treasure valley road dust study: final report - ResearchGate

?? To assess the impact of wintertime application of traction control materials, street
sweeping, and the occurrence of certain meteorological events on road dust emissions.
?? To collect and chemically analyze road dust samples for use in Chemical Mass Balance
(CMB) receptor modeling.
1.3 Technical Approach
The objectives of this study were accomplished through a combination of field data
collection, laboratory analysis, data processing, and modeling.
1.3.1 Field Data Collection
The Treasure Valley Road Dust Study used primarily locally-collected data to estimate
road dust emissions. All the fieldwork for this project occurred in 2001 and was divided into a
winter (2/26/01–3/17/01) and a summer (7/11/01–7/26/01) portion. The field study consisted of
multiple components including procurement of road dirt samples for silt and source profi le
analyses of road dust, surveys of streets in the Treasure Valley with the TRAKER vehicle (see
below) to assess spatial distributions of road dust emissions factors, repeated TRAKER
measurements of road dust emissions factors over the same set of streets on 12 different
occasions to assess temporal variability, and two intensive experiments to test the effects of
wintertime road sanding and street sweeping on road dust emissions factors.
1.3.1.1 Silt Sampling
The AP-42 (USEPA, 1999) prescribes the use of silt measurements for estimation of
emissions factors from both paved and unpaved roads. Silt is defined operationally as the
material that can pass through a 200 mesh sieve (nominally corresponding to particles with
diameters of 75 ?m or less). Silt content is used to estimate emissions from unpaved roads and is
defined as the ratio of silt mass in the sample to the total mass in the sample. In contrast, the silt
loading which is used to calculate emissions from paved roads is defined as the mass of silt per
unit area of road. Sample collection involves securing the test area from passing vehicles and
carefully sweeping and vacuuming three measured strips of roadway that run perpendicular to
the direction of traffic. Road soil samples were collected for silt analysis during the wintertime
and summertime from a variety of road classes throughout the Treasure Valley.
1.3.1.2 TRAKER
TRAKER (Testing Re-entrained Aerosol Kinetic Emissions from Roads), developed at
the Desert Research Institute (DRI), is a new method for measuring the emissions potential from
roads (Kuhns et al., 2001). TRAKER consists of a vehicle fitted with particle measuring
instruments that draw air from behind the front tires. The on-board instruments log the particle
concentration behind the tire and the GPS coordinates of the measurement every 1 second of
operation. The advantage of the TRAKER over traditional silt loading methods is that hundreds
of thousands of measurements of suspendable PM 10 can be obtained in a relatively short period
of time over a large spatial domain. This allows for a more representative sampling of road dust
emissions than can be practically obtained with traditional silt measurements.
In this study, the TRAKER was used in three ways. First, the TRAKER was used to
survey over 400 km of roads during each of the two sampling seasons in Ada and Canyon
Counties. Second, the TRAKER was used to assess seasonal trends in the dust emitting potential
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