Spark ignition vehicle contributions to atmospheric fine elemental carbon concentrations in coastal, rural and urban communities using polycyclic aromatic hydrocarbon tracers in the CMB model modified for reactivity

Abstract

Repartimos a parcela do componente de carbono elementar (CE) em PM 2,5 atmosférico atribuível à emissões de veículos com ignição por faísca (SI) em amostras coletadas durante dois anos em doze comunidades no Sul da Califórnia, incluindo zonas costeiras, rurais e urbanas usando o Modelo de Balanço de Massa Química (CMB8) modificado para levar em conta a reatividade dos hidrocarbonetos policíclicos aromáticos (HPAs). Foram avaliadas as razões HPA/CE em amostras coletadas no túnel Caldecott para utilização como assinaturas das fontes. A reatividade dos HPAs que ocorre durante o transporte de aerossóis atmosféricos que pode afetar as estimativas de contribuição das fontes (ECF) durante o verão/primavera/outono foi considerada com o uso de constantes de decaimento medidas experimentalmente. Nossos resultados mostram que o benzo [ghi] perylene e o indeno[1,2,3-cd]pireno podem ser utilizados com sucesso como marcadores específicos de CE nas emissões por veículos com SI. A estimativa média da porção de CE atribuído pelo modelo à emissões provenientes de SI nessas comunidades foi de 39, 58 e 62%, respectivamente, durante o verão, primavera/outono, e inverno. Para todas as comunidades costeiras, as atribuições a veículos por SI representam cerca do dobro das estimativas para as áreas rurais e urbanas, antes de dezembro 2003 quando MTBE ainda era usado na California.We apportioned the elemental carbon (EC) component of ambient PM 2.5 attributable to emissions from spark ignition (SI) vehicles in samples collected over a three-year period in twelve Southern California communities, including coastal, rural, and urban areas using the chemical mass balance model (CMB8) modified for polycyclic aromatic hydrocarbon (PAH) reactivity. Selected PAH/EC ratios, measured in samples collected in the Caldecott tunnel were evaluated for use as fingerprints. PAH reactivity which occurs during atmospheric transport and affects the source contribution estimates during the summer/fall/spring months was accounted for using experimentally measured decay constants. Results showed that benzo[ghi]perylene and indeno [1,2,3-cd]pyrene can be used successfully as specific tracers of EC contributions from SI vehicles. The average EC portion of PM 2.5 attributed by the model to SI emissions at these communities was 39, 58 and 62%, respectively, during the summer, spring/autumn, and winter. For all seasons, coastal community contributions represent about twice those found in the rural and urban inland communities, before December 2003 when MTBE was still in use in California.

Emissions from Ethanol-Gasoline Blends: A Single Particle Perspective

“…For example, the shift in PAH molecular weight distributions could potentially lead to high ethanol fuel exhaust being misidentified as diesel exhaust [24] and the change in both EC and OC fractions along with probable change in their thermal profile could change the results from techniques that rely on those markers [23]. Eiguren-Fernandez and Miguel [63] successfully used the ratio of specific PAHs to EC to identify spark ignition sources. We showed a significant shift in the molecular weight distribution of emitted PAHs with added ethanol.…”

Time-resolved characterization of particle associated polycyclic aromatic hydrocarbons using a newly-developed sequential spot sampler with automated extraction and analysis

“…Results are calculated using an effective-variance least squares method (EVLS), and requires of speciated profiles of potentially contributing sources and the corresponding ambient data from analyzed samples collected at a single receptor site. The model has been applied successfully for assessing contribution of sources to air concentrations of trace elements, elemental and organic carbon, and organics (Eiguren-Fernandez and Miguel, 2009; Kavouras and Zielinska, 2012; Larsen et al, 2012). …”