CHEMICAL COMPOSITION OF ATMOSPHERIC BULK DEPOSITION AT THE INDUSTRIAL AREA OF GELA (SICILY, ITALY)

Abstract

Bulk deposition has been collected at six sampling sites in area of Gela plain (Italy) in the period from February 2008 to May 2009. Samples collected each two weeks were analysed for the major ion and trace elements content. Preliminary results allow identifying three different sources that control the abundance of the elements in atmospheric deposition: (1) sea spray, (2) geogenic dust, and (3) anthropogenic pollution. Due to the closeness of the coast, clear evidence of sea spray input is detectable for most of the samples. The high excess of non sea-salt sulphate (50 - 90% of the total) is prevailingly ascribable to the abundant SO2 emissions of the refinery. The pH values of the collected samples range from 4.2 to 8.6, with 80% of them above pH 6.5, indicating an extensive neutralization. This is due to NH3 coming from widespread agricultural activities in the plain of Gela, and geogenic CaCO3 either from local or from regional (desert dust) sources. Elevated levels of trace metals (Zn, V, Sb, Ni, Cr, Ni and Cu) can be observed in the samples collected close to the industrial area. All these elements can be identified as “anthropogenic” and attributed to the human activities, mainly to the industrial emissions, but a contribution could also derive from the intensive vehicular traffic.