Abstract
More than 7000 atmospheric measurements of over 60 C2 − C16
volatile organic compounds (VOCs) were conducted at a background site in Cyprus during a 1-month intensive field campaign held in March 2015. This
exhaustive dataset consisted of primary anthropogenic and biogenic VOCs, including a wide range of source-specific tracers,
and oxygenated VOCs (with various origins) that were measured online by flame ionization detection–gas
chromatography and proton transfer mass spectrometry. Online submicron aerosol chemical composition was performed in
parallel using an aerosol mass spectrometer. This study presents the high temporal variability in VOCs and their associated
sources. A preliminary analysis of their time series was performed on the basis of independent tracers (NO, CO, black
carbon), meteorological data and the clustering of air mass trajectories. Biogenic compounds were mainly attributed
to a local origin and showed compound-specific diurnal cycles such as a daily maximum for isoprene and a nighttime maximum for
monoterpenes. Anthropogenic VOCs as well as oxygenated VOCs displayed higher mixing ratios under the influence of
continental air masses (i.e., western Asia), indicating that long-range transport significantly contributed to the VOC
levels in the area. Source apportionment was then conducted on a database of 20 VOCs (or grouped VOCs) using a source
receptor model. The positive matrix factorization and concentration field analyses were hence conducted to identify and
characterize covariation factors of VOCs that were representative of primary emissions as well as chemical transformation
processes. A six-factor PMF solution was selected, namely two primary biogenic factors (relative contribution of 43 %
to the total mass of VOCs) for different types of emitting vegetation; three anthropogenic factors (short-lived combustion
source, evaporative sources, industrial and evaporative sources; 21 % all together), identified as being either of local origin
or from more distant emission zones (i.e., the south coast of Turkey); and a last factor (36 %) associated with
regional background pollution (air masses transported both from the Western and Eastern Mediterranean regions). One of the
two biogenic and the regional background factors were found to be the largest contributors to the VOC concentrations
observed at our sampling site. Finally, a combined analysis of VOC PMF factors with source-apportioned organic aerosols
(OAs) helped to better distinguish between anthropogenic and biogenic influences on the aerosol and gas phase
compositions. The highest OA concentrations were observed when the site was influenced by air masses rich in semi-volatile
OA (less oxidized aerosols) originating from the southwest of Asia, in contrast with OA factor contributions associated
with the remaining source regions. A reinforcement of secondary OA formation also occurred due to the intense oxidation of
biogenic precursors.
Citation
ID:
176002
Ref Key:
debevec2017atmosphericorigin