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  • 1
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    HOx budgets during HOxComp: A case study of HOx chemistry under NOx-limited conditions (2012)
    Wiley
    Details
    Publication Date: 2012-02-10
    Description: Recent studies have shown that measured OH under NOx-limited, high-isoprene conditions are many times higher than modeled OH. In this study, a detailed analysis of the HOx radical budgets under low-NOx, rural conditions was performed employing a box model based on the Master Chemical Mechanism (MCMv3.2). The model results were compared with HOx radical measurements performed during the international HOxComp campaign carried out in Jülich, Germany, during summer 2005. Two different air masses influenced the measurement site denoted as high-NOx (NO, 1–3 ppbv) and low-NOx (NO, 〈 1 ppbv) periods. Both modeled OH and HO2 diurnal profiles lay within the measurement range of all HOx measurement techniques, with correlation slopes between measured and modeled OH and HO2 around unity. Recently discovered interference in HO2 measurements caused by RO2 cross sensitivity was found to cause a 30% increase in measured HO2 during daytime on average. After correction of the measured HO2 data, the model HO2 is still in good agreement with the observations at high NOx but overpredicts HO2 by a factor of 1.3 to 1.8 at low NOx. In addition, for two different set of measurements, a missing OH source of 3.6 ± 1.6 and 4.9 ± 2.2 ppb h−1 was estimated from the experimental OH budget during the low-NOx period using the corrected HO2 data. The measured diurnal profile of the HO2/OH ratio, calculated using the corrected HO2, is well reproduced by the MCM at high NOx but is significantly overestimated at low NOx. Thus, the cycling between OH and HO2 is better described by the model at high NOx than at low NOx. Therefore, similar comprehensive field measurements accompanied by model studies are urgently needed to investigate HOx recycling under low-NOx conditions.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation (2013)
    Springer Nature
    Details
    Publication Date: 2013-11-29
    Description: Nature Geoscience 6, 1023 (2013). doi:10.1038/ngeo1964 Authors: H. Fuchs, A. Hofzumahaus, F. Rohrer, B. Bohn, T. Brauers, H-P. Dorn, R. Häseler, F. Holland, M. Kaminski, X. Li, K. Lu, S. Nehr, R. Tillmann, R. Wegener & A. Wahner Most pollutants in the Earth’s atmosphere are removed by oxidation with highly reactive hydroxyl radicals. Field measurements have revealed much higher concentrations of hydroxyl radicals than expected in regions with high loads of the biogenic volatile organic compound isoprene. Different isoprene degradation mechanisms have been proposed to explain the high levels of hydroxyl radicals observed. Whether one or more of these mechanisms actually operates in the natural environment, and the potential impact on climate and air quality, has remained uncertain. Here, we present a complete set of measurements of hydroxyl and peroxy radicals collected during isoprene-oxidation experiments carried out in an atmospheric simulation chamber, under controlled atmospheric conditions. We detected significantly higher concentrations of hydroxyl radicals than expected based on model calculations, providing direct evidence for a strong hydroxyl radical enhancement due to the additional recycling of radicals in the presence of isoprene. Specifically, our findings are consistent with the unimolecular reactions of isoprene-derived peroxy radicals postulated by quantum chemical calculations. Our experiments suggest that more than half of the hydroxyl radicals consumed in isoprene-rich regions, such as forests, are recycled by these unimolecular reactions with isoprene. Although such recycling is not sufficient to explain the high concentrations of hydroxyl radicals observed in the field, we conclude that it contributes significantly to the oxidizing capacity of the atmosphere in isoprene-rich regions.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 3
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    Formation of molecular chlorine from the photolysis of ozone and aqueous sea-salt particles (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-01-09
    Description: Halogen atoms from the reactions of sea-salt particles may play a significant role in the marine boundary layer. Reactions of sodium chloride, the major component of sea-salt particles, with nitrogen oxides generate chlorine atom precursors. However, recent studies suggest there is an additional source of chlorine in the marine troposphere. This study shows that molecular chlorine is generated from the photolysis of ozone in the presence of sea-salt particles above their deliquescence point; this process may also occur in the ocean surface layer. Given the global distribution of ozone, this process may provide a global source of chlorine.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Oum -- Lakin -- DeHaan -- Brauers -- Finlayson-Pitts -- New York, N.Y. -- Science. 1998 Jan 2;279(5347):74-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Irvine, CA 92697-2025 USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9417027" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Amplified trace gas removal in the troposphere (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-06-06
