Search results for "Optical absorption spectroscopy"

Inter-comparison of stratospheric O<sub>3</sub> and NO<sub>2</sub> abundances retrieved from …

2006

Abstract. Stratospheric O3 and NO2 abundances measured by different remote sensing instruments are inter-compared: (1) Line-of-sight absorptions and vertical profiles inferred from solar spectra in the ultra-violet (UV), visible and infrared (IR) wavelength ranges measured by the LPMA/DOAS (Limb Profile Monitor of the Atmosphere/Differential Optical Absorption Spectroscopy) balloon payload during balloon ascent/descent and solar occultation are examined with respect to internal consistency. (2) The balloon borne stratospheric profiles of O3 and NO2 are compared to collocated space-borne skylight limb observations of the Envisat/SCIAMACHY satellite instrument. The trace gas profiles are retr…

2016

Abstract. Scanning spectrometer networks using scattered solar radiation in the ultraviolet spectral region have become an increasingly important tool for monitoring volcanic sulfur dioxide (SO2) emissions. Often measured spectra are evaluated using the differential optical absorption spectroscopy (DOAS) technique. In order to obtain absolute column densities (CDs), the DOAS evaluation requires a Fraunhofer reference spectrum (FRS) that is free of absorption structures of the trace gas of interest. For measurements at volcanoes such a FRS can be readily obtained if the scan (i.e. series of measurements at different elevation angles) includes viewing directions where the plume is not seen. I…

Gas emission strength and evolution of the molar ratio of BrO/SO2in the plume of Nyiragongo in comparison to Etna

2015

Airborne and ground-based differential optical absorption spectroscopy observations have been carried out at the volcano Nyiragongo (Democratic Republic of Congo) to measure SO2 and bromine monoxide (BrO) in the plume in March 2004 and June 2007, respectively. Additionally filter pack and multicomponent gas analyzer system (Multi-GAS) measurements were carried out in June 2007. Our measurements provide valuable information on the chemical composition of the volcanic plume emitted from the lava lake of Nyiragongo. The main interest of this study has been to investigate for the first time the bromine emission flux of Nyiragongo (a rift volcano) and the BrO formation in its volcanic plume. Mea…

Reactive halogen chemistry in volcanic plumes

2007

[1] Bromine monoxide (BrO) and sulphur dioxide (SO2) abundances as a function of the distance from the source were measured by ground-based scattered light Multiaxis Differential Optical Absorption Spectroscopy (MAX-DOAS) in the volcanic plumes of Mt. Etna on Sicily, Italy, in August–October 2004 and May 2005 and Villarica in Chile in November 2004. BrO and SO2 spatial distributions in a cross section of Mt. Etna's plume were also determined by Imaging DOAS. We observed an increase in the BrO/SO2 ratio in the plume from below the detection limit near the vent to about 4.5 × 10−4 at 19 km (Mt. Etna) and to about 1.3 × 10−4 at 3 km (Villarica) distance, respectively. Additional attempts were …

Active alkaline traps to determine acidic-gas ratios in volcanic plumes: Sampling techniques and analytical methods

2014

In situ measurements have been the basis for monitoring volcanic gas emissions for many years and—being complemented by remote sensing techniques—still play an important role to date. Con- cerning in situ techniques for sampling a dilute plume, an increase in accuracy and a reduction of detection limits are still necessary for most gases (e.g., CO2, SO2, HCl, HF, HBr, HI). In this work, the Raschig-Tube tech- nique (RT) is modified and utilized for application on volcanic plumes. The theoretical and experimental absorption properties of the RT and the Drechsel bottle (DB) setups are characterized and both are applied simultaneously to the well-established Filter packs technique (FP) in the …

DOAS Measurements of Iodine Oxides in the Framework of the MAP (Marine Aerosol Production) Project

2007

Evaluation of the coupled high-resolution atmospheric chemistry model system MECO(n) using in situ and MAX-DOAS NO<sub>2</sub&am…

2021

Abstract. We present high spatial resolution (up to 2.2×2.2 km2) simulations focussed over south-west Germany using the online coupled regional atmospheric chemistry model system MECO(n) (MESSy-fied ECHAM and COSMO models nested n times). Numerical simulation of nitrogen dioxide (NO2) surface volume mixing ratios (VMRs) are compared to in situ measurements from a network with 193 locations including background, traffic-adjacent and industrial stations to investigate the model's performance in simulating the spatial and temporal variability of short-lived chemical species. We show that the use of a high-resolution and up-to-date emission inventory is crucial for reproducing the spatial varia…

Local dynamic properties of the heme pocket in native and solvent-induced molten-globule-like states of cytochrome c

2002

We report the Soret absorption band, down to cryogenic temperature, of native and molten-globule-like state of horse heart cytochrome c. The band profile is analyzed in terms of vibronic coupling of the heme normal modes to the electronic transition in the framework of the Franck-Condon approximation. From the temperature dependence of the Gaussian broadening and of the peak position, we obtain information on the 'bath' of low frequency harmonic motions of the heme group within the heme pocket. The reported data indicate that, compared to the native state, the less rigid tertiary structure of the molten globule is reflected in a higher flexibility of the heme pocket and in greater conformat…

In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O<sub>3</…

2010

Abstract. Discrete in situ atmospheric measurements of molecular iodine (I2) were carried out at Mace Head and Mweenish Bay on the west coast of Ireland using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. I2, IO and OIO were also measured by long-path differential optical absorption spectroscopy (LP-DOAS). The simultaneous denuder and LP-DOAS I2 measurements were well correlated (R2=0.80) but the denuder method recorded much higher concentrations. This can be attributed to the fact that the in situ measurements were made near to macroalgal sources of I2 in the intertidal zone, whereas the LP-DOAS technique provides distance-averaged mixing rat…

Methane line parameters in the HITRAN2012 database

2013

International audience; The compilation of methane molecular line parameters was updated to include new global analyses and measurements for 12CH4, 13CH4 and 12CH3D. Over 70% of the methane parameters in HITRAN2008 were replaced; existing parameters retained were the microwave lines and the Dyad of 13CH4 near 7 μm and ν6 of 13CH3D near 8.7 μm, 12CH3D (7-4076 cm-1), hot bands of 12CH4 (1887-3370 cm-1) and normal sample CH4 (4800-5550 cm-1 and 8000-9200 cm-1). With a minimum intensity at 296 K in units of cm-1/(molecule cm-2) set to 10-37 for the far-IR and 10-29 for the mid- and near-IR, the methane database increased from 290,091 lines in HITRAN2008 to 468,013 lines, and three-fourths of th…