Non-methane hydrocarbons at a high-altitude rural site in the Mediterranean (Greece)

Acetylene, C3–C10 paraffins, olefins, aromatic hydrocarbons and the biogenic isoprene, were determined in six sampling periods from May to October in 1996–1997. The concentrations of the determined species were generally lower than those measured in southeastern US and western France, but higher than those measured in more remote regions. Acetylene and C3–C5 hydrocarbons exhibited seasonal variation with higher concentrations in the late October sampling period. The aromatic hydrocarbons, except benzene, exhibited maximum concentrations in the summer. Isoprene had maximum concentrations in the summer, with its concentration linearly increasing as a function of the logarithm of temperature, in agreement with past studies. Its emission flux was calculated to be on the lower end of similar studies in US. The main destruction route of all hydrocarbons was determined to be due to their photochemical reactions. The photochemical reactivity, calculated in terms of propylene equivalent concentration, was in the summer dominated by isoprene which accounts for 69% of the total, aromatics with 16%, olefins with 11% and paraffins with 4%. In the May and October periods, the aromatics contributed the most ( 37%) to the photochemical reactivity. Air mass back trajectories indicated higher concentrations when air masses arrived from northwestern and northeastern, compared to southern, directions.