2001, Volume 35, 3735-3741 Marc M. Baum,* Eileen S. Kiyomiya, Sasi Kumar, Anastasios M. Lappas, Vadym A. Kapinus, and Harry C. Lord III: Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-Road Ammonia Measurements. A term converting molar concentration ratios to mass-based emission rates was inadvertently omitted from eq 1. The revised eq 1 with the term included is
Er ) {[NH3]/[CO2]}{Em(CO2) × 17.0/44.0}/7.1
(1)
The above omission led to an overestimation of ammonia (NH3) mass emission rates (Em) and emission rates (Er) by a factor of 2.6. A revised Table 2 with the corrected values is given here.
TABLE 1. Gas-Phase Emissions Data on Criteria Pollutants Measured between April 25 and 30, 1999 mean (% V) s.d. (% V) max (% V) Em (g L-l) Er (g km-l)a a
CO2
CO
THC (as C3H8)
NO
14.48 1.18 15.05 2100 296
0.79 1.65 11.50 69 9.7
0.0145 0.0455 1.37 1.9 0.27
0.0665 0.0813 0.623 6.8 0.95
Based on a mean fleet fuel efficiency of 7.1 km L-1.
TABLE 2. Gas-Phase Fleet NH3 Emissions Data Measured between April 25 and 30, 1999 mean concentration (ppm V) standard deviation (ppm V) maximum concentration (ppm V) mean NH3/CO2 ratio (ppm V/ppm V) Em (mg L-1) Er (g km-I)a a
44.7 83 2024 31.9 × 10-5 257 36
Based on a mean fleet fuel efficiency of 7.1 km L-l.
In addition, estimated vehicular, gas-phase NH3 emissions in the South Coast Air Basin of California based on our corrected data should be 17 t day-1, accounting for between 8 and 10% of total emissions in the region. An analogous expression to eq 1 was used to calculate nitric oxide (NO) emission rates (Em and Er), which consequently were overestimated by a factor of 1.5. A revised Table 1 is also included above containing corrected NO emission rates. The authors thank Andrew J. Kean and Robert A. Harley of the University of California at Berkeley for bringing the error in eq 1 to our attention. ES020890D 10.1021/es020890d
10.1021/es020890d CCC: $22.00 Published on Web 09/17/2002
2002 American Chemical Society
VOL. 36, NO. 21, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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