On Biogenic Halocarbons in Antarctic Waters Erik Mattsson Akademisk avhandling för filosofie doktorsexamen i Naturvetenskap, inriktning kemi, som med tillstånd från Naturvetenskapliga fakulteten kommer att offentligt försvaras den 8 november 2013 kl 10.00 i KC, Institutionen för kemi och molekylärbiologi, Kemigården 4, Göteborg. Department of Chemistry and Molecular Biology University of Gothenburg Gothenburg 2013 Cover illustration: Bromoform concentration in the surface waters of the Southern Ocean Erik Mattsson Department of Chemistry and Molecular Biology University of Gothenburg SE-412 96 Göteborg Sweden On Biogenic Halocarbons in Antarctic Waters © Erik Mattsson 2013 [email protected] ISBN 978-91-628-8795-7 Available online at: http://hdl.handle.net/2077/34086 Till Charlott, Esther och Sigrid Printed in Gothenburg, Sweden 2013 Printed by Ale Tryckteam AB Cover illustration: Bromoform concentration in the surface waters of the Southern Ocean Erik Mattsson Department of Chemistry and Molecular Biology University of Gothenburg SE-412 96 Göteborg Sweden On Biogenic Halocarbons in Antarctic Waters © Erik Mattsson 2013 [email protected] ISBN 978-91-628-8795-7 Available online at: http://hdl.handle.net/2077/34086 Till Charlott, Esther och Sigrid Printed in Gothenburg, Sweden 2013 Printed by Ale Tryckteam AB Abstract Little is known regarding the distribution of naturally produced volatile halogenated organic compounds, halocarbons, in Antarctic waters and the contribution of these waters to the global atmospheric load of halogens. In the atmosphere, halocarbons are degraded by photolysis, and form reactive halogen radicals. These radicals are thereafter involved in the catalytic degradation of ozone and formation of aerosols. Ozone degradation mainly occurs over the poles, and the process is most prominent during the springtime in the stratosphere at the South Pole. Biogenic halocarbons are formed by algae during photosynthesis. As such, the formation of halocarbons takes place in all oceans, but with large spatial and temporal variations. To determine the source strength of the oceans, it is essential to establish reliable estimates of the air-sea exchange, as well as production and degradation rates of halocarbons in the assessment of the role the oceans play in the destruction of ozone. In this work, the major aim has been to broaden the knowledge of the distribution of biogenic halocarbons in the Pacific sector of the Southern. Studies of the relationship between halocarbon distributions and biophysical variables indicated sea ice as the main regulating factor. The production and degradation rates in sea ice were therefore established, and the net production was found to be able to sustain concentration gradients in the ice. High resolution measurements of halocarbons in surface water and air were conducted to establish the air-sea exchange of halocarbons, and the results showed that the cold waters acted as a sink (100 days of minimum sea ice extent), with an uptake of 0.04 Gmol Br for bromoform, in contrast to earlier findings. A three year study during the austral summer in the Amundsen Sea was conducted, and the distributions and fluxes of halocarbons were found to be consistent. A novel approach utilising transposed- orthogonal projections to latent structures T-OPLS, indicated that biogenic halocarbons could be used to study the circulation of water masses on the shelf in the Amundsen Sea. Keywords: Volatile biogenic halocarbons, Antarctica, Southern Ocean, Sea ice, snow, air-sea exchange ISBN: 978-91-628-8795-7 v Abstract Little is known regarding the distribution of naturally produced volatile halogenated organic compounds, halocarbons, in Antarctic waters and the contribution of these waters to the global atmospheric load of halogens. In the atmosphere, halocarbons are degraded by photolysis, and form reactive halogen radicals. These radicals are thereafter involved in the catalytic degradation of ozone and formation of aerosols. Ozone degradation mainly occurs over the poles, and the process is most prominent during the springtime in the stratosphere at the South Pole. Biogenic halocarbons are formed by algae during photosynthesis. As such, the formation of halocarbons takes place in all oceans, but with large spatial and temporal variations. To determine the source strength of the oceans, it is essential to establish reliable estimates of the air-sea exchange, as well as production and degradation rates of halocarbons in the assessment of the role the oceans play in the destruction of ozone. In this work, the major aim has been to broaden the knowledge of the distribution of biogenic halocarbons in the Pacific sector of the Southern. Studies of the relationship between halocarbon distributions and biophysical variables indicated sea ice as the main regulating factor. The production and degradation rates in sea ice were therefore established, and the net production was found to be able to sustain concentration gradients in the ice. High resolution measurements of halocarbons in surface water and air were conducted to establish the air-sea exchange of halocarbons, and the results showed that the cold waters acted as a sink (100 days of minimum sea ice extent), with an uptake of 0.04 Gmol Br for bromoform, in contrast to earlier findings. A three year study during the austral summer in the