PM Emissions Emanating from Limited-Access Highways

Abstract

Motor vehicle contributions to primary particulate matter (PM) emissions include exhaust, tire wear, brake and clutch wear, and resuspended road dust. Relatively few field studies have been conducted to quantify fleetaverage exhaust emissions for actual on-road conditions. Therefore, direct measurements of motor vehicle-related PM emissions are warranted. In this study, PM 10 and PM 2.5 mass concentrations were measured near two major highways in the St. Louis area over the period from FebruaryApril 1997. Samplers were deployed both upwind and downwind of the roadways to capture the transport and dispersion of PM with distance from the roadway. The observed microscale concentration fields were compared to estimates using the PART5 emission factor model together with the CALINE4 highway dispersion model. Traffic-induced PM mass concentrations observed downwind of the roadway were always less than PART5/CALINE4 predictions; average percent differences for observed traffic-induced mass concentrations compared to predicted values were -34% for PM 2.5 and -70% for PM 10 . In most cases, the observed PM concentration decay with increasing distance from the roadway was steeper than predicted by dispersion modeling. Motor vehicle-induced emission factors were reconstructed by fitting CALINE4 to the observed concentration data with the emission factor as the sole adjustable parameter. Reconstructed fleet-average motor vehicle emission factors for the urban interstate highway were 0.03-0.04 g/VMT for both PM 2.5 and PM 10 , IMPLICATIONSMotor vehicle emission factors can be combined with vehicle fleet activity data to predict traffic-induced emissions. This paper provides data for ambient particulate matter concentrations measured near limited-access roadways in St. Louis, and uses a highway dispersion model to reconstruct the fleet-average emission factors. Reconstructed emission factors were lower than predicted values. While such information can be used to test the validity of emission factor predictions, additional work is needed to compare different methods for reconstructing emission factors.while the fleet-average emission factors for the rural interstate highway were 0.2 and 0.3 g/VMT for PM 2.5 and PM 10 , respectively.

Tailpipe and Nontailpipe Emission Factors and Source Contributions of PM10 on Major Freeways in the Los Angeles Basin

“…Speciated Daily Tailpipe and Non-Tailpipe Emission Rates of LDVs and HDVs on the Entire Los Angeles Basin Freeways a −1 which is in agreement with the Lamoree and Turner (1999)85 estimation (20 mg km −1 veh −1 ). Furthermore, the PM 10 emission factors of tire and brake wear for LDVs (10.63 ± 3.46 mg km −1 veh −1 ) and HDVs (30.12 ± 3.46 mg km −1 veh −1 ) are generally consistent with the corresponding values inLuhana et al (2004) …”

“…The combined tire and brake wear emission factor for average vehicle fleet in this study was 16.00 ± 3.69 mg km –1 veh –1 which is in agreement with the Lamoree and Turner (1999) estimation (20 mg km –1 veh –1 ). Furthermore, the PM 10 emission factors of tire and brake wear for LDVs (10.63 ± 3.46 mg km –1 veh –1 ) and HDVs (30.12 ± 3.46 mg km –1 veh –1 ) are generally consistent with the corresponding values in Luhana et al (2004) study, estimating 6.9 mg km –1 veh –1 and 49.7 mg km –1 veh –1 for LDV and HDV fleet, respectively.…”

Transport of Atmospheric Fine Particulate Matter: Part 2—Findings from Recent Field Programs on the Intraurban Variability in Fine Particulate Matter

“…In the latter case, one conventional approach is to perform spatial gradient monitoring near the source, ideally with upwind measurements to distinguish the emission source contributions from background levels. 31 Another, indirect approach is to deconvolute high-time-resolution data into different frequency components with the high frequency contributions likely indicative of near-field emissions and the low frequency contributions likely due to emissions on larger spatial scales. 6 …”

The Unfavorable Influence of Transport on the Environment

“…However, the release of other pollutants, especially PM, is connected with other processes as well, such as the abrasion of various exposed components (brake and clutch lining) when copper (Cu), antimony (Sb), barium (Ba), iron (Fe), aluminium (Al), zinc (Zn), molybdenum (Mo), manganese (Mn), magnesium (Mg), cadmium (Cd), and others are released into the air (Lamoree, Turner, 1999). The abrasion of tyres containing various types of rubber is a source of zinc; other metals like calcium VOLUME 4 TRANSACTIONS ON TRANSPORT SCIENCES NUMBER 2 (Ca) and iron (Fe), and elementary carbon are released as well.…”