Hypothesis
It is
well known that lead concentrations from old house paint and combustible
gasoline emissions can reside in soils for long periods of time. My hypothesis
is that there are high concentrations of lead in soils next to my old house and
that there is the same in soils located next to high traffic density street
intersections in Springfield, Missouri.
I also think concentrations of lead in the soils is proportional to
traffic density.
Procedure
I
visited the Springfield, Missouri Traffic Engineer, talked to him about my
project and obtained a 1997 street traffic density pamphlet for
Springfield. I studied the pamphlet and
chose eight traffic intersections. Each
pair of four sets of intersections was similar in traffic density but different
than the other pairs. The highest
traffic density pair was classified as 1; the next highest, 2; the third
highest, 3 and the lowest, 4. Even though the classification is based on
present traffic densities when no lead is present in gasoline, the traffic
engineer assured me the intersections that were chosen would have been
classified in the same relative categories in the past when gasoline contained
lead. The following street intersections used in this project with the above
classification and location site numbers were: Kansas Expressway--Sunshine
Street (1A) and Battlefield--Glenstone Street (1B); Campbell Street--Chestnut
Street (2A)
and Atlantic Street--Kansas Expressway (2B); Cherokee Street--National Street (3A) and Battlefield--Jefferson
Street (3B); Campbell
Street--Commercial (4A) and Grant Street--Talmage Street (4B).
Soil
samples were collected at each of the above sites. Each sample was collected at an undisturbed site on the north
side of the intersection. Samples were
collected this way to avoid turnover of soil at the location and because the
prevailing wind in this area was from the south. Samples were collected as close to the intersection as possible
and from 0-2 inches depth with a garden hand hoe. Each sample was labeled and placed in a plastic sandwich
bag. The collection location of the
soil was modified for the 4A site since there was indication of old paint spillage
near this location. The sample
representing this location was collected about 40 feet north of the
intersection at a location higher in elevation that the area of paint spillage.
Samples were dried for further treatment.
I
visited the Springfield Health Department and received some important books and
pamphlets on lead concentrations in soils contributed by the paint from older
houses. Also, I received a core device.
This device would allow me to collect soil from different depths in soil
for the purpose of determining variations of lead concentrations with
depth.
I
collected soil samples from areas on the property on
which my house is located. My house was built in 1912 and I expected the
old paint, which fell to the ground nearest my house would result in elevated
concentrations of lead in the soils. At
one soil collection site near my house the core device was used to collect
three samples at 0-1 inch depth, 1-2 inch depth, and 2-3 inch depth. These samples were labeled as SPL 1",
SPL 2", and SPL 3", respectively.
Three control samples collected the same way in front of my house were
labeled CSPL 1", CSPL 2", and CSPL 3", respectively. In addition, four samples were collected
from the house at one foot intervals.
The first sample was collected as close to the house foundation as
possible. The samples were collected
with a hand hoe from about 0-1'' depth and placed in a plastic sandwich bag.
These samples were labeled HS1-HS4, respectively. In addition, a control sample labeled HCS was collected with the
same procedure from the front of the house.
These samples and street intersection samples were dried in the open air
in my basement.
All
dried soil samples representing street intersections and house locations were
disaggregated and passed through a 40 mesh sieve. The sieved portion of each sample was weighed to approximately
0.5 grams and transferred to a centrifuge bottle. The exact weight for each sample was recorded. To each sample 10 milliliters of 3N nitric
acid was added. All samples were placed
in a heated shaker bath and shaken for 5 hours at 80 degrees C. The samples were centrifuged and the liquid
portion transferred to analyses bottles.
The lead concentration for each sample was determined by atomic absorption
analysis.
Results
The
concentration of lead in the soil of each street intersection and house yard
sample is shown in the project Data Table. The data
from this table are displayed in Graphs 1, 2 and 3.
Graph 1 shows the concentration of lead in ppm in
the soils collected from street intersections (50-2,679ppm). The concentrations are proportional to the
traffic densities. Toxic concentrations
usually refer to toxicity to children.
The latest toxic value for lead in soils varies from one source to
another. The U. S. Environmental
Protection Agency (EPA) proposes lead concentrations in soils higher than 500
ppm as toxic. The U. S. Department of
Housing and Urban Development (HUD) considers 500 to 1,000 ppm lead in soils to
be toxic and in Sweden, concentrations of greater than 80 ppm are toxic for
play areas. It is interesting to note
that many of the soils at the street locations in this study have lead
concentrations that are toxic to children.
Fortunately, these areas are not where children play.
The concentrations of lead in the soils at my house
are plotted on Graph 2. Results indicate extremely high concentrations of lead in the
soils adjacent to my house. Concentrations
of lead in all samples (944 and 1824 ppm) are higher than the values set by all
the regulating agencies mentioned above. From the results of the analysis of
samples collected at the surface area adjacent to my house there is a trend of
increasing lead concentrations away from the house to the third sample and a
decrease concentration at the last sample at 4 feet from the house. From the core sample analysis, there is a
higher concentration of lead at the deepest area in the soil for that site. The
data in Graph 3 shows the concentration of lead in
the control sample for the surface samples collected away from the house and
control samples for core samples. There
is a much lower concentration of lead in the control samples than in each corresponding
test sample. The trend of lead
concentration with a function of depth is similar in the control and test
samples of the core soil.
Conclusions
Concentrations of lead in the soils at street intersections increased
with increasing traffic densities. Most
of these concentrations are toxic to children according to Regulation Agencies
including the EPA. The same is true of
lead concentrations in the soils adjacent to my house. These results may suggest further studies of
lead concentrations in soils in play areas near high traffic density
streets. Also, it might be important
for families with young children living in old houses to have the soil in their
yards checked for elevated lead concentrations. A deck covering the soil or river rock placed on top of a plastic
liner covering the area adjacent to houses with elevated lead concentrations
would be an excellent way to protect children from contacting the soil.
Acknowledgements
I wish to thank Mr. Earl Newman, Traffic Engineer of
Springfield, Missouri for giving me helpful suggestions concerning this
project. I also wish to thank Mr.
Patrick Scott from the same Department.
I want to acknowledge Mr. Kelley Derrick of the Health Department Vector
Control for Lead for Springfield who gave me pamphlets on the effects of lead
in soils. I want to thank Missouri State University for the use of their facilities, especially the
Department of Geography Geology and Planning at Missouri State for the use of a soil
sieve and analytical balance and the Chemistry Department for use of an Atomic
Absorption Analyzer. Also, I wish to
thank my father, Dr. Erwin Mantei for suggestions concerning this project.