Relative tropospheric photolysis rates of HCHO, H13CHO, HCH18O, and DCDO measured at the European photoreactor facility.
Department of Chemistry, University of Copenhagen, Universitetsparken 5 DK-2100 Copenhagen OE, Denmark.
The relative photolysis rates of HCHO, H13CHO, HCH18O, and DCDO were studied in pseudo-natural tropospheric conditions in July 2003 at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. The photolytic decay of HCHO, H13CHO, and HCH18O is measured relative to DCDO by long path FT-IR detection during the course of about 3 h of sunlight. The relative photolysis rates obtained are as follows: JH13CHO/JHCHO = 0.894 +/- 0.006, JHCH18O/JHCHO = 0.911 +/- 0.011, and JDCDO/JHCHO = 0.597 +/- 0.001. The errors represent 1sigma and do not include possible systematic errors. The atmospheric implications of the large isotope effects in the photolysis of formaldehyde are discussed.
Laurence Y Yeung, Hagit P Affek, Katherine J Hoag, Weifu Guo, Aaron A Wiegel, Elliot L Atlas, Sue M Schauffler, Mitchio Okumura, Kristie A Boering, John M Eiler
Divisions of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA. firstname.lastname@example.org
The stratospheric CO(2) oxygen isotope budget is thought to be governed primarily by the O((1)D)+CO(2) isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO(2) isotopologue (16)O(13)C(18)O, in concert with (18)O and (17)O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric (16)O(13)C(18)O, observed as proportions in the polar vortex that are higher than in any naturally derived CO(2) sample to date. We show, through photochemical experiments, that lower (16)O(13)C(18)O proportions observed in the midlatitudes are determined primarily by the O((1)D)+CO(2) isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher (16)O(13)C(18)O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O((1)D)+CO(2). We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO(2) or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric (16)O(13)C(18)O enrichments may impose additional isotopic constraints on biosphere-atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.
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Relative Tropospheric Photolysis Rates of HCHO, H(13)CHO, HCH(18)O, and DCDO Measured at the European Photoreactor Facility.
Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen OE, Denmark.
A relative rate experiment is carried out for four isotopomers of carbon monoxide (CO) and their reactions with OH and OD radicals. The relative reaction rates of 13C16O, 12Cl8O, 12C17O and 13C18O with OH and OD radicals are measured at 298 +/- 2 K and 1013 +/- 10 mbar. The OH/OD source in the reaction chamber is photolysis of ozone to produce O(1D) in the presence of molecular hydrogen: O(1D)+ H2/D2 --> OH/OD + H/D. The relative reaction rates are determined as: k(OH)+ 13C16O/k(OH)+ 12C18O = 0.98 +/- 0.01, k(OH)+ 12C17O/k(OH)+ 12C18O = 0.990 +/- 0.008, k(OH)+ 13C16O/k(OH)+ 13C18O = 0.98 +/- 0.01, k(OD)+ 13C16O/k(OD)+ 12C18O = 0.99 +/- 0.01, k(OD)+ 12C17O/ k(OD)+ 12C18O = 1.000 +/- 0.008, k(OD)+ 13C16O/k(OD)+ 13C18O = 0.98 +/- 0.01. The errors represent 2sigma from the statistical analyses and do not include possible systematic errors. These are novel results for the kinetic isotope effects in the reactions of CO isotopomers with OD radicals. The results for the reactions of CO isotopomers with OH radicals constitute a repeat and a re-analysis of experimental data previously published by this group which have been found to be partly erroneous. This communication serves as a correction to the following paper: K. L. Feilberg, S. R. SellevÃ¥g, C. J. Nielsen, D. W. T. Griffith and M. S. Johnson, Phys. Chem. Chem. Phys., 2002, 4, 4687.
Relative tropospheric photolysis rates of acetaldehyde and formaldehyde isotopologues measured at the European photoreactor facility.
Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5 DK-2100 Copenhagen OE, Denmark.
The photolysis rates of HCHO, DCDO, CH(3)CHO, and CH(3)CDO are studied by long-path FTIR spectroscopy in natural tropospheric conditions at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. Average relative photolysis rates j(HCHO)/j(DCDO)= 3.15 +/- 0.08 and j(CH(3)CHO)/j(CH(3)CDO)= 1.26 +/- 0.03 are obtained from three days of experiments for each reaction in the period June 17 to July 7, 2006.
