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After the Napa Fires, a Disaster-in-Waiting: Toxic Ash

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by Adam Rogers October 29 2017 read full Wired article here

By any measure, the fires that tore through Northern California were a major disaster. Forty-two people are dead, and 100,000 are displaced. More than 8,400 homes and other buildings were destroyed, more than 160,000 acres burned—and the fires aren’t all out yet.

That devastation leaves behind another potential disaster: ash. No one knows how much. It’ll be full of heavy metals and toxins—no one knows exactly how much, and it depends on what burned and at what temperature. The ash will infiltrate soils, but no one’s really sure how or whether that’ll be a problem. And eventually some of it—maybe a lot—will flow into the regional aquatic ecosystem and ultimately the San Francisco Bay….

…”Naturally occurring, lower-severity fires can have positive impacts,” says Kevin Bladon, a forest ecohydrologist at Oregon State University. The fires free up organic carbon and put nutrients like nitrogen and phosphorous into play. “But the really large, high-severity megafires that we’ve started to observe push the systems in a lot of cases too far.”

That means dangerously large algal blooms, so-called eutrophication that can eat all the dissolved oxygen out of a waterway, making it unlivable for everything else….’

…What makes these latest Northern California fires unique, though, is that they burned not just forest wildland but also cities. And the built environment burns differently. It gets hotter, and it leaves behind different remains. “All of a sudden you’ve got a lot of impervious surfaces,” Bladon says. “Water hits it and flows over. If there are burned materials sitting on the roads, that’s going to move very rapidly into waterways. We have no handle on that at all.” Ash science isn’t much more than a decade old; understanding urban ash science has never really been a necessity—but now megafires are coming to cities….

…The Regional Monitoring Program for Water Quality already watches what’s in the San Francisco Bay besides water. Some of its scientists now have a proposal to monitor the Napa River for what water watchdogs call “contaminants of emerging concern.” The field is new enough that they’re not even sure what they’re looking for yet—they’re going to use “non-targeted analysis” to look for anything unexpected. The San Francisco Estuary Institute already monitors dioxins, PAHs, metals, and other stuff in the bay, but only annually or semiannually.

That’s probably not fast enough….

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