Many REEL OSU students pursue group or individual research questions involving environmental chemistry as part of their introductory chemistry courses. In addition, students also contribute to an overarching investigation of the anthropogenic background concentration of analytes in the area.
Anthropogenic activities in urban areas have the potential to concentrate potentially toxic materials, like lead, in settings that are often frequented by a large number of people. Exposure to these toxins poses numerous health risks depending on the nature of the exposure. The goal of identifying areas with increased concentrations of harmful toxins should also be joined with efforts to establish baseline values for these same substances at sites with minimal anthropogenic contributions. To this end, REEL students in Chemistry 123 have analyzed surface soil samples collected from public parks throughout Greater Columbus, OH. Samples were then processed and analyzed by X-ray fluorescence spectroscopy to determine the concentration of various analytes (like lead). These results serve to establish the background concentration typically found in this area and act as a baseline for comparing other portions of this urban area that have different land uses.
Background Concentrations, Anthropogenic Contributions & Testing Sites
Natural background concentrations reflect levels of soil concentrations that naturally occur at sites that have not been disturbed or affected by human activities.
Background, or anthropogenic background concentrations result from human activities not associated with a specific contamination activity. The more human activity in an area, the greater the potential anthropogenic enhancement.
Point source releases of contaminants results in increased concentrations that are geographically restricted in scope and more intense in enhancement than is considered acceptable as anthropogenic background enhancement. In terms of testing sites, urban areas exhibit different zones of activity, including manufacturing centers, residential and retail area, parks and nature preserves, etc. Public parks in urban areas will have soil compositionally similar to the rest of the area, but will exhibit less human disturbance. Public parks were therefore chosen to represent the background concentration in this area.
Results and Discussion
An important analyte investigated here is lead, Pb. As determined by XRF for surface soil samples collected from urban parks (N=265) the refined background concentration distribution of Pb has a mean of 36 ppm and standard deviation of 11 ppm (skewness = 0.18, kurtosis = -0.7). Prior to removal of outliers the mean and standard deviation are 73 ppm and 115 ppm, respectively. The large standard for the entire data set (N=386) is attributed to prevalence of contaminated samples in this urban area.
The average concentration of Pb in urban soils is often much higher than values determined here, e.g. Rome, London, and Birmingham average 330, 300, and 570 ppm, respectively. Warsaw and Bangkok, however, have reported average values less than 75 ppm, and the background concentration reported agrees with worldwide estimates (D.S. Manta, et. al. The Science of the Total Environment. 2002, 300, 229-243). It is also evident that that parks in center of the urban area, being older, are more likely to exhibit elevated Pb concentration.
Primary Research Contributors: Jason Eng, Jason Stybel, Steven Kiracofe and Dr. Ted M. Clark. Several conference presentations have been based on this project.