Field and laboratory based emission factors for PCDD/PCDF/PCB from sugarcane fires

Abstract

The formation of chemicals during combustion processes can be evaluated either in field experiments or during laboratory burns. Measuring emission of trace pollutants such as polychlorinated dibenzo-p-dioxins and furans (PCDD/PCDFs) in field samples is difficult since fires are often short, difficult to access, the smoke escapes usually upwards due to convection and frequently local turbulence carries the smoke away from the sampling equipment. Hence to our knowledge, with the exception of the study by Prange et al. no field data are available on the levels of dioxin-like chemicals in smoke from forest fires and to date no study has measured directly emissions of dioxin-like chemicals from a sugar cane fire under field conditions. As a results of the difficulties associated with high volume field sampling of emissions of trace pollutants from 'outdoor' fires most combustion experiments of trace semivolatiles have been carried out in laboratory experiments where a given amount of biomass was burned under controlled conditions. For dioxin-like chemicals the emission factors that are usually applied for biomass combustion have been derived in such studies, and the few published emission factors for dioxin-like chemicals from agricultural fires are all based on laboratory combustion experiments. This study was part of Australia's National Dioxin Program's Bushfire Study. In this paper we report results of field and laboratory experiments on the emissions of dioxin-like chemicals from sugar cane fires with the aim to: determine emission factors for dioxin-like chemicals from cane fires; evaluate whether cane fires are an important source for dioxin-like chemicals; and to assess whether laboratory combustion chambers and field experiments provide similar emission factors and dioxin emission profiles (i.e. whether laboratory experiments can provide good data to evaluate the emission of dioxin-like chemicals in real field fires).