Graduate student Changhyoun Park's research, flux measurements of volatile organic compounds (VOCs) in an urban area, analyzed a long-term data set of local Houston air quality. His efforts earned him a first-place prize for his division in the recent Student Research Week 2010 at Texas A&M.

Park (right), a doctoral student graduating in May, presented his research findings on man-made and tree-canopy related isoprene emission measurements taken from a tall tower near downtown Houston. His measurements show that cars may be a much larger source of this naturally occurring chemical than previously thought.

"I measured the eddy flux of so called volatile organic compounds, or VOCs, by installing monitoring equipment on the 60 m communications tower of Houston's taxicab company," Park said. Eddy-flux measurements record the surface-atmosphere exchange of gases, in this particular case that of VOCs. This kind of measurement is commonly used at rural or forest sites, but Park and his advisor Dr. Gunnar Schade are among the first researchers to use it in an urban environment. As a primary goal of his research, Park set out to evaluate the correctness of emissions inventories by comparing his data to established EPA emission inventory numbers.

"Houston has long been recognized as having one of the highest levels of pollutant emissions in the United States, in part due to its petrochemical industries," Park explained. EPA guidelines predict that even with corrective measures, Houston, the nation's fourth largest city, will continue to violate the new ozone air quality standard until 2020. "We wanted to know how close the EPA's emission inventory model is to real-world emissions, because the model data enter into predictions of past, present and future air quality."

Park found that the EPA model underestimated the amount of certain pollutants emitted into the atmosphere by as much as three to five times, albeit with significant uncertainties. As these pollutants cause ground-level ozone pollution, Park, says, related to respiratory problems, they degrade the overall quality of life in the city.