Laser Technology Helps Measure Pollution from NYC Buses

Atmospheric scientists used laser technology while riding in traffic behind New York City transit buses to find out exactly how much and what type of pollution different types of buses emit in their exhausts, and the results were surprising. The findings may help other cities determine what kinds of buses to purchase for their transit systems.

The study found that conventional diesel buses are comparatively fuel efficient, but produce nitrogen oxide pollutants that can contribute to photochemical smog as well as large amounts of fine soot and sulfate particles, which are suspected to contribute to heart disease and lung cancer.

Photochemical smog develops when primary pollutants (nitrogen oxides and volatile organic compounds created from fossil fuel combustion) interact with sunlight and produce a mixture of hundreds of different and hazardous chemicals known as secondary pollutants.

Types of buses the researcher's tested included diesel buses with pollution controls called soot particle oxidation traps and without controls, new compressed natural gas fueled buses; and hybrid diesel/electric buses. Buses were tested while on their regular routes. They then determined that each type of bus poses different pollution problems.

Scott Herndon and Charles Kolb, of Aerodyne Research used a mobile step van laboratory with fast response laser sensors that provided emission results every second. The laser sensors generated a low-power light beam that measured pollutant levels in samples of the target vehicle's exhaust plumes drawn into the van as the buses went along their normal routes.

For the complete article on the NYC bus pollution, go to: http://www.gsfc.nasa.gov/topstory/2002/1206laser.html