The effect of ozone on the emission of carbonyls from leaves of adult Fagus sylvatica

Under the site conditions of a temperate forest, the exchange of short-chained oxygenated carbonyls (aldehydes, ketones) was assessed from leaves of adult European beech trees. The crowns of the trees were either exposed to an elevated O₃ regime as released by a free-air fumigation system (2 x O₃) or to the unchanged O₃ regime at the site (1 x O₃, 'control'). Daily fluctuations of oxygenated carbonyls were quantified in relation to environmental and physiological factors. In particular, the effect of O₃ on carbonyl exchange was studied. Measurements of leaf gas exchange were performed with a dynamic cuvette system, and carbonyl fluxes were determined using 2,4-dinitrophenylhydrazine (DNPH)-coated silica gel cartridges. Leaves mainly emitted acetaldehyde, formaldehyde and acetone. Acetaldehyde dominated the emissions, amounting up to 100 nmol m^-2 min^-1, followed by formaldehyde (approximately 80 nmol m^-2 min^-1) and acetone (approximately 60 nmol m^-2 min^-1). Carbonyl emissions were highest during midday and significantly lowered at night, irrespective of the O₃ exposure regime. Trees exposed to 2 x O₃ emitted acetaldehyde and acetone at enhanced rates. The findings are of particular significance for future climate change scenarios that assume increased O ₃ levels.