms of two trans pyridine ligands. Molecules are stacked in columns running along the a axis. There are pi-pi stacking interactions between the molecules in each column, with a distance of 3.623 (2) A between the centroids of the pyridine rings. There are also O-H...O interactions between the columns.

Studies of CW lasing action in CO2-CO, N2O-CO, CO2-H2O, and N2O-H2O mixtures pumped by blackbody radiation

NASA Technical Reports Server (NTRS)

Abel, Robert W.; Christiansen, Walter H.; Li, Jian-Guo

1988-01-01

A proof of principle experiment to evaluate the efficacy of CO and H2O in increasing the power output for N2O and CO2 lasing mixtures has been conducted and theoretically analyzed for a blackbody radiation-pumped laser. The results for N2O-CO, CO2-CO, N2O-H2O and CO2-H2O mixtures are presented. Additions of CO to the N2O lasant increased power up to 28 percent for N2O laser mixtures, whereas additions of CO to the CO2 lasant, and the addition of H2O to both the CO2 and N2O lasants, resulted in decreased output power.

Oceanic nitrogen cycling and N2O flux perturbations in the Anthropocene

NASA Astrophysics Data System (ADS)

Landolfi, A.; Somes, C. J.; Koeve, W.; Zamora, L. M.; Oschlies, A.

2017-08-01

There is currently no consensus on how humans are affecting the marine nitrogen (N) cycle, which limits marine biological production and CO2 uptake. Anthropogenic changes in ocean warming, deoxygenation, and atmospheric N deposition can all individually affect the marine N cycle and the oceanic production of the greenhouse gas nitrous oxide (N2O). However, the combined effect of these perturbations on marine N cycling, ocean productivity, and marine N2O production is poorly understood. Here we use an Earth system model of intermediate complexity to investigate the combined effects of estimated 21st century CO2 atmospheric forcing and atmospheric N deposition. Our simulations suggest that anthropogenic perturbations cause only a small imbalance to the N cycle relative to preindustrial conditions (˜+5 Tg N y-1 in 2100). More N loss from water column denitrification in expanded oxygen minimum zones (OMZs) is counteracted by less benthic denitrification, due to the stratification-induced reduction in organic matter export. The larger atmospheric N load is offset by reduced N inputs by marine N2 fixation. Our model predicts a decline in oceanic N2O emissions by 2100. This is induced by the decrease in organic matter export and associated N2O production and by the anthropogenically driven changes in ocean circulation and atmospheric N2O concentrations. After comprehensively accounting for a series of complex physical-biogeochemical interactions, this study suggests that N flux imbalances are limited by biogeochemical feedbacks that help stabilize the marine N inventory against anthropogenic changes. These findings support the hypothesis that strong negative feedbacks regulate the marine N inventory on centennial time scales.

[Effects of diurnal warming on soil N2O emission in soybean field].

PubMed

Hu, Zheng-Hua; Zhou, Ying-Ping; Cui, Hai-Ling; Chen, Shu-Tao; Xiao, Qi-Tao; Liu, Yan

2013-08-01

To investigate the impact of experimental warming on N2O emission from soil of soybean field, outdoor experiments with simulating diurnal warming were conducted, and static dark chamber-gas chromatograph method was used to measure N2O emission fluxes. Results indicated that: the diurnal warming did not change the seasonal pattern of N2O emissions from soil. In the whole growing season, comparing to the control treatment (CK), the warming treatment (T) significantly enhanced the N2O flux and the cumulative amount of N2O by 17.31% (P = 0.019), and 20.27% (P = 0.005), respectively. The significant correlations were found between soil N2O emission and soil temperature, moisture. The temperature sensitivity values of soil N2O emission under CK and T treatments were 3.75 and 4.10, respectively. In whole growing stage, T treatment significantly increased the crop aboveground and total biomass, the nitrate reductase activity, and total nitrogen in leaves, while significantly decreased NO3(-) -N content in leaves. T treatment significantly increased soil NO3(-) -N content, but had no significant effect on soil organic carbon and total nitrogen contents. The results of this study suggested that diurnal warming enhanced N2O emission from soil in soybean field.

Leachate treatment in landfills is a significant N2O source.

PubMed

Wang, Xiaojun; Jia, Mingsheng; Zhang, Chengliang; Chen, Shaohua; Cai, Zucong

2017-10-15

The importance of methane (CH 4 ) emissions from landfills has been extensively documented, while the nitrous oxide (N 2 O) emissions from landfills are considered negligible. In this study, three landfills were selected to measure CH 4 and N 2 O emissions using the static chamber method. Dongbu (DB) and Dongfu (DF) landfills, both located in Xiamen city, Fujian Province, were classified as sanitary. The former started to receive solid waste from Xiamen city in 2009, and the latter was closed in 2009. Nanjing (NJ) landfill, located in Nanjing county, Fujian Province, was classified as managed. Results showed that for the landfill reservoirs, CH 4 emissions were significant, while N 2 O emissions occurred mainly in operating areas (on average, 16.3 and 19.0mgN 2 Om -2 h -1 for DB and NJ landfills, respectively) and made a negligible contribution to the total greenhouse gas emissions in term of CO 2 equivalent. However, significant N 2 O emissions were observed in the leachate treatment systems of sanitary landfills and contributed 72.8% and 45.6% of total emissions in term of CO 2 equivalent in DB and DF landfills, respectively. The N 2 O emission factor (EF) of the leachate treatment systems was in the range of 8.9-11.9% of the removed nitrogen. The total N 2 O emissions from the leachate treatment systems of landfills in Xiamen city were estimated to be as high as 8.55gN 2 O-Ncapita -1 yr -1 . These results indicated that N 2 O emissions from leachate treatment systems of sanitary landfills were not negligible and should be included in national and/or local inventories of greenhouse gas emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

The vibration-rotation-tunneling levels of N2-H2O and N2-D2O.

PubMed

Wang, Xiao-Gang; Carrington, Tucker

2015-07-14

In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

NASA Astrophysics Data System (ADS)

Wang, Xiao-Gang; Carrington, Tucker

2015-07-01

In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

Sensitivity of terrestrial N2O emission to atmospheric nitrogen deposition

NASA Astrophysics Data System (ADS)

Ito, A.; Sudo, K.; Nishina, K.; Ishijima, K.; Inatomi, M. I.

2015-12-01

Terrestrial N2O emission is generated from several nitrogen sources including biological fixation, agricultural fertilizer, and atmospheric deposition. There remain large uncertainties how much N2O is produced from atmospheric deposition. This is a crosscutting issue between global warming and atmospheric pollution. In this study, we assessed the sensitivity of global terrestrial N2O emission to atmospheric deposition, using a process-based model VISIT. In the model, N2O emission is estimated separately for nitrification and denitrfication with the NGAS parameterization. The global simulations were conducted from 1901 to 2014 at spatial resolution of 0.5 degree. Atmospheric deposition of ammonium, NOy, and organic nitrogen simulated by the atmospheric chemistry model CHASER from the pre-industrial time to the present was used. Annual total nitrogen deposition was estimated to increase from 27 Tg N in 1901 to 77 Tg N in 2014. The total N2O emission was also estimated to increase in the period, but it was largely attributable to the increased emission from croplands. We need further investigations for the N2O emission from natural soils, which may be nitrogen-limited.

Trends of total water vapor column above the Arctic from satellites observations

NASA Astrophysics Data System (ADS)

Alraddawi, Dunya; Sarkissian, Alain; Keckhut, Philippe; Bock, Olivier; Claud, Chantal; Irbah, Abdenour

2016-04-01

Atmospheric water vapor (H2O) is the most important natural (as opposed to man-made) greenhouse gas, accounting for about two-thirds of the natural greenhouse effect. Despite this importance, its role in climate and its reaction to climate change are still difficult to assess. Many details of the hydrological cycle are poorly understood, such as the process of cloud formation and the transport and release of latent heat contained in the water vapor. In contrast to other important greenhouse gases like carbon dioxide (CO2) and methane, water vapor has a much higher temporal and spatial variability. Total precipitable water (TPW) or the total column of water vapor (TCWV) is the amount of liquid water that would result if all the water vapor in the atmospheric column of unit area were condensed. TCWV distribution contains valuable information on the vigor of the hydrological processes and moisture transport in the atmosphere. Measurement of TPW can be obtained based on atmospheric water vapor absorption or emission of radiation in the spectral range from UV to MW. TRENDS were found over the terrestrial Arctic by means of TCWV retrievals (using Moderate Resolution Imaging Spectro-radiometer (MODIS) near-infrared (2001-2015) records). More detailed approach was made for comparisons with ground based instruments over Sodankyla - Finland (TCWV from: SCIAMACHY 2003-2011, GOME-2A 2007-2011, SAOZ 2003-2011, GPS 2003-2011, MODIS 2003-2011)

Quantifying N2O reduction to N2 based on N2O isotopocules - validation with independent methods (helium incubation and 15N gas flux method)

NASA Astrophysics Data System (ADS)

Lewicka-Szczebak, Dominika; Augustin, Jürgen; Giesemann, Anette; Well, Reinhard

2017-02-01

Stable isotopic analyses of soil-emitted N2O (δ15Nbulk, δ18O and δ15Nsp = 15N site preference within the linear N2O molecule) may help to quantify N2O reduction to N2, an important but rarely quantified process in the soil nitrogen cycle. The N2O residual fraction (remaining unreduced N2O, rN2O) can be theoretically calculated from the measured isotopic enrichment of the residual N2O. However, various N2O-producing pathways may also influence the N2O isotopic signatures, and hence complicate the application of this isotopic fractionation approach. Here this approach was tested based on laboratory soil incubations with two different soil types, applying two reference methods for quantification of rN2O: helium incubation with direct measurement of N2 flux and the 15N gas flux method. This allowed a comparison of the measured rN2O values with the ones calculated based on isotopic enrichment of residual N2O. The results indicate that the performance of the N2O isotopic fractionation approach is related to the accompanying N2O and N2 source processes and the most critical is the determination of the initial isotopic signature of N2O before reduction (δ0). We show that δ0 can be well determined experimentally if stable in time and then successfully applied for determination of rN2O based on δ15Nsp values. Much more problematic to deal with are temporal changes of δ0 values leading to failure of the approach based on δ15Nsp values only. For this case, we propose here a dual N2O isotopocule mapping approach, where calculations are based on the relation between δ18O and δ15Nsp values. This allows for the simultaneous estimation of the N2O-producing pathways' contribution and the rN2O value.

Vertical Profiles as Observational Constraints on Nitrous Oxide (N2O) Emissions in an Agricultural Region

NASA Astrophysics Data System (ADS)

Pusede, S.; Diskin, G. S.

2015-12-01

We use diurnal variability in near-surface N2O vertical profiles to derive N2O emission rates. Our emissions estimates are ~3 times greater than are accounted for by inventories, a discrepancy in line with results from previous studies using different approaches. We quantify the surface N2O concentration's memory of local surface emissions on previous days to be 50-90%. We compare measured profiles both over and away from a dense N2O source region in the San Joaquin Valley, finding that profile shapes, diurnal variability, and changes in integrated near-surface column abundances are distinct according to proximity to source areas. To do this work, we use aircraft observations from the wintertime DISCOVER-AQ project in California's San Joaquin Valley, a region of intense agricultural activity.

Arctic Marine Water Isotope Characteristics: In-situ, Continuous Surface and Water Column Isoscapes (δ18O and δ2H) and Linkages into the Marine Food Web

NASA Astrophysics Data System (ADS)

Welker, J. M.; Klein, E. S.; Collins, E.; Iken, K.; Hopcroft, R. R.; Norcross, B.

2016-12-01

The Arctic is under going rapid and profound sea ice, temperature, food web, ocean current, precipitation and synoptic weather changes. Delineating these changes requires a suite of tools, especially those that have the ability to depict the interactive nature of the marine system. Understanding the marine water isotope cycle is paramount to recognizing the unique isotopic properties of this region and to characterize possibly the reorganization of the Arctic. The Arctic marine water isotope system has been primarily examined with shore-based stations and or episodic station sampling; without continuous surface water sampling in combination with station-specific water column and organismic measurements. New technologies that allow in situ and continuous water isotope measurements (vapor and liquid) and the integration of inorganic and organic water isotope geochemistry provide a means to reveal in more detail the fundamental traits of the Arctic marine water isotope system. In July and August of 2016, we are measuring seawater surface (8 m depth) isotopes (δ18O and δ2H) in-situ and continuously (Picarro CWS system) along a research transect (60oN to 77oN) from the Gulf of Alaska to the Arctic Ocean Basin. These continuous surface water isotope measurements are being combined with periodic water column isotope profiling and corresponding organic δ18O and δ2H measurements of pelagic and benthic organisms (microbes to fish) to depths of up to 2600m. We measured surface seawater δ18O that from -1‰ to -6‰; while seawater profiles followed vertical separation in the water column; possibly reflecting divergent currents of the Arctic. Station based δ18O and δ2H values of surface water did not vary by more than 1‰ δ18O over the course of our 24-36 hour sampling periods. The δ18O and δ2H values of marine organism throughout the water column and by trophic level will be analyzed and a seawater-food web model will be developed in addition to surface and water

Surface Nitrification: A Major Uncertainty in Marine N2O Emissions

NASA Technical Reports Server (NTRS)

Zamora, Lauren M.; Oschlies, Andreas

2014-01-01

The ocean is responsible for up to a third of total global nitrous oxide (N2O) emissions, but uncertainties in emission rates of this potent greenhouse gas are high (approaching 100%). Here we use a marine biogeochemical model to assess six major uncertainties in estimates of N2O production, thereby providing guidance in how future studies may most effectively reduce uncertainties in current and future marine N2O emissions. Potential surface N2O production from nitrification causes the largest uncertainty in N2O emissions (estimated up to approximately 1.6 Tg N/yr (sup -1) or 48% of modeled values), followed by the unknown oxygen concentration at which N2O production switches to N2O consumption (0.8 Tg N/yr (sup -1)or 24% of modeled values). Other uncertainties are minor, cumulatively changing regional emissions by less than 15%. If production of N2O by surface nitrification could be ruled out in future studies, uncertainties in marine N2O emissions would be halved.

(CaO)nIrO2 (n = 1, 2, 4) family: Chemical scissors effects of CaO on structural characteristics correlated to physical properties. Ab initio study

NASA Astrophysics Data System (ADS)

Matar, Samir F.; Etourneau, Jean

2017-11-01

Based on crystal chemistry analysis within Ca-Ir-O ternary, the generic (CaO)nIrO2 formula leading to CaIrO3 for n = 1, Ca2IrO4 for n = 2 and Ca4IrO6 for n = 4 actual chemical compounds show significant structural changes regarding the spatial arrangement of IrO6 octahedra whereby increasing amounts of CaO act as 'chemical scissor' decreasing the dimensionality of stacking octahedra from 3D (IrO2) to 0D (Ca4IrO6). This is accompanied by changes in the electronic structure investigated within density functional theory. Such changes are particularly exhibited by linear increase of Ir density of states at the Fermi level revealing increasing localization of d states with crystal field effects. Eventually only for Ca4IrO6 a magnetic instability occurs in non magnetic configuration. Spin polarized calculations lead to development of small magnitude but finite magnetization on Ir with M 0.50 μB totally polarized along minority spin channel ↓.

Operational trace gas column observations from GOME-2 on MetOp

NASA Astrophysics Data System (ADS)

Valks, Pieter; Hao, Nan; Pinardi, Gaia; Hedelt, Pascal; Liu, Song; Van Roozendael, Michel; De Smedt, Isabelle; Theys, Nicolas; Koukouli, MariLiza; Balis, Dimitris

2017-04-01

This contribution focuses on the operational GOME-2 trace gas column products developed in the framework of EUMETSAT's Satellite Application Facility on Atmospheric Composition Monitoring (AC-SAF). We present an overview of the retrieval algorithms for ozone, OClO, NO2, SO2 and formaldehyde, and we show examples of various applications such as air quality and climate monitoring, using observations from the GOME-2 instruments on MetOp-A and MetOp-B. Total ozone and the minor trace gas columns from GOME-2 are retrieved with the latest version 4.8 of the GOME Data Processor (GDP), which uses an optimized Differential Optical Absorption Spectroscopy (DOAS) algorithm, with air mass factor conversions based on the LIDORT model. Improved total and tropospheric NO2 columns are retrieved in the visible wavelength region between 425 and 497 nm. SO2 emissions from volcanic and anthropogenic sources can be measured by GOME-2 using the UV wavelength region around 320 nm. For formaldehyde, an optimal DOAS fitting window around 335 nm has been determined for GOME-2. The GOME-2 trace gas columns have reached the operational EUMETSAT product status, and are available to the users in near real time (within two hours after sensing by GOME-2). The use of trace gas observations from the GOME-2 instruments on MetOp-A and MetOp-B for air quality purposed will be illustrated, e.g. for South-East Asia and Europe. Furthermore, comparisons of the GOME-2 satellite observations with ground-based measurements will be shown. Finally, the use of GOME-2 trace-gas column data in the Copernicus Atmosphere Monitoring Service (CAMS) will be presented.

Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers?

NASA Astrophysics Data System (ADS)

Well, Reinhard; Eschenbach, Wolfram; Flessa, Heinz; von der Heide, Carolin; Weymann, Daniel

2012-08-01

contribution of different processes to the total N2O flux, apparently because these values were not only governed by individual pathways but eventually also by the spatial distribution of substrates and activity within the aquifers. These observations could be explained by the dynamics of N2O production, reduction and transport in water-saturated systems with heterogenic distribution of microbial activity and by a combination of diffusive and enzymatic isotope effects.

Investigation of N2O Production from 266 and 532 nm Laser Flash Photolysis of O3/N2/O2 Mixtures

NASA Technical Reports Server (NTRS)

Estupinan, E. G.; Nicovich, J. M.; Li, J.; Cunnold, D. M.; Wine, P. H.

2002-01-01

Tunable diode laser absorption spectroscopy has been employed to measure the amount of N2O produced from laser flash photolysis of O3/N2/O2 mixtures at 266 and 532 nm. In the 532 nm photolysis experiments very little N2O is observed, thus allowing an upper limit yield of 7 x 10(exp -8) to be established for the process O3 + N2 yield N2O + O2, where O3 is nascent O3 that is newly formed via O(3P(sub J)) + O2 recombination (with vibrational excitation near the dissociation energy of O3). The measured upper limit yield is a factor of approx. 600 smaller than a previous literature value and is approximately a factor of 10 below the threshold for atmospheric importance. In the 266 nm photolysis experiments, significant N2O production is observed and the N2O quantum yield is found to increase linearly with pressure over the range 100 - 900 Torr in air bath gas. The source of N2O in the 266 nm photolysis experiments is believed to be the addition reaction O(1D(sub 2)) + N2 + M yields (k(sub sigma)) N2O + M, although reaction of (very short-lived) electronically excited O3 with N2 cannot be ruled out by the available data. Assuming that all observed N2O comes from the O(1D(sub 2)) + N2 + M reaction, the following expression describes the temperature dependence of k(sub sigma) (in its third-order low-pressure limit) that is consistent with the N2O yield data: k(sub sigma) = (2.8 +/- 0.1) x 10(exp -36)(T/300)(sup -(0-88+0.36)) cm(sup 6) molecule(sup -2)/s, where the uncertainties are 2(sigma) and represent precision only. The accuracy of the reported rate coefficients at the 95% confidence level is estimated to be 30 - 40% depending on the temperature. Model calculations suggest that gas phase processes initiated by ozone absorption of a UV photon represent about 1.4% of the currently estimated global source strength of atmospheric N2O. However, these processes could account for a significant fraction of the oxygen mass-independent enrichment observed in atmospheric N2O, and

Comparison of Eight Years Total Column Ozone Retrievals form Brewer and Dobson Spectrophotometers in South Pole

NASA Astrophysics Data System (ADS)

Feng, K. H.; Moeini, O.; McElroy, C. T.; Evans, R. D.; Petropavlovskikh, I. V.

