Urban Air Hazard: Traffic Is Major Cause of Particulate Emissions


Traffic is a major cause of particulate pollution in the urban environment. While this may not be news to those living next to the highway, the exact cause of the pollution and possible solutions is something that we should sit up and notice. Fine particulates in the air are known to result in the premature death of over 300,000 people in the EU annually. Indeed, it is the increase in mortality that has led to firmer regulations of emissions in the U.S. and Europe. A recent report from The FINE Particles - Technology, Environment and Health – National Technology Programme in Finland reviews the latest research and technology used in monitoring traffic and the potential to create cleaner combustion engines. The report (PDF) addresses the details of how these small particles are created, and examines the technologies in development that might help us reduce this increasing hazard.The stated goal of the report is to examine how this pollution is generated, figure out how to monitor ‘real time’ emissions and identify business opportunities for creating a cleaner combustion engine. The 36 page report is well written with great graphics. If you have the time I recommend giving it a try. If you don’t have the time here is a quick synopsis.

• The report looked at both research oriented projects as well as technology oriented projects.

• Traffic emissions result from either the combustion process or from tyre (tire) contact with the road. Tire contact creates ‘road dust’ which is what makes up most of the monitored and controlled PM10 emissions. Fine particles are harder to monitor, and it is from the combustion engine that we get most of these fine particles.

• Vehicle emissions from the diesel combustion engine create two kinds of fine particles, soot particles and nucleation particles. Soot, as you may know is basically just amorphous carbon compounds, like what you might find inside your chimney. Nucleation particles are liquid like particles that can be composed of some very small center particle along with sulfuric acid and other hydrocarbons along for the ride. It is the elusive nucleation particles that dominate at the roadside and appear to be most closely related to increased traffic. The nucleation particles can have solid core materials that may have a significant influence on health.

• These nucleation particles are what needs to be studied in more detail- however because they can and do form outside of the actual combustion process a wide range of things can change their behavior. The air temperature, the humidity, or other particulate matter can all create different environments for nucleation particles. This report describes a paper where they used a ‘real time’ chase car to pick up emission on the road instead of in the lab. The report clarifies that for future emissions standard for fine particles to be set correctly we will need to employ new collection methods-including emissions monitoring chase cars.

• The report noted that as we move into new fuel mixtures such as bio-fuel we will need to adjust our monitoring, engine design, and emissions standards to match. They also point out that factors such as injection timing, combustion chamber shape, swirl motion, and controllable valve timing may be ways of cutting particulate emissions. And point to research showing that lowering aromatic content in diesel fuel reduced potentially hazardous emissions.

• The report describes a few filter technologies, but nothing there seems more promising then using particle oxidation catalytic converters (POC). In general they feel there is a need for further development of filters to achieve future emissions regulations.

• They stress that how and what emissions we monitor will play a big role in creating future combustion engine technology. Their analysis points out that not only should we be looking at solid particles, but we should also be looking at nucleation particles as indicators of urban air quality- something we are currently not taking into account.

• Lastly, the report calls for more work to be done on biofuels such as ethanol and biodiesel to investigate how they perform in terms of particulate emissions and the characteristics of the particles they release, both sooty and nucleation type fine particles.

The findings of this report point out where we need to invest our research energy, as well as direct our policy for emissions standards. It also motivates me to find an apartment a little bit further away from the freeway. ::Reducing Particulate Emissions in Traffic and Transport (PDF)

Related Content on Treehugger.com