Natural river processes are able
to reduce levels of contaminants and the higher concentrations of contaminants
found in Columbia River water in urban areas, such as Portland, suggest
that the sources of pollution are from local sites and not due to an accumulation
of pollutants from upstream.
These are two conclusions from a
study recently completed by U.S. Geological Survey scientist Dr. Kathleen
McCarthy at the agencys water resources division in Portland. McCarthy
used a …
