2 edition of measurement of hydroxyl radical concentrations in tropospheric air found in the catalog.
measurement of hydroxyl radical concentrations in tropospheric air
Charles William Blankenship
Written in English
|Statement||by Charles William Blankenship, Jr.|
|The Physical Object|
|Pagination||vii, 53 leaves ;|
|Number of Pages||53|
two hydroxyl (OH) radicals is accepted as the dominant tropospheric primary radical source, multiple other primary radical sources exist and can dominate in certain environments. In this work we use a series of model simulations to investigate if the nature of the primary radical matters. The OH radical is.
Atmospheric Environment Vol. Printed in Great Britain. / + Pergamon Press Ltd. TROPOSPHERIC CONCENTRATIONS OF THE HYDROXYL RADICAL REVIEW C.
HEWITT and ROY M. HARRISON*+ Department of Environmental Sciences, University of Lancaster, Lancaster LAI 4YQ, U.K. (first received 11 January and received/or Cited by: The dominant role played by the hydroxyl radical in tropospheric photochemistry makes essential a better definition of its atmospheric abundance.
The measurement techniques employed to date are critically evaluated and the reported concentrations of HO in ambient air are by: surface measurements of hydroxyl radicals in urban and rural ar-eas.
Predictions of average tropospheric, hemispheric and/or zonal concentrations of hydroxyl radicals derived from methylchloroform and carbon monoxide concentrations and models are discussed.
The limitations of one- and two-dimensional model predictions of zonal and seasonal. The hydroxyl radical, OH, initiates the removal of the majority of trace gases in the atmosphere, and together with the closely coupled species, the hydroperoxy radical, HO(2), is intimately.
Absolutely calibrated in-situ measurements of tropospheric hydroxyl radicals, formaldehyde, sulfur dioxide, In total, identifications of OH in air spectra were made in a rural environment between August 5 and Aug The observed maximum and median OH radical concentrations are OH/cm3 and OH/cm3 Cited by: During the last three years, this system has been flown s air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S.
OH concentrations measured during. Aspects of Modeling the Tropospheric Hydroxyl Radical Concentration. Israel Journal of Chemistry34 (), DOI: /ijch P. Stevens, J. Mather, W. Brune. Measurement of tropospheric OH and HO 2 by laser-induced fluorescence at low pressure.
Measurements of hydroxyl (OH) and hydroperoxy (HO 2 *) radical concentrations were made at the Pasadena ground site during the CalNex‐LA campaign using the measurement of hydroxyl radical concentrations in tropospheric air book fluorescence‐fluorescence assay by gas expansion technique.
The measured concentrations of OH and HO 2 * exhibited a distinct weekend effect, with higher radical concentrations observed on the. hydroxyl concentration. Levine et al. () esti- mated that the tropospheric level of the hydroxyl radical may have decreased by about 25% since due to the change in CO and CH.
(iii) Increasing emissions of NO, and HC have given rise to the increase in tropospheric ozone (Isaksen, ; ). The height distribution of. Radiochemical techiques have many untapped applications in atmospheric chemistry, especially when great sensitivity is required.
We describe the application of these techniques to the measurement of hydroxyl radical concentrations in the troposphere. An instrument for the measurement of tropospheric OH radical concentrations by laser-induced fluorescence spectroscopy has been developed.
Ambient air is expanded through a nozzle into a low-pressure fluorescence cell and is irradiated by a frequency-doubled dye laser, which is pulsed with a high repetition rate of kHz. tropospheric hydroxyl radical measurement.
Journal Of Geophysical Research, 95(D11), be used in the measurement of atmospheric hydroxyl radical concentrations. This laser can be tuned by expanding the ambient air flow via a nozzle, followed by. By far the most important radical in the troposphere is the hydroxyl radical, OH.
It is generated photochemically, and reacts with most atmospheric trace gases, in many instances as the first, and rate-determining, step in the reaction chains leading to their oxidation.
The hydroxyl radical, OH, initiates the removal of the majority of trace gases in the atmosphere, and together with the closely coupled species, the hydroperoxy radical, HO 2, is intimately involved in the oxidation chemistry of the critical review discusses field measurements of local concentrations of OH and HO 2 radicals in the troposphere, and in particular the comparisons.
