Soil Sampling for Nutrients, Heavy Metals and Pesticides
First, I feel as though I must apologize for not writing more often. In an effort to make it more of a habit I’ve decided to simply write a quick post about pages from our website to share more about the services and reveal relevant stories. I’m starting with soil sampling for heavy metals, pesticides, and nutrients from our Soil Testing page.
For some reason I’m sure a web analyst could explain, most our soil sampling requests have come from San Francisco, San Mateo, Marin, and Sonoma counties. We routinely collect soil samples and have them analyzed for nutrients, heavy metals and pesticides.
Soil nutrient analysis is ideal for people starting a farm, orchard, or even a simple backyard garden. Often times nutrient analysis is performed as part of a pre-purchase testing protocol for farm or ranch land. This is a fairly basic screen that looks at many common soil parameters such as pH, salinity, organic matter, nitrogen, phosphorous, potassium, magnesium, calcium, sodium, sulfur, zinc, iron, chloride, etc. This information is used to see if the soil would require any additional nutrients or fertilizers to support your ideal crop. Lab analysis for nutrients costs less than $100.
Our most common soil pollutant screens include heavy metal and pesticide screen tests developed by the US EPA. Our basic heavy metal soil screen will report levels of detectable arsenic, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc. These metals are often present in soil as a result of naturally occurring mineral deposits around the property, but sometimes there are high spikes in heavy metals as a result of human activity.
Old dumping grounds or leaky underground storage tanks can be a source, and perhaps the most common source around the San Francisco Bay is lead-based paint. EPA “target” housing for lead-based paint is anything built before 1978. What happens when you paint a house? The first step is to scrape off all the peeling, flaking paint. Now there are more stringent rules in place to safeguard workers and occupants during painting activities, specifically the EPA Renovation, Repair and Painting (RRP) rule. However, we frequently find elevated levels of lead in soil immediately around older homes… and this can be a concern for homeowners wanting an edible backyard garden.
Here is an example of lab results from a clean agricultural parcel in Sonoma County.
Pesticide screens for soil are also a common request. On this job we took two composite samples from outside (yard) and under the home (crawlspace). There are quite a few screens for pesticides in soil, but this one looked for the older, more persistent chemicals you may have heard of… such as heptachlor, aldrin, dieldrin, DDE, DDT, chlordane, etc. If you read Silent Spring or Living Downstream you’ll recognize these notorious pesticides that linger in soil for decades.
Outside in the lawn area, only a few traces were identified:
However, under the home was a different picture. Beneath older homes, people used to dump these persistent pesticides on the soil to discourage insects and rodents from taking harborage in the crawlspace. This space is devoid of rain and sunlight, and natural processes that degrade and transport pesticides from soil do not occur as quickly in crawlspaces. As part of our work we frequently find ourselves crawling through crawlspaces and disturbing all the fine particulates in the soil. These results sent chills down my spine – and confirm why it’s necessary to fully suit up and don a respirator before entering a crawlspace.
Heavy metals and pesticides in soil do have clear exposure pathways to building occupants. Windblown dust, hand-to-mouth through gardening and air infiltration from the crawlspace are three pathways that come to mind. Unless you’ve had soil testing for heavy metals, pesticides under your home, I strongly discourage anyone from entering a crawlspace without at least a half-face respirator and some protective clothing so you don’t inhale contaminated dust or cross-contaminate indoors from dust on your clothes.
Next time you consider gardening, consider soil testing for heavy metals, pesticides, and nutrients.
Thanks for tuning in!