Composition of torched crude oil organic particulate emitted by refinery and its similarity to atmospheric aerosol in the surrounding area

The absolute contents and relative distributions of organic aerosols [n-alkanes, n-alkanoic and n-alkenoic acids, n-alkan-2-ones and polycyclic aromatic hydrocarbons (PAH)] were determined in torched gases emitted during the crude oil extraction and in the free atmosphere of the Hassi-Messaoud city (Algeria). Monocarboxylic acids, both saturated and monounsaturated (from 9802 to 20 057 ng m−3), accounted for the major fraction of the total particulate organic matter identified both in torch exhaust and atmospheric particulate. n-Alkanes were also abundant both in the direct emission (from 460 to 632 ng m−3) and city atmosphere (462 ng m−3) and displayed a peculiar fingerprint characterised by the presence of a set of branched congeners around even carbon-numbered homologues and a strong even-to-odd predominance along the whole carbon number range (C16–C34). Whilst n-alkan-2-ones were absent in the city and poor in smokes emitted from the torches (from 31 to 42 ng m−3), PAH were present at low extents in all sites (from 18 to 65 ng m−3). The incomplete thermal combustion of torched crude oil was very likely the main source of these particle-bound organic constituents in the city and its surrounding region.