Development of an hourly bottom-up emission inventory to assess air pollution dispersion with GRAMM/GRAL in complex terrain

The detailed spatial and temporal emission inventory, prepared on an hourly basis and at a 250 × 250-meter grid, coupled with the local dispersion modeling system GRAMM/GRAL, helps to identify the impact of primary emission sources on air pollution. Our study was conducted in the complex subalpine city of Ljubljana. We prepared a detailed emission inventory for the most contributive sectors, which are industry, transport, small combustion, and agriculture for NOx, PM10, PM2.5, NMVOCs, and NH3 emissions in the year 2021. The total estimated annual emissions for Ljubljana were 1,935 tons of NOₓ, 393 tons of PM10, 315 tons of PM2.5, 1,847 tons of NMVOCs, and 168 tons of NH3. A comprehensive uncertainty analysis was conducted to assess the reliability of the emission inventory. Results from the GRAMM/GRAL dispersion model illustrate the spatial distribution of pollutants, which closely follows the geographical patterns of emission sources. Statistical comparison between modeled and observed concentrations indicates moderate agreement for PM10 and stronger agreement for NO2. Additionally, PMF analysis at the Vič monitoring station shows a consistent representation of primary emission sources compared with the model results. Overall, the results of this study improve understanding of atmospheric emission dynamics and provide a scientific basis for evidence-based decision-making aimed at reducing pollutant concentrations and protecting public health.