Twenty years of continuous high time resolution volatile organic compound monitoring in the United Kingdom from 1993 to 2012

Continuous, high frequency observations of C-2 - C-8 hydrocarbons began in the United Kingdom in 1993 and have continued through to the present day at a range of kerbside, urban background and rural locations. Most of the monitored hydrocarbons have shown dramatic declines in concentrations over the study period, with present levels close to an order of magnitude below their levels in the 1990s. The concentrations of 23 selected hydrocarbons have been aggregated up to give an estimate of the total VOC concentrations. These annual values have shown an exponential decline of -18% yr(-1) at the London Marylebone Road kerbside site, -11 % yr(-1) at the London Eltham urban background site and -22% yr(-1) at the rural Harwell site. Similar declines have been reported in UK road transport VOC emissions, demonstrating how the VOC emission inventories have apparently captured the salient features influencing real-world VOC emissions over the 1994-2012 period. (C) 2014 Elsevier Ltd. All rights reserved.