Evidence for heavy fuel oil combustion aerosols from chemical analyses at the island of Lampedusa: a possible large role of ships emissions in the Mediterranean 1Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
11 Apr 2012
2ENEA, Laboratory for Earth Observations and Analyses, 92010, Lampedusa, Italy
3ENEA, Laboratory for Earth Observations and Analyses, 00123, S. Maria di Galeria, Rome, Italy
4ENEA, Laboratory for Earth Observations and Analyses, 90141, Palermo, Italy
5Department of Physics, University of Florence and I.N.F.N., Sez. Florence, Via Sansone 1, 50019 Sesto Fiorentino, Florence, Italy
Received: 20 October 2011 – Published in Atmos. Chem. Phys. Discuss.: 08 November 2011 Abstract. Measurements of aerosol chemical composition made on the island of
Lampedusa, south of the Sicily channel, during years 2004–2008, are used to
identify the influence of heavy fuel oil (HFO) combustion emissions on
aerosol particles in the Central Mediterranean. Aerosol samples influenced
by HFO are characterized by elevated Ni and V soluble fraction (about 80%
for aerosol from HFO combustion, versus about 40% for crustal particles),
high V and Ni to Si ratios, and values of Vsol>6 ng m−3.
Evidence of HFO combustion influence is found in 17% of the daily
samples. Back trajectories analysis on the selected events show that air
masses prevalently come from the Sicily channel region, where an intense
ship traffic occurs. This behavior suggests that single fixed sources like
refineries are not the main responsible for the elevated V and Ni events,
which are probably mainly due to ships emissions.
Revised: 19 March 2012 – Accepted: 28 March 2012 – Published: 11 April 2012
Vsol, Nisol, and non-sea salt
show a marked seasonal behaviour, with an evident summer maximum. Such a
pattern can be explained by several processes: (i) increased photochemical
activity in summer, leading to a faster production of secondary aerosols,
mainly nssSO42−, from the oxidation of SO2 (ii) stronger
marine boundary layer (MBL) stability in summer, leading to higher
concentration of emitted compounds in the lowest atmospheric layers. A very
intense event in spring 2008 was studied in detail, also using size
segregated chemical measurements. These data show that elements arising from
heavy oil combustion (V, Ni, Al, Fe) are distributed in the sub-micrometric
fraction of the aerosol, and the metals are present as free metals,
carbonates, oxides hydrates or labile complex with organic ligands, so that
they are dissolved in mild condition (HNO3, pH1.5).
Data suggest a characteristic nssSO42−/V ratio in the range
200–400 for HFO combustion aerosols in summer at Lampedusa. By using the
value of 200 a lower limit for the HFO contribution to total sulphates is
estimated. HFO combustion emissions account, as a summer average, at least
for 1.2 μg m−3, representing about 30% of the total
nssSO42−, 3.9% of PM10, 8% of PM2.5, and 11% of PM1.
Within the used dataset, sulphate from HFO combustion emissions reached the
peak value of 6.1 μg m−3 on 26 June 2008, when it contributed by
47% to nssSO42−, and by 15% to PM10.
Citation: Becagli, S., Sferlazzo, D. M., Pace, G., di Sarra, A., Bommarito, C., Calzolai, G., Ghedini, C., Lucarelli, F., Meloni, D., Monteleone, F., Severi, M., Traversi, R., and Udisti, R.: Evidence for heavy fuel oil combustion aerosols from chemical analyses at the island of Lampedusa: a possible large role of ships emissions in the Mediterranean, Atmos. Chem. Phys., 12, 3479-3492, doi:10.5194/acp-12-3479-2012, 2012.