ICE (PHOTO)CHEMISTRY.
ICE AS A MEDIUM FOR LONG-TERM (PHOTO)CHEMICAL
TRANSFORMATIONS – ENVIRONMENTAL IMPLICATIONS
Petr Klán1* and Ivan Holoubek2
1
Department of Organic Chemistry, Faculty of Science, Masaryk University, Kotlarska 2,
611 37 Brno, Czech Republic; e-mail: klan@sci.muni.cz
2
RECETOX, Faculty of Science, Masaryk University, Veslarska 230b, 637 00 Brno, Czech
Republic; e-mail: holoubek@chemi.muni.cz
* Author to whom all correspondence should be addressed.
Abstract
This review accounts for the current knowledge about the distribution, accumulation,
and chemical/photochemical transformations of persistent, bioaccumulative, and toxic
compounds (PBTs) in water ice, especially in the connection with Polar Regions and
atmospheric cloud particles. (Photo)reactions on/in ice are discussed in terms of
photochemistry, photobiology, paleochemistry, as well as astrophysics. Authors propose a
model, in which a significant amount of some PBTs are generated by (photo)chemistry of
primary pollutants in ice, which may subsequently be released to the environment. It is argued
that ice photochemistry might play an important role in the chemical transformations in cold
ecosystems and in the upper atmosphere, particularly now when the ozone layer is partially
depleted.
Keywords: Ice; Snow; Photochemistry; UV radiation; PBTs; Polar Regions; Accumulation;
Distribution; Cloud particles; Atmosphere; Interstellar; Paleochemistry.
1
1. Introduction
Persistent, bioaccumulative, and toxic substances (PBTs) are of local, regional and/or
global concern, depending on their mobility in the environment (Wallack et al., 1998). The
global extent of pollution by PBT substances became apparent with their detection in remote
areas, such as the Arctic, where they have never been used or produced, at levels posing risks
to both wildlife (Barrie et al., 1992) and humans (Mulvad et al., 1996). The studies of
deposition/emission and transformation processes, as well as PBT bioavailability in terrestrial
ecosystems, will certainly be among the main topics of further research (UNEP, 1996; UN
ECE, 1996; UNEP, 1999).
Photochemical reactions, i.e. reactions induced by ultraviolet (UV) or visible light,
play a major role in the environment (Boule, 1999). Solar light is involved in a large number
of reactions in the atmosphere, in natural waters, on soil, and in living organisms (Roof, 1982;
Zepp, 1982; Boule, 1999). Photochemical activation is the principal driving force of
transformations of organic substances in the atmosphere and it plays a significant role in the
degradation of compounds which are inefficiently biodegraded in surface waters (Boule,
1999). Special attention is now paid to the photochemistry of many important and widely
distributed environmental groups of pollutants, such as polycyclic aromatic hydrocarbons
(PAHs), polychlorinated biphenyls (PCBs) (Pagni and Sigman, 1999), or pesticides (Méallier,
1999).
This review accounts for the current knowledge about distribution, accumulation, and
chemical/photochemical transformations of PBTs in water ice in the connection with Polar
Regions and atmospheric cloud particles. Knowledge about the (photo)chemical changes that
can occur in frozen water, are still quite limited. However, it seems that scientists have started
to pay more attention to this problem in the recent years.
2. Global Distribution and Arctic Accumulation of PBTs
Snow and ice are important components of cold ecosystems as well as of temperate
ecosystems in winter and they undoubtedly influence the fate and behaviour of PBTs (Hoff et
al., 1995). Over the past several years there has been a growing concern about the chemical
composition of snow pack and ice cores in Polar Regions (Bales and Wolf, 1995; Chappellaz
et al., 1997; Legrand, 1997; Sumner, 1999). Wolf and his coworker (Wolf, 1992; Wolff and
2
Suttie, 1994) noted that the Antarctic ice sheet is an important sink for atmospheric pollution
from other continents.
There is a common belief that the major mechanism for PBT substance mobility is a
cyclical evaporation from soil and water surfaces, where winds lift them along with water
vapor and dust into the air, transport them, and eventually, deposit them with rain, snow, and
solid particles. With repeated evaporation and deposition, the net result is a movement of
PBTs over long distances in the direction of atmospheric air movements. Models of this
behaviour correlate well with the measured PBT concentrations in the Northern Hemisphere
(Delzell et al., 1994).
Snow is an important form of precipitation, especially at higher altitudes and/or
latitudes (Tanabe et al., 1983; Cotham and Bidleman, 1991; de Voogt and Jansson, 1993;
Wania et al., 1998; 1999). In the latter areas, snow accumulation represents more than 75 %
of the annual precipitation (Gregor, 1990). Although it has been argued that snow is probably
a more efficient scavenger of organic compounds than rain, the opposite opinion has been
recently suggested (de Voogt and Jansson, 1993). Summer snow scavenging ratios do not
seem to differ much from rain scavenging ratios, whereas winter snow scavenging efficiency
may be lower by a factor of 3 (Cotham and Bidleman, 1991; Hoff and Barrie, 1986). The
differences between snow scavenging during winter and summer are probably due to riming
during the snow formation (Collet, et al., 1991).
The process of uptake of chemicals into nascent snow crystals can take place either by
adsorption onto the surface of a precipitating snow crystal (Goss, 1994; Hoff et al., 1995;
Bales and Choi, 1996; Fuhrer et al., 1996; Hutterli et al., 1999) or through co-deposition with
water into the growing crystals (Hanot and Domine, 1999). Measurements of the specific
snow surface area and formulation of a model describing the behavior of PBT substances in
an aging snowpack are definitely important recent developments (Wania, 1997). It was found
that sorption of non-polar compounds by ice surfaces was similar to that observed for water
films on mineral surfaces at higher temperatures (Hoff et al., 1995; Goss, 1994). The current
understanding of the interaction of organic vapors or organic components of atmospheric
aerosols with the surface of snow and ice is still insufficient, because of difficulties with the
quantitative treatment of these processes (Hoff et al., 1995; Scheringer et al., 2000).
3
3. Chemical Impurities in Ice: Physical Processes
The fate of organic chemicals is likely to be profoundly influenced by the unique
characteristics of high latitude ecosystems: low temperatures, the prolonged snow
precipitation, glaciers, ice caps, and permanently frozen water on the ground (permafrost).
Seas, lakes, and rivers may be ice-covered either permanently or for some part of the year.
Snow and ice covers limit the extent of direct dry particle deposition as well as the diffusive
gas exchange with water, soil, and vegetation. Nevertheless, the snow pack itself is a subject
to diffusive gas exchange (Wania et al., 1998).
