Foam: Natural causes or pollution in our waters?
If the Cahoon Creek has a "clean bill of health," as reported by the Sea Scouts in the March 21 issue of the Observer, why is there foam in the creek? Is it from pollution? This question was posed by a reader of the Observer who lives by the creek. Two members of the Marine Environment Explorer Club 360, Norah Hamil and Jennie Koomar, set out to answer this question. Research suggested that a close examination of the foam would point to its source.
Foam is generated when there is a change in water surface tension and air is introduced. Surface tension is that force on a water/air interface that forms a slight film on the surface of water. Surface tension is what forms beads of water on a newly waxed car and also allows certain insects and spiders to walk on water. When certain chemicals, called surface active agents or surfactants, are introduced to the water the surface tension is reduced and then as air is introduced by turbulence, foam is formed.
Synthetic surfactants in streams are the result of detergents and produce foam close to the source that is short lived, has a perfume smell and it has rainbow reflections in its bubbles. There are also natural surfactants that are created by decomposing and rotting leaves and vegetation. Foam caused by natural sources forms where there is turbulence along the length of a stream. It is white in color, but turns brown over time and occurs after a rainfall.
One Friday after school, the Explorer Club trekked out in the rain to observe a stretch of the Cahoon Creek. We found foam in the creek, which was white in color. At a weir just north of Detroit Road we took foam samples, they did not have a detergent or perfume smell (in fact had a strong fishy smell) and the bubbles were clear of any rainbow coloring.
In conclusion, we determined that the surfactants producing the foam had to be formed by the natural decomposition of vegetation. Considering that the Cahoon Creek passes through the Cleveland Metroparks’ only large wetland marsh at Bradley Woods Reservation it is not surprising that natural surfactants flow in the creek.
Explorer Club 360 is a Learning for Life affiliate of the Boy Scouts for students in sixth through eighth grade. The club concentrates on STEM projects related to our marine environment while developing life skills, character, leadership and ethics. For further details contact adviser, Richard Gash, 440-871-6106 or firstname.lastname@example.org.
Norah Hamil and Jennie Koomar
Marine Explorer's Club 360