Monitoring of Biogenic Volatile organic Compounds (BVOCs) in Air with Analytical Techniques

Biogenic volatile organic compounds (BVOCs), are a heterogeneous group of molecules with a wide range of functions useful for plants and, consequently, for the whole ecosystem and the environment. The general aim of this dissertation is the study and monitoring of BVOC emissions in different place and time and the correlation between emissions and climate changing, atmospheric reaction and behaviour of birds. This dissertation concerns 4 main chapters in which we discuss 4 different aspects of the study of BVOC emissions. The first one regards a rapidly and inexpensive analytical method that is based on the use of thermal gas chromatography (TD-GC-MS) to monitor BVOCs released by Juniperus Communis in Sibillini National Park. Hexanal, Toluene, α-Pinene, 4-Terpineol and β-Caryophyllene have been used as standard compounds. This method showed a good sensibility (limit of detection ranges between 10-19 pptv for all compounds except for Hexanal that is 100 pptv), repeatability (RDS% within 11%), precision (recovery higher than 85%) and selectivity. We collected samples in situ from April 2016 to September 2017 almost once for months. The compounds have been identified using Kovats retention indices (RI) and quantified with the response factor (RF) for different class of compounds. All samples have been correlated with temperature and humidity values. The results show higher emission in April (flowering period) and at particular condition of temperature (24°C). These results are comparable to the data found in the literature about emissions of Juniperus Communis, confirming the validity of the developed method. The second aspect of our research project regards the study of all parts of Juniperus Communis and Juniperus Oxycedrus using a different analytical technique: Solid Phase Microextraction (SPME). The study was performed in June, during the blowing period, different plant parts were sampled (branches, leaves, fruits) and analyzed in the laboratory; the study was conducted to complete the monitoring of emissions in the National Park of Sibillini to understand which BVOCs come from different parts of the plant. From the results obtained, there is a greater emission from the Juniperus Oxycedrus, this confirms the data obtained during the air monitoring lasted two years. In fact, while the red juniper emits more monoterpenes and sesquiterpenes, the Juniperus Communis is rich in oxygenated terpenes. Moreover, during my PhD I spent 6 months abroad in Mainz at the Max Planck Institute for Chemistry in Jonathan Williams’s research group. I studied oxygenated BVOC emissions in Amazon forest during dry season. The site chosen for this study was the Amazon Tall Tower Observatory, ATTO, the site is equipped with a 325m tall tower and sampling was performed on this tower at four different heights (40, 80, 150 and 320 m). the analysis were performed using a thermal desorption coupled with a TOF-MS equipped with a cyclodextrin column to observe chiral compounds. The use of the chiral column allowed the separation of the enantiomers R and S and, in the case of 1-Hexanol-2-Ethyl it was possible to evaluate the relationship between the two enantiomers. In this case, a change of chirality is observed between 40 and 80m and again between 80m and 320m. Moreover, we found that Nonanal is the compound higher emitted by plants as defence mechanism after bacterial or insect attack. In the case of the MEK, however, it was confirmed that it is directly emitted from the vegetation in fact shows a concentration greater than 40m. Subsequently it tends to decrease until it reaches 320m where an increase can be observed, this has become due to the formation of MEK as an oxidation product of alkanes or other compounds. Then we found that trend of isoprene’s degradation products are in accordance with the results in the literature and that, at times when the isoprene is most emitted, the MVK and the MACR are lower but they increase in height, in fact they get higher concentrations at 320m. The last study concerns a field campaign in Arnino (Pisa, Italy), this project is a collaboration between Max Planck Institute for Chemistry, Max Planck Institute for Ornithology and University of Pisa. The objective of the project is to analyze the emissions correlating them to the wind direction and then to create an olfactory map of the pigeons with the aim of connecting the emissions to the orientation of the pigeons. In particular, I studied compounds emitted primarily from anthropogenic sources such as Benzene, Toluene but also Acetone, and were later correlated with the wind direction figures to understand where the major contribution of these compounds comes from. In the case of compounds such as Benzene and Toluene (emitted by vehicles or industries), it is possible to observe a daily profile with the highest emissions during the day which then decrease in the night and moreover, there are greater concentrations when the wind comes from the city of Pisa and then from East / South-East. The Acetone study has encountered major problems, because this compound comes from different contributions.