Iodine oxide homogeneous nucleation: An explanation for coastal new particle production

A series of laboratory experiments on the chemical composition of aerosol p articles formed after photodissociation of CH2I2, a major volatile alkyl ha lide released from macroalgae, have been performed in a laboratory scale re action chamber using on-line atmospheric pressure chemical ionization mass spectrometry (APCI/MS). Based on the mass spectrometric results and the mol ecular properties of iodine oxides, we suggest that the self-nucleation of iodine oxides provides an efficient source of natural condensable material in coastal environments and discuss this concept focusing on OIO as one pot ential key species for new particle formation. The presented hypothesis not only fits the measured enrichment of iodine species in submicrometer parti cles, but also can explain the frequently observed nucleation bursts in the coastal boundary layer.