2015-12-01

Total column ozone measured by a Brewer Mark III spectrophotometer (#85) from 2008 to 2015 is compared to the data obtained from three different Dobson spectrophotometers (#80, #82 and #42) that have been operating in parallel with the Brewer at the Amundsen-Scott Station near the South Pole. Measurements are made using either direct sunlight or light from the moon (up to 2 weeks per month). The result of the comparison was used to assess the performance of the two instrument types and determine the stability of the measurement systems. Both instruments suffer from non-linearity due to the presence of instrumental stray light caused by the out-off-band radiations scattered from the optics within the instrument. Stray light results in an underestimated ozone column at large ozone path lengths. Since measurements made at the location of the station (Latitude 89.99o, Longitude -24.80o) have solar zenith angles of 66.5 degrees or greater, the issue of stray light is a particular concern.

Effects of Carbon and Cover Crop Residues on N2O and N2 Emissions

NASA Astrophysics Data System (ADS)

Burger, M.; Cooperman, Y.; Horwath, W. R.

2016-12-01

In Mediterranean climate, nitrous oxide emissions occurring with the first rainfall after the dry summer season can contribute up to 50% of agricultural systems' total annual emissions, but the drivers of these emissions have not been clearly identified, and there are only few measurements of atmospheric nitrogen (N2) production (denitrification) during these events. In lab incubations, we investigated N2O and N2 production, gross ammonification and nitrification, and microbial N immobilization with wet-up in soil from a vineyard that was previously fallow or where cover crop residue had been incorporated the previous spring. Before the first rainfall, we measured 120 mg dissolved organic carbon (DOC-C) kg-1 soil in the 0-5 cm layer of this vineyard, and after the rain 10 mg DOC-C kg-1, while nitrate levels before the rain were <5 mg N kg-1 in fallow and <10 mg N kg-1 in previously cover cropped soil. The N2O/N2 production was 2, 7, 9, and 86% in fallow, legume-grass mixture, rye, and legume cover cropped soil. The N2O/N2 ratio tended to increase with lower DOC (post-rain) levels in the soil. The results suggest that accumulated carbon in dry surface soil is the main driving factor of N2O and N2 emissions through denitrification with the first rainfall after prolonged dry periods.

Estimating Surface NO2 and SO2 Mixing Ratios from Fast-Response Total Column Observations and Potential Application to Geostationary Missions

EPA Science Inventory

Total-column nitrogen dioxide (NO2) data collected by a ground-based sun-tracking spectrometer system 21 (Pandora) and an photolytic-converter-based in-situ instrument collocated at NASA’s Langley Research Center in 22 Hampton, Virginia were analyzed to study the relationship bet...

Emissions of methane in Europe inferred by total column measurements

NASA Astrophysics Data System (ADS)

Wunch, D.; Deutscher, N. M.; Hase, F.; Notholt, J.; Sussmann, R.; Toon, G. C.; Warneke, T.

2017-12-01

Atmospheric total column measurements have been used to infer emissions of methane in urban centres around the world. These measurements have been shown to be useful for verifying city-scale bottom-up inventories, and they can provide both timely and sub-annual emission information. We will present our analysis of atmospheric total column measurements of methane and carbon monoxide to infer annual and seasonal regional emissions of methane within Europe using five long-running atmospheric observatories. These observatories are part of the Total Carbon Column Observing Network, part of a global network that has been carefully designed to measure these gases on a consistent scale. Our inferred emissions will then be used to evaluate gridded emissions inventories in the region.

N2O emissions from secondary clarifiers and their contribution to the total emissions of the WWTP.

PubMed

Mikola, Anna; Heinonen, Mari; Kosonen, Heta; Leppänen, Maarit; Rantanen, Pirjo; Vahala, Riku

2014-01-01

Recent studies have indicated that the emissions of nitrous oxide, N2O, constitute a major part of the carbon footprint of wastewater treatment plants (WWTPs). Denitrification occurring in the secondary clarifier basins has been observed by many researchers, but until now N2O emissions from secondary clarifiers have not been widely reported. The objective of this study was to measure the N2O emissions from secondary clarifiers and weigh the portion they could represent of the overall emissions at WWTPs. Online measurements over several days were carried out at four different municipal WWTPs in Finland in cold weather conditions (March) and in warm weather conditions (June-July). An attempt was made to define the conditions in which N2O emissions from secondary clarifiers may occur. It was evidenced that large amounts of N2O can be emitted from the secondary clarifiers, and that the emissions have long-term variation. It was assumed that part of the N2O released in secondary clarification was originally formed in the activated sludge basin. The emissions from secondary clarification thus seem to be dependent on conditions of the nitrification and denitrification accomplished in the denitrification-nitrification process and on the amount of sludge stored in the secondary clarifiers.

Photocatalytic activity of self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition

NASA Astrophysics Data System (ADS)

Shi, Pengjun; Li, Xibo; Zhang, Qiuju; Yi, Zao; Luo, Jiangshan

2018-04-01

A well-separated and oriented TiO2 nano-columns arrays with porous structure were fabricated by the oblique angle sputter deposition technique and subsequently annealing at 450 °C in Ar/O2 mixed atmosphere. The deposited substrate was firstly modified by a template of self-assembled close-packed arrays of 500 nm-diameter silica (SiO2) spheres. Scanning electronic microscopic (SEM) images show that the porous columnar nanostructure is formed as a result of the geometric shadowing effect and surface diffusion of the adatoms in oblique angle deposition (OAD). X-ray diffraction (XRD) measurements reveal that the physically OAD film with annealing treatment are generally mixed phase of rutile and anatase TiO2 polymorphic forms. The morphology induced absorbance and band gap tuning by different substrates was demonstrated by the UV–vis spectroscopy. The well-separated one-dimensional (1D) nano-columns array with specific large porous surface area is beneficial for charge separation in photocatalytic degradation. Compared with compact thin film, such self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition performed an enhanced visible light induced photocatalytic activity by decomposing methyl orange (MO) solution. The well-designed periodic array-structured porous TiO2 films by using modified patterned substrates has been demonstrated significantly increased absorption edge in the UV-visible light region with a narrower optical band gap, which are expected to be favorable for application in photovoltaic, lithium-ion insertion and photocatalytic, etc.

A New High-Resolution N2O Emission Inventory for China in 2008

NASA Astrophysics Data System (ADS)

Shang, Z.; Zhou, F.; Ciais, P.; Tao, S.; Piao, S.; Raymond, P. A.; He, C.; Li, B.; Wang, R.; Wang, X.; Peng, S.; Zeng, Z.; Chen, H.; Ying, N.; Hou, X.; Xu, P.

2014-12-01

The amount and geographic distribution of N2O emissions over China remain largely uncertain. Most of existing emission inventories use uniform emission factors (EFs) and the associated parameters and apply spatial proxies to downscale national or provincial data, resulting in the introduction of spatial bias. In this study, county-level and 0.1° × 0.1° gridded anthropogenic N2O emission inventories for China (PKU-N2O) in 2008 are developed based on high-resolution activity data and regional EFs and parameters. These new estimates are compared with estimates from EDGAR v4.2, GAINS-China, National Development and Reform Commission of China (NDRC), and with two sensitivity tests: one that uses high-resolution activity data but the default IPCC methodology (S1) and the other that uses regional EFs and parameters but starts from coarser-resolution activity data. The total N2O emissions are 2150 GgN2O/yr (interquartile range from 1174 to 2787 GgN2O/yr). Agriculture contributes 64% of the total, followed by energy (17%), indirect emissions (12%), wastes (5%), industry (2.8%), and wildfires (0.2%). Our national emission total is 17% greater than that of the EDGAR v4.2 global product sampled over China and is also greater than the GAINS-China, NDRC, and S1 estimates by 10%, 50%, and 17%, respectively. We also found that using uniform EFs and parameters or starting from national/provincial data causes systematic spatial biases compared to PKU-N2O. In addition, the considerable differences between the relative contributions of the six sectors across the six Agro-Climate Zones primarily reflect the different distributions of industrial activities and land use. Eastern China (8.7% area of China) is the largest contributor of N2O emissions and accounts for nearly 25% of the total. Spatial analysis also shows nonlinear relationships between N2O emission intensities and urbanization. Per-capita and per-GDP N2O emissions increase gradually with an increase in the urban

Tidal and spatial variability of nitrous oxide (N2O) in Sado estuary (Portugal)

NASA Astrophysics Data System (ADS)

Gonçalves, Célia; Brogueira, Maria José; Nogueira, Marta

2015-12-01

The estimate of the nitrous oxide (N2O) fluxes is fundamental to assess its impact on global warming. The tidal and spatial variability of N2O and the air-sea fluxes in the Sado estuary in July/August 2007 are examined. Measurements of N2O and other relevant environmental parameters (temperature, salinity, dissolved oxygen and dissolved inorganic nitrogen - nitrate plus nitrite and ammonium) were recorded during two diurnal tidal cycles performed in the Bay and Marateca region and along the estuary during ebb, at spring tide. N2O presented tidal and spatial variability and varied spatially from 5.0 nmol L-1 in Marateca region to 12.5 nmol L-1 in Sado river input. Although the Sado river may constitute a considerable N2O source to the estuary, the respective chemical signal discharge was rapidly lost in the main body of the estuary due to the low river flow during the sampling period. N2O varied with tide similarly between 5.2 nmol L-1 (Marateca) and 10.0 nmol L-1 (Sado Bay), with the maximum value reached two hours after flooding period. The influence of N2O enriched upwelled seawater (˜10.0 nmol L-1) was well visible in the estuary mouth and apparently represented an important contribution of N2O in the main body of Sado estuary. Despite the high water column oxygen saturation in most of Sado estuary, nitrification did not seem a relevant process for N2O production, probably as the concentration of the substrate, NH4+, was not adequate for this process to occur. Most of the estuary functioned as a N2O source, and only Marateca zone has acted as N2O sink. The N2O emission from Sado estuary was estimated to be 3.7 Mg N-N2O yr-1 (FC96) (4.4 Mg N-N2O yr-1, FRC01). These results have implications for future sampling and scaling strategies for estimating greenhouse gases (GHGs) fluxes in tidal ecosystems.

Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

NASA Astrophysics Data System (ADS)

Chen, Daixi; Habu, Daiki; Masubuchi, Yuji; Torii, Shuki; Kamiyama, Takashi; Kikkawa, Shinichi

2016-04-01

SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3-/O2-. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.

Quenching of I(2P1/2) by NO2, N2O4, and N2O.

PubMed

Kabir, Md Humayun; Azyazov, Valeriy N; Heaven, Michael C

2007-10-11

Quenching of excited iodine atoms (I(5p5, 2P1/2)) by nitrogen oxides are processes of relevance to discharge-driven oxygen iodine lasers. Rate constants at ambient and elevated temperatures (293-380 K) for quenching of I(2P1/2) atoms by NO2, N2O4, and N2O have been measured using time-resolved I(2P1/2) --> I(2P3/2) 1315 nm emission. The excited atoms were generated by pulsed laser photodissociation of CF3I at 248 nm. The rate constants for I(2P1/2) quenching by NO2 and N2O were found to be independent of temperature over the range examined with average values of (2.9 +/- 0.3) x 10(-15) and (1.4 +/- 0.1) x 10(-15) cm3 s(-1), respectively. The rate constant for quenching of I(2P1/2) by N2O4 was found to be (3.5 +/- 0.5) x 10(-13) cm3 s(-1) at ambient temperature.

Soil Nitrification and N2O Production: the connection with N concentration and Soil Water Content

NASA Astrophysics Data System (ADS)

Zhu-Barker, X.; Horwath, W. R.

2016-12-01

The development of mitigation strategies to reduce nitrous oxide (N2O) emission from soils is dependent on explicating the biophysical factors affecting different N2O production pathways. Ammonia oxidation and heterotrophic denitrification are the main pathways of N2O production, depending on soil conditions such as soil moisture content, oxygen (O2) content and N substrate. Many researchers have reported that N2O production increased as substrate concentration and soil moisture content increased. However, less understood is how N fertilizer concentration and moisture content interact to affect N2O production pathways. To investigate interaction and its effect on O2 consumption, we incubated three agricultural soils (clay, sandy loam, and peat) with different concentrations of (NH4)2SO4 (0-1000 µg N g-1) under 50 %, 75%, and 100% of water holding capacity. All treatments received 15N -KNO3 to bring the concentrations of NO3-_N in soils to 50 mg kg-1 soil and the NO3- pool to an enrichment of 10 atom% 15N. In all soils, the total amount of O2 consumption and N2O production increased as soil ammonical N concentration increased. The increased soil moisture significantly promoted N2O production in sandy loam and clay loam soils, compared to the peat soil. These results indicate that N2O production increased as substrate concentration increased likely due to the onset of O2 limitation caused by ammonia oxidation.

Global observations of BrO in the troposphere using GOME-2 satellite data

NASA Astrophysics Data System (ADS)

Theys, N.; van Roozendael, M.; Hendrick, F.; Xin, Y.; Isabelle, D.; Richter, A.; Mathias, B.; Quentin, E.; Johnston, P. V.; Kreher, K.; Martine, D.

2010-12-01

Measurements from the GOME-2 satellite instrument have been analyzed for tropospheric BrO using a residual technique that combines measured BrO columns and estimates of the stratospheric BrO content from a climatological approach driven by O3 and NO2 observations. Comparisons between the GOME-2 results and correlative data including ground-based BrO vertical columns and total BrO columns derived from SCIAMACHY nadir observations, present a good level of consistency. We show that the adopted technique enables to separate the stratospheric and tropospheric fractions of the measured total BrO columns and allows studying the BrO plumes in polar region in more detail. While several satellite BrO plumes can largely be explained by an influence of stratospheric descending air, we show that numerous tropospheric BrO hotspots are associated to regions with low tropopause heights as well. Elaborating on simulations using the p-TOMCAT tropospheric chemical transport model, this finding is found to be consistent with the mechanism of bromine release through sea salt aerosols production during blowing snow events. Outside the polar region, evidences are provided for a global tropospheric BrO background with columns of 1-3 x 1013 molec/cm2.

{μ-2-[(3-Amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1:2κ(5)O(1),O(6):N,N',O(1)}{2-[(3-amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1κ(3)N,N',O(1)}-μ-azido-1:2κ(2)N:N-azido-2κN-methanol-2κO-dinickel(II).

PubMed

Ghaemi, Akbar; Rayati, Saeed; Fayyazi, Kazem; Ng, Seik Weng; Tiekink, Edward R T

2012-08-01

Two distinct coordination geometries are found in the binuclear title complex, [Ni(2)(C(13)H(19)N(2)O(2))(2)(N(3))(2)(CH(3)OH)], as one Schiff base ligand is penta-dentate, coordinating via the anti-cipated oxide O, imine N and amine N atoms (as for the second, tridentate, ligand) but the oxide O is bridging and coordination also occurs through the meth-oxy O atom. The Ni(II) atoms are linked by a μ(2)-oxide atom and one end of a μ(2)-azide ligand, forming an Ni(2)ON core. The coordination geometry for the Ni(II) atom coordinated by the tridentate ligand is completed by the meth-oxy O atom derived from the penta-dentate ligand, with the resulting N(3)O(3) donor set defining a fac octa-hedron. The second Ni(II) atom has its cis-octa-hedral N(4)O(2) coordination geometry completed by the imine N and amine N atoms of the penta-dentate Schiff base ligand, a terminally coordinated azide N and a methanol O atom. The arrangement is stabilized by an intra-molecular hydrogen bond between the methanol H and the oxide O atom. Linear supra-molecular chains along the a axis are formed in the crystal packing whereby two amine H atoms from different amine atoms hydrogen bond to the terminal N atom of the monodentate azide ligand.

Constraining the H2 column density distribution at z ˜ 3 from composite DLA spectra

NASA Astrophysics Data System (ADS)

Balashev, S. A.; Noterdaeme, P.

2018-07-01

We present the detection of the average H2 absorption signal in the overall population of neutral gas absorption systems at z˜ 3 using composite absorption spectra built from the Sloan Digital Sky Survey-III damped Lyman α catalogue. We present a new technique to directly measure the H2 column density distribution function f_H_2(N) from the average H2 absorption signal. Assuming a power-law column density distribution, we obtain a slope β = -1.29 ± 0.06(stat) ± 0.10 (sys) and an incidence rate of strong H2 absorptions [with N(H2) ≳ 1018 cm-2] to be 4.0 ± 0.5(stat) ± 1.0 (sys) per cent in H I absorption systems with N(H I) ≥1020 cm-2. Assuming the same inflexion point where f_H_2(N) steepens as at z = 0, we estimate that the cosmological density of H2 in the column density range log N(H_2) (cm^{-2})= 18{-}22 is {˜ } 15 per cent of the total. We find one order of magnitude higher H2 incident rate in a sub-sample of extremely strong damped Lyman α absorption systems (DLAs) [log N(H I) (cm^{-2}) ≥ 21.7], which, together with the derived shape of f_H_2(N), suggests that the typical H I-H2 transition column density in DLAs is log N(H)(cm-2) ≳ 22.3 in agreement with theoretical expectations for the average (low) metallicity of DLAs at high-z.

Constraining the H2 column density distribution at z˜3 from composite DLA spectra

NASA Astrophysics Data System (ADS)

Balashev, S. A.; Noterdaeme, P.

2018-04-01

We present the detection of the average H2 absorption signal in the overall population of neutral gas absorption systems at z ˜ 3 using composite absorption spectra built from the Sloan Digital Sky Survey-III damped Lyman-α catalogue. We present a new technique to directly measure the H2 column density distribution function f_H_2(N) from the average H2 absorption signal. Assuming a power-law column density distribution, we obtain a slope β = -1.29 ± 0.06(stat) ± 0.10 (sys) and an incidence rate of strong H2 absorptions (with N(H2) ≳ 1018 cm-2) to be 4.0 ± 0.5(stat) ± 1.0 (sys) % in H I absorption systems with N(H I)≥1020 cm-2. Assuming the same inflexion point where f_H_2(N) steepens as at z = 0, we estimate that the cosmological density of H2 in the column density range log N(H_2) (cm^{-2})= 18-22 is ˜15% of the total. We find one order of magnitude higher H2 incident rate in a sub-sample of extremely strong DLAs (log N(H I) (cm^{-2}) ≥ 21.7), which, together with the the derived shape of f_H_2(N), suggests that the typical H I-H2 transition column density in DLAs is log N(H)(cm-2) ≳ 22.3 in agreement with theoretical expectations for the average (low) metallicity of DLAs at high-z.

Direct Imaging and First Principles Studies of Si3N4/SiO2 Interface

NASA Astrophysics Data System (ADS)

Walkosz, Weronika; Klie, Robert; Ogut, Serdar; Mikijelj, Bilijana; Pennycook, Stephen; Idrobo, Juan C.

2010-03-01

It is well known that the composition of the integranular films (IGFs) in sintered polycrystalline silicon nitride (Si3N4) ceramics controls many of their physical and mechanical properties. A considerable effort has been made to characterize these films on the atomic scale using both experimental and theoretical methods. In this talk, we present results from a combined atomic-resolution Z-contrast and annular bright field imaging, electron energy-loss spectroscopy, as well as ab initio studies of the interface between β-Si3N4 (10-10) and SiO2 intergranular film. Our results show that O replaces N at the interface between the two materials in agreement with our theoretical calculations and that N is present in the SiO2 IGF. Moreover, they indicate the presence of atomic columns completing Si3N4 open rings, which have not been observed experimentally at the recently imaged Si3N4/rare-earth oxides interfaces, but have been predicted theoretically on bare Si3N4 surfaces. The structural and electronic variations at the Si3N4/SiO2 interface will be discussed in detail, focusing in particular on bonding characteristics.

