A low pressure laser-induced fluorescence instrument (adapted from the HOx LIF system) was developed to measure iodine monoxide (IO) at low concentrations.

Iodine monoxide (IO) is an iodine-based oxidant that is present in high concentrations in marine environments. IO can lead to ozone destruction and new particle formation but point measurements of IO have been limited.

The instrument was brought to Mace Head Atmospheric Research Station on the west coast of Ireland to make point measurements of IO beside large beds of macroalgae (seaweed).

The highest concentrations of IO ever measured were seen at daytime low tide and a strong dependance on tide height was observed. Comparison with iodine atom measurements and spatially averaged IO was also possible for a limited time. Data showed strong temporal variability in IO mixing ratios that had not been observed previously and provided direct evidence of an inhomogeneous spatial distribution of IO at the coast-line (Commane et al. 2011, ACP).