ClOx

ClOx is a shorthand term in atmospheric chemistry for chlorine oxide species, notably chlorine monoxide (ClO) and chlorine dioxide (ClO2). It also refers to related chlorine-oxygen compounds formed during atmospheric chlorine chemistry. The ClOx pool represents reactive chlorine-derived species that drive ozone-related reactions under sunlight.

In the stratosphere, ClOx species participate in catalytic cycles that destroy ozone. Chlorine from human-made compounds releases atoms that form ClO; through further reactions, ClOx can be converted to reservoir species such as ClOOCl, which photolyzes to release chlorine again. These cycles enable small chlorine amounts to cause substantial ozone loss.

Formation and distribution: ClOx arise from the breakdown of chlorine-containing gases and accumulate in the stratosphere, especially during polar spring when polar stratospheric clouds promote chlorine activation. They also participate in tropospheric chemistry, affecting radical budgets and atmospheric oxidizing capacity.

Measurement and significance: ClOx levels are monitored by satellite and ground-based spectroscopy. Their observed abundance correlates with ozone depletion and is used to track recovery progress of the ozone layer following reductions in emissions of chlorine-containing compounds.