Variation of the Distribution of Atmospheric n-Alkanes Emitted by Different Fuels’ Combustion

Sofia Caumo,Roy E Bruns,Pérola C Vasconcellos

doi:10.3390/atmos11060643

Sofia Caumo, Roy E Bruns + Show 1 more

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https://doi.org/10.3390/atmos11060643

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Abstract

This study presents the emission profiles of n-alkanes for different vehicular sources in two Brazilian cities. Atmospheric particulate matter was collected in São Paulo (Southeast) and in Salvador (Northeast) to determine n-alkanes. The sites were impacted by bus emissions and heavy and light-duty vehicles. The objective of the present study is to attempt to differentiate the profile of n-alkane emissions for particulate matter (PM) collected at different sites. PM concentrations ranged between 73 and 488 µg m−3, and the highest concentration corresponded to a tunnel for light and heavy duty vehicles. At sites where diesel-fueled vehicles are dominant, the n-alkanes show a unimodal distribution, which is different from the bimodal profile observed in the literature. Carbon preference index values corresponded to anthropogenic sources for most of the sites, as expected, but Cmax varied comparing to literature and a source signature was difficult to observe. The main sources to air pollution were indicated by principal component analysis (PCA). For PCA, a receptor model often used as an exploratory tool to identify the major sources of air pollutant emissions, the principal factors were attributed to mixed sources and to bus emissions. Chromatograms of four specific samples showed distinct profiles of unresolved complex mixtures (UCM), indicating different contributions of contamination from petroleum or fossil fuel residues, which are unable to resolve by gas chromatography. The UCM area seemed higher in samples collected at sites with the abundance of heavy vehicles.

Highlights

The Brazilian fleet corresponds to about 50 million vehicles [1] and, since 2003, a new generation of vehicles, known as flexible fuel vehicles, has been introduced in the country
The limits defined in the Brazilian Atmospheric Standards for total suspended particles (TSP) are related to 24 h of exposure, even with sampling time below 24 h, the average concentrations in both tunnels was higher than the limit of 240 μg m−3 established in Brazil
An intense traffic of heavy-duty vehicles (HDV) occurred in MMT during the afternoon and light-duty vehicles (LDV) circulation was constant during the morning and afternoon

Summary

Introduction

The Brazilian fleet corresponds to about 50 million vehicles [1] and, since 2003, a new generation of vehicles, known as flexible fuel vehicles, has been introduced in the country. Their flexible engines are adapted to use gasohol (gasoline with anhydrous ethanol) as well as pure ethanol [2]. The combustion of all these fuels leads to the rise of species in both gaseous and particulate phases in the atmosphere and their composition has not yet been elucidated in detail [3]. Among the compounds emitted by fossil fuel burning, the organic fraction is predominant, and organic pollutants as n-alkanes are often present [5,6]

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