Acton W.J.F.,Lancaster University |
Schallhart S.,University of Helsinki |
Langford B.,UK Center for Ecology and Hydrology |
Valach A.,Lancaster University |
And 11 more authors.
Atmospheric Chemistry and Physics
This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone Cmethacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton-transfer-reaction mass spectrometer (PTR-MS) and a proton-transfer-reaction timeof- flight mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (using PTR-MS) and eddy covariance (using PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean daytime flux of 1.9 mg m-2 h-1. Mixing ratios, recorded 4m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28-day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTRToF- MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m-2 h-1 was calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) isoprene emission algorithms (Guenther et al., 2006). A detailed tree-species distribution map for the site enabled the leaf-level emission of isoprene and monoterpenes recorded using gas-chromatography mass spectrometry (GC-MS) to be scaled up to produce a bottom-up canopy-scale flux. This was compared with the top-down canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant-species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates. © Author(s) 2016. Source
Taglienti A.,Research Center for Soil Plant System |
Ritota M.,Research Center for Soil Plant System |
Cozzolino S.,Research Center for Soil Plant System |
Sequi P.,Research Center for Soil Plant System |
And 3 more authors.
Magnetic Resonance Imaging (MRI) is a technique known mainly for its medical and diagnostic applications and is capable of producing non-destructively high resolution images of any internal section of the analysed sample. MRI has been widely applied in food science during the last decade, mostly for investigating fruits and vegetables, and several studies are present in literature, mainly concerning the determination of the internal morphology and the evolution of tissues during postharvest ripening and storage. MRI proved to be a powerful tool in food quality assessment, providing informative images about the spin density distribution, mostly water molecules, and the relationship between water and cellular tissues. Kiwifruit have been extensively studied over the years; in the present work, 6 new selections have been investigated by means of MRI. The internal morphologies of these selections have been compared to fruit of the cultivar 'Hayward'. Several changes were observed, which differ from each selection to the other and will be briefly illustrated. Source