scholarly journals Photochemical decomposition of hydrogen peroxide (H2O2) and formaldehyde (HCHO) in artificial snow

2004 ◽  
Vol 39 ◽  
pp. 29-33 ◽  
Author(s):  
Hans-Werner Jacobi ◽  
Bright Kwakye-Awuah ◽  
Otto Schrems
Keyword(s):  
Hydrogen Peroxide ◽  
Ice Cores ◽  
Photochemical Activity ◽  
Photochemical Reactions ◽  
Visible Range ◽  
Surface Snow ◽  
Photochemical Decomposition ◽  
Reactive Radicals ◽  
Natural Snow ◽  
Atmospheric Concentrations

AbstractLaboratory-made snow doped with either hydrogen peroxide (H2O2) or formaldehyde (HCHO) was exposed to radiation in the ultraviolet and visible range, resulting in a decomposition of both compounds. These experiments demonstrate that, besides the photolysis of nitrate, further photochemical reactions of atmospheric relevant compounds can take place in snow. Under similar conditions the decomposition of H2O2 is more efficient than that of HCHO. Since the decompositions in the experiments follow first-order reaction kinetics, we suggest that the same products as in photolysis reactions in the liquid phase are produced. If similar reactions also take place in natural snow covers, these reactions would have several important consequences. The reactions could represent pathways for the generation of highly reactive radicals in the condensed phase, enhancing the photochemical activity of surface snow and modifying the oxidation capacity of the atmospheric boundary layer. The photolysis could also constitute an additional sink for H2O2 and HCHO in surface snow, which should be taken into account for the reconstruction of atmospheric concentrations of both compounds from concentration profiles in surface snow and ice cores.

scholarly journals Possible Causes of the Variation in Microparticle Concentration in an Ice Core from Mizuho Station, Antarctica

1982 ◽  
Vol 3 ◽  
pp. 107-112 ◽  
Author(s):  
Yoshiyuki Fujii ◽  
Tetsuo Ohata
Keyword(s):  
Annual Cycle ◽  
Arid Regions ◽  
Annual Variation ◽  
Ice Core ◽  
Ice Cores ◽  
Layer Formation ◽  
Snow Layer ◽  
Discontinuous Surface ◽  
Surface Snow ◽  
Surface Layer Formation

Variation of the microparticle concentration in an ice core from Mizuho station, East Antarctica, does not show the annual cycle that has been demonstrated for ice cores from Antarctica and Greenland by other authors. Possible reasons for the lack of a annual cycle are considered and two causes are suggested. (1) Semi-annual variation of microparticle concentration as observed in drift-snow. The low particle concentration in March and in August to October is not due to minor particle transport, but to the dilution of microparticles transported mainly from arid regions in the southern hemisphere through the troposphere by falling snow. (2) Discontinuous surface-layer formation. A seasonal or an annual sequence of the variation in microparticle concentration in surface snow layers may be interrupted by the absence of surface snow-layer formation.

scholarly journals Photochemical reactions in the fluorite region II─Photochemical decomposition of formaldehyde vapour

1937 ◽  
Vol 163 (913) ◽  
pp. 221-227 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Absorption Spectrum ◽  
Ground State ◽  
Wave Length ◽  
Ultra Violet ◽  
Photochemical Reactions ◽  
Photochemical Decomposition ◽  
The Subject ◽  
Region Ii ◽  
Formaldehyde Vapour

The photochemical decomposition of formaldehyde in the near ultra­-violet has been the subject of several investigations. It is known (Norrish and Kirkbride 1932) that the products are chiefly carbon monoxide and hydrogen, and that neither the composition of the products nor the quantum yield depends appreciably on wave-length. Recently Price (1935) has investigated the far ultra-violet absorption spectrum of formaldehyde. The first band observed in this region occurs at about 1745 A and is very diffuse, whereas the first bands in acetaldehyde (Price 1935) and acetone (Noyes, Duncan and Manning 1934) occur at longer wave-lengths and are relatively much sharper. Price ascribes this diffuseness to a predissociation resulting from the interaction of the upper state in formaldehyde with the ground state and assumes that the primary dissociation at about 1745 A should be CH 2 O → hv 1745 A CH 2 + O.

scholarly journals The Photochemical Decomposition of Hydrogen Peroxide I

1914 ◽  
Vol 18 (2) ◽  
pp. 166-178 ◽  
Author(s):  
J. Howard Mathews ◽  
Harry A. Curtis
Keyword(s):  
Hydrogen Peroxide ◽  
Photochemical Decomposition

