Photoformation of hydroxyl radical on snow grains at Summit, Greenland

Anastasio, Cort; Galbavý, Š; Hutterli, Manuel A.; Burkhart, John F.; Friel, Donna K.

doi:10.1016/j.atmosenv.2006.12.011

Cited by 57 publications

(60 citation statements)

References 45 publications

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“…Subsequent studies also concluded that the detection of NO − 2 is only possible after the initial photo fragments (i.e. NO − 2 and O) escape the ice cage surrounding them Anastasio, 2003, 2007;Anastasio et al, 2007). Kahan et al (2010a, c) observed similar apparent rates for unimolecular and bimolecular reactions occurring in large ice cubes and in aqueous solution.…”

Section: Physical Environmentsmentioning

confidence: 73%

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

et al. 2014

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Abstract. Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air–ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed.

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Section: Physical Environmentsmentioning

confidence: 73%

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

et al. 2014

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“…OH in snow is formed by photochemical mechanisms, with HOOH likely being the primary precursor, and most of the OH production (90%) occurring in the top 10 cm of the snowpack (Chu and Anastasio 2005;Anastasio et al 2007;France et al 2007). Since the NWT snowpack sustains elevated concentrations of (NO ?…”

Section: Resultsmentioning

confidence: 99%

Fluxes and chemistry of nitrogen oxides in the Niwot Ridge, Colorado, snowpack

et al. 2009

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The effect of snow cover on surfaceatmosphere exchanges of nitrogen oxides (nitrogen oxide (NO) ? nitrogen dioxide (NO 2 ); note, here 'NO 2 ' is used as surrogate for a series of oxidized nitrogen gases that were detected by the used monitor in this analysis mode) was investigated at the high elevation, subalpine (3,340 m asl) Soddie site, at Niwot Ridge, Colorado. Vertical (NO ? NO 2 ) concentration gradient measurements in interstitial air in the deep (up to *2.5 m) snowpack were conducted with an automated sampling and analysis system that allowed for continuous observations throughout the snow-covered season. These measurements revealed sustained, highly elevated (NO ? NO 2 ) mixing ratios inside the snow. Nitrogen oxide concentrations were highest at the bottom of the snowpack, reaching levels of up to 15 ppbv during mid-winter. Decreasing mixing ratios with increasing distance from the soilsnow interface were indicative of an upwards flux of NO from the soil through the snowpack, and out of the snow into the atmosphere, and imply that biogeochemical processes in the subnival soil are the predominant NO source. Nitrogen dioxide reached maximum levels of *3 ppbv in the upper layers of the snowpack, i.e., *20-40 cm below the surface. This behavior suggests that a significant fraction of NO is converted to NO 2 during its diffusive transport through the snowpack. Ozone showed the opposite behavior, with rapidly declining levels below the snow surface. The mirroring of vertical profiles of ozone and the NO 2 /(NO ? NO 2 ) ratio suggest that titration of ozone by NO in the snowpack contributes to the ozone reaction in the snow and to the ozone surface deposition flux. However, this surface efflux of (NO ? NO 2 ) can only account for a minor fraction of ozone deposition flux over snow that has been reported at other mid-latitude sites. Neither (NO ? NO 2 ) nor ozone levels in the interstitial air showed a clear dependence on incident solar irradiance, much in contrast to observations in polar snow. Comparisons with findings from polar snow studies reveal a much different (NO ? NO 2 ) and ozone snow chemistry in this alpine environment. Snowpack concentration gradients and diffusion theory were applied to estimate an average, wintertime (NO ? NO 2 ) flux of 0.005-0.008 nmol m -2 s -1 , which is of similar magnitude as reported (NO ? NO 2 ) fluxes

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“…O 3 deposition to snow and concentrations inside the snowpack has been found to be low (Zeller and Hehn, 1995;Helmig et al, 2009b;Bocquet et al, 2011). OH concentrations may be higher under sunny conditions (Anastasio et al, 2007;Beyersdorf et al, 2007), however, light levels on boreal forest floor during winter are very low. Thus, for oxidative reactions the snow-air interface, including the top layers of the snowpack, seems to be more important than the deeper layers of the snowpack.…”

Section: Sources and Sinks Of Snowpack Vocsmentioning

confidence: 99%

“…However, as discussed already in Sect. 4.2, the concentrations of the main oxidants, OH and O 3 , inside the snowpack are presumably low, except for the surface layer of the snowpack (Zeller and Hehn, 1995;Anastasio et al, 2007;Beyersdorf et al, 2007), as are the temperature and light levels, all of which reduce the reactivity of VOCs.…”

Section: Voc Fluxesmentioning

confidence: 99%

Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

et al. 2012

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Abstract. Soil provides an important source of volatile organic compounds (VOCs) to atmosphere, but in boreal forests these fluxes and their seasonal variations have not been characterized in detail. Especially wintertime fluxes are almost completely unstudied. In this study, we measured the VOC concentrations inside the snowpack in a boreal Scots pine (Pinus sylvestris L.) forest in southern Finland, using adsorbent tubes and air samplers installed permanently in the snow profile. Based on the VOC concentrations at three heights inside the snowpack, we estimated the fluxes of these gases. We measured 20 VOCs from the snowpack, monoterpenes being the most abundant group with concentrations varying from 0.11 to 16 µg m −3 . Sesquiterpenes and oxygencontaining monoterpenes were also detected. Inside the pristine snowpack, the concentrations of terpenoids decreased from soil surface towards the surface of the snow, suggesting soil as the source for terpenoids. Forest damages (i.e. broken treetops and branches, fallen trees) resulting from heavy snow loading during the measurement period increased the terpenoid concentrations dramatically, especially in the upper part of the snowpack. The results show that soil processes are active and efficient VOC sources also during winter, and that natural or human disturbance can increase forest floor VOC concentrations substantially. Our results stress the importance of soil as a source of VOCs during the season when other biological sources, such as plants, have lower activity.

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Photoformation of hydroxyl radical on snow grains at Summit, Greenland

Cited by 57 publications

References 45 publications

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow

Fluxes and chemistry of nitrogen oxides in the Niwot Ridge, Colorado, snowpack

Snowpack concentrations and estimated fluxes of volatile organic compounds in a boreal forest

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