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The measurement of SO2 levels in vehicle exhaust can provide important information in understanding the relative contribution of sulfur and sulfate from fuel vs. oil source to PM. For this study, a differential optical absorption spectrometer (DOAS) that can measure SO2 down to 20 ppbV in real-time was built and evaluated. The DOAS consisted of an extractive sampling train, a cylindrical sampling cell with a single-path design to minimize cell volume, a spectrometer, and a deuterium lamp light source with a UVC range of ∼200-230 nanometer (nm). Laboratory tests showed detection limits were approximately in the range of 12 to 15 ppbV and showed good linearity over SO2 concentration ranges of 20 to 953 ppbV. Interference tests showed some interference by NO and by NH3, at levels of 300 ppmV and 16.6 ppmV, respectively.

The impact of biodiesel and new generation biofuels on emissions from heavy-duty diesel engines was investigated using a California Air Resources Board (CARB) certified diesel fuel as a base fuel. This study was performed on two heavy-duty diesel engines, a 2006 engine and a diesel particle filter (DPF) equipped 2007 engine, on an engine dynamometer over four different test cycles. Emissions from soy-based and animal-based biodiesel, renewable diesel fuel, and gas-to-liquid (GTL) diesel fuel were evaluated at blend levels ranging from 5 to 100%. Consistent with previous studies, particulate matter (PM), hydrocarbons (HC), and carbon monoxide (CO) emissions generally showed increasing reductions with increasing biodiesel and renewable/GTL diesel fuel blend levels for the non-DPF equipped engine. The levels of these reductions were generally comparable to those found in previous studies performed using more typical Federal diesel fuels.

Light duty gasoline vehicles (LDGV) are estimated to contribute 40% of the total on-road mobile source tailpipe emissions of particulate matter (PM) in California. While considerable efforts have been made to reduce toxic diesel PM emissions going into the future, less emphasis has been placed on PM from LDGVs. The goals of this work were to characterize a small fleet of visibly smoking and high PM emitting LDGVs, to explore the potential PM-reduction benefits of Smog Check and of repairs, and to examine remote sensing devices (RSD) as a potential method for identifying high PM emitters in the in-use fleet. For this study, we recruited a fleet of eight vehicles covering a spectrum of PM emission levels. PM and criteria pollutant emissions were quantified on a dynamometer and CVS dilution tunnel system over the Unified Cycle using standard methods and real time PM instruments.