Shedding Light on Homegrown Toxins: What Hides Beneath Your Lawn
Contaminated Ground Soil Prevalent in L.A.: Solutions for Remediation, Applicable for Homes Undamaged by Fire
Worried about the impact of the Eaton and Palisades wildfires' debris on your soil? Experts assure us that despite concerns, there may be some unpleasant truths lurking beneath the ground. Let's dive into the circumstances we've unearthed in post-fire Los Angeles:
- Soil tests under eight affected burn sites paint a mixed picture. Places like a burned Malibu home and a 100-year-old Altadena property displayed lead levels far above the State's limit of 80 parts per million, checking in at around 180 ppm – double the state's standard. However, in nearby communities, lead levels were significantly lower, between 23 and 40 ppm.
- L.A. soil sediments have been contaminated for decades by chemicals from industries, agriculture, home-improvement goods, and even residential fertilizers. Fire damage indubitably worsened the situation but, with decades of pollution, it's challenging to pinpoint specific toxins initially existing in the soil.
- Landscape designer Shawn Maestretti of Studio Petrichor, who lost his Altadena home, shares a stark warning: "You've always been playing in it." Removing soil is the quickest method to get rid of toxic soil, but considering the sheer scale of the task, it may not be sustainable.
- As an alternative approach, methods like in-place remediation are on the rise. This strategy aims to eliminate contaminants without removing the soils, focusing instead on removing the toxins from the soils. One organization at the forefront of this advancement is the Centre for Applied Ecological Remediation, offering classes and guidance for those eager to learn more about bioremediation.
Engaged gardener or not, it's wise to testing your soil for heavy metals, nutrients, minerals, and pH levels - all for less than $200. You can find a range of soil testing companies throughout Southern California.
In the sections below, we'll detail the assessments, explain how to interpret your test data, and offer expert tips for reviving your soil.
Unpacking the Results
We tested the soil in LA's burn sites before scraping, capturing a snapshot of existing toxins in the soil. We deployed a hand trowel to gather samples in Altadena, Pacific Palisades, and Malibu in March. These locations represented properties with both burned and standing structures. Each property's soil was amalgamated in a plastic bag, simulating a typical homeowner's method for soil sampling. Wallace Laboratories in El Segundo performed the tests.
Test results were all over the map but unearthed one consistent finding: all but one property displayed high pH levels, indicative of increased alkalinity due to ash's alkaline nature.
Dealing with the Sally Strange: pH Levels in LA’s Soil
Southern California's soil tends to be alkaline, but the ideal pH value is generally believed to be between 6.5 and 7.2. Once the pH level exceeds 8, plant growth suffers due to the roots' inability to access the nutrients required for survival. Our tests found pH levels ranging from 7.7 to 8.2.
You can tackle high pH levels by incorporating gypsum into your soil and avoiding substances like crushed concrete that may raise the pH levels to toxic levels for plants.
Tresspassing Toxins: Metals Hiding at Elevated Levels
Our results revealed significant lead levels at two properties, a burned home's Malibu planting strip and a well-landscaped 100-year-old Altadena property. Both sites showed lead levels near 180 ppm, more than twice the state limit.
Lead, like other heavy metals, persists indefinitely in soil and accumulates over time. Acceptable lead levels vary by state, with the federal limit recently reduced to 200 ppm due to increasing evidence regarding lead's harmful effects on humans. Plants readily absorb these toxins, making it risky to consume root vegetables or leafy greens grown in lead-tainted soil.
Sources of lead in older homes may include lead-based paints, widely used in homes until the 1978 ban, and common products like certain formulations of Ironite fertilizers.
Alternatives to Scraping: Transforming Toxic Soil
For homeowners opting in for cleanup, the Army Corps of Engineers has committed to removing six inches of soil from burned patches and transporting it to designated toxic landfills. The method raises concerns about the removal of valuable topsoil, which is essential for germination and nutrient provision.
Maestretti and Leigh Adams of Studio Petrichor are working tirelessly to safeguard the soil they nurtured around their Altadena properties, both of which were destroyed in the Eaton fire. Though they plan to have the burned areas cleaned, they're hesitant to scrape the rest of their yards.
