Soil Sampling for Lead,

      Cadmium, and Arsenic

This document provides guidance on how to sample soils contaminated with lead, cadmium or arsenic. The directions would change somewhat if the soils were contaminated with other materials.

The equipment you will need:

Where and how you sample depends on what question you want to answer.

Children are the most sensitive population for heavy metal contamination, because they often play in the dirt, they often eat dirt (about 10 percent of children actually eat dirt by the handful), their stomachs are more acid than adults’ (thus absorbing more heavy metal, proportionately), and their growing bodies and nervous systems are more sensitive to metals. If you have small children, you should sample in the areas in which they play.

Use a clean plastic or stainless steel spoon or scoop and collect soil from areas where children play. Remove any sticks or other debris from the area, and combine soil from several spots in each play area. Gather a small, approximately equivalent amount of dirt from four to 8 spots, sampling only the top two inches of soil. This is called a composite sample. In total, you should have at least one-half cup of soil. Store the soil in a container such a zip lock bag or small clean glass jar. Label the container, and draw a rough map of the property, noting where the sample was taken.

Clean your sampling equipment by scrubbing with detergent, and rinsing at least three times in clean water. Repeat the sampling process in other child play areas.

Gardens are a concern because we are often eating the produce from them. However, be aware that different gardening methods can lead to greater or lesser uptake by plants. Furthermore, different vegetables take up different metals differently. Arsenic appears to be mostly in roots and stems, and less in leaves and fruits, while cadmium appears to be mostly concentrated in leaves. There is no hard and fast connection between the heavy metals in garden soil and the heavy metals in vegetables.

Gardens can be sampled in much the same way as child use areas, but you should be sampling the first six to 8 inches of the soil (the root zone) instead of the top two inches. A stainless steel bulb planter can be used for this kind of sample. Make sure it is REALLY clean before you start and after every composite sample.

Take a composite sample by removing the plant debris on the surface, then sampling the top 6 to 8 inches of soil. Combine at least three samples from each garden. Then label the sample and mark your map as to its location. Another way to sample gardens is to composite several gardens—but be aware that metal contamination varies a great deal over small distances. You may have one garden that is very bad while others are very good. Mixing them together may conceal the bad garden.

Property/Real estate assessments are asking whether the property as a whole is contaminated. To determine this, you should take a random sampling over the entire property of at least ten separate, non-composited samples. They will give you a statistical assessment of the property. Don’t forget to use the map to note where samples are taken.

Assessments for clean topsoil are asking whether a large amount of topsoil is below levels of concern. Usually topsoil is produced in very large quantities. Changes in composition occur between the beginning and the end of the production run. The best way to sample is to take spoonfuls of material at regular intervals from the beginning to the end of the pile. Ten to 20 sub-samples should be taken and combined into one composite sample.

Worst-case assessments are based on picking the few places on the property where the highest concentrations are expected. On Vashon-Maury Island, the heavy metals derived from the Tacoma Smelter plume, and the highest concentrations are found on upper, southward-facing slopes. Samples should be taken at the foot of the largest trees, where the soil appears to be undisturbed on the south side, and preferably at elevations of at least 100 feet. If the property is at low elevation, try to get as high as possible for the sampling. No compositing is required. Two or at most three samples will give you a reliable worst-case sampling.

The advantage to doing a worst-case assessment, is that if your numbers are relatively low, you know that there is not likely to be a problem on the property. Worst-case assessments can be most useful for those seeking to purchase property or those who suspect that their overall levels of contamination are low.

Recovery of costs under the Model Toxics Control Act. It may be possible to sample in order to recover cleanup costs. There are specific requirements for remediation, sampling and analysis. See http://www.ecy.wa.gov/pubs/9406.pdf.

Storage and Analysis

Once you have your samples, you should store them in a refrigerator.

All your work sampling will be worthless if your laboratory is not good at analyzing these kinds of samples. You need to tell them to:

Call your laboratory ahead of time to assure that they can do this kind of analysis. They can supply you with sample containers and chain-of-custody documentation. Also ask what their turnaround time is—how long it will take to get your results. Find out how they want the samples delivered. To have samples compliant to the EPA standards you should pack them with ice packs or ice, and send them via courier to the lab in a cooler. Make sure that you include your name and contact information inside the cooler, along with a description of the samples and what tests you want done.

If you only want the sample results for your own information, most labs will accept soil samples sent to them via the U.S. Mail. This is the cheapest way to send samples, and it will not affect the results, but you will not have a chain of custody record, so the sample results will not comply to the US regulations.

Caveat Emptor. Relatively few laboratories can do a good job with these kinds of samples. We have audited laboratories in the area, and those passing our audit criteria are found at good labs.

If you have any questions, feel free to call the Institute for Environmental Research and Education (206-463-7430) or email to staff@iere.org, or you can call the Heavy Metals Remediation Committee of the Vashon-Maury Island Community Council. May Gerstle chairs this committee, and her phone number is 206-463-0974.

This webpage supports the Heavy Metals Remediation Committee of the Vashon-Maury Island Community Council
It is funded in part by Island Remediation and Public Participation Center through a grant from the Washington State Department of Ecology