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Previous Antarctic summer campaigns have shown unexpectedly high levels of oxidants in the lower atmosphere of the continental plateau as well as at coastal regions, with atmospheric hydroxyl radical (OH) concentrations up to 4 × 106 cm−3. Such high reactivity of the summer Antarctic boundary layer results in part from the emissions of nitrogen oxides (NOx ≡ NO + NO2) produced during photo-denitrification of the snowpack, but its underlying mechanisms are not yet fully understood as some of the chemical species involved (NO2, in particular) have not yet been measured directly and accurately. To overcome this crucial lack of information, newly developed optical instruments based on absorption spectroscopy (incoherent broadband cavity enhanced absorption spectroscopy or IBBCEAS) were deployed for the first time at Dome C (−75.10 lat., 123.33 long., 3,233 m a.s.l) during the 2019–2020 summer campaign to refine uncertainties in snow-air-radiation interaction. These instruments directly measure NO2 with a detection limit of 30 pptv (parts per trillion by volume or 10–12 mol mol−1) (3σ). We performed two sets of measurements in December 2019 (4th to 9th) and January 2020 (16th to 25th) to capture the early and late photolytic season, respectively. Late in the season, the daily averaged NO2 : NO ratio (0.4 ± 0.4) matches that expected for photochemical equilibrium through Leighton’s extended relationship involving ROx (0.6 ± 0.3). In December, however, we observe a daily averaged NO2 : NO ratio of 1.3 ± 1.1, which is approximately twice the daily ratio of 0.7 ± 0.4 calculated for Leighton equilibrium. This suggests that more NO2 is produced from the snowpack early in the photolytic season (December 4th to 9th) possibly due to stronger UV irradiance caused by a smaller solar zenith angle near the solstice. Such a high sensitivity of the NO2 : NO ratio to the sun’s position is of importance for consideration in atmospheric chemistry models.

International audience; To fully decipher the role of nitrate photolysis on the atmospheric oxidative capacity in snow-covered regions, NOx flux must be determined with more precision than existing estimates. Here, we introduce a method based on dynamic flux chamber measurements for evaluating the NOx production by photolysis of snowpack nitrate in Antarctica. Flux chamber experiments were conducted for the first time in Antarctica, at the French-Italian station Concordia, Dome C (75°06'S, 123°20’E, 3233 m a.s.l) during the 2019–2020 summer campaign. Measurements were gathered with several snow samples of different ages ranging from newly formed drifted snow to 6-year-old firn. Contrary to existing literature expectations, the daily average photolysis rate coefficient, urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0007, did not significantly vary between differently aged snow samples, suggesting that the photolabile nitrate in snow behaves as a single-family source with common photochemical properties, where a urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0008 = (2.37 urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0009 0.35) × 10−8 s−1 (1urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0011) has been calculated from December 10th 2019 to January 7th 2020. At Dome C summer daily average NOx flux, urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0015, based on measured NOx production rates was estimated to be (4.3 urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0017 1.2) × 108 molecules cm−2 s−1, which is 1.5–7 times less than the net NOx flux observed previously above snow at Dome C using the gradient flux method. Using these results, we extrapolated an annual continental snow sourced NOx budget of 0.017 urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0022 0.003 Tgurn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0023N y−1, urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-00252 times the nitrogen budget, (N-budget), of the stratospheric denitrification previously estimated for Antarctica. These quantifications of nitrate photolysis using flux chamber experiments provide a road-map toward a new parameterization of the urn:x-wiley:2169897X:media:jgrd57323:jgrd57323-math-0026 product that can improve future global and regional models of atmospheric chemistry.

We assessed the impact of chest CT body composition parameters on outcomes and disease severity at hospital presentation of COVID-19 patients, focusing also on the possible mediation of body composition in the relationship between age and death in these patients. Chest CT scans performed at hospital presentation by consecutive COVID-19 patients (02/27/2020-03/13/2020) were retrospectively reviewed to obtain pectoralis muscle density and total, visceral, and intermuscular adipose tissue areas (TAT, VAT, IMAT) at the level of T7-T8 vertebrae. Primary outcomes were: hospitalization, mechanical ventilation (MV) and/or death, death alone. Secondary outcomes were: C-reactive protein (CRP), oxygen saturation (SO2), CT disease extension at hospital presentation. The mediation of body composition in the effect of age on death was explored. Of the 318 patients included in the study (median age 65.7 years, females 37.7%), 205 (64.5%) were hospitalized, 68 (21.4%) needed MV, and 58 (18.2%) died. Increased muscle density was a protective factor while increased TAT, VAT, and IMAT were risk factors for hospitalization and MV/death. All these parameters except TAT had borderline effects on death alone. All parameters were associated with SO2 and extension of lung parenchymal involvement at CT; VAT was associated with CRP. Approximately 3% of the effect of age on death was mediated by decreased muscle density. In conclusion, low muscle quality and ectopic fat accumulation were associated with COVID-19 outcomes, VAT was associated with baseline inflammation. Low muscle quality partly mediated the effect of age on mortality.

Supplemental material, sj-pdf-1-hsr-10.1177_13558196211008942 for The effects of centralizing cancer surgery on postoperative mortality: A systematic review and meta-analysis by Roberto Grilli, Federica Violi, Maria Chiara Bassi and Massimiliano Marino in Journal of Health Services Research & Policy