title: On-road ammonia emissions characterized by mobile, open-path measurements.
abstract: Ammonia (NH3) is a key precursor species to atmospheric fine particulate matter with strong implications for regional air quality and global climate change. NH3 from vehicles accounts for a significant fraction of total emissions of NH3 in urban areas. A mobile platform is developed to measure NH3, CO, and CO2 from the top of a passenger car. The mobile platform conducted 87 h of on-road measurements, covering 4500 km in New Jersey and California. The average on-road emission factor (EF) in CA is 0.49 ± 0.06 g NH3 per kg fuel and agrees with previous studies in CA (0.3-0.8 g/kg). The mean on-road NH3:CO emission ratio is 0.029 ± 0.005, and there is no systematic difference between NJ and CA. On-road NH3 EFs increase with road gradient by an enhancement of 53 mg/kg fuel per percentage of gradient. On-road NH3 EFs show higher values in both stop-and-go driving conditions and freeway speeds with a minimum near 70 km/h. Consistent with prior studies, the on-road emission ratios suggest a highly skewed distribution of NH3 emitters. Comparisons with existing NJ and CA on-road emission inventories indicate that there may be an underestimation of on-road NH3 emissions in both NJ and CA. We demonstrate that mobile, open-path measurements provide a unique tool to help quantitatively understand the on-road NH3 emissions in urban and suburban settings.
authors: Department of Civil and Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors: Kang
authors: K
authors: Sun
authors: Lei
authors: L
authors: Tao
authors: David J
authors: DJ
authors: Miller
authors: M Amir
authors: MA
authors: Khan
authors: Mark A
authors: MA
authors: Zondlo
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000641:Ammonia / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis; D002248:Carbon Monoxide / Q000032:analysis; D015141:Los Angeles; D009515:New Jersey; D013997:Time Factors; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D002245:Carbon Dioxide; D000641:Ammonia; D002248:Carbon Monoxide