Size distribution and chemical composition of metalliferous stack emissions in the San Roque petroleum refinery complex, southern Spain

We demonstrate that there is great variation in the size range and chemical composition of metalliferous particulate matter (PM) present within petrochemical complex chimney stacks. Cascade impactor PM samples from seven size ranges (17, 14, 5, 2.5, 1.3, 0.67, and 0.33 μm) were collected from inside stacks within the San Roque complex which includes the largest oil refinery in Spain. SEM analysis demonstrates the PM to be mostly carbonaceous and aluminous fly ash and abundant fine metalliferous particles. The metals with the most extreme concentrations averaged over all size ranges were Ni (up to 3295 μg m−3), Cr (962 μg m−3), V (638 μg m−3), Zn (225 μg m−3), Mo (91 μg m−3), La (865 μg m−3), and Co (94 μg m−3). Most metal PM are strongly concentrated into the finest fraction (<0.33 μm), although emissions from some processes, such as purified terephthallic acid (PTA) production, show coarser size ranges. The fluid catalytic cracking stack shows high concentrations of La (>200 μg m−3 in PM0.67-1.3), Cr and Ni in a relatively coarse PM size range (0.7-14 μm). Our unique database, directly sampled from chimney stacks, confirms that oil refinery complexes such as San Roque are a potent source of a variety of fine, deeply inhalable metalliferous atmospheric PM emissions.