Copenhagen Center for Atmospheric Research, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark. email@example.com
The kinetic isotope effects in the reactions of CHCl(3), CDCl(3), and (13)CHCl(3) with Cl, OH, and OD radicals have been determined in relative rate experiments at 298 +/- 1 K and atmospheric pressure monitored by long path FTIR spectroscopy. The spectra were analyzed using a nonlinear least-squares spectral fitting procedure including line data from the HITRAN database and measured infrared spectra as references. The following relative reaction rates were determined: k(CHCl(3)+Cl)/k(CDCl(3)+Cl)= 3.28 +/- 0.01, k(CHCl(3)+Cl)/k((13)CHCl(3)+Cl)= 1.000 +/- 0.003, k(CHCl(3)+OH)/k(CDCl(3)+OH)= 3.73 +/- 0.02, k(CHCl(3)+OH)/k((13)CHCl(3)+OH)= 1.023 +/- 0.002, k(CHCl(3)+OD)/k(CDCl(3)+OD)= 3.95 +/- 0.03, and k(CHCl(3)+OD)/k((13)CHCl(3)+OD)= 1.032 +/- 0.004. Larger isotope effects in the OH reactions than in the Cl reactions are opposite to the trends for CH(4) and CH(3)Cl reported in the literature. The origin of these differences was investigated using electronic structure calculations performed at the MP2/aug-cc-PVXZ (X = D, T, Q) level of theory and are compared with previously calculated values for the other methane derivatives. The Born-Oppenheimer barrier heights to H abstraction are 12.2 and 17.0 kJ mol(-1) at the CCSD(T)/aug-cc-pVTZ level of theory for OH and Cl, respectively. The reaction rate coefficients of the two elementary vapor phase reactions including the (2)H and (13)C kinetic isotope effects were calculated using improved canonical variational theory with small curvature tunneling (ICVT/SCT) and the results compared with experimental data.
Barbara D'Anna, Armin Wisthaler, Ã˜yvind Andreasen, Armin Hansel, Jens Hjorth, Niels R Jensen, Claus J Nielsen, Yngve StenstrÃ¸m, Jyrki Viidanoja
Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway. firstname.lastname@example.org
The rate coefficients for the gas phase reaction of NO3 and OH radicals with a series of cycloalkanecarbaldehydes have been measured in purified air at 298 +/- 2 K and 760 +/- 10 Torr by the relative rate method using a static reactor equipped with long-path Fourier transform infrared (FT-IR) detection. The values obtained for the OH radical reactions (in units of 10(-11) cm3 molecule(-1) s(-1)) were the following: cyclopropanecarbaldehyde, 2.13 +/- 0.05; cyclobutanecarbaldehyde, 2.66 +/- 0.06; cyclopentanecarbaldehyde, 3.27 +/- 0.07; cyclohexanecarbaldehyde, 3.75 +/- 0.05. The values obtained for the NO3 radical reactions (in units of 10(-14) cm3 molecule(-1) s(-1)) were the following: cyclopropanecarbaldehyde, 0.61 +/- 0.04; cyclobutanecarbaldehyde, 1.99 +/- 0.06; cyclopentanecarbaldehyde, 2.55 +/- 0.10; cyclohexanecarbaldehyde, 3.19 +/- 0.12. Furthermore, the reaction products with OH radicals have been investigated using long-path FT-IR spectroscopy and proton-transfer-reaction mass spectrometry (PTR-MS). The measured carbon balances were in the range 89-97%, and the identified products cover a wide spectrum of compounds including nitroperoxycarbonyl cycloalkanes, cycloketones, cycloalkyl nitrates, multifunctional compounds containing carbonyl, hydroxy, and nitrooxy functional groups, HCOOH, HCHO, CO, and CO2.
Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, Norway.
The UV-vis and infrared absorption cross sections of perfluoro-2-methyl-3-pentanone (CF3CF2C(O)CF(CF3)2, 1,1,1,2,2,4,5,5,5-nonafluoro-4-(trifluoromethyl)-3-penta none), has been obtained, and a photolysis study was carried out under natural sunlight conditions in the European simulation chamber, Valencia, Spain (EUPHORE). The photolysis loss rate, J(photol), equaled (6.4 +/- 0.3) x 10(-6) s(-1) in the period of 10-14 GMT, July 14, 2003 in Valencia (0.5 W, 39.5 N) and corresponded to an effective quantum yield of photolysis of 0.043 +/- 0.011 over the wavelength range of 290-400 nm; the error limits correspond to 2sigma from the statistical analyses. The atmospheric lifetime of CF3CF2C(O)CF(CF3)2 is estimated to be around 1 week, and the global warming potential of the compound is negligible.
Appl Opt. 2004 Apr 20;43 (12):2500-9 15119620
Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0372 Oslo, Norway.
The complex index of refraction of aqueous methanesulfonic acid (MSA) at room temperature and at concentrations of 1-70 wt.% is presented. The complex index of refraction is obtained in the entire wave-number region from the mid infrared to the ultraviolet-visible regions. An analysis of the infrared spectra reveals a single absorption band, which makes it possible to identify MSA in aqueous H2SO4. The surface tension of 1-99-wt.% aqueous MSA from room temperature to approximately 263 K, depending on the concentration of MSA, is reported. A polynomial parameterization of the surface tension in terms of acid weight fraction and temperature is presented.
Atmospheric chemistry and environmental impact of the use of amines in carbon capture and storage (CCS).
Centre of Theoretical and Computational Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0372 Oslo, Norway. email@example.com.
This critical review addresses the atmospheric gas phase and aqueous phase amine chemistry that is relevant to potential emissions from amine-based carbon capture and storage (CCS). The focus is on amine, nitrosamine and nitramine degradation, and nitrosamine and nitramine formation processes. A comparison between the relative importance of the various atmospheric sinks for amines, nitrosamines and nitramines is presented.
