Volume 16, No. 3, March 2016, Pages 581-592 PDF(1.18 MB)
Non-Methane Volatile Organic Compounds in the Background Atmospheres of a Southern European Mountain Site (Mt. Cimone, Italy): Annual and Seasonal Variability
Eleonora Lo Vullo1, Francesco Furlani1,2, Jgor Arduini1,3, Umberto Giostra1,2, Paolo Cristofanelli3, Martin L. Williams4, Michela Maione1,2,3
1 University of Urbino, Department of Basic Sciences and Foundations (DiSBeF), Urbino, Italy
2 National Inter-University Consortium for Physics of the Atmosphere and Hydrosphere (CINFAI), Tolentino, Italy
3 National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Bologna, Italy
4 King’s College London, Environmental Research Group, Science Policy Group, London, UK
- NMVOCs measured at Mt. Cimone over the last 5 years showed a general decreasing trend.
- The seasonal cycles are influenced by OH concentrations but also by local emissions.
- We showed the substantial role of the pollution from PBL in the summer.
Since January 2010 continuous high-frequency in situ measurements of a range of anthropogenic Non-Methane Volatile Organic Compounds (NMVOCs) has been carried out at the World Meteorological Organisation Global Atmospheric Watch observatory at Mt. Cimone, on the highest peak of the Italian Northern Apennines, at the border between the Po Valley and the Mediterranean Basin. Five-year (2010–2014) time series of eleven NMVOCs, including aromatic and aliphatic species, have been analysed in order to derive average mixing ratios and detect annual and seasonal variability. Recent studies conducted in Europe, mainly in urban areas, have reported a decrease in atmospheric NMVOCs. Here we investigate how the decline in emissions, due to the implementation of air pollution policies, is reflected in the annual variability of NMVOC mixing ratios measured at a regional background location. Analysis of temporal trends for well-mixed conditions showed statistically significant decreases in ethyne, n-pentane and ethyl-benzene, while no significant trends were found for propane, butanes, i-pentane, toluene and xylenes. The seasonal variability of NMVOCs has been studied showing clear seasonal cycles for longer lived compounds and cycles with smaller seasonal amplitudes for shorter- lived species. We used the propane time series to describe the seasonal cycle and to verify to what extent the mixing ratios of propane have been depleted by OH oxidation. We found that, during the summer, different transport times to the receptors and different source distribution are the main responsible for the relatively low integrated OH concentrations at Mt. Cimone.
Volatile hydrocarbons; Air quality; Hydroxyl radical; Long-term observations.