Question

The dominant source of pollution due to oxides of nitrogen (nox) in urban areas is

Answer 1

Nitrogen oxides are produced in combustion processes, partly from nitrogen compounds in the fuel, but mostly by direct combination of atmospheric oxygen and nitrogen in flames. Nitrogen oxides are produced naturally by lightning, and also, to a small extent, by microbial processes in soils.

Emission Sources and Trends

Man-made emissions of nitrogen oxides dominate total emissions in Europe, with the UK emitting about 2.2 million tonnes of NO2 each year. Of this, about one-quarter is from power stations, one-half from motor vehicles, and the rest from other industrial and domestic combustion processes. Unlike emissions of sulphur dioxide, emissions of nitrogen oxides are only falling slowly in the UK, as emission control strategies for stationary and mobile sources are offset by increasing numbers of road vehicles.

Emissions from electricity generation - NOx emissions from electricity generation are fairly constant from 1970 onwards until 1990. During the early 1990s the increased use of gas in electricity generation displaced coal and oil (DECC, 2009). The cleaner fuel and more modern power stations led to a significant reduction in NOx emissions from the sector until 2000. From 2000, the absolute level of gas used for electricity generation remained fairly constant, and increased demand was met by coal-fired power stations. Since 2006, coal use (and the total amount of fuel used in electricity generation) has substantially decreased (DECC, 2009).

NOx emissions from road transport - the road transport sector has provided a significant contribution to the downward trend in UK emissions. Emissions from road transport currently make the largest contribution to the UK total, accounting for some 33% in 2010 (Defra, 2011). The first petrol cars with three-way catalysts were introduced in 1992, and this resulted in a significant reduction in NOx emissions. Emission limits for diesel cars and light goods vehicles came into effect in 1993/94. Limits on emissions from heavy goods vehicles (HGVs) first came into effect in 1988 leading to a gradual reduction in emission rates as new HGVs penetrated the fleet. The introduction of these standards has had a substantial impact on NOx emissions from the road transport sector compared with the 1990s (RoTAP, 2012).

Answer 2

As we are becoming more modern and Industrial day by day,we are constantly polluting our mother nature.

In the present days the usage fuel driven vehicles and other equipments has been increased.

Combustion of these fuels generate various harmful gases like nitrogen oxides (nox).

These nitrogen oxides are occurring a devastating air pollution in the rural areas.