LOCATION AND RELEVANCE: A FIELD AND LAB EXERCISE IN MAPPING SOIL LEAD CONTAMINATION NEAR LAWRENCE UNIVERSITY

We describe here a lab exercise based on mapping lead contamination of urban soils near Lawrence University’s campus in Appleton, WI (population ~70,000). This particular exercise has run for four years and has involved hundreds of introductory environmental science students as well as scores of intermediate-level geochemistry students. The exercise has both content and skills goals. The content goals are: parsing out the main source(s) of lead contamination, understanding the deleterious effects of lead exposure, and proposing solutions to mitigate contaminated properties. The skills goals include: use of XRF techniques, field data collection and processing, and geospatial mapping using GIS.

In the past four years our students have analyzed ~400 surface soils in the neighborhood near Lawrence. Like many larger cities, Appleton has a historic city-center. However, it is has no high-density housing or commercial districts and has not seen heavy traffic. These differences make for interesting comparisons with similar studies conducted in larger cities (e.g. Chicago, Milwaukee, Boston). At each property 3 integrated-samples were taken, one adjacent to the front of the house, one in the front lawn, and one between the road and sidewalk. Contaminated properties show a clear decay in lead concentration away from the homes, suggesting that exterior paint is the likely source. Students correlate building and property traits (e.g. structure age, exterior type, exterior condition, and assessed home value) with soil lead concentrations and map these data for geospatial patterns. High lead concentrations (averaging over 1,000 ppm near the structure) were associated with aging, poorly maintained structures as expected. However, a number of well-maintained structures also show substantially elevated concentrations. These results require the students to adopt a more sophisticated and nuanced view of the sources of contamination and methods of mitigation. Overall the exercise creates a rich learning environment that is literally in their own backyard. Moreover, the students feel part of a something larger by contributing to an on going study. Many students, who have worked on the project in the introductory and intermediate courses have gone on to carve out individual senior capstone research based upon this project.