Filterable PM2.5, Metallic Elements, and Organic Carbon Emissions from the Exhausts of Diesel Vehicles

Abstract

ABSTRACT Urban air pollution in the form of fine particulate matter (PM2.5) constitutes substantial health risks to human via inhalation. To determine the inhalation risks of PM2.5 containing metallic elements, we characterized and quantified PM2.5 emissions from the exhaust of 15 diesel vehicles having accrued mileages ranging from 28,306 to 883,374 km (average of 525,854 km). These vehicles originated from several manufacturers and covered model years from 1988 to 2005. The concentrations of metallic elements (Fe, Zn, Mg, K, Ca, Al, and Cr) were studied with the help of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results demonstrate that the metallic element composition in exhaust PM2.5 was in descending order as follows: Ca, Zn, Al, K, Fe, and Cr. The exhaust components containing PM2.5 and other chemical compositions were obtained based on carbonaceous materials (total carbon -TC, organic carbon - OC and elemental carbon - EC). Our results demonstrate that elemental carbon (EC) and organic carbon (OC) were the key concentrations of carbonaceous components: EC accounted for 2051 µg m-3 of PM2.5, while the OC fraction accounted for 1410 μg m-3, and TC accounted for 3461 µg m-3, respectively. The results have revealed Ca had the highest EFs among all the investigated atmospheric metallic elements, which ranged between 45.3 and 259 μg/L-fuel (with an average of 132 μg/L-fuel). Zn and Cr had the lowest EFs, accounting for a mean average of 13.1 μg/L-fuel and 1.91 μg/L-fuel, respectively. The concentrations and EFs of metallic elements in PM2.5 exhaust also were studied in relationship to atmospheric PM2.5 composition. These results will help further an understanding of how PM2.5 emissions from diesel vehicles contribute to metallic element concentrations in the natural environment and their potential negative effects.