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A physicochemical characterisation of airborne particulate matter (PM) was performed in a region affected by the emissions from a source of precursors of secondary inorganic aerosols (SIA, 1050 MW power plant). This characterisation sought to study the interferences of other possible natural and anthropogenic sources when monitoring PM 10, PM2.5 and PM I around this emission source. The study was performed in the semi-arid Ebro basin and Catalan and Iberian ranges (Eastern Spain) and consisted in (1) monitoring the transport and impacts on the ground of the SO2 plume (fumigation), (2) chemically characterising (25 PM components) of TSP-size fractions, and diurnal and nocturnal PM10 and PM2.5 samples, and (3) in measuring the PM mass size distribution. This PM characterisation was undertaken in ambient air, during fumigations of the SO2 plume on the ground and around other local PM sources. PM1 was found to be the best parameter for monitoring PM pollution derived from the SO2 emissions owing to the formation of ammonium-sulphate in the finest PM fractions. Three PM I & PM2.5 events were recorded during the field measurement campaign: two events were caused by ammonium-sulphate episodes, the third was due to an African dust outbreak. PM-mass size distribution and the high correlation of PM I with SO2 during the SO2 fumigation events suggest that a significant fraction of sulphate is formed by means of ’new particle formation’ processes (nucleation). PM 10 presents a much higher variability (noise) than PM I & PM2.5 owing to the re-suspension of coarse (2.5-10 mum) mineral dust particles. The PM1 load in PM10 undergoes significant variations: 60-80% during plume fumigations, 20-60% in ambient air, and down to 10% in areas affected by mineral dust re-suspension. The daily cycles observed in some PM components (sulphate, nitrate and mineral dust elements) and the chemical features of PM are also described in detail. (C) 2004 Elsevier Ltd. All rights reserved.