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 t wo years. Mass/size distributions were obtained in the size range 0.06 -10 mum using Berner low-pressure cascade impactor systems. The distri butions obtained reflect the different types of air mass which are enc ountered at Mace Head. Westerly winds are dominant at the site with th e associated air masses being typically maritime. Unimodal mass/size d istributions with the peak mass concentration occurring principally in the 2-4 mum size range were characteristic of these conditions. Conti nental air masses from Europe are typified by mass/size distributions which have peak values in the submicron size range. Distinct bimodal d istributions 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 conce ntration 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 mari time air masses at higher wind speeds. A drop-off in mass concentratio n was observed at wind speeds greater than approximately 11 m s-1. Thi s is attributed to the cut-off characteristic of the PM10 inlet used w ith the impactor system. High mass concentrations during long term pol lution events at Mace Head were also observed with the collected aeros ol resident principally in the submicron size range during these condi tions.