The effect of forest fires in emissions of biogenic volatile organic compounds and windblown dust over urban areas

Abstract

This study examines the impact of forest fires on natural biogenic volatile organic compounds (BVOCs) and windblown dust emissions over urban areas; specifically over the Athens larger urban zone for the reference year 2008. The area spans a continuum of urban–suburban–wild lands and suffers air quality problems with respect to particulate matter (PM) which are frequently exacerbated during the summer due also to forest fire events. Although the anthropogenic, natural and forest fire emissions in the area have been well documented in the past, the indirect effect of forest fires on natural emissions has not been estimated. A brief description of the area and the history of forest fires events during the period 2000–2008 are presented together with an emission inventory for particulate matter (PM2.5 and PM2.5–10) and non-methane VOC (NMVOC), precursor to PM, from anthropogenic and natural sources for the reference year 2008. The effect of large forest fires (over 40 ha) during the period 2000–2008 on natural emissions is examined with respect also to the spatial and temporal distribution and their relative contribution to total emissions over the area. Moreover, the effect of several parameters and assumptions used in natural emissions calculations pre and post-fire events is discussed. The results indicate that there is a trade-off between fire effects that can result in an increase in PM10 windblown dust emissions but decrease of BVOCs emissions due to vegetation reduction. The changes in natural BVOCs and PM10 emissions over the selected area are rather small, specifically 3.5% and 1.7%, respectively. Changes in the relative contribution of natural to total PM10 and NMVOC emissions in the area due to forest fires was also found small, approximately 0.5% and 0.7%, respectively. The contribution of anthropogenic emissions appears to dramatically outweigh the potential effects on air quality from natural emissions and their changes due to large forest fires. Therefore, more attention should be given to mitigating the anthropogenic emissions in the area for the purposes of promoting air quality.