O2-O2 and O2-N2 collision-induced absorption mechanisms unravelled

NASA Astrophysics Data System (ADS)

Karman, Tijs; Koenis, Mark A. J.; Banerjee, Agniva; Parker, David H.; Gordon, Iouli E.; van der Avoird, Ad; van der Zande, Wim J.; Groenenboom, Gerrit C.

2018-05-01

Collision-induced absorption is the phenomenon in which interactions between colliding molecules lead to absorption of light, even for transitions that are forbidden for the isolated molecules. Collision-induced absorption contributes to the atmospheric heat balance and is important for the electronic excitations of O2 that are used for remote sensing. Here, we present a theoretical study of five vibronic transitions in O2-O2 and O2-N2, using analytical models and numerical quantum scattering calculations. We unambiguously identify the underlying absorption mechanism, which is shown to depend explicitly on the collision partner—contrary to textbook knowledge. This explains experimentally observed qualitative differences between O2-O2 and O2-N2 collisions in the overall intensity, line shape and vibrational dependence of the absorption spectrum. It is shown that these results can be used to discriminate between conflicting experimental data and even to identify unphysical results, thus impacting future experimental studies and atmospheric applications.

The denitrification paradox: The role of O2 in sediment N2O production

NASA Astrophysics Data System (ADS)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

Structural and optical properties of glancing angle deposited In2O3 columnar arrays and Si/In2O3 photodetector

NASA Astrophysics Data System (ADS)

Mondal, A.; Shougaijam, B.; Goswami, T.; Dhar, J. C.; Singh, N. K.; Choudhury, S.; Chattopadhay, K. K.

2014-04-01

Ordered and perpendicular columnar arrays of In2O3 were synthesized on conducting ITO electrode by a simple glancing angle deposition (GLAD) technique. The as-deposited In2O3 columns were investigated by field emission gun-scanning electron microscope (FEG-SEM). The average length and diameter of the columns were estimated ˜400 nm and ˜100 nm, respectively. The morphology of the structure was examined by transmission electron microscopy (TEM). X-ray diffraction (XRD) analysis shows the polycrystalline nature of the sample which was verified by selective area electron diffraction (SAED) analysis. The growth mechanism and optical properties of the columns were also discussed. Optical absorption shows that In2O3 columns have a high band to band transition at ˜3.75 eV. The ultraviolet and green emissions were obtained from the In2O3 columnar arrays. The P-N junction was formed between In2O3 and P-type Si substrate. The GLAD synthesized In2O3 film exhibits low current conduction compared to In2O3 TF. However, the Si/GLAD-In2O3 detector shows ˜1.5 times enhanced photoresponsivity than that of Si/In2O3 TF.

Structural, electronic, and magnetic properties of Y(n)O (n=2-14) clusters: Density functional study.

PubMed

Yang, Zhi; Xiong, Shi-Jie

2008-09-28

The geometries stability, electronic properties, and magnetism of Y(n)O clusters up to n=14 are systematically studied with density functional theory. In the lowest-energy structures of Y(n)O clusters, the equilibrium site of the oxygen atom gradually moves from an outer site of the cluster, via a surface site, and finally, to an interior site as the number of the Y atoms increases from 2 to 14. Starting from n=12, the O atom falls into the center of the cluster with the Y atoms forming the outer frame. The results show that clusters with n=2, 4, 8, and 12 are more stable than their respective neighbors, and that the total magnetic moments of Y(n)O clusters are all quite small except Y(12)O cluster. The lowest-energy structure of Y(12)O cluster is a perfect icosahedron with a large magnetic moment 6mu(B). In addition, we find that the total magnetic moments are quenched for n=2, 6, and 8 due to the closed-shell electronic configuration. The calculated ionization potentials and electron affinities are in good agreement with the experimental results, which imply that the present theoretical treatments are satisfactory.

Stratospheric column NO2 anomalies over Russia related to the 2011 Arctic ozone hole

NASA Astrophysics Data System (ADS)

Aheyeva, Viktoryia; Gruzdev, Aleksandr; Elokhov, Aleksandr; Grishaev, Mikhail; Salnikova, Natalia

2013-04-01

We analyze data of spectrometric measurements of stratospheric column NO2 contents at mid- and high-latitude stations of Zvenigorod (55.7°N, Moscow region), Tomsk (56.5°N, West Siberia), and Zhigansk (66.8°N, East Siberia). Measurements are done in visual spectral range with zenith-viewing spectrometers during morning and evening twilights. Alongside column NO2 contents, vertical profiles of NO2 are retrieved at the Zvenigorod station. Zvenigorod and Zhigansk are the measurement stations within the Network for the Detection of Atmospheric Composition Change (NDACC). For interpretation of results of analysis of NO2 data, data of Ozone Monitoring Instrument measurements of total column ozone and rawinsonde data are also analyzed and back trajectories calculated with the help of HYSPLIT trajectory model are used. Significant negative anomalies in stratospheric NO2 columns accompanied by episodes of significant cooling of the stratosphere and decrease in total ozone were observed at the three stations in the winter-spring period of 2011. Trajectory analysis shows that the anomalies were caused by the transport of stratospheric air from the region of the ozone hole observed that season in the Arctic. Although negative NO2 anomalies due to the transport from the Arctic were also observed in some other years, the anomalies in 2011 have had record magnitudes. Analysis of NO2 vertical profiles at Zvenigorod shows that the NO2 anomaly in 2011 compared to other years anomalies was additionally contributed by the denitrification of the Arctic lower stratosphere. NO2 profiles show that a certain degree of the denitrification probably survived even after the ozone hole.

Characterization of the N2O isotopic composition (15N, 18O and N2O isotopomers) emitted from incubated Amazon forest soils. Implications for the global N2O isotope budget

NASA Astrophysics Data System (ADS)

Pérez, T.; García, D.; Trumbore, S.; Tyler, S.; de Camargo, P.; Moreira, M.; Piccolo, M.; Park, S.; Boering, K.; Cerri, C.

2003-04-01

Tropical rain forest soils are the largest natural source of N2O to the atmosphere. Uncertainty in the signature of this source limits the utility of isotopes in constraining the global N2O budget. Differentiating the relative contribution of nitrification and denitrification to the emitted N2O using stable isotopes has been difficult due to the lack of enrichment factors values for each process measured in situ. We have devised a method for measuring enrichment factors using soil incubation experiments. We selected three Amazon rain forest soils: (1) Clay and (2) Sandy from Santarem, Pará State, and (3) Sandy from Nova Vida Farm, Rondonia State, Brazil. The enrichment factor values for nitrification and denitrification are: -97.8±4.2 and -9.9±3.8 per mil for clay Santarem soil, -86.8±4.3 and -45.2±4.5 per mil for sandy Santarem soil and-112.6±3.8 and -10.4±3.5 per mil for Nova Vida Farm soils, respectively. Our results show that enrichment factors for both processes differ with soil texture and location. The enrichment factors for nitrification are significantly smaller than the range reported in the literature (-66 to -42 per mil). Also, the enrichment factors for the Santarem soils (clay and sandy) differ significantly implying that soil texture (which will affect the soil air filled pore space at a given water content) is influencing the bacteria isotopic discrimination. However, the enrichment factors for the Santarem clay sand Nova Vida sandy soils do not differ by much. This suggests that the enrichment factors not only can be affected by texture but also by the microbial fauna present in these soils. We also determined the measurement of the N2O positional dependence. N2O is a linear molecule with two nitrogen atoms. The 15N isotope can be located in either the central nitrogen (alpha position) or in the terminal nitrogen (beta position). The isotopomer site preference (15N alpha - 15N beta) can be used to differentiate processes of production and

Hydrogen bonding in microsolvation: photoelectron imaging and theoretical studies on Au(x)(-)-(H2O)(n) and Au(x)(-)-(CH3OH)(n) (x = 1, 2; n = 1, 2) complexes.

PubMed

Wu, Xia; Tan, Kai; Tang, Zichao; Lu, Xin

2014-03-14

We have combined photoelectron velocity-map imaging (VMI) spectroscopy and theoretical calculations to elucidate the geometry and energy properties of Aux(-)(Solv)n clusters with x = 1, 2; n = 1, 2; and Solv = H2O and CH3OH. Besides the blue-shifted vertical electron detachment energies (VDEs) of the complexes Au1,2(-)(Solv)n with the increase of the solvation number (n), we independently probed two distinct Au(-)(CH3OH)2 isomers, which combined with MP2/aug-cc-pVTZ(pp) calculations represent a competition between O···H-O hydrogen bonds (HBs) and Au···H-O nonconventional hydrogen bonds (NHBs). Complementary calculations provide the total binding energies of the low-energy isomers. Moreover, the relationship between the total binding energies and total VDEshift is discussed. We found that the Au1,2(-) anions exhibit halide-analogous behavior in microsolvation. These findings also demonstrate that photoelectron velocity map imaging spectroscopy with the aid of the ab initio calculations is an effective tool for investigating weak-interaction complexes.

N2O molecular tagging velocimetry

NASA Astrophysics Data System (ADS)

ElBaz, A. M.; Pitz, R. W.

2012-03-01

A new seeded velocity measurement technique, N2O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide "laughing gas" is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N2O to O(1D) that subsequently reacts with N2O to form NO. O2 fluorescence induced by the ArF laser "writes" the original position of the NO line. After a time delay, the shifted NO line is "read" by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N2O in air, ˜1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800-1200 ppm of NO for 190-750 K at 1 atm and 850-1000 ppm of NO for 0.25-1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N2O MTV method amenable to low- and high-speed air flow measurements. The N2O MTV technique is demonstrated in air jet to measure its velocity profile. The N2O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N2O with O(1D) from N2O photodissociation and thus does not depend on the bulk gas composition.

Potassium (2,2'-bipyridine-κN,N')bis-(carbonato-κO,O')cobaltate(III) dihydrate.

PubMed

Wang, Jian-Fei; Lin, Jian-Li

2010-09-30

In the title compound, K[Co(CO(3))(2)(C(10)H(8)N(2))]·2H(2)O, the Co(III) atom is coordinated by two bipyridine N atoms and four O atoms from two bidentate chelating carbonate anions, and thus adopts a distorted octa-hedral N(2)O(4) environment. The [Co(bipy)(CO(3))(2)](-) (bipy is 2,2'-bipyridine) -units are stacked along [100] via π-π stacking inter-actions, with inter-planar distances between the bipyridine rings of 3.36 (4) and 3.44 (6) Å, forming chains. Classical O-H⋯O hydrogen-bonding inter-actions link the chains, forming channels along (100) in which the K(+) ions reside and leading to a three-dimensional supra-molecular architecture.

The MOVPE growth mechanism of catalyst-free self-organized GaN columns in H2 and N2 carrier gases

NASA Astrophysics Data System (ADS)

Wang, Xue; Jahn, Uwe; Ledig, Johannes; Wehmann, Hergo-H.; Mandl, Martin; Straßburg, Martin; Waag, Andreas

2013-12-01

Columnar structures of III-V semiconductors recently attract considerable attention because of their potential applications in novel optoelectronic and electronic devices. In the present study, the mechanisms for the growth of catalyst-free self-organized GaN columns on sapphire substrate by metal organic vapor phase epitaxy have been thoroughly investigated. The growth behaviours are strongly affected by the choice of carrier gas. If pure nitrogen is used, Ga droplets are able to accumulate on the top of columns during growth, and they are converted into a high quality GaN layer during the cool down phase due to nitridation. Hydrogen as the carrier gas can improve the optical quality of the overall GaN columns substantially, and in addition increase the vertical growth rate. In this case, no indication of Ga droplets could be detected. Furthermore, silane doping during the growth promotes the vertical growth in both cases either pure nitrogen or pure hydrogen as the carrier gas.

Conversion of nitrogen oxides in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures subjected to a dc corona discharge

NASA Astrophysics Data System (ADS)

Dors, Mirosław; Mizeraczyk, Jerzy

1996-10-01

This paper concerns the influence of a direct current (dc) corona discharge on production and reduction of NO, NO2 and N2O in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures. The corona discharge was generated in a needle-to-plate reactor. The positively polarized electrode consisted of 7 needles. The grounded electrode was a stainless steel plate. The gas flow rate through the reactor was varied from 28 to 110 cm3/s. The time-averaged discharge current ranged from 0 to 6 mA. It was found that in the N2:O2:CO2 mixture the corona discharge produced NO, NO2 and N2O. In the N2:O2:CO2:NO2 mixture the reduction of NO2 was between 6-56%, depending on the concentration of O2, gas flow rate and corona discharge current. The NO2 reduction was accompanied by production of NO and N2O. The results show that efficient reduction of nitrogen oxides by a corona discharge cannot be expected in the mixtures containing N2 and O2 if reducing additives are not employed.

Infrared spectra of seeded hydrogen clusters: (para-H2)N-N2O and (ortho-H2)N-N2O, N = 2-13.

PubMed

Tang, Jian; McKellar, A R W

2005-09-15

High-resolution infrared spectra of clusters containing para-H2 and/or ortho-H2 and a single nitrous oxide molecule are studied in the 2225-cm(-1) region of the upsilon1 fundamental band of N2O. The clusters are formed in pulsed supersonic jet expansions from a cooled nozzle and probed using a tunable infrared diode laser spectrometer. The simple symmetric rotor-type spectra generally show no resolved K structure, with prominent Q-branch features for ortho-H2 but not para-H2 clusters. The observed vibrational shifts and rotational constants are reported. There is no obvious indication of superfluid effects for para-H2 clusters up to N=13. Sharp transitions due to even larger clusters are observed, but no definite assignments are possible. Mixed (para-H2)N-(ortho-H2)M-N2O cluster line positions can be well predicted by linear interpolation between the corresponding transitions of the pure clusters.

Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules

NASA Astrophysics Data System (ADS)

Buchen, Caroline; Well, Reinhard; Flessa, Heinz; Fuß, Roland; Helfrich, Mirjam; Lewicka-Szczebak, Dominika

2017-04-01

Grassland break-up due to grassland renewal and grassland conversion to cropland can lead to a flush of mineral nitrogen from decomposition of the old grass sward and the decomposition of soil organic matter. Moreover, increased carbon and nitrogen mineralisation can result in enhanced nitrous oxide (N2O) emissions. As N2O is known to be an important greenhouse gas and a major precursor for ozone depletion, its emissions need to be mitigated by adjusting agricultural management practices. Therefore, it is necessary to understand the N2O processes involved, as well as the contribution of N2O reduction to N2. Apart from the widely used 15N gas flux method, natural abundance isotopic analysis of the four most abundant isotopocules of N2O species is a promising alternative to assess N2O production pathways. We used stable isotope analyses of soil-emitted N2O (δ18ON2O, δ15NN2Obulk and δ15NN2OSP= intramolecular distribution of 15N within the linear N2O molecule) with an isotopocule mapping approach to simultaneously estimate the magnitude of N2O reduction to N2 and the fraction of N2O originating from the bacterial denitrification pathway or fungal denitrification and/or nitrification. This approach is based on endmember areas of isotopic values for the N2O produced from different sources reported in the literature. For this purpose, we calculated two main scenarios with different assumptions for N2O produced: N2O is reduced to N2 before residual N2O is mixed with N2O of various sources (Scenario a) and vice versa (Scenario b). Based on this, we applied seven different scenario variations, where we evaluated the range of possible values for the potential N2O production pathways (heterotrophic bacterial denitrification and/or nitrifier denitrification and fungal denitrification and/or nitrification). This was done by using a range of isotopic endmember values and assuming different fractionation factors of N2O reduction in order to find the most reliable scenario

The ratio of N(C18O) and AV in Chamaeleon I and III-B. Using 2MASS and SEST

NASA Astrophysics Data System (ADS)

Kainulainen, J.; Lehtinen, K.; Harju, J.

2006-02-01

We investigate the relationship between the C18O column density and the visual extinction in Chamaeleon I and in a part of the Chamaeleon III molecular cloud. The C18O column densities, N(C18O), are calculated from J=1{-}0 rotational line data observed with the SEST telescope. The visual extinctions, A_V, are derived using {JHK} photometry from the 2MASS survey and the NICER color excess technique. In contrast with the previous results of Hayakawa et al. (2001, PASJ, 53, 1109), we find that the average N(C18O)/AV ratios are similar in Cha I and Cha III, and lie close to values derived for other clouds, i.e. N(C18O) ≈ 2 × 1014 cm-2 ( AV - 2 ). We find, however, clear deviations from this average relationship towards individual clumps. Larger than average N(C18O)/AV ratios can be found in clumps associated with the active star forming region in the northern part of Cha I. On the other hand, some regions in the relatively quiescent southern part of Cha I show smaller than average N(C18O)/AV ratios and also very shallow proportionality between N(C18O) and A_V. The shallow proportionality suggests that C18O is heavily depleted in these regions. As the degree of depletion is proportional to the gas density, these regions probably contain very dense, cold cores, which do not stand out in CO mappings. A comparison with the dust temperature map derived from the ISO data shows that the most prominent of the potentially depleted cores indeed coincides with a dust temperature minimum. It seems therefore feasible to use N(C18O) and AV data together for identifying cold, dense cores in large scale mappings.

Life on N2O: deciphering the ecophysiology of N2O respiring bacterial communities in a continuous culture.

PubMed

Conthe, Monica; Wittorf, Lea; Kuenen, J Gijs; Kleerebezem, Robbert; van Loosdrecht, Mark C M; Hallin, Sara

2018-04-01

Reduction of the greenhouse gas N 2 O to N 2 is a trait among denitrifying and non-denitrifying microorganisms having an N 2 O reductase, encoded by nosZ. The nosZ phylogeny has two major clades, I and II, and physiological differences among organisms within the clades may affect N 2 O emissions from ecosystems. To increase our understanding of the ecophysiology of N 2 O reducers, we determined the thermodynamic growth efficiency of N 2 O reduction and the selection of N 2 O reducers under N 2 O- or acetate-limiting conditions in a continuous culture enriched from a natural community with N 2 O as electron acceptor and acetate as electron donor. The biomass yields were higher during N 2 O limitation, irrespective of dilution rate and community composition. The former was corroborated in a continuous culture of Pseudomonas stutzeri and was potentially due to cytotoxic effects of surplus N 2 O. Denitrifiers were favored over non-denitrifying N 2 O reducers under all conditions and Proteobacteria harboring clade I nosZ dominated. The abundance of nosZ clade II increased when allowing for lower growth rates, but bacteria with nosZ clade I had a higher affinity for N 2 O, as defined by μ max /K s . Thus, the specific growth rate is likely a key factor determining the composition of communities living on N 2 O respiration under growth-limited conditions.

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

NASA Astrophysics Data System (ADS)

Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

Octa-akis(4-amino-pyridine)-1κN,2κN-aqua-2κO-μ-carbonato-1:2κO,O':O''-dinickel(II) dichloride penta-hydrate.

PubMed

Fun, Hoong-Kun; Sinthiya, A; Jebas, Samuel Robinson; Ravindran Durai Nayagam, B; Alfred Cecil Raj, S

2008-10-18

In the title compound, [Ni(2)(CO(3))(C(5)H(6)N(2))(8)(H(2)O)]Cl(2)·5H(2)O, one of the the Ni(II) ions is six-coordinated in a distorted octa-hedral geometry, with the equatorial plane defined by four pyridine N atoms from four amino-pyridine ligands, the axial positions being occupied by one water O and a carbonate O atom. The other Ni(II) ion is also six-coordinated, by four other pyridine N atoms from four other amino-pyridine ligands and two carbonate O atoms to complete a distorted octa-hedral geometry. In the crystal structure, mol-ecules are linked into an infinite three-dimensional network by O-H⋯O, N-H⋯Cl, N-H⋯O, O-H⋯N, C-H⋯O, C-H⋯N and C/N-H⋯π inter-actions involving the pyridine rings.

