MASS MEASUREMENTS OF AEROSOL AT MACE HEAD, ON THE WEST-COAST OF IRELAND

Aerosol mass size measurements have been carried out at the Mace Head research station, on the west coast of Ireland, for a period of over two years. Mass size distributions were obtained in the size range 0.06-10 mum using Berner low-pressure cascade impactor systems. The distributions obtained reflect the different types of air mass which are encountered at Mace Head. Westerly winds are dominant at the site with the associated air masses being typically maritime. Unimodal mass size distributions with the peak mass concentration occurring principally in the 2-4 mum size range were characteristic of these conditions. Continental air masses from Europe are typified by mass size distributions which have peak values in the submicron size range. Distinct bimodal distributions were obtained when aerosols were collected from a mixture of air mass types. Overall, the mass concentration was found to vary between approximately 2 and 45 mug m-3. A wide variation in mass concentration values were measured at similar wind speeds. However, a trend towards higher mass concentrations at higher wind speeds was observed in the coarse mass fraction contribution ( 1 mum) from westerly maritime air masses at higher wind speeds. A drop-off in mass concentration was observed at wind speeds greater than approximately 11 m s-1. This is attributed to the cut-off characteristic of the PM10 inlet used with the impactor system. High mass concentrations during long term pollution events at Mace Head were also observed with the collected aerosol resident principally in the submicron size range during these conditions.