by James G. Acker
I think that the most I ever learned about foam was in an
article about beer (seriously).
The article about beer basically said this: _any_ aqueous
solution can form a foam, but (obviously) the identity of what is
dissolved in solution affects both the consistency and quality of
the foam. In general, the higher concentrations of dissolved organic
matter [proteins, lignins, and lipids] will cause a foam to be thicker
and longer-lasting. If a foam is thick and persistent, that will give
it a greater ability to entrain particulates, which are likely to
affect the color of the foam.
Foams seen on sandy beaches are likely not generated
in situ. More commonly, a phytoplankton (algal) bloom offshore
will dissolve a large amount of organic matter in seawater, and as
this water is transported onshore by winds and then agitated in the
surf zone, foams will form. Speaking of contaminants, if the bloom
was a "red tide", the foam could contain toxins that could become
aerosols. These toxins might cause irritation and other respiratory
discomfort if inhaled. This phenomenon occasionally happens along
the west coast of Florida.
---- James Acker