Leaf level emissions of volatile organic compounds (VOC) from some Amazonian and Mediterranean plants

[摘要] Emission inventories defining regional and global biogenic volatile organiccompounds (VOC) emission strengths are needed to determine the impact of VOCon atmospheric chemistry (oxidative capacity) and physics (secondary organicaerosol formation and effects). The aim of this work was to contribute withmeasurements of tree species from the poorly described tropical vegetation indirect comparison with the quite well-investigated, highly heterogeneousemissions from Mediterranean vegetation. VOC emission from sixteen plantspecies from the Mediterranean area were compared with twelve plant speciesfrom different environments of the Amazon basin by an emission screening atleaf level using branch enclosures. Analysis of the volatile organics wasperformed online by a proton-transfer-reaction mass spectrometer (PTR-MS) andoffline by collection on adsorbent tubes and subsequent gas chromatographicanalysis. Isoprene was the most dominant compound emitted followed bymonoterpenes, methanol and acetone. The average loss rates of VOC carbon inrelation to the net CO₂ assimilation were found below 4% andindicating normal unstressed plant behavior. Most of the Mediterraneanspecies emitted a large variety of monoterpenes, whereas only five tropicalspecies were identified as monoterpene emitters exhibiting a quiteconservative emission pattern (α-pinene < limonene < sabinene < ß-pinene). Mediterraneanplants showed additional emissions of sesquiterpenes. In the case ofAmazonian plants no sesquiterpenes were detected. However, missing ofsesquiterpenes may also be due to a lack of sensitivity of the measuringsystems. Furthermore, our screening activities cover only 1% of treespecies of such tropical areas as estimated based on recent biodiversityreports. Methanol emissions, an indicator of growth, were found to be commonin most of the tropical and Mediterranean species. A few species from bothecosystems showed acetone emissions. The observed heterogeneous emissions,including reactive VOC species which are not easily detected by fluxmeasurements, give reason to perform more screening at leaf level and,whenever possible, within the forests under ambient conditions.

[学科分类] 地球化学与岩石