Ionospheric TEC, thermospheric cooling and Σ[O/N2] compositional changes during the 6-17 March 2012 magnetic storm interval (CAWSES II)

NASA Astrophysics Data System (ADS)

Verkhoglyadova, O. P.; Tsurutani, B. T.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Paxton, L. J.

2014-08-01

A series of four geomagnetic storms (the minimum SYM-H~-148 nT) occurred during the March 6-17, 2012 in the ascending phase of the solar cycle 24. This interval was selected by CAWSES II for its campaign. The GPS total electron content (TEC) database and JPL's Global Ionospheric Maps (GIM) were used to study vertical TEC (VTEC) for different local times and latitude ranges. The largest response to geomagnetic activity is shown in increases of the low-latitude dayside VTEC. Several GPS sites feature post-afternoon VTEC “bite-outs”. During Sudden Impulse (SI+) event on March 8th a peak daytime VTEC restores to about quiet-time values. It is shown that the TIMED/SABER zonal flux of nitric oxide (NO) infrared cooling radiation correlates well with auroral heating. A factor of ~5 cooling increase is noted in some storms. The cooling radiation intensifies in the auroral zone and spreads towards the equator. Effects of the storm appear at lower latitudes ~18.6 h later. The column density ratio Σ[O/N2] is analyzed based on TIMED/GUVI measurements. Both increases (at low latitudes) and decreases (from auroral to middle latitudes) in the ratio occurs during the geomagnetic storms. We suggest that the column density ratio could be enhanced at low to middle latitudes on the dayside partially due to the superfountain effect (atomic oxygen uplift due to ion-neutral drag). It is suggested that decreases in the Σ[O/N2] ratio at high to middle-latitudes may be caused by high thermospheric temperatures. During SI+s, there is an increase in Σ[O/N2] ratio at auroral latitudes.

DOAS-based total column ozone retrieval from Phaethon system

NASA Astrophysics Data System (ADS)

Gkertsi, F.; Bais, A. F.; Kouremeti, N.; Drosoglou, Th; Fountoulakis, I.; Fragkos, K.

2018-05-01

This study introduces the measurement of the total ozone column using Differential Optical Absorption Spectroscopy (DOAS) analysis of direct-sun spectra recorded by the Phaethon system. This methodology is based on the analysis of spectra relative to a reference spectrum that has been recorded by the same instrument. The slant column density of ozone associated with the reference spectrum is derived by Langley extrapolation. Total ozone data derived by Phaethon over two years in Thessaloniki are compared with those of a collocated, well-maintained and calibrated, Brewer spectrophotometer. When the retrieval of total ozone is based on the absorption cross sections of (Paur and Bass, 1984) at 228 K, Phaethon shows an average overestimation of 1.85 ± 1.86%. Taking into account the effect of the day-to-day variability of stratospheric temperature on total ozone derived by both systems, the bias is reduced to 0.94 ± 1.26%. The sensitivity of the total ozone retrieval to changes in temperature is larger for Phaethon than for Brewer.

Closed-loop 15N measurement of N2O and its isotopomers for real-time greenhouse gas tracing

NASA Astrophysics Data System (ADS)

Slaets, Johanna; Mayr, Leopold; Heiling, Maria; Zaman, Mohammad; Resch, Christian; Weltin, Georg; Gruber, Roman; Dercon, Gerd

2016-04-01

Quantifying sources of nitrous oxide is essential to improve understanding of the global N cycle and to develop climate-smart agriculture, as N2O has a global warming potential 300 times higher than CO2. The isotopic signature and the intramolecular distribution (site preference) of 15N are powerful tools to trace N2O, but the application of these methods is limited as conventional methods cannot provide continuous and in situ data. Here we present a method for closed-loop, real time monitoring of the N2O flux, the isotopic signature and the intramolecular distribution of 15N by using off-axis integrated cavity output spectroscopy (ICOS, Los Gatos Research). The developed method was applied to a fertilizer inhibitor experiment, in which N2O emissions were measured on undisturbed soil cores for three weeks. The treatments consisted of enriched urea-N (100 kg urea-N/ha), the same fertilizer combined with the nitrification inhibitor nitrapyrin (375 g/100 kg urea), and control cores. Monitoring the isotopic signature makes it possible to distinguish emissions from soil and fertilizer. Characterization of site preference could additionally provide a tool to identify different microbial processes leading to N2O emissions. Furthermore, the closed-loop approach enables direct measurement on site and does not require removal of CO2 and H2O. Results showed that 75% of total N2O emissions (total=11 346 μg N2O-N/m2) in the fertilized cores originated from fertilizer, while only 55% of total emissions (total=2 450 μg N2ON/m2) stemmed from fertilizer for the cores treated with nitrapyrin. In the controls, N2O derived from soil was only 40% of the size of the corresponding pool from the fertilized cores, pointing towards a priming effect on the microbial community from the fertilizer and demonstrating the bias that could be introduced by relying on non-treated cores to estimate soil emission rates, rather than using the isotopic signature. The site preference increased linearly

Decreased N2O reduction by low soil pH causes high N2O emissions in a riparian ecosystem.

PubMed

Van den Heuvel, R N; Bakker, S E; Jetten, M S M; Hefting, M M

2011-05-01

Quantification of harmful nitrous oxide (N(2)O) emissions from soils is essential for mitigation measures. An important N(2)O producing and reducing process in soils is denitrification, which shows deceased rates at low pH. No clear relationship between N(2)O emissions and soil pH has yet been established because also the relative contribution of N(2)O as the denitrification end product decreases with pH. Our aim was to show the net effect of soil pH on N(2)O production and emission. Therefore, experiments were designed to investigate the effects of pH on NO(3)(-) reduction, N(2)O production and reduction and N(2) production in incubations with pH values set between 4 and 7. Furthermore, field measurements of soil pH and N(2)O emissions were carried out. In incubations, NO(3)(-) reduction and N(2) production rates increased with pH and net N(2)O production rate was highest at pH 5. N(2)O reduction to N(2) was halted until NO(3)(-) was depleted at low pH values, resulting in a built up of N(2)O. As a consequence, N(2)O:N(2) production ratio decreased exponentially with pH. N(2)O reduction appeared therefore more important than N(2)O production in explaining net N(2)O production rates. In the field, a negative exponential relationship for soil pH against N(2)O emissions was observed. Soil pH could therefore be used as a predictive tool for average N(2)O emissions in the studied ecosystem. The occurrence of low pH spots may explain N(2)O emission hotspot occurrence. Future studies should focus on the mechanism behind small scale soil pH variability and the effect of manipulating the pH of soils. © 2011 Blackwell Publishing Ltd.

Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1).

PubMed

Li, Xiang; Wang, Haopeng; Bowen, Kit H

2010-10-14

The hydrated nucleoside anions, uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1), have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine(-)(H(2)O)(1) and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1

NASA Astrophysics Data System (ADS)

Li, Xiang; Wang, Haopeng; Bowen, Kit H.

2010-10-01

The hydrated nucleoside anions, uridine-(H2O)n=0-2, cytidine-(H2O)n=0-2, and thymidine-(H2O)n=0,1, have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine-(H2O)1 and its calculated value in the companion article by S. Kim and H. F. Schaefer III.

Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil

PubMed Central

Win, Khin Thuzar; Shibata, Akira; Yamamoto, Akinori; Sano, Tomohito; Hirono, Yuhei

2018-01-01

A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions. PMID:29394272

Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil.

PubMed

Oo, Aung Zaw; Sudo, Shigeto; Akiyama, Hiroko; Win, Khin Thuzar; Shibata, Akira; Yamamoto, Akinori; Sano, Tomohito; Hirono, Yuhei

2018-01-01

A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions.

K-shell photoabsorption coefficients of O2, CO2, CO, and N2O

NASA Technical Reports Server (NTRS)

Barrus, D. M.; Blake, R. L.; Burek, A. J.; Chambers, K. C.; Pregenzer, A. L.

1979-01-01

The total photoabsorption coefficient has been measured from 500 to 600 eV around the K edge of oxygen in gases O2, CO2, CO, and N2O by means of a gold continuum source and crystal spectrometer with better than 1-eV resolution. The cross sections are dominated by discrete molecular-orbital transitions below the K-edge energy. A few Rydberg transitions were barely detectable. Broad shape resonances appear at or above the K edge. Additional broad, weak features above the K edge possibly arise from shake up. Quantitative results are given that have about 10% accuracy except on the very strong peaks. All the measured features are discussed in relation to other related measurements and theory.

Relationship Between Column-Density and Surface Mixing Ratio: Statistical Analysis of O3 and NO2 Data from the July 2011 Maryland DISCOVER-AQ Mission

NASA Technical Reports Server (NTRS)

Flynn, Clare; Pickering, Kenneth E.; Crawford, James H.; Lamsol, Lok; Krotkov, Nickolay; Herman, Jay; Weinheimer, Andrew; Chen, Gao; Liu, Xiong; Szykman, James;

Sunflower N2O emissions under two different water regimes in Mediterranean climate

NASA Astrophysics Data System (ADS)

Monaco, Eugenia; Vitale, Luca; Di Tommasi, Paul; Tedeschi, Anna; Tosca, Maurizio; Magliulo, Vincenzo

2017-04-01

Human activities are altering the atmospheric greenhouse gases (GHGs) concentration with negative effects on global climate and environment. Cropland represents about 12 % of earth's surface and largely contribute to GHGs production, in particular N2O, due to a massive use of nitrogen fertilization. In particular, agriculture and intensive livestock farming may significantly affect biogeochemical cycles included nitrogen cycle. However, it is often difficult to predict the total amount of fluxes caused by agricultural management, which impact on both the whole agro-ecosystem. The objective of the experiment was to evaluate soil N2O fluxes under two different irrigation managements. The experimental trial was conducted in a farm in surrounding of Naples, southern Italy. The crop monitored was sunflower for biomass uses. Two irrigation levels were performed: returning 100% (optimal irrigation) and 50% (deficit irrigation) of soil field capacity for the layer 0.0-0.50 m. 314 Kg ha-1 of urea fertilizer was supplied in two times: at sowing and 40 days later. Before sowing, six autochambers were inserted 3 cm into the soil and connected to a gas chromatograph and a scanning apparatus. A program for chambers' management was implemented to monitor soil N2O fluxes measured different times of the day. Biometric parameters such as LAI, root depth, above- and below-ground biomass were monitored during the experiment. Results shows that soil N2O fluxes were affected by irrigation regime; in particular, the deficit irrigation determined lower N2O fluxes compared to optimal irrigation but the total biomass production and yield were comparable between the two water regimes. So low input farm management could be take in account to reduce the total N2O emission and maintain at the same time high productivity level in terms of biomass and yield. Keywords: N2O fluxes, Irrigation schedule, sunflower

Comparison of GOME tropospheric NO2 columns with NO2 profiles deduced from ground-based in situ measurements

NASA Astrophysics Data System (ADS)

Schaub, D.; Boersma, K. F.; Kaiser, J. W.; Weiss, A. K.; Folini, D.; Eskes, H. J.; Buchmann, B.

2006-08-01

Nitrogen dioxide (NO2) vertical tropospheric column densities (VTCs) retrieved from the Global Ozone Monitoring Experiment (GOME) are compared to coincident ground-based tropospheric NO2 columns. The ground-based columns are deduced from in situ measurements at different altitudes in the Alps for 1997 to June 2003, yielding a unique long-term comparison of GOME NO2 VTC data retrieved by a collaboration of KNMI (Royal Netherlands Meteorological Institute) and BIRA/IASB (Belgian Institute for Space Aeronomy) with independently derived tropospheric NO2 profiles. A first comparison relates the GOME retrieved tropospheric columns to the tropospheric columns obtained by integrating the ground-based NO2 measurements. For a second comparison, the tropospheric profiles constructed from the ground-based measurements are first multiplied with the averaging kernel (AK) of the GOME retrieval. The second approach makes the comparison independent from the a priori NO2 profile used in the GOME retrieval. This allows splitting the total difference between the column data sets into two contributions: one that is due to differences between the a priori and the ground-based NO2 profile shapes, and another that can be attributed to uncertainties in both the remaining retrieval parameters (such as, e.g., surface albedo or aerosol concentration) and the ground-based in situ NO2 profiles. For anticyclonic clear sky conditions the comparison indicates a good agreement between the columns (n=157, R=0.70/0.74 for the first/second comparison approach, respectively). The mean relative difference (with respect to the ground-based columns) is -7% with a standard deviation of 40% and GOME on average slightly underestimating the ground-based columns. Both data sets show a similar seasonal behaviour with a distinct maximum of spring NO2 VTCs. Further analysis indicates small GOME columns being systematically smaller than the ground-based ones. The influence of different shapes in the a priori and

Chip-based molecularly imprinted monolithic capillary array columns coated GO/SiO2 for selective extraction and sensitive determination of rhodamine B in chili powder.

PubMed

Zhai, Haiyun; Huang, Lu; Chen, Zuanguang; Su, Zihao; Yuan, Kaisong; Liang, Guohuan; Pan, Yufang

2017-01-01

A novel solid-phase extraction chip embedded with array columns of molecularly imprinted polymer-coated silanized graphene oxide (GO/SiO2-MISPE) was established to detect trace rhodamine B (RB) in chili powder. GO/SiO2-MISPE monolithic columns for RB detection were prepared by optimizing the supporting substrate, template, and polymerizing monomer under mild water bath conditions. Adsorption capacity and specificity, which are critical properties for the application of the GO/SiO2-MISPE monolithic column, were investigated. GO/SiO2-MIP was examined by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy. The recovery and the intraday and interday relative standard deviations for RB ranged from 83.7% to 88.4% and 2.5% to 4.0% and the enrichment factors were higher than 110-fold. The chip-based array columns effectively eliminated impurities in chili powder, indicating that the chip-based GO/SiO2-MISPE method was reliable for RB detection in food samples using high-performance liquid chromatography. Accordingly, this method has direct applications for monitoring potentially harmful dyes in processed food. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of Madden-Julian Oscillation (MJO) on global distribution of total water vapor and column ozone

NASA Astrophysics Data System (ADS)

Fathurochman, Irvan; Lubis, Sandro W.; Setiawan, Sonni

2017-01-01

The Madden-Julian Oscillation (MJO) is the leading mode of intra-seasonal variability in the tropical troposphere, characterized by an eastward moving ‘pulse’ of cloud and rainfall near the equator. In this study, total precipitable water (TPW) and total column ozone (TCO) datasets from ECMWF ERA-Interim reanalysis were used to analyse the impact of the MJO on the distribution of water vapor and column ozone in the tropics from 1979 to 2013. The results show that seasonal variations of TPW modulated by the MJO are maximized in the tropics of about 10°S-10°N during boreal winter, while the variation in TCO is maximized in the mid-latitudes of about 30°S - 40°N in the same season. The composite analysis shows that MJO modulates TPW and TCO anomalies eastward across the globe. The underlying mechanism of the MJO’s impact on TPW is mainly associated with variation of tropical convection modulated by the MJO, while the underlying mechanism of the MJO’s impact on TCO is mainly associated with an intra-seasonal variability of tropopause height modulated by the MJO activity. This knowledge helps to improve the prediction skill of the intra-seasonal variation of water vapor and column ozone in the tropics during boreal winter.

Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n.

PubMed

Höckendorf, Robert F; Hao, Qiang; Sun, Zheng; Fox-Beyer, Brigitte S; Cao, Yali; Balaj, O Petru; Bondybey, Vladimir E; Siu, Chi-Kit; Beyer, Martin K

2012-04-19

The chemistry of (H(2)O)(n)(•-), CO(2)(•-)(H(2)O)(n), and O(2)(•-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(•-) to O(2)(•-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(•-) with CH(3)SH as well as CO(2)(•-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters. © 2012 American Chemical Society

High-Accuracy Measurements of Total Column Water Vapor From the Orbiting Carbon Observatory-2

NASA Technical Reports Server (NTRS)

Nelson, Robert R.; Crisp, David; Ott, Lesley E.; O'Dell, Christopher W.

2016-01-01

Accurate knowledge of the distribution of water vapor in Earth's atmosphere is of critical importance to both weather and climate studies. Here we report on measurements of total column water vapor (TCWV) from hyperspectral observations of near-infrared reflected sunlight over land and ocean surfaces from the Orbiting Carbon Observatory-2 (OCO-2). These measurements are an ancillary product of the retrieval algorithm used to measure atmospheric carbon dioxide concentrations, with information coming from three highly resolved spectral bands. Comparisons to high-accuracy validation data, including ground-based GPS and microwave radiometer data, demonstrate that OCO-2 TCWV measurements have maximum root-mean-square deviations of 0.9-1.3mm. Our results indicate that OCO-2 is the first space-based sensor to accurately and precisely measure the two most important greenhouse gases, water vapor and carbon dioxide, at high spatial resolution [1.3 x 2.3 km(exp. 2)] and that OCO-2 TCWV measurements may be useful in improving numerical weather predictions and reanalysis products.

Microwave dielectric properties of BaO-2CeO{sub 2}-nTiO{sub 2} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sreemoolanadhan, H.; Sebastian, M.T.; Ratheesh, R.

2004-11-01

The BaO-2CeO{sub 2}-nTiO{sub 2} ceramics with n=3, 4 and 5 have been prepared with CeO{sub 2} as starting material. The ceramics have been characterized using scanning electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopy techniques. The microwave dielectric properties have been measured using standard dielectric resonator techniques. BaO-2CeO{sub 2}-3TiO{sub 2} (123), BaO-2CeO{sub 2}-4TiO{sub 2} (124) and BaO-2CeO{sub 2}-5TiO{sub 2} (125) ceramics showed dielectric constants of 38, 27 and 32, respectively. All the ceramics showed fairly good unloaded Q-factors. 124 and 125 compounds exhibited low {tau}f values, while 123 showed a high {tau}f value.

A new fully automated FTIR system for total column measurements of greenhouse gases

NASA Astrophysics Data System (ADS)

Geibel, M. C.; Gerbig, C.; Feist, D. G.

2010-10-01

This article introduces a new fully automated FTIR system that is part of the Total Carbon Column Observing Network (TCCON). It will provide continuous ground-based measurements of column-averaged volume mixing ratio for CO2, CH4 and several other greenhouse gases in the tropics. Housed in a 20-foot shipping container it was developed as a transportable system that could be deployed almost anywhere in the world. We describe the automation concept which relies on three autonomous subsystems and their interaction. Crucial components like a sturdy and reliable solar tracker dome are described in detail. The automation software employs a new approach relying on multiple processes, database logging and web-based remote control. First results of total column measurements at Jena, Germany show that the instrument works well and can provide parts of the diurnal as well as seasonal cycle for CO2. Instrument line shape measurements with an HCl cell suggest that the instrument stays well-aligned over several months. After a short test campaign for side by side intercomaprison with an existing TCCON instrument in Australia, the system will be transported to its final destination Ascension Island.

Using satellite measurements of N2O to remove dynamical variability from HCl measurements

NASA Astrophysics Data System (ADS)

Stolarski, Richard S.; Douglass, Anne R.; Strahan, Susan E.

2018-04-01

Column HCl measurements show deviations from the expected slow decline following the regulation of chlorine-containing compounds by the Montreal Protocol. We use the simultaneous measurements of N2O and HCl by the Microwave Limb Sounder (MLS) instrument on the Aura satellite to examine this problem. We find that the use of N2O measurements at a specific altitude to represent the impact of dynamical variability on HCl results in a derived linear trend in HCl that is negative (ranging from -2.5 to 5.3 % decade-1) at all altitudes between 68 and 10 hPa. These trends are at or near 2σ statistical significance at all pressure levels between 68 and 10 hPa. This shows that analysis of simultaneous measurements of several constituents is a useful approach to identify small trends from data records that are strongly influenced by dynamical interannual variability.

