Surface-Enhanced Nitrate Photolysis on Ice

Marcotte, Guillaume; Marchand, P.; Pronovost, S.; Ayotte, Patrick; Laffon, C.; Parent, P.

doi:10.1021/jp511173w

Cited by 23 publications

(26 citation statements)

References 71 publications

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“…However, when temperature is increased at 140 K, amorphous samples are irreversibly transformed to cubic crystal ice, leading to a reduction of the SSA by a factor of 100 or even higher (Ocampo and Klinger, 1982), which are common values of freshly atmospheric ice samples. It is worth noting that amorphous solid water (ASW) has recently been chosen as a model for the disordered interstitial air-ice interface within snowpack (Marcotte et al, 2015).…”

Section: Experimental Methodsmentioning

confidence: 99%

Photolysis of frozen iodate salts as a source of active iodine in the polar environment

Gálvez¹,

Baeza‐Romero²,

Sanz³

et al. 2015

Preprint

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Abstract. Reactive halogens play a key role in the oxidation capacity of the polar troposphere. However, sources and mechanisms, particularly those involving active iodine, are still poorly understood. In this paper, the photolysis of an atmospherically relevant frozen iodate salt has been experimentally studied using infrared (IR) spectroscopy. The samples were generated at low temperatures in the presence of different amounts of water. The IR spectra have confirmed that under near-UV/Vis radiation iodate is efficiently photolyzed. The integrated IR absorption coefficient of the iodate anion on the band at 750 cm−1 has been measured to be A = 9.5 × 10−17 cm molec−1. Using this value, a lower limit of the integrated absorption cross section of iodate, in an ammonium frozen salt, has been estimated for the first time at wavelengths relevant for tropospheric studies (σ = 1.1 × 10−20 cm2 nm molec−1 from 300 to 900 nm). According to this, we suggest that the photolysis of iodate in frozen salt can potentially provide a pathway for the release of active iodine to the polar atmosphere.

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Section: Experimental Methodsmentioning

confidence: 99%

Photolysis of frozen iodate salts as a source of active iodine in the polar environment

Gálvez¹,

Baeza‐Romero²,

Sanz³

et al. 2015

Preprint

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“…Second, being adsorbed to the surface of ice crystals, redeposited nitrate should be more easily photolyzed. In a laboratory experiment by Marcotte et al (2015), photolysis of nitrate on the ice surface was enhanced by a factor of 3 over nitrate in the bulk ice phase. Finally, redeposition of reactive nitrogen is in the form of both nitric and pernitric acid (Slusher et al, 2002).…”

Section: Estimating Seasonal No X Emission Fluxes For the Sp Regionmentioning

confidence: 99%

The meteorology and chemistry of high nitrogen oxide concentrations in the stable boundary layer at the South Pole

Neff

Crawford

Buhr³

et al. 2018

Atmos. Chem. Phys.

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“…Second, being adsorbed to the surface of ice crystals, redeposited nitrate should be more easily photolyzed. In a laboratory experiment by (Marcotte et al 2015), photolysis of nitrate on the ice surface was enhanced by a factor of three over nitrate in the bulk ice phase. Finally,…”

Section: Estimating Seasonal No X Emission Fluxes For the Sp Regionmentioning

confidence: 99%

The Meteorology and Chemistry of High Nitrogen Oxide Concentrations in the Stable Boundary Layer at the South Pole

Neff¹,

Buhr²,

Nicovich³

et al. 2017

Preprint

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Abstract. Four summer seasons of nitrogen oxide (NO) concentrations were obtained at the South Pole during the Sulfur Chemistry in the Antarctic Troposphere (ISCAT) program (1998 and 2000) and the Antarctic Tropospheric Chemistry Investigation (ANTCI) in (2003,. Together, analyses of their data here provide insight into the large-to-small scale meteorology that sets the stage for high NO and the significant variability that occurs day-to-day, within seasons and year-toyear. In addition, these observations reveal the interplay between physical and chemical processes at work in the stable 15 boundary layer of the high Antarctic plateau. We found a systematic evolution of the large-scale wind system over the ice sheet from winter to summer that controls the surface boundary layer and its effect on NO: Initially in early spring (Days 280-310) the transport of warm air and clouds over West Antarctica dominates the environment over the South Pole; In late spring (Days 310-340), of significance to NO, the winds at 300-hPa exhibit a bimodal behavior alternating between NW and SE; In early summer (Days 340-375), the flow aloft is dominated by winds from the Weddell Sea. During late spring, winds 20 aloft from the SE are strongly associated with clear skies, shallow stable boundary layers, and light surface winds from the east: it is under these conditions that the highest NO occurs. Examination of the winds at 300 hPa from 1961 to 2013 shows that this seasonal pattern has not changed significantly although the last twenty years have seen an increasing trend in easterly surface winds at the South Pole. What has also changed is the persistence of the ozone hole, often into early summer. With lower total ozone column density and higher sun elevation, the highest actinic flux responsible for the 25 photolysis of snow nitrate now occurs in late spring under the shallow boundary layer conditions optimum for high accumulation of NO. This may occur via the non-linear HO X -NO X chemistry proposed after the first ISCAT field programs and NO X recycling to the surface where quantum yields may be large under the low-snow-accumulation regime of the Antarctic plateau. During the 2003 field program a sodar made direct measurements of the stable boundary layer depth (BLD), a key factor in explaining the chemistry of the high NO concentrations. Because direct measurements were not 30 available in the other years, we developed an estimator for BLD using direct observations obtained in 2003 and step-wise linear regression with meteorological data from a 22-m tower (that was tested against independent data obtained in 1993). These data were then used with assumptions about the column abundance of NO to estimate surface fluxes of NO X . These results agreed in magnitude with results at Concordia Station and confirmed significant daily, intraseasonal and interannual variability in NO and its flux from the snow surface. Finally, we found that synoptic to mesoscale eddies governed the 35 boundary layer circulation and accumulation pathways fo...

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Surface-Enhanced Nitrate Photolysis on Ice

Cited by 23 publications

References 71 publications

Photolysis of frozen iodate salts as a source of active iodine in the polar environment

Photolysis of frozen iodate salts as a source of active iodine in the polar environment

The meteorology and chemistry of high nitrogen oxide concentrations in the stable boundary layer at the South Pole

The Meteorology and Chemistry of High Nitrogen Oxide Concentrations in the Stable Boundary Layer at the South Pole

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