Webster and Ashland?

One of the things I love about being a bicycle commuter is noticing the area you ride through in a more connected way—feeling the environment instead of passing through it. One of my regular does has me cruising the river at Webster and it got me wondering; why is the river foamy and smelling like cleaning products here? Also I don't know if I've ever noticed this particular scent other than this year, kind of like simple green. Asking this here because car brains probably never notice in their climate controlled lazyboi chairs.