Our present understanding of how PBTs interact with frozen water is relatively limited
and the process has only recently become a subject to detailed investigations. While inorganic
snow chemistry generated some information in the past several decades, the study of the fate
of organic chemicals in association with snow and ice has been largely neglected (Wania et
al., 1998). The limited understanding of the physics and chemistry of these systems, and
difficulties in conducting field studies under reproducible and controllable conditions, has
retarded the development of quantitative models describing snow-contaminant interactions,
yet there are successful ones (Dozier et al., 1991; Michalowski et al., 2000). In order to assess
and evaluate the environmental fate and behaviour of PBTs in cold ecosystems, it is of
particular importance to design an extensive and, if possible, a fully quantitative model of
(Wania et al., 1998). This would need to include:
1. the efficiency and nature of PBT snow scavenging from the atmosphere;
2. the behaviour of the chemicals in the snowpack, especially as they age;
3. the release of chemicals from the snowpack into the ecosystem;
4. the potential preservation of a chemical depositional record in permanent ice.
Contamination levels tend to be highest close to sources of a chemical and decline
with increasing distance as a result of dilution, dispersion, and degradation (Wania, 1999).
Higher concentrations of the pollutants deposited in Polar Regions are often explained in part
by their temperature-dependent partitioning (Paasivirta at al., 1985; Wania and Mackay, 1993;
Scheringer et al., 2000). The contaminants of the snow accumulating on the ground can be
transferred with the melted water to the terrestrial or aquatic environment underlying the snow
pack or they may volatilize back into the atmosphere (Pomeroy and Jones, 1996; Wania et al.,
1999). Volatilization and drainage can occur during different phases of the post-depositional
4
snow pack metamorphosis (Wania, 1999; Wania et al., 1999). There are large areas of sea-ice
formation in the Arctic Ocean (e.g. Kara and Laptev Sea), while the areas of sea ice melting
(e.g. Barents Sea, Baffin Bay, etc.) are relatively small resulting in a strong “funneling” effect
(Wania, 1997). Additionally, sea ice may be several years old by the time it melts. During its
lifetime, a multi-year ice floe had plenty of opportunities to collect contaminants by dry and
wet atmospheric deposition, and these contaminants are released to the water column in a
fairly short time period. Laboratory experiments have indicated the importance of interfacial
adsorption for the behaviour of organic compounds in snow and ice. First modeling attempts,
based on these studies, have opened the prospect of quantitative description of these processes
(Wania, 1999; Wania et al., 1999).
4. (Photo)chemical Processes in Ice and Snow
Water and ice are still regarded as poorly understood reaction media. Knowledge of
the chemical properties of ice or ice-like solids is important for understanding a wide variety
of phenomena. Photochemical and photophysical properties of water ice are quite complex
(Petrenko and Whitworth, 1999). Aggregation of isolated water molecules into a solid matrix
and photoproducts produced by initial irradiation, trapped into the matrix, strongly perturb ice
spectroscopic characteristics (Quickenden et al., 1996; Xu et al., 1997; Langford et al., 2000).
Ice is not completely transparent from 200 to 700 nm and photoproducts identified include
molecules of oxygen and hydrogen peroxide, atomic hydrogen, and hydroxyl radical
(Moorthy, 1965; Ohno, 1968; Eiben and Wieczorek, 1971; Matich et al., 1993; Ghormley and
Hochanadel, 1971; Quickenden et al., 1996; Khusnatdinov and Petrenko, 1997; Watanabe et
al., 2000). Absorption of light by sea ice (Perovich and Govoni, 1991; Askebjer et al., 1997;
Miller et al., 1997; Vincent, 1998) thus influences photosynthetic production of microalgae
(Soohoo et al., 1987; Ryan, 1992; Belzile et al., 2000).
Because of its physical and chemical properties and its common occurrence in
atmospheric aerosols, ice is an important part of atmospheric chemistry (Wang and Prinn,
2000; Prenni and Tolbert, 2001). Natural clouds (cirrus and convective clouds) and
anthropogenic tropospheric clouds (condensation trails of air planes) are made up of ice
crystals. Surface and near-surface reactions that are promoted by water ice most likely play a
key role in the formation of the Antarctic ozone hole (Solomon, 1988; Toon and Turco, 1991;
McConnell et al., 1992; Prather, 1992; Molina, 1993; Michalowski et al., 2000; Peterson and
5
Honrath, 2001) or may mediate some other chemical transformations (Fan and Jacob, 1992;
Brasseur and Granier, 1992; Hanson and Ravishankara, 1993). It is now generally accepted
that enhanced levels of Cl2 in the atmosphere, caused by release from chlorofluorocarbons,
are responsible for the destruction of ozone (Russell at al., 1996). Some chemical processes
occurring on/in ice result in chlorine and nitric acid formation (Molina at al., 1987; Tolbert et
al., 1988; Hanson and Ravishankara, 1992; Abbatt and Molina, 1992):
HCl + ClONO2  Cl2 + HNO3
HCl + HOCl  Cl2 + H2O
N2O5 + H2O  2HNO3
Studies of heterogeneous chemical reactivity of chlorine peroxide (ClOOCl) on metal
halide-doped ice surfaces indicated that the reaction was sensitive to the presence of ice (De
Haan and Birks, 1997). Reactions of the absorbed organic molecules at the surface of the ice
film, propene and 2-methyl-2-propanol, in the presence of Cl2 and HCl, respectively, were
recently investigated (Graham and Roberts, 1999a; 1999b). The reaction of coadsorbed
propene and chlorine was found to be very different from what occurs in aqueous solution.
Instead of chlorohydrine, the product of the reaction with water, 1,2-dichloropropane, was
identified as a major product. 2-Methyl-2-propanol was converted to 2-chloro-2methylpropane. The starting material was not reactive toward HCl; reactive chlorine was
derived from a dissociatively ionized state in the near surface region of the film. The
hydrogen bonding capabilities of water molecules of ice and proton transfer has been
investigated experimentally as well as theoretically in connection with ozone depletion (Kroes
and Clary, 1992a; 1992b; Silverstein et al., 1998; Schaff and Roberts, 1999; Thibert and
Domine, 1997; Thibert and Domine, 1998; Gertner and Hynes, 1998; Livingston and George,
1998; Holmes and Sodeau, 1999; Kobayashi et al., 2000; Pursell et al., 2000).
There is increasing evidence for post-depositional chemical alterations in accumulated
ice and snow. Organic as well inorganic matter found in ancient ice layers provides useful
information for palaeochemists and palaeobiologists, but it can also serve as a source of
information about some basic chemical reactions in this medium (Crutzen and Bruehl, 1993;
Neftel et al., 1995; Thompson, 1995). Protein oxidation over long-time periods has been, for
example, studied in human hair samples which are almost 1000 years old (Lubec at al., 1997).
6
It is believed that pre-industrial environmental system processes are well recorded in polar ice
cores (Delmas, 1992 and 1994; Fuhrer et al., 1993).