Abstract An instrument for the measurement of tropospheric OH radical concentrations by laser-induced fluorescence spectroscopy has been developed. Ambient air. Abstract. The hydroxyl radical plays a critical role in the chemistry of the lower atmosphere.
Understanding its production, interconversion, and sinks is central to modeling and predicting the chemistry of the troposphere. The OH measurements made during the Tropospheric. Global average hydroxyl radical concentrations have been measured indirectly by analyzing methyl chloroform (CH 3 CCl 3) present in the air.
The results obtained by Montzka et al. ()  shows that the interannual variability in • OH estimated from CH 3 CCl 3 measurements is small, indicating that global • OH is generally well buffered.
An instrument for the measurement of tropospheric OH radical concentrations by laser-induced fluorescence spectroscopy has been developed. Ambient air is expanded through a nozzle into a low-pressure fluorescence cell and is irradiated by a frequency-doubled dye laser, which is pulsed with a high repetition rate of kHz.
The laser wavelength is tunable to selectively excite single. The hydroxyl radical (• OH) is one of the most powerful oxidizing agents, able to react unselectively and instantaneously with the surrounding chemicals, including organic pollutants and • OH radicals are omnipresent in the environment (natural waters, atmosphere, interstellar space, etc.), including biological systems where • OH has an important role in immunity metabolism.
The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now.
Berkeley Electronic Press Selected Works. The hydroxyl radical is the principal oxidizing agent in the troposphere It controls and determines the oxidizing power of the atmosphere and thus governs the atmospheric lifetime of many species and their potential to contribute to climate change air pollution and ozone formation Owing to the development of new measurement techniques and the discovery.
Tropospheric production of OH A major discovery in the early s was that sufficient OH is in fact produced in the troposphere by reactions -to allow for oxidation of species such as CO and CH4 within the troposphere. A calculation of the rate constant for at sea level is shown in Figure as the product of the solar actinic flux, the absorption cross-section for O3, and the O(1D.
1 Trends in global tropospheric hydroxyl radical and methane lifetime since from AerChemMIP David S. Stevenson 1, Alcide Zhao 1, Vaishali Naik 2)LRQD0 2&RQQRU 3, Simone Tilmes 4, Guang Zeng 5, Lee T. Murray 6, William J. Collins 7, Paul Griffiths 8,9, Sungbo S Larry W.
5 Horowitz 2, Lori Sentman 2, Louisa Emmons 4 1School of GeoSciences, The University of Edinburgh, EH9 3FF. Measurement of hydroxyl concentration in boundary layer air by monitoring CO oxidation Campbell, Malcolm J.; Sheppard, John C.; Au, Bernard F.
The local 14CO oxidation rate and the corresponding OH radical concentration in boundary layer air have been measured at several sites.
Measured OH concentrations range from 3× to. Atmospheric OH radical measurements of known quality in terms of precision and accuracy are of paramount importance for the testing of models that are employed in atmospheric research.
The accuracy of instruments used in field campaigns can best be determined in instrument intercomparisons under controlled conditions. The atmosphere simulation chamber SAPHIR in Jülich provides an excellent. Most measurements of hydroxyl radical have been made in relatively clean air environments [Hard et al., b, ; Perner et al., ; Eisele and Tanner, ; Eisele et al., ].
A recent study of tropospheric OH in clean air [Crosley, ], which included three independent OH measurement techniques [Harder.
Diurnal variations in the hydroxyl radical concentration of ambient air were measured for the first time by the technique of laser-induced fluorescence. Science VolIssue The hydroxyl radical (OH) is the main tropospheric oxidant and the main sink for atmospheric methane.
The global abundance of OH has been monitored for the past decades using atmospheric methyl chloroform (CH 3CCl 3) as a proxy. This method is becoming ineffective as atmospheric CH 3CCl 3 concentrations decline.
Here we propose that satellite. HOx radical cycle. OH is highly reactive, with the balance between production and destruction rates giving an atmospheric lifetime under clean conditions of ~1 s (less under polluted conditions), and consequently tropospheric concentrations are extremely low.
Daytime maxima are in the range of () x 10 6 molecule cm-3 ( – pptv). Get this from a library. Development and deployment of instrumentation to measure total hydroxyl radical reactivity in the atmosphere.
