Climate and Air Pollution Monitoring in Two Forest Ecosystems in Bulgaria

The relationship between month and daily mean concentrations of ozone and NOx were established. Month values of ozone dose (AOT40 values) for the vegetation period as well as the short-term ozone episodes and some climatic factors (air temperature and humidity, global radiation) and NOx concentrations is established with direct reference to ICP-forest data. The monitoring of air pollution is carried out in two forest ecosystems: Vitinia and Jundola. The values of the correlation coefficients in Pearson correlation matrixes are used as the basis of an estimation of the variability in these relations. There was not clear trend between month mean ozone concentrations and global radiation. The coefficient values for the air temperature increased along with the month means of these parameters. Daily means of the temperature and NOx concentrations are in a good correlation with the short-term ozone means during the summer months. The tendencies established are explained in relation to climate peculiarities in two forest ecosystems during the different parts of the vegetation season. Introduction The ground level ozone is responsible for a variety of adverse effects on both human being and plant life (Lu et al. 2002). Many studies suggest that ozone have a major role in some types of forest decline (Karlson et al. 2005). Deciduous species appeared to be more sensitive to ozone exposure while conifers are more sensitive to the concentrations of SO2 and NO2 (Ozolincius et al., 2005). To protect the forest trees from such adverse effects, early information and precautions about the high ozone level need to be ascertained (Lu et al., 2002). There remains a great need for information about NOx and stratospheric ozone Ground level ozone is formed in the atmosphere by the reactions of volatile organic compounds and nitrogen oxides in the presence of heat and sunlight. Increased anthropogenic emissions are likely to raise the background level of ozone. The photochemical formation of tropospheric ozone from increased concentrations of methane and nitric oxides may also lead to a higher ozone level on a global scale. A significant increase in the background concentration of ozone has been observed at several sites in Europe although the underlying causes are not settled (Solberg, 2005). Measurements and modelling results indicate that there is a strong link between climate and seasonal factors and surface ozone (Balls et al.1995; Benton et al. 1996; Grünhage and Jäger1994, Grendfelt, 1996). Ozone is formed during all the year but most readily during hot summer weather (Lelieveld et al., 2002). Ozone turned to be the most important air pollutant in both relatively clear and urban areas in Bulgaria (Tzvetkova and Doncheva 2001). However data for annual pattern of distribution of the elevated ozone values especially in forest stands in Bulgaria are scarce. This paper reports the average month values for ozone and nitrogen oxide concentrations along with some climatic factors during the vegetation period of 2001. The data used for the estimation are received on the basis of continuous pollution and climate monitoring in two typical for Bulgaria forest ecosystems. The study aims to investigate the importance of meteorological factors and their impact on relevant pollutant concentration levels. Rough estimation was made of the effect of some potential ozone sources at the experimental stations. Acknowledgment: This investigation was carried out with the technical equipment and financial support of the Swiss Government as a part of Bulgarian-Swiss cooperative project “Monitoring of the forest ecosystems”.