Marine N2O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

NASA Astrophysics Data System (ADS)

Battaglia, G.; Joos, F.

2018-01-01

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent; yet global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2-dependent by-product from nitrification in the Bern3D ocean model. A large model ensemble is used to probabilistically constrain modern and to project marine N2O production for a low (Representative Concentration Pathway (RCP)2.6) and high GHG (RCP8.5) scenario extended to A.D. 10,000. Water column N2O and surface ocean partial pressure N2O data serve as constraints in this Bayesian framework. The constrained median for modern N2O production is 4.5 (±1σ range: 3.0 to 6.1) Tg N yr-1, where 4.5% stems from denitrification. Modeled denitrification is 65.1 (40.9 to 91.6) Tg N yr-1, well within current estimates. For high GHG forcing, N2O production decreases by 7.7% over this century due to decreasing organic matter export and remineralization. Thereafter, production increases slowly by 21% due to widespread deoxygenation and high remineralization. Deoxygenation peaks in two millennia, and the global O2 inventory is reduced by a factor of 2 compared to today. Net denitrification is responsible for 7.8% of the long-term increase in N2O production. On millennial timescales, marine N2O emissions constitute a small, positive feedback to climate change. Our simulations reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.

Comparing N2O emissions at varying N rates from irrigated and rainfed corn in the US Midwest

NASA Astrophysics Data System (ADS)

Millar, N.; Kahmark, K.; Basso, B.; Robertson, G. P.

2011-12-01

Global N2O emissions from agriculture are estimated to be ~2.8 Pg CO2e yr-1 accounting for 60% of total anthropogenic emissions. N2O is the largest contributor to the GHG burden of cropping systems in the US, with annual estimated emissions of ~0.5 Tg primarily due to N fertilizer inputs and other soil management activities. Currently 23 million acres of corn, soybean and wheat are irrigated annually in the US with increased N2O emissions due to the practice likely under-reported in GHG inventories. Here we compare N2O emissions and yield from irrigated and rainfed corn at varying N rates between 0 and 246 kg N ha-1 from the Kellogg Biological Station in SW Michigan. Initial results show that N2O emissions increase with increasing N rate and are significantly higher from irrigated corn compared to rainfed corn at the same N rate. At increasing N rates daily emissions following an irrigation event were between 2.4 - 77.5 g N2O-N ha-1 from irrigated corn and 1.6 - 13.0 g N2O-N ha-1 from rainfed corn. Emissions data from automated and static chambers will be presented and trade-offs between N2O emissions, N fertilizer rate, crop yield and irrigation practice will be evaluated from an environmental and economic standpoint.

Characterization of Water Coordination to Ferrous Nitrosyl Complexes with fac-N2O, cis-N2O2, and N2O3 Donor Ligands.

PubMed

McCracken, John; Cappillino, Patrick J; McNally, Joshua S; Krzyaniak, Matthew D; Howart, Michael; Tarves, Paul C; Caradonna, John P

2015-07-06

Electron paramagnetic resonance (EPR) experiments were done on a series of S = (3)/2 ferrous nitrosyl model complexes prepared with chelating ligands that mimic the 2-His-1-carboxylate facial triad iron binding motif of the mononuclear nonheme iron oxidases. These complexes formed a comparative family, {FeNO}(7)(N2Ox)(H2O)3-x with x = 1-3, where the labile coordination sites for the binding of NO and solvent water were fac for x = 1 and cis for x = 2. The continuous-wave EPR spectra of these three complexes were typical of high-spin S = (3)/2 transition-metal ions with resonances near g = 4 and 2. Orientation-selective hyperfine sublevel correlation (HYSCORE) spectra revealed cross peaks arising from the protons of coordinated water in a clean spectral window from g = 3.0 to 2.3. These cross peaks were absent for the {FeNO}(7)(N2O3) complex. HYSCORE spectra were analyzed using a straightforward model for defining the spin Hamiltonian parameters of bound water and showed that, for the {FeNO}(7)(N2O2)(H2O) complex, a single water conformer with an isotropic hyperfine coupling, Aiso = 0.0 ± 0.3 MHz, and a dipolar coupling of T = 4.8 ± 0.2 MHz could account for the data. For the {FeNO}(7)(N2O)(H2O)2 complex, the HYSCORE cross peaks assigned to coordinated water showed more frequency dispersion and were analyzed with discrete orientations and hyperfine couplings for the two water molecules that accounted for the observed orientation-selective contour shapes. The use of three-pulse electron spin echo envelope modulation (ESEEM) data to quantify the number of water ligands coordinated to the {FeNO}(7) centers was explored. For this aspect of the study, HYSCORE spectra were important for defining a spectral window where empirical integration of ESEEM spectra would be the most accurate.

The earthworm gut: an ideal habitat for ingested N2O-producing microorganisms.

PubMed

Horn, Marcus A; Schramm, Andreas; Drake, Harold L

2003-03-01

The in vivo production of nitrous oxide (N(2)O) by earthworms is due to their gut microbiota, and it is hypothesized that the microenvironment of the gut activates ingested N(2)O-producing soil bacteria. In situ measurement of N(2)O and O(2) with microsensors demonstrated that the earthworm gut is anoxic and the site of N(2)O production. The gut had a pH of 6.9 and an average water content of approximately 50%. The water content within the gut decreased from the anterior end to the posterior end. In contrast, the concentration of N(2)O increased from the anterior end to the mid-gut region and then decreased along the posterior part of the gut. Compared to the soil in which worms lived and fed, the gut of the earthworm was highly enriched in total carbon, organic carbon, and total nitrogen and had a C/N ratio of 7 (compared to a C/N ratio of 12 in soil). The aqueous phase of gut contents contained up to 80 mM glucose and numerous compounds that were indicative of anaerobic metabolism, including up to 9 mM formate, 8 mM acetate, 3 mM lactate, and 2 mM succinate. Compared to the soil contents, nitrite and ammonium were enriched in the gut up to 10- and 100-fold, respectively. The production of N(2)O by soil was induced when the gut environment was simulated in anoxic microcosms for 24 h (the approximate time for passage of soil through the earthworm). Anoxia, high osmolarity, nitrite, and nitrate were the dominant factors that stimulated the production of N(2)O. Supplemental organic carbon had a very minimal stimulatory effect on the production of N(2)O, and addition of buffer or ammonium had essentially no effect on the initial N(2)O production rates. However, a combination of supplements yielded rates greater than that obtained mathematically for single supplements, suggesting that the maximum rates observed were due to synergistic effects of supplements. Collectively, these results indicate that the special microenvironment of the earthworm gut is ideally suited

Effects of cover crops incorporation and nitrogen fertilization on N2O and CO2 emissions

NASA Astrophysics Data System (ADS)

Kandel, T. P.; Gowda, P. H.; Northup, B. K.; DuPont, J.; Somenahally, A. C.; Rocateli, A.

2017-12-01

In this study, we measured N2O and CO2 fluxes from plots planted to hairy vetch (winter cover crop) and broadleaf vetch (spring cover crop) as N sources for the following crabgrass (summer forage crop) in El Reno, Oklahoma, USA. Comparisons also included 0 and 60 kg ha-1 mineral N fertilizer supplied as dry urea. No significant N2O fluxes were observed during rapid growing periods of cover crops (March-April, 2017), however, large fluxes were observed after hairy vetch incorporation. Immediately after the hairy vetch biomass incorporation, large rainfall events were recorded. The fluxes subsided gradually with drying soil condition but were enhanced after every consecutive rainfall events. A rainfall induced flux measuring up to 8.2 kg N2O ha-1 day-1 was observed after 26 days of biomass incorporation. In total, 29 kg N2O ha-1 (18 kg N ha-1) was emitted within a month after biomass incorporation from hairy vetch plots. Growth of broadleaf vetch was poor and N2O fluxes were also lower. Similarly, plots fertilized with 60 kg N ha-1 had significant fluxes of N2O but the magnitude was much lower than the hairy vetch plots. Dynamics of N2O and CO fluxes correlated strongly. The results thus indicated that although cover crops may provide many environmental/agronomic benefits such as N fixation, soil carbon built-up, weed suppression and erosion control, high N2O emissions may dwarf these benefits.

Assessment of errors and biases in retrievals of X CO2, X CH4, X CO, and X N2O from a 0.5 cm –1 resolution solar-viewing spectrometer

DOE PAGES

Hedelius, Jacob K.; Viatte, Camille; Wunch, Debra; ...

2016-08-03

Bruker™ EM27/SUN instruments are commercial mobile solar-viewing near-IR spectrometers. They show promise for expanding the global density of atmospheric column measurements of greenhouse gases and are being marketed for such applications. They have been shown to measure the same variations of atmospheric gases within a day as the high-resolution spectrometers of the Total Carbon Column Observing Network (TCCON). However, there is little known about the long-term precision and uncertainty budgets of EM27/SUN measurements. In this study, which includes a comparison of 186 measurement days spanning 11 months, we note that atmospheric variations of X gas within a single day aremore » well captured by these low-resolution instruments, but over several months, the measurements drift noticeably. We present comparisons between EM27/SUN instruments and the TCCON using GGG as the retrieval algorithm. In addition, we perform several tests to evaluate the robustness of the performance and determine the largest sources of errors from these spectrometers. We include comparisons of X CO2, X CH4, X CO, and X N2O. Specifically we note EM27/SUN biases for January 2015 of 0.03, 0.75, –0.12, and 2.43 % for X CO2, X CH4, X CO, and X N2O respectively, with 1 σ running precisions of 0.08 and 0.06 % for X CO2 and X CH4 from measurements in Pasadena. We also identify significant error caused by nonlinear sensitivity when using an extended spectral range detector used to measure CO and N 2O.« less

Visible spectrum photofragmentation of O{sub 3}{sup −}(H{sub 2}O){sub n}, n ≤ 16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehman, Julia H.; Lineberger, W. Carl, E-mail: wcl@jila.colorado.edu

2014-10-21

Photofragmentation of ozonide solvated in water clusters, O{sub 3}{sup −}(H{sub 2}O){sub n}, n ≤ 16, has been studied as a function of photon energy as well as the degree of solvation. Using mass selection, the effect of the presence of the solvent molecule on the O{sub 3}{sup −} photodissociation process is assessed one solvent molecule at a time. The O{sub 3}{sup −} acts as a visible light chromophore within the water cluster, namely the O{sub 3}{sup −}(H{sub 2}O) total photodissociation cross-section exhibits generally the same photon energy dependence as isolated O{sub 3}{sup −} throughout the visible wavelength range studied (430–620more » nm). With the addition of a single solvent molecule, new photodissociation pathways are opened, including the production of recombined O{sub 3}{sup −}. As the degree of solvation of the parent anion increases, recombination to O{sub 3}{sup −}-based products accounts for close to 40% of photoproducts by n = 16. The remainder of the photoproducts exist as O{sup −}-based; no O{sub 2}{sup −}-based products are observed. Upper bounds on the O{sub 3}{sup −} solvation energy (530 meV) and the O{sup −}-OO bond dissociation energy in the cluster (1.06 eV) are derived.« less

Gas entrapment and microbial N2O reduction reduce N2O emissions from a biochar-amended sandy clay loam soil

PubMed Central

Harter, Johannes; Guzman-Bustamante, Ivan; Kuehfuss, Stefanie; Ruser, Reiner; Well, Reinhard; Spott, Oliver; Kappler, Andreas; Behrens, Sebastian

2016-01-01

Nitrous oxide (N2O) is a potent greenhouse gas that is produced during microbial nitrogen transformation processes such as nitrification and denitrification. Soils represent the largest sources of N2O emissions with nitrogen fertilizer application being the main driver of rising atmospheric N2O concentrations. Soil biochar amendment has been proposed as a promising tool to mitigate N2O emissions from soils. However, the underlying processes that cause N2O emission suppression in biochar-amended soils are still poorly understood. We set up microcosm experiments with fertilized, wet soil in which we used 15N tracing techniques and quantitative polymerase chain reaction (qPCR) to investigate the impact of biochar on mineral and gaseous nitrogen dynamics and denitrification-specific functional marker gene abundance and expression. In accordance with previous studies our results showed that biochar addition can lead to a significant decrease in N2O emissions. Furthermore, we determined significantly higher quantities of soil-entrapped N2O and N2 in biochar microcosms and a biochar-induced increase in typical and atypical nosZ transcript copy numbers. Our findings suggest that biochar-induced N2O emission mitigation is based on the entrapment of N2O in water-saturated pores of the soil matrix and concurrent stimulation of microbial N2O reduction resulting in an overall decrease of the N2O/(N2O + N2) ratio. PMID:28008997

Bis(2,2'-bipyridyl-κN,N')(carbonato-κO,O')cobalt(III) bromide trihydrate.

PubMed

Ma, Peng-Tao; Wang, Yu-Xia; Zhang, Guo-Qian; Li, Ming-Xue

2007-12-06

The title complex, [Co(CO(3))(C(10)H(8)N(2))(2)]Br·3H(2)O, is isostructural with the chloride analogue. The six-coordinated octahedral [Co(2,2'-bipy)(2)CO(3)](+) cation (2,2'-bipy is 2,2'-bipyrid-yl), bromide ion and water mol-ecules are linked together via O-H⋯Br and O-H⋯O hydrogen bonds, generating a one-dimensional chain.

Expansion of antimonato polyoxovanadates with transition metal complexes: (Co(N3C5H15)2)2[{Co(N3C5H15)2}V15Sb6O42(H2O)]·5H2O and (Ni(N3C5H15)2)2[{Ni(N3C5H15)2}V15Sb6O42(H2O)]·8H2O.

PubMed

Antonova, Elena; Näther, Christian; Kögerler, Paul; Bensch, Wolfgang

2012-02-20

Two new polyoxovanadates (Co(N(3)C(5)H(15))(2))(2)[{Co(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·5H(2)O (1) and (Ni(N(3)C(5)H(15))(2))(2)[{Ni(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·8H(2)O (2) (N(3)C(5)H(15) = N-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V(15)Sb(6)O(42)(H(2)O)](6-) shell displays the main structural motif, which is strongly related to the {V(18)O(42)} archetype cluster. Both compounds crystallize in the triclinic space group P1 with a = 14.3438(4), b = 16.6471(6), c = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and V = 4401.4(2) Å(3) (1) and a = 14.5697(13), b = 15.8523(16), c = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and V = 4533.0(7) Å(3) (2). In the structure of 1 the [V(15)Sb(6)O(42)(H(2)O)](6-) cluster anion is bound to a [Co(N(3)C(5)H(15))(2)](2+) complex via a terminal oxygen atom. In the Co(2+)-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN(5)O octahedron. Similarly, in compound 2 an analogous NiN(5)O complex is joined to the [V(15)Sb(6)O(42)(H(2)O)](6-) anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in 1 and to Sb···N interactions in 2. In the solid-state lattices of 1 and 2, two additional [M(N(3)C(5)H(15))(2)](2+) complexes act as countercations and are located between the [{M(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)](4-) anions. Between the anions and cations strong N-H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the b axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni(2+) and Co(2+) cations do not

Excessive use of nitrogen in Chinese agriculture results in high N2O/(N2O+N2) product ratio of denitrification, primarily due to acidification of the soils

PubMed Central

Qu, Zhi; Wang, Jingguo; Almøy, Trygve; Bakken, Lars R

2014-01-01

China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long-term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 mM, we measured oxic respiration (R), potential denitrification (D), substrate-induced denitrification, and the denitrification product stoichiometry (NO, N2O, N2). Soils with a history of high fertilizer N levels had high N2O/(N2O+N2) ratios, but only in those field experiments where soil pH had been lowered by N fertilization. By comparing all soils, we found a strong negative correlation between pH and the N2O/(N2O+N2) product ratio (r2 = 0.759, P < 0.001). In contrast, the potential denitrification (D) was found to be a linear function of oxic respiration (R), and the ratio D/R was largely unaffected by soil pH. The immediate effect of liming acidified soils was lowered N2O/(N2O+N2) ratios. The results provide evidence that soil pH has a marginal direct effect on potential denitrification, but that it is the master variable controlling the percentage of denitrified N emitted as N2O. It has been known for long that low pH may result in high N2O/(N2O+N2) product ratios of denitrification, but our documentation of a pervasive pH-control of this ratio across soil types and management practices is new. The results are in good agreement with new understanding of how pH may interfere with the expression of N2O reductase. We argue that the management of soil pH should be high on the agenda for mitigating N2O emissions in the future, particularly for countries where ongoing intensification of plant production is likely to acidify the soils. PMID:24249526

Statistical modeling of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2.

PubMed

Ushakov, Vladimir G; Troe, Jürgen; Johnson, Ryan S; Guo, Hua; Ard, Shaun G; Melko, Joshua J; Shuman, Nicholas S; Viggiano, Albert A

2015-08-14

The rates of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2 are modeled by statistical rate theory accounting for energy- and angular momentum-specific rate constants for formation of the primary and secondary cationic adducts and their backward and forward reactions. The reactions are both suggested to proceed on sextet and quartet potential energy surfaces with efficient, but probably not complete, equilibration by spin-inversion of the populations of the sextet and quartet adducts. The influence of spin-inversion on the overall reaction rate is investigated. The differences of the two reaction rates mostly are due to different numbers of entrance states (atom + linear rotor or linear rotor + linear rotor, respectively). The reaction Fe(+) + N2O was studied either with (6)Fe(+) or with (4)Fe(+) reactants. Differences in the rate constants of (6)Fe(+) and (4)Fe(+) reacting with N2O are attributed to different contributions from electronically excited potential energy surfaces, such as they originate from the open-electronic shell reactants.

Theoretical characterization of stable eta1-N2O-, eta2-N2O-, eta1-N2-, and eta2-N2-bound species: intermediates in the addition reactions of nitrogen hydrides with the pentacyanonitrosylferrate(II) ion.

PubMed

Olabe, José A; Estiú, Guillermina L

2003-08-11

The addition of nitrogen hydrides (hydrazine, hydroxylamine, ammonia, azide) to the pentacyanonitrosylferrate(II) ion has been analyzed by means of density functional calculations, focusing on the identification of stable intermediates along the reaction paths. Initial reversible adduct formation and further decomposition lead to the eta(1)- and eta(2)-linkage isomers of N(2)O and N(2), depending on the nucleophile. The intermediates (adducts and gas-releasing precursors) have been characterized at the B3LYP/6-31G level of theory through the calculation of their structural and spectroscopic properties, modeling the solvent by means of a continuous approach. The eta(2)-N(2)O isomer is formed at an initial stage of adduct decompositions with the hydrazine and azide adducts. Further conversion to the eta(1)-N(2)O isomer is followed by Fe-N(2)O dissociation. Only the eta(1)-N(2)O isomer is predicted for the reaction with hydroxylamine, revealing a kinetically controlled N(2)O formation. eta(1)-N(2) and eta(2)-N(2) isomers are also predicted as stable species.

Spatial variability in groundwater N2 and N2O in the San Joaquin River

NASA Astrophysics Data System (ADS)

Hinshaw, S.; Dahlgren, R. A.

