A coordinated action involving eleven stations of the ground-based Network for Detection of Strat... more A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to contribute to the validation of the three atmospheric ...
While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occur... more While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occurring and well-understood phenomenon, dynamical variability in the Arctic stratosphere means ozone depletion in the northern polar vortex is both less predictable and more susceptible to changes resulting from climate change than in the southern vortex. In order to examine ozone-depleting processes and quantify chemical changes occurring
Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detecte... more Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detected from the ground and from space
The Solar Occultation Flux (SOF) method and mobile DOAS technique were used to measure industrial... more The Solar Occultation Flux (SOF) method and mobile DOAS technique were used to measure industrial emissions of volatile organic compounds, formaldehyde, NO2 and SO2 in the Houston area during the time period April 15 to June 11, 2009. The measurements were conducted as part of the campaign FLAIR (Formaldehyde and alkenes from Large Industrial Releases) with the aim to better understand the role of formaldehyde for the photochemical production of ozone. The SOF technique is an optical method utilizing the absorption of direct solar infrared radiation in the 1.8-14 µm range for the retrieval of total columns of various species such as ethylene, propylene, ammonia and alkanes. Mobile DOAS utilizes scattered light in the ultraviolet spectral region for measurements of HCHO, SO2 and NO2. A crude chemical model has been applied to interprete whether the measured formaldehyde in the industrial emission plumes is primary emitted or secondary produced from oxidation of alkenes. The measured emissions of alkenes in the Houston Ship channel area were a factor of 10 higher than reported in the emission inventories and corresponded to about 600 kg/h for both ethene and propene. Several individual industrial sources of formaldehyde were identified in the Houston area. The emissions from these sources were relativaly small and ranged from a few kg/h up to over 40 kg/h. In most cases it was interpreted with the model that these corresponded to primary emissions of formaldehyde. However, a few large scale measurements further downwind the Houston ship channel showed formaldehyde fluxes (over 1000 kg/h) that could not be explained by the sum of the individual sources measured. These numbers are consistent with secondary production of formaldehyde from the alkene sources. Our conclusion is hence that the dominant part of the formaldehyde around the the Houston ship channel is being secondary produced from alkenes rather than coming from direct emissions.
Atmospheric Chemistry and Physics Discussions, 2007
This paper describes the statistical analysis of annual trends in long term datasets of greenhous... more This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European
Instrument Development for Atmospheric Research and Monitoring, 1997
The work accomplished during the period 1990 to 1995 by the three Belgian groups participating in... more The work accomplished during the period 1990 to 1995 by the three Belgian groups participating in the EUROTRAC-TOPAS project is described. It involved the construction and permanent improvement of two DOAS (Differential Optical Absorption Spectroscopy) spectrometers. One of these is a Fourier transform instrument which was applied to atmospheric measurements in the Visible-UV region for the first time. Long path absorption set-ups were constructed. Software was developped to operate and automate the instruments and specific algorithms were written for the retrieval of concentrations from the atmospheric spectra. Both instruments were validated by participating in two EUROTRAC-TOPAS intercomparison campaigns which gathered instruments from six european countries. Finaly, high resolution absorption cross sections of several atmospherically relevant species were measured in the laboratory.
We present absorption spectra as a function of temperature for CdTe quantum dots in doped glasses... more We present absorption spectra as a function of temperature for CdTe quantum dots in doped glasses. We calculate the absorption spectra considering the transition energies from a spherical 0268-1242/14/1/007/img9 model. We consider also the inhomogeneous broadening due to the quantum-dot size distribution and the homogeneous broadening, due mainly to electron-phonon interactions. The samples grown with a two-step heat treatment present very thin size distributions, with a standard deviation of 5.8%, which is comparable to the best CdSe samples in the literature. Also, the results show that the homogeneous width increases as the quantum-dot size decreases, indicating an enhancement of the electron-phonon interaction for small dots.
