Serina Diniega always wanted to plant an avocado tree at her Altadena home, but now she worries the creamy green fruit might pose a threat.
Her yard was scorched in the Eaton fire as her block went up in flames. The planetary scientist’s house survived, but unseen contaminants could be lurking in the soil.
“What can I do to keep that tree healthy, hopefully be able to eat the fruit a number of years down the line without worrying about whether or not I’m poisoning my family?” she wondered. The internet was full of opinions, but science was scarce.
So when a DIY soil detoxification workshop came up at a local nursery, she jumped on it. Many others did too; roughly 40 people were waitlisted for the three-hour class led by SoilWise, a landscaping, education and consulting business. Once a niche subject, the firestorms of January have put a spotlight on soil health, as residents wonder if their yards are safe for their children to play or if their home-grown tomatoes are OK to eat.
Learning how plants, compost and other materials combat contamination can be a source of empowerment in the face of disasters that are beyond individual control, and proponents say the approach is more environmentally friendly than conventional alternatives. For some, the tools are also a backstop against inadequate government help.
Harnessing the power of nature
The typical approach to dealing with contaminated dirt is stripping away the topsoil. As part of its post-fire cleanup, the U.S. Army Corps of Engineers said it would scrape up to 6 inches from fire-destroyed homes.
But in many cases, large swaths of yards and gardens were left out.
That’s not real remediation, SoilWise’s Genesis Sandoval said during the recent workshop at Theodore Payne Foundation, a native plant nursery and education center in Sun Valley. “It’s really just moving a problem from one place to another place.”
It historically has ended up on the doorstep of marginalized communities, she added.
Nature provides other tools, though.
Heavy metals such as lead don’t break down, so they have to essentially be trapped in certain types of plants, minerals and compost, SoilWise co-founder Lynn Fang said.
There’s evidence that buckwheat and bush sunflower can take up lead, and saltbush can ensnare arsenic, Fang said, also name-checking corn, squash and cucumber for their ability to sequester contaminants such as dioxins.
Biochar, a charcoal-like material that some people mix in their garden soil, has pores that can capture metals, Fang said, adding that there’s also research indicating it can suck up PFAS, or so-called forever chemicals.
Some nasties, including dioxins, can be broken down by fungi and microbes. Oyster mushrooms excel at chomping down contaminants such as hydrocarbons — even cigarette butts. “They’ll turn it into basically, like, mushroom,” Fang said.
Workshop attendees got down and (literally) dirty making “ecological filter socks,” stuffing things like oak mulch and crushed oyster shells into burlap sacks.
The nitty gritty
The broad strokes of natural detoxification are easy to grasp, but the particulars not so much. For example, in the family of minerals known as zeolites, one might be great at trapping lead while another may not be effective.
Once the absorptive socks or plants have done their job, they may pose a risk themselves. The workshop leaders discussed the possibility of creating a “sacrificial zone,” potentially under trees, where materials such as lead-laced plants are composted.
“It can be a lot to take in, especially because soil health is a topic that is becoming more popular, and we’re not really used to soil health being taught or being exposed to soil health in as much depth,” SoilWise’s Maggie Smart-McCabe said.
What lies beneath
After the Eaton and Palisades blazes, federal and state disaster agencies refused to pay to test soil for contaminants on scorched lots — a practice employed in virtually all wildfire recoveries in the recent past.
So researchers with USC in March began to offer the service to L.A. County residents. The free program has focused on screening for lead, a potent neurotoxin that’s especially dangerous for kids.
So far, most of the roughly 3,000 samples residents have submitted fall below California’s level of potential concern, 80 parts per million.
But a substantial proportion are above that. Some are even in 1,000s, which the state classifies as hazardous waste.
Lead poses a bigger problem in Altadena than in Pacific Palisades, largely because of the former’s overall older housing stock, built when homes were coated in leaded paint, said Josh West, a professor of earth sciences and environmental studies at USC.
Yet Palisades residents generally have more money to deal with cleanup.
“The burden that people in Altadena are facing is a much greater proportion of their average income,” West said.
Mucked up soil in L.A. didn’t begin with the fires
Emissions spewed by factories and innumerable cars also have left their invisible mark on the soil across our urban landscape. So why is soil health suddenly getting so much attention?
Sandoval said the blazes “affected a lot of privileged communities,” pointing to a possible explanation rooted in racial and socioeconomic inequity.
For close to a century, a battery recycling plant released heavy metals into communities in South and East L.A., “while government agencies were unresponsive to this community health crisis,” according to Prospering Backyards, an initiative launched to address the pollution.
More than 80% of soil samples tested in 2022 — seven years after that plant closed — were above the 80 ppm threshold for lead, according to a recent report.
Prospering Backyards has tested applying zeolites (the lead-trapping minerals) to the ground along with layers of mulch and compost. A report from last year found the technique helped reduce exposure to contaminants, according to Maru García, project lead for Prospering Backyards.
That research, which predates the fires, is now being tapped to meet the current crisis.
Galvanized by interest after January’s fires, García’s group helped develop “healing toolkits,” essentially guides focused on dealing with contaminants. They also began holding workshops that she said addressed not just practical concerns but emotional ones.
Many expressed fear and overwhelm. Others were grappling with anger and mistrust. Some couldn’t put a name to their feelings.
“I saw just the need to go through this,” García said. “And for me it was kind of a confirmation that treatments that are approaching the remediation by itself are not really bringing the whole solution.”
Bringing in the feelings
That was true at SoilWise’s workshop as well, where anxieties and collective grief commingled with hope.
“I worry about the chickens,” said Lelas Stone, reflecting on what she hoped to learn. Her Altadena home didn’t burn but others nearby did. Soil testing revealed a high lead level of 110 ppm.
Citing an expert, Fang said chickens pecking in soil with high levels of lead and arsenic will accumulate the toxins in their bodies and eggshells. She advised people not to cook the eggs in their shells.
Others expressed similar anxieties about wanting to keep their loved ones — from pups to parents — safe. Yet attendees seemed to be able to reach beyond the current sorrow to connect with soil on a visceral level. After all, their passion for gardening predated the tragedy.
Diniega teared up recalling the first bee she saw in a seared Altadena neighborhood, about a month after the blaze was put out. Some trees in her garden whose roots survived are rebounding.
“It’s a celebration anytime anything comes back,” she said.
Theodore Payne Foundation plans to hold an online version of the DIY soil remediation class in October.
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