Spatial variability of surface snow isotopic composition on the East Antarctic Plateau and implications for climate reconstructions

2020 ◽  
Author(s):  
Maria Hörhold ◽  
Alexander Weinhart ◽  
Sepp Kipfstuhl ◽  
Johannes Freitag ◽  
Georgia Micha ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ice Core ◽  
Empirical Relationship ◽  
Ice Cores ◽  
Stable Water Isotopes ◽  
Antarctic Plateau ◽  
Mean Temperature ◽  
Spatial Coverage ◽  
Surface Snow ◽  
Relationship Of

<p>The reconstruction of past temperatures based on ice core records relies on the quantitative but empirical relationship of stable water isotopes and annual mean temperature. However, its relation varies through space and time. On the East Antarctic Plateau, temperature reconstructions from ice cores are poorly constrained or even fail on decadal and smaller time scales. The observed discrepancy between annual mean temperature and isotopic composition partly relies on surface processes altering the signal after deposition but also, to a great deal, on spatially coherent processes prior to or during deposition. However, spatial coverage over larger areas on the East Antarctic Plateau is challenging. We here present in-situ measurements of the isotopic composition of surface snow with unprecedented statistical quality and coverage. 1m surface snow profiles were collected during an overland traverse between Kohnen station and Plateau Station, covering a 1200km long transect. We explore regional differences of the temperature-isotope relationship and discuss possible mechanisms affecting the isotopic composition in areas with accumulation rates lower than 60mmWEa^-1.</p>

Pulse Рhotochemical Decomposition of Phenol in Wastewater

2020 ◽  
Vol 24 (2) ◽  
pp. 22-27
Author(s):  
A.M. Gonopol'sky ◽  
S.G. Shashkovskiy ◽  
Y.A. Goldstein ◽  
S.G. Kireev ◽  
A.D. Volosatova ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Good Accuracy ◽  
Radiation Power ◽  
Decomposition Rate Constant ◽  
Initial Concentration ◽  
Destruction Rate ◽  
Wide Wavelength Range ◽  
Photochemical Decomposition ◽  
Phenol Decomposition ◽  
Average Radiation Power

Photochemical decomposition of phenol with a concentration of 5 to 24 mg/L using hydrogen peroxide and ultraviolet irradiation (UV/H2O2) was studied. Xenon flash lamp was chosen as a radiation source. It emits high-intensity continuous-spectrum radiation in a wide wavelength range from 200 to 1000 nm. The effect of the initial concentration of hydrogen peroxide and the source average radiation power on the phenol destruction rate were studied. An extremum in the dependence of the phenol decomposition rate constant on the initial concentration of hydrogen peroxide was found. Kinetic model of the process based on the obtained data was developed. It was tested by predicting phenol destruction rate with the different process parameters and gave good accuracy.

scholarly journals Laser-Induced Photochemical Reaction of Maleic Acid Solutions in the Presence of Hydrogen Peroxide

1997 ◽  
Vol 17 (2) ◽  
pp. 97-108 ◽  
Author(s):  
Yuichi Shimizu ◽  
Shun'ichi Sugimoto ◽  
Shunichi Kawanishi ◽  
Nobutake Suzuki
Keyword(s):  
Hydrogen Peroxide ◽  
Maleic Acid ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Direct Synthesis ◽  
Reaction Scheme ◽  
Photochemical Reactions ◽  
The Other ◽  
Acid Solutions ◽  
Selective Formation

Targeting the selective and direct synthesis of tartaric acid (TA), the photochemical reactions of maleic acid (MA) solutions containing H2O2. in various solvents have been investigated using four wavelengths in the UV region between 193 and 351 nm, with high intensity from an excimer laser. All the laser irradiations in H2O resulted in the direct synthesis of TA with lower selectivity and it was found that, with XeF-laser (351 nm) irradiation in 1,4-dioxane, TA is selectively and directly synthesized from MA containing H2O2 of lower concentration at room temperature. On the other hand, none of the irradiations in methanol, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran gave the selective formation of TA. On the basis of these results, the reaction scheme for the selective formation of TA is discussed.

scholarly journals Air–snow transfer of nitrate on the East Antarctic Plateau – Part 2: An isotopic model for the interpretation of deep ice-core records

2015 ◽  
Vol 15 (20) ◽  
pp. 12079-12113 ◽  
Author(s):  
J. Erbland ◽  
J. Savarino ◽  
S. Morin ◽  
J. L. France ◽  
M. M. Frey ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Ice Core ◽  
Ice Cores ◽  
Reactive Nitrogen ◽  
Antarctic Plateau ◽  
Surface Snow ◽  
Rate Building ◽  
The Antarctic ◽  
The Impact ◽  
Ice Core Records

