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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

NGEE Arctic Tram: Periodic Soil CO2 and CH4 Flux Chamber Measurements across Polygonal Tundra, Utqiagvik (Barrow), Alaska, 2014-2017

Soil chamber flux measurements made from a 2014-2017 adjacent to the TRAM system, with measurements referenced to TRAM stop numbers. Dataset includes measurements using transparent and opaque chambers (CO2 and CH4 fluxes in light and dark). The Tram location was selected to be in the footprint of the NGEE Arctic AmeriFlux tower (US-NGB). Measurement stop positions are at 0.5 m intervals (1-137) over the 68 m Tram track. Dataset includes one CSV data file and one user guide in PDF. The Next-Generation Ecosystem Experiments: Arctic (NGEE Arctic), was a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1971

Physisorption of Ar, Kr, CH4, and N2 on 304 stainless steel at very low pressures.

Determination of physisorption isotherms of these gases on stainless steel by pressure change measurements in very low pressure cryogenic baths where a steel nipple was brought in contact with the test gas at 77 to 90 K in a sealed constant-volume system. The position of the nipple in the gas was changed in such a manner that gas adsorption on a 47.5 sq cm area of the steel surface could be measured. The Dubinin-Radushkevich (DR) equation (1947) was used for an empirical description of isotherms at different temperatures. The mean adsorption energies calculated from the DR plots were 1290, 1545, 1490 and 1903 cal/mol for Ar, Kr, CH4 and N2, respectively, being about 10% higher than the corresponding values on Pyrex.

Troy, M.↗
NASA NTRS1974

Dissociation of CH4 by electron impact: Production of metastable hydrogen and carbon fragments

Metastable fragments produced by electron impact excitation of CH4 have been investigated for incident electron energies from threshold to 300 eV. Only metastable hydrogen and carbon atoms were observed. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0 + or - .5 eV, 25.5 + or - .6 eV, 36.7 + or - .6 eV and 66 + or - 3 eV, and at 26.6 + or - .6 eV for the production of metastable carbon atoms. Most of the fragments appear to have been formed in high-lying Rydberg states. The total metastable hydrogen cross section reaches a maximum value of approximately 1 X 10 to the minus 18th power sq cm at 100 eV. At the same energy, the metastable carbon cross section is 2 x 10 to the minus 19th power sq cm.

Finn, T. G.↗
NASA NTRS1974

VUV dissociative excitation cross sections of H2O, NH3, and CH4 by electron impact

Absolute excitation functions for excited fragments resulting from electron bombardment of H2O, NH3, and CH4 by low-energy electrons (0 to 300 eV) have been measured in the vacuum ultraviolet (1100 to 1950 A). The predominant emission for each molecule was the H Lyman-alpha line, while the O I, N I, C I, and C II emissions were at least an order of magnitude weaker. Absolute cross sections at 100 eV are given along with the appearance potential of the various processes and the possible dissociative-excitation channels through which such processes proceed.

Morgan, H. D.↗
NASA NTRS1975

Further development of a global pollution model for CO, CH4, and CH2 O

Global tropospheric pollution models are developed that describe the transport and the physical and chemical processes occurring between the principal sources and sinks of CH4 and CO. Results are given of long term static chemical kinetic computer simulations and preliminary short term dynamic simulations.

Peters, L. K.↗
NASA NTRS1976

A temperature dependence kinetics study of the reactions of Cl/2-P-3/2/ with O3, CH4, and H2O2

The temperature dependence of two chlorine atom reactions of considerable fundamental importance to stratospheric chemistry was studied using the technique of flash photolysis-resonance fluorescence. The reactions of interest were: (1) Cl + O3 yields ClO + O2 studied at 220-350 K, and (2) Cl + CH4 yields CH3 + HCl studied at 218-401 K. In addition, the reaction Cl + H2O2 yields HCl + HO2 was studied at 300 K. The corresponding rate constants are provided for the three reactions. The new rate data implies the need to revise downward by a factor of 2.4-3 the magnitude of the ozone perturbation due to the presence of ClO/x/ species in the stratosphere, predicted by earlier model calculations.

Watson, R.↗
NASA NTRS1979

On the CH4 nu-4 fundamental controversy - Line-intensity measurements revisited

Because of the controversy over the value of the band strength for the nu-4 fundamental of CH4, equivalent widths of the R(0), R(1), and P(11, 11, F1) lines have been measured to compare with opposing views. The present measurements are consistent with the band strength of Ko and Varanasi (1977), who, on the basis of high-resolution line-strength measurements, propose an integrated band strength of 145 kaysers/(cm-am).

Lutz, B. L.↗