presley wrote:
A further elaboration of the theme of the chemical composition of
rainfall: "What is a chemical salt recipe for 'typical' rainwater?

Rainwater gets its compositions largely by dissolving particulate
materials in the atmosphere (upper troposhere) when droplets of
water nucleate on atmospheric particulates, and secondarily by
dissolving gasses from the atmosphere. Rainwater compositions vary
geographically.
In open ocean and coastal areas they have a salt content
essentially like that of sea water (same ionic proportions but much
more dilute) plus CO2 as bicarbonate anion (acidic pH).

Terrestrial rain compositions vary siginificantly from place to
place because the regional geology can greatly affect the types of
particulates that get added to the atmosphere. Likewise, sources of
gaesous acids (SO3, NO2) and bases (NH3) vary as a function of
biome factors and anthopogenic land use practices. Each of these
gasses can be added in varying proportions from natural and non
natural input sources (non-natural sources of SO3 and NO2 far
outweigh natural ones). Particulate load to the atmosphere can also
be greatly affected by human activities. Finally, local climate
(especially the amount of precipitation in one area compared to
another) will affect the solute concentrations in terrestrial
rainwaters. The result is highly variable compositions, so there
isn't one simple formula. If you want to read up a bit on this and
see data for rainwater from many different locales globally, I
suggest the book "Global
Environment: water air and geochemical cycles" by Berner and Berner
(Prentice-Hall, 1996) or a similar text "

Here in the PNW our rain comes in off the Pacific Ocean and it is not
the least bit salty.

--

Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8
Sunset Zone 5