It has been shown that sunlit snow and ice plays an important role in processing atmospheric species. Photochemical production of a variety of chemicals has recently been reported to occur in snow/ice and the release of these photochemically generated species may significantly impact the chemistry of the overlying atmosphere. Nitrogen oxide and oxidant precursor fluxes have been measured in a number of snow covered environments, where in some cases the emissions significantly impact the overlying boundary layer. For example, photochemical ozone production (such as that occurring in polluted mid-latitudes) of 3–4 ppbv/day has been observed at South Pole, due to high OH and NO levels present in a relatively shallow boundary layer. Field and laboratory experiments have determined that the origin of the observed NOx flux is the photochemistry of nitrate within the snowpack, however some details of the mechanism have not yet been elucidated. A variety of low molecular weight organic compounds have been shown to be emitted from sunlit snowpacks, the source of which has been proposed to be either direct or indirect photo-oxidation of natural organic materials present in the snow. Although myriad studies have observed active processing of species within irradiated snowpacks, the fundamental chemistry occurring remains poorly understood. Here we consider the nature of snow at a fundamental, physical level; photochemical processes within snow and the caveats needed for comparison to atmospheric photochemistry; our current understanding of nitrogen, oxidant, halogen and organic photochemistry within snow; the current limitations faced by the field and implications for the future.

/pdf/an-overview-of-snow-photochemistry-evidence-mechanisms-and-yaeoz9jq34.pdf

An overview of snow photochemistry: evidence, mechanisms and impacts

Brown algae of the Laminariales (kelps) are the strongest accumulators of iodine among living organisms. They represent a major pump in the global biogeochemical cycle of iodine and, in particular, the major source of iodocarbons in the coastal atmosphere. Nevertheless, the chemical state and biological significance of accumulated iodine have remained unknown to this date. Using x-ray absorption spectroscopy, we show that the accumulated form is iodide, which readily scavenges a variety of reactive oxygen species (ROS). We propose here that its biological role is that of an inorganic antioxidant, the first to be described in a living system. Upon oxidative stress, iodide is effluxed. On the thallus surface and in the apoplast, iodide detoxifies both aqueous oxidants and ozone, the latter resulting in the release of high levels of molecular iodine and the consequent formation of hygroscopic iodine oxides leading to particles, which are precursors to cloud condensation nuclei. In a complementary set of experiments using a heterologous system, iodide was found to effectively scavenge ROS in human blood cells.

https://www.pnas.org/content/pnas/105/19/6954.full.pdf

Iodide accumulation provides kelp with an inorganic antioxidant impacting atmospheric chemistry.

We have examined the 532-nm aerosol backscatter coefficient measurements by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) for their use in the monitoring of stratospheric aerosol. CALIPSO makes observations that span from 82° S to 82° N each day and, for each profile, backscatter coefficient values reported up to ~40 km. The possibility of using CALIPSO for stratospheric aerosol monitoring is demonstrated by the clear observation of the 20 May 2006 eruption of Montserrat in the earliest CALIPSO data in early June as well as by observations showing the 7 October 2006 eruption of Tavurvur (Rabaul). However, the very low aerosol loading within the stratosphere makes routine observations of the stratospheric aerosol far more difficult than relatively dense volcanic plumes. Nonetheless, we found that averaging a complete days worth of nighttime-only data into 5-deg latitude by 1-km vertical bins yields a stratospheric aerosol distribution that is fairly consistent with past measurements by spaceborne instruments. Based on comparisons with 2004 data from the Stratospheric Aerosol and Gas Experiment, the derived values are close to expectation except in the tropics where they are larger by about a factor of 2. The cause of the difference in the tropics is not readily apparent but is most likely related to difficulties in the lidar calibration process currently found in the CALIOP data at tropical latitudes.

pdf/calipso-observations-of-stratospheric-aerosols-a-preliminary-ypzh0ura94.pdf

CALIPSO observations of stratospheric aerosols: a preliminary assessment

After many years of successful and disappointing results, the field of Li–O2 research seems to have reached an equilibrium state. The extensive knowledge that has accrued through advanced analytical studies enables us to delineate the weaknesses of the Li–O2 battery. It is now clear that the instability of the cell components toward extreme conditions existing during cell operation leads to early cell failure as well. One serious challenge is the high oxidation potential applied during the charge process. Redox-mediators may reduce the over-potential and, therefore, improve the efficiency and cyclability of Li–O2 cells. Their use in Li–O2 cells is mandatory. We have previously shown that LiI can indeed behave in such a manner; however, it also promotes the formation of side products during cell operation. We have, therefore, embarked on a comprehensive study of lithium halide salts as electrolytes for use in Li–O2 cells. We examine herein the effect of other components in the cell, such as solvents and contaminants, on the lithium halide salt activity. Based on the electrochemical behavior and the identity of the final cell products under various conditions, we can glean substantial information regarding the detailed operation mechanisms for each specific case. We have concluded that low concentration of LiBr in diglyme solution can improve the cell performance with fewer side effects than LiI. With LiBr, only the desired Li2O2 is formed during discharge. During charge, the bromine redox couple (Br−/Br3−) can reduce the oxidation potential to only 3.5 V. Higher efficiency and better cyclability of cells containing LiBr demonstrate that the electrolyte solution is the key to a successful Li–O2 battery.

Li–O2 cells with LiBr as an electrolyte and a redox mediator

Polyhydroxy fatty acid amide materials are prepared from reactants such as N-methylglucamine and fatty acid esters in the presence of hydroxy solvents. Polyhydroxy fatty acid amide detersive surfactants are secured. By-product and color formation are minimized.

Preparation of polyhydroxy fatty acid amides in the presence of solvents

The Kinetics of the Reduction, in Acid Solution, of Hydrogen Peroxide by Iodide Ion

Relative stabilities of d-glucose-amine derivatives.

Kinetics and mechanism of p-dimethylaminobenzaldehydediphenylamine hydrochloride reaction in the solid state

A Third-order Ionic Reaction without Appreciable Salt Effect.

The Kinetics of the Reduction of Hydrogen Peroxide by the Halides

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