Atmospheric ethanol in London and the potential impacts of future fuel formulations

Abstract

There is growing global consumption of non-fossil fuels such as ethanol made from renewable biomass. Previous studies have shown that one of the main air quality disadvantages of using ethanol blended fuels is a significant increase in the production of acetaldehyde, an unregulated and toxic pollutant. Most studies on the impacts of ethanol blended gasoline have been carried out in the US and Brazil, with much less focus on the UK and Europe. We report time resolved measurements of ethanol in London during the winter and summer of 2012. In both seasons the mean mixing ratio of ethanol was around 5 ppb, with maximum values over 30 ppb, making ethanol currently the most abundant VOC in London air. We identify a road transport related source, with 'rush-hour' peaks observed. Ethanol is strongly correlated with other road transportrelated emissions, such as small aromatics and light alkanes, and has no relationship to summer biogenic emissions. To determine the impact of road transport-related ethanol emission on secondary species (i.e. acetaldehyde and ozone), we use both a chemically detailed box model (incorporating the Master Chemical Mechanism, MCM) and a global and nested regional scale chemical transport model (GEOS-Chem), on various processing time scales. Using the MCM model, only 16% of the measured acetaldehyde was formed from ethanol oxidation. However, the model significantly underpredicts the total levels of acetaldehyde, indicating a missing primary emission source, that appears to be traffic-related. Further support for a primary emission source comes from the regional scale model simulations, where the observed concentrations of ethanol and acetaldehyde can only be reconciled with the inclusion of large primary emissions. Although only constrained by one set of observations, the regional modelling suggests a European ethanol source similar in magnitude to that of ethane (∼60 Gg yr -1 ) and greater than that of acetaldehyde (∼10 Gg yr -1 ). The increased concentrations of ethanol and acetaldehyde from primary emissions impacts both radical and NO x cycling over Europe, resulting in significant regional impacts on NO y speciation and O 3 concentrations, with potential changes to human exposure to air pollutants.

Disentangling vehicular emission impact on urban air pollution using ethanol as a tracer

“…Urban measurements in Pittsburgh, in early 2000s, reported ethanol values ranging from 0.6 to 3.5 ppbv 25 , largely associated to industrial sources with a minor contribution of biogenic emissions 24 . More recently, in London, where gasoline currently contains 5% of ethanol (E5), ethanol has been reported as the most abundant Volatile Organic Compound (VOC), with an average mixing ratio of 5 ppbv 26 . Conversely, average ethanol concentration in 2010 in the Los Angeles Basin was reported at 9 ppbv, mostly associated to use as fuel additive (typically E10), a stark increase in concentration relative to few years prior 27 .…”

One decade of VOCs measurements in São Paulo megacity: Composition, variability, and emission evaluation in a biofuel usage context

“…The VOCs values observed in SPM were higher by a factor of 2 to 9 for aromatics, 1.8 to 5 for alkanes and 1.5 to 10 for alkenes. In spite of the high levels of ethanol also observed in Los Angeles and London (average of 5 ppb and 9±5 ppb, respectively, de Gouw et al, 2012;Dunmore et al, 2016), where ethanol is used as a fuel additive; acetaldehyde, formaldehyde and ethanol were greater in SPM by factors of 4 to 7.The increase of these compounds together with some alkenes in the emissions has been pointed out in previous studies as a result of ethanol combustion processes (Niven, 2005;Suarez-Bertoa et al, 2015a). Nevertheless, and despite the large biofuel use in SPM, there is not a clear enrichment for those compounds in São Paulo when compared to other locations.…”

Surface–atmosphere fluxes of volatile organic compounds in Beijing

“…Methanol and ethanol + formic acid together account for approximately one-third of the total oxygenated VOC mixing ratio. These compounds have been observed at high concentrations in many cities (Langford et al, 2009, Manchester, summer;Shao et al, 2009, Beijing, summer;Valach et al, 2015, London, August and September;Sahu and Saxena, 2015, Ahmedabad, winter), with ethanol reported to be the most abundant VOC in London with a mean mixing ratio of 5 ppbv in summer and winter (Dunmore et al, 2016).…”