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Hexachlorobenzene in the global environment: emissions, levels, distribution, trends and processes
Jonathan L Barber1, Andrew J Sweetman, Dolf van Wijk
1Department of Environmental Sciences, Institute of Environmental and Natural Sciences, Lancaster University, UK. j.l.barber@lancaster.ac.uk
The Science of the Total Environment
|July 12, 2005
Summary
Hexachlorobenzene (HCB), a model persistent organic pollutant, has shown a downward environmental trend over 20 years. Secondary soil emissions significantly contribute to maintaining current air concentrations.
Area of Science:
- Environmental Chemistry
- Pollutant Fate and Transport
- Global Environmental Monitoring
Background:
- Hexachlorobenzene (HCB) is a persistent organic pollutant (POP) with global distribution.
- Understanding HCB's environmental behavior is crucial for assessing risks and developing mitigation strategies.
Purpose of the Study:
- To compile and analyze data on HCB sources, emissions, levels, and trends.
- To assess the global fate and behavior of HCB, including its dispersion and environmental sinks.
- To investigate the role of primary and secondary sources, particularly soil emissions, in maintaining ambient HCB levels.
Main Methods:
- Compilation and synthesis of existing data on HCB production, emissions, and environmental concentrations.
- Analysis of temporal trends and environmental half-life of HCB across various media.
- Estimation of contemporary HCB environmental burden and emission rates from soils.
Main Results:
- Global HCB production exceeded 100,000 tonnes, with peak atmospheric emissions likely in the 1970s.
- A consistent downward trend in environmental HCB levels has been observed over the past two decades, with an average half-life of approximately 9 years.
- Contemporary environmental burden ranges from 10,000 to 26,000 tonnes, primarily in soils, sediments, and oceans.
- Soil emissions, significant in the past, continue to play a role in maintaining current atmospheric HCB concentrations.
Conclusions:
- HCB has undergone significant global dispersion via air-surface exchange.
- While primary emissions have decreased, secondary emissions from soils are critical for sustaining ambient HCB levels.
- Effective management of HCB requires addressing both historical contamination and ongoing secondary sources.
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