Aerosol measurements and evidence of gas-to-particle conversion processes at mace head, Ireland

Abstract

Some general characteristics of Aitken nuclei (AN) and equivalent black carbon (EBC) during background and polluted conditions have been shown, and estimate of background concentrations are given in this chapter. The characteristics of AN production events have also been considered. Very high AN concentrations are attributed to photochemical gas-to-particle conversion processes. It is likely that these events were due to nucleation following oxidation of biogenic precursor gases. The exact chemical nature of these precursor gases is not clear, however they are thought likely to be sulfur species probably including dimethylsulphide (DMS). Reactive species may also have increased the nucleation potential of precursor gases. The observed decrease in the EBC concentration during AN production may indicate that the absorption characteristics of the ambient aerosol are being modified by coagulative deposition of the AN. Such processes may also affect the hydroscopic properties of the larger aerosol. If such events are typical of coastal boundary areas, then they may significantly alter the number concentrations and physical and chemical characteristics of air masses entering and leaving marine/continental areas.