Chemical and physical characteristics of aerosol particles at a remote coastal location, Mace Head, Ireland, during NAMBLEX

• Main Authors: Coe, H., Allan, J. D., Alfarra, M. R., Bower, K. N., Flynn, M. J., Mcfiggans, G. B., Topping, D. O., Williams, P. I., O'Dowd, C. D., Dall'Osto, M., Beddows, D. C. S., Harrison, R. M.
• Other Authors: School of Earth, Atmospheric and Environmental Sciences Manchester (SEAES), University of Manchester Manchester, Laboratory of Environmental Chemistry Villigen (LUC), Paul Scherrer Institute (PSI), Department of Physics NUI Galway, National University of Ireland Galway (NUI Galway), School of Cancer Sciences, University of Birmingham Birmingham, Department of Physics, University of Wales
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Aitken; Mace; North Atlantic
• Online Access: https://hal.science/hal-00296000; https://hal.science/hal-00296000/document; https://hal.science/hal-00296000/file/acp-6-3289-2006.pdf

International audience A suite of aerosol physical and chemical measurements were made at the Mace Head Atmospheric Research Station, Co. Galway, Ireland, a coastal site on the eastern seaboard of the north Atlantic Ocean during NAMBLEX. The data have been used in this paper to show that over a wide range of aerosol sizes there is no impact of the inter-tidal zone or the surf zone on measurements made at 7 m above ground level or higher. During the measurement period a range of air mass types were observed. During anticyclonic periods and conditions of continental outflow Aitken and accumulation mode were enhanced by a factor of 5 compared to the marine sector, whilst coarse mode particles were enhanced during westerly conditions. Baseline marine conditions were rarely met at Mace Head during NAMBLEX and high wind speeds were observed for brief periods only. The NAMBLEX experiment focussed on a detailed assessment of photochemistry in the marine environment, investigating the linkage between the HO x and the halogen radical cycles. Heterogeneous losses are important in both these cycles. In this paper loss rates of gaseous species to aerosol surfaces were calculated for a range of uptake coefficients. Even when the accommodation coefficient is unity, lifetimes due to heterogeneous loss of less than 10 s were never observed and rarely were they less than 500 s. Diffusional limitation to mass transfer is important in most conditions as the coarse mode is always significant. We calculate a minimum overestimate of 50% in the loss rate if this is neglected and so it should always be considered when calculating loss rates of gaseous species to particle surfaces. HO 2 and HOI have accommodation coefficients of around 0.03 and hence we calculate lifetimes due to loss to particle surfaces of 2000 s or greater under the conditions experienced during NAMBLEX. Aerosol composition data collected during this experiment provide representative information on the input aerosol characteristics to western Europe. During NAMBLEX ...