Fluxes of biogenic VOC from Mediterranean vegetation by trap enrichment relaxed eddy accumulation

Results are presented for the application of a modified relaxed eddy accumulation system for the determination of VOC fluxes in the atmosphere (TREA). First, system design, performances and testing against eddy covariance carbon dioxide fluxes are presented. Subsequently, the capability of TREA to discriminate between biogenic and anthropogenic VOC fluxes is discussed with some examples. TREA fluxes are also compared with the major biogenic VOC fluxes calculated with the gradient method and the relative merits and problems of the two techniques are discussed. TREA fluxes for two consecutive days are presented for 18 biogenic compounds. Compounds mostly emitted from the canopy were α-pinene, β-pinene, limonene and trans-β ocimene. The parallel analysis of fluxes determined by TREA and bag enclosures is carried out and discrepancies are discussed in terms of the removal processes of VOC in the atmosphere.