Interest in spectral properties of water ice, and their implications for possible
photochemical transformations in ice as a medium, received a substantial motivation in recent
years from its identification on outer solar system bodies and in interstellar space (Grim and
Greenberg, 1987; Mayer and Pletzer, 1986; Mukai, 1986). Such occurrence of ice is important
because it could allow life to be supported at those locations or might play a key role in the
formation of biologically interesting molecules (Kerridge, 1999). A chemical change in ice
can be promoted, due to penetrating cosmic radiation or absorbed solar radiation
(Allamandola et al., 1988; Schutte et al., 1993; Schutte, 1995; Bernstein et al., 1997; Johnson
and Quickenden, 1997; Tielens and Charnley, 1997; Chiar, 1997; Cottin et al., 1999;
Allamandola et al., 1999; Sandford et al., 2000; Gerakines, 2000; Duley, 2000; Moore et al.,
2001; Ehrenfreund, 2001). As an example, hexamethylentetraamine photolysis in frozen water
and its implications for astrochemistry has been reported (Berstein et al., 1994). The products
found were simple molecules such as HOCN, H2NCN, HNCO, CH3CN, N(CH3)3. Interesting
results have been obtained about photolysis of polycyclic aromatic hydrocarbons in the
laboratory under astrophysical conditions (T < 50 K; UV < 200 nm), which resulted in
oxidation of peripheral carbon atoms yielding aromatic alcohols, ketones, and ethers (Scheme
1) (Bernstein et al., 1999; Bernstein et al., 2001).
Scheme 1
Information on photochemical transformations in ice, other than that from
astrophysical research, is limited. Photolysis of chlorine dioxide (OClO) in amorphous and
polycrystalline ice yielded the chlorine peroxy radical, ClOO, and atomic chlorine (Pursell et
al., 1995; 1996; Graham et al., 1996). Photochemistry of chlorine nitrate adsorbed on HCldoped crystals produced Cl2O and Cl2 (Faraudo and Weibel, 2001). Kinetics of HO2 radicals
has been investigated in UV-irradiated frozen solutions of H2O2 by EPR techniques
(Bednarek and Plonka, 1994). McConnell an his coworkers (1992) have proposed that HBr
and brominated organic compounds, scavenged by ice crystals, might undergo photochemical
heterogeneous reactions resulting in the Br2 release. In addition, Sumner and Shepson (1999)
reasoned that formaldehyde photolysis can be a dominant source of oxidizing free radicals in
the lower polar troposphere and at the snow surface, facilitating the release of bromine into
the lower troposphere. Researchers recently showed that sunlight irradiation of snow results in
7
the release of significant amounts of gas phase NOx (NO + NO2) (Honrath et al.; 1999; 2000a;
2000b; Jones et al., 2000). The laboratory experiments revealed that the observed NO x
production is a result of nitrate photolysis. The authors suggested that this reaction could have
a potential impact on ice core records of oxidants. Since HNO3 is scavenged by cirrus clouds,
the NOx photorelease studies may clarify uncertainties of current models simulating the
[NOx]:[HNO3] ratios in the atmosphere. Another investigation of NO2 fluxes from the
photolyzed ice solid solution of KNO3 has recently been published (Dubowski et al., 2001).
The authors utilized the photoisomeration reaction of 2-nitrobenzaldehyde in the frozen
aqueous solution to determine the photon flux. The same reaction was used in the study of the
proton transport in the ice matrix (Konstantinov et al., 1982).
Scheme 2
In order to understand the photodeactivation mechanism of DNA, photodimerization
reactions of thymine (Scheme 2), pyrimidine, or uracil derivatives in frozen media, especially
water ice, were investigated (Wacker et al., 1961; Wang et al., 1965; Blackburn and Davies,
1966; Rahn and Hosszu, 1969; Khattak and Wang, 1969; Varghese, 1970; Borkman and
Yamanashi, 1974; Sasson and Wang, 1997; Fahr, 1978; Bose et al., 1984). Those reactions in
ice have been also utilized for synthetic reasons.
Scheme 3
Klán and his coworkers published three papers about unusual photobehaviour of
halobenzenes in ice (Klán et al., 2000; Holoubek et al., 2000; Klán et al., 2001). The
photolysis of these compounds in ice yielded very different photoproducts from those
observed in liquid water. Instead of phenol derivatives formed from the photoreaction
between water and organic halides in aqueous solution, biphenyl, terphenyl, and their
chlorinated (brominated) isomers were the only products found due to aggregation of the
starting molecules even in very diluted solutions (Scheme 3). A similar observation was made
by Huntley and the coworkers (1998), who found small amounts of biphenyl and
chlorobiphenyl (in addition to the major product benzene) in the photolysis of chlorobenzene
adsorbed on the ice films grown on a Ni(111) substrate under ultrahigh vacuum conditions.
The lack of water-molecule reactivity in the halobenzene experiments was explained in terms
of the effective reaction cavity (Weiss et al., 1993); the bimolecular reactions between the
8
host water molecules and the guest organic substances were restricted. As a model
photoreaction, the Norrish type II reaction of valerophenone was investigated in ice and other
solid solvents (Klán, Janošek et al., 2000) and it was found that its conformational motion in
the reaction cavity of ice was partially reduced.
Scheme 4
It is known that solutes tend to be largely segregated from the ice phase and are
dispersed at the grain boundaries or interstitial pores (Gross et al., 1987; Dash et al., 1995;
Petrenko and Whitworth, 1999). Photoreactions resembling liquid phase photochemistry are
expected in a quasi-liquid water layer on the surface of snow (ice) grains (Conklin and Bales,
1993) at higher (sub-zero) temperatures, especially when the organic substances are more
hydrophilic (i.e. water-soluble). Dubowski and Hoffmann (2000) reported results from
investigations on photochemical degradation of 4-nitrophenol in ice pellets. They found
similar photoproducts, hydroquinone, benzquinone, 4-nitrosophenol etc., as known from
4-nitrophenol photolysis in aqueous solution. The results suggest a similar mechanism for the
decomposition in both liquid and solid states (Scheme 4). The authors also discussed this
reaction as an archetypal process for photochemical behaviour of organic compounds in polar
ice and snow.
5. Ice as a Potential Source of Environmental Contamination
We have reasonable knowledge about the levels of PBTs (mainly pesticides and
PCBs) in Polar Regions because measurements have been made since the beginning of the
1960s (e.g., Barrie et al., 1992; Masclet et al., 1995; Chernyak, 1996). However, we have a
lack of knowledge about their potential (photo)chemical transformations in ice. Gregor (1990)
suggested that photodegradation is likely to become important only after revolatilization. It
has been argued that the final effect of these phenomena during snowmelt (revolatilization
followed by photolytic degradation) would be a significant reduction of the quantity of
pesticides and other PBTs entering the arctic aquatic environment. Hoffmann (1996)
suggested in his review two possible transformation pathways that can occur in ice: (1)
induced by high-energy cosmic radiation or by (2) UV solar radiation. The photochemical
reactions may be initiated by direct irradiation or sensitization by other UV absorbers present
9
in ice. Photodegradation by sunlight seems to be the most readily available, especially as the
ozone layer is becoming a less effective UV filter. Photochemical activation is evidently
feasible, due to the excellent transparency of ice, even at lower temperatures (photochemical
reactions are usually not very sensitive to temperature). Strongly absorbing pollutants might
partially filter out the radiation, which can cause lowering the photochemical activity of
compounds from deeper layers of ice. However, this should be only a minor effect because
their concentrations are very low. Light reflection and scattering (Grenfell et al., 1994)
certainly play a much more important role in diminishing the quantum efficiencies of
photochemical reactions in ice or snow.
