Underestimated Ammonia Emissions from Road Vehicles.

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Transportation Emissions

Background:

• Accurate estimation of ammonia (NH3) emissions is crucial for air quality management.
• National inventories often rely on generalized emission factors, potentially leading to inaccuracies.
• Vehicle emissions are a significant contributor to atmospheric pollutants.

Purpose of the Study:

• To estimate total UK ammonia (NH3) emissions from passenger cars using novel methods.
• To compare bottom-up and top-down emission estimation approaches.
• To assess the accuracy of the UK National Atmospheric Emissions Inventory for NH3.

Main Methods:

• Utilized comprehensive remote sensing measurements from over 230,000 passenger cars.
• Employed both top-down and bottom-up emission estimation methodologies.
• Integrated 1 Hz real driving data with detailed remote sensing emission data.

Main Results:

• Bottom-up estimates indicated total annual UK NH3 emissions from gasoline cars at 7.8 ± 0.3 kt.
• The UK national inventory reported significantly lower emissions of 3.0 ± 1.7 kt.
• Both methods confirmed NH3 emissions are underestimated by a factor of approximately 2.6.

Conclusions:

• Gasoline passenger car NH3 emissions are substantially underestimated in the UK National Atmospheric Emissions Inventory.
• Urban NH3 emissions from passenger cars are particularly underreported, by a factor of 17.
• This study highlights the need for improved methodologies in national emission inventories.