New insights from comprehensive on-road measurements of NO\(_x\), NO\(_2\) and NH\(_3\) from vehicle emission remote sensing in London, UK

Abstract

In this paper we report the first direct measurements of nitrogen dioxide (NO\(_2\)) in the UK using a vehicle emission remote sensing technique. Measurements of NO, NO\(_2\) and ammonia (NH\(_3\)) from almost 70,000 vehicles were made spanning vehicle model years from 1985 to 2012. These measurements were carefully matched with detailed vehicle information data to understand the emission characteristics of a wide range of vehicles in a detailed way. Overall it is found that only petrol fuelled vehicles have shown an appreciable reduction in total NO\(_x\) emissions over the past 15-20 years. Emissions of NO\(_x\) from diesel vehicles, including those with after-treatment systems designed to reduce emissions of NO\(_x\), have not reduced over the same period of time. It is also evident that the vehicle manufacturer has a strong in- fluence on emissions of NO\(_2\) for Euro 4 and 5 diesel cars and urban buses. Smaller-engined Euro 4 and5 diesel cars are also shown to emit less NO\(_2\) than larger-engined vehicles. It is shown that NO\(_x\) emissions from u rban buses fitted with Selective Catalytic Reduction (SCR) are comparable to those using Exhaust Gas Recirculation for Euro V vehicles, while reductions in NO\(_x\) of about 30% are observed for Euro IV and EEV vehicles. However, the emissions of NO\(_2\) vary widely dependent on the bus technology used. Almost all the NO\(_x\) emission from Euro IV buses with SCR is in the form of NO, whereas EEV vehicles (Enhanced Environmentally friendly Vehicle) emit about 30% of the NO\(_x\) as NO\(_2\). We find similarly low amounts of NO\(_2\) from trucks (3.5-12t and >12t). Finally, we show that NH\(_3\) emissions are most important for older generation catalyst-equipped petrol vehicles and SCR-equipped buses. The NH\(_3\) emissions from petrol cars have decreased by over a factor of three from the vehicles manufactured in the late 1990s compared with those manufactured in 2012. Tables of emission factors are presented for NO\(_x\), NO\(_2\) and NH\(_3\) together with uncertainties to assist the development of new emission inventories.

New insights from comprehensive on-road measurements of NO\(_x\), NO\(_2\) and NH\(_3\) from vehicle emission remote sensing in London, UK

D.C. Carslaw, G. Rhys-Tyler

Atmospheric Environment, 2013

In this paper we report the first direct measurements of nitrogen dioxide (NO\(_2\)) in the UK using a vehicle emission remote sensing technique. Measurements of NO, NO\(_2\) and ammonia (NH\(_3\)) from almost 70,000 vehicles were made spanning vehicle model years from 1985 to 2012. These measurements were carefully matched with detailed vehicle information data to understand the emission characteristics of a wide range of vehicles in a detailed way. Overall it is found that only petrol fuelled vehicles have shown an appreciable reduction in total NO\(_x\) emissions over the past 15-20 years. Emissions of NO\(_x\) from diesel vehicles, including those with after-treatment systems designed to reduce emissions of NO\(_x\), have not reduced over the same period of time. It is also evident that the vehicle manufacturer has a strong in- fluence on emissions of NO\(_2\) for Euro 4 and 5 diesel cars and urban buses. Smaller-engined Euro 4 and5 diesel cars are also shown to emit less NO\(_2\) than larger-engined vehicles. It is shown that NO\(_x\) emissions from u rban buses fitted with Selective Catalytic Reduction (SCR) are comparable to those using Exhaust Gas Recirculation for Euro V vehicles, while reductions in NO\(_x\) of about 30% are observed for Euro IV and EEV vehicles. However, the emissions of NO\(_2\) vary widely dependent on the bus technology used. Almost all the NO\(_x\) emission from Euro IV buses with SCR is in the form of NO, whereas EEV vehicles (Enhanced Environmentally friendly Vehicle) emit about 30% of the NO\(_x\) as NO\(_2\). We find similarly low amounts of NO\(_2\) from trucks (3.5-12t and >12t). Finally, we show that NH\(_3\) emissions are most important for older generation catalyst-equipped petrol vehicles and SCR-equipped buses. The NH\(_3\) emissions from petrol cars have decreased by over a factor of three from the vehicles manufactured in the late 1990s compared with those manufactured in 2012. Tables of emission factors are presented for NO\(_x\), NO\(_2\) and NH\(_3\) together with uncertainties to assist the development of new emission inventories.

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