Remote sensing of NO2 exhaust emissions from road vehicles(93 page pdf, David Carslaw and Glyn Rhys-Tyler, DEFRA Project Reference:332c2011 (City of London Corporation) , 334c2011 (London Borough of Ealing) , May 2013)
Today we review research on measuring NO2 emissions from EU standard and diesel vehicles using remote sensors on roadways in London. Results show that while NO2 concentrations have slowly decreased over the last decade due to more stringent EU standards, there has not been a similar improvement in diesel vehicles. For the latter, care must be taken in reducing NO2 that increases in Particulate Matter (PM) are avoided.
Key Quotes:
“Directly emitted NO2 from vehicles behaves like a primary pollutant close to roads and can make a significant contribution to near-road NO2 exceedances of both the annual and hourly mean EU Limit Values.“
“Co-linear beams of infrared (IR) and UV light are passed across the roadway into the IR detection unit, and are then focused onto a dichroic beam splitter, which serves to separate the beams into their IR and UV components. The IR light is then passed onto a spinning polygon mirror, which spreads the light across the four infrared detectors: CO, CO2, HC and reference.”
“Whilst it is possible to analyse trends in NOx and NO2 emission rates using aggregated data from monitoring sites across the LAQN, this roadside sensing technique has the advantage of being able to quantify the variation in NOx and NO2 emissions across the urban road vehicle fleet by vehicle type (e.g. car, LGV, HGV, bus, taxi), fuel type, Euro standard, engine size and vehicle age.”
“For passenger cars, emissions of NOx for Euro 5 diesel cars are at an equivalent level to pre-Euro vehicles (i.e. pre 1992 vehicles). Emissions peaked for Euro 2/3 cars but are only about 25% less for Euro 5 cars. “
“diesel cars >2.0l accounted for 36% of total diesel passenger cars measured.”
“For diesel cars it has been shown that total NOx emissions, whilst peaking for vehicles manufactured around year 2000, have changed little overall over the past 20 years and in that time new after-treatment technologies have increased the proportion of NOx that is NO2 “
“A brief analysis of ambient trends of NOx and NO2 at 23 roadside and kerbside sites in London over the past 10 years shows that NOx and NO2 concentrations have only decreased by about 1 and 0.5% on average per year, respectively “
“only measuring NO and making assumptions about the level of NO2 for modern vehicle technologies could be unreliable and potentially misleading. “
Related articles
No comments:
Post a Comment