CONTENTS

TITLE
LIST OF ORIGINAL PUBLICATIONS
MAIN ARGUMENTS PROPOSED TO DEFENCE

1. INTRODUCTION
1.1. Nature of air ions
1.2. Characterization of air ions
1.3. The balance of ions in the atmosphere
1.4. Environmental importance of air ions
1.5. Earlier research
1.6. Main objectives of the present study

2. THE MEASURING STATION
2.1. Location
2.2. Meteorological characterization
2.3. Air pollution
2.3.1. Dependence of air pollution on wind direction
2.3.2. Summary of NO2 measurements
2.3.3. Characterization of air pollution by Sheftel method

3. INSTRUMENTATION AND DATA PROCESSING
3.1. General layout of the system
3.2. Air tract
3.3. Air ion spectrometers
3.4. Sensors
3.5. Electrical aerosol spectrometer
3.6. Estimation of the air ion fraction concentrations
3.7. Measurement accuracy

4. STATISTICAL CHARACTERIZATION OF AIR ION MOBILITY SPECTRUM
4.1. Average mobility spectrum of air ions
4.2. Variability of air ion spectra
4.3. Average characteristics and variability of small ions
4.4. Average characteristics and variability of intermediate ions
4.5. Average characteristics and variability of large ions

5. BURSTS OF INTERMEDIATE IONS

6. CLASSIFICATION OF AIR IONS AND CORRELATION BETWEEN THE CONCENTRATIONS OF MOBILITY CLASSES
6.1. Problem of the classification of air ions
6.2. Principal component and factor analysis of the set of fraction concentrations
6.3. Statistical classification of air ions
6.4. Correlation between the concentrations of air ion mobility classes

7. THE MEAN MOBILITY OF SMALL AIR IONS
7.1. Average characteristics
7.2. Time series of the mean mobility
7.3. The mean mobility and the evolution of small ion mobility spectra
7.4. Diurnal variation
7.5. Annual variation
7.6. Correlation of the mean mobility with meteorological parameters
7.7. Correlation of the mean mobility with the fraction concentrations of mobility spectra
7.8. The multiple regression analysis

8. ANNUAL VARIATIONS OF AIR ION MOBILITY CLASSES
8.1. Concentration of small air ions
8.2. Concentration of intermediate and light large air ions
8.3. Concentration of heavy large air ions

9. DIURNAL VARIATIONS OF AIR ION MOBILITY CLASSES
9.1. Concentration of small air ions
9.2. Concentration of intermediate ions
9.3. Concentration of light large ions
9.4. Concentration of heavy large air ions

10. CONTRIBUTION OF AIR ION MOBILITY CLASSES TO AIR CONDUCTIVITY

11. AIR ION MEASUREMENTS AS A SOURCE OF INFORMATION ABOUT ATMOSPHERIC AEROSOLS
11.1. Introduction
11.2. Measurements
11.3. Preliminary data analysis
11.4. Transformation of the spectra

12. CONCLUSIONS

REFERENCES

ABSTRACT, SUMMARY IN ESTONIAN, ACKNOWLEDGEMENTS, CV