Release of native and mass labelled PCDD/PCDF from soil heated to simulate bushfires

Soil is an important reservoir of PCDD/PCDF, which can be released when environmental conditions change. Fire is an extreme event that can increase the surface temperatures of soil substantially, yet little is known of the role soil plays in the emission of PCDD/PCDF. Soil containing native PCDD/PCDF was fortified with a mixture of mass labelled PCDD/PCDF and heated between 150 degrees C and 400 degrees C. Both native and mass labelled PCDD/PCDF were released from the soil beyond 200 degrees C. Release of the mass labelled compounds was linearly related to temperature with up to 9% found in the air stream at 400 degrees C. The release of some native PCDD/PCDF was much greater. At 400 degrees C, emission of 1,2,3,7,8-Cl5DD was 300% compared to pre-experimental soil. Emission of PCDD/PCDF from soil during bushfires is a relevant process and may originate from both volatilization and formation via de novo or precursor pathways, or dechlorination. (C) 2012 Elsevier Ltd. All rights reserved.