Tropospheric Ozone Concentrations - Seasonal and Daily Analysis and its Association with NO and NO 2 as a Function of NO x in Ciuc Depression - Romania
This paper summarizes the results of a yearlong continuous measurements of gaseous pollutants, NO, NO 2 , NO x and O 3 in the ambient air of Ciuc Depression. Measured concentration of the pollutants in study area is a function of time. NO, NO 2 and O 3 peak occurred in succession in presence of sunlight. At the time of maximum O 3 concentration most of the NO x are utilized. The diurnal cycle of ground level ozone concentrations, revealed mid-day peak with lower nocturnal concentrations and inverse relationship exists between O 3 and NO x , which are evidences of photochemical O 3 formation. Particular emphasis is placed on establishing how the level of “oxidant”, OX (taken to be the sum of O 3 and NO 2 ) varies with the level of NO x , and therefore to gain some insight into the atmospheric sources of OX. The analyses indicate that the level of OX at a given location is made up of NO x – independent and NO x – dependent contributions. The former is effectively a regional contribution which equates to the regional background O 3 level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. Increased values can be also observed for more periods of the year; this fact for the depressional case of Ciuc are due to the particular case represent by stable boundary layer conditions (high static stability conditions in term of Brunt - Vaisala frequency) which are long known for causing increasing concentration of pollutant concentrations.