2010-12-01

The San Joaquin River is surrounded by nearly 2 million acres of irrigated agricultural land. Groundwater inputs from agricultural areas can have severe negative effects on water quality with high nitrate concentrations being a major concern. Riparian zones are important ecological habitats that mitigate nitrogen loading from groundwater discharging into rivers primarily by denitrification. Denitrification is a permanent removal of nitrate by anaerobic microbial communities via the reduction to NO, N2O and N2. However, previous studies have shown that these areas can be source of N2O emissions. Although removal of nitrate through denitrification is advantageous from a water quality perspective, N2O is a harmful greenhouse gas. This study aimed to investigate nitrogen dynamics and dissolved N gases in surface and groundwater of the riparian zones of the San Joaquin River. Excess N2 and N2O concentrations were measured in surface and groundwater at 4 locations along a 33 km reach of the river. Samples were collected within bank sediments and 5 transect points across the river at depth intervals between 2-3 cm and 150 cm. Dissolved N2 and Ar were measured by membrane inlet mass spectrometry and used to estimate excess dissolved N2 concentrations. Dissolved N2O concentrations were measured using the headspace equilibrium technique and analyzed with a gas chromatograph. Both N2 uptake and excess N2 were present, ranging from -3.40 to 8.65 N2 mg/L with a median concentration of 1.20 N2 mg/L. Significantly lower concentrations of N2O were present ranging from 0.0 to 0.12 N2O mg/L. Deeper groundwater sites had significantly higher N2 and N2O concentrations coinciding with decreased O2. The presence of excess N2 and low N2O concentrations documents the importance of denitrification in removing nitrate from groundwater. Further investigation will examine N2O emissions from riparian soils and benthic sediments using static chambers and focus on nitrogen pathways that

N2O and CO2 emissions following repeated application of organic and mineral N fertiliser from a vegetable crop rotation.

PubMed

De Rosa, Daniele; Rowlings, David W; Biala, Johannes; Scheer, Clemens; Basso, Bruno; Grace, Peter R

2018-05-11

Accounting for nitrogen (N) release from organic amendments (OA) can reduce the use of synthetic N-fertiliser, sustain crop production, and potentially reduce soil borne greenhouse gases (GHG) emissions. However, it is difficult to assess the GHG mitigation potential for OA as a substitute of N-fertiliser over the long term due to only part of the organic N added to soil is being released in the first year after application. High-resolution nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions monitored from a horticultural crop rotation over 2.5 years from conventional urea application rates were compared to treatments receiving an annual application of raw and composted chicken manure combined with conventional and reduced N-fertiliser rates. The repeated application of composted manure did not increase annual N 2 O emissions while the application of raw manure resulted in N 2 O emissions up to 35.2 times higher than the zero N fertiliser treatment and up to 4.7 times higher than conventional N-fertiliser rate due to an increase in C and N availability following the repeated application of raw OA. The main factor driving N 2 O emissions was the incorporation of organic material accompanied by high soil moisture while the application of synthetic N-fertiliser induced only short-term N 2 O emission pulse. The average annual N 2 O emission factor calculated accounting for the total N applied including OA was equal to 0.27 ± 0.17%, 3.7 times lower than the IPCC default value. Accounting for the estimated N release from OA only enabled a more realistic N 2 O emission factor to be defined for organically amended field that was equal to 0.48 ± 0.3%. This study demonstrated that accounting for the N released from repeated application of composted rather than raw manure can be a viable pathway to reduce N 2 O emissions and maintain soil fertility. Copyright © 2017. Published by Elsevier B.V.

Quantifying N2O emissions and production pathways from fresh waste during the initial stage of disposal to a landfill.

PubMed

Wang, Xiaojun; Jia, Mingsheng; Zhang, Han; Pan, Songqing; Kao, Chih Ming; Chen, Shaohua

2017-05-01

Intensive nitrous oxide (N 2 O) emissions usually occur at the working face of landfills. However, the specific amounts and contributions of the multiple pathways to N 2 O emissions are poorly understood. N 2 O emissions and the mutual conversions of N-species in both open and sealed simulated landfill reactors filled with fresh refuse were examined during a 100-h incubation period, and N 2 O sources were calculated using 15 N isotope labelling. N 2 O peak fluxes were above 70μgNkg -1 waste h -1 for both treatments. The sealed incubation reactors became a N 2 O sink when N 2 O in the ambient environment was sufficient. The total amount of N 2 O emissions under sealed conditions was 2.15±0.56mgNkg -1 waste, which was higher than that under open conditions (1.91±0.34mgNkg -1 waste). The NO 2 - peak appeared prior to the peak in N 2 O flux. The degree and duration of total nitrogen reduction in open incubations were larger and longer than those of sealed incubations and could possibly be due to oxygen supplementation. Denitrification (DF) was a major source of N 2 O generation during these incubations. The contribution of the DF pathway decreased from 89.2% to 61.3% during the open incubations. The effects of nitrification (NF) and nitrification-coupled denitrification (NCD) increased during the increasing phase and the decreasing phase of N 2 O flux, contributing 24.1-37.4% and 31.7-34.4% of total N 2 O emissions, respectively. In sealed treatments, the DF pathway accounted for more than 90% of the total N 2 O emission during the entire incubation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Theoretical study of the interaction of N/sub 2/ with water molecules. (H/sub 2/O)/sub n/:N/sub 2/, n = 1--8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtiss, L.A.; Eisgruber, C.L.

1984-03-01

Ab initio molecular orbital calculations including correlation energy have been carried out on the interaction of a single H/sub 2/O molecule with N/sub 2/. The potential energy surface for H/sub 2/O:N/sub 2/ is found to have a minimum corresponding to a HOH xxx N/sub 2/ structure with a weak (<2 kcal mol/sup -1/) hydrogen bond. A second, less stable, configuration corresponding to a H/sub 2/O xxx N/sub 2/ structure with N/sub 2/ bonded side on to the oxygen of H/sub 2/O was found to be either a minimum or a saddle point in the potential energy surface depending on themore » level of calculation. The minimal STO-3G basis set was used to investigate the interaction of up to eight H/sub 2/O molecules with N/sub 2/. Two types of clusters, one containing only HOH xxx N/sub 2/ interactions and the other containing both HOH xxxN/sub 2/ and H/sub 2/O xxx N/sub 2/ interactions, were investigated for (N/sub 2/:(H/sub 2/O)/sub n/, n = 2--8).« less

Comments on higher rank Wilson loops in N$$ \\mathcal{N} $$ = 2∗

DOE PAGES

Liu, James T.; Zayas, Leopoldo A. Pando; Zhou, Shan

2018-01-01

For N = 2∗ theory with U(N) gauge group we evaluate expectation values of Wilson loops in representations described by a rectangular Young tableau with n rows and k columns. The evaluation reduces to a two-matrix model and we explain, using a combination of numerical and analytical techniques, the general properties of the eigenvalue distributions in various regimes of parameters (N, λ, n, k) where λ is the ’t Hooft coupling. In the large N limit we present analytic results for the leading and sub-leading contributions. In the particular cases of only one row or one column we reproduce previouslymore » known results for the totally symmetry and totally antisymmetric representations. We also extensively discusss the N = 4 limit of the N = 2∗ theory. While establishing these connections we clarify aspects of various orders of limits and how to relax them; we also find it useful to explicitly address details of the genus expansion. As a result, for the totally symmetric Wilson loop we find new contributions that improve the comparison with the dual holographic computation at one loop order in the appropriate regime.« less

Anaerobic nitrification-denitrification mediated by Mn-oxides in meso-tidal sediments: Implications for N2 and N2O production

NASA Astrophysics Data System (ADS)

Fernandes, Sheryl Oliveira; Javanaud, Cedric; Aigle, Axel; Michotey, Valérie D.; Guasco, Sophie; Deborde, Jonathan; Deflandre, Bruno; Anschutz, Pierre; Bonin, Patricia C.

2015-04-01

Field measurements in the Arcachon Bay (southwest France) indicated anaerobic production of NOx via nitrification, which was coupled to the reduction of Mn-oxides. To prove the occurrence of this process, laboratory microcosm experiments were set up. A 15N tracer-based approach was used to track if NOx produced through Mn-oxide-mediated anaerobic nitrification would be reduced to N2 via denitrification or anammox. We also hypothesized the generation of the potent greenhouse gas nitrous oxide (N2O) during nitrification-denitrification in the presence of Mn-oxides. The microcosms were prepared using sediment sectioned at varying depths (0-2.5, 2.5-4.5, 4.5-8.5, 8.5-12 and 12-17 cm) during two sampling campaigns in October (fall) and January (winter). Labeling with 15NO3- revealed low N2 production originating from NO3- in the water column (Pw), which did not increase significantly on amendment with Mn-oxides during both sampling periods. However, for both seasons, a significant increase of N2 produced via nitrification (Pn) was observed upon addition of Mn-oxides reaching 76-fold enhancement at ≤ 2.5 cm. To support these results, sediment slurries of October were subjected to amendment of 15NH4+, 14NO3- with or without addition of Mn-oxides. A substantial production of P15 (N2 production from 15NH4+) within 0-17 cm provided further evidence on nitrification-denitrification mediated by Mn-oxides probably with minimal intervention of anammox. In organically rich sediments, anaerobic nitrification-denitrification mediated by Mn-oxides could play an important role in lowering re-mineralized NH4+ levels in the benthic system. As hypothesized, significant production of N2O through the pathway was observed revealing newer mechanisms leading to the generation of the radiative gas.

The non-modulated transfer of total effluent for serially coupled columns in gas chromatography.

PubMed

Krupcík, Ján; Mydlová-Memersheimerová, Janka; Májek, Pavel; Zapadlo, Michal; Sandra, Pat

2010-03-12

The non-modulated transfer (NMT) of the total effluent of the separation of polychlorinated biphenyls (PCBs) on two columns coupled in series has been studied. A non-polar poly(5%-phenyl-95%-methyl)siloxane column (40 m x 100 microm x 0.1 microm) and a polar 70%-cyanopropyl-polysilphenylene-siloxane column (4 m x 0.1 mm x 0.1 microm) were used as (1)D and (2)D columns, respectively. The effluents from both the (1)D column and the (1)D+(2)D column series were monitored independently by two FIDs. Data from the (1)D and (1)D+(2)D integration reports were used to evaluate the NMT experiment. (1)D retention times, t(R,i,D1), were directly accessible from (1)D integration report while (2)D retention times, t(R,i,B), were calculated for all corresponding peak pairs from (1)D and (1)D+(2)D integration reports as a difference t(R,i,D2)=t(R,i,D1+D2)-t(R,i,D1). Search for corresponding peaks of PCB congeners in the (1)D and (1)D+(2)D chromatograms is elucidated in detail on standard PCB samples and on PCB congeners present in the technical formulation Arochlor 1242. Both retention times (t(R,i,D1) and t(R,i,D2)) as well as peak widths at half height (w(h,i)) and peak heights (h(i)) obtained from integration reports were used to construct 2D and 3D images for PCB NMT separations on serially coupled columns. The performance of the NMT procedure is illustrated by the separation of (i) standard PCB solutions, (ii) a mixture of the 209 PCBs, and (iii) a mixture of Arochlor 1242 and hydrocarbons on the DB-5+BPX-70 column series. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Effects of soil moisture and temperature on NO, NO2, and N2O emissions from European forest soils

NASA Astrophysics Data System (ADS)

Schindlbacher, Andreas; Zechmeister-Boltenstern, Sophie; Butterbach-Bahl, Klaus

2004-09-01

Emissions of NO, NO2, and N2O to the atmosphere were measured with a fully automated laboratory system from undisturbed soil columns obtained from five different temperate and one boreal forest sites. The soils were chosen to cover a transect through Europe, sandy and loamy textures, and different atmospheric nitrogen deposition rates. In a two-factorial experimental design, soil cores were kept under varying conditions with respect to temperature (range 5-20°C) and soil moisture (range 0-300 kPa). The combination of soil temperature and soil moisture could explain a better part of variations in NO (up to 74%) and N2O (up to 86%) emissions for individual soils, but average emissions differed significantly between various forest soils. Generally, NO and N2O were emitted from all soils except from the boreal pine forest soil, where NO was consumed. NO emissions from the German spruce forest receiving highest yearly nitrogen inputs of >35 kg ha-1 yr-1 ranged from 1.3 to 608.9 μg NO-N m-2 h-1 and largely exceeded emissions from other soils. Average N2O emissions from this soil tended also to be highest (171.7 ± 42.2 μg N2O-N m-2 h-1), but did not differ significantly from other soils. NO2 deposition occurred in all soils and strongly correlated to NO emissions. NO and N2O emissions showed a positive exponential relationship to soil temperature. With activation energies between 57 and 133 kJ mol-1, N2O emissions from the various soils responded more uniformely to temperature than NO emissions with 41 and 199 kJ mol-1. The two Austrian beech forest soils showed exceptionally high activation energies for NO emissions, which might be attributed to chemodenitrification. N2O emissions increased with increasing water filled pore space (WFPS) or decreasing water tension, respectively. Maximal N2O emissions were measured between 80 and 95% WFPS or 0 kPa water tension. Optimal moisture for NO emission differed significantly between the soils, and ranged between 15% WFPS in

Isotopomeric characterization of N2O produced, consumed, and emitted by automobiles.

PubMed

Toyoda, Sakae; Yamamoto, Sei-ichiro; Arai, Shinji; Nara, Hideki; Yoshida, Naohiro; Kashiwakura, Kiriko; Akiyama, Ken-ichi

2008-01-01

Fossil fuel combustion is the second largest anthropogenic source of nitrous oxide (N2O) after agriculture. The estimated global N2O flux from combustion sources, as well as from other sources, still has a large uncertainty. Herein, we characterize automobile sources using N2O isotopomer ratios (nitrogen and oxygen isotope ratios and intramolecular site preference of 15N, SP) to assess their contributions to total global sources and to deconvolute complex production/consumption processes during combustion and subsequent catalytic treatments of exhaust. Car exhaust gases were sampled under running and idling state, and N2O isotopomer ratios were measured by mass spectrometry. The N2O directly emitted from an engine of a vehicle running at constant velocity had almost constant isotopomer ratios (delta15Nbulk = -28.7 +/- 1.2 per thousand, delta18O = 28.6 +/- 3.3 per thousand, and SP = 4.2 +/- 0.8 per thousand) irrespective of the velocity. After passing through catalytic converters, the isotopomer ratios showed an increase which varied with the temperature and the aging of the catalysts. The increase suggests that both production and consumption of N2O occur on the catalyst and that their rates can be comparable. It was noticed that in the idling state, the N2O emitted from a brand new car has higher isotopomer ratios than that from used cars, which indicate that technical improvements in catalytic converters can reduce the N2O from mobile combustion sources. On average, the isotopomeric signatures of N2O finally emitted from automobiles are not sensitive to running/idling states or to aging of the catalysts. Characteristic average isotopomer ratios of N2O from automobile sources are estimated at -4.9 +/- 8.2 per thousand, 43.5 +/- 13.9 per thousand, and 12.2 +/- 9.1 per thousand for delta15Nbulk, delta18O, and SP, respectively.

Seasonal cycle and secular trend of the total and tropospheric column abundance of ethane above the Jungfraujoch

NASA Technical Reports Server (NTRS)

Ehhalt, D. H.; Schmidt, U.; Zander, R.; Demoulin, P.; Rinsland, C. P.

1991-01-01

The secular trend and the seasonal cycle of the total and the tropospheric column abundances of C2H6 over the Jungfraujoch Station (Switzerland) were deduced from infrared solar spectra recorded in 1951 and from 1984 to 1988. Results show a definite seasonal variation in the total vertical column abundance of C2H6, with a maximum of (1.43 + or - 0.03) x 10 to the 16th molecules/sq cm during March and April and a minimum in the fall; the ratio between the maximum and the minimum column abundances was found to be 1.62 + or - 0.11. The secular trend in the tropospheric burden above the Jungfraujoch was found to be (0.85 + or - 0.3) percent/yr.

Uptake properties of Ni2+ by nCaO.Al2O3.2SiO2 (n=1-4) prepared from solid-state reaction of kaolinite and calcite.

PubMed

Jha, Vinay Kumar; Kameshima, Yoshikazu; Nakajima, Akira; Okada, Kiyoshi; MacKenzie, Kenneth J D

2005-08-31

A series of nCaO.Al2O3.2SiO2 samples (n=1-4) were prepared by solid-state reaction of mechanochemically treated mixtures of kaolinite and calcite fired at 600-1000 degrees C for 24 h. All the samples were X-ray amorphous after firing at 600-800 degrees C but had crystallized by 900 degrees C. The main crystalline phases were anorthite (n=1), gehlenite (n=2 and 3) and larnite (n=4). The uptake of Ni2+ by nCaO.Al2O3.2SiO2 samples fired at 800 and 900 degrees C was investigated at room temperature using solutions with initial Ni2+ concentrations of 0.1-50 mmol/l. Amorphous samples (fired at 800 degrees C) showed a higher Ni2+ uptake capacity than crystalline samples (fired at 900 degrees C). Ni2+ uptake was found to increase with increasing of CaO content. Amorphous 4CaO.Al2O3.2SiO2 showed the highest Ni2+ uptake capacity (about 9 mmol/g). The Ni2+ uptake abilities of the present samples are higher than those of other materials reported in the literature. Since the sorbed Ni2+/released Ca2+ ratios of these samples are close to unity, ion replacement of Ni2+ for Ca2+ is thought to be the principal mechanism of Ni2+ uptake by the present samples.

Brewer spectrometer total ozone column measurements in Sodankylä

NASA Astrophysics Data System (ADS)

Karppinen, Tomi; Lakkala, Kaisa; Karhu, Juha M.; Heikkinen, Pauli; Kivi, Rigel; Kyrö, Esko

2016-06-01

Brewer total ozone column measurements started in Sodankylä in May 1988, 9 months after the signing of The Montreal Protocol. The Brewer instrument has been well maintained and frequently calibrated since then to produce a high-quality ozone time series now spanning more than 25 years. The data have now been uniformly reprocessed between 1988 and 2014. The quality of the data has been assured by automatic data rejection rules as well as by manual checking. Daily mean values calculated from the highest-quality direct sun measurements are available 77 % of time with up to 75 measurements per day on clear days. Zenith sky measurements fill another 14 % of the time series and winter months are sparsely covered by moon measurements. The time series provides information to survey the evolution of Arctic ozone layer and can be used as a reference point for assessing other total ozone column measurement practices.

Analysis of Ti and TiO2 nanolayers by total reflection X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Kubala-Kukuś, A.; Banaś, D.; Stabrawa, I.; Szary, K.; Sobota, D.; Majewska, U.; Wudarczyk-Moćko, J.; Braziewicz, J.; Pajek, M.

2018-07-01

Total reflection X-ray photoelectron spectroscopy (TRXPS) is applied in the analysis of Ti and TiO2 nanolayers deposited on silicon and silicon dioxide substrates. The idea of application of total-reflection phenomenon for exciting X-ray used in the XPS technique is briefly discussed. The experimental setup and measurement conditions for the studied Ti and TiO2 layers are presented. The XPS spectra were registered both for the non-total and total reflection regimes. The survey spectra and C1s, N1s, Ti2p and O1s photoelectron peaks are shown. For energy calibration, the position of C1s photoelectron peak was applied (C-C component, binding energy 284.8 eV). The peak to background ratios are discussed as regards the dependence of the excitation angle. An increase of this ratio for the glancing angle 1°, being below critical angle of the X-ray beam and sample material, results in an improvement of XPS detection limit by factor up to 2. In the case of the Ti nanolayer, additionally, the thickness of the overlayer TiO2 is determined. As an example of applying the TRXPS technique, the analysis of Ti nanolayers implanted by highly charged Xe35+ ions of 280 keV energy is discussed. The Xe3d and O1s photoelectron peaks are presented and discussed.

Spatial Variations in N2O Concentration and Isotopomer Composition off the Peru Coast

NASA Astrophysics Data System (ADS)

Bourbonnais, A.; Letscher, R. T.; Kock, A.; Bange, H. W.; Altabet, M. A.

