Long-term aerosol measurements in Gran Canaria, Canary Islands: Particle concentration, sources and elemental composition

Abstract

There are very few sets of long-term measurements of aerosol concentrations overthe North Atlantic Ocean, yet such data is invaluable in quantifying atmospheric dustinputs to this ocean region. We present an 8-year record of total suspended particles (TSP)collected at three stations on Gran Canaria Island, Spain (Taliarte at sea level, Tafira 269 mabove sea level (a.s.l.) and Pico de la Gorra 1930 m a.s.l.). Using wet and dry depositionmeasurements, the mean dust flux was calculated at 42.3 mg m 2d 1. Air mass backtrajectories (HYSPLIT, NOAA) suggested that the Sahara desert is the major source ofAfrican dust (dominant during 32–50% of days), while the Sahel desert was the majorsource only 2–10% of the time (maximum in summer). Elemental composition ratios ofAfrican samples indicate that, despite the homogeneity of the dust in collected samples,some signatures of the bedrocks can still be detected. Differences were found for the Sahel,Central Sahara and North of Sahara regions in Ti/Al, Mg/Al and Ca/Al ratios, respectively.Elements often associated with pollution (Pb, Cd, Ni, Zn) appeared to share a commonorigin, while Cu may have a predominantly local source, as suggested by a decrease in theenrichment factor (EF) of Cu during dust events. The inter-annual variability of dustconcentrations is investigated in this work. During winter, African dust concentrationmeasurements at the Pico de la Gorra station were found to correlate with theNorth Atlantic Oscillation (NAO) index