Aerosol measurements and evidence of gas-to-particle conversion processes at Mace Head, Ireland.

An analysis of Aitken nuclei (AN) and equivalent black carbon (EBC) aerosols concentrations from measurements at Mace Head is presented. The data presented here are from 1991 but are considered to be representative of long term measurements at the Mace Head site and are presented in this context. Estimates of background AN and EBC concentration in north Atlantic air masses are given as well as values for polluted conditions. Variations in these values are discussed. Examples of the occurrence of very high AN concentrations (>30,000 cm(-3)) which are considered to have resulted from local photochemical gas-to-particle conversion processes are presented. Factors controlling these production events are examined.