An international team of atmospheric chemists has produced the first gridded global inventory of reactive chlorine emissions to the atmosphere. Reactive chlorines are of interest because some of these compounds contribute to the destruction of stratospheric ozone, some are toxic to humans at high-dose exposures, and others are carcinogenic at chronic, lower-dose exposures.
This collaborative study involved 20 researchers from academia, government and industry working in six countries over three years. The research was conducted under the auspices of the International Global Atmospheric Chemistry Programme's Global Emissions Inventory Activity. Results were published in a seven-article special section of the April 20,1999, issue of the Journal of Geophysical Research.
"This work provides an objective benchmark for assessing our current understanding of the global chlorine cycle and for investigating the potential environmental implications of future changes in chlorine emissions," says William C. Keene, research associate professor of environmental sciences at the University of Virginia. "The inventory should facilitate informed public policy decisions for the regulation of chlorine emissions."
Keene was a principal investigator for the project and served as a lead organizer, manager and director for the planning and execution of the study. The project is similar to the global carbon emissions inventory conducted several years ago to investigate natural and human influences on the atmospheric carbon quantity. That benchmark study was central to thediscussions leading to the recent Kyoto Protocols, a set of international guidelines for regulating future carbon emissions.
"We anticipate that the chlorine emissions study may be employed in a similar manner," Keene says, "although our results are associated with greater uncertainty because multiple compounds are involved and the underlying observational data are more limited."
Individual working groups characterized emissions of 10 specific chlorine-containing compounds from each of four different classes of source types: oceanic and terrestrial biogenic emissions; sea-salt production and dechlorination; biomass burning; and exclusively human-made emissions from industrial sources and coal burning. Emissions of those compounds for which sufficient information was available were gridded over the earth’s surface on a one-degree by one-degree scale. The individual inventories for each compound were then integrated across source types and the relative importance of natural and human-caused sources differentiated. The result is a set of "known" inventories of specific chlorine-containing compounds as a function of source type that can be applied in various types of further investigations.
"We anticipate that these results will provide critical input data for future modeling studies, as well as a useful perspective in planning future measurement programs," Keene says in the preface to the seven papers published in the journal.
Major financial support for the project was provided by the Chemical Manufacturers Association via the Chlorine Chemistry Council and from the European Chemical Industry via Euro Chlor (a federation of the European chlorine industry). Individual investigators also received support from other agencies and institutions, including the U.S. National Science Foundation and the Atmospheric Environment Service, Canada. ###
For more information about this study, see the website for the Reactive Chlorine Emissions Inventory at: http://blueskies.sprl.umich.edu/geia/rcei.
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