[Robert Frederick Hansen; Indiana University, Bloomington. Department of Chemistry.; Indiana University, Bloomington,] -- The hydroxyl radical (OH) is an important atmospheric oxidant that plays a key role in the formation of tropospheric ozone and secondary. In a recent research article in Science, Wennberg et al.
derived the production rate of ozone (O 3) in the middle and upper troposphere from measured concentrations of the hydrogen peroxy radical (HO 2), the hydroxyl radical (OH), and nitrogen oxide (NO).They were able to do so because of the unique and central role OH plays in tropospheric chemistry: OH is the main oxidizing agent in the.
The hydroxyl radical is the principal oxidizing agent in the troposphere It controls and determines the oxidizing power of the atmosphere and thus governs the atmospheric lifetime of many species and their potential to contribute to climate change air pollution and ozone formation Owing to the development of new measurement techniques and the discovery of new reaction mechanisms the.
Page 7 Techniques For Measuring Reactive Nitrogen Oxides, Volatile Organic Compounds, and Oxidants Introduction. A key element in advancing the understanding of tropospheric production of ozone is the ability to make unequivocal measurements of the concentrations of the ozone precursors, the reactive nitrogen oxides (NO y compounds) and volatile organic compounds (VOCs).
Weschler and H. Shields, Environmental Science and Technology, “Production of the Hydroxyl Radical in Indoor Air”, Vol. 30, No. 11,OSHA Ozone Air Contaminants Standard, 29 CFR The three most important oxidising species in the air are: the hydroxyl radical OH the nitrate radical NO the ozone molecule O 3 Hydroperoxy radicals (HO 2) are also important and the sum of HO 2 and OH is sometimes referred to as HO x.
The most important oxidising species is the hydroxyl radical (OH). It is extremely reactive and able to. Atmospheric Free Radical Measurements Related to Photochemical Oxidants in Urban Air EPA Grant Number: R Title: Atmospheric Free Radical Measurements Related to Photochemical Oxidants in Urban Air Investigators: Hard, Thomas M.
Current Investigators: Hard, Thomas M., George, Linda A., O'Brien, Robert J. Institution: Portland State University. Ozone (O 3) is a trace gas of the troposphere, with an average concentration of 20–30 parts per billion by volume (ppbv), with close to ppbv in polluted areas.
Ozone is also an important constituent of the stratosphere, where the ozone layer exists which is located between 10 and 50 kilometers above the earths surface. The troposphere is the lowest layer of the Earth's atmosphere.
Changes in Tropospheric Chemical Composition. Changes in O 3; Changes in HOx; Changes in CH 4 and CO; Changes in H 2 O 2; Changes in O 3 Tropospheric ozone plays an important role in the atmosphere because its photolysis in the presence of water vapor is the primary source for hydroxyl radical (OH), which is responsible for the removal of many important trace gases.
The hydroxyl radical (OH) is the central oxidant of the lower atmosphere. OH is highly variable in space and time, but current observation-based methods cannot resolve local and regional OH gradients.
We combine the robust chemical relationship between OH and formaldehyde (HCHO) (a ubiquitous hydrocarbon oxidation product) with satellite-based HCHO observations to infer total. Source of hydroxyl radical burst. The hydroxyl radical burst is not explained by known pathways to OH formation in cloud drops [processes (i) to (vii) above], as their kinetics are all about one to three orders of magnitude too slow.
In laboratory air, OH and H 2 O 2 are low. source of tropospheric ozone. 1,2) During the day time, isoprene reacts predominantly with the hydroxyl radical (OH) which has tropospheric lifetime of a few seconds or less and the concentration of OH in the sunlit troposphere is near 10 6 moleculescm 3.
3) In the metropolitan city, the atmosphere is polluted by automobile exhaust gases.Liu SC and Trainer M () Responses of tropospheric ozone and odd hydrogen radicals to column ozone changes.
J Atmos Chem Levy II, H () Normal atmosphere: large radical and formaldehyde concentrations predicted. Science Logan JA, Prather MJ, Wofsy SC, and McElroy MB () Tropospheric chemistry: a global perspective.Hydroxyl Radicals, Atmospheric Lifetimes, and Ozone Formation Even at relatively low tropospheric mixing ratios (ppbv to pptv levels, Table 1), the high reactivity of VOCs allows them to play a significant role in atmospheric chemistry.
The main sink of most VOCs is through photooxidation, initiated typically by reaction with hydroxyl (OH.