Maestretti champions the health of his native plants surviving despite the fire, attributing their resilience to mulch and hugelkultur mounds, a mix of logs, wood chips, and compost.
Adams envisions rebuilding a smaller home and dedicating the rest of her property to the practice of bioremediation, utilizing amendments such as mulch, fungi, zeolite, various plants like sunflowers and corn, and phytoremediation – a process in which plants absorb toxins from the soil. This approach minimizes toxin exposure during the remediation process, making it a more sustainable option.
Fruits of Compromised Soil: Navigating Preparation, Planting, and Consumption
After residing in contaminated soil for years, it's essential to thoroughly test your soil before planting. Once you understand the situation, there's a range of soil repair techniques available to you. Davis recommends implementing bioremediation methods, gradually transforming soil through organic amendments and selected plant species.
Those seeking a quicker fix, however, may choose to scrape their contaminated land, entrusting the task to the Army Corps of Engineers. While this option offers short-term relief, it might come at the cost of subtracting essential nutrients from the soil, potentially compromising future plant growth.
If you're growing food, take extra care. Root vegetables, fruits, and leafy greens offer a clear path for toxins to enter the human food chain. As you gradually heal your soil and test the soil every few years, consider implementing raised beds to isolate edible plants from the potentially toxic subsoil.
Sources
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671098/
- https://www.tandfonline.com/doi/abs/10.1080/09644019909373314
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2228278/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5361620/
- https://www.atmosphere.com/exposure/ восстановление_золень
Glossary
- Arsenic: A naturally occurring semimetal and highly toxic compound found in various sources, including industrial emissions and pesticides.
- Bioremediation: The process of eradicating or reducing pollution using biological agents like microorganisms or plants.
- Gypsum: A mineral composed primarily of calcium sulfate dihydrate (CaSO4·2H2O) that can help reduce soil alkalinity and improve soil structure.
- Phytoremediation: The secondary metabolism of selected plants to eliminate or reduce contaminated substances, often heavy metals, from the soil, water, or air.
- Zeolite: A mineral composed primarily of aluminosilicate, possessing a stable 3-dimensional structure that can encapsulate contaminants like heavy metals in its crystalline structure.
- List of Vocabulary: soil pollution, remediation, ecological health, heavy metals, lead, arsenic, cadmium, particulate matter, industrial activities, chemicals, fertilizers, vehicular emissions, construction, phytoremediation, bioremediation, soil testing, selective planting, soil amendments, gypsum, pH levels, biochemists, soil scientist, toxins, pollinators, ACTH, topsoil, subsoil, raised beds.
- Post-wildfire debris has raised concerns about potential toxins in the soil, with experts urging caution.
- Soil tests from burned sites in Malibu and Altadena reveal high levels of lead, exceeding the state's limit by up to double.
- L.A.'s soil has been contaminated for decades due to industrial, agricultural, and residential activities, making it challenging to pinpoint specific toxins existing in the soil.
- Landscape designer Shawn Maestretti warns that residents have always been exposed to these contaminants, advising caution in soil removal due to the scale of the task.
- In-place remediation, which aims to eliminate contaminants without soil removal, is gaining popularity as an alternative approach to soil remediation.
- The Centre for Applied Ecological Remediation is spearheading this advancement, offering classes and guidance on bioremediation.
- It's advisable for homeowners to test their soil for heavy metals, nutrients, minerals, and pH levels before planting to ensure soil health and safety.
- Test results from Los Angeles's burn sites show consistently high pH levels, indicative of increased alkalinity due to ash's alkaline nature.
- High pH levels can damage plant roots, making it difficult for them to access essential nutrients for growth.
- Sources of contaminated soil may include toxins from lead-based paints, certain fertilizers, and even residential landscaping.
- Maestretti and Leigh Adams, members of Studio Petrichor, promote the health of native plants that survived the fire through methods like mulch and hugelkultur mounds.
- Homeowners have the option to scrape contaminated land or implement bioremediation techniques like amendments and selected plant species to gradually transform the soil.
