Ja. Gillies et al., On-road particulate matter (PM2.5 and PM10) emissions in the Sepulveda Tunnel, Los Angeles, California, ENV SCI TEC, 35(6), 2001, pp. 1054-1063
Citations number
41
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
Total and speciated particulate matter (PM2.5 and PM10) emission factors fr
om in-use vehicles were measured for a mixed light- (97.4% LD) and heavy-du
ty fleet (2.6% HD) in the Sepulveda Tunnel, Los Angeles, CA. Seventeen l-h
test runs were performed between July 23, 1996, and July 27, 1996. Emission
factors were calculated from mass concentration measurements taken at the
tunnel entrance and exit, the Volume of airflow through the tunnel, and the
number of vehicles passing through the 582 m long tunnel. For the mixed LD
and HD fleet, PM2.5 emission factors in the Sepulveda Tunnel ranged from 0
.016 (+/-0.007) to 0.115 (+/-0.019) g/vehicle.km traveled with an average o
f 0.052 (+/-0.027) g/vehicle.km. PM10 emission factors ranged from 0.030 (/-0.009) to 0.131 (+/-0.024) g/vehicle.km with an average of 0.069 (+/-0.03
0) g/vehicle.km. The PM2.5 emission factor was similar to 74% of the PM10 f
actor. Speciated emission rates and chemical profiles for use in receptor m
odeling were also developed. PM2.5 was dominated by organic carbon (OC) (31
.0 +/- 19.5%) and elemental carbon (EC) (48.5 +/- 20.5%) that together acco
unt for 79% (+/-24%) of the total emissions. Crustal elements (Fe, Mg, Al,
Si, Ca, and Mn) contribute similar to7.8%, and the ions Cl-, NO3-, NH3+, SO
42-, and K+ together constitute another 9.8%. In the PM10 size fraction the
particulate emissions were also dominated by OC (31 +/- 12%) and EC (35 +/
- 13%). The third most prominent species was Fe (18.5 +/- 9.0%), which is g
reater than would be expected from purely geological sources. Other geologi
cal components (Mg, All Si, K, Ca, and Mn) accounted for an additional 12.6
%. PM10 emission factors showed some dependence on vehicle speed, whereas P
M2.5 did not. For test runs in which the average vehicle speed was 42.6 km/
h a 1.7 times increase in PM10 emission factor was observed compared to tho
se runs with an average vehicle speed of 72.6 km/h. Speciated emissions wer
e similar. However, there is significantly greater mass attributable to geo
logical material in the PM10, indicative of an increased contribution from
resuspended road dust. The PM2.5 shows relatively good correlation with NOx
emissions, which indicates that even at the low percent of HD vehicles, wh
ich emit significantly more NOx than ID vehicles, they may also have a-sign
ificant impact on the PM2.5 levels.