Ambient concentrations of 1,3-butadiene in the UK

This paper assesses the current knowledge of 1,3-butadiene as an atmospheri c pollutant, considers measurement techniques and reviews available data on 1.3-butadiene monitoring and emissions estimates. Atmospheric chemistry, s ources of emission, current legislation, measurement techniques and monitor ing programmes for 1,3-butadiene are reviewed. There have been comparativel y few studies of the products of oxidation of 1,3-butadiene in the atmosphe re. However, on the basis of the available information, and by analogy with the oxidation mechanism for the widely-studied and structurally similar na tural hydrocarbon isoprene (2-methyl-1,3-butadiene), it is possible to defi ne some features of the likely oxidation pathways for 1,3-butadiene. The to tal UK 1,3-butadiene emission to the atmosphere for 1996 has been estimated at 10.60 kTonnes. 1,3-Butadiene is a product of petrol and diesel combusti on; consequently this total is dominated by road transport exhaust emission s (accounting for some 68% of the total). Off-road vehicles and machinery a re responsible for 14% of the total UK emission. 1,3-Butadiene is used in t he manufacture of numerous rubber compounds, and consequently emissions ari se from both the manufacture and use of 1,3-butadiene in industrial process es. Emissions from the chemical industry account for 18% of the UK total em ission-8% from 1,3-butadiene manufacture and 10% from 1,3-butadiene use. Th e United Kingdom Expert Panel on Air Quality Standards (EPAQS) has publishe d a report on 1,3-butadiene, and recommended a national air quality standar d of 1.0 ppb (expressed as an annual rolling mean). This was adopted by the Government as part of the National Air Quality Strategy (NAQS) in 1997, an d a target of compliance by 2005 was set. Work conducted for the review of the NAQS (1999) indicated that it was likely that all locations would be co mpliant with the national standard by the end of 2003. As a result, the rev iew updated the air quality objective for 1,3-butadiene, with the deadline for compliance being brought forward to 31/12/2003. The UK Hydrocarbon Moni toring Network provides continuous hourly measurements of 1,3-butadiene at 13 sites. and has been operational since 1993. The dataset that is availabl e allows spatial and temporal trends to be evaluated, and has proved to be invaluable in characterising the current ambient levels of 1,3-butadiene in the UK. Hourly maximum concentrations of 1,3-butadiene of up to 10 ppb (1 ppb = 1 ppb, i.e. 1 vol. of 1,3-butadiene in 1000 000 000 vol. of air. 1 pp b of 1,3-butadiene is ca. equal to 2.25 mug m(-3) at 20 degreesC) may be me asured for several hours at the sites. Monthly mean concentrations are typi cally 0.1-0.4 ppbv. At most sites, these levels are driven by emissions fro m motor vehicles. Occasionally emissions of 1,3-butadiene from industrial s ources may elevate 1,3-butadiene concentrations to several tens of ppb. Tre nd analysis of the data suggests that ambient concentrations of 1,3-butadie ne in the UK are declining at about 10% per year. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.