Figure 1
Thanks to a relative lack of attention, information, and knowledge, there are serious
difficulties in the formulation of a model that would describe a general behaviour of PBTs in
ice. We recently discussed the problem of a long-range transport of PBTs to Polar Regions,
their deposition and accumulation, and the following photochemical transformations that
result in the formation of new kinds of PBTs (Klán et al., 2000; Holoubek et al., 2000; Klán et
al., 2001). Based on this discussion, we suggest a potentially new aspect of the fate of PBTs in
the polar environment or the upper atmosphere. The key processes in the step-by-step model
are (Figure 1):
1. Transport of PBTs through air, water, and solid particles to Polar Regions;
2. Their possible (photo)transformations in/on ice, resulting in “secondary pollutants”
which may be:
a) less toxic, eventually further degradable in nature, or
b) new types of PBTs, possibly more toxic and persistent;
3. Release of these compounds to the environment through evaporation or ice melt.
The possibility that ice photochemistry can lead to the formation of new and
unexpected organic compounds of a high environmental risk, supported by some laboratory
experiments, brings a new insight into the problem. A logical question that follows such
assumptions is: what will be the result of global warming processes if ice melts? It is apparent
that further research, that may reveal many surprising discoveries, is needed.
10
Acknowledgment:
We thank Kevin C. Jones for fruitful comments on the manuscript.
References:
Abbatt, J. P. D., Molina, M. J., 1992. The heterogeneous reaction of HOCl + HCl + Cl2 + H2O
on ice and nitric acid trihydrate – Reaction probabilities and stratospheric implications. J.
Geophys. Res. Lett. 19 (5), 461-464.
Allamandola, L. J., Sandford, S. A., Valero, G. J., 1988. Photochemical and thermal evolution
of interstellar precometary ice analogs. Icarus 76 (2), 225-252.
Allamandola, L. J., Bernstein, M. P., Sandford, S. A., Walker, R. L., 1999. Evolution of
interstellar ices. Space Sci. Rev. 90 (1-2), 219-232.
Askebjer, P. et al., 1997. UV and optical light transmission properties in deep ice at the South
Pole. Geophys. Res. Lett. 24 (11), 1355-1358.
Bales, R. C., Choi, J., 1996. Conceptual framework for interpretation of exchange processes.
NATO ASI Series I, 43, 319-338.
Barrie, L. A., Gregor, D., Hargrave, B., Lake, R., Muir, D., Shearer, R., Tracey, B., Bidleman,
T. F., 1992. Arctic contaminants: sources, occurrence and pathways. Sci. Total Environ.
122 (1-2), 1-74.
Bales, R. C., Wolf, E. W., 1995. Processes of chemical exchange between the atmosphere and
polar snow: Key to interpreting natural climate signals in ice cores. EOS Trans. AGU, 76,
477-482.
Bednarek J., and Plonka, A., 1994. ESR studies on reactivity of HO2 radicals in
polycrystalline ice – Nonmonotonic changes of disproportionation rate in the temperature
range 100-200 K. Rad. Phys. Chem. 44 (5), 485-489.
Belzile, C., Johannessen, S. C., Gosselin, M., Demers, S., Miller, W. L., 2000. Ultraviolet
attenuation by dissolved and particulate constituents of first-year ice during late spring in
an Arctic Polynya. Limnol. Ocean. 45 (6), 1265-1273.
Bernstein, M. P., Allamandola, L. J., Sandford, S. A., 1997. Complex organics in laboratory
simulations of interstellar/cometary ices. Life Sciences: Complex Organics in Space.
Adv. Space. Res. 19 (7), 991-998.
11
Bernstein, M. P., Dworkin, J. P., Sandford, S. A., Allamandola, L. J., 2001. Ultraviolet
irradiation of naphthalene in H2O ice: Implications for meteorites and biogenesis. Meteor.
Planet. Sci. 36 (3), 351-358.
Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Gillette, J. S., Clemett, S. J., Zare, R.
N., 1999. UV irradiation of polycyclic aromatic hydrocarbons in ices: production of
alcohols, quinones, and ethers. Science 283 (5405), 1135-1138.
Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Chang S., 1994. Infrared spectrum of
matrix-isolated hexamethylenetetraamine in Ar and H2O at cryogenic temperatures. J.
Phys. Chem. 98 (47), 12206-12210.
Blackburn, G. M.; Davies, R. J. H., 1966. Photochemistry of 1-methylthymine and 3methylthymine. J. Chem. Soc., C, Org. (15) 1342-1345.
Borkman, R. F.; Yamanashi, B. S., 1974. Photodimerization kinetics of thymine and thymined2. Photochem. Photobiol. 19 (2), 173-176.
Bose, S. N., Kumar, S., Davies, R. J. H.; Sethi, S. K., McCloskey, J. A., 1984. The
photochemistry of d(T-A) in aqueous solution and in ice. Nucleic Acids Res. 12 (20),
7929-47.
Boule, P. (Ed.), 1999. The Handbook of Environmental Chemistry, Vol. 2, Part L:
Environmental Photochemistry. Springer-Verlag, Berlin.
Brasseur, G., Granier, C., 1992. Mount-Pinatubo aerosols, chlorofluorocarbons, and ozone
depletion. Science 257 (5074), 1239-1242.
Chappellaz, J., Brook, E., Blunier, T., Malaize, B., 1997. CH4 and Delta O-18 of O-2 records
from Antarctic and Greenland ice: A clue for stratigraphic disturbance in the bottom part
of the Greenland ice core project and the Greenland ice sheet project 2 ice cores. J.
Geophys. Res.-Ocean 102 (C12) 26547-26557.
Chernyak, S. M., Rice, C. P., McConnel, L. L., 1996. Evidence of currently used pesticides in
air, ice, fog, seawater and surface microlayer in the Bering and Chukchi seas. Mar. Pollut.
Bull. 32 (5), 410-419.
Chiar, J. E., 1997. The nature and evolution of interstellar ices. Origins Life Evol. Biosphere
B 27 (1-3), 79-100.
Collett, J. L., Prévot, A. S. H., Staehelin, J., Waldvogel, A., 1991. Physical factors influencing
winter precipitation chemistry. Environ. Sci. Technol. 25 (4), 782-788.
Conklin, M. H., Bales, R. C., 1993. SO2 uptake on ice spheres: Liquid nature of the ice-air
interface. J. Geophys. Res. 98 (D9), 16851-16855.
