Nucleation in the coastal environment
New particle formation in the coastal environment has been widely studied in recent years and is a focus of several funded projects within CAS activities including the UK SOLAS funded Reactive Halogens in the Marine Boundary Layer (RHaMBLe), EU FP6 funded Marine Aerosol Production (MAP), the International Polar Year (IPY) NERC-funded COBRA and the NERC-funded INSPECT projects. It has been demonstrated that coastal nucleation results from emissions of molecular iodine (McFiggans et al., 2005) on macroalgal exposure during daytime low-tide leading to production of iodine oxides which can efficiently cluster to form particles a few nanometres in diameter.Within CAS we have developed a coupled box model incorporating gaseous iodine photochemistry and a sectional description of aerosol microphysics. The model produces ultrafine particles in the smallest size range by the explicit clustering of all possible molecular collision pairs from the iodine oxides. A simplified version of this model has been applied to atmospheric simulations of measured particle bursts and to simulations of laboratory experiments. We are working with the University of Helsinki within the MAP project to produce a parameterised scheme of iodine-induced nucleation for use in large-scale models. The work is being carried out by Gordon McFiggans.