Chemical Characterization and Source Apportionment of PM2.5 in a Nonattainment Rocky Mountain Valley

Severe air pollution has significant adverse health effects and poses a threat to public health in many communities, including nonattainment areas in the Unites States. To develop effective control strategies to reduce air pollution with minimum economic cost, one of the biggest challenges is to quantify the contributions from different sources. By combining chemical analyses, Positive Matrix Factorization modeling, and emission inventory development, this study identified primary and secondary sources of particulate matter with a diameter of <2.5 μm (PM) in a nonattainment Rocky Mountain valley (i.e., West Silver Valley [WSV]) in Idaho. The results show that biomass burning is the dominant source and contributes ∼84% of the PM concentration in the valley. The study also identified influences on the WSV PM concentrations from traffic (7.4%), soil dust (3.4%), and secondary aerosols (4.8%). The results of this paper represent the first report on the chemical composition and source apportionment of PM in mountain valleys of northern Idaho and have been used to develop effective strategies to reduce the PM concentrations in the WSV. Moreover, this study provides detailed equations and methods in PM speciation, accounting for artifacts of the chemical analysis, Positive Matrix Factorization modeling, and emission inventory development, which can be used for source apportionment of severe air pollution in other regions.