Estimations of primary nitrogen dioxide exhaust emissions from chemiluminescence NOx measurements in a UK road tunnel

摘要

NO and NO_2 measurements have been made using the chemiluminescence method from 115 weekdays during the period 4th Jan-lOth Sep 2010 in a well characterised, unventilated tunnel on the Leeds Inner Ring Road. Measurements are made at two points in the tunnel and the difference in NO and NO_2 was attributed to emissions from vehicles in the tunnel. These data have been used to determine the fraction of NO_x (NO + NO_2) as primary NO_2 (f-NO_2) from vehicles using the tunnel. The average value of f-NO_2 from 7 am to 7 pm was 0.17_(-0.03)~(+0.01) in agreement with estimations from the UK National Atmospheric Emissions Inventory (NAEI). However, during the day there was a reproducible increase in f-NO_2 from approximately 0.10 at 7 am to 0.21 at 7 pm which is not reproduced with the current UK vehicle fleet emissions inventories. The increase in　f-NO_2 can be qualitatively linked to a decrease in the fraction of NOx arising from heavy goods vehicles and buses.