J. Dewulf

Emissions of biogenic volatile organic compounds from Fraxinus excelsior and Quercus robur under ambient conditions in Flanders (Belgium)

A dynamic branch enclosure system was used to measure emission rates of biogenic volatile organic compounds (BVOCs) from two common European tree species: Fraxinus excelsior and Quercus robur under ambient conditions in Flanders (Belgium). Both tree species were studied for seasonal variability of BVOC emission rates under natural biotic stress (infestations). Emissions were normalized at standard conditions of temperature and photosynthetic active radiation (PAR) (30°C and 1000u2009µmolu2009m−2u2009s−1, respectively). Emission rates from Fraxinus excelsior were highest in May (9.56u2009µgu2009gDW −1u2009h−1) and lowest in October (1.17u2009µgu2009gDW −1u2009h−1). This tree species emitted (Z)-β-ocimene, (E)-β-ocimene and α-farnesene during the entire measurement period and additionally isoprene only in May. Quercus robur showed isoprene emission variations according to the seasonal cycle with rates of 30, 106 and 29u2009µgu2009gDW −1u2009h−1 in May, August and October, respectively. Apart from isoprene, (E)-β-ocimene and β-caryophyllene were emitted through the entire experimental period.

Volatile organic compounds in an urban environment: a comparison among Belgium, Vietnam and Ethiopia

The effects of urban and indoor air pollution on human health are a major environmental concern for all, but not much has been researched in the developing world. Specifically, quantitative data on the occurrence of volatile organic compounds (VOCs) – main contributors to air pollution – in Asia and Africa are scarce compared to the availability of data in the developed world. This paper presents one of the first studies focusing on the analysis and occurrence of VOCs in Vietnam and Ethiopia, which constitutes part of the novelty of this work. A spectrum of 34 VOCs was measured at eight different urban sites in Ghent (Belgium), Hanoi (Vietnam), Jimma and Addis Ababa (Ethiopia) during three sampling campaigns from September 2008 to September 2010. Sampling was done in an active way by means of sorbent tubes filled with Tenax TA. The analysis was done by TD-GC-MS using internal standard calibration. Data were interpreted and compared in terms of (i) individual, subgroup and total VOCs concentration (TVOCs), (ii) indoor-to-outdoor (I/O) concentration ratios, (iii) source identification by diagnostic ratio and/or correlation coefficients, and (iv) ozone formation potential (OFP) at outdoor sites based on up-to-date maximum incremental reactivity (MIR). I/O concentration ratios varied between 0.2 and 30, with big differences noticed with respect to the type of VOC(s) considered and the type of outdoor sampling location. The highest TVOC concentrations were measured in street samples with maximum values of 54u2009µg/m3 in Ghent, 507u2009µg/m3 in Hanoi and 318u2009µg/m3 in Addis Ababa illustrating the large difference in ambient air quality levels. This is also reflected in the arithmetic mean OFP values (µg/m3) of 82, 1308 and 596 in Ghent, Hanoi and Addis Ababa, respectively. Results of this study could be helpful to support formulation of national policy with regard to ambient air quality.

Dynamic capillary diffusion system for monoterpene and sesquiterpene calibration: quantitative measurement and determination of physical properties

This article describes a method for preparation of low concentration gas standard mixtures of biogenic volatile organic compounds (BVOCs) emitted primarily by plants. A set of 10 plant volatiles including α-pinene, β-pinene, 3-carene, linalool, methyl salicylate, α-cedrene, β-caryophyllene, β-farnesene, aromadendrene and α-humulene was used in the study. Gas standard mixture of these compounds was generated using a capillary diffusion system (CDS). Diffusion coefficient (D) and saturation vapour pressure (p s) data of these compounds were calculated from experimentally determined gas chromatographic retention indices (RI) and empirical relationships between D and p s versus RI. A comparison of the calculated and measured concentrations of investigated compounds has proved that designed CDS can be successfully used for the proper quantification of BVOCs.

Accelerated solid-phase dynamic extraction for the analysis of biogenic volatile organic compounds in air

In this study, accelerated solid phase dynamic extraction (ASPDE) technique was used to identify biogenic volatile organic compounds (BVOCs) emitted from Norway spruce (Picea abies). Compounds that were determined in tree samples are: tricycylene, α-pinene, camphene, β-pinene, myrcene, 3-carene, p-cymene, limonene, cineole, α-phellandrene, α-terpinene, γ-terpinene and terpinolene. ASPDE showed a potential for the analysis of environmental samples as well as for field applications. This technique was further studied by using a gaseous mixture of BVOCs (sabinene, α-pinene, β-pinene, limonene, linalool, and (Z)-hexenyl acetate) and exhibited a good repeatability during all the experiments in the range of 2.5% (α-pinene) and 14.6% (linalool). However, during the analysis of samples it was observed that desorption at high temperature (230°C) can lead to the formation of artifacts, which were not observed at the desorption temperature of 100°C. Further experimental investigations revealed that monoterpenes appeared as unanticipated compounds during desorption of ASPDE samples; these compounds were degradation products of linalool.