BACKGROUND CONCENTRATION OF AIR POLLUTANTS FOR SOFIA CITY � ANALYSIS FOR SUMMER AND WINTER MONTHS

Abstract

The air pollution in many Bulgarian cities is of concern mainly due to high concentration of particulate matter (PM). Poor air quality has adverse health effects and is responsible for premature deaths and life loss. According to the World Health Organization air pollution remains the single largest environmental health risk in Europe. Additionally, negative effects of urban air pollution can be detected on buildings, cultural heritage, vegetation, biodiversity, etc. Air pollutant concentrations in the city depend on processes occurring on different temporal and spatial scale and reflect contribution from distant and local emission sources. At a single point in the city the pollutants concentrations can be regarded as superposition of natural background values, regional background and city increment contribution consisting of urban background and street level values. Background values are critical components of the total air quality concentrations and their estimation is important for defining appropriate abatement measures at national, regional and local level. The objective of this work is to present and discuss background concentrations of key pollutants (PM, NO2, SO2 and ozone) for the city of Sofia for one summer and one winter month of 2021. These concentrations are estimated by the Bulgarian Chemical Weather Forecasting System (BgCWFS) [1-3], based on WRF-CMAQ models. The results analysed are for domain Sofia (30 x 27 grid points) with 1 km resolution. The concentrations for this domain can be considered as regional background for the city of Sofia. We discuss the spatial monthly distributions of the key pollutants and the variability across the city and present domain mean concentrations for the two months. The relationship to some meteorological variables (wind speed, temperature, mixing height) is also discussed.