Iodine oxide in the marine boundary layer

A striking example of the influence of halogen chemistry on tropospheric ozone levels is the episodic destruction of boundary-layer ozone during the Arctic sunrise by reactive halogen species1, 2. We detected iodine oxide in the boundary layer at Mace Head, Ireland (53°20′ N, 9°54′ W) during May 1997, which indicates that iodine chemistry is occurring in the troposphere.