The atmospheric HCHO budget at Dumont d'Urville (East Antarctica): Contribution of photochemical gas‐phase production versus snow emissions

Abstract

HCHO was monitored throughout the year 2009 at the coastal East Antarctic site of Dumont d'Urville (DDU) using Aerolaser AL‐4021 analyzers. The accurate determination of less than 100 pptv required optimization of the analyzers, in particular, to minimize effects of changing ambient temperatures. The impact of station activities and of the presence of large penguin colonies at the site in summer was scrutinized. The obtained contamination‐free record indicates monthly means close to 50 pptv from May to September and a maximum of 200 pptv in January. Zero‐dimensional and 2‐D calculations suggest that in summer, the largest HCHO source is the gas‐phase photochemistry (80%) mainly driven by methane oxidation, which is considerably greater than from snow emissions (20%). The influence of light alkenes, dimethyl sulfide, and halogens remains weak. In winter, snow emissions represent the main HCHO source (70%). These findings are compared to previous studies conducted at the West Antarctic coast. It is shown that in summer the HCHO production from methane chemistry is 3 times more efficient at DDU than at the west coast due to more frequent arrival of oxidant‐rich air masses from inland Antarctica. Halogen chemistry is found to represent a weak HCHO sink at both West and East Antarctica. Compared to DDU, the shallower atmospheric boundary layer and the less efficient gas‐phase production at the west coast make the snow pack the dominant HCHO source (85%) compared to gas‐phase photochemistry (15%) there in summer.

Multi-year record of atmospheric mercury at Dumont d'Urville, East Antarctic coast: continental outflow and oceanic influences

“…A detailed description of the sampling site ("Labo 3") has been given by Preunkert et al (2013) while the climatology of this coastal station has been detailed by König-Langlo et al (1998). The average surface air temperature ranges from −1 • C in January to −17 • C in winter, with a mean annual temperature of −12 • C. The annual mean surface wind speed is 10 m s −1 , with no clear seasonal variations.…”

“…Such local pollution events can be easily identified for instance by the fast decrease of O 3 or increase of HCHO mixing ratios (Legrand et al, 2009;Preunkert et al, 2013). We used a criterion based on wind direction and sudden drops of O 3 mixing ratios to filter the raw data (i.e., collected at 5 min intervals) and discard Hg(0) data impacted by local pollution.…”

Formaldehyde (HCHO) in air, snow, and interstitial air at Concordia (East Antarctic Plateau) in summer

“…Aqueous-phase formaldehyde reacts with the Hantzsch reagent to produce a fluorescent compound that is detected at 510 nm. The working conditions applied to the AL 4021 deployed at Concordia were similar to those applied by Preunkert et al (2013) in their study conducted at the coastal Antarctic site of Dumont D'Urville. In brief, raw data are monitored with a time resolution of 30 s; gas standard calibration and zero determinations are made every 12 and 2 h, respectively.…”

“…In brief, raw data are monitored with a time resolution of 30 s; gas standard calibration and zero determinations are made every 12 and 2 h, respectively. While Preunkert et al (2013) used an air flow of 2 L STP min −1 (leading to a stripping efficiency of 98 %) to obtain accurate HCHO measurements of the low winter levels encountered at DDU, the flow rate was set here when possible (see Sect. 2.3) to 1 L STP min −1 , as recommended by Aerolaser, to reach a stripping efficiency of more than 99 % (M. Haaks, personal communication, 2011).…”

“…This is true in margin regions of Antarctica as concluded on the basis of examinations of the observed HO x budgets at Halley (Bloss et al, 2007) and Dumont d'Urville (DDU; Kukui et al, 2012). At these two coastal sites, the HCHO budget was recently discussed by Preunkert et al (2013), who concluded that, depending on the oxidative character of the local atmosphere and the thickness and stability of the atmospheric boundary layer, either the methane oxidation by OH followed by reaction with NO or snow emissions from neighboring snow-covered regions dominate the HCHO budget. At DDU the largest HCHO source is the methane oxidation in relation to a level of oxidants 3 times higher compared to Halley, and more frequent air mass transport from inland Antarctica there.…”