ESS101C
Prof.
Jin-Yi Yu
The Chlorine Cycle
qNatural sources of
chlorine:
(1) Methyl
chloride (CH3Cl): produced by marine plankton.
(2) Hydrogen
chloride (HCl): produced by
volcanic eruption and by evaporation of sea
spray.
These natural-generated chlorine are most removed by
precipitation before they reach the stratosphere.
qThe largest
sources of stratospheric chlorine today are freons (CFCs), which are thropogenic compounds.
èCFCs do not react
in either the troposphere or lower stratosphere
èCFCs go all the
way to the upper stratosphere and are photolyzed by UV radiation.
è The Cl so
produced proceeds to destroy ozone.
è
Eventually, Cl react with CH4 and is diffused to the
troposphere, where it is precipitated out.
(from The Earth System)