Atmospheric Environment zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Vol. 22, No. 6, pp. 1179--I 194, 1988. ooo66981/88 %3.W +O.WJ Printed in Great Britain. 8; 1988 Pergamon Prss plc zyxwvut CHLORINE, BROMINE AND IODINE IN ARCTIC AEROSOLS W. T. STURCES* and L. A. BARRIE Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario, Canada M3H 5T4 (First receiz)ed 14 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED May 1987 and inpnal form 16 November 1987) Abstract-Weekly suspended particulate samples were collected at three stations in the Canadian Arctic between 1979 and 1984. The halogens, Cl, Br and I were determined, along with a comprehensive suite of elements and ions. As was previously observed in Alaska, Br was found to peak every year just after the Arctic dawn, reaching concentrations of two orders of magnitude greater than could be explained by marine, automotive and crustal sources. Chlorine concentration correlated closely with that of Na, indicating a marine origin. It was found to be strongly depleted relative to Na during periods of high sulphate concentration. Iodine was found to be enormously enriched relative to seawater by a factor of looCrlO,ooO. The enrichment was least during the early winter when marine aerosol concentrations were at their highest. At locations remote from open oceans I con~ntrations exhibited two annual peaks, one in the spring, and one during the early autumn. No clear correlations with other parameters could be found for these peaks. At locations close to open ocean, concentrations were higher than at the inland sites and did not vary seasonally. Key word index: Bromine, chlorine, iodine, aerosols, halogens, Arctic. INTRODUCTION Over the past two decades, interest in the halogen elements in the atmosphere has grown rapidly, not least because of the key role they play in the chemical and physical processes of the troposphere and strato- sphere. The Planfor Action, published by the Global Tropospheric Chemistry Panel (1984), highlighted the need to understand the behaviour of halogens in the atmosphere. The halogen group includes F, Cl, Br and I. The fifth halogen, astatine, is unstable and has a minute natural abundance, and is therefore not considered here. Fluorine will also not be discussed here. Chlor- ine has perhaps been most widely studied, especially since it was discovered that it has the potential to destroy 0, in the stratosphere (Prather et al., 1984). There is also interest in the apparent volatilization of Cl from marine aerosols (Kritz and Rancher, 1980). Bromine has been the subject of speculation that it may be a yet more powerful agent or synergin than Cl alone for 0, removal (Wofsy zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA et al., 1975). Both Cl and Br may catalyze the oxidation of SO, to SOi- (Clarke and Radojevic, 1983). Mutagenic, and possi- bly carcinogenic properties have been ascribed to some chlorinated and brominated species (Singh et al., 1982). Bromine has been investigated as a possible tracer for leaded aerosol from combustion of leaded gasoline (Harrison and Sturges, 1983). A remarkable springtime pulse of Br has been observed in the Arctic (Berg et aL, 1983; 1984). At Alert a strong inverse * Present address: Institute of Aerosol Science, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K. correlation of particulate Br and lower tropospheric O3 has been observed (Barrie et a[., 1988). It appears that I as well as Br may be active in 0, destruction in the troposphere (Jenkin et al., 1985). Iodine is involved in a large number of atmospheric reactions, and may prove to be a key factor in several aspects of tropospheric chemistry (Chameides and Davis, 1980). Iodine in marine air has been the subject of numerous studies related to its enormous enrich- ment on sea salt particles (Moyers and Duce, 1972). In this paper, 5 yr of routine aerosol chemistry observations (April 1979-June 1984) at three lo- cations in the Canadian Arctic are examined to gain insight into the occurrence of halogens in the northern polar region. EXPERIM ENTA L Weekly aerosol samples were collected on 20 x 25 cm Whatman 41 cellulose filters using hi-volume samplers oper- ated at 26 es ‘. Portions of the filters were analyzed for major ions after extraction in water by ion chromatography (IC) and pH electrodes, and for trace elements by inductively coupled plasma emission spectroscopy (ICP) and instru- mental neutron activation analysis (INAA). Full details of sample collection and analysis are contained in previous publications (Barrie et al., 1981; Barrie and Hoff, 1985). Bromine was measured by both IC (yielding Br-) and by INAA (yielding total Br). The results presented here are for INAA as this was the more sensitive analysis. Br- and Br were strongly correlated. The mean ratio of Br /Br as rep- resented by the slope of a linear regression was 0.68. This may be due to calibration problems. Chlorine and Na were also determined by both IC (yield- ing Na+ Cl-) and INAA (yielding Na, Cl). The agreement between the two methods was excellent (Barrie and Hoff, 1985).The IC results were selected, being the larger data set. 1179