Science Inventory

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Recently, much attention has been directed at understanding the impact of mobile sources on near-road air quality, especially PM and its components, NOx and CO, but little information exists for mobile source air toxics (MSATs). MSATs of interest to this project are 1,3-butadiene, benzene, acrolein, acetaldehyde and formaldehyde. Concentrations of mobile source related air pollutants are known to decrease with distance from roadway. A meta-analysis of 33 traffic related studies round the spatial extent of impact for mobile sources on PM mass, ultra fine particle counts, black carbon (BC) and NOz varied depending on pollutant. A study performed in Raleigh, NC showed that short term changes in traffic and meteorology does impact near-road air pollutant concentrations. Results from two studies focusing on air toxics found concentrations returned to upwind levels after ~200 - 250 m from the roadway. These results, however, were based on time-integrated data of air toxics collected on a daily or multi-day basis. Over these time periods, significant changes can occur in meteorology (wind direction, mixing height, atmospheric stability, etc.) and traffic conditions. The National Near-Road Mobile Source Air Toxics Study is designed to evaluate both short-term and long-term effects by collecting high-time resolution data on concentrations of MSATs and other mobile source-related air pollutants, meteorology and traffic conditions. Data collected over a one-year period will also allow for an analysis of seasonal differences.

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AWMA conference paper

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