Abstract. Unraveling the modern budget of reactive nitrogen on the Antarctic Plateau is critical for the interpretation of ice-core records of nitrate. This requires accounting for nitrate recycling processes occurring in near-surface snow and the overlying atmospheric boundary layer. Not only concentration measurements but also isotopic ratios of nitrogen and oxygen in nitrate provide constraints on the processes at play. However, due to the large number of intertwined chemical and physical phenomena involved, numerical modeling is required to test hypotheses in a quantitative manner. Here we introduce the model TRANSITS (TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow), a novel conceptual, multi-layer and one-dimensional model representing the impact of processes operating on nitrate at the air–snow interface on the East Antarctic Plateau, in terms of concentrations (mass fraction) and nitrogen (δ15N) and oxygen isotopic composition (17O excess, Δ17O) in nitrate. At the air–snow interface at Dome C (DC; 75° 06' S, 123° 19' E), the model reproduces well the values of δ15N in atmospheric and surface snow (skin layer) nitrate as well as in the δ15N profile in DC snow, including the observed extraordinary high positive values (around +300 ‰) below 2 cm. The model also captures the observed variability in nitrate mass fraction in the snow. While oxygen data are qualitatively reproduced at the air–snow interface at DC and in East Antarctica, the simulated Δ17O values underestimate the observed Δ17O values by several per mill. This is explained by the simplifications made in the description of the atmospheric cycling and oxidation of NO2 as well as by our lack of understanding of the NOx chemistry at Dome C. The model reproduces well the sensitivity of δ15N, Δ17O and the apparent fractionation constants (15ϵapp, 17Eapp) to the snow accumulation rate. Building on this development, we propose a framework for the interpretation of nitrate records measured from ice cores. Measurement of nitrate mass fractions and δ15N in the nitrate archived in an ice core may be used to derive information about past variations in the total ozone column and/or the primary inputs of nitrate above Antarctica as well as in nitrate trapping efficiency (defined as the ratio between the archived nitrate flux and the primary nitrate input flux). The Δ17O of nitrate could then be corrected from the impact of cage recombination effects associated with the photolysis of nitrate in snow. Past changes in the relative contributions of the Δ17O in the primary inputs of nitrate and the Δ17O in the locally cycled NO2 and that inherited from the additional O atom in the oxidation of NO2 could then be determined. Therefore, information about the past variations in the local and long-range processes operating on reactive nitrogen species could be obtained from ice cores collected in low-accumulation regions such as the Antarctic Plateau.

scholarly journals Methane variations on orbital timescales: a transient modeling experiment

2011 ◽  
Vol 7 (1) ◽  
pp. 47-77
Author(s):  
T. Y. M. Konijnendijk ◽  
S. L. Weber ◽  
E. Tuenter ◽  
M. van Weele
Keyword(s):  
Climate Model ◽  
Climate Modeling ◽  
Ice Cores ◽  
Vegetation Coverage ◽  
Ch4 Emissions ◽  
Monsoon Area ◽  
Two Factors ◽  
Modeling Experiment ◽  
Global Vegetation ◽  
Atmospheric Concentrations

Abstract. Methane (CH4) variations on orbital timescales are often associated with variations in wetland coverage, most notably in the summer monsoon areas of the Northern Hemisphere. Here we test this assumption by simulating orbitally forced variations in global wetland emissions, using a simple wetland distribution and CH4 emissions model that was coupled off-line to a climate model containing atmosphere, ocean and vegetation components. The transient climate modeling simulation extends over the last 650 000 yrs and includes variations in land-ice distribution and greenhouse gases. Tropical temperature and global vegetation are found to be the dominant controls for global CH4 emissions and thus atmospheric concentrations. The relative importance of wetland coverage, vegetation coverage, and emission temperatures depends on the specific climatic zone (boreal, tropics and Indian/Asian monsoon area) and timescale (precession, obliquity and glacial-interglacial timescales). Simulated variations in emissions agree well with those in measured concentrations, both in their time series and spectra. The simulated lags with respect to the orbital forcing also show close agreement with those found in measured data, both on the precession and obliquity timescale. We only find covariance between monsoon precipitation and CH4 concentrations, however we find causal links between atmospheric concentrations and tropical temperatures and global vegetation. The primary importance of these two factors explains the lags found in the CH4 record from ice cores.

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