Gardening on Brownfields:
Testing Your Soil
for Contaminants
Department of Agronomy
MF3192
Before gardening on a brownfields site, it is
important to test the soil for contaminants associated
with the historic use of the site. Commercial, industrial,
and residential uses may leave long-lasting contaminants that are potentially harmful to human health and
the environment. Heavy metals, as well as some organic
pesticides, are persistent in the soil.
What do I sample for? Laboratory analysis of
environmental contaminants can be expensive. To
avoid unnecessary costs, narrow possible contaminants
to analyze for.
While the use of leaded gasoline was phased out in
the United States in the mid-1970s and finally banned
by the Clean Air Act effective January 1996, lead is
the most commonly found metal in soils. Lead from
lead-based paint, the use of lead-containing pesticides,
and industrial uses also may contribute to lead concentrations in soils.
Arsenic is prevalent in soils as well, either occurring naturally, from the decay of arsenic-containing
bedrock, or introduced by the use of arsenatecontaining pesticides or through industrial activity.
Always analyze for soil lead concentrations and,
if the selected garden site is in an area where arsenic
occurs naturally in the soil, soil arsenic concentrations
should be analyzed as well — regardless of the former
use of the selected garden site.
Pesticides such as DDT (dichloro-diphenyltrichloroethane) and its breakdown product DDE
(dichloro-diphenyl-dichloroethylene) are persistent
in soils. Although the use of DDT was banned in the
United States in 1972, DDT can still be found in soils.
It was common to spray around foundations, including
the foundations of residential structures, to protect
against mice, rats, and other pests. Because of this,
it may be advisable to sample and test for DDT and
its breakdown products when garden beds are to be
established close to old residences or the foundation of
former residential structures.
Polycyclic aromatic hydrocarbons (PAHs) result
from incomplete burning of coal, oil, gas, and other
organic materials and are persistent in soil. If you
suspect or know of activities that may have generated
PAHs on the property where you want to garden, it is
wise to test for PAHs.
Brownfield Sites
The former use of a property dictates what
potential soil contaminants should be analyzed for. For
example, if a service station was once located on the
property you selected for growing crops, you may want
to have soils analyzed for potential contaminants such
as lead, arsenic, cadmium, mercury, and total petroleum
hydrocarbons. Depending on how much time has
passed since the service station was in operation, you
also may want to test for benzene, toluene, ethylbenzene, and xylenes (all constituents of gasoline, diesel
and fuel oils).
Examples of soil contaminants you may encounter
and their potential sources are listed in Table 1.
Table 1. Examples of soil contaminants and their potential
sources.
Soil Contaminants
Potential Sources
Lead
Past use of lead, lead-based
paint, and leaded gasoline
Other metals (such as
chromium, cadmium, and
mercury)
Industrial manufacturing;
mercury and cadmium from
waste oil; coal ashes
Arsenic
Copper/lead/arsenate
pesticides; waste oil; naturally
occurring locally
PCBs
Leaking transformers;
capacitors; electrical
equipment
PAHs
Incomplete combustion of
carbon-containing fuels (such
as wood, coal, diesel fuel)
Asbestos
Improper demolition or
remodeling of structures:
insulation; shingles; floor tiles
Persistent Pesticides
(DDT, DDE)
Used in the past to spray
for insects/rodents along
foundations
Chlorinated solvents
(TCE, PCE) and other
solvents
Dry cleaning operations;
former manufacturing
facilities
Kansas State University Agricultural Experiment Station and Cooperative Extension Service
2
Some research regarding the previous use of a site
selected for growing crops helps identify what constituents to analyze. For more information on historic site
uses and their potentially associated contaminants,
please see the K-State Research and Extension publication Gardening on Brownfields: Historical Property
Usage and Implications, MF3096.
In addition, consult the K-State Research and
Extension publication Gardening on Brownfields:
Obtaining Property Information and Site History,
MF3078 on how to research the historical use of a
property.
Where do I sample? Laboratory analyses for
contaminants can be expensive. Sample only areas of
the property where garden beds will be established.
If at all possible you should have the garden layout
planned before sampling soils. To keep costs down,
consider the following sampling strategies:
• Sample selectively: Sample areas of the selected
garden site showing stressed vegetation, low
areas (where surface waters tend to pool), around
residential structures, around former foundations,
and at locations where historical records identify
storage and/or use of potential contaminants (such
as drums, above-ground storage tanks for petroleum products, pesticides, etc.).
