Morphological and Trace Element Analysis of Nano Spherical Soot from the Central Valley of California

Abstract

Cancer clusters in the Central Valley of California have been linked to metal exposure. One suspected pathway for metal exposure is through air particulates and soot makes up a large portion of air particulates in many samples (> 50% during winter samples). Soot is a byproduct of incomplete combustion of any carbonaceous material but primary sources include diesel engines, agriculture (including forest fires), burning of waste materials and transportation. Using the Transmission Electron Microscope (TEM) we are analyzing soot collected by the California Air Resources Board from three different environments; upwind, downwind and within the Central Valley. Upwind soot is fairly uniform in composition, with very low metal contents but soot from urban settings shows both structural and chemical variability and metal contents up to 4810 ppm of Pb, 250ppm of Se and 1450ppm of As. In this study, we examine soot from these different environments to evaluate both potential sources for soot and the possible health effects. In the future, we will be looking at changes in soot composition over time to determine if changing government regulations of fuel contents has resulted in changes in the level of harmful contaminants in soot.