Website beginnings by David Tacke

This is a new, little website to showcase a few of my images. Over time, I will add increasing numbers of photographs, reaching back to 1971, a few perhaps further. An important purpose of this website is to convey a story with each image. In this case the subject is river foam.

Foam occurs naturally in rivers and streams as leaves and branches and other organic materials fall into the water, decay and decompose, releasing compounds known as dissolved organic carbon (DOC). Certain DOC are surface active agents, or surfactants. Surfactants interact with water, reducing surface tension, allowing air and turbulence to produce foam. Large ocean algal blooms can cause foam accumulations 3 feet deep. In northern Minnesota, bogs and wetlands introduce DOC into streams and lakes, resulting in the deep “tea” color of those water bodies.  

Human introduced synthetic surfactants, such as those created from household detergents, shampoos, cosmetics and other cleaning products, also create foam. A significant source of surfactants comes from various industrial agents, such as wetting agents, dispersants, de-foaming and de-inking compounds, antistatic agents, paint and protective coatings, pesticides, leather processing, plastics and elastomers, and oil extraction and production. Many industrial surfactants are very persistent in the environment and can ‘bio’accumulate in humans and other organisms. While these surfactants usually result in a foam which persists over a short range, some, such as Alkylphenol ethoxylates, perfluorooctanoic acid, perfluorooctane sulfonate, can be extremely detrimental to life forms due to their estrogenic and carcinogenic properties eliciting reproductive effects in fish and other organisms. 

In this case, foam was formed in turbulence below St. Anthony Falls, rose to the surface and then became concentrated in swirls and eddies in protected areas below the bridge.