Influence of air pollution to incident photosynthetically active radiation during clear sky conditions in Ostrava, Czech Republic

Abstract This research paper focuses on with the effects of air pollutants PM10, NOx, and SO2 on the blue (400–510 nm), green (510–600 nm), and red (600–700 nm) spectral regions of photosynthetically active radiation (PAR). The measurements of solar radiation incident on a horizontal surface were taken at two locations in the city of Ostrava (Czech Republic) that differed in the source of air pollution. Linear regression models, with two explanatory variables (solar elevation angle and logarithm of individual pollutant concentration), were used as statistical tools for revealing the effect of air pollutants on incident solar radiation. The effect of air pollution on the Blue/PAR spectral ratio was ambiguous. There was a significant decrease in the Green/PAR spectral ratio, whereas there was a significant enhancement in the Red/PAR spectral ratio caused by the increasing air pollutant concentrations. The effects of air pollutants on these spectral ratios were significant from a statistical point of view with p-values smaller than 0.05, but the magnitude of the effect that the air pollutants had on the Blue/PAR and Red/PAR was small. In comparison to the above mentioned, the pollutants had a dominating effect on the Green/PAR spectral ratio. Pollution did not induce homogenous reduction of all PAR spectral regions, instead each pollutant had a specific effect on the contributions of blue, green, and red spectral regions to PAR irradiance. Possible causes of these effects are discussed.