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DEVELOPMENT OF A MODEL FOR REAL TIME CO CONCENTRATIONS NEAR ROADWAYS

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Citation:

Singh, R. B. AND A H. Huber. DEVELOPMENT OF A MODEL FOR REAL TIME CO CONCENTRATIONS NEAR ROADWAYS. Presented at AWMA 93rd Annual Meeting and Exhibition, Salt Lake City, UT, June 18-22, 2000.

Impact/Purpose:

The research is planned to meet the following objectives:

Support is provided to HEASD Tasks by Alan Huber. (60% 9524 New Air Toxics Modeling, ; 10% 5732 PM Population Exposure Modeling; 10% 3948 Next Generation MMMP Exposure Modeling; 10% N533 PM Toxic agent exposure modeling, and 10% 3957 Integrated Human Exposure Source-to-Dose Modeling)

  • Development of data and algorithms for exposure modeling in urban areas, to be used in refined probabilistic exposure models being developed elsewhere, to allow prediction of human exposures for an urban population.

  • Characterize exposures and variability of concentrations in critical microenvironments in urban areas using targeted measurement studies and refined air quality models.

  • Identify critical human activities influencing exposures, especially identifying microenvironments that are key to exposures to urban air toxics.

  • Develop methods (measurements, dispersion modeling, receptor modeling) to distinguish exposures to "near field" sources - like indoor sources, human activities or hobbies, or nearby point or area sources - from "background" concentrations or from distant sources that can be modeled well by compartmental or air quality models.

  • Provide data and algorithms based on a scientific understanding of exposure dynamics for inclusion in NERL human exposure models and other models like OAR's TRIM..

    • Description:

    Although emission standards for mobile sources continue to be tightened, tailpipe emissions in urban areas continue to be a major source of human exposure to air toxics. Current human exposure models using simplified assumptions based on fixed air monitoring stations and regional scale emission models do not represent the actual human exposures and should be improved. The MOBILE (used in USA except California) and EMFAC( used in California only) mobile source emission models are suitable for supporting regional scale modeling and emission inventory. These emission models have not be designed to estimated real-time emissions needed to support human exposure studies near roadways. A number of independent studies have found that these emission factor models are not reliable for estimating microscale emissions and therefore inappropriate to be used with roadway dispersion models and microenvironmental modeling necessary to estimate human exposures near roadways. Therefore, it has become necessary to design a real-time emission factor model capable of estimating emission factors at microscale level helpful in establishing complex source-to dose relationships.

    In view of the above, a real time microscale automobile emission factor model for CO (MicroFacCo), virtually capturing all the information in the real world, has been developed for United States vehicles. The algorithm used to calculate emission factors is disaggregated based on the on-road vehicle fleet. The emission factors are calculated from a real-time fleet, not for a fleet-wide average estimated by vehicle miles traveled (VMT) weighting of the emission factors for different vehicle classes (methodology used to develop MOBILE and EMFAC). MicroFacCo calculates the emission factors from a road on a lane-by-lane basis and for available vehicle fleet structure data based on direct observations, video records, available tunnel studies vehicle fleet or average values of the country or region. Apart from calculating composite emission factors, the model also gives the contribution of CO from different sources, both depending on vehicle class wise and year wise.

    The model is being used to conjunction with roadway dispersion models (i.e.CALINE4), and being evaluated in the roadways around research triangle park, north carolina in a range of traffic fleet and meteorological conditions. Modeled concentrations are bing compared with measured concentrations inside a vehicle and along the roadside of I-40 and highway 70.

    Record Details:

    Record Type:DOCUMENT( PRESENTATION/ ABSTRACT)
    Product Published Date:06/18/2000
    Record Last Revised:06/21/2006
    Record ID: 62610