12
Cotham, W. E., Bidleman, T. F., 1991. Estimating the atmospheric deposition of
organochlorine contaminants to the Arctic. Chemosphere 22 (1-2), 165-188.
Cottin, H., Gazeau, M. C., Doussin, J. F., Raulin, F., 1999. SEMAPh.Or.E COMETAIRE, A
tool for the study of the photoochemical decomposition of probable large organic
molecules in comets. First application: polyoxymethylene. Phys. Chem. Earth Pt. C 24
(5), 597-602.
Crutzen, P. J.; Bruhl, C., 1993. A model study of atmospheric temperatures and the
concentrations of ozone, hydroxyl, and some other photochemically active gases during
the glacial, the pre-industrial halocene, and the present. Geophys. Res. Lett. 20 (11),
1047-1050.
Dash, J. G., Fu, H. Y., Wettlaufer, J. S., 1995. The premelting of ice and its environmental
consequences. Rep. Prog. Phys. 58 (1), 115-167.
De Haan, D. O., Birks, J. W., 1997. Heterogeneous reactions of chloride peroxide with halide
ions. J. Phys. Chem. A 101 (43), 8026-8034.
de Voogt, P., Jansson, B., 1993. Vertical and long-range transport of persistent organics in the
atmosphere. Rev. Environ. Contam. Toxicol. 132, 1-27.
Delmas, J. R., 1992. Environmental information from ice cores. Rev. Geophys. 30 (1), 1-21.
Delmas, J. R., 1994. Ice records of the past environment. Sci. Total. Environ. 143 (1), 17-30.
Delzell, E., Giesy, J. P., Munro, I., Doull, J., Mackay, D., Williams, G., 1994. Regulatory
Toxicol. Pharmacol. Coulston, F. and Kolbey, A. C., Jr. (Eds.) Academic Press, Inc., San
Diego, CA, Ch. 5, pp.187-307.
Dozier, J., Gjessing, Y. T., Johannes, A. J., Morris, E. M., 1991. Chemical processes in snow
– Where should we go? NATO ASI Series G, 28, 457-460.
Dubowski, Y., Colussi, A. J., Hoffmann, M. R., 2001. Nitrogen dioxide release in the 302 nm
band photolysis of spray-frozen aqueous nitrate solutions. Atmospheric implications. J.
Phys. Chem. A 105 (20), 4928-4932.
Dubwski, Y., Hoffmann, M. R., 2000. Photochemical transformations in ice: Implications for
the fate of chemical species. Geophys. Res. Lett. 27 (20), 3321-3324.
Duley, W. W., 2000. Chemistry in grain aggregates. A source of complex molecules? Mon.
Not. R. Astron. Soc. 319 (3), 791-796.
Ehrenfreund, P., Bernstein, M. P., Dworkin, J. P., Sandford, S. A., Allamandola, L. J., 2001.
The photostability of amino acids in space. Astrophys. J. 550 (Part 2), L95-L99.
Eiben, K., Wieczorek, H., 1971. Reactions of electrons in irradiated ice. Ber. Bunsenges.
Phys. Chem. 75 (7), 676-678.
13
Fan, S. M., Jacob, D. J., 1992. Surface ozone depletion in Arctic spring sustained by bromine
reactions in aerosols. Nature 359 (6395), 522-524.
Fahr, E., Roth, G. P., Wuestenfeld, P., 1978. Gas chromatographic study of products formed
by UV irradiation of uracil and thymine in solution and ice matrix. Z. Naturforsch., B:
Anorg. Chem., Org. Chem. 33B (6), 646-51.
Faraudo, G. Weibel, D. E., 2001. Effect of HCl addition and temperature on the
heterogeneous chemistry and photochemistry of ClONO2 adsorbed on ice crystals. Prog.
React. Kinet. Mec. 26, 179-199.
Fuhrer, K., Hutterli, M., McConnel, J. R., 1996. Overview of recent field experiments for the
study of the air-snow transfer of H2O2 and HCHO. NATO ASI Series I, 43, 307-318.
Fuhrer, K., Neftel, A., Anklin M., Maggi, V., 1993. Continuous measurements of hydrogenperoxide, forlmadehyde, calcium and ammonium concentrations along the New Grip ice
core from Summit, Central Greenand. Atmos. Environ. A-Gen. 27 (12), 1873-1880.
Gerakines, P. A., Moore, M. H., Hudson, R. L., 2000. Carbonic acid production in H2O : CO2
ices - UV photolysis vs. proton bombardment. Astron. Astrophys. 357, 793-800.
Gertner, B. J., Hynes, J. T., 1998. Model molecular dynamics simulation of hydrochloric acid
ionization at the surface of stratospheric ice. Faraday Disc. (110), 301-322.
Ghormley, J. A., Hochanadel, C. J., 1971. Production of H, OH, and H2O2 in the flash
photolysis of ice. J. Phys. Chem. 75 (1), 40-44.
Grenfell, T. C., Warren, S. G., Mullen, P. C., 1994. Reflection of solar radiation by the
Antarctic snow surface at ultraviolet, visible, and near infrared wavelengths. J. Geophys.
Res. (Atmos.) 99 (D9), 18669-18684.
Goss, K. U., 1994. Adsorption of organic vapors on polar surfaces – Recent advances.
Environ. Sci. Pollut. Res. Int. 1, 34-37.
Gross, G. W., Guthjar, A., Caylor, K., 1987. Recent experimental work on solute
redistribution at the ice water interface. Implications for electrical properties and
interfaces processes. J. Phys. (Paris) 48C, 527-533.
Graham, J. D., Roberts, J. T., 1999a. Chemical reactions of organic molecules adsorbed at ice
1. Chlorine substitution in 2-methyl-2-propanol. Langmuir 16 (7), 3244-3248.
Graham, J. D., Roberts, J. T., 1999b. Chemical reactions of organic molecules adsorbed at ice
1. Chlorine addition to propene. J. Phys. Chem. B 104 (5), 978-982.
Graham, J. D., Roberts, J. T., Anderson, L. D., Grassian, V. H., 1996. The 367 nm
photochemistry of OClO thin films and OClO adsorbed on ice. J. Phys. Chem. 100 (50),
19551-19558.
14
Gregor, D. J., 1990. In: Kurtz, D. (Ed.): Long-range transport of pesticides. Lewis Publ.
Chelsea, Michigan, USA.
Grim, R. J. A., Greenberg, J. M., 1987. Photoprocessing of H2S in interstellar grain mantles as
an explanation for S-2 comets. Astr. Astrophys. 181, 155-168.
Hanot, L., Domine, F., 1999. Evolution of the surface area of a snow layer. Environ. Sci.
Technol. 33 (23), 4250-4255.
Hanson, D. R., Ravishankara, A. R., 1992. Investigation of the reactive and nonreactive
processes involving ClONO2 and HCl on water and nitric acid doped ice. J. Phys. Chem.
