Peroxyacetyl nitrate (PAN) concentrations in the Antarctic troposphere measured during the photochemical experiment at Neumayer (PEAN'99)

Abstract

Because investigations of PAN at higher southern latitudes are very scarce, we measured surface PAN concentrations for the "rst time in Antarctica. During the Photochemical Experiment at Neumayer (PEAN'99) campaign mean surface PAN mixing ratios of 13$7 pptv and maximum values of 48 pptv were found. When these PAN mixing ratios were compared to the sum of NO V and inorganic nitrate they were found to be equal or higher. Low ambient air temperatures and low PAN concentrations caused a slow homogeneous PAN decomposition rate of approximately 5;10\ pptv h\ . These slow decay rates were not su$cient to "rmly establish the simultaneously observed NO V concentrations. In addition, low concentration ratios of [HNO ]/[NO V ] imply that the photochemical production of NO V within the snow pack can in#uence surface NO V mixing ratios in Antarctica. Alternate measurements of PAN mixing ratios at two di!erent heights above the snow surface were performed to derive #uxes between the lower troposphere and the underlying snow pack using calculated friction velocities. Most of the concentration di!erences were below the precision of the measurements. Therefore, only an upper limit for the PAN #ux of $1;10 molecules m\ s\ without a predominant direction can be estimated. However, PAN #uxes below this limit can still in#uence both the transfer of nitrogen compounds between atmosphere and ice, and the PAN budget in higher southern latitudes.

Iodine monoxide in the Antarctic snowpack

“…This diurnal variation is similar to predictions from photochemical model calculations (Vogt et al, 1999), where the IO minimum at noon is caused by the reaction of HO 2 with IO to HOI, and the am/pm asymmetry by a built-up of I 2 O 2 by IO self reaction during the day. However, HO 2 concentrations at the West Antarctic coast are about a factor of five smaller than modelled by Vogt et al for mid-latitude conditions, and NO 2 concentrations around 3 ppt measured in the boundary layer at Neumayer Jacobi et al, 2000) are likely to be too small to cause a significant formation of IONO 2 during the day. Another possible explanation for the noon minimum of IO above the instrument is a break-up of the boundary layer and a mixing in of free tropospheric air low in IO.…”

Boundary layer physics over snow and ice

“…This manual discusses the present optimum instrument designs to deploy over snow, such as preferring propeller-vane wind instruments over cup anemometers. The AWS will only provide limited information on the structure of the boundary layer, the data being used as if standard meteorological data were available (Jacobi et al, 2000;Jones et al, 2001). u * can be estimated from wind speed, assuming neutral stratification and a known or estimated roughness length.…”

“…Several of note are: chemistry near the ground. A similar study for Peroxyacetyl nitrate (PAN) during PEAN'99 highlighted the benefits of having co-located in situ turbulence sensors during boundary layer chemistry campaigns (Jacobi et al, 2000).…”

Characterising terrestrial influences on Antarctic air masses using Radon-222 measurements at King George Island

“…Steig and Orsi, 2013;Heffernan, 2012;Pereira et al, 2006), there is growing interest in quantifying the magnitude and source regions of pollutants affecting this pristine region (e.g. Jones et al, 2008;Pereira et al, 2004;Jacobi et al, 2000;Berresheim and Eisele, 1998). In turn, anthropogenically driven changes to Antarctic climate and ecosystems have the potential to feedback to the global climate system, due to the significant role that Antarctica plays in largescale atmospheric and oceanic circulation patterns.…”