2016-02-01

Nitrous oxide (N2O) is a potent greenhouse gas and stratospheric ozone depleting substance. The ocean is an important source of N2O to the atmosphere, accounting for up to about 30% of total emissions. However, the factors controlling N2O production and consumption in oceanic environments are still not understood nor constrained. N2O is a by-product of aerobic nitrification, and is formed by two different pathways: 1) the decomposition of hydroxylamine, an intermediate during ammonium oxidation to nitrite, or 2) the reduction of nitrite to N2O (nitrifier-denitrification). N2O is also an intermediate during denitrification under anoxic conditions. In this study, we measured N2O concentrations and isotopomer ratios, as well as O2, nutrient and biogenic N2 concentrations and the isotopic compositions of nitrate, nitrite and biogenic N2 at several coastal stations during two cruises off the Peru coast (6-14°S, 75-81°W) in December 2012 and January 2013. [N2O] varied from below equilibrium values in the OMZ to up to 238 nmol L-1 at 11 m depth at one of the shallowest stations. The isotopic composition of N2O (bulk δ15N: -5 to 30‰, δ18O: 41 to 95‰, and Site Preference: -3 to 65‰) also varied widely, with important differences between stations. Our results show a strong spatial heterogeneity in the mechanisms controlling N2O production and consumption in coastal upwelling regions, which should be taken into account in oceanic N2O models. We will discuss the contributions from different N2O production processes responsible for the observed extreme N2O accumulations.

The diversity of the N2O reducers matters for the N2O:N2 denitrification end-product ratio across an annual and a perennial cropping system.

PubMed

Domeignoz-Horta, Luiz A; Spor, Aymé; Bru, David; Breuil, Marie-Christine; Bizouard, Florian; Léonard, Joël; Philippot, Laurent

2015-01-01

Agriculture is the main source of terrestrial emissions of N2O, a potent greenhouse gas and the main cause of ozone layer depletion. The reduction of N2O into N2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only biological process known to eliminate this greenhouse gas. Recent studies showed that a previously unknown clade of N2O-reducers was related to the capacity of the soil to act as an N2O sink, opening the way for new strategies to mitigate emissions. Here, we investigated whether the agricultural practices could differently influence the two N2O reducer clades with consequences for denitrification end-products. The abundance of N2O-reducers and producers was quantified by real-time PCR, and the diversity of both nosZ clades was determined by 454 pyrosequencing. Potential N2O production and potential denitrification activity were used to calculate the denitrification gaseous end-product ratio. Overall, the results showed limited differences between management practices but there were significant differences between cropping systems in both the abundance and structure of the nosZII community, as well as in the [rN2O/r(N2O+N2)] ratio. More limited differences were observed in the nosZI community, suggesting that the newly identified nosZII clade is more sensitive than nosZI to environmental changes. Potential denitrification activity and potential N2O production were explained mainly by the soil properties while the diversity of the nosZII clade on its own explained 26% of the denitrification end-product ratio, which highlights the importance of understanding the ecology of this newly identified clade of N2O reducers for mitigation strategies.

Relationship between synoptic scale weather systems and column averaged atmospheric CO2

NASA Astrophysics Data System (ADS)

Naja, M.; Yaremchuk, A.; Onishi, R.; Maksyutov, S.; Inoue, G.

2005-12-01

Analysis of the atmospheric CO2 observations with transport models contributes to the understanding of the geographical distributions of CO2 sources and sinks. Space-borne sensors could be advantageous for CO2 measurements as they can provide wider spatial and temporal coverage. Inversion studies have suggested requirement of better than 1% precision for the space-borne observations. Since sources and sinks are inferred from spatial and temporal gradients in CO2, the space-borne observations must have no significant geographically varying biases. To study the dynamical biases in column CO2 due to possible correlation between clouds and atmospheric CO2 at synoptic scale, we have made simulations of CO2 (1988-2003) using NIES tracer transport model. Model resolution is 2.5o x 2.5o in horizontal and it has 15 vertical sigma-layers. Fluxes for (1) fossil fuels, (2) terrestrial biosphere (CASA NEP), (3) the oceans, and (4) inverse model derived monthly regional fluxes from 11 land and 11 ocean regions are used. SVD truncation is used to filter out noise in the inverse model flux time series. Model reproduces fairly well CO2 global trend and observed time series at monitoring sites around the globe. Lower column CO2 concentration is simulated inside cyclonic systems in summer over North hemispheric continental areas. Surface pressure is used as a proxy for dynamics and it is demonstrated that anomalies in column averaged CO2 has fairly good correlation with the anomalies in surface pressure. Positive correlation, as high as 0.7, has been estimated over parts of Siberia and N. America in summer time. Our explanation is based on that the low-pressure system is associated the upward motion, which leads to lower column CO2 values over these regions due to lifting of CO2-depleted summertime PBL air, and higher column CO2 over source areas. A sensitivity study without inverse model fluxes shows same correlation. The low-pressure systems' induced negative biases are 0

(Carbonato-κ(2)O,O')bis-(5,5'-dimethyl-2,2'-bipyridyl-κ(2)N,N')cobalt(III) bromide trihydrate.

PubMed

Arun Kumar, Kannan; Meera, Parthsarathi; Amutha Selvi, Madhavan; Dayalan, Arunachalam

2012-04-01

In the title complex, [Co(CO(3))(C(12)H(12)N(2))(2)]Br·3H(2)O, the Co(III) cation has a distorted octa-hedral coordination environment. It is chelated by four N atoms of two different 5,5'-dimethyl-2,2'-bipyridyl (dmbpy) ligands in axial and equatorial positions, and by two O atoms of a carbonate anion completing the equatorial positions. Although the water mol-ecules are disordered and their H atoms were not located, there are typical O⋯O distances between 2.8 and 3.0 Å, indicating O-H⋯O hydrogen bonding. The crystal packing is consolidated by C-H⋯O and C-H⋯Br hydrogen bonds, as well as π-π stacking inter-actions between adjacent pyridine rings of the dmbpy ligands, with centroid-centroid distances of 3.694 (3) and 3.7053 (3) Å.

Nano-sized TiO2 (nTiO2) induces metabolic perturbations in Physarum polycephalum macroplasmodium to counter oxidative stress under dark conditions.

PubMed

Zhang, Zhi; Liang, Zhi Cheng; Zhang, Jian Hua; Tian, Sheng Li; Le Qu, Jun; Tang, Jiao Ning; De Liu, Shi

2018-06-15

Nano-sized TiO 2 (nTiO 2 ) exerts an oxidative effect on cells upon exposure to solar or UV irradiation and ecotoxicity of the nTiO 2 is an urgent concern. Little information is available regarding the effect of TiO 2 on cells under dark conditions. Metabolomics is a unique approach to the discovery of biomarkers of nTiO 2 cytotoxicity, and leads to the identification of perturbed metabolic pathways and the mechanism underlying nTiO 2 toxicity. In the present study, gas chromatography mass spectrometry (GC/MS)-based metabolomics was performed to investigate the effect of nTiO 2 on sensitive cells (P. polycephalum macroplasmodium) under dark conditions. According to the multivariate pattern recognition analysis, at least 60 potential metabolic biomarkers related to sugar metabolism, amino acid metabolism, nucleotide metabolism, polyamine biosynthesis, and secondary metabolites pathways were significantly perturbed by nTiO 2 . Notably, many metabolic biomarkers and pathways were related to anti-oxidant mechanisms in the living organism, suggesting that nTiO 2 may induce oxidative stress, even under dark conditions. This speculation was further validated by the biochemical levels of reactive oxygen species (ROS), 8-hydroxy-2-deoxyguanosine (8-OHdG), and total soluble phenols (TSP). We inferred that the oxidative stress might be related to nTiO 2 -induced imbalance of cellular ROS. To the best of our knowledge, the present study is the first to investigate the nTiO 2 -induced metabolic perturbations in slime mold, provide a new perspective of the mechanism underlying nTiO 2 toxicity under dark conditions, and show that metabolomics can be employed as a rapid, reliable and powerful tool to investigate the interaction among organisms, the environment, and nanomaterials. Copyright © 2018 Elsevier Inc. All rights reserved.

Uncertainties in United States agricultural N2O emissions: comparing forward model simulations to atmospheric N2O data.

NASA Astrophysics Data System (ADS)

Nevison, C. D.; Saikawa, E.; Dlugokencky, E. J.; Andrews, A. E.; Sweeney, C.

2014-12-01

Atmospheric N2O concentrations have increased from 275 ppb in the preindustrial to about 325 ppb in recent years, a ~20% increase with important implications for both anthropogenic greenhouse forcing and stratospheric ozone recovery. This increase has been driven largely by synthetic fertilizer production and other perturbations to the global nitrogen cycle associated with human agriculture. Several recent regional atmospheric inversion studies have quantified North American agricultural N2O emissions using top-down constraints based on atmospheric N2O data from the National Oceanic and Atmospheric Administration (NOAA) Global Greenhouse Gas Reference Network, including surface, aircraft and tall tower platforms. These studies have concluded that global N2O inventories such as EDGAR may be underestimating the true U.S. anthropogenic N2O source by a factor of 3 or more. However, simple back-of-the-envelope calculations show that emissions of this magnitude are difficult to reconcile with the basic constraints of the global N2O budget. Here, we explore some possible reasons why regional atmospheric inversions might overestimate the U.S. agricultural N2O source. First, the seasonality of N2O agricultural sources is not well known, but can have an important influence on inversion results, particularly when the inversions are based on data that are concentrated in the spring/summer growing season. Second, boundary conditions can strongly influence regional inversions but the boundary conditions used may not adequately account for remote influences on surface data such as the seasonal stratospheric influx of N2O-depleted air. We will present a set of forward model simulations, using the Community Land Model (CLM) and two atmospheric chemistry tracer transport models, MOZART and the Whole Atmosphere Community Climate Model (WACCM), that examine the influence of terrestrial emissions and atmospheric chemistry and dynamics on atmospheric variability in N2O at U.S. and

The structure of galactic HI in directions of low total column density

NASA Technical Reports Server (NTRS)

Lockman, F. J.; Jahoda, K.; Mccammon, D.

1985-01-01

A detailed 21 cm study of areas of that have the smallest known amount of HI in the northern sky was performed. These observations were corrected for stray radiation. The region of main interest, around alpha = 10(h)45(m), delta = 57 deg 20', has a minimium N(HI) of 4.5 x 10 to the 19th power/sq cm. Spectra taken at 21' resolution over a field 4 x 3 deg in this direction show up to four HI line components. Two, near 0 and -50 km/s, are ubiquitous. There is also a narrow component at -10 km/s attributable to a diffuse cloud covering half of the field, and scattered patches of HI at v -100 km/s. the low and intermediate velocity components have a broad line width and are so smoothly distributed across the region that it is unlikely that they contain significant unresolved angular structure. Eight other low column density directions were also observed. Their spectra typically have several components, but the total column density is always 7 x 10 to the 19th power/sq cm and changes smoothly along a 2 deg strip. Half of the directions show narrow lines arising from weak diffuse HI clouds that contain 0.5 to 3.0 x 10 to the 19th power/sq cm.

CO Column Density and Extinction in the Chamaeleon II--III Dark-Cloud Complex

NASA Astrophysics Data System (ADS)

Hayakawa, Takahiro; Cambrésy, Laurent; Onishi, Toshikazu; Mizuno, Akira; Fukui, Yasuo

2001-12-01

We carried out 13CO (J = 1 -- 0) and C18O (J = 1 -- 0) observations of the Chamaeleon II--III dark-cloud complex with the NANTEN radio telescope. The column densities of both molecular isotopes were derived assuming LTE. The AV values were obtained by scaling the AV values that were derived using an adaptive-grid star-count method applied to the DENIS J-band data. We established the AV--CO isotope column-density relations in Cha II and III, and compared them with those in Cha I. The slopes of the AV--13CO relations for Cha II and III are steeper than that for Cha I. Those of the AV -- C18O relations are similar among the three clouds. The total column density ratio, N(13O) / N(C18O, in Cha I tends to be small compared with those in Cha II or Cha III; the ratios range from ~ 5 to ~ 25 at low extinction in Cha II and III, but at most ~ 10 in Cha I. We suggest that the increase of N(13CO) due to the 13CO formation process causes cloud-to-cloud variations in the AV -- N(13CO) correlation.

Effect of fertilizer application on NO and N2O fluxes from agricultural fields

NASA Astrophysics Data System (ADS)

Harrison, Roy M.; Yamulki, Sirwan; Goulding, K. W. T.; Webster, C. P.

1995-12-01

Losses of fertilizer as NO and N2O were studied at Broadbalk field, Rothamsted Experimental Station in England, on which subplots have been subject to differing constant levels of fertilizer application for many years. Fluxes of NO and N2O were measured using open- and closed-chamber techniques, respectively. Fluxes from unfertilized soil ranged from 0.3 to 4.8 ng N m-2 s-1 for NO and 0.23 to 3.0 ng N m-2 s-1 for N2O. The corresponding fluxes from the plot with the highest fertilizer application (92 kg N ha-1 yr-1 as NH4NO3) ranged from 0.5 to 64 ng N m-2 s-1 for NO and 0.4 to 240 ng N m-2 s-1 for N2O. Application of increasing amounts of fertilizer substantially enhanced emission rates of both NO and N2O. However, the amount of increase was controlled by competition between the crop and the microorganisms for the available soil nutrients, and loss of N2O to the atmosphere increased sharply at superoptimal levels of fertilizer application. The fertilizer-derived NO and N2O emissions represented approximately 90% of the total emission of these gases during the 25-day sampling period after fertilizer application. The results suggest that while increasing the amount of fertilizer increases both NO and N2O fluxes simultaneously, the NO/N2O emission ratio decreases. Results from laboratory experiments showed that the magnitude of the fertilizer loss as N2O was strongly affected by the form of the applied fertilizer.

Reaction of N2O5 with H2O on carbonaceous surfaces

NASA Technical Reports Server (NTRS)

Brouwer, L.; Rossi, M. J.; Golden, D. M.

1986-01-01

The heterogeneous reaction of N2O5 with commercially available ground charcoal in the absence of H2O revealed a physisorption process (gamma = 0.003), together with a redox reaction generating mostly NO. Slow HNO3 formation was the result of the interaction of N2O5 with H2O that was still adsorbed after prolonged pumping at 0.0001 torr. In the presence of H2O, the same processes with gamma = 0.005 are observed. The redox reaction dominates in the early stages of the reaction, whereas the hydrolysis gains importance later at the expense of the redox reaction. The rate law for HNO3 generation was found to be d(HNO3)/dt = k(bi)(H2O)(N2O5) with k(bi), the effective bimolecular rate constants, for 10 mg of carbon being (1.6 + or - 0.3) x 10 to the -13th cu cm/s.

Frozen Cropland Soil in Northeast China as Source of N2O and CO2 Emissions

PubMed Central

Qiao, Yunfa; Han, Xiaozeng; Brancher Franco, Roberta

2014-01-01

Agricultural soils are important sources of atmospheric N2O and CO2. However, in boreal agro-ecosystems the contribution of the winter season to annual emissions of these gases has rarely been determined. In this study, soil N2O and CO2 fluxes were measured for 6 years in a corn-soybean-wheat rotation in northeast China to quantify the contribution of wintertime N2O and CO2 fluxes to annual emissions. The treatments were chemical fertilizer (NPK), chemical fertilizer plus composted pig manure (NPKOM), and control (Cont.). Mean soil N2O fluxes among all three treatments in the winter (November–March), when soil temperatures are below −7°C for extended periods, were 0.89–3.01 µg N m−2 h−1, and in between the growing season and winter (October and April), when freeze-thaw events occur, 1.73–5.48 µg N m−2 h−1. The cumulative N2O emissions were on average 0.27–1.39, 0.03–0.08 and 0.03–0.11 kg N2O–N ha−1 during the growing season, October and April, and winter, respectively. The average contributions of winter N2O efflux to annual emissions were 6.3–12.1%. In all three seasons, the highest N2O emissions occurred in NPKOM, while NPK and Cont. emissions were similar. Cumulative CO2 emissions were 2.73–4.94, 0.13–0.20 and 0.07–0.11 Mg CO2-C ha−1 during growing season, October and April, and winter, respectively. The contribution of winter CO2 to total annual emissions was 2.0–2.4%. Our results indicate that in boreal agricultural systems in northeast China, CO2 and N2O emissions continue throughout the winter. PMID:25536036

Analysis of SAW properties in ZnO/AlxGa1-xN/c-Al2O3 structures.

PubMed

Chen, Ying; Emanetoglu, Nuri William; Saraf, Gaurav; Wu, Pan; Lu, Yicheng; Parekh, Aniruddh; Merai, Vinod; Udovich, Eric; Lu, Dong; Lee, Dong S; Armour, Eric A; Pophristic, Milan

2005-07-01

Piezoelectric thin films on high acoustic velocity nonpiezoelectric substrates, such as ZnO, AlN, or GaN deposited on diamond or sapphire substrates, are attractive for high frequency and low-loss surface acoustic wave devices. In this work, ZnO films are deposited on AlxGa1-xN/c-Al2O3 (0 < or = chi < or = 1) substrates using the radio frequency (RF) sputtering technique. In comparison with a single AlxGa1-xN layer deposited on c-Al2O3 with the same total film thickness, a ZnO/AlxGa1-xN/c-Al2O3 multilayer structure provides several advantages, including higher order wave modes with higher velocity and larger electromechanical coupling coefficient (K2). The surface acoustic wave (SAW) velocities and coupling coefficients of the ZnO/AlxGa1-xN/c-Al2O3 structure are tailored as a function of the Al mole percentage in AlxGa1-xN films, and as a function of the ZnO (h1) to AlxGa1-xN (h2) thickness ratio. It is found that a wide thickness-frequency product (hf) region in which coupling is close to its maximum value, K(2)max, can be obtained. The K(2)max of the second order wave mode (h1 = h2) is estimated to be 4.3% for ZnO/GaN/c-Al2O3, and 3.8% for ZnO/AlN/c-Al2O3. The bandwidth of second and third order wave modes, in which the coupling coefficient is within +/- 0.3% of K(2)max, is calculated to be 820 hf for ZnO/GaN/c-Al2O3, and 3620 hf for ZnO/AlN/c-Al2O3. Thus, the hf region in which the coupling coefficient is close to the maximum value broadens with increasing Al content, while K(2)max decreases slightly. When the thickness ratio of AlN to ZnO increases, the K(2)max and hf bandwidth of the second and third higher wave modes increases. The SAW test devices are fabricated and tested. The theoretical and experimental results of velocity dispersion in the ZnO/AlxGa1-xN/c-Al2O3 structures are found to be well matched.

In situ Dynamics of O2, pH, Light, and Photosynthesis in Ikaite Tufa Columns (Ikka Fjord, Greenland)-A Unique Microbial Habitat.

PubMed

Trampe, Erik C L; Larsen, Jens E N; Glaring, Mikkel A; Stougaard, Peter; Kühl, Michael

2016-01-01

The Ikka Fjord (SW Greenland) harbors a unique microbial habitat in the form of several hundred submarine tufa columns composed of ikaite, a special hexahydrate form of calcium carbonate that precipitates when alkaline phosphate- and carbonate-enriched spring water seeping out of the sea floor meets cold seawater. While several unique heterotrophic microbes have been isolated from the tufa columns, the microbial activity, and the boundary conditions for microbial growth in ikaite have remained unexplored. We present the first detailed in situ characterization of the physico-chemical microenvironment and activity of oxygenic phototrophs thriving within the ikaite columns. In situ underwater microsensor measurements of pH, temperature, and irradiance in the porous ikaite crystal matrix, revealed an extreme microenvironment characterized by low temperatures, strong light attenuation, and gradients of pH changing from pH 9 at the outer column surface to above pH 10 over the first 1-2 cm of the ikaite. This outer layer of the freshly deposited ikaite matrix contained densely pigmented yellow and green zones harboring a diverse phototrophic community dominated by diatoms and cyanobacteria, respectively, as shown by amplicon sequencing. In situ O2 measurements, as well as underwater variable chlorophyll fluorescence measurements of photosynthetic activity, demonstrated high levels of oxygenic photosynthesis in this extreme gradient environment with strong irradiance-driven O2 dynamics ranging from anoxia to hyperoxic conditions in the ikaite matrix, albeit the local formation of gas bubbles buffered the day-night dynamics of O2 in the tufa columns. The microbial phototrophs in the ikaite matrix are embedded in exopolymers forming endolithic biofilms that may interact with mineral formation and cementing of ikaite crystals.

