Emission factor of ammonia (NH ₃ ) from on-road vehicles in China: tunnel tests in urban Guangzhou

Abstract

Ammonia (NH 3 ) is the primary alkaline gas in the atmosphere that contributes to formation of secondary particles. Emission of NH 3 from vehicles, particularly gasoline powered light duty vehicles equipped with three-way catalysts, is regarded as an important source apart from emissions from animal wastes and soils, yet measured emission factors for motor vehicles are still not available in China, where traffic-related emission has become an increasingly important source of air pollutants in urban areas. Here we present our tunnel tests for NH 3 from motor vehicles under 'real world conditions' in an urban roadway tunnel in Guangzhou, a central city in the Pearl River Delta (PRD) region in south China. By attributing all NH 3 emissions in the tunnel to light-duty gasoline vehicles, we obtained a fuel-based emission rate of 2.92 ± 0.18 g L −1 and a mileage-based emission factor of 229.5 ± 14.1 mg km −1 . These emission factors were much higher than those measured in the United States while measured NO x emission factors (7.17 ± 0.60 g L −1 or 0.56 ± 0.05 g km −1 ) were contrastingly near or lower than those previously estimated by MOBILE/PART5 or COPERT IV models. Based on the NH 3 emission factors from this study, on-road vehicles accounted for 8.1% of NH 3 emissions in the PRD region in 2006 instead of 2.5% as estimated in a previous study using emission factors taken from the Emission Inventory Improvement Program (EIIP) in the United States.

On-road vehicle emissions of glyoxal and methylglyoxal from tunnel tests in urban Guangzhou, China

“…The tunnel is 1238.5 m in length with a 721 m flat underwater section. A schematic diagram of the tunnel is given by Liu et al (2014) and Zhang et al (2015). The tunnel's ventilation system was not operated during our study, and therefore in the tunnel bore selected for our test the air flow resulted entirely from the southbound vehicle traffic.…”

Air quality improvement in a megacity: implications from 2015 Beijing Parade Blue pollution control actions

“…These results, along with the fact that urban Beijing has a higher relative on-road vehicle density and almost no agricultural activity, suggest that NH 3 emission and transport from local traffic were the main contributors to high urban NH 3 concentrations. Based on a mileage-based NH 3 emission factors of 28 ± 5 (assumed as the lower limit; Chang et al, 2016) and 230 ± 14.1 mg km −1 (assumed as the upper limit; Liu et al, 2014) for light-duty gasoline vehicles, a population of 5.61 million vehicles (average mileage 21 849 km vehicle −1 yr −1 ) in Beijing would produce approximately 3.4-28 kt NH 3 in 2015, which likely declined by up to 4.7-38 t NH 3 day −1 during the Parade Blue period given that the traffic load decreased by half with the implementation of the odd-and-even car ban policy. For accurately determining NH 3 emissions, however, further study of NH 3 emission factors for vehicles and other sources is warranted.…”

Role of ammonia in forming secondary aerosols from gasoline vehicle exhaust

“…Recent tunnel studies indicated that emissions from light-duty gasoline vehicles (LDGVs) are also an important source of NH 3 [21][22][23][24][25]. Nordin et al [26] found that SOA formed from the exhaust of idling gasoline vehicles could be 1-2 orders of magnitude higher than POA.…”