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| q |
In most of the seasons, there are always abundant NO2 in the
stratosphere to
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tie up a significant fraction of the available chlorine in the form
of chlorine
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nitrate.
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| q |
In the wintertime Antarctic stratosphere, NO2 concentrations are
low, because
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most of the odd nitrogen has been converted into HNO3 and become
droplets
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in PSCs (polar stratospheric clouds).
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| q |
Therefore, the formation of PSCs allow reactive chlorine
concentration to
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increases.
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| q |
The PSCs particles also help convert unreactive forms of
chlorine into reactive
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chlorine by providing surfaces on which heterogeneous reaction can
occur.
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