We interpret here the variability of levels of carbonaceous aerosols based on a 12-yr database from 78 monitoring stations across Spain especially compiled for this article. Data did not evidence any spatial trends of carbonaceous aerosols across the country. Conversely, results show marked differences in average concentrations from the cleanest, most remote sites (around 1 μg m⁻³ of non-mineral carbon (nmC), mostly made of organic carbon (OC), with very little elemental carbon (EC) 0.1 μg m⁻³; OC/EC = 12–15), to the highly polluted major cities (8–10 μg m⁻³ of nmC; 3–4 μg m⁻³ of EC; 4–5 μg m⁻³ of OC; OC/EC = 1–2). Thus, urban (and very specific industrial) pollution was found to markedly increase levels of carbonaceous aerosols in Spain, with much lower impact of biomass burning.

Correlations between yearly averaged OC/EC and EC concentrations adjust very well to a potential equation (OC/EC = 3.37 EC^−0.67 R² = 0.94). A similar equation is obtained when including average concentrations obtained at other European sites (y = 3.61x^−0.5, R² = 0.78).

A clear seasonal variability in OC and EC concentrations was detected. Both OC and EC concentrations were higher during winter at the traffic and urban sites, but OC increased during the warmer months at the rural sites. Hourly equivalent black carbon (EBC) concentrations at urban sites accurately depict road traffic contributions, varying with distance to road, traffic volume and density, mixing layer height and wind speed. Weekday urban rush-hour EBC peaks are mimicked by concentrations of primary gaseous emissions from road traffic, whereas a single midday peak is characteristic of remote and rural sites. Decreasing annual trends for carbonaceous aerosols were observed between 1999 and 2011 at a large number of stations, probably reflecting the impact of the EURO4 and EURO5 standards in reducing the diesel PM emissions. This has resulted in some cases in an increasing trend of NO₂/OC+EC ratios, because these standards have been much less effective for the abatement of NO_x exhaust emissions in passenger diesel cars. This study concludes that EC, EBC, and especially nmC and OC+EC are very good candidates for new air quality standards since they cover both emission impact and health related issues

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Tar residues (“tarballs”) occur frequently on the SE coast of the Paria Peninsula, NE Venezuela. This paper reports on tarballs recovered from approximately 14 km of shoreline during monthly sampling over a two‐year period ending in April, 2011. The tarballs were analysed geochemically and results show that more than 70% of them could be included within a single compositional group on the basis of their physical and organoleptic properties. The tarballs were fingerprinted using biomarkers (hopanes, steranes, alkanes, aromatic steroids, phenanthrenes and dibenzothiophenes) by gas chromatography and gas chromatography – mass spectrometry. Sulphur and trace element contents were also determined. These analyses indicate that the tarballs do not have an anthropogenic origin, but that they probably originated from petroleum generated by argillaceous limestones in the Turonian – Campanian Naparima Hill Formation. This formation includes marls and organic‐rich shales and limestones, and is an important source rock at oilfields in Trinidad and the southern Gulf of Paria. In the southern part of the Gulf, petroleum escapes from Neogene reservoirs to the seafloor via natural seepages associated with the Los Bajos and other fault systems. It is inferred that the petroleum is then transported by wind and tidal currents to the coast of the SE Paria Peninsula where it strands as tarballs. The geochemistry of the tarballs collected is discussed to investigate their source.

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