96 (6), 2682-2691.
Hanson, D. R., Ravishankara, A. R., 1993. Reactions of halogen species on ice surfaces.
NATO ASI Series I, 7, 281-90.
Hoff, R. M., Barrie, L. A., 1986. Air chemistry observations in the Canadian Arctic. Water
Sci. Technol. 18 (2), 97-107.
Hoff, R. M., Wania, F., Mackay, D., Gillham, R., 1995. Sorption of non-polar organic vapors
by ice and snow. Environ. Sci. Technol. 29 (8), 1982-1989.
Holmes, N. S., Sodeau, J. R., 1999. A study of interaction between halomethanes and water
ice. J. Phys. Chem. A 103 (24), 4673-4679.
Holoubek, I., Klán, P., Ansorgová, A., del Favero, D., 2000. Photochemistry of PBT
compounds in ice - New potential source of ice contamination? Organohalogen
Compounds 46, 228-231.
Hoffmann, M. R., 1996. Possible chemical transformations in snow and ice induced by solar
(UV photons) and cosmic irradiation (muons). NATO ASI Series I, 43, 353-377.
Honrath, R. E., Peterson, M. C., Guo, S., Dibb, J. E., Shepson, P. B., Cambell, B., 1999.
Evidence of NOx production within or upon ice particles in the Greenland snow pack.
Geophys. Res. Lett. 26 (6), 695-698.
Honrath, R. E., Guo, S., Peterson, M. C., Dziobak, M. P., Dibb, J. E., Arsenault, M. A.
(2000a): Photochemical production of gas phase NOx from ice crystal NO3-. J. Geophys.
Res. 105 (D19), 24183-24190.
Honrath, R. E., Peterson, M. C., Dziobak, M. P., Dibb, J. E., Arsenault, M. A., Green S. A.
(2000b): Release of NOx from sunlight-irradiated midlatitude snow. Geophys. Res. Lett.
27 (15), 2237-2240.
Huntley, D. R., Grimm, F. A., Vaughn, T. E., Syud, F. A., 1998. Adsorption and
photochemical, reactions of chlorinated hydrocarbons on ice surfaces. Abstr. Pap. Chem.
Am. Soc. 211, 183 (Part 1).
15
Hutzinger, O., 1982. The handbook of environmental chemistry. Vol. 2, Part C: Reactions and
processes. Springer-Verlag, Berlin.
Hutterli, M. A., Rothlisberger, R., Bales, R. C., 1999. Atmosphere-to-snow-to-firn transfer
studies of HCHO at Summit, Greenland. Geophys. Res. Lett. 26 (12), 1691-1694.
Johnson, R. E., Quickenden, T., 1997. Photolysis and radiolysis of water ice on outer solar
system bodies. J. Geophys. Res. 102 (E5), 10985-10996.
Jones, K. C., de Voogt P., 1999. Persistent organic pollutants (POPs): State of the science.
Environ. Pollut. 100 (1-3), 209-221.
Jones, A. E., Weller, R., Wolff, E. W., Jacobi, H.-W., 2000. Speciation and rate of
photochemical NO and NO2 production in Antarctic snow. Geophys. Res. Lett. 27 (3),
345-348.
Kerridge, J. F., 1999. Formation and processing of organics in the early Solar system. Space
Sci. Rev. 90 (1-2), 275-288.
Khattak, M. N., Wang, S. Y., 1969. Uracil photoproducts from uracil irradiated in ice. Science
163 (3873), 1341-1342.
Khusnatdinov, N. N., Petrenko, V. F., 1997. Experimental study of ice photolysis under UV
irradiation. J. Phys. Chem. B 101 (32), 6208-6211.
Klán, P., Ansorgová, A., Del Favero, D., Holoubek I., 2000. Photochemistry of chlorobenzene
in ice. Tetrahedron Lett. 41 (40), 7785-7789.
Klán, P., Del Favero, D., Ansorgová, A., Klánová, J., Holoubek I., 2001. Photodegradation of
halobenzenes in water ice. Environ. Sci. Pollut. R. 8 (3), 195-200.
Klán, P., Janosek, J., Kriz, Z., 2000. Photochemistry of valerophenone in solid solutions. J.
Photochem. Photobiol. A: Chem. 134 (1-2), 37-44.
Kobayashi, C., Saito, S. J., Ohmine, I., 2000. Mechanism of fast proton transfer in ice:
Potential energy surface and reaction coordinate analyses. J. Chem. Phys. 113 (20), 90909100.
Konstantinov, A. A., Kaminskaya, O. P., Grigorev, V. A., 1982. Photochemical injection of
protons into ice. Dokl. Akad. Nauk SSSR 264 (2), 488-90.
Kroes, G.-J., Clary, D. C., 1992a. Sticking of HCl and ClOH to ice: A computational study. J.
Phys. Chem. 96 (17), 7079-7088.
Kroes, G.-J., Clary, D. C., 1992b. Absorption of HCl on ice under stratospheric conditions –
A computational study. Geophys. Res. Lett. 19 (13), 1355-1358.
Langford, V. S., McKinley, A. J., Quickenden, T. I., 2000. Luminiscent photoproducts in UVirradiated ice. Acc. Chem. Res. 33 (10), 665-671.
16
Legrand, M., 1997. Ice-core records of atmospheric sulphur. Philos. T. Roy. Soc. B, 352, 241250.
Livingston, F. E., George, S. M., 1998. Effect of HNO3 and HCl on D2O desorption kinetics
from crystalline D2O ice. J. Phys. Chem. A 102 (50), 10280-10288.
Lubec, G., Zimmerman, M. R., Teschler, N. M., Stocchi, V., Aufderheide A.C., 1997. Protein
oxidation of a hair sample kept in Alaskan ice for 800-1000 years. Free Radical Res. 26
(5), 457-462.
Masclet, P., Hoyau, V., Jaffrezo, J., Legrand, M., 1995. Evidence for the presence of
polycyclic aromatic hydrocarbons in the polar atmosphere and in the polar ice of
Greenland. Analusis 23 (6), 250-252.
Matich, A. J., Bakker, M. G., Lennon, D., Quickenden, T. I., Freeman, C. G., 1993. O2
luminescence from UV-excited H2O and D2O ices. J. Phys. Chem. 97 (41), 10539-10553.
Mayer, E., Pletzer, R., 1986. Astrophysical implications of amorphous ice – A microporous
solid. Nature 319 (6051), 298-301.
McConnell, J. C., Henderson, G. S., Barrie, L., Bottenheim, J., Niki, H., Langford, C. H.,
Templeton, E. M. J., 1992. Photochemical bromine production implicated in Arctic
bounadry-layer ozone depletion. Nature 355 (6356), 150-152.
Méallier, P., 1999. Phototransformation of pesticides in aqueous solution. In: The handbook
of environmental chemistry. Boule P. (Ed.), Vol. 2, Part L: Environmental
Photochemistry. Ch. 9, pp. 241-261. Springer-Verlag, Berlin.
