Field measurements of biogenic volatile organic compounds in the atmosphere using solid-phase microextraction Arrow

Biogenic volatile organic compounds (BVOCs) emitted by terrestrial vegetation participate in a diversity of natural processes. These compounds impact both on short-range processes, such as on plant protection and communication, and on high-range processes, by e.g. participation on aerosol particle formation and growth. The biodiversity of plant species around the Earth, the vast assortment of emitted BVOCs, and their trace atmospheric concentrations contribute to the high remaining uncertainties about the effects of these compounds on atmospheric chemistry and physics, and call for the development of novel collection devices that can offer portability with improved selectivity and capacity. In this study, a novel solid-phase microextraction (SPME) Arrow sampling system was used for the static and dynamic collection of BVOCs from the boreal forest, and samples were subsequently analysed on-site by gas chromatography-mass spectrometry (GC-MS). This system offers higher sampling capacity and improved robustness than the traditional equilibrium-based SPME techniques, such as SPME fibers. Field measurements were performed in summer 2017 at the Station for Measuring Ecosystem-Atmosphere Relations (SMEAR II) in Hyytiälä, Finland. Complementary laboratory tests were also performed to compare the SPME-based techniques under controlled experimental conditions and to evaluate the effect of temperature and relative humidity on their extraction performance. The most abundant monoterpenes and aldehydes were successfully collected. A significant improvement on sampling capacity was observed with the new SPME Arrow system when compared to SPME fibers, with collected amounts being approximately 2 times higher for monoterpenes and 7-8 times higher for aldehydes. BVOC species exhibited different affinities for the type of sorbent materials used (PDMS/Carbon WR vs. PDMS/DVB). Higher extraction efficiencies were obtained with dynamic collection prior to equilibrium regime, but this benefit during the field measurements was small probably due to the natural agitation provided by the wind. An increase in temperature and relative humidity caused a decrease in the amounts of analytes extracted under controlled experimental conditions, even though the effect was more significant for PDMS/Carbon WR than for PDMS/DVB. Overall, results demonstrated the benefits and challenges of using SPME Arrow for the sampling of BVOCs in the atmosphere.Peer reviewe