Amundsen Sea was conducted, and the distributions and fluxes of halocarbons were found to be consistent. A novel approach utilising transposed- orthogonal projections to latent structures T-OPLS, indicated that biogenic halocarbons could be used to study the circulation of water masses on the shelf in the Amundsen Sea. Keywords: Volatile biogenic halocarbons, Antarctica, Southern Ocean, Sea ice, snow, air-sea exchange ISBN: 978-91-628-8795-7 v Populärvetenskaplig sammanfattning Flyktiga halogenerade kolväten, även kallade halokarboner, återfinns i både haven och atmosfären. De vanligaste naturligt bildade halokarbonerna innehåller brom eller jod medan de antropogena oftast innehåller fluor eller klor. De största naturliga källorna av dessa ämnen är haven. Här bildas halokarboner av tång och växtplankton när de försöker göra sig av med överskott av väteperoxid som bildas under fotosyntesen. Vad som påverkar produktionen av halokarboner är fortfarande oklart. Den högsta produktionen av halokarboner återfinns i kustnära områden där tång frodas, men eftersom det öppna havet är så mycket större till ytan är även detta en betydelsefull källa. Halokarboner som uppehåller sig i ytan kan övergå till atmosfären, eftersom de är flyktiga. Väl där kan de delta i ozonnedbrytande processer, när de utsatta för solljus bildar reaktiva radikaler. Dessa processer är mest påtagliga över polerna, där ozonhalten på sommarhalvåret minskar drastiskt i halt. Polarområdena är också viktiga att studera ur ett klimatologiskt perspektiv, eftersom de är känsliga för den globala uppvärmningen som sker på jorden, exempelvis har en ökad avsmältning av glaciärerna i Antarktis observerats. Halokarboner är förhållandevis lite undersökt i Antarktis jämfört med de tempererade haven. Under tre år med den svenska isbrytaren Oden genomfördes mätningar av halokarboner i havsis, atmosfär och hav i Amundsen och Ross haven. Resultaten från mätningarna i havsisen visade att isen är en betydelsefull källa av halokarboner till atmosfären och denna borde inkluderas i framtida globala budgetar av halokarboner. Luft och havsvattenmätningar i de olika regionerna visade att dessa vatten kan agera som en sänka för halokarboner i atmosfären, vilket var en viktig upptäckt då dessa vatten tidigare har ansetts endast vara en källa av halokarboner till atmosfären.. vi Part A. Table of contents Part B. List of Publications 1 RATIONALE ................................................................................................. 1  This thesis is based on the following studies, referred to in the text by their Roman numerals. 2 BACKGROUND ............................................................................................. 3  3 SOUTHERN OCEAN ...................................................................................... 6  I. Mattson, E., Karlsson, A. Smith, W.O., and Abrahamsson, 3.1 Overview ............................................................................................... 6  K. (2012) The relationship between biophysical variables and halocarbon distribution in the waters of the Amundsen 3.2 Polynias................................................................................................. 7  and Ross seas, Antarctica, Marine Chemistry, 141-142, 1-9, 3.3 Ross Sea ................................................................................................ 8  doi:10.1016/j.marchem.2012.07.002 3.4 Amundsen Sea .................................................................................... 11  II. Mattsson, E., Karlsson, A., and Abrahamsson, K. (2013) 4. FORMATION OF HALOCARBONS ............................................................... 13  Regional sinks of bromoform in the Southern Ocean, 4.1 Enzymatic formation .......................................................................... 13  Geophysical Research Letters, Vol. 40, 1-6, 4.2 Correlation to pigments ...................................................................... 15  doi:10.1002/grl.50783 4.3 Abiotic formation ................................................................................ 16  III. Mattsson, E., Karlsson, A. Granfors, A. M. Josefson and 5. DEGRADATION AND TRANSFORMATION OF HALOCARBONS .................... 17  Abrahamsson, K. Inter-annual variation of halocarbons in the Amundsen and Ross Sea, Manuscript 5.1 Substitution of halides ........................................................................ 17  5.2 Hydrolysis .......................................................................................... 19  IV. Granfors, A., Karlsson, A. Mattsson, E., Smith, W.O., andAbrahamsson, K. (2013) Contribution of sea ice in the 5.3 Photolysis ........................................................................................... 19  Southern Ocean to the cycling of volatile halogenated 5.4 Microbial degradation ......................................................................... 20  organic compounds, Geophysical Research Letters, Vol. 40, 6. AIR-SEA FLUX .......................................................................................... 22  1-6, doi:10.1002/grl.50777 7. SEA ICE ..................................................................................................... 27  Contribution Report 8. ANALYTICAL METHODOLOGY .................................................................. 