Reactive and organic halogen species in three different European coastal environments

Abstract

Abstract. We present results of three field campaigns using active longpath DOAS (Differential Optical Absorption Spectroscopy) for the study of reactive halogen species (RHS) BrO, IO, OIO and I 2 . Two recent field campaigns took place in Spring 2002 in Dagebüll at the German North Sea Coast and in Spring 2003 in Lilia at the French Atlantic Coast of Brittany. In addition, data from a campaign in Mace Head, Ireland in 1998 was partly re-evaluated. During the recent field campaigns volatile halogenated organic compounds (VHOCs) were determined by a capillary gas chromatograph coupled with an electron capture detector and an inductively coupled plasma mass spectrometer (GC/ECD-ICPMS) in air and water. Due to the inhomogeneous distribution of macroalgae at the German North Sea Coast we found a clear connection between elevated levels of VHOCs and the appearance of macroalgae. Extraordinarily high concentrations of several VHOCs, especially CH 3 I and CH 3 Br of up to 1830 pptv and 875 pptv, respectively, were observed at the coast of Brittany, demonstrating the outstanding level of bioactivity there. We found CH 2 I 2 at levels of up to 20 pptv, and a clear anti-correlation with the appearance of IO. The IO mixing ratio reached up to 7.7±0.5 ppt (pmol/mol) during the day, in reasonable agreement with model studies designed to represent the meteorological and chemical conditions in Brittany. For the two recent campaigns the DOAS spectra were evaluated for BrO, OIO and I 2 , but none of these species could be clearly identified (average detection limits around 2 ppt, 3 ppt, 20 ppt, resp., significantly higher in individual cases). Only in the Mace Head spectra evidence was found for the presence of OIO. Since macroalgae under oxidative stress are suggested to be a further source for I 2 in the marine boundary layer, we re-analyzed spectra in the 500-600 nm range taken during the 1998 PARFORCE campaign in Mace Head, Ireland, Correspondence to: C. Peters (christina.peters@iup.uni-heidelberg.de) which had not previously been analyzed for I 2 . We identified molecular iodine above the detection limit (∼20 ppt), with peak mixing ratios of 61±12 ppt. Since I 2 was undetectable during the Brittany campaign, we suggest that iodine may not be released into the atmosphere by macroalgae in general, but only by a special type of the laminaria species under oxidative stress. Only during periods of extraordinarily low water (spring-tide), the plant is exposed to ambient air and may release gaseous iodine in some way to the atmosphere. The results of our re-analysis of spectra from the PARFORCE campaign in 1998 support this theory. Hence, we feel that we can provide an explanation for the different I 2 levels in Brittany and Mace Head.

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

“…Butz et al: Inorganic iodine in the tropical UT/LS observed regularly in the form of IO radicals in the lower troposphere with concentrations of several ppt (e.g. Frieß et al, 2001;Peters et al, 2005;Zingler and Platt, 2005;SaizLopez et al, 2006SaizLopez et al, , 2007bRead et al, 2008). Only recently, space-borne observations confirmed enhanced levels of IO near coastal Antarctica (Saiz-Lopez et al, 2007a;Schönhardt et al, 2008).…”

“…Measurements in marine boundary layer air indicate that background CH 3 I concentrations range between 0.1 ppt and 2 ppt (Butler et al, 2007;Yokouchi et al, 2008) with higher values reported from North Atlantic coastal source regions (e.g. Peters et al, 2005). Following emission by certain types of algae, molecular iodine (I 2 ) has been identified as an inorganic source of IO x in the coastal boundary layer (e.g.…”

“…The approach is based on balloon-borne solar absorption spectroscopy as presented by Bösch et al (2003). From spectra recorded in the visible spectral range by a long-path DOAS setup comparable to the one described in Peters et al (2005), we infer IO abundances along a 29 km absorption path in the marine boundary layer between the mainland and an island in the bay of Sao Marcos. IO concentrations up to (0.82±0.31) ppt (Fig.…”

Impacts of bromine and iodine chemistry on tropospheric OH and HO<sub>2</sub>: comparing observations with box and global model perspectives

“…Observations of BrO and IO radicals within the MBL have demonstrated widespread impacts on atmospheric composition and chemistry (Alicke et al, 1999;Sander et al, 2003;Leser et al, 2003;Saiz-Lopez and Plane, 2004;SaizLopez et al, 2004SaizLopez et al, , 2006Peters et al, 2005;Whalley et al, 2007;Mahajan et al, 2010a;Commane et al, 2011;Dix et al, 2013;Gomez Martin et al, 2013;Le Breton et al, 2017), including significant effects on HO x concentrations and on the HO 2 : OH ratio in coastal and marine locations (Bloss et al, 2005a(Bloss et al, , 2010Sommariva et al, 2006;Kanaya et al, 2007;Whalley et al, 2010).…”

Understanding the origin of clouds

“…[15] Only limited work at other sites that support Laminaria digitata has been performed and have only assessed precursor gases. [23] The work at Cape Grim indicates that further work is required at other locations and on other macro-algae to better understand the global importance of the processes identified at Mace Head.…”