Great News for Salmon
Reading this article really made my day.
The Problem
In 2020, scientists from the University of Washington, Western Washington University and the Center for Urban Waters in Tacoma were finally able to pinpoint that tire dust from roadway runoff was the source of a deadly chemical rapidly killing coho salmon swimming in urban streams. Tire manufacturers use a 6PPD compound in tires to protect tires from the attack of ozone, which could otherwise cause tires to crack and cause unsafe tire failure. However, this ozone reaction on 6PPD produces 6PPD-quinone in tire dust. When this dust runs off into roadside streams, it was found to be highly toxic to salmon (Science journal article), causing them to die before they reach their spawning grounds and lay their eggs. “Loss rates to die-offs are typically high, e.g., 40–90% of an entire fall run within a given urban stream” (ref).
“We’re talking concentrations that are about a few drops in an Olympic-sized swimming pool could kill half of a population of coho that you might put in that pool.”
The Good News
Since 6PPD-quinone was found to be the culprit killing salmon in urban streams, scientists at King County, Western Washington University and University of Washington have found a new soil mixture that could be used along roadsides to treat runoff laced with the deadly tire chemical. A layered combination of sand, coconut fiber, and biochar was found to remove nearly all of the pollutant. Read the full article.
When 20 juvenile coho salmon were exposed to untreated runoff water, nearly all of them died. However, when 20 juvenile coho salmon were exposed to runoff water treated by the new sand/coconut/biochar soil mixture, all of them survived.
King County is now working to transition this breakthrough research into practice. They continue to work with university scientists to verify the new soil treatment in the field at a site near Bellingham, and they are building maps to prioritize local spawning streams for applying the new soil treatment.
“It’s not every day that we get to say with certainty that we can solve such a complicated problem, but I feel hopeful about this one. This issue isn’t unique to King County, but King County is uniquely positioned to do something about it and our researchers are building a whole toolkit of strategies that will make cleaner, safer water a reality. ”