Michalowski, B. A., Francisco, J. S., Li, S.-M., Barrie, L., Bottenheim, J. W., Shepson, P. B.,
2000. A computer model study of multiphase chemistry in the Arctic boundary layer
during polar sunrise. J. Geophys. Res. 105 (D12), 15131-15145.
Miller, D., Quinby-Hunt, M. S., Hunt, A. J., 1997. Laboratory studies of angle- and
polarization-dependent light scattering in sea ice. Appl. Opt. 36 (6), 1278-1288.
Molina, M. J., 1993. Chemical interactions of tropospheric halogens on snow/ice. NATO ASI
Series I, 7, 273-9.
Molina, M. J., Tso, T.-L., Molina, L. T., Wang, F. C.-Y., 1987. Antarctic stratospheric
chemistry of chlorine nitrate, hydrogen chlorine and ice release of active chlorine.
Science 238 (4831), 1253-1257.
Moore, M. H., Hudson, R. L., Gerakines, P. A., 2001. Mid- and far-infrared spectroscopic
studies of the influence of temperature, ultraviolet photolysis and ion irradiation on
cosmic-type ices. Spectrochim. Acta A 57 (4), 843-858.
17
Moorthy, P. N., 1965. Photochemical charge-transfer reactions in frozen aqueous systems. I.
Electron transfer from the solute to the matrix. Formation and trapping of holes. J. Chem.
Phys. 3127-3131.
Mulvad, G., Pederson, H. S., Hansen, J. C., Dewail,y E., Jul, E., Pedersen, M. B., Bjerregaard,
P., Malcom, G. T., Deguchi, Y., Middaugh, J. P., 1996. Exposure of Greenlandic Inuit to
organochlorines and heavy metals through the marine food-chain: An international study.
Sci. Total Environ. 186, 137-139
Mukai, T., 1986. Analysis of a dirty water-ice. Model for cometary dust. Astr. Astrophys. 164
(2), 397-407.
Neftel, A., Bales, R. C., Jacob, D. J., 1995. H2O2 and HCHO in polar snow and their relation
to atmospheric chemistry. NATO ASI Series I, 30, 249-64.
Ohno, S., 1968. The H/D isotope effect in the conversion of the electron into a hydrogen atom
in aqueous acid solutions at 300 and 77 K. Bull. Chem. Soc. Jpn. 41 (6), 1301-1307.
Paasivirta, J., Knuutila, M., Paukku, R., 1985. Study of organochlorine pollutants in snow at
North Pole and comparison to the snow at north, central and south Finland. Chemosphere
14 (11-12), 1741-1748.
Pagni, R. M., Sigman, M. E., 1999. The photochemistry of PAHs and PCBs in water and on
solids. In: The handbook of environmental chemistry. Boule, P. (Ed.), Vol. 2, Ch. 6, 139179. Part L: Environmental Photochemistry. Springer-Verlag, Berlin.
Perovich, D. K., Govoni, J. W., 1991. Absorption coefficients of ice from 250 to 400 nm.
Geophys. Res. Lett. 18 (7), 1233-1235.
Peterson, M. C., Honrath, R.E., 2001. Observations of rapid photochemical destruction of
ozone in snowpack Interstitial Air. Geophys. Res. Lett. 28 (3), 511-514.
Petrenko, V. F., Whitworth, R. W., 1999. Physics of ice. Oxford University Press, Oxford.
Pomeroy, J. W., Jones, H. G., 1996. Wind-blown snow: sublimation, transport and changes to
polar snow. NATO ASI Series I 43, 453-489.
Prather, M. J., 1992. More rapid polar ozone depletion through the reaction of HOCl with HCl
on polar stratospheric clouds. Nature 355 (6360), 534-537.
Prenni, A. J.; Tolbert, M. A., 2001. Studies of polar stratospheric cloud formation. Acc.
Chem. Res. 34 (7), 545-553.
Pursell, C. J., Conyers, J., Alapat, P., Parveen, R., 1995. Photochemistry of chlorine dioxide
in ice. J. Phys. Chem. 99 (26), 10433-10437.
18
Pursell, C. J., Conyers, J., Denison, C., 1996. Photochemistry of chlorine dioxide in
polycrystalline ice (T = 140-185 K): Production of chloryl chloride, Cl-(OClO). J. Phys.
Chem. 100 (38), 15450-15453.
Pursell, C. J., Zaidi, M., Thompson, A., Fraser-Gaston, C., Vela, E., 2000. Acid-base
chemistry on crystalline ice: HCl+NH3. J. Phys. Chem. A 104 (3), 552-556.
Quickenden, T. I., Green, T. A., Lennon, D., 1996. Luminiscence from UV-irradiated
amorphous H2O ice. J. Phys. Chem. 100 (42), 16801-16807.
Rahn, R. O., Hosszu, J. L., 1969. Photochemical studies of thymine in ice. Photochem.
Photobiol. 10 (2), 131-7.
Roof, A. A. M., 1982. Basic principles of environmental photochemistry. In: The handbook of
environmental chemistry. Hutzinger O. (Ed.), Vol. 2, Part B: Reactions and Processes,
Ch. 1, 1-17. Springer-Verlag, Berlin.
Russell, J. M. I., Luo, M.-Z., Cicerone, R. J., Deaver, L. E., 1996. Satellite confirmation of the
dominance of chlorofluorocarbons in the global stratospheric chlorine budget. Nature 379
(6565), 526-529.
Ryan, K. G., 1992. UV radiation and photosynthetic production in Antartic sea ice
microalgae. J. Photochem. Photobiol. B: Biol. 13 (3-4), 235-240.
Sandford, S. A., Bernstein, M. P., Allamandola, L. J., Gillette, J. S., Zare, R. N., 2000.
Deuterium enrichment of polycyclic aromatic hydrocarbons by photochemically induced
exchange with deuterium-rich cosmic ices. Astrophys. J. 538 (2), 691-697.
Sasson, S., Wang, S. Y., 1977. Photochemistry of 5-bromouridine and 5-bromo-2'deoxyuridine in ice and in "puddles". Photochem. Photobiol. 26 (4), 357-361.
Schaff, J. E., Roberts, J. T., 1999. Interaction of acetonitrile with the surfaces of amorphous
and crystalline ice. Langmuir 15, (21) 7232-7237.
Scheringer, M., Wegmann, F., Fenner, K., Hungerbuhler, K., 2000. Investigation of the cold
condensation of persistent organic pollutants with a global multimedia fate model.
Environ. Sci. Technol. 34 (9), 1842-1850.
Schutte, W. A., 1995. The formation of organic molecules in astronomical ices. Prebiotic
chemistry on space 16, 53-60.
Schutte, W. A., Allamandola, L. J., Sandford, S. A., 1993. Formaldehyde and organicmolecule production in astrophysical ices at cryogenic temperatures. Science 259 (5098),
1143-1145.
