Urban Geochemistry In A Pb-Contaminated Environment: Analysis Of Roadside Hazards In Philadelphia, Pa
Environmental media, such as road dust and soils, can be used to study contaminants in the urban environment. In particular, lead (Pb), is a neurotoxic pollutant that has had substantial impact on urban communities. While Pb pollution is a pressing issue, few studies have addressed it in Philadelphia with environmental media assessments. In this dissertation, I performed novel multi-analytical mineralogical and chemical characterizations of road dusts and soils. Additionally, I created innovative dissolution experiments to explore potential risks from yellow traffic paint containing crocoite (PbCrO4) to human health and to the environment. In Chapter 2, I describe a framework where I sampled and characterized road dust collected throughout Philadelphia. In this published work, I found that there were some differences in chemical concentrations for many elements by both traffic and land use, with industrial areas being most polluted. I also observed high Pb content in road dust, compared internationally, and noted areas of high risk. I report a published investigation of a source of this Pb, yellow traffic paint containing crocoite, in Chapter 3. As limited experiments have been performed on this subject, I created an approach to simulate environmental (rainwater) and human (inhalation and ingestion) interactions. I found that the silica coating surrounding the crocoite particles persisted in all interactions and limited the release of Pb and Cr into solution, thus reducing the potential danger of the particles. Finally, in Chapter 4 (submitted work), I present an investigation of collocated road dust and soil samples at two size fractions in Fishtown, one of the most Pb-contaminated areas of Philadelphia. Electron microscopy results revealed an abundance of small Pb particles in all sample types; I also found that finer soils were more enriched in Pb than bulk samples. Furthermore, I noted that elemental concentrations were statistically significantly different by both size and media for most elements. However, the mineral phases identified were similar for all sizes and media. This dissertation outlines the efficacy of our multi-analytical approach and demonstrates the form, location, and potential risk of contaminants such as Pb in Philadelphia.