Abstract-Air pollution is one of the key problems in urban areas and its investigation is vital both for people's health but also for the environment as a whole. In particular, ozone is a secondary air pollutant with concentrations dependent mainly on changes in the levels of other pollutants and meteorological conditions within a given region. This paper presents a multivariate analysis of hourly data on 9 air pollutants and 6 meteorological variables in the town of Dimitrovgrad, Bulgaria over a period of 7 years and 3 months. Yeo-Johnson power transformation is applied to each air pollutant variable to improve normality and symmetry. The dominant patterns in the considered data are examined with the help of Principal Component Analysis (PCA) and factor analysis. Furthermore, particular focus is given to determining the concentration levels of ozone in relation to the other air pollutants and 6 meteorological parameters using multiple linear regression. The fitting of the obtained models with coefficients of determination R2 over 78% are obtained. The results are interpreted.
Index Terms-Air pollution modeling, factor analysis, multiple linear regression, ozone concentration, principal component analysis (PCA).
I. INTRODUCTIONThe monitoring, investigation and control of ambient air quality is a topical issue, very important for preserving the human health and the environment. Directives and regulatory restrictions are established in all European countries and worldwide for permissible concentrations of air pollutants [1]-[3]. In Bulgaria, 12 types of pollutants are systematically monitored by more than 36 automated stations run by the Executive Environment Agency which manages and coordinates activities related to the control and environmental protection of the country. The availability of a huge amount of collected data allows their statistical examination and makes it possible to find significant patterns, as well as dependencies within the data enabling the prediction of future states.In The objective of this paper is to investigate the relationships between large number of air pollutants in Dimitrovgrad, a town in Bulgaria, over an extended period of 7 years and 3 months. The specific goals of the study are: 1) Establishing the existence and determining the type of correlations between the investigated air pollutants; 2) Defining patterns and possible groups of pollutants which are closely related, and classifying the pollutants; 3) Obtaining multivariate regression models which describe the changes in ozone pollution levels in relation to the other pollutants and meteorological data.
II. MATERIALS AND METHODSWe examine air quality in the town of Dimitrovgrad, a typical urban region in South-central Bulgaria, 220 km away from the capital city of Sofia. The town is located in the Thracian valley on the banks of the Maritza river at an altitude of 125 m above sea level. It has about 40 000 inhabitants.The study was carried out based on hourly data about concentration of air pollutants between 1st January 2007...