Finding dirty diesels

Diesel-fueled vehicles have gained notoriety for their oily carbon emissions. However, there’s wide variability in how much of this soot any car emits. A new Dutch study finds that just 5 percent of cars—mostly diesel-fueled vehicles—account for 43 percent of tailpipe-soot releases.

Andy Kurniawan and Andreas Schmidt-Ott of Delft University of Technology analyzed soot emissions from more than 1,250 cars by using a device set up on the shoulder of the road. As long as cars were spaced at least 8 seconds apart, the device could suck in and determine a single vehicle’s exhaust. In the March 15 Environmental Science & Technology, the researchers describe how the device works. By irradiating the carbon particles with ultraviolet light, the device imparts a positive electric charge to them. It then measures the charge to quantify the soot, Schmidt-Ott explains.

Policy makers looking to reduce pollution may get the biggest bang for the buck by focusing on cars badly in need of a tune-up, Schmidt-Ott maintains. The chemical engineer recommends that municipalities begin scouting for “superpolluters,” with devices such as the one that his group used.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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