Seasonal evolution of suspended particles around a large coal-fired power station: Chemical characterization

The present work focuses on the seasonal evolution of total suspended particles (TSP) around the Teruel power station in Northeastern Spain. The results show a marked seasonal trend, along the sampling period (July 1995–July 1996), which is characterized by levels of the elements studied in TSP that were higher (up to one order of magnitude) in spring-summer and decreased progressively towards winter. This trend contrasts with the seasonal evolution reported by most of the studies carried out in industrial and urban areas in Central and Northern Europe. The origin of this seasonal TSP trend may be related to: (a) higher summer oxidation which increased levels of secondary TSP; (b) higher convective circulation in summer which raised levels of soil-related particles and primary anthropogenic particles; (c) higher frequency of intrusion episodes of Sahara air masses in summer and spring; and (d) lower aerosol scavenging potential in summer. A clear grain-size fractionation was observed for the different ions determined. SO42− and NH4+ were concentrated in the finest grain-size fraction (0.3−0.6 μm); NO3−, Cl−, K+, Mg2+, Na+ and minor amounts of NH4+ were concentrated in the 1.2−5.0 μm fractions; and Ca2+ increased with the particle diameter. S-bearing species were (NH4)2SO4 (mascagnite), (NH4)2Ca(SO4)2 • H2O (koktaite) and CaSO4 • 2H2O (gypsum). Mascagnite was the dominant species in the finest grain size fraction (0.3−0.6 μm), whereas koktaite was also present in the 0.6−1.2 μm fraction, and gypsum predominated in the other fractions