Air quality measurements during prescribed fires

摘要

Concern associated to smoke from forest fires has been increasing during the last past years, and currently, there is a growing awareness that smoke from forest fires can expose individuals and populations to hazardous air pollutants. Notwithstanding these preoccupations, air quality data acquired during forest fires and accompanied with other important information, like meteorology, visibility, fire and combustible characteristics, is still reduced and is not possible to completely evaluate the effects of forest fires on the air quality. The main purpose of this paper is to contribute to a better understanding of forest fires as a source of pollutants to the atmosphere. The Gestosa burning experiments performed in Central Portugal since 1998 till 2001, which involved several teams and covered a very extensive characterization of variables related to the fire behaviour, constituted a great opportunity to analyse and measure air pollutants concentrations during prescribed fires. The similar vegetation cover during all the burning experiments, essentially shrub land, was an important facilitating value to the analysis because vegetation characteristics like biomass were considered as constant. From the first field campaign till the last one it is possible to notice a clear evolution of measurements approaches and techniques aiming to optimise the procedures. In order to improve the air quality knowledge a modelling approach was also adopted, allowing obtaining spatial patterns of pollutants concentrations during the experiments. It was possible to verify that pollutants concentrations, namely nitrogen oxides, particulate matter and carbon monoxide values, were considerably high when measurements were taken close to the burning plots and therefore influenced by the smoke. These levels could be dangerous, mostly for the fire fighters working close to the fire front.