Concentrations and fluxes of biogenic volatile organic compounds above a Mediterranean macchia ecosystem in western Italy

Abstract

Abstract. Emission rates and concentrations of biogenic volatile organic compounds (BVOCs) were measured at a Mediterranean coastal site at Castelporziano, approximately 25 km south-west of Rome, between 7 May and 3 June 2007, as part of the ACCENT-VOCBAS field campaign on biosphere-atmosphere interactions. Concentrations and emission rates were measured using the disjunct eddy covariance (DEC) method utilizing three different proton transfer reaction mass spectrometers (PTR-MS) so allowing a comparison between the instruments. The high resolution data from the PTR-MS instruments considerably enhances the original BEMA measurements of the mid 1990s.Depending on the measurement period, the volume mixing ratios were in the range 1.6-3.5 ppbv for methanol, 0.44-1.3 ppbv for acetaldehyde, 0.96-2.1 ppbv for acetone, 0.10-0.14 ppbv for isoprene, and 0.13-0.30 ppbv for monoterpenes. A diurnal cycle in mixing ratios was apparent with daytime maxima for methanol, acetaldehyde, acetone, and isoprene. The fluxes ranged from 370-440 µg m −2 h −1 for methanol, 180-360 µg m −2 h −1 for acetaldehyde, 180-450 µg m −2 h −1 for acetone, 71-290 µg m −2 h −1 for isoprene, and 240-860 µg m −2 h −1 for monoterpenes. From the measured flux data (7 May-3 June) an average basal emission rate for the Macchia vegetation was calculated

Observations of Diurnal to Weekly Variations of Monoterpene-Dominated Fluxes of Volatile Organic Compounds from Mediterranean Forests: Implications for Regional Modeling

“…Site details and BEF calculation methods concerning previous campaigns have been described previously. 2,4,13 Our recent field campaign was carried out in the mixed oak and pine forest between September and October 2011. The experimental site (41.744N, 12.411E) named "Castello" is primarily dominated by Pinus pinea (stone pine), Quercus ilex (holm oak), and Quercus suber (cork oak).…”

“…Eddy Covariance measurements showed that coastal plant species emitted high levels of BVOC, with fluxes ranging from 370 to 440 μg m −2 h −1 for methanol, 180−360 μg m −2 h −1 for acetaldehyde, 180−450 μg m −2 h −1 for acetone, 71−290 μg m −2 h −1 for isoprene, and 240−860 μg m −2 h −1 for monoterpenes. 13 In this study, we only used BEFs for isoprenoids (142 and 2008 μg m −2 h −1 for sum of isoprene and monoterpenes, respectively, Table 2), since a clear dependence on light or just temperature was not found for oxygenated BVOC, therefore making it uncertain to calculate BEFs based on light and temperature (hereon called G95 L +T, 11 ) or temperature only algorithm (G95 T).…”

“…10 Ten years later, a second experimental campaign took place in spring and summer 2007 on a dune-shrubland experimental site. 2,13 In this campaign, the use of a proton transfer reaction mass spectrometer (PTR-MS 14 ) provided the fast BVOC observations necessary for quasi-real-time flux measurements using Disjunct Eddy Covariance. 15 This allowed for the first time continuous measurements and BEFs calculation at canopy level.…”

Eddy covariance emission and deposition flux measurements using proton transfer reaction – time of flight – mass spectrometry (PTR-TOF-MS): comparison with PTR-MS measured vertical gradients and fluxes

“…Flux calculation for the PTR-MS was based on the continuous flow disjunct eddy covariance method following Davison et al (2009) and described elsewhere in detail (Fares et al, 2012a). For PTR-TOF-MS, we applied the following method to calculate EC fluxes for all identified mass peaks:…”

“…The basic principle of both instruments has been described elsewhere in detail (for PTR-MS: Lindinger et al, 1998;de Gouw and Warneke, 2007; for PTR-TOF-MS: Jordan et al, 2009;Graus et al, 2010). Specifics of instrumental setup for this field experiment are given below.…”