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Effects of Aftermarket Control Technologies on Gas and Particle Phase Oxidative Potential from Diesel Engine Emissions
Pavlovic, J., A. Holder, AND T. Yelverton. Effects of Aftermarket Control Technologies on Gas and Particle Phase Oxidative Potential from Diesel Engine Emissions. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 49:10544-10552, (2015).
Epidemiological studies have shown associations between ambient PM and increases in human morbidity and mortality due to lung cancer, cardiopulmonary diseases, and asthma (Dockery et al., 1993). Emerging hypothesis is that PM-induced toxicity is driven by the presence of reactive oxygen species (ROS) within affected cells in the respiratory system. ROS have been shown to be detrimental in living cells by causing oxidative stress that is made apparent by various inflammatory effects, such as asthma, chronic bronchitis, ischemic heart disease and stroke, among others (Griendling and FitzGerald, 2003; Vallyathan et al., 1998; Poli and Parola, 1997). The findings from the present study provide a better understanding of potential health effects (oxidative stress) of particle and gas emissions from stationary diesel gensets with and without modern after treatment control devices. This study showed that the engine size/output, as well as the engine load and type of control device affect the GROS and PMROS concentrations and PMOP.
Particulate matter (PM) originating from diesel combustion is a public health concern due to its association with adverse effects on respiratory and cardiovascular diseases and lung cancer. This study investigated emissions from three stationary diesel engines (gensets) with varying power output (230 kW, 400 kW, and 600 kW) at 50% and 90% load to determine concentrations of gaseous (GROS) and PM reactive oxygen species (PMROS). In addition, the influence of three modern emission control technologies on ROS emissions was evaluated: active and passive diesel particulate filters (A-DPF and P-DPF) and a diesel oxidation catalyst (DOC). PMROS made up 30-50% of the total ROS measured without aftermarket controls. All applied controls removed PMROS by more than 75% on average. However, the oxidative potential of PM downstream of these devices was not diminished at the same rate and particles surviving the A-PDF had an even higher oxidative potential on a per PM mass basis compared to the particles emitted by uncontrolled gensets. Further, the GROS as compared to PMROS emissions were not reduced with the same efficiency (<36%). GROS concentrations were highest with the DOC in use, indicating continued formation of GROS with this control. Correlation analyses showed that PMROS and to a lesser extent GROS have a good correlation with semi-volatile organic carbon (OC1) sub-fraction. In addition, results suggest that chemical composition, rather than PM size, is responsible for differences in the PM oxidative potential.