Soluble organic compounds in fog and cloud droplets: what we have learned in the past few years

We have recently set up a new procedure for characterising the water
soluble organic compounds (WSOC) in fog water, for which information is
still rather limited. Fog samples collected during the 1998-99 fall-winter
season in the Po Valley (Italy) were analysed following this procedure,
which allows a quantitative determination of three main classes of organic
compounds (neutral species, mono- and di-carboxylic acids, polycarboxylic
acids), together accounting for ca. 85% of the total WSOC. This procedure
also provides information on the main chemical characteristics of these
three classes of compounds (functional groups, aliphatic vs. aromatic
character etc.). The enhanced chemical knowledge on fog/cloud chemical
composition opens new scenarios as far as chemical and microphysical
processes in clouds and fogs are concerned.