When we were coming in, we saw really substantial plumes of
SO2 that the CalTech guys were measuring and we
see signs of it in our instrument and then very sustained levels of the fine
sulfate aerosol and this is something that they call "vog," which is sort of
like fog, except it's from a volcano and
the volcano is emitting a lot of SO2.
Some volcanoes emit low levels all the time. I think Kilauea's emitting
fairly high levels fairly often. This stuff oxidizes to make sulfuric acid and that
then forms small droplets of sulfuric acid
and when these guys take up water, they swell and make the real visible
haze, the strong haze that we saw the whole time we were in Kona.
Sulfuric acid is not good for you; this is a big part of acid rain
and the same sort of chemistry happened in the U.S.
that precipitated the Clean Air Act.
So all the SO2 in that case was mostly from coal-burning,
but we did a lot to clean that up and reduce acid rain,
certainly an environmental crisis in the eastern U.S. probably 30 years ago.