• Sample systematically: If there are no discerning
features on the property and the historic records
do not indicate any reasons to sample selectively,
consider using a grid pattern to identify sampling
locations. Establish the grid pattern depending
on size of the property and your sampling budget
(systematic sampling tends to be a bit more expensive as you end up taking more samples than with
a selective sampling approach). Grid patterns may
range from 10 feet by 10 feet to 100 feet by 100
feet. Samples are taken at intersecting grid points
(see Figure 1.)
Figure 1. Example of a sampling grid. Samples are obtained at
the intersection of the grid lines (dashed lines).
Sampling Location
•
Sample randomly: If your budget does not allow
systematic sampling, and you cannot sample
selectively, you need to select random sampling
locations. Obtain at least one sample per planned
garden bed and, if your property abuts a street and
garden beds are planned alongside that street, take
a few samples within approximately 20 feet of that
property boundary. You can start with a relatively
small number of samples and, if the analytical
results show elevated concentrations, go back and
take more samples.
How many samples do I need? Your need for
information and accuracy, the property size, and your
budget govern how many samples you take. The more
samples you take, the better you will understand the
potential soil contamination levels at your property.
If you sample selectively, i.e. sample identified
potential problem areas as identified visually or via
historic records, you will want to take individual
samples. For other areas of the property, especially
when sampling on a grid, it may be adequate to
obtain a number of composite samples. Gather these
composite samples by collecting several individual
samples and mix equal parts of each sample to form
one composite sample and repeat the process until you
have the area you want to sample covered. While this
is more economical, it may mean a smaller, localized
area of contaminated soil will not be identified as such
because an average contaminant concentration over a
larger area is generated.
The analysis of some constituents, such as pesticides, can be quite expensive, while analysis for metals
is relatively inexpensive. If warranted, a combination of
composite and individual samples could be obtained,
depending on budget and need for accuracy.
To what depth do I sample? When sampling soil
for contaminants, representative samples need to be
taken in order to obtain good analytical results. This
means the sample should be made up only from soil
from the location and depth you intended to sample;
no other soil should be mixed in. Sample depth should
be governed by the rooting depth of the crops to be
grown. Most leafy vegetables (chards, lettuce, spinach,
etc.) do not exceed a rooting depth of 6 inches (≈ 15
cm) under good growing conditions, i.e. sufficient
moisture and good soil structure (not too clayey or
sandy). Tomatoes root deeper, averaging 1 foot under
good growing conditions, and larger root crops tend to
fall in the same category. Depending on what you grow,
taking a soil sample from ground surface to a depth of
either 6 inches or 12 inches will be sufficient.
Kansas State University Agricultural Experiment Station and Cooperative Extension Service
3
How do I sample? The following tools are needed
for sample collection: clean trowel, shovel or spade, and
a clean plastic bucket (for compositing samples only).
Note: When sampling for metals, use only steel tools.
Start with clean sampling tools and clean all sampling
tools with soap and water between each sample location. You do not want to carry over potential contaminants from one sample location to the next as this will
influence the test results. If you touch the samples
with your bare hands, make sure you clean your hands
between sample locations. If you wear disposable gloves
for sample collection, put on a clean pair at every
sample location.
If sampling for metal analysis, use clean zippertype sandwich bags for sample storage. For anything
else, use containers provided by the laboratory that
will analyze your samples. Note: some samples require
refrigeration and storage at 39.2 degrees Fahrenheit (4
degrees Celsius), i.e. they need to be stored in a cooler
filled with a bag/bags of ice immediately on collection
until analysis by the laboratory. The laboratory that
analyzes your samples will tell you what samples to
keep cold and what sample containers to use for the
specific constituents to be analyzed. Always submit
the samples to the laboratory as soon as collection is
finished. Be sure to ask the laboratory for instructions.
Who should take samples? If you are uncomfortable taking soil samples for environmental contamination analysis yourself, you have potentially several
options.
• Ask local government. If the local government
owns the property, ask if environmental soil
sampling could be performed for the property. Your
local government may have an EPA brownfields
grant under which they may be able to perform soil
sampling.
