Litter of mediterranean species as a source of volatile organic compounds

International audienceLeaf litter, at the interface between the soil and the atmosphere, releases Biogenic Volatile Organic Compounds (BVOC) which play an important role both in global atmospheric chemistry and plant ecology. Litter is especially important in the Mediterranean region, where it is produced in high amounts and decomposes slowly. Only leaf litter emissions of two dominant species (Pinus halepensis and Eucalyptus spp.) present in the Mediterranean region have been studied so far. The aim of this study is to characterize (quantitatively and qualitatively) the BVOC emissions (C10–C15) from litter (freshly fallen and non-decomposed leaves) under laboratory conditions. Sixteen species frequently found in the Mediterranean region were considered, nine of which possess terpene storage structures. Results show a large diversity of BVOC (87 compounds detected, terpenes, alkanes, alkenes, aldehydes, ketones, benzenoids), with terpene emission being higher than non-terpenic emission in most of the cases. Species were classified within 3 categories: negligible emitters (e.g. Acer monspessulanum and Quercus ilex, < 0.10 μg.gDM−1.h−1), low emitters (Pinus pinea, Quercus pubescens, 0.1–1.0 μg.gDM−1.h−1) and moderate emitters (Thymus vulgaris, Cotinus coggygria and Pinus halepensis between 1.5 and 4.7 μg.gDM−1.h−1). Litter that possessed terpene storage structures and known to store high terpene concentration did not always release the highest terpene emission rates (e.g. Eucalyptus globulus, Rosmarinus officinalis). Species that do not possess such structures release only non terpenic emissions (e.g. alkanes, aldehydes). Estimation of the potential contribution of P. halepensis and Q. pubescens litter to O3 and secondary organic aerosol (SOA) formation in the atmosphere showed that P. halepensis has a larger potential impact on the global air quality than Q. pubescens. This study will contribute to build future BVOC emissions inventories on leaf litter for their further integration in atmospheric chemistry models