A coordinated action involving eleven stations of the ground-based Network for Detection of Strat... more A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to contribute to the validation of the three atmospheric ...
While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occur... more While chemical ozone depletion in the Antarctic spring-time stratosphere is now an annually occurring and well-understood phenomenon, dynamical variability in the Arctic stratosphere means ozone depletion in the northern polar vortex is both less predictable and more susceptible to changes resulting from climate change than in the southern vortex. In order to examine ozone-depleting processes and quantify chemical changes occurring
Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detecte... more Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detected from the ground and from space
The Solar Occultation Flux (SOF) method and mobile DOAS technique were used to measure industrial... more The Solar Occultation Flux (SOF) method and mobile DOAS technique were used to measure industrial emissions of volatile organic compounds, formaldehyde, NO2 and SO2 in the Houston area during the time period April 15 to June 11, 2009. The measurements were conducted as part of the campaign FLAIR (Formaldehyde and alkenes from Large Industrial Releases) with the aim to better understand the role of formaldehyde for the photochemical production of ozone. The SOF technique is an optical method utilizing the absorption of direct solar infrared radiation in the 1.8-14 µm range for the retrieval of total columns of various species such as ethylene, propylene, ammonia and alkanes. Mobile DOAS utilizes scattered light in the ultraviolet spectral region for measurements of HCHO, SO2 and NO2. A crude chemical model has been applied to interprete whether the measured formaldehyde in the industrial emission plumes is primary emitted or secondary produced from oxidation of alkenes. The measured emissions of alkenes in the Houston Ship channel area were a factor of 10 higher than reported in the emission inventories and corresponded to about 600 kg/h for both ethene and propene. Several individual industrial sources of formaldehyde were identified in the Houston area. The emissions from these sources were relativaly small and ranged from a few kg/h up to over 40 kg/h. In most cases it was interpreted with the model that these corresponded to primary emissions of formaldehyde. However, a few large scale measurements further downwind the Houston ship channel showed formaldehyde fluxes (over 1000 kg/h) that could not be explained by the sum of the individual sources measured. These numbers are consistent with secondary production of formaldehyde from the alkene sources. Our conclusion is hence that the dominant part of the formaldehyde around the the Houston ship channel is being secondary produced from alkenes rather than coming from direct emissions.
Atmospheric Chemistry and Physics Discussions, 2007
This paper describes the statistical analysis of annual trends in long term datasets of greenhous... more This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European
Instrument Development for Atmospheric Research and Monitoring, 1997
The work accomplished during the period 1990 to 1995 by the three Belgian groups participating in... more The work accomplished during the period 1990 to 1995 by the three Belgian groups participating in the EUROTRAC-TOPAS project is described. It involved the construction and permanent improvement of two DOAS (Differential Optical Absorption Spectroscopy) spectrometers. One of these is a Fourier transform instrument which was applied to atmospheric measurements in the Visible-UV region for the first time. Long path absorption set-ups were constructed. Software was developped to operate and automate the instruments and specific algorithms were written for the retrieval of concentrations from the atmospheric spectra. Both instruments were validated by participating in two EUROTRAC-TOPAS intercomparison campaigns which gathered instruments from six european countries. Finaly, high resolution absorption cross sections of several atmospherically relevant species were measured in the laboratory.
We present absorption spectra as a function of temperature for CdTe quantum dots in doped glasses... more We present absorption spectra as a function of temperature for CdTe quantum dots in doped glasses. We calculate the absorption spectra considering the transition energies from a spherical 0268-1242/14/1/007/img9 model. We consider also the inhomogeneous broadening due to the quantum-dot size distribution and the homogeneous broadening, due mainly to electron-phonon interactions. The samples grown with a two-step heat treatment present very thin size distributions, with a standard deviation of 5.8%, which is comparable to the best CdSe samples in the literature. Also, the results show that the homogeneous width increases as the quantum-dot size decreases, indicating an enhancement of the electron-phonon interaction for small dots.
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