M8 AM Persistent Organic Pollutants
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 337-338
(BAR-1117-828743) Hexachlorobenzene (HCB) in the global environment: emissions, levels, distribution, trends and processes.
Barber, J1, Sweetman, A1, van Wijk, D2, Jones, K, 1 Lancaster University, Lancaster, UK2 Euro Chlor, Brussels, Belgium
ABSTRACT- Hexachlorobenzene (HCB) will be considered as a model persistent organic pollutant. Data on its sources, emissions, environmental levels and distributions and trends have been compiled and will be used to assess its fate and behaviour in the global environment. Global production exceeded 100 000 tonnes and primary emissions to atmosphere probably peaked in the 1970s. There has been a consistent downward trend in the environment over the past 20 years. Consideration will be given as to the extent to which it has undergone repeated air-surface exchange or hopping to become globally dispersed, the balance between primary and secondary sources in maintaining ambient levels, and its ultimate sinks in the environment. Temporal trends of HCB in the environment vary, dependent on time period measured, media studied and study location, but the average half-life from all the studies is 
8 years. Estimates made of the contemporary burden in the environment range between 10 000-26 000 tonnes, and are dominated by the loadings in treated and background soils, sediments and oceans. Estimates of the trends of HCB emissions from treated soils have been derived. At its peak, the amount of HCB emitted from soil to air may have been in the hundreds to thousands of tonnes per year, which would have made it a significant source of HCB to the environment. Whilst the amount of HCB being emitted from contemporary soil is much lower, only a small amount of re-emission of HCB from soil to air is required to maintain contemporary air concentrations under the current primary emission scenario.
Key words: HCB, Global, Model