INVESTIGADORES
BLANCO Maria Belen
artículos
Título:
The Cl-initiated degradation of CH2=CHOC(O)CH3 , CH2=CHCH2OC(O)CH2CH3 and CH2=CHC(O)O(CH2)3CH3 in the troposphere
Autor/es:
M. B .BLANCO, I. BEJAN, I. BARNES, P. WIESEN AND M.A.TERUEL
Revista:
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Editorial:
SPRINGER HEIDELBERG
Referencias:
Año: 2009 vol. 16 p. 641 - 648
ISSN:
0944-1344
Resumen:
Background, aim and scope Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms, although almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical and Cl atom initiated oxidation of the compounds can be important.
Rate coefficients for the reactions of chlorine atoms with vinyl acetate (VAC), allyl acetate (AAC) and n-butyl acrylate (BUAC) have been determined at 298 K and atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate
Materials and Method The decay of the organics was followed using in situ FTIR spectroscopy and the rate coefficients were determined using a relative kinetic method and different hydrocarbon reference compounds.
Results The following room temperature rate coefficients (in cm3 molecule-1 s-1) were obtained: k1(Cl + CH3C(O)OCH=CH2) = (2.68 ± 0.91) x 10-10, k2(Cl + CH3C(O)OCH2CH=CH2) = (1.30 ± 0.45) x 10-10, k3(Cl + CH2=CHC(O)O(CH2)3CH3) = (2.50 ± 0.78) x 10-10, where the uncertainties are a combination of the 2¦Ò statistical errors from linear regression analyses and a contribution to cover uncertainties in the rate coefficients of the reference hydrocarbons.
Discussion This is the first kinetic study of the title reactions under atmospheric conditions. The kinetic data were analysed in terms of reactivity trends and used to estimate the atmospheric lifetimes of the esters and assess their potential importance in the marine atmosphere.
Conclusions Although reaction with OH radicals is the major atmospheric sink for the unsaturated esters studied, reaction with Cl atoms can compete in the early morning hours in coastal areas where the Cl concentration can reach peak values as high as 1 ¡Á105 atoms cm¨C3. The calculated residence times show that the chemistry of unsaturated esters will impact air quality locally near their emission sources.
Recommendations and Perspectives The reactions need to be studied over the range of temperatures and pressures generally encountered in the marine atmosphere. In addition, product studies should also be performed as a function of temperature since this will allow degradation mechanisms to be derived, which are representative for the wide range of conditions occurring in marine environments. Inclusion of the kinetic and product data in tropospheric numerical models will allow an assessment of potential environmental impacts of the esters for different marine pollution scenarios.