Emissions compliance proves a major challenge for the UK

摘要

Efforts to reduce emissions from vehicle exhausts is proving to be a tough ask as the UK struggles to meet European directives on air quality, says Dr Glyn Rhys-Tyler. Greater attention has been placed on the environmental impact of transport in recent years and the fact that poor air quality has a significant negative impact on human health. The two main air pollutants of current concern from road transport in the UK are nitrogen oxides (NO_x) and particulate matter. This article focuses on NO_x from vehicle exhausts. NO_x from vehicle exhausts primarily comprises two components: nitric oxide (NO) and nitrogen dioxide (NO_2). From a health perspective NO_2 is of most concern. However NO readily converts to NO_2 in the atmosphere, so to reduce ambient concentrations of NO_2 it is necessary to control emissions of total NO_x. Road transport is responsible for about 46% of total NO_x emissions in England. However in locations with poor air quality, for example some parts of the highway network, the relative contribution of road transport to the NO_2 air quality problem can be up to 80%. NO and NO_2 emissions are particularly associated with diesel engines.