32  Paper I: Responsible for planning, conducting experiments, 8.1 Sampling and storage .......................................................................... 32  interpretation and writing 8.2 Pre-concentration techniques .............................................................. 32  Paper II: Responsible for planning, conducting experiments, 8.3 Quantification ..................................................................................... 34  interpretation and writing 9. CONCLUDING REMARKS ........................................................................... 36  10. OUTLOOK ............................................................................................... 37  PaperIII: Participated in planning, conducting experiments, interpretation and writing ACKNOWLEDGEMENT .................................................................................... 38  No participation on experimental part of OSO2010. REFERENCES .................................................................................................. 39  Paper IV: Participated in planning and interpretation viii ix Part B. List of Publications This thesis is based on the following studies, referred to in the text by their Roman numerals. I. Mattson, E., Karlsson, A. Smith, W.O., and Abrahamsson, K. (2012) The relationship between biophysical variables and halocarbon distribution in the waters of the Amundsen and Ross seas, Antarctica, Marine Chemistry, 141-142, 1-9, doi:10.1016/j.marchem.2012.07.002 II. Mattsson, E., Karlsson, A., and Abrahamsson, K. (2013) Regional sinks of bromoform in the Southern Ocean, Geophysical Research Letters, Vol. 40, 1-6, doi:10.1002/grl.50783 III. Mattsson, E., Karlsson, A. Granfors, A. M. Josefson and Abrahamsson, K. Inter-annual variation of halocarbons in the Amundsen and Ross Sea, Manuscript IV. Granfors, A., Karlsson, A. Mattsson, E., Smith, W.O., and Abrahamsson, K. (2013) Contribution of sea ice in the Southern Ocean to the cycling of volatile halogenated organic compounds, Geophysical Research Letters, Vol. 40, 1-6, doi:10.1002/grl.50777 Contribution Report Paper I: Responsible for planning, conducting experiments, interpretation and writing Paper II: Responsible for planning, conducting experiments, interpretation and writing Paper III: Participated in planning, conducting experiments, interpretation and writing No participation on experimental part of OSO2010. Paper IV: Participated in planning and interpretation ix Abbreviations 1 Rationale AASW Antarctic Surface Water Volatile halogenated organic compounds, VHOCs, or more commonly, CDW Circumpolar Deep Water halocarbons, have two independent sources; human industrial activities and biogenic processes in the oceans. Halocarbons are defined as hydrocarbons mCDW modified Circumpolar Deep Water with one or several covalently bonded halogens, e.g. fluorine, chlorine, AABW Antarctic Bottom Water bromine or iodine. When halocarbons are released into the atmosphere, they SW Shelf Water are subjected to photolysis, producing reactive halogen radicals, which ISW Ice Shelf Water produces reactive halogen free radicals. These free radicals are involved in ACC Antarctic circumpolar current ozone depletion both in the troposphere and in the stratosphere. NADW North Atlantic Deep Water The largest source of biogenic halocarbons on Earth is the oceans. The role of AIW Antarctic Intermediate Water these compounds in the degradation of ozone has been investigated ever since RIS Ross Ice Shelf Lovelock [1973] found that marine algae could produce CH I. The biogenic 3 ECD Electron capture detector compounds include a number of chlorinated, brominated, and iodinated GC Gas chromatograph compounds, where bromoform is the single largest contributor to organo- MS Mass spectrometer bromine in the atmosphere [WMO, 2010]. There are still uncertainties regarding the global circulation of these compounds even if the mechanisms behind the biological production of halocarbons have been extensively studied, and algal production rates have been established. For instance, the oceanic source of CHBr3 based on algal production has been estimated to be  3 Gmol yr-1, and the emission of CHBr to the atmosphere 10 Gmol yr-1, 3 which indicates a discrepancy of  7 Gmol yr-1[Quack and Wallace, 2003]. Parameters that control the biological production, geographical distribution, seasonal variation, the air-sea flux, and the degradation of halocarbons are all factors that need to be further investigated to minimize the discrepancies in the global models of source strengths and fluxes. Uncertainties can also be found in the models due to the under-sampling of the oceans, with respect to geographical, temporal and seasonal coverage. Data from tropical regions are abundant and covers all seasons, whereas investigations of Polar regions are scarce, and usually conducted during the summer. The aim of this work has been to broaden the knowledge of biogenic halocarbons (Table 1) in the waters surrounding the Antarctica, with special emphasis on the Bellingshausen, Amundsen, and Ross Seas. To understand the driving forces of the halocarbon distribution, the coupling to biogeophysical parameters and sea ice have been investigated (Papers I and IV). The removal of halocarbons from the mixed layer due to degradation and downward mixing was investigated through studies of the water column (Paper III). x 1