Silverstein, K. A. T., Haymet, A. D. J., Dill, K. A., 1998. A simple model of water and the
hydrophobic effect. J. Am. Chem. Soc. 120 (33), 3166.
19
Solomon, S., 1988. The mystery of the antarctic ozone hole. Rev. Geophys. 26 (1), 131-148.
Soohoo, J. B., Palmisano, A. C., Kottmeier, S. T., Lizotte, M. P., Soohoo, S. L., Sullivan, C.
W., 1987. Spectral light absorption and quantum yield of photosynthesis in sea
microalgae and a bloom of Phaeocystis-Pouchetii from McMurdo Sound, Antarctica.
Mar. Ecol. Prog. Ser. 39 (2), 175-189.
Sumner, A. L., Shepson, P. B., 1999. Snowpack production of formaldehyde and its effect on
the Arctic troposphere. Nature 398 (6724), 230-233.
Thibert, E., Dominé, F., 1997. Thermodynamics and kinetics of the solid solution of HCl in
ice. J. Phys. Chem. B 101 (18), 3554-3565.
Thibert, E., Dominé, F., 1998. Thermodynamics and kinetics of the solid solution of HNO3 in
ice. J. Phys. Chem. B 102 (22), 4432-4439.
Tielens, A. G. G. M., Charnley, S. B., 1997. Circumstellar and interstellar synthesis of organic
molecules. Origins of Life and Evoluton of the Biosphere 27, 23-51.
Thompson, A. M., 1995. Photochemical modeling of chemical cycles: Issues related to the
interpretation of ice core data. NATO ASI Series I, 30, 265-97.
Tolbert, M. A., Rossi, M. J., Golden, D. M., 1988. Antarctic ozone depletion chemistry –
Reactions of N2O5 with H2O and HCl on ice surfaces. Science 240 (4855), 1018-1021.
Toon, O. B., Turco, R. P., 1991. Polar stratospheric clouds and ozone depletion. Sci. Am. 264
(6), 68-74
UN-ECE, 1998. Draft protocol to the convention on long-range air pollution on persistent
organic pollutants (EB.AIR/1998/2), The convention on long-range transboundary air
pollution. United Nations Economic and Social Council, Economic Commission for
Europe.
UNEP, 1996. UNEP survey on sources of POPs. A report prepared for an IFCS expert
meeting on POPs, Manila, Philippines.
UNEP, 1999. GEF PDF-B regionally based assessment of persistent toxic substances. Draft
report 1st Scientific and Technical Evaluation Workshop on persistent manufactured
chemicals produced for non-agricultural applications, persistent toxic and persistent
unintentional by-products of industrial and combustion processes, Geneva.
Varghese, A. J., 1970. Photochemistry of thymidine in ice. Biochemistry 9 (24), 4781-4787.
Vincent, W. F., Rae, R., Laurion, I., Howard-Williams, C., Priscu, J. C., 1998. Transparency
of Antarctic ice-covered lakes to solar UV radiation. Limnol. Oceanogr. 43 (4), 618-24.
Wacker, A., Weinblum, D., Traeger, L., Moustafa, Z., 1961. Photochemical reactions of uracil
and uridine. J. Mol. Biol. 3, 790-793.
20
Walack, H. W., Bakker, D.J., Brandt, I., Brostrom-Lundén, E., Brouwer, A., Bull, K. R.,
Gough, C., Guardans, R., Holoubek, I., Jansson, B., Koch, R., Kuylenstirna, J., Lecloux,
A., Macka,y D., McCutcheon, P., Mocarelli, P., Taalman, R. D. F., 1998. Controlling
persistent organic pollutants – What next? Environ. Toxicol. Pharmacol. 6, 143-175.
Wang, S. Y., 1964. The mechanism for frozen aqueous solution irradiation of pyrimidines.
Photochem. Photobiol. 3 (4), 395-8.
Wang, C., Prinn, R. G., 2000. On the roles of deep convective clouds in troposheric
chemistry. J. Geophys. Res. (Atmos.) 105 (D17), 22269-22297.
Wania, F., 1997. Modeling the behaviour of non-polar organic chemicals in an ageing snow
pack. Chemosphere 35 (10), 2345-2363.
Wania, F., 1999. On the origin of elevated levels of persistent chemicals in the environment.
Environ. Sci. Pollut. Res. 6 (1), 11-19.
Wania, F., Hoff, J. T., Jia, C. Q., Mackay, D., 1998. The effects of snow and ice on the
environmental behaviour of hydrophobic organic chemicals. Environ. Pollut. 102 (1), 2541.
Wania, F., Mackay, D., 1993. Global fractionation and cold condensation of low volatility
organochlorine compounds in Polar Regions. Ambio 22 (1), 10-18.
Watanabe, N., Horii, T.; Kouchi, A., 2000. Measurements of D2 yields from amorphous D2O
ice by ultraviolet irradiation at 12 K. Astrophys. J. 541 (Part 1), 772-778.
Weiss, R.G., Ramamurthy, V., Hammond, G.S., 1993. Photochemistry in organized media: A
model. Acc. Chem. Res. 26 (10), 530-536.
Wolff, E., 1992. The influence of global and local atmospheric pollution on the chemistry of
Antarctic snow and ice. Marine Pollution Bull. 25 (9-12), 274-280.
Wolff, E., Suttie, E. D., 1994. Antarctic snow record of Southern Hemisphere lead pollution.
Geophys. Res. Ett. 21 (9), 781-784.
Xu, L., Zhang, G., Ding, J., Chen, H., 1997. Light scattering by polydispersions of randomly
oriented hexagonal ice crystals: Phase function analyses. Optik 106 (3), 103-114.
Zepp, R. G., 1982. Experimental approaches to environmental photochemistry. In: The
handbook of environmental chemistry. Hutzinger O. (Ed.), Vol. 2, Part B: Reactions and
Processes, Ch. 2, 19-41. Springer-Verlag, Berlin.
21
O
OH
H
H
160 nm
+
ice
O
Scheme 1: Photochemistry of benzo[ghi]perylene in ice under astrophysical conditions
O
O
HN
O
h
N
H
ice
O
HN
O
NH
N
H
N
H
O
Scheme 2: Photodimerization of thymine in ice
22
Cl
h
ice
Cl x
Cl x
Cl y
Cl y
Cl z
x, y, z = 0-3
Scheme 3: Production of very toxic substances from less harmful chemicals in ice
OH
O
OH
OH
O
OH
NO
h
ice
NO 2
Scheme 4: Photochemical degradation of 4-nitrophenol in ice pellets
23
cloud
products of
ice (photo)chemistry
ice or snow
PBTs
GLOBAL
TRANSPORT
DEPOSITION
ACCUMULATION
(PHOTO)CHEMISTRY
RELEASE TO
THE ENVIRONMENT
Figure 1: Ice photochemistry and its implication on the environment.
24