SURFACE SOIL GEOCHEMISTRY OF ATLANTA, GA

Previous research from urban cities around the world have found elevated soil lead concentrations in many of the cities due to anthropogenic deposition of lead from industrial, transportation, and residential applications. The surface soils in cities exhibit extreme variability in soil-lead contamination because of heterogeneity of the soil and multiple anthropogenic input sources depositing over extended periods of time. Children, impoverished populations, and pregnant women all experience elevated health risks when exposed to land with elevated soil lead concentration.

The objective of the study is to create a prediction map of surface level soil-lead contamination for Atlanta, Georgia through the geochemical and spatial analysis of 1000 soil samples collected within the city’s urban environment through X-ray fluorescence analysis and spatial interpretations within ArcGIS. The project will test the following hypothesises: 1) Lead contamination is concentrated around transportation infrastructure most heavily used in the 1950s through the 70s; and 2) Areas in the city have highly localized elevated values from stationary dispersion of lead from deteriorating lead paint and historical industrial lead use within the urban centre of Atlanta.

The sample locations were randomly generated within ArcGIS, then collected at least 1m from any transportation infrastructure and at least 10m from any permanent structure when feasible. Each sample was collected with a plastic trowel to a depth of 10cm and stored in a plastic bag at Georgia State University. Before being analyzed for lead concentration samples were dried for 12hrs at 180° C then sieved to isolate the grains smaller than 250 μm.

Each sample was scanned a minimum of 4 times and a 95% confidence interval was calculated using a spreadsheet template provided by the Region IV office of the EPA. Sample scans with an RSD of 35% or greater were scanned up to 10 times, or until the RSD fell below the 35%. Samples which were either heavily contaminated or contained trace concentrations expressed the most significant variation in XRF results. This is due to the high variability in soil type and land use within a specialized range of urban environments. Lead concentrations measured ranged from below detection limit to > 12,000 ppm within the city.