Open air mineral treatment operations and ambient air quality: assessment and source apportionment

Abstract

We present a methodology for evaluating and quantifying the impact of inhalable mineral dust resuspension close to a potentially important industrial point source, in this case an open air plant producing sand, flux and kaolin in the Capuchinos district of Alcañiz (Teruel, NE Spain). PM₁₀ levels at Capuchinos were initially high (42 μg m⁻³ as the annual average with 91 exceedances of the EU daily limit value during 2007) but subsequently decreased (26 μg m⁻³ with 16 exceedances in 2010) due to a reduced demand for minerals from the ceramic industry and construction sector during the first stages of the economic crisis. Back trajectory and local wind pattern analyses revealed only limited contribution from exotic PM sources such as African dust intrusions whereas there was clearly a strong link with the mineral stockpiles of the local industry. This link was reinforced by chemical and mineral speciation and source apportionment analysis which showed a dominance of mineral matter (sum of CO₃²⁻, SiO₂, Al₂O₃, Ca, Fe, K, Mg, P, and Ti: mostly aluminosilicates) which in 2007 contributed 76% of the PM₁₀ mass (44 μg m⁻³ on average). The contribution from Secondary Inorganic Aerosols (SIA, sum of SO₄²⁻, NO₃⁻ and NH₄⁺) reached 8.4 μg m⁻³, accounting for 14% of the PM₁₀ mass, similar to the amount of calcareous road dust estimated to be present (8 μg m⁻³; 13%). Organic matter and elemental carbon contributed 5.3 μg m⁻³ (9%) whereas marine aerosol (Na + Cl) levels were minor with an average concentration of 0.4 μg m⁻³ (1% of the PM₁₀ mass). Finally, chemical and mineralogical analysis of stockpile samples and comparison with filter samples confirmed the local industry to be the major source of ambient PM₁₀ in the area.