    Description: The degradation of trace gases and pollutants in the troposphere is dominated by their reaction with hydroxyl radicals (OH). The importance of OH rests on its high reactivity, its ubiquitous photochemical production in the sunlit atmosphere, and most importantly on its regeneration in the oxidation chain of the trace gases. In the current understanding, the recycling of OH proceeds through HO2 reacting with NO, thereby forming ozone. A recent field campaign in the Pearl River Delta, China, quantified tropospheric OH and HO2 concentrations and turnover rates by direct measurements. We report that concentrations of OH were three to five times greater than expected, and we propose the existence of a pathway for the regeneration of OH independent of NO, which amplifies the degradation of pollutants without producing ozone.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hofzumahaus, Andreas -- Rohrer, Franz -- Lu, Keding -- Bohn, Birger -- Brauers, Theo -- Chang, Chih-Chung -- Fuchs, Hendrik -- Holland, Frank -- Kita, Kazuyuki -- Kondo, Yutaka -- Li, Xin -- Lou, Shengrong -- Shao, Min -- Zeng, Limin -- Wahner, Andreas -- Zhang, Yuanhang -- New York, N.Y. -- Science. 2009 Jun 26;324(5935):1702-4. doi: 10.1126/science.1164566. Epub 2009 Jun 4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Forschungszentrum Julich, Institut fur Chemie und Dynamik der Geosphare-2: Troposphare, 52425 Julich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19498111" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-04-20
    Description: Gaseous nitrous acid (HONO) is an important precursor of tropospheric hydroxyl radicals (OH). OH is responsible for atmospheric self-cleansing and controls the concentrations of greenhouse gases like methane and ozone. Due to lack of measurements, vertical distributions of HONO and its sources in the troposphere remain unclear. Here, we present a set of observations of HONO and its budget made onboard a Zeppelin airship. In a sunlit layer separated from Earth's surface processes by temperature inversion, we found high HONO concentrations providing evidence for a strong gas-phase source of HONO consuming nitrogen oxides and potentially hydrogen oxide radicals. The observed properties of this production process suggest that the generally assumed impact of HONO on the abundance of OH in the troposphere is substantially overestimated.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Xin -- Rohrer, Franz -- Hofzumahaus, Andreas -- Brauers, Theo -- Haseler, Rolf -- Bohn, Birger -- Broch, Sebastian -- Fuchs, Hendrik -- Gomm, Sebastian -- Holland, Frank -- Jager, Julia -- Kaiser, Jennifer -- Keutsch, Frank N -- Lohse, Insa -- Lu, Keding -- Tillmann, Ralf -- Wegener, Robert -- Wolfe, Glenn M -- Mentel, Thomas F -- Kiendler-Scharr, Astrid -- Wahner, Andreas -- New York, N.Y. -- Science. 2014 Apr 18;344(6181):292-6. doi: 10.1126/science.1248999.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Energie-und Klimaforschung: Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24744373" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    ATMOSPHERIC SCIENCE. Response to Comment on "Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere" (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-06-20
    Description: Ye et al. have determined a maximum nitrous acid (HONO) yield of 3% for the reaction HO2.H2O + NO2, which is much lower than the yield used in our work. This finding, however, does not affect our main result that HONO in the investigated Po Valley region is mainly from a gas-phase source that consumes nitrogen oxides.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Xin -- Rohrer, Franz -- Hofzumahaus, Andreas -- Brauers, Theo -- Haseler, Rolf -- Bohn, Birger -- Broch, Sebastian -- Fuchs, Hendrik -- Gomm, Sebastian -- Holland, Frank -- Jager, Julia -- Kaiser, Jennifer -- Keutsch, Frank N -- Lohse, Insa -- Lu, Keding -- Tillmann, Ralf -- Wegener, Robert -- Wolfe, Glenn M -- Mentel, Thomas F -- Kiendler-Scharr, Astrid -- Wahner, Andreas -- New York, N.Y. -- Science. 2015 Jun 19;348(6241):1326. doi: 10.1126/science.aaa3777.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Energie und Klimaforschung, Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany. f.rohrer@fz-juelich.de x.li@fz-juelich.de. ; Institut fur Energie und Klimaforschung, Troposphare (IEK-8), Forschungszentrum Julich, Julich, Germany. ; Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26089508" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Electronic Resource
    Electronic Resource
    Latitudinal variation of measured NO2 photolysis frequencies over the Atlantic Ocean between 50° N and 30° S (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 269-282 
    Details
    ISSN: 1573-0662
    Keywords: Photolysis frequency ; J(NO2) ; global radiation ; aerosol ; meridional cross section ; marine atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Using a filter radiometer, the meridional profile of the NO2 photolysis frequency, J(NO2), was measured between 50° N and 30° S during the cruise ANTVII/1 September/October 1988 of the research vessel Polarstern on the Atlantic Ocean. Simultaneously, global broadband irradiance and acrosol were monitored. Clean marine background air with low aerosol loads (b sp=(1–2)×10-5 m-1) was encountered at the latitudes 25° N–30° N and 18° S–27° S, respectively. Under these conditions and an almost cloudless sky J(NO2) reached 7.3×10-3 s-1 (2π sr) for a zenith angle of 30°. Between 30° N and 30° S, the latitudinal variation of the J(NO2) noontime maxima was less than ± 10%, while the mean value at noon was 7.8×10-3 s-1. For the set of all data between 50° N and 30° S, a nearly linear correlation of J(NO2) vs. global broadland irradiance was found. The slope of (8.24±0.03)×10-5 s-1/mW cm-2 agrees within 10% with observations in Jülich (51° N, 6.2° E).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115398
