Detailed Information on Publication Record

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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TY  - JOUR
ID  - 752291
AU  - Matykiewiczová, Nina - Klánová, Jana - Klán, Petr
PY  - 2007
TI  - Photochemical degradation of PCBs in snow.
JF  - Environmental Science & Technology
VL  - 41
IS  - 41
SP  - 8308-8314
EP  - 8308-8314
SN  - 0013936X
KW  - Photochemistry
KW  - Irradiation
KW  - Snow
KW  - Ice
KW  - Persistent organic pollutants
KW  - Polychlorinated biphenyls
KW  - Hydrogen peroxide.
N2  - 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.
ER  -

Basic information
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
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
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

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)
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)

Links
GA205/05/0819, research and development project	Name: Environmentální důsledky fotochemických transformací v ledu a sněhu
GA205/05/0819, research and development project	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)
MSM0021622412, plan (intention)	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)