Photochemical degradation of PCBs in snow.
MATYKIEWICZOVÁ, Nina, Jana KLÁNOVÁ and Petr KLÁN. Photochemical degradation of PCBs in snow. Environmental Science & Technology. USA, 2007, vol. 41, No 41, p. 8308-8314. ISSN 0013-936X. |
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Basic information | |
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Original name | Photochemical degradation of PCBs in snow. |
Name in Czech | Fotochemická degradace PCBs ve sněhu. |
Authors | MATYKIEWICZOVÁ, Nina (203 Czech Republic), Jana KLÁNOVÁ (203 Czech Republic) and Petr KLÁN (203 Czech Republic, guarantor). |
Edition | Environmental Science & Technology, USA, 2007, 0013-936X. |
Other information | |
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Original language | English |
Type of outcome | Article in a journal |
Field of Study | 10401 Organic chemistry |
Country of publisher | United States of America |
Confidentiality degree | is not subject to a state or trade secret |
Impact factor | Impact factor: 4.363 |
RIV identification code | RIV/00216224:14310/07:00020846 |
Organization unit | Faculty of Science |
UT WoS | 000251582800019 |
Keywords in English | Photochemistry; Irradiation; Snow; Ice; Persistent organic pollutants; Polychlorinated biphenyls; Hydrogen peroxide. |
Tags | Hydrogen peroxide., ice, irradiation, Persistent organic pollutants, Photochemistry, Polychlorinated biphenyls, snow |
Tags | International impact, Reviewed |
Changed by | Changed by: prof. RNDr. Luděk Bláha, Ph.D., učo 15473. Changed: 25/6/2009 09:58. |
Abstract |
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This work represents the first laboratory study known to the authors describing photochemical behavior of persistent organic pollutants in snow at environmentally relevant concentrations. The snow samples were prepared by shock freezing of the corresponding aqueous solutions in liquid nitrogen and were UV irradiated in a photochemical cold chamber reactor at minus 25 C, in which simultaneous monitoring of snow air exchange processes was also possible. The main photodegradation pathway of two model snow contaminants, PCB 7 and PCB 153 (c 100 ng/kg), was found to be reductive dehalogenation. Possible involvement of the water molecules of snow in this reaction has been excluded by performing the photolyses in D2O snow. Instead, trace amounts of volatile organic compounds have been proposed to be the major source of hydrogen atom in the reduction, and this hypothesis was confirmed by the experiments with deuterated organic co-contaminants, such as d6 ethanol or d8 tetrahydrofuran. It is argued that bimolecular photoreduction of PCBs was more efficient or feasible than any other phototransformations under the experimental conditions used, including the coupling reactions. The photodegradation of PCBs, however, competed with a desorption process responsible for the pollutant loss from the snow samples, especially in case of lower molecular-mass congeners. Organic compounds, apparently largely located or photoproduced on the surface of snow crystals, had a predisposition to be released to the air but, at the same time, to react with other species in the gas phase. It is concluded that physico-chemical properties of the contaminants and trace co-contaminants, their location and local concentrations in the matrix, and the wavelength and intensity of radiation are the most important factors in evaluation of organic contaminants lifetime in snow. Based on the results, it has been estimated that the average lifetime of PCBs in surface snow, connected exclusively to the photoreductive dechlorination process, is 1-2 orders of magnitude longer than that in surface waters when subjected to the equivalent solar radiation. However, in case that the concentration of the hydrogen peroxide in natural snow is sufficient, the photoinduced oxidation process could succeed the photoreductive dechlorination and evaporative fluxes as the major sink. |
Abstract (in Czech) |
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This work represents the first laboratory study known to the authors describing photochemical behavior of persistent organic pollutants in snow at environmentally relevant concentrations. The snow samples were prepared by shock freezing of the corresponding aqueous solutions in liquid nitrogen and were UV irradiated in a photochemical cold chamber reactor at minus 25 C, in which simultaneous monitoring of snow air exchange processes was also possible. The main photodegradation pathway of two model snow contaminants, PCB 7 and PCB 153 (c 100 ng/kg), was found to be reductive dehalogenation. Possible involvement of the water molecules of snow in this reaction has been excluded by performing the photolyses in D2O snow. Instead, trace amounts of volatile organic compounds have been proposed to be the major source of hydrogen atom in the reduction, and this hypothesis was confirmed by the experiments with deuterated organic co-contaminants, such as d6 ethanol or d8 tetrahydrofuran. It is argued that bimolecular photoreduction of PCBs was more efficient or feasible than any other phototransformations under the experimental conditions used, including the coupling reactions. The photodegradation of PCBs, however, competed with a desorption process responsible for the pollutant loss from the snow samples, especially in case of lower molecular-mass congeners. Organic compounds, apparently largely located or photoproduced on the surface of snow crystals, had a predisposition to be released to the air but, at the same time, to react with other species in the gas phase. It is concluded that physico-chemical properties of the contaminants and trace co-contaminants, their location and local concentrations in the matrix, and the wavelength and intensity of radiation are the most important factors in evaluation of organic contaminants lifetime in snow. Based on the results, it has been estimated that the average lifetime of PCBs in surface snow, connected exclusively to the photoreductive dechlorination process, is 1-2 orders of magnitude longer than that in surface waters when subjected to the equivalent solar radiation. However, in case that the concentration of the hydrogen peroxide in natural snow is sufficient, the photoinduced oxidation process could succeed the photoreductive dechlorination and evaporative fluxes as the major sink. |
Links | |
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GA205/05/0819, research and development project | Name: Environmentální důsledky fotochemických transformací v ledu a sněhu |
Investor: Czech Science Foundation, Enviromental consequences of photochemical processes in ice and snow | |
MSM0021622412, plan (intention) | Name: Interakce mezi chemickými látkami, prostředím a biologickými systémy a jejich důsledky na globální, regionální a lokální úrovni (INCHEMBIOL) (Acronym: INCHEMBIOL) |
Investor: Ministry of Education, Youth and Sports of the CR, Interactions among the chemicals, environment and biological systems and their consequences on the global, regional and local scales (INCHEMBIOL) |
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