Abstract
This paper analyses surface ozone measurements at five stations in an urban area (Valladolid) in the upper Spanish plateau over the period 2002–2020. Temporal evolutions, the relationship between ozone and other pollutants such as nitrogen oxides, and the assessment of the ozone concentration trend during the study period were analysed. Daily evolution of ozone at all the stations showed mean maximum concentrations in the afternoon, 15:00 GMT, with values ranging between 73.8 and 80.9 µg m−3, evidencing the influence of photochemical processes favoured by solar radiation in ozone formation. The lowest levels were recorded at night and in the early morning, 7:00 GMT, and were between 23.4 and 32.3 µg m−3, related with the reduction by NO reactions and deposition processes. A broad spring–summer peak between May and July was seen, with the highest values in the latter, with a mean value of up to 73.8 µg m−3. The variation in the monthly mean ozone concentrations of the different percentiles was analysed using a harmonic model. The empirical equation described the experimental values satisfactorily, with a confidence level of 95% and coefficients of determination above 80%, confirming the major decreasing trend in the ozone peak values over the study period.
Highlights
Tropospheric ozone (O3) is considered one of the main atmospheric pollutants due to its harmful effects on human health, agricultural crops, forests and materials [1,2,3]
The interquartile range was similar at all stations, about 48 μg m−3, with the lowest value notably being 44 μg m−3 at Michelín 2, due to the greater value of the lower quartile
Levels of its precursors and specific meteorological conditions were seen to influence the levels of ozone
Summary
Tropospheric ozone (O3) is considered one of the main atmospheric pollutants due to its harmful effects on human health, agricultural crops, forests and materials [1,2,3]. It has been considered of great importance in recent decades due to its impact on air quality at urban and regional scales as the main component of photochemical smog [4], and is of crucial importance for atmospheric chemistry and energy balance [5]. Ozone is a secondary pollutant formed by chemical reactions involving other species in the atmosphere (nitrogen oxides, carbon monoxide, methane, and volatile organic compounds) together with intense solar radiation and high temperatures. Local destruction or removal of ozone is caused by the titration reaction with NO and the deposition process to vegetation and other surfaces [7]
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