Determination of size-segregated polycyclic aromatic hydrocarbon and its nitro and alkyl analogs in emissions from diesel-biodiesel blends

There have been several works on criteria emissions from biofuels and their mixtures. In this study, the focus is on emissions of non-criteria pollutants, in particular polycyclic aromatic hydrocarbons (PAHs) and their nitrated (nitro-PAHs) and alkylated analogs (alkyl-PAHs). The determinations were made using a standard engine from the fleet of vans used in Brazilian towns and cities operating at 700, 1200 and 1500 rpm and with pure commercial diesel and mixtures of 7, 10, 15 and 20% biodiesel. Sampling was performed with a 10-stage cascade impactor and the selected items were grouped into coarse, fine, ultrafine and nano particles. Chemical analyses were conducted using gas phase chromatography - mass spectrometry (GC MS) detection with large volume injection. The results show that emissions from all PAHs increase with engine speed by 18.1% from 700 to 1200 rpm and by 88.7% from 700 to 1500 rpm. It was observed that there was a reduction of total PAHs from 700 to 1500 rpm when there was an increase in biodiesel content. However, this has the undesirable effect of increasing the nitro-PAHs when there is a greater amount of biodiesel in the mixture, which may be because the rise in NO,, emissions can cause a reaction with PAHs. High correlations were observed between the emissions of PAHs and alkyl-PAHs (0.90) and between PAHs and nitro-PAHs (0.67) which suggests the formation mechanisms of these compounds might be similar.

Automated summary

This study focuses on the emissions of non-criteria pollutants, including PAHs and their nitro-PAHs and alkyl-PAHs, from biofuels and their mixtures. Results show that emissions of all PAHs increase with engine speed, but there is a reduction in total PAHs with an increase in biodiesel content, although this can lead to an increase in nitro-PAHs. High correlations were observed between PAHs and alkyl-PAHs, and between PAHs and nitro-PAHs, suggesting similar formation mechanisms for these compounds.