Abstract
Abstract. For decades, reactive halogen species (RHSs) have been the subject of detailed scientific research due to their influence on the oxidizing capacity of the atmosphere and on the climate. From the RHSs, those containing bromine are of particular interest in the polar troposphere as a result of their link to ozone-depletion events (ODEs) and to the perturbation of the cycle of toxic mercury, for example. Given its remoteness and related limited accessibility compared to the Arctic region, the RHSs in the Antarctic troposphere are still poorly characterized. This work presents ground-based observations of tropospheric BrO from two different Antarctic locations: Marambio Base (64∘13′ S, 56∘37′ W) and Belgrano II Base (77∘52′ S, 34∘7′ W) during the sunlit period of 2015. By means of MAX-DOAS (Multi-axis Differential Optical Absorption Spectroscopy) measurements of BrO performed from the two research sites, the seasonal variation in this reactive trace gas is described along with its vertical and geographical distribution in the Antarctic environment. Results show an overall vertical profile of BrO mixing ratio decreasing with altitude, with a median value of 1.6 pmol mol−1 in the lowest layers of the troposphere. Additionally, observations show that the polar sunrise triggers a geographical heterogeneous increase in bromine content in the Antarctic troposphere yielding a maximum BrO at Marambio (26 pmol mol−1), amounting to 3-fold the values observed at Belgrano at dawn. Data presented herein are combined with previous studies and ancillary data to update and expand our knowledge of the geographical and vertical distribution of BrO in the Antarctic troposphere, revealing Marambio as one of the locations with the highest BrO reported so far in Antarctica. Furthermore, the observations gathered during 2015 serve as a proxy to investigate the budget of reactive bromine (BrOx = Br + BrO) and the bromine-mediated ozone loss rate in the Antarctic troposphere.
Highlights
The importance of the halogens (X = Cl, Br, I) in atmospheric chemistry and climate became clear decades ago after observations of these substances were made in the stratosphere and in the troposphere (e.g., Molina and Rowland, 1974; Farman et al, 1985; Barrie et al, 1988; Oltmans et al, 1989; Fan and Jacob, 1992; Hausmann and Platt, 1994; Solomon, 1999)
The sunlight is focused in a quartz fibre bundle, which is directed into the indoor unit comprising a temperaturestabilized Czerny–Turner monochromator and a CCD camera fully developed by Institute for Aerospace Technology (INTA) based on a Hamamatsu S70311008 sensor, kept at −40 ◦C ± 0.05 ◦C with a temperature control developed and built at INTA
This section is divided into three main parts. It presents the time series of the DOAS measurements and the ancillary observations performed during 2015, offering an overview of the information gathered within the frame of this study
Summary
Yielding the possibility that molecular bromine (Br2) transforms from the aqueous (aq) to the gas phase When this is followed by the photolysis of Br2 into two bromine atoms, an autocatalytic release of bromine is triggered, resulting in an exponential buildup of reactive bromine BrOx (Br + BrO) in the troposphere and the so-called “bromine explosion” events (e.g., Fan and Jacob, 1992; Platt and Lehrer, 1997; Wennberg, 1999; Simpson et al, 2015). Details of the measurement sites and methods are provided below, along with ancillary observations
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