Examining source apportionment models for fine particulate matter in the midwestern United States

In 1997, the United States Environmental Protection Agency promulgated the National Ambient Air Quality Standards for fine particulate matter. The Speciation Trends Network was established in 2001 to better characterize the composition of fine particulate matter. Through better characterization, it is possible to determine fine particulate matter source contributions to control the pollutant and reduce ambient concentrations thus allowing bringing areas across the United States into compliance with the standard.; This work examined the results of the Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) source apportionment models for three urban sites and one rural location in the Midwestern United States. A comparison of the results from the two models showed that they correlated rather well with one another for all of the sites examined. This agreement especially applied to area wide sources as opposed localized sources of fine particulate matter.; An examination of the rotational ambiguity of the PMF model using edges demonstrated an improved relationship between CMB and PMF motor vehicle source contributions. The use of target shapes to rotate the PMF solution showed that it is possible to use the CMB and PMF models to cross validate one another as well as determine which species may or may not have a significant role in determining a particular source's fine particulate matter contribution.; Comparing the source contributions by site showed that it may be possible to identify a "qualified diesel" source signature by using iron and manganese as the tracer elements. This source was present at all four locations with greater contributions occurring at the rural site as opposed to the urban locations. This may be due to better atmospheric mixing of the diesel emissions with gasoline vehicles in the urban areas.