• Ask the state environmental agency or
regional EPA office. Your state environmental
agency and/or your regional EPA office
can perform soil sampling via the Targeted
Brownfield Assessments/Brownfield Targeted
Assessments program. These assessments are
performed free of charge, but are available
only if you are an entity of local government
or a not-for-profit organization. Please see
www.gardeningonbrownfields.org/p.aspx?tabid=33
for a list of state and EPA brownfield contacts.
• Ask your local health department. Your local
health department may be able to take soil
samples for you.
•
•
Consult an environmental laboratory. If you are
using a local laboratory for sample analysis, ask if
they have a technician who may be able to obtain
the required soil samples. You likely will have to
pay extra for this service.
Hire an environmental consultant. A consultant
can obtain soil samples at the property.
Soil test resources
Some universities offer soil testing for lead, other
metals, and arsenic.
Brooklyn College, New York http://www.brooklyn.cuny.
edu/web/aca_centers_esac/110901_Soil_Brochure.pdf
Cornell University, New York:
http://cnal.cals.cornell.edu/analyses/index.html
Iowa State University:
http://soiltesting.agron.iastate.edu/faq.html
Kansas State University: for pricing: http://www.
agronomy.k-state.edu/services/soiltesting/documents/
soil-testing-lab/FARMER_AND_GARDENER_
PRICE_LIST.pdf, for shipping and other
information: http://www.agronomy.k-state.edu/
services/soiltesting/shipping-information.html
Penn State Cooperative Extension: http://agsci.psu.edu/
aasl/soil-testing/environmental-soil-testing
Rutgers University, New Jersey Agricultural
Experiment Station:
http://njaes.rutgers.edu/soiltestinglab/services.asp
University of Connecticut Soil Testing Lab:
http://www.soiltest.uconn.edu/price.php
University of Delaware Soil Testing Program: http://
ag.udel.edu/dstp/Gen%20Program%20Info.html
University of Maine Soil Testing Lab: http://anlab.
umesci.maine.edu/soillab_files/prices/soiltest12.pdf
University of Massachusetts Soil and Tissue Testing
Laboratory: http://soiltest.umass.edu/services
University of Minnesota Soil Testing Lab: http://www.
extension.umn.edu/garden/yard-garden/soils/docs/
lawngardensoilsampleinformationsheet20131.pdf
University of the District of Columbia, Washington
D.C.: https://www.udc.edu/college_of_urban_
agriculture_and_environmental_studies/
soil_testing
University of Vermont, Agricultural and
Environmental Testing Laboratory:
http://pss.uvm.edu/ag_testing/?Page=forms.html
University of Wisconsin: http://uwlab.soils.wisc.edu/fees/
Kansas State University Agricultural Experiment Station and Cooperative Extension Service
Glossary
Brownfields site: Previously used, underutilized/
blighted, potentially contaminated property.
Individual sample: A sample obtained at a specific
location and depth.
Composite sample: A sample made up of several
individual samples.
Metalloid: A chemical element with properties in
between those of a metal and a nonmetal. Arsenic is a
metalloid.
Heavy metals: Any metal heavier than iron; examples
of heavy metals are lead, cadmium, and mercury.
Sabine E. Martin, Ph.D.
Professional Geologist
Hydrogeology, Brownfields, and Redevelopment
Representative sample: A sample representing only
the location and depth from which it was obtained.
Ganga M. Hettiarachchi, Ph.D.
Associate Professor
Soil and Environmental Chemistry
Brand names appearing in this publication are for product identification purposes only.
No endorsement is intended, nor is criticism implied of similar products not mentioned.
Publications from Kansas State University are available at: www.ksre.ksu.edu
Publications are reviewed or revised annually by appropriate faculty to reflect
current research and practice. Date shown is that of publication or last revision.
Contents of this publication may be freely reproduced for educational purposes.
All other rights reserved. In each case, credit Sabine E. Martin, Gardening
on Brownfields: Testing your Soil for Contaminants, Kansas State University,
December 2014.
Kansas State University Agricultural Experiment Station
and Cooperative Extension Service
K-State Research and Extension is an equal opportunity provider and employer.
Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June
30, 1914, as amended. Kansas State University, County Extension Councils,
Extension Districts, and United States Department of Agriculture Cooperating,
John D. Floros, Director.
MF3192 December 2014