OC/EC ratio observations in Europe: Re-thinking the approach for apportionment between primary and secondary organic carbon

Abstract

This study explores a large set of OC and EC measurements in PM(10) and PM(2.5) aerosol samples, undertaken with a long term constant analytical methodology, to evaluate the capability of the OC/EC minimum ratio to represent the ratio between the OC and EC aerosol components resulting from fossil fuel combustion (OC(ff)/EC(ff)). The data set covers a wide geographical area in Europe, but with a particular focus upon Portugal, Spain and the United Kingdom, and includes a great variety of sites: urban (background, kerbside and tunnel), industrial, rural and remote. The highest minimum ratios were found in samples from remote and rural sites. Urban background sites have shown spatially and temporally consistent minimum ratios, of around 1.0 for PM(10) and 0.7 for PM(2.5).The consistency of results has suggested that the method could be used as a tool to derive the ratio between OC and EC from fossil fuel combustion and consequently to differentiate OC from primary and secondary sources. To explore this capability, OC and EC measurements were performed in a busy roadway tunnel in central Lisbon. The OC/EC ratio, which reflected the composition of vehicle combustion emissions, was in the range of 03-0.4. Ratios of OC/EC in roadside increment air (roadside minus urban background) in Birmingham, UK also lie within the range 03-0.4. Additional measurements were performed under heavy traffic conditions at two double kerbside sites located in the centre of Lisbon and Madrid. The OC/EC minimum ratios observed at both sites were found to be between those of the tunnel and those of urban background air, suggesting that minimum values commonly obtained for this parameter in open urban atmospheres over-predict the direct emissions of OC(ff) from road transport. Possible reasons for this discrepancy are explored. (C)

Chemical Compositions of PM2.5 at Two Non-Urban Sites from the Polluted Region in Europe

“…The finding is agreed with similar studies (Plaza et al, 2011;Pio et al, 2011;Zhang et al, 2014) and indicates that biological matter and secondary organic aerosol (SOA) could have been important OC sources in Racibórz and Złoty Potok. There was also a seasonal variation for the EC/PM 2.5 ratio.…”

Wet deposition of fossil and non-fossil derived particulate carbon: Insights from radiocarbon measurement

“…This 268 finding agrees with the fact that OC/EC emissions ratios are higher in biogenic or biomass 269 burning sources than those in fossil fuel emissions (i.e. mainly vehicular emissions in 270 Europe) (Pio et al, 2011). A notable seasonality was not found for relative fossil and non-271 fossil contributions to OC, whereas non-fossil EC fraction was slightly higher in winter 272 than other seasons due to larger wood burning emission for heating during cold period 273 (Zhang et al, 2013; Zotter et al, 2014a).…”

Characteristics of Organic Carbon and Elemental Carbon in the Ambient Air of Coking Plant

“…In contrast to the OC/EC ratios from these pollution sources and considering that the sampling sites were close to the coke oven, the primary source of OC and EC in the coking plant was the coking process. Table 2 compares the OC and EC concentrations and the OC/EC ratio in the ambient air of the coking plant with those reported in previous studies (Handler et al, 2008;Pio et al, 2011;Ducret-Stich et al, 2013;Alves et al, 2015). OC/EC ratios of 1.29, 1.67, 1.09, and 1.8 were reported for the ambient air of coking plant, highway, urban roadway tunnel, and industry.…”

“…These ratios all being lower than 2 suggest that the OC and EC pollutions near these sources mainly originated from primary emission (Turpin and Huntzicker, 1995;Chow et al, 1996). OC and EC concentrations were 2.76 and 1.65 µg/m 3 in the highway atmosphere, 29.6 and 27.1 µg/m 3 in the atmosphere of the urban roadway tunnel, and 6.0 and 3.9 µg/m 3 in the industrial air (Pio et al, 2011;Ducret-Stich et al, 2013;Alves et al, 2015). The OC concentration in the coking plant area was 169.6 µg/m 3 , which is 61.4 times that of the highway atmosphere, 5.7 times that of the urban roadway tunnel air, and 28.3 times of the industrial air.…”