N2O fluxes at the soil-atmosphere interface in various ecosystems and the global N2O budget

NASA Technical Reports Server (NTRS)

Banin, Amos

1987-01-01

The overall purpose of this research task is to study the effects of soil properties and ecosystem variables on N2O exchanges at the soil-atmosphere interface, and to assess their effects on the globle N2O budget. Experimental procedures are implemented in various sites to measure the source/sink relations of N2O at the soil-atmosphere interface over prolonged periods of time as part of the research of biogeochemical cycling in terrestrial ecosystems. A data-base for establishing quantitative correlations between N2O fluxes and soil and environmental parameters that are of potential use for remote sensing, is being developed.

[County-scale N2O emission inventory of China's manure management system].

PubMed

Wang, Chuan; Gao, Wei; Zhou, Feng; Chen, Qing; Ying, Na; Xu, Peng; Hou, Xi-Kang

2013-10-01

Manure is one of the two largest contributors to China's N2O emission. By using the county-scale activity data and the regional emission factors and related parameters with spatial differentiation in China in 2008, this paper assessed the N2O emission loading, sources profile, spatial pattern, and uncertainty, aimed to establish a high-resolution N2O emission inventory of China's manure management system in 2008. As compared with the research results based on the IPCC, EDGAR, and other works, the proposed emission inventory was more reliable and comprehensive. The total China' s N2O emission from manure in 2008 was estimated as 572 Gg, among which, the emission from the manure except pasture/range/paddock was 322 Gg (56.3%), from the manure in pasture/range/paddock was 180 Gg (31.5%), and the indirect emission from atmospheric volatilized N deposition and leaching/runoff was 45.8 Gg (8.0%) and 1.23 Gg (0.2%), respectively. The spatial pattern of China's N2O emission from manure was more centralized, and mainly concentrated in Jilin, Shandong, Sichuan, Hunan, Henan, Heilongjiang, and Liaoning provinces, contributing 52.4% of the total emission, and more than 25% being from 84 counties (only < 3% of the whole counties). The proposed emission inventory had a higher spatial resolution and accuracy. Different with this inventory, the IPCC underestimated the direct emission while overestimated the indirect emission, with the regions of higher emission rate being underestimated by -1.5%-6.0% and those of lower emission rate being overestimated by 1.6%-13%. As for the EDGAR, the regions of higher emission rate were underestimated by -18. 8--50.0%, and those of lower emission rate were mostly overestimated by 25%-54.1%.

Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

PubMed

Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

2016-02-01

This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

Optimizing rice plant photosynthate allocation reduces N2O emissions from paddy fields

NASA Astrophysics Data System (ADS)

Jiang, Yu; Huang, Xiaomin; Zhang, Xin; Zhang, Xingyue; Zhang, Yi; Zheng, Chengyan; Deng, Aixing; Zhang, Jun; Wu, Lianhai; Hu, Shuijin; Zhang, Weijian

2016-07-01

Rice paddies are a major source of anthropogenic nitrous oxide (N2O) emissions, especially under alternate wetting-drying irrigation and high N input. Increasing photosynthate allocation to the grain in rice (Oryza sativa L.) has been identified as an effective strategy of genetic and agronomic innovation for yield enhancement; however, its impacts on N2O emissions are still unknown. We conducted three independent but complementary experiments (variety, mutant study, and spikelet clipping) to examine the impacts of rice plant photosynthate allocation on paddy N2O emissions. The three experiments showed that N2O fluxes were significantly and negatively correlated with the ratio of grain yield to total aboveground biomass, known as the harvest index (HI) in agronomy (P < 0.01). Biomass accumulation and N uptake after anthesis were significantly and positively correlated with HI (P < 0.05). Reducing photosynthate allocation to the grain by spikelet clipping significantly increased white root biomass and soil dissolved organic C and reduced plant N uptake, resulting in high soil denitrification potential (P < 0.05). Our findings demonstrate that optimizing photosynthate allocation to the grain can reduce paddy N2O emissions through decreasing belowground C input and increasing plant N uptake, suggesting the potential for genetic and agronomic efforts to produce more rice with less N2O emissions.

Interfacial RhO{sub x}/CeO{sub 2} sites as locations for low temperature N{sub 2}O dissociation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cunningham, J.; Hickey, J.N.; Soria, J.

Temperatures required for extensive N{sub 2}O dissociation to N{sub 2}, or to N{sub 2} plus O{sub 2}, over 0.5% RhO{sub x}/CeO{sub 2} materials, and over polycrystalline Rh{sub 2}O{sub 3} or CeO{sub 2}, are compared for preoxidised and for prereduced samples on the basis of conversions achieved in pulsed-reactant, continuous-flow and recirculatory microcatalytic reactors. Influences of sample prereduction or preoxidation upon those measurements and upon results from parallel ESR and FTIR studies of N{sub 2}O interactions with such materials are presented and compared. Over partially reduced 0.5% RhO{sub x}/CeO{sub 2} materials complete dissociation of N{sub 2}O pulses to N{sub 2} plusmore » O{sub 2} is obtained at temperatures 50-100{degrees} lower than those required for extensive dissociation over prereduced Rh{sub 2}O{sub 3}. Furthermore, N{sub 2} was the sole product from the latter. Higher ongoing N{sub 2}O conversions to N{sub 2} plus O{sub 2} at 623 K over 0.5% Rh/CeO{sub 2} in pulsed-reactant than in continuous-flow mode point to regeneration of active sites under helium flushing between pulses. The TPD profile for dioxygen release from Rhodia containing samples at temperatures 350-550 K is presented. ESR measurements reveal complementary effects of outgassings at temperatures, T{sub v}, {ge} 573 K upon the availability at RhO{sub x}/CeO{sub 2} surfaces of electron-excess sites reactive towards N{sub 2}O. Differences from observations over Rh{sub 2}O{sub 3} and CeO{sub 2} can be understood by attributing the low-temperature activity of RhO{sub x}/CeO{sub 2} to electron excess sites at microinterfaces between the dispersed Rhodia component and the Ceria support.« less

Fast gradient screening of pharmaceuticals with 5 cm long, narrow bore reversed-phase columns packed with sub-3 μm core-shell and sub-2 μm totally porous particles.

PubMed

Fekete, Szabolcs; Fekete, Jeno

2011-04-15

The performance of 5 cm long narrow-bore columns packed with 2.6-2.7 μm core-shell particles and a column packed with 1.7 μm totally porous particles was compared in very fast gradient separations of polar neutral active pharmaceutical compounds. Peak capacities as a function of flow-rate and gradient time were measured. Peak capacities around 160-170 could be achieved within 25 min with these 5 cm long columns. The highest peak capacity was obtained with the Kinetex column however it was found that as the flow-rate increases, the peak capacity of the new Poroshell-120 column is getting closer to that obtained with the Kinetex column. Considering the column permeability, peak capacity per unit time and per unit pressure was also calculated. In this comparison the advantage of sub-3 μm core-shell particles is more significant compared to sub-2 μm totally porous particles. Moreover it was found that the very similar sized (d(p)=2.7 μm) and structured (ρ=0.63) new Poroshell-120 and the earlier introduced Ascentis Express particles showed different efficiency. Results obtained showed that the 5 cm long narrow bore columns packed with sub-3 μm core-shell particles offer the chance of very fast and efficient gradient separations, thus these columns can be applied for fast screening measurements of routine pharmaceutical analysis such as cleaning validation. Copyright © 2011 Elsevier B.V. All rights reserved.

Variational Assimilation of GOME Total-Column Ozone Satellite Data in a 2D Latitude-Longitude Tracer-Transport Model.

NASA Astrophysics Data System (ADS)

Eskes, H. J.; Piters, A. J. M.; Levelt, P. F.; Allaart, M. A. F.; Kelder, H. M.

1999-10-01

A four-dimensional data-assimilation method is described to derive synoptic ozone fields from total-column ozone satellite measurements. The ozone columns are advected by a 2D tracer-transport model, using ECMWF wind fields at a single pressure level. Special attention is paid to the modeling of the forecast error covariance and quality control. The temporal and spatial dependence of the forecast error is taken into account, resulting in a global error field at any instant in time that provides a local estimate of the accuracy of the assimilated field. The authors discuss the advantages of the 4D-variational (4D-Var) approach over sequential assimilation schemes. One of the attractive features of the 4D-Var technique is its ability to incorporate measurements at later times t > t0 in the analysis at time t0, in a way consistent with the time evolution as described by the model. This significantly improves the offline analyzed ozone fields.

Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

NASA Astrophysics Data System (ADS)

Yao, Guisheng; Li, Yong; Jiang, Peng; Jin, Xiuming; Long, Menglong; Qin, Haixia; Kumar, R. Vasant

2017-04-01

Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si3N4 and Si2N2O are formed as the nitridation products in the samples. Fibroid and short columnar Si3N4 are detected in the samples. The formation mechanisms of Si3N4 and Si2N2O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O2 in N2 atmosphere, forming a thin film of SiO2 on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO2 film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO2 film will crack, and N2 is infiltrated into the central section of the sample through cracks, generating Si2N2O and short columnar Si3N4 in situ. At the same time, metastable SiO(g) reacts with N2 and form fibroid Si3N4. In the regions where the oxygen partial pressure is high, Si3N4 is oxidized into Si2N2O.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils.

PubMed

Samad, Md Sainur; Biswas, Ambarish; Bakken, Lars R; Clough, Timothy J; de Klein, Cecile A M; Richards, Karl G; Lanigan, Gary J; Morales, Sergio E

2016-10-26

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N 2 O and N 2 emissions. Soil pH regulates the reduction of N 2 O to N 2 , however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N 2 O emission ratio (N 2 O/(NO + N 2 O + N 2 )) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N 2 O emission ratio and community changes. Soil pH was negatively associated with N 2 O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir &nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N 2 O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N 2 O emission ratio through more efficient conversion of N 2 O to N 2 .

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

NASA Astrophysics Data System (ADS)

Samad, M. D. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-10-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

PubMed Central

Samad, M. d. Sainur; Biswas, Ambarish; Bakken, Lars R.; Clough, Timothy J.; de Klein, Cecile A. M.; Richards, Karl G.; Lanigan, Gary J.; Morales, Sergio E.

2016-01-01

Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2. PMID:27782174

Ab initio studies on Al(+)(H(2)O)(n), HAlOH(+)(H(2)O)(n-1), and the size-dependent H(2) elimination reaction.

PubMed

Siu, Chi-Kit; Liu, Zhi-Feng; Tse, John S

2002-09-11

We report computational studies on Al(+)(H(2)O)(n), and HAlOH(+)(H(2)O)(n-1), n = 6-14, by the density functional theory based ab initio molecular dynamics method, employing a planewave basis set with pseudopotentials, and also by conventional methods with Gaussian basis sets. The mechanism for the intracluster H(2) elimination reaction is explored. First, a new size-dependent insertion reaction for the transformation of Al(+)(H(2)O)(n), into HAlOH(+)(H(2)O)(n-1) is discovered for n > or = 8. This is because of the presence of a fairly stable six-water-ring structure in Al(+)(H(2)O)(n) with 12 members, including the Al(+). This structure promotes acidic dissociation and, for n > or = 8, leads to the insertion reaction. Gaussian based BPW91 and MP2 calculations with 6-31G* and 6-31G** basis sets confirmed the existence of such structures and located the transition structures for the insertion reaction. The calculated transition barrier is 10.0 kcal/mol for n = 9 and 7.1 kcal/mol for n = 8 at the MP2/6-31G** level, with zero-point energy corrections. Second, the experimentally observed size-dependent H(2) elimination reaction is related to the conformation of HAlOH(+)(H(2)O)(n-1), instead of Al(+)(H(2)O)(n). As n increases from 6 to 14, the structure of the HAlOH(+)(H(2)O)(n-1) cluster changes into a caged structure, with the Al-H bond buried inside, and protons produced in acidic dissociation could then travel through the H(2)O network to the vicinity of the Al-H bond and react with the hydride H to produce H(2). The structural transformation is completed at n = 13, coincident approximately with the onset of the H(2) elimination reaction. From constrained ab initio MD simulations, we estimated the free energy barrier for the H(2) elimination reaction to be 0.7 eV (16 kcal/mol) at n = 13, 1.5 eV (35 kcal/mol) at n = 12, and 4.5 eV (100 kcal/mol) at n = 8. The existence of transition structures for the H(2) elimination has also been verified by ab initio calculations

Multiannual tropical tropospheric ozone columns and the case of the 2015 el Niño event

NASA Astrophysics Data System (ADS)

Leventidou, Elpida; Eichmann, Kai-Uwe; Weber, Mark; Burrows, John P.

2016-04-01

Stratospheric ozone is well known for protecting the surface from harmful ultraviolet solar radiation whereas ozone in the troposphere plays a more complex role. In the lower troposphere ozone can be extremely harmful for human health as it can oxidize biological tissues and causes respiratory problems. Several studies have shown that the tropospheric ozone burden (300±30Tg (IPCC, 2007)) increases by 1-7% per decade in the tropics (Beig and Singh, 2007; Cooper et al., 2014) which makes the need to monitor it on a global scale crucial. Remote sensing from satellites has been proven to be very useful in providing consistent information of tropospheric ozone concentrations over large areas. Tropical tropospheric ozone columns can be retrieved with the Convective Cloud Differential (CCD) technique (Ziemke et al. 1998) using retrieved total ozone columns and cloud parameters from space-borne observations. We have developed a CCD-IUP algorithm which was applied to GOME/ ERS-2 (1995-2003), SCIAMACHY/ Envisat (2002-2012), and GOME-2/ MetOpA (2007-2012) weighting function DOAS (Coldewey-Egbers et al., 2005, Weber et al., 2005) total ozone data. A unique long-term record of monthly averaged tropical tropospheric ozone columns (20°S - 20°N) was created starting in 1996. This dataset has been extensively validated by comparisons with SHADOZ (Thompson et al., 2003) ozonesonde data and limb-nadir Matching (Ebojie et al. 2014) tropospheric ozone data. The comparison shows good agreement with respect to range, inter-annual variation, and variance. Biases where found to be within 5DU and the RMS errors less than 10 DU. This 17-years dataset has been harmonized into one consistent time series, taking into account the three instruments' difference in ground pixel size. The harmonised dataset is used to determine tropical tropospheric ozone trends and climatological values. The 2015 el Niño event has been characterised as one of the top three strongest el Niños since 1950. El Niño

Partitioning Residue-derived and Residue-induced Emissions of N2O Using 15N-labelled Crop Residues

NASA Astrophysics Data System (ADS)

Farrell, R. E.; Carverhill, J.; Lemke, R.; Knight, J. D.

2014-12-01

Estimates of N2O emissions in Canada indicate that 17% of all agriculture-based emissions are associated with the decomposition of crop residues. However, research specific to the western Canadian prairies (including Saskatchewan) has shown that the N2O emission factor for N sources in this region typically ranges between 0.2 and 0.6%, which is well below the current IPCC default emission factor of 1.0%. Thus, it stands to reason that emissions from crop residues should also be lower than those calculated using the current IPCC emission factor. Current data indicates that residue decomposition, N mineralization and N2O production are affected by a number of factors such as C:N ratio and chemical composition of the residue, soil type, and soil water content; thus, a bench-scale incubation study was conducted to examine the effects of soil type and water content on N2O emissions associated with the decomposition of different crop residues. The study was carried out using soils from the Black, Dark Brown, Brown, and Gray soil zones and was conducted at both 50% and 70% water-filled pore space (WFPS); the soils were amended with 15N-labeled residues of wheat, pea, canola, and flax, or with an equivalent amount of 15N-labeled urea; 15N2O production was monitored using a Picarro G5101-i isotopic N2O analyzer. Crop residue additions to the soils resulted in both direct and indirect emissions of N2O, with residue derived emissions (RDE; measured as 15N2O) generally exceeding residue-induced emissions (RIE) at 50% WFPS—with RDEs ranging from 42% to 88% (mean = 58%) of the total N2O. Conversely, at 70% WFPS, RDEs were generally lower than RIEs—ranging from 21% to 83% (mean = 48%). Whereas both water content and soil type had an impact on N2O production, there was a clear and consistent trend in the emission factors for the residues; i.e., emissions were always greatest for the canola residue and lowest for the wheat residue and urea fertilizer; and intermediate for pea

Mechanism of nucleation and growth of catalyst-free self-organized GaN columns by MOVPE

NASA Astrophysics Data System (ADS)

Wang, Xue; Li, Shunfeng; Fündling, Sönke; Wehmann, Hergo-H.; Strassburg, Martin; Lugauer, Hans-Jürgen; Steegmüller, Ulrich; Waag, Andreas

2013-05-01

The growth mechanism of catalyst-free self-organized GaN nuclei and three-dimensional columns on sapphire by metal organic vapour phase epitaxy (MOVPE) is investigated. Temperature- and time-dependent growth is performed. The growth behaviour can be characterized by two different kinetic regimes: mass-transport-limited growth and thermodynamically limited growth. The sum of activation energies for thermodynamic barrier of nucleation and for surface diffusion/mass-transport limitation, i.e. Whet +Ed, is 0.57 eV in the ‘low’-temperature region and 2.43 eV in the ‘high’-temperature region. GaN columns grown under the same conditions have very comparable height, which is not dependent on their diameter or the distance to other columns. Therefore, the growth rate is presumably limited by the incorporation rate on the top surface of columns. The height and diameter at the top of the GaN columns increase linearly with time and no height limit is observed. The GaN columns can reach more than 40 µm in height. Moreover, the investigated GaN columns are Ga-polar.

Microcosm N2O emissions wth calibration

EPA Pesticide Factsheets

The dataset consists of measurements of soil nitrous oxide emissions from soils under three different amendments: glucose, cellulose, and manure. Data includes the four isotopomers of nitrous oxide (14N15N16O, 15N14N16O, 14N14N18O, 14N14N16O), and the site preference.This dataset is associated with the following publication:Chen , H., D. Williams , P. Deshmukh , F. Birgand, B. Maxwell, and J. Walker. Probing the Biological Sources of Soil N2O Emissions by Quantum Cascade Laser-Based 15N Isotopocule Analysis. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. Soil Science Society of America, Madison, WI, USA, 100(0): 175-181, (2016).

40 CFR 1065.375 - Interference verification for N2O analyzers.

Code of Federal Regulations, 2013 CFR

2013-07-01

... interference verification as follows: (1) Start, operate, zero, and span the N2O analyzer as you would before... possible to the inlet of the analyzer. For example, measure dewpoint, T dew, and absolute pressure, p total...

40 CFR 1065.375 - Interference verification for N2O analyzers.

Code of Federal Regulations, 2010 CFR

2010-07-01

... interference verification as follows: (1) Start, operate, zero, and span the N2O analyzer as you would before... possible to the inlet of the analyzer. For example, measure dewpoint, T dew, and absolute pressure, p total...

40 CFR 1065.375 - Interference verification for N2O analyzers.

Code of Federal Regulations, 2014 CFR

2014-07-01

... interference verification as follows: (1) Start, operate, zero, and span the N2O analyzer as you would before... possible to the inlet of the analyzer. For example, measure dewpoint, T dew, and absolute pressure, p total...

40 CFR 1065.375 - Interference verification for N2O analyzers.

Code of Federal Regulations, 2011 CFR

2011-07-01

... interference verification as follows: (1) Start, operate, zero, and span the N2O analyzer as you would before... possible to the inlet of the analyzer. For example, measure dewpoint, T dew, and absolute pressure, p total...