A Simple Model for Estimating Emissions of Volatile Organic Compounds from Grass and Cut Grass in Urban Airsheds and Its Application to Two Australian Cities

Abstract

Grass, and particularly cut grass, recently has been shown to emit significant amounts of volatile organic compounds (VOCs) into the atmosphere.Some components of these emissions are highly reactive and may contribute to photochemical smog in urban areas.A simple model for estimating the VOC emissions from grass and for grass cutting that allows these processes to be included in urban/regional emissions inventories is presented here.Using previous work and recent literature values, estimates are made of these biogenic volatile organic compound (BVOC) emissions for two typical urban airsheds, those including the cities of Sydney and Melbourne in Australia.Grass and cut grass could contribute 2% for Sydney and 3% for Melbourne of the total VOCs emitted into these urban atmospheres annually.These contributions could rise to 4 and 5%, respectively, during the weekends of the summer growing season and, thus, could contribute to weekday/weekend ozone differences.It is recommended that the emissions of BVOCs from grass and cut grass be included in urban and global emissions inventories so that more accurate predictions of smog chemistry can be determined. IMPLICATIONSThe C 6 compounds emitted from cut grass presently are omitted from most inventories of emissions of BVOCs.Estimates indicate that this may constitute a significant omission.These compounds are highly reactive in the atmosphere, and, in the presence of nitrogen oxides, may make a significant contribution to the formation of photochemical smog and secondary organic aerosol in urban areas.The increased incidence of grass cutting on weekends means that these emissions (and the associated lawnmower emissions) may contribute to weekday/weekend ozone differences.