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.