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  • 8
    Electronic Resource
    Electronic Resource
    Atmospheric measurements during Polarstern cruise ANT VII/1, 54° N to 32° S: An overview (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 203-214 
    Details
    ISSN: 1573-0662
    Keywords: Maritime troposphere ; trace gas measurements ; oxidant formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A comprehensive set of trace gas concentrations and meteorological parameters were measured simultaneously during a cruise of the research vessel Polarstern from Bremerhaven (54° N, 8° E) to Rio Grande (32° S, 52° W) during the period from 15 September to 9 October 1988. This paper describes the general features of the cruise and summarizes the measurements made, the techniques employed, and the placement of the instruments on board the ship. The synoptic data base is used to characterize the nature and possible origins of the air masses encountered during the cruise and to draw some general conclusions from the measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115394
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  • 9
    Electronic Resource
    Electronic Resource
    Intercomparison of Tropospheric OH Measurements by Different Laser Techniques during the POPCORN Campaign 1994 (1998)
    Springer
    Journal of atmospheric chemistry 31 (1998), S. 227-246 
    Details
    ISSN: 1573-0662
    Keywords: OH intercomparison ; laser absorption spectroscopy ; DOAS ; laser induced fluorescence ; LIF ; troposphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In-situ OH measurements by laser-induced fluorescence (LIF) spectroscopy and folded long-path differential optical absorption spectroscopy (DOAS) were carried out in a rural environment in North-East Germany as part of the field experiment POPCORN in August 1994. The large set of OH data obtained allowed an intercomparison of both techniques based on relative diurnal profiles and simultaneously measured absolute concentrations. Most of the time the two OH instruments encountered the same air and agreed well in the measured relative diurnal variations. Only on a few occasions the measurements significantly disagreed due to a perturbation of the DOAS measurements by a local OH source in the north-western wind sector. Excluding data from this wind direction, the statistical analysis of 137 data pairs yields a correlation coefficient of r = 0.90 and a weighted linear fit with a slope of 1.09 ± 0.12. The correlations are carefully analyzed. The comparison of both instruments is discussed in the light of newly published effective absorption cross-sections for H2O and O2 that affect the calibration of LIF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006014707617
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  • 10
    Electronic Resource
    Electronic Resource
    Latitudinal variation of measured O3 photolysis frequencies J(O1D) and primary OH production rates over the Atlantic Ocean between 50° N and 30° S (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 283-298 
    Details
    ISSN: 1573-0662
    Keywords: Photolysis frequency ; J(O1D), O3, H2O ; OH production rate ; meridional cross-section ; marine atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The latitudinal variation of the photolysis frequency of ozone to O(1D) atoms, J(O1D), was measured using a filter radiometer during the cruise ANT VII/1 of the research vessel Polarstern in September/October 1988. The J(O1D) noon values exhibited a maximum of 3.6×10-5 s-1 (2π sr) at the equator and decreased strongly towards higher latitudes. J(O1D) reached highest values for clean marine background air with low aerosol load and almost cloudless sky. The J(O1D) data, measured under these conditions and a temperature of 295 K, can be expressed by: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOsaiaacI% cacaqGpbWaaWbaaSqabeaaiiaacqWF8baFaaGccaqGebGaaeykaiaa% bccacqWF9aqpcaqGGaGaaeyzaiaabIhacaqGWbGaaeiiaiaabUhacq% GHsislcaaI4aGaaiOlaiaaicdacaaIYaGaeyOeI0IaaGioaiaac6ca% caaI4aGaaiiEaiaaigdacaaIWaWaaWbaaSqabeaacqGHsislcaaIZa% aaaOGaaeiiaiaabIhacaqGGaGaam4uaiabgUcaRiaaiodacaGGUaGa% aGinaiaacIhacaaIXaGaaGimamaaCaaaleqabaGaeyOeI0IaaGOnaa% aakiaadofadaahaaWcbeqaaiaaikdaaaGccaGG9bGaaeikaiaaboha% daahaaWcbeqaaiabgkHiTiaaigdaaaGccaGGPaaaaa!5EE9!\[J({\text{O}}^| {\text{D) }} = {\text{ exp \{ }} - 8.02 - 8.8x10^{ - 3} {\text{ x }}S + 3.4x10^{ - 6} S^2 \} {\text{(s}}^{ - 1} )\] where S represents the product of the overhead ozone column (DU) and the secant of the solar zenith angle. The meridional profile of the primary OH radical production rate P(OH) was calculated from the J(O1D) measurements and simultaneously recorded O3 and H2O mixing ratios. While the latitudinal distribution of J(O1D) and water vapour was nearly symmetric to the equator, high tropospheric ozone levels up to 40 ppb were observed in the Southern Hemisphere, SH, resulting in higher P(OH) in the SH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115399
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