Surface Ocean - Lower Atmosphere Study (SOLAS) Project Integration

Organohalogens

Short-lived brominated and iodinated halocarbons (or organohalogens) from oceanic sources are important halogen-carriers to both the troposphere and stratosphere. Reactive halogen compounds are formed in significant quantities via the breakdown of organohalogens and are critical to oxidising capacity in the troposphere, and significant contributors to ozone depletion in the stratosphere (Law & Sturges et al., 2006; Ko & Poulet et al., 2002). In addition, it has been suggested that biogenic iodocarbon emissions may play a role in new particle formation in the atmosphere (O'Dowd et al., 2002). Methyl iodide (CH3I) is of particular interest from this perspective as it is one of the major means by which iodine gets into the gas phase and into the atmosphere, although other very short-lived iodocarbons may also play a role (Carpenter et al., 2000). Likewise, bromoform (CHBr3) is the dominant source of organic bromine to the troposphere and lower stratosphere (Quack and Wallace, 2003). Recently, the Halogens in the Troposphere (HitT) task team have produced the HitT White Paper, in which they outline how research into halogenated compounds should proceed (see their webpage for more details).

An important aspect of understanding the tropospheric halogen budget is the net flux of volatile organohalogens from the ocean to the atmosphere. Our understanding of the contribution of these important halogen sources to stratospheric and tropospheric chemistry is limited in part by a lack of calibration and comparison of measurements among laboratories. For example, several studies have highlighted a high variability in marine concentrations and atmospheric fluxes of these gases (e.g., Carpenter et al., 2003; Butler et al., 2007). However, it is not always clear how much of the variation results from natural spatial and temporal differences or from analytical dissimilarities or calibration. An advancement of data compatibility will improve the:

  1. understanding of the relative contributions of organic and inorganic forms to the reactive species that drive oxidation;
  2. assessment of the impacts of climate change on atmospheric chemistry;
  3. value and validity of common databases.

Seeking to address this increasingly relevant issue, thirty-two scientists (details) from eight nations gathered in February 2008 at the Novartis Institute in London. This workshop was made possible by the support of the SOLAS International Project Office (IPO), the Natural Environment Research Council (NERC) through UK-SOLAS Knowledge Transfer funds, and the European Science Foundation (ESF) through COST (Cooperation in the field of Scientific and Technical Research) Action 735 funds.

The aim of this workshop was to plan for an international effort that will ensure traceability to common calibration scales for marine measurements of short-lived, volatile halocarbons. The workshop agenda focused on determining the scope of the scientific need, identifying which compounds should be targeted for the greatest scientific benefit, identifying opportunities for beginning calibration and comparison efforts, and prescribing a way forward for improving the comparability of measurements.

Discussions were led by presentations (links to presentation pdfs are in brackets), specifically:

  1. the scientific importance of these observations (Bell and Butler);
  2. the needs of the modeling community in terms of the detection limitations of the instrumentation (von Glasow);
  3. the lack of understanding of the variability of these compounds due to measurement uncertainties (Carpenter and Blake);
  4. methods and potential inter-calibration techniques (Hall and Quack).

More detailed reports of these discussions have been written for the SOLAS Newsletter and for the COST Action 735 management committee.

Anybody who is involved in making marine measurements of short-lived halocarbon compounds (aqueous or gas phase) who would like to be involved in any future inter-calibration effort, please contact the SOLAS Project Integrator.

References
  1. Butler, J.H., King, D.B., Lobert, J.M., Montzka, S.A., Yvon-Lewis, S.A., Hall, B.D., Warwick, N.J., Mondeel, D.J., Aydin, M., Elkins, J.W., 2007. Oceanic distributions and emissions of short-lived halocarbons. Global Biogeochemical Cycles, 21 (1), art. no.-GB1023.
  2. Carpenter, L.J., Malin, G., Liss, P.S., Kupper, F.C., 2000. Novel biogenic iodine-containing trihalomethanes and other short-lived halocarbons in the coastal East Atlantic. Global Biogeochemical Cycles, 14 (4), 1191-1204.
  3. Carpenter, L.J., 2003. Iodine in the marine boundary layer. Chemical Reviews, 103 (12), 4953-4962.
  4. Ko, M.K.W. and Poulet, G. (Lead Authors) Blake, D.R., Boucher, O., Burkholder, J.H., Chin, M., Cox, R.A., George, C., Graf, H.-F., Holton, J.R., Jacob, D.J., Law, K.S., Lawrence, M.G., Midgley, P.M., Seakins, P.W., Shallcross, D.E., Strahan, S.E., Wuebbles, D.J., and Yokouchi, Y. (2002) Very short-lived halogen and sulfur substances. Chapter 2 in Scientific Assessment of Ozone Depletion: 2002 Global Ozone Research and Monitoring Project–Report No. 47, World Meteorological Organization, Geneva, Switzerland, 2003.
  5. Law, K.S. and Sturges, W.T. (Lead Authors) Blake, D.R., Blake, N.J., Burkholder, J.B., Butler, J.H., Cox, R.A., Haynes, P.H., Ko, M.K.W., Kreher, K., Mari, C., Pfeilsticker, K., Plane, J.M.C., Salawitch, R.J., Schiller, C., Sinnhuber, B.-M., von Glasow, R., Warwick, N.J., Wuebbles, D.J., Yvon-Lewis, S.A. (2006) Halogenated very short-lived substances. Chapter 2 in Scientific Assessment of Ozone Depletion: 2006 Global Ozone Research and Monitoring Project–Report No. 50, World Meteorological Organization, Geneva, Switzerland, 2007.
  6. O'Dowd, C.D., Jimenez, J.L., Bahreini, R., Flagan, R.C., Seinfeld, J.H., Hameri, K., Pirjola, L., Kulmala, M., Jennings, S.G., Hoffmann, T., 2002. Marine aerosol formation from biogenic iodine emissions. Nature, 417 (6889), 632-636.
  7. Quack, B., Wallace, D.W.R., 2003. Air-sea flux of bromoform: Controls, rates, and implications. Global Biogeochemical Cycles, 17 (1), art. no.-GB1023.

Implementation Group 1 also examines these other short-lived components:

Dimethyl Sulphide | Alkyl nitrates | Isoprene | Methanol | Ammonia | Aerosol and rain