Interactive effects of low molecular weight carbon compounds on N2O emissions

Low molecular weight carbon (C) compounds in hotspots such as the rhizosphere can greatly affect nitrate reduction processes. Towards a better prediction of N2O emission from denitrification, we are still lacking understanding of responses to the supply of complex C compound mixtures such as rhizodeposits versus the often examined response to individually amended C compounds. In a laboratory study, we applied three C compounds, glucose, citric acid and glutamic acid, individually or as a three-compound mixture to 14NH415NO3 amended soil at 80% water-filled pore space. For the individual C compound treatments, the substrateswere enriched in 13C-C. The mixture was enriched in 13C-C either in all constituent compounds or in one of the compounds only, resulting in four different treatments. This set-up enabled quantification of the utilization of each compound for heterotrophic respiration when applied individually and in combination, and for this to be related to the dynamics of 15N-NO3- reduction to 15N-N2O. The total 15N-N2O emission from the compound mixture over 10 days was similar to the total emission predicted from the average of the individual compound treatments This could suggest potential predictability of denitrification responses to complex mixtures of C based on knowledge of its constituents. However, immediate and simultaneous peaks of 15N-N2O and 13C-CO2 fluxes from the compound mixture contrasted with observed delays in 15N-N2O and 13C-CO2 fluxes when the compounds had been applied individually. Moreover, relative contributions of the C compounds to 13C-CO2 respiration from the compound mixture were different from the predicted contributions based on their individual application. While contributions of glutamic acid-C and citric acid-C to respiration in mixture during peak 15N-N2O emission were increased, glucose utilization in the mixture treatment was significantly lower. These findings give a glimpse of the challenges we are facing when trying to predict nitrate reduction occurring in the rhizosphere where interactions between C compounds and the soil matrix, as well as within the wider heterotrophic community, determine process rates. Given that most of our understanding of the role of C in regulating nitrate reduction, is informed from single compound studies, we require more evidence on the effects and innate interactions of compound mixtures to be able to predict responses to C sources

The Theory of Brown Dwarfs and Extrasolar Giant Planets

Straddling the traditional realms of the planets and the stars, objects below the edge of the main sequence have such unique properties, and are being discovered in such quantities, that one can rightly claim that a new field at the interface of planetary science and and astronomy is being born. In this review, we explore the essential elements of the theory of brown dwarfs and giant planets, as well as of the new spectroscopic classes L and T. To this end, we describe their evolution, spectra, atmospheric compositions, chemistry, physics, and nuclear phases and explain the basic systematics of substellar-mass objects across three orders of magnitude in both mass and age and a factor of 30 in effective temperature. Moreover, we discuss the distinctive features of those extrasolar giant planets that are irradiated by a central primary, in particular their reflection spectra, albedos, and transits. Aspects of the latest theory of Jupiter and Saturn are also presented. Throughout, we highlight the effects of condensates, clouds, molecular abundances, and molecular/atomic opacities in brown dwarf and giant planet atmospheres and summarize the resulting spectral diagnostics. Where possible, the theory is put in its current observational context.Comment: 67 pages (including 36 figures), RMP RevTeX LaTeX, accepted for publication in the Reviews of Modern Physics. 30 figures are color. Most of the figures are in GIF format to reduce the overall size. The full version with figures can also be found at: http://jupiter.as.arizona.edu/~burrows/papers/rm

MEASUREMENTS of BAND INTENSITIES, HERMAN-WALLIS PARAMETERS, and SELFBROADENING LINE-WIDTHS of the 30011←0000130011\leftarrow 00001 and 30014←0000130014\leftarrow 00001 BANDS of CO2CO_{2} at 6503cm−16503 cm^{-1} and 6076cm−16076 cm^{-1}.

Author Institution: California Institute of Technology, Pasadena, CA 91109.; Ames Research Center, Moffett Field, CA 94035-1000.; Utah State University, Bedford, MA.Rotationless band intensities and Herman-Wallis parameters are listed in HITRAN tabulations (Rothman, et al. J.Q.S.R.T. 48, 537, 1992) for several hundred $CO_{2}$ overtone-combination bands. These parameters are based on laboratory measurements when available, and on DND calculations for the unmeasured bands. The DND calculations for the Fermi interacting $n\nu_{1} + \nu_{3}$ polyads show the $a_{2}$ Herman Wallis parameter varying smoothy from a negative valu for the first member of the polyad to a positive value for the final member. Johns' (J. Mol. Spec. 134, 433, 1989) measurements of the $\nu_{1} + \nu_{3}$ dyad are consistent with the DND calculations for the $a_{2}$ parameter, as are our recent measurements (submitted to J. Mol. Spec.) of the $4\nu_{1} + \nu_{3}$ pentad. However, the measurement-based values in the HITRAN tables for the $2\nu_{1} + \nu_{3}$ triad and the $3\nu_{1} + \nu_{3}$ tetrad do not support the DND calculated values for the $a_{2}$ parameters. We therefore decided to make new measurements to improve some of these intensity parameters. With the McMath FTS at Kitt Peak National Observatory/National Solar Observatory we recorded several spectra of the 4000 to $8000 cm^{-1}$ region of pure $CO_{2}$ at $0.011 cm^{-1}$ resolution using the 6 meter White absorption cell. The signal/noise and absorbance of the first and fourth bands of the $3\nu_{1} + \nu_{3}$ tetrad of $^{12}C{^{16}O_{2}}$ were ideal on these spectra for measuring line intensities and broadening widths. Our selfbroadening results agree with the HITRAN paramaterization, while our measurements of the rotationless band intensities are about 15% less than the HITRAN values. We find a negative value of $a_{2}$ for the $30011\leftarrow 00001$ band and a positive values for the $30014\leftarrow 00001$ band, whereas the HITRAN values of $a_{2}$ are positive for all four tetrad bands. Our $a_{1}$ and $a_{2}$ Herman-Wallis parameters are closer to DND calculated values than the 1992 HITRAN values for both the $30011\leftarrow 00001$ and the $30014\leftarrow 00001$ band

Reprint of: The HITRAN molecular spectroscopic database and HAWKS (HITRAN Atmospheric Workstation): 1996 edition

International audienc