Haas School of Business, University of California, Berkeley, Berkeley, CA 94720, USA.
Controversy surrounds occupational health and safety regulators, with some observers claiming that workplace regulations damage firms' competitiveness and destroy jobs and others arguing that they make workplaces safer at little cost to employers and employees. We analyzed a natural field experiment to examine how workplace safety inspections affected injury rates and other outcomes. We compared 409 randomly inspected establishments in California with 409 matched-control establishments that were eligible, but not chosen, for inspection. Compared with controls, randomly inspected employers experienced a 9.4% decline in injury rates (95% confidence interval =-0.177 to -0.021) and a 26% reduction in injury cost (95% confidence interval =-0.513 to -0.083). We find no evidence that these improvements came at the expense of employment, sales, credit ratings, or firm survival.
Copenhagen Center for Atmospheric Research (CCAR), Department of Chemistry, University of Copenhagen , Universitetsparken 5, 2100 KÃ¸benhavn Ã˜, Denmark.
Ethyl propionate is a model for fatty acid ethyl esters used as first-generation biodiesel. The atmospheric chemistry of ethyl propionate was investigated at 980 mbar total pressure. Relative rate measurements in 980 mbar N(2) at 293 Â± 0.5 K were used to determine rate constants of k(C(2)H(5)C(O)OC(2)H(5)+ Cl)=(3.11 Â± 0.35) Ã— 10(-11), k(CH(3)CHClC(O)OC(2)H(5)+ Cl)=(7.43 Â± 0.83) Ã— 10(-12), and k(C(2)H(5)C(O)OC(2)H(5)+ OH)=(2.14 Â± 0.21) Ã— 10(-12) cm(3) molecule(-1) s(-1). At 273-313 K, a negative Arrhenius activation energy of -3 kJ mol(-1) is observed.. The chlorine atom-initiated oxidation of ethyl propionate in 980 mbar N(2) gave the following products (stoichiometric yields): ClCH(2)CH(2)C(O)OC(2)H(5)(0.204 Â± 0.031), CH(3)CHClC(O)OC(2)H(5)(0.251 Â± 0.040), and C(2)H(5)C(O)OCHClCH(3)(0.481 Â± 0.088). The chlorine atom-initiated oxidation of ethyl propionate in 980 mbar of N(2)/O(2)(with and without NO(x)) gave the following products: ethyl pyruvate (CH(3)C(O)C(O)OC(2)H(5)), propionic acid (C(2)H(5)C(O)OH), formaldehyde (HCHO), and, in the presence of NO(x), PAN (CH(3)C(O)OONO(2)). The lack of acetaldehyde as a product suggests that the CH(3)CH(O)C(O)OC(2)H(5) radical favors isomerization over decomposition. From the observed product yields, we conclude that H-abstraction by chlorine atoms from ethyl propionate occurs 20.4 Â± 3.1%, 25.1 Â± 4.0%, and 48.1 Â± 8.8% from the CH(3)-,-CH(2)-, and -OCH(2)- groups, respectively. The rate constant and branching ratios for the reaction between ethyl propionate and the OH radical were investigated theoretically using quantum mechanical calculations and transition state theory. The stationary points along the reaction path were optimized using the CCSD(T)-F12/VDZ-F12//BH&HLYP/aug-cc-pVTZ level of theory; this model showed that OH radicals abstract hydrogen atoms primarily from the -OCH(2)- group (80%).
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Eur J Radiol. 2010 Jan ;73 (1):26-30 19926238
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Relative Tropospheric Photolysis Rates of HCHO and HCDO Measured at the European Photoreactor Facility.
The relative photolysis rates of HCHO and HCDO have been studied in May 2004 at the European Photoreactor Facility (EUPHORE) in Valencia, Spain. The photolytic loss of HCDO was measured relative to HCHO by long path FT-IR and DOAS detection during the course of the experiment. The isotopic composition of the reaction product H2 was determined by isotope ratio mass spectrometry (IRMS) on air samples taken during the photolysis experiments. The relative photolysis rate obtained by FTIR is jHCHO/jHCDO = 1.58 +/- 0.03. The ratios of the photolysis rates for the molecular and the radical channels obtained from the IRMS data, in combination with the quantum yield of the molecular channel in the photolysis of HCHO, PhiHCHO-->H2+CO (JPL Publication 06-2), are jHCHO-->H2+CO/jHCDO-->HD+CO = 1.82 +/- 0.07 and jHCHO-->H+HCO/(jHCDO-->H+DCO + jHCDO-->D+HCO)= 1.10 +/- 0.06. The atmospheric implications of the large isotope effect in the relative rate of photolysis and quantum yield of the formaldehyde isotopologues are discussed in relation to the global hydrogen budget.
Stereochemical course of tryptophan dehydrogenation during biosynthesis of the calcium-dependent lipopeptide antibiotics.
School of Chemistry and Manchester Interdisciplinary Biocentre, The University of Manchester, 131 Princess Street, Manchester M1 7ND, UK.
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