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Diffusive Sampling Of SO2 And NO2 Concentrations In Complex Terrain In Castile And Leon (Spain)


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M. A. García, M. L. Sánchez, O. Loukfaoui, M. J. López, B. de Torre, M. I. Ozores & I. A. Pérez


Diffusive sampling of SO2 and NO2 concentrations in complex terrain in Castile and Leon (Spain) M. A. Garcia, M. L. Sanchez, O. Loukfaoui, M. J. Lopez, B. de Torre, M. I. Ozores & I. A. Perez Department of Applied Physics, Valladolid University, Spain Abstract 92 radial diffusive samplers were used to measure sulphur dioxide and nitrogen dioxide concentrations in July 1999. They were distributed over a well-defined 56x56 km2 grid centred around a coal power station, covering a large stretch of the provinces of Palencia and Leon in the north of Spain. Both pollutants were quantitatively retained on cartridges coated with triethanolamine, and exposed over a period of 20 days. The trapped sulphur dioxide and nitrogen dioxide were analysed as sulphite, sulphate and nitrite by ion chromatography. In order to determine the precision and the exposure time, preliminary tests were performed. The results showed the great sensitivity of the method applied and concluded that two or three weeks were a suitable time to measure all kinds of air pollution scenarios within the area. The accuracy of the diffusive samplers was evaluated by comparison with the measurements obtained using continuous analysers. The inter-comparison yielded satisfactory results (r=0.81, for SO2 and NO2) showing a tendency to underestimate the nitrogen dioxide concentration. Spatial distribution of both pollutants across the selected grid was analysed and compared. The concentration levels of sulphur dioxide and nitrogen dioxide ranged between 3.0-39.0 and 11.2-27.7 pg/m3, respectively. In general, the results derived from the analysis of the concentration contours showed that the maximum concentrations of the pollutants were recorded in the